CHAPTER IV
Filariasis
Joseph M. Hayman, Jr., M.D.
Filariasis became a problem of importance in American orother military forces for the first time in history during World War II. Infact, the epidemic occurrence of the disease in the American military forcesapparently represents the first such to be reported in medical literature,although, of course, its endemic presence in certain areas was well known. Therewere two principal reasons for these epidemics and for the importance which theyassumed in the military and the logistic planning. These were the assignment ofpreviously unexposed troops to endemic areas without adequate protection and theignorance of the majority of medical officers of the early symptoms, thediagnosis, and the course of the disease.
HISTORICAL NOTE
Filariasis, contrary to common opinion, has not been unknownin the United States. The first demonstrated cases of filariasis indigenous inthe United States were reported by John Guit?ras in 1886.1 Though sporadiccases were reported from time to time from Florida, Alabama, and Virginia, theregion around Charleston, S.C., was the only known focus of any consequence inthe United States. In 1915, Johnson reported finding microfilariae in 19 percentof 400 hospital admissions within a year.2 By 1940, however,filariasis indigenous in the United States had practically disappeared, evenfrom Charleston. This disease was probably brought to the West Indies and theAmericas with the importation of African slaves.3 The absence of the diseaseon the Pacific coast, even in tropical America, in contrast to its widegeographic range on the Atlantic coast, supports this view, as does the factthat there is no mention of so striking a condition as elephantiasis in theearly accounts of the Barbados where later it was so common that it was known as"Barbados leg." The vast majority of medical officers had no knowledgeof the early symptoms or manifestationsof filariasis, and their only concept of the infection was that ofincapacitating elephantiasis, relatively rare even in endemic foci. The symptomsand course of filariasis in an endemic area, where exposure begins in childhood,are very different
1Guit?ras, J.: The FilariaSanguinis-Hominis in the United States. M. News (Philadelphia) 48: 399, 1886.
2Johnson, F. B.: Filarial Infection.South. M.J. 8: 630, 1915.
3Smith, A. J.: Filariasis in the Americas. In Proceedingsof Second Pan American Scientific Congress, 1917, vol. 9, sec. 8, pt. 1, pp. 49-76.
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from the manifestations of early infection in previouslynonexposed adults. Medical literature contains only meager descriptions of thelatter, and American medical officers had practically no knowledge of thisaspect of the disease.
DEFINITION
Filariasis is the term applied to infection of man andanimals by certain nematodes (round worms) of the superfamily Filarioidea. Onlyone genus, Wuchereria, was of any military importance. This genuscontains two closely related species, Wuchereria bancrofti and Wuchereriamalayi. The latter is endemic in Malaya and is present in many of theislands in the Far East, as well as in parts of China and India. Few infectionswith this parasite were recognized in troops. Wuchereria malayi has thesame life history as W. bancroftibut is believed to produce milder symptoms and not to lead to thedevelopment of elephantiasis. It will not be considered separately from W.bancrofti in this chapter.
CAUSATIVE AGENT
The adult W. bancrofti are white hairlike translucentworms measuring from 25 to 100 mm. in length and about 0.01 mm. in breadth.Adult male and female worms live coiled together in the dilated lymphatics,mainly in those of the pelvic region. Occasionally, adult worms, includinggravid females, are found in peripheral lymphatics and lymph nodes. The gravidfemale discharges sheathed embryos, periodically, which reach the bloodstreamand circulate there. There is no evidence that the embryos themselves produceany symptoms. These microfilarial embryos measure about 360 by 7 microns,including sheath. The microfilariae do not develop further nor multiply in thebloodstream. Further development occurs only in the intermediate host, themosquito. When a suitable mosquito feeds on a person with microfilariae in theperipheral blood, the embryos are taken in and enter the stomach. Here, theembryos escape from their sheaths and enter the thoracic muscles of themosquito. In the thoracic muscles, fuller development, including one or moremolts, takes place. After 10 or more days, the infective microfilariae orfilariform larvae, now measuring from 1.5 to 2 mm. in length, migrate to theproboscis. When the mosquito next feeds on a person, the larvae escape and enterthrough the puncture wound made by the mosquito, or through abrasions in theskin, and find their way into the peripheral lymphatics and thence into thesystemic circulation. It should be noted that there is no multiplication of thelarvae in the insect; the larvae taken in at the time of feeding simply grow andmature into the infective stage. The time from the entry of the mature larvae tothe appear-
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ance of microfilariae in the blood of the host is usuallystated to be about 1 year.
In most endemic areas, the microfilariae exhibit a nocturnalperiodicity; that is, they are present in the peripheral blood in much greaternumbers during the night than during the day, reaching a maximum between 2100and 0200 hours. This is not true of filariasis in Samoa, Fiji, and some otherPacific islands. The reasons for this nocturnal periodicity are not known.
GEOGRAPHIC DISTRIBUTION
Filariasis is endemic throughout most of the moist and warmregions of the world between latitudes 30? N. and 32? S. In Europe, it isapparently confined to Spain (Barcelona), Hungary, and Turkey. It is presentalong the southern shore of the Mediterranean and is common throughout the wholecentral tropical belt of Africa. In the Far East, it extends along the coast ofIndia, through Malaya, French Indochina, southern China, Korea and Japan, thePhilippines, and Borneo. It is sparsely present in northern Australia. In thewestern world, it is common along the eastern coast of Central and South Americafrom about central Mexico to Argentina, although it has not been reported fromthe west coast. It is common in the Greater and Lesser Antilles. It was formerlypresent in the neighborhood of Charleston (p. 123). It is endemic in thepopulation of all major island groups in the Pacific Ocean from a latitude whichwould bisect the islands of Japan to one that would cross Australia just southof Brisbane, with the exception of New Zealand and the Hawaiian Islands.Throughout this filarial belt, the prevalence of the disease is spotty, largevariations in incidence often being noted in adjacent villages, and is relatedto the flight range of the local vector.
TRANSMISSION
Epidemic filariasis occurred only in troops in the South andCentral Pacific Islands where microfilariae among the natives were"non-periodic" (diurnal), where the vector was an Aedes speciesday-biting mosquito which was present in considerable numbers, and where therewas intimate intermingling of infected natives and of troops. In contrast,filariasis occurred only sporadically in other Pacific islands, such as the NewHebrides, Solomons, and New Guinea where the parasite is nocturnal. Maj. JamesI. Knott, MC, who was assigned to investigate filariasis in the Pacific area inMarch 1944,4 indicated, in his series ofreports,5 that the islands whereAmerican troops had been infected were Tongareva (Penryhn), Bora-Bora
4Memorandum, Maj. O. R. McCoy, MC, Tropical Disease ControlDivision, to Chief, Personnel Service, The Surgeon General's Office, 21Feb. 1944, subject: Assignment of MedicalOfficer for Filariasis Study.
5Reports on Filariasis Bancrofti in American Forces in thePacific Area, April l944-January 1945, by Maj. James I. Knott, MC.
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(Society), Aitutaki (Cook), Wallis, Tutuila (American Samoa), Upolu(British Samoa), Tongatabu (Tonga), and Fiji. He believedthat reports of infection from Apamama (Gilberts), the Solomons, Bismarck,and New Guinea were doubtful and probably in error.
Throughout the filarial belt, some 50 species of mosquitoes,including species of Aedes, Anopheles, Culex, and Mansonia, havebeen reported as possible vectors. About half are known to transmit the diseasenaturally, while the others have been shown experimentally to permit thedevelopment of the parasite and hence are potential vectors. The majority aremore active night biters, and, therefore, the disease is probably transmittedchiefly at night. But in some areas, such as Samoa,6 the principalvector is a day biter, Aedes scutellaris var. pseudoscutellaris. Thisone factor was probably as much responsible as any other for the large number ofcases in the Samoan Defense Area. The troops in this area were instructed inpreventive measures and were provided with means to prevent contact with nightbiters, but the importance of day feeders was not known. It should be noted,however, that many night biters will actively feed during dark days, in thejungle and in quarters.
COURSE
Symptoms and Signs in Natives
To appreciate the problem presented by the epidemics offilariasis in the Armed Forces, it is necessary to point out the difference inthe manifestation and course of the disease among natives in an endemic area andamong adults heavily exposed for the first time. In an endemic area, childrenbegin to be infected in infancy and presumably develop a certain degree ofimmunity. Iyengar7 found that the incidence of microfilariae in the peripheralblood increased from childhood up to the age of 20, and then remained constant,while the incidence of filarial disease, as manifested by symptoms, increasedsteadily up to the age of 45. That is, microfilariae were less apt to be foundin the blood of those showing symptoms than in those symptom free. A similardecrease in the presence of microfilariae with age was found in Puerto Rico, byBercovitz and Shwachman,8 where 5.03 percent of men between 18 and 20years of age, but only 0.92 percent of men between 36 and 38 years of age, werepositive. Of 460 men showing microfilariae in their blood, only 11 gave anyhistory suggestive of filarial disease. Thus, in endemic areas, it appears thatonly a few of those infected develop symptoms, and then after some years ofmicrofilaremia.
6Byrd, E. E., St. Amant, L. S., and Bromberg, L.: Studieson Filariasis in the Samoan Area. U.S. Nav. M. Bull. 44: 1-20, January 1945.
7Iyengar, M. O. T.: Studies on the Epidemiology of Filariasisin Tranvancore. Indian Medical Research Memoir No. 30, Supplemental Series toIndian J. M. Research, 1938.
8Professional History of Internal Medicine in World War II,The Antilles Department, pp. 131-135. [Official record.]
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In a certain number of infected persons, symptoms due toobstruction of lymphatics by adult worms develop. These early symptoms-oftencalled those of the acute stage-consist of recurring lymphangitis, adenitis,and scrotal swelling often accompanied by fever and lasting from several days to2 weeks. Gradually, the attacks become less severe and come at longer intervals.These bouts are called elephantoid fever in some places; agua, in Barbados;mumu, in Samoa; and wanganga, in Fiji. Secondary bacterial, streptococcal orstaphylococcal, infection or trauma has been held necessary for the developmentof these attacks. However, O'Connor,9 in 1933, showed that the presence ofbacteria is not necessary for the occurrence of most of the pathological and allof the inflammatory attacks associated with filariasis. This conclusion has beenamply verified by Wartman10 andby others11 from the studyof cases among the Armed Forces. The role of possible toxic secretions fromadult worms (uterine fluid), of products from disintegrated microfilariae caughtand destroyed in lymph nodes, or of an allergic reaction in the production ofthese recurrent attacks has not been determined.
After the first few attacks of lymphangitis and adenitis, orof funiculitis and scrotal swelling, the limb or genitalia may return to itsprevious size. But, in continually reinfected natives, increasing lymphaticobstruction takes place, so that in the course of time each attack leaves aslight permanent increase in the size of the limb. "At first there isordinary pitting edema, then swelling becomes harder and does not pit; later thewhole limb becomes massive, 'brawny,' harsh and dry, the folds and cracksappear; finally these become infected with septic organisms and ulcerationoccurs."12 This isfilarial elephantiasis, which develops most commonly in the arms, the forearms,the legs, the feet, and the scrotum. Manson-Bahr13has pointed out that it must not be thought that lymphaticelephantiasis is solely due to filarial infection. Lymphatic elephantiasis maybe congenital or familial (Milroy's or Meige's disease); it may be theresult of streptococcic infection, secondary to venous thrombosis; or it may bedue to obstruction from tuberculous glands or malignant growths. Othermanifestations of the chronic stage of filariasis are lymph varices (most commonin the groin), lymph scrotum, chyluria, chylous ascites, arthritis, and filarialabscess. These conditions are seen almost exclusively in natives of endemicareas or in persons who have lived for many years in such areas and have hadrepeated reinfections.
9O'Connor, F. W., cited byLane, C.: Mechanical Basis of Periodicity in Wuchereria bancrofti Infection.Lancet 2: 399-404, 19 Aug. 1933.
10Wartman, W.B.: Lesions of Lymphatic System in Early Filariasis. Am. J. Trop, Med. 24:299-313, September 1944.
11(1) Dickson, J. G., Huntington,R. W., Jr., and Eichold, S.: Filariasis in Defense Force, Samoan Group; Preliminary Report. U.S. Nav. M. Bull. 41: 1240-1251,September 1943. (2) Zuckerman, S. S., and Hibbard, J. S.: Clinicopathologic Study of Early Filariasis.With Lymph Node Biopsies. U.S. Nav. M. Bull. 44: 27-36, January 1945.
12Napier, L. Everard: The Principles and Practice of Tropical Medicine. New York: The MacMillan Co., 1946, p. 674.
13Mason-Bahr, Philip H.:Tropical Diseases, 11th edition. Baltimore: Williams & Wilkins Co., 1942, p. 759.
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Symptoms and Signs in Military Personnel
The picture of filariasis as it occurred in the Armed Forceswas quite different. Symptoms usually began to appear from 5 to 18 months afterfirst possible exposure and consisted of pain, swelling, or redness of an arm ora leg, or pain and swelling in the scrotal region. Constitutional symptoms, suchas chills, fever, malaise, or headache, were rarely reported. A few casesdeveloped symptoms as early as 3 months after the first possible exposure.14In this regard, the case of O'Connor's assistant who developedepitrochlear adenitis 43 days after being bitten by a filariated mosquito ispertinent.15 Dickson, Huntington, and Eichold16described a case in which adult worms were recovered 5? months after the first possible exposure to filariasis.
The observations on different groups of infected men weredescribed in a number of reports to The Surgeon General and later published inthe literature. These have been reviewed by Wartman17whogives an extensive bibliography. Many men were only exposed in an endemic areafor 1 to 2 months, so that symptoms did not develop until their removal to anon-endemic area. In other groups, symptoms began to develop while the troopswere still in the endemic area. No relation was noted between season and onsetof symptoms, nor to time of day.
When the reports of different observers are combined,symptoms referable to the genitalia were the most common initial complaint,although varying from 1118 to 97 percent19indifferent reports. The commonest complaint was of heaviness or mild pain in thescrotum, less often in the groin, frequently first noticed after severe exertionand usually made worse by exercise. On examination, edema of the spermatic cordwas the most constant finding.20 This might be present alone;however, it was frequently accompanied by the swelling of the epididymis or thetesticle and by the presence of a hydrocele or scrotal edema. Absence of thecremasteric reflex on the affected side, attributed to edema of the cremastericmuscle, was thought a helpful early diagnostic sign in some cases.21 Theleft spermatic
14(1) King, B. G.: Early Filariasis Diagnosis and ClinicalFindings; Report of 268 Cases in American Troops. Am. J. Trop. Med. 24: 285-298,September 1944. (2) Burhans, R. A., Camp, J. D., Butt, H. R., and Cragg, R. W.: Lymphangitis of Suspected FilarialOrigin; Preliminary Report Concerning Its Treatment. U.S. Nav. M. Bull. 42: 336-340,February 1944.
15O'Connor, F. W., and Hulse, C. R.: Some PathologicalChanges Associated With Wuchereria [Filaria] bancrofti Infection.Tr. Roy. Soc. Trop. Med. & Hyg. 25: 445-454, May 1932.
16See footnote11 (1), p. 127.
17Wartman, W. B.:Filariasis in American Armed Forces in World War II.Medicine 26; 333-394, December 1947.
18Smith, F. R., Jr.: Filariasis; Study of 737 Patients SoDiagnosed. U.S. Nav. M. Bull. 44: 719-725, April 1945.
19Johnson, P. A. G.: Filariasis;Clinical Findings in 189 Cases. U.S. Nav. M. Bull. 43: 950-954, November 1944.
20Hodge, I. G., Denhoff, E., and Vander Veer, J. B.: Early Filariasis(Bancrofti) in American Soldiers. Am.J.M. Sc. 210: 207-223, August 1945.
21Saphir, W.: Filariasis; EarlyClinical Manifestations; Analysis of 35Cases. J.A.M.A. 128: 1142-1144, 18 Aug. 1945.
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cord was involved more frequently than the right. Bilateralinvolvement was not uncommon.
The entire cord from the internal ring to its junction withthe epididymis might be involved. In some cases, there was only slightthickening of one side as compared with the other, or the entire cord would beenlarged from two to five times its normal size. The swollen cord was usuallyrubbery in consistency, but sometimes nodular. The pain varied from slightdiscomfort to exquisite pain, similar to that resulting from a blow to thescrotum. The funiculitis was descending or retrograde, similar to thelymphangitis seen in the extremities. Fogel and Huntington22were able to follow the development of the lesion in threehospital corpsmen. The onset consisted of lower abdominal pain at which time thespermatic cords were normal on palpation. The authors noted, as follows:
Within 12 hours there was palpable swelling high up in theinguinal canal. The examining finger could be inserted through the externalinguinal ring without causing much discomfort to the patient. As the hourspassed the progress of the swelling could be palpated as it moved down the cord.Within 24 hours that part of the cord lying within the inguinal canal wasgreatly swollen and tender. It was difficult to pass the palpating fingerthrough the external ring because of the swelling and tenderness of the cord. Inthe succeeding 24 hours a scrotal mass was visible and palpable.
Such observations leave little doubt that the acutefuniculitis was an acute lymphangitis of the spermatic cord. As with otherfilarial lesions, the swelling of the cord subsided in a few days to 2 weeks,often to recur one or more times at varying intervals. Frequently, especiallyafter several attacks, slight painless enlargement of the cord persisted and wasprobably the most permanent of all physical findings.23
According to King,24 the globus major was mostfrequently involved, and the body and globus minor only infrequently. In mostinstances, the lesion subsided completely, but in some cases thickening andpalpable nodules remained. Some attached considerable significance to thepresence of a small, shotlike lymph node, located where the vas deferens becomesdistinctly palpable from the epididymis, which might persist for many months.
Acute orchitis, unilateral or bilateral, occurred in from 14to 54 percent of reported cases. Symptoms consisted of pain, swelling, andtenderness. The pain might radiate up to the spermatic cord, or it might appearfirst in the lower quadrant of the abdomen and radiate downward to the spermaticcord and the testicle. Pain was usually not severe. Aspiration in a few casesyielded a small amount of fluid similar to that obtained from an ordinaryhydrocele. Inflammation of the scrotal skin was not uncommon, usually in themost dependent portion of the scrotum, and was not related
22Fogel, R.H., and Huntington, R. W., Jr.: Genital Manifestations of Early Filariasis. U.S.Nav. M. Bull. 43: 263-270, August 1944.
23Leede, W. E., andJosey, A. I.: Early Diagnosis of Filariasis and Certain Suggestions Relative tothe Cause of Symptoms. Ann. Int. Med. 23: 816-822, November 1945.
24See footnote 14 (1), p. 128.
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to the degree of swelling of the cord. Microfilariae were notfound in aspirated hydrocele fluid. Varicocele was reported by a number ofobservers, usually on the left side, but its relationship to filariasis was notdetermined and certainly is open to serious question.25
Acute lymphangitis was the most striking and characteristicphysical finding in acute filariasis, and the one most helpful in making theclinical diagnosis. It occurred in the arm, the leg, the buttock, the groin, theabdomen, or the neck. Regardless of location, retrograde spread wascharacteristic, often starting from a palpable lymph node. It was about twice ascommon in the arms as in the legs in all series reported from the Pacificislands. This is the reverse of Grace's26 report from British New Guinea wherefour-fifths of the patients showed involvement of the legs first. Thelymphangitis of the arms occurred most commonly along the course of the brachialvessels or on the volar surface of the forearm. It took one of three forms-asa red streak of varying length, often with an underlying firm, irregular cord;as a patch of subcutaneous edema and overlying redness, irregular in outline andof varying size, most commonly occurring on the inner anterior surface of theforearm, just below the elbow; or as a diffuse edema and erythema of the upperpart of the arm or the forearm. With erythema, there was local heat, but againtenderness was only mild or moderate. The red streaks were usually shorter,broader, and more diffuse than in bacterial lymphangitis. The characteristicretrograde progression, in contrast to the centripetal progression of bacterialinfection, should be stressed. Lymphangitis of the extremities progressed fromthe axilla down the arm to the elbow, from the antecubital region down theforearm to the wrist, or from the inguinal region either down the inner aspectof the thigh or around the lateral aspect of the thigh, above the greatertrochanter, to the gluteal region.
Hodge, Denhoff, and Vander Veer27believedthat involvement of the deep lymph vessels of the abdomen should be consideredin the presence of pain in the flank or the abdomen, with radiation to thegenitalia or the thigh, and tenderness of the abdomen on the affected side. Itis obvious that other causes of these symptoms, such as appendicitis and renal,ureteral, and retroperitoneal pathological conditions, should be excluded beforeconsidering filariasis as the explanation of the symptoms. An attack oflymphangitis often began to fade in 24 hours, and lasted from a few days to 2weeks. Recurrences were common and characteristic. Chronic lymphangitis,however, was rare.28 Persistent lymph edema was also rare.29
25See footnote 17, p. 128.
26Grace, A. W.:Tropical Lymphangitis and Abscesses. J.A.M.A. 123: 462-466, 23 Oct. 1943.
27See footnote 20, p. 128.
28Behm, A. W., and Hayman, J. M., Jr.: Course of FilariasisAfter Removal From Endemic Area. Am. J.M. Sc. 211: 385-394, April 1946.
29Coggeshall, L. T.: Lymphadenopathy and Filariasis.(Abstract) Bull. U.S. Army M. Dept. 5: 250, 1946.
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Enlarged, slightly tender, discrete lymph nodes withoutattachment to the skin or without suppuration were described by all authors andconstituted the commonest symptom attributable to filariasis. Most criticalmedical officers found it difficult to judge the significance of enlarged nodes,particularly when the enlargement was slight, nontender, and in the more commonsites for palpable nodes, such as the axilla and the groin. Among marines atKlamath Falls, Ore., Coggeshall30 foundenlarged nodes in 60 percent of 200 men diagnosed as filariasis, in 57 percentof 271 men evacuated for malaria, and in 50 percent of 98 controls who had neverbeen overseas. Adenopathy was more suggestive of filariasis when the enlargementcame on acutely without ascribable cause and when it occurred in places whereenlarged nodes are not usually palpable, such as the antecubital area, theepitrochlear region, particularly above the site of the common epitrochlearnode, the intercostal region, the popliteal space, in the back, the wrist, thetip of the ilium, or in the region of the teres and serratus muscles.
Transient or fugitive swellings, believed to be evidence ofhypersensitivity to filarial products, were described in arms, legs, hands,feet, torso, eyelids, and forehead. According to Burhans, Camp, Butt, and Cragg,31 the swellings developed along the path of lymphatic vessels or atthe edges of muscles. Fogel and Huntington (p. 129) observed them in areolartissue. These swellings were raised, usually slightly tender, and sometimesresembled erythema multiforme. They lasted from a few days to 2 weeks anddisappeared without residua. No worms were found in biopsies from suchswellings.
Filarial abscess, or abscess or suppurating nodes attributedto filariasis, was extremely rare. Glauser32 reported three cases and Englehornand Wellman33 two cases. No worms or filariae were found in the pus.
The initial attack lasted from 3 to 5 days to 2 weeks,occasionally as long as a month. King34 recorded fever in 53 (19.7 percent) of 268cases. Usually, the temperature did not exceed 99? or 100? F., but in a fewcases it reached 102? or 104? F. A striking feature of these attacks was thelack of severe constitutional symptoms. The patients did not feel sick, andthe local lesions were not extraordinarily painful. In no instance did thereseem to be danger to life. From the military standpoint, the attacks were mostimportant because the lesions were incompatible with full field duty. Theaverage hospital stay in King's series was 15.9 days.
Recurrences of adenopathy, lymphangitis, and scrotal swellingwere common and characteristic. They occurred at intervals of a few days to
30Coggeshall, L. T.:Filariasis in Serviceman; Retrospect and Prospect. J.A.M.A. 131: 8-12, 4May 1946.
31Burhans, R.A., Camp, J. D., Butt, H. R., and Cragg, R. W.:Lymphangitis of Suspected Filarial Origin; Preliminary Report Concerning Its Treatment.U.S. Nav. M. Bull. 42: 336-340, February 1944.
32Glauser, F.: Filariasis inReturning Marines. U.S. Nav. M. Bull. 44: 21-26, January 1945.
33Englehorn, T. D., and Wellman, W. E.: Filariasis in Soldierson Island in South Pacific. Am. J.M. Sc. 209: 141-152, February 1945.
34 See footnote 14 (1), p. 128.
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several months. Relapses became less frequent and severe withthe passage of time, but during the first 12 to 18 months this was not alwaystrue, and not infrequently a relapse would be more severe than the initialattack. Relapse was observed as long as 2 years after the initial attack.35The frequency of relapse diminished rapidly after evacuation to the UnitedStates. Complaints of subjective symptoms were far more common than objectivefindings. Coggeshall (p. 131) commented that men assigned to tasks they likeddid not complain; men on the football and basketball teams did not experienceany difficulty, while men on guard duty or police detail would complainbitterly. Behm and Hayman36 believedthat complaints of pain unaccompanied by recurrence or increase in swelling ofnodes, scrotal contents, or lymphangitis should not be regarded as due tofilariasis but rather should be more properly interpreted as due to musclestrain, fatigue, arthritis, or some other cause. Nearly all observers believedthat relapses were prone to be precipitated by severe physical exertion.37Coggeshall, however, was unable to precipitate a recurrence by exhaustingexercise in 10 marines after their return to Klamath Falls. Behm and Haymanreported from a study of 408 men, diagnosed to have filariasis, who had been ina hyperendemic area for 1 year and then observed for 14 months after removal,that the number of attacks varied from 1 to 13, as follows:
Number of attacks | Number of men |
1 | 139 |
2 | 99 |
3 | 76 |
4 | 53 |
5 | 21 |
6 | 10 |
7-13 | 10 |
No attacks were observed in this group later than 13 monthsafter removal from the endemic area. A number of other reports noted the rapiddisappearance of signs and symptoms after return to the United States.38
Laboratory Examinations
Routine laboratory examinations were of little value indiagnosis.39 No abnormalities of the urine attributable to filariasis weredescribed. From the reported data, the total white blood cell count averagedabout 9,000, with extremes of 3,600 and 19,000 per cubic millimeter. There wasno significant alteration in the number or the form of neutrophils, lymphocytes,
35Coggeshall, L. T.: Malaria and Filariasis in ReturningServiceman; Ninth Charles Franklin Craig Lecture.Am. J. Trop. Med. 25: 177-184, May 1945.
36See footnote 28, p. 130.
37(1) Brown, Maj.T. McP., Stifler, Capt. W. C., and Bethea, Capt. R. W.,Jr.: Supplementary Report From the 118th General Hospital on 536 Officers andEnlisted Men From 134th Field Artillery Battalion, 31 July1944. (2) See footnote 28, p. 130, and footnote 23, p. 129.
38(1) See footnote 32, p. 131,and footnotes 18 and 19, p. 128. (2) Zeligs, M. A.: Psychomatic Aspects of Filariasis; Present Day Evaluation, J.A.M.A. 128: 1139-1142, 18 Aug. 1945.
39See footnote 17, p. 128.
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or mononuclear cells. In his review, Wartman observed:"Eosinophilia occurred in one-half to two-thirds of the cases, the averagebeing about 850 cells per cu. mm. Most authors thought the presence ofeosinophilia was not helpful in diagnosis." Eosinophilia was not observedin Leede and Josey's patients. On the other hand, King, and Hodge, Denhoff,and Vander Veer found that the incidence of eosinophilia (9 percent or above)was significantly greater in soldiers exposed to filariasis. Among exposedtroops with signs of filariasis, the incidence of eosinophilia was greater thanin those with no evidence of the disease but was twice as great in those withslight or doubtful findings, as in those with frank clinical filariasis. Nosignificant changes were found in red blood cell counts, hemoglobin, orsedimentation rate. Bacterial cultures of biopsy material, blood, aspiratedfluid from lymph nodes, and hydroceles showed no pathogens.
Despite many thousands of blood examinations, by all knownmethods, at all times of the day and night, microfilariae were only found in theblood of approximately 20 cases. Since some of these men had served in PuertoRico, the source of infection could not always be established. Flynn40found 8 positive blood or lymph node aspirationmaterial in 125 patients. Hodge, Denhoff, and Vander Veer (p. 128) found asingle microfilaria in 2 blood samples among over 2,000 taken from 266 soldiers.Leede and Josey found microfilariae once in an individual who had lived foryears in an endemic zone in childhood. Goodman, Weinberger, Lippincott, Marble,and Wright41 reportedfinding microfilariae on one occasion in each of 2 soldiers among 145 examinedon 7 nights and 3 days by the Knott concentration method. In other large groupsof men, including those reported by King and by Behm and Hayman, nomicrofilariae were found despite careful and repeated study by Knott's methodas well as by thick smears.
The "new" disease which was epidemic among troopsin certain Pacific areas was first definitely established as filariasis by thedemonstration of adult worms and microfilariae in biopsied lymph nodes andlymphatics. Wartman (p. 127), Michael,42 Hartz,43 andRifkin andThompson44 described the pathological findings in biopsy material, and Wartman(p. 128) summarized all the material available in the Army Institute ofPathology. As a result of these studies, Wartman concluded that it was clearthat the adult filaria worms in the lymphatic system might cause a granulomatousinflammatory reaction. When in lymph nodes, the changes were often not confinedto the immediate vicinity of the worms but were present throughout
40Flynn, P. D.: FilariasisSuspects; Review of Cases Admitted. U.S. Nav. M. Bull. 42: 1075-1079, May 1944.
41Goodman, A. A., Weinberger, E. M., Lippincott, S. W., Marble, A., andWright, H. W.: Studies of Filariasis in SoldiersEvacuated From South Pacific. Ann. Int. Med. 23: 823-836, November 1945.
42Michael, P.: Filariasis: Histopathologic Study. U.S. Nav. M. Bull.45: 225-236, August 1945.
43Hartz, P. H.: Contribution to Histopathology of Filariasis.Am. J. Clin. Path. 14: 34-43, January 1944.
44Rifkin, H., and Thompson, K. J.: Structural Changes in Early Filariasis. Arch. Path. 40: 220-224, October 1945.
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the node. Michael believed that the sex of the infecting worminfluenced the histological changes, male worms degenerating somewhat earlierand faster than females, and fertilized females still more slowly. Many of thechanges found in worm-infested nodes were also observed in tissues in which noparasites were discovered, even in serial sections. Biopsies of such nodes atthe height of enlargement showed marked hyperplasia, infiltration witheosinophils, and distention of lymphatic sinuses. Changes in lymph vesselsconsisted of dilatation, lymph thrombosis, and acute lymphangitis which wassometimes necrotizing. In some, these changes appeared reversible, but in othersfibrosis and obstruction of the affected lymphatic vessel had ensued. Nodifference could be detected in the changes associated with the presence ofliving or dead worms. From his failure to find parasites in genital lesions,Michael speculated that many genital enlargements were toxic or allergic innature, and not due to direct invasion of the organs by parasites, and thattherefore the changes could be presumed to be reversible. In a study of 58biopsies from the Pacific area, Wartman found adult worms in 8 (13.8 percent)and microfilariae in 3 (5.1 percent) and regarded the histological picture in 24(51.0 percent) of the biopsies that showed no parasites as characteristic of thedisease. Michael reported finding adult worms in 30 percent of 120 biopsies. Healso pointed out that, if a cut node is placed in saline solution, the adultworm may be found in the ambient fluid in 24 to 48 hours, thus saving the laborof serial sections. While the demonstration of adult worms or microfilariae issatisfactory proof of the diagnosis, biopsies should not be undertaken lightlyor routinely. Biopsies from the inguinal and femoral region are usuallyunsatisfactory and frequently lead to prolonged disability. Excision of lymphnodes or other tissue while acute symptoms are present may be followed by severeexacerbation of symptoms. An epitrochlear or other unusually enlarged node, or apalpable lymphatic cord, taken as an attack subsides is apparently the mostprofitable site for biopsy.
Because of the failure to demonstrate microfilariae in theblood and the difficulty in making a reasonable clinical diagnosis offilariasis, numerous attempts were made to develop a satisfactory laboratorytest. Older observations had shown that there is in the filariids a common groupreacting factor capable of eliciting an intradermal response in personsharboring filarial infection and that antigens prepared from these filariidscould also be used in serologic tests. Because of the impracticality ofobtaining adult W. bancrofti, mostworkers had used a related filariid, especially the dog heartworm, Dirofilariaimmitis. Taliaferro and Hoffman45 had originally used a 1: 200dilution of saline extract of the dog heartworm, while Fairley46found that a 1: 1,000 dilution gave fewer falsepositive reactions.
45Taliaferro, W. H., and Hoffman, W. A.: Skin Reactions to Dirofilariaimmitis in Persons Infected WithWuchereria bancrofti. J. Prev. Med. 4: 261-280, July 1930.
46Fairley, N. H.: The Skin Test and Complement FixationReaction in Filariasis. Tr. Roy. Soc. Trop. Med. & Hyg. 25: 220, 1932.
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Since no prepared antigen was available from supply, overseaunits prepared their own antigens from D. immitis procured locally. King47showedthat even minor differences in the method of preparation made significantdifferences not only in patients but in controls. The results of these studies,both overseas and in the United States, are summarized by Wartman. In general,antigens prepared from D. immitis gave false positive reactions in 5 to 14 percent of men who had never beenin an endemic area and in 83 to 91 percent of those showing clinical symptomsthat might be filariasis. A finding that made the interpretation of these skintests particularly difficult was the increased incidence of positive reactionsin men who had tropical service in a nonfilarial area or in one of very lowendemicity, as well as among those who had served in an endemic area but hadnever had symptoms. The former was as high as 27 percent in some series. Thelatter might be attributed to a "biological" rather than a"clinical" infection; that is, to an infection sufficient to produceskin sensitization but no symptoms, comparable to that observed in certainindividuals who give a positive reaction to Trichinella antigen.Huntington's48 conclusions that while the skin test is helpful in the generalstudy of the incidence and epidemiology of filariasis, it is not particularlyhelpful in the diagnosis of individual cases, would be echoed by most observers.Both immediate and delayed reactions were observed; the immediate beingapparently the more sensitive, the delayed giving fewer false positivereactions. The use of other filariid antigens (Setaria equina, Litomosoidescarinii) gave similar results. The presence of intestinal helminths apparentlymade no significant difference in the incidence of positive reactions.Bozicevich and Hutter49 believed that the test was made more specific by use ofa 1: 8,000 dilution of antigen. Complement fixation and precipitin reactionswere not found to be particularly useful.
With this brief review of filariasis, as described in mosttextbooks of medicine, and of the symptoms and findings in acute epidemicfilariasis as encountered among military personnel in World War II, it is hopedthat the description of the experience in different units (p. 138) and in thevarious theaters can be appreciated.
INCIDENCE
When the marines went into the Samoan area early in 1942,there was extreme military necessity of getting under cover as quickly aspossible. The native villages were the most available sites. As a result, therewas intimate contact between troops and the heavily infected native population.
47See footnote 14(1), p. 128.
48Huntington, R.W., .Jr.: Skin Reactions to Dirofilaria immitis Extract.U.S. Nav. M. Bull. 44: 707-717, April 1945.
49Bozicevich, J., and Hutter,A. M.: Intradermal and Serological Tests With Dirofilaria immitis Antigenin Cases of Human Filariasis. Am. J. Trop. Med. 24: 203-208, May 1944.
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The possibility that the troops might become infected withfilariasis was not seriously considered, for the region had been occupied bywhite men for a number of years without evidence of infection. Indeed, somebelieved that the white man was not susceptible. Previous white residents of thearea had lived apart from native villages and in screened quarters. Moreover,while the men were equipped with mosquito nets, it was not recognized that theimportant vector of filariasis in this area was the day-biting A. scutellarisvar. pseudoscutellarisand that the microfilariae in this area were nonperiodic. As a consequenceof living in and near native villages and of a day-biting vector, these men weresubjected to a large number of infected bites in a relatively short time. In allof the Pacific islands, a high incidence of infection among troops occurred onlywhere these two conditions existed.
It is difficult to get precise data on the number of meninfected. Coggeshall (p. 131) estimated that 38,300 men of the U.S. Navy and theU.S. Marine Corps were exposed, and a filarial registry showed 10,421 diagnosedcases. Many of these were erroneous diagnoses, but on the other hand there weremany cases in which the diagnosis of filariasis was not entered on the healthrecord.
The approximate number of primary admissions for filariasisin the years 1942-45 is shown in table 18. One death was recorded in anoversea theater in 1944.
TABLE 18.-Admissions forfilariasis in the U.S. Army, by area and year, 1942-45
Area | Number of cases | ||||
| 1942 | 1943 | 1944 | 1945 | |
Continental United States | 481 | --- | --- | 391 | 90 |
Overseas: |
|
|
|
|
|
| Europe | --- | --- | --- | --- | --- |
| Mediterranean1 | 9 | --- | 8 | 1 | --- |
| Middle East | 1 | --- | --- | 1 | --- |
| China-Burma-India | 2 | --- | 1 | 1 | --- |
| Southwest Pacific | 323 | --- | 70 | 233 | 20 |
| Central and South Pacific | 1,348 | --- | 557 | 741 | 50 |
| North America2 | 1 | --- | 1 | --- | --- |
| Latin America | 307 | 3 | 18 | 216 | 70 |
|
| 32,002 | 3 | 660 | 1,194 | 145 |
|
| 32,483 | 3 | 660 | 1,585 | 235 |
1Includes North Africa.
2Includes Alaskaand Iceland.
3Includes admissionson transports.
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The admissions tabulated as from continental United Statesrepresent infections acquired overseas. The marked decrease in 1945 as comparedwith 1944 was due to the movement of the war away from hyperendemic areas, aswell as to better mosquito control, and to the separation of troops and natives.The average number of days lost per man in 1943 was 112, while in 1945 it was66. The annual admission rate for filariasis per 1,000 mean strength in theCentral and South Pacific Area was 1.91 in 1943 and 1.69 in 1944. A few caseswere reported in Puerto Rican troops who had probably been infected in PuertoRico before military service. The chief sources of infection in Army units wereBora Bora, Aitutaki, Tongareva, Fiji, and Tongatabu Islands (pp. 125-126).
DISCUSSION OF EPIDEMIC
Full consideration must be given to the fact that themilitary activities in the Pacific areas early in the war were such that thetactical situation had highest priority. In commenting on the epidemic in Samoa,Wallis, and Aitutaki, Knott reported50 that recommendations by medical officersthat natives be removed from camp areas raised objections from islandgovernments and were vetoed by area commanders. Many medical officers could notbelieve that the lymphangitis observed in troops was filarial. No one was tospeak or write of filariasis. To combat rumors, Knott reported, the areacommander put out the famous order that no case was to be called filariasisbecause "this disease does not affect white men." The men themselves,however, believed the natives. Shortly after this order, the diagnosis wassettled by finding worms in biopsy material. Knott commented further:
The army units in the Central Pacific Area were not warnedofficially that filariasis had broken out in the marines on Samoa and Walliswhen it first broke out, but the medical officers promptly passed the word alongto the others. Officers from the Army islands visited Samoa and learned whatthey could. But here again the information was gotten after the units hadalready been infected. And again, the medical officers could not convince theisland commanders that they should exclude the natives from the camp areas.Perhaps the area commanders would have listened to the medical officers ifthey had had scientific data to prove the danger of the situation. Butthere were no epidemiologic mosquito survey, nor mosquito control units inthe area.
The men who had seen examples of filariasis among the nativeswere extremely fearful of the diagnosis, believing that they would suffersimilar disfigurement and particularly that they would be sterile. The obviousignorance of medical officers of the disease only seemed to increase thisapprehension, lower morale, and lead to the conviction of the men that they hadbeen afflicted with a serious and incurable disease about which nobody knewanything. Examples of the ignorance of the disease are the remark of a (Navy)consultant who when shown sections of worms in biopsied glands said that thiscouldn't be filariasis, since no microfilariae were found in
50See footnote 5,p. 125.
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peripheral blood but must be a new disease,51 and by the action of a postmedical inspector who, in recording the admission of 108 patients diagnosedfilariasis, reported as follows:
Immediate and rigid precautions were taken to isolate patients by restrictionof the patients to the ward several hours before dusk; by careful,complete screening of the building in which they were housed; by spraying of thescreens and doors several times during the day and night. ** * blood smears were taken during day and night inan attempt to detect the presence of microfilariae. However, these smearswere entirely negative.52
The impact of such treatment on the emotional reaction of the men and theirfamilies can well be imagined.
Another example of ignorance of the disease was noted in a report53 whichcontained the following statement:
It is known that the microfilaria cannot reproduce themselves asexually.It takes a number of months for the microfilaria to develop into the adultmacrofilaria. We have seen adult macrofilaria in the human from 15 to 18months after exposure and so know that the adult forms can develop in this time;* * *. Itis necessary to have an adult male and female macrofilaria in close harmony toproduce sexually mature microfilaria.
It is hard to believe that the writer, who was making the diagnosis offilariasis and talking to patients, knew even the life cycle of the parasite!
That the disease was filariasis was recognized officially in a directive fromthe Surgeon General of the Navy, dated 23 May 1943. The directive clarified theadministrative handling of filariasis and directed that those so diagnosed betransferred to the nearest U.S. naval hospital in the United States to behospitalized until free from symptoms and not to be sent again into endemicareas. The presence of microfilariae did not restrict movement. No such definiteevacuation policy was established by the Army.54 War DepartmentCircular No. 189, 21 August 1943, specified that filariasis was disqualifyingfor service in tropical areas; War Department Circular No. 293, 11 November1943, provided that men suffering from filariasis would not be dispatchedoverseas; and War Department Technical Bulletin (TB MED) 142, "Filariasis(Wuchereria) With Special Reference to Early Stages," appeared in February1945, but by this time the epidemic overseas was past.
UNIT HISTORIES
The history of two Army units illustrates the difficulty in diagnosis, theresults of indecision, and the loss in manpower caused by filariasis. The 134thField Artillery Battalion and the 404th Combat Engineer Company (Separate) weredispatched overseas in April 1942 and were stationed
51Personal experience.-J. M. H., Jr.
52Monthly Sanitary Report for Month of July,Halloran General Hospital, 3 Aug. 1943.
53Essential Technical Medical Data, South PacificBase Command, for February 1945, dated 12 Mar. 1945.
54To the bestof my knowledge.-J. M. H., Jr.
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on Tongatabu, where the nonperiodic form of filariasis washighly endemic, from May 1942 to May 1943. No symptoms recognized as due tofilariasis developed during this time. These units left Tongatabu in May 1943,stopped at New Caledonia and in Townsville, Australia, and then were stationedon Woodlark Island, southeast of New Guinea, until January 1944. While WoodlarkIsland is in the filarial zone, the endemicity is extremely low, if any. AnAustralian mine superintendent who had lived on the island for 30 years reportedthat he had never seen evidence of the disease among natives, and physicalexaminations and blood smears on 100 natives showed no evidence of filariasis.55In addition to the men who had been on Tongatabu, 145 replacements were withthem on Woodlark. Recurrent lymphangitis, scrotal swelling, and adenopathy beganto develop in the Tonga group about August 1943. Many men who complained of painand discomfort showed no significant physical findings. Similar symptomsdeveloped at the same time among the replacements who had never been onTongatabu. Because of the number of men exhibiting symptoms, the uncertainty ofthe actual number infected, and the loss of morale and efficiency, the unitswere transferred to Sydney, Australia, and examined by the staff of the 118thGeneral Hospital.56 In addition to history, physical examination, and bloodstudies, skin tests were done with a 1:1,000 extract of D. immitis. The results of these skin testsare shown in table 19.
TABLE 19.-Results ofskin tests for filariasis, 118th General Hospital, 1944
Group tested | Number of tests | Positive reaction | |
| Percent | ||
Tonga | 502 | 368 | 73.3 |
Non-Tonga | 143 | 35 | 24.5 |
Control1 | 72 | 13 | 18.1 |
No tropical service | 100 | 11 | 11.0 |
1Personnel of 118th General Hospital.
On the basis of history, examination, and skin tests, it wasconcluded that 494 of 526 men who had been on Tonga and 17 of the 144 who hadonly been on Woodlark showed evidence of filariasis. The commanding officer ofthe Sixth U.S. Army recommended that these units be returned to the UnitedStates because (1) their combat efficiency had been seriously impaired, (2)rehabilitation would extend over a long period, (3) their future combat valuewas highly doubtful, and (4) replacement of all individuals
55Letter, Maj. Albert M. Dashiell, Headquarters, Sixth Army, toSurgeon, Sixth U.S. Army, 11 Nov. 1943, subject: Filariasis.
56Brown, Maj. T. McP., Stifler, Capt. W. C., Jr., andBethea, Capt. W. R., Jr.: Preliminary Report of Filariasis Survey of 501 MenFrom 134th Field Artillery Battalion and 171 Men From 404th Combat EngineerCompany (S), 10 Mar. 1944.
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showing evidence of filariasis would result in a state oftraining far below that required for efficient combat.57
The personnel of the organizations returned to the UnitedStates as patients in July 1944. When they reached Moore General Hospital,Swannanoa, N.C., the troops had been overseas 27 months, had never been incombat, and had been hospitalized for 7 months. The men were confused,apprehensive, and discouraged. They had, many of them, seen some of the latesequelae of filariasis, had been conscious of the concern and indecision of themedical officers who had examined them, and commonly believed that they wereafflicted with an incurable, progressive, and eventually disfiguring andincapacitating disease. This was borne out by the men's own opinion of theirability to do duty. Of the 134th Field Artillery who had been on Tonga, 24percent thought they were fit for full duty, 70 percent that they were fit onlyfor limited duty, and 6 percent that they were completely incapacitated. Afterthorough study and from 2 to 10 months' observation, 196 (36.8 percent) ofthose who had been on Tonga were diagnosed as filariasis. Of these, three wereseparated from the service because of filariasis, one with persistent lymphedema of both legs, one with a lymph scrotum, and one with recurrentlymphangitis; the others were returned to duty in the Zone of Interior inaccordance with current directives. No microfilariae were demonstrated onrepeated search. The number of recurrent attacks of lymphangitis, adenopathy, orscrotal swelling was difficult to estimate, since many more were recounted bythe men than were documented in medical records or observed by a medicalofficer. On the basis of histories of 408 men, 139 stated that they had had asingle attack; 99, two attacks; 76, three; 53, four; 10, six; and only 10, morethan 10 recurrences. No evidence of recurrence of physical findings that couldbe attributed to filariasis was observed later than 25 months after removal fromthe endemic area. Of 308 men returned to duty as nonfilarial and followed for anadditional 8 months, 3 presented sufficiently characteristic symptoms ofrecurrent adenopathy to justify a change in diagnosis to
Group tested | Percent positive with antigen dilution of | |
| 1:8,000 | |
Tonga | 73.3 | 57.7 |
Woodlark | 24.5 | 18.3 |
Control | --- | 6.0 |
57Letter, Lt. Gen. Walter Krueger, Headquarters, Sixth U.S. Army, to Commanding General, U.S. Army Forces, Far East, 8 Apr. 1944, subject: Return of 134th Field Artillery Battalion and 404th Engineer Company (C) (Separate) to the United States.
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filariasis. The entire group was skin tested according to thetechnique of Bozicevich and Hutter, using a 1: 8,000 dilution of antigen. Theresults of these tests in comparison with those done overseas are shown in table20.
Of the men discharged because of filariasis, 79.5 percent hada positive skin test while 42.0 percent of the "not filariasis" Tongagroup and 19.1 percent of the Woodlark group did also. The former might bethought of as due to a "biological" rather than "clinical"infection; that is, to an infection sufficient to produce skin sensitivity butno symptoms, comparable to that observed in certain individuals who give apositive reaction to Trichinella antigen. But it is hard to apply thisexplanation to the Woodlark group where the possibility of infection was veryproblematical. This obviously makes the skin test of less value in the individualcase than would be desirable.
The history of these two units has been given in some detailbecause they were the most carefully studied of Army units and because theexperience in other groups of men exposed in hyperendemic areas was similar. Theamount of physical incapacity was slight in proportion to that produced by fear,anxiety, and uncertainty. Zeligs58 presentedfactual data which showed that these fears were groundless. The longer theperiod of inactivity because of a diagnosis of filariasis, the moredifficult it was to return men to duty. When presented with evidence of theirability to lead normal lives and with the demonstration that they could exercisewithout producing symptoms, most men ceased to be concerned. Those with a pasthistory of psychoneurotic behavior, or where the element of secondary gain wasprominent, frequently used filarial symptoms to help solve preexisting emotionalproblems or to escape unpleasant situations. The ignorance of most medicalofficers of the disease led to a diagnosis of filariasis in men who had neverbeen in an endemic area or who suffered from angioneurotic edema,thrombophlebitis lymphogranuloma venereum, and epididymitis secondary to aurethritis.
DIAGNOSIS
The diagnosis of early filariasis is not easy. Demonstrationof microfilariae in the peripheral blood or of adult worms in biopsy material isthe only proof. Care should be taken with blood smears to prevent contaminationwith filarial-like structures.59 Usually, the diagnosis must be made on historyand clinical findings. History of exposure in an endemic area is of primeimportance; the diagnosis should not be entertained without it. History oflymphangitis, adenopathy, or scrotal pain is unreliable. An acute attack ofretrograde lymphangitis, adenopathy, particularly in
58See footnote 38 (2), p. 132.
59Manson-Bahr, P.: ASpurious Blood Parasite From Fiji. Tr. Roy. Soc. Trop.Med. & Hyg. 45: 12, 1951.
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unusual locations, funiculitis, epididymitis, or orchitis should be observed.All other discoverable causes for the symptoms should be excluded. The skin testis helpful in surveys but is not reliable in the individual. Exercise tests areof value where they precipitate acute attacks.60
PREVENTIVE MEASURES
Prevention of infection in troops depends upon information on the presence ofmicrofilariae among natives, whether the parasite is diurnal or periodic, and onthe important local vectors. The greatest danger is where the parasite isdiurnal and the vector a day biter. Under such conditions, separation of troopsand natives is essential. Studies by Byrd, St. Amant, and Bromberg61 showed that, while 25 percent ofAedes scutellaris collectedin the center of a native village might be infected, the infection rate droppedto zero at 200 yards. Thus, while this mosquito has a short flight range, othervectors have a longer range. Where the tactical situation permits, troop areasshould be at least 1 mile from native villages, or the latter moved. All methodsfor mosquito control should be instituted. Where the vector is a day biter,preventive measures, such as the wearing of long sleeves and full-lengthtrousers and the frequent application of repellent, should be enforced.
The value of observing the principles of military sanitation was shown by Lt.Gen. Thomas E. Watson, U.S. Marine Corps,62on the island ofUpolu. About 90 percent of the troops were in a camp around an airfield. Nativeswere excluded from the camp, and mosquito-control measures were carried out inthe area. Only rare cases of filariasis developed, and these may not have beenacquired in the area. The other 10 percent of troops, stationed in the town ofApia, intermingled with natives and a number acquired filariasis.
When the presence of filariasis among troops was recognized, measures weretaken not only to prevent further infection, but to minimize the possibility ofdevelopment of late complications from prolonged exposure. Filariasis wasdesignated as disqualifying for duty in tropical areas, and later for anyoversea assignment (p. 138).
Another problem arose late in the war with the transfer of prisoners of warfrom heavily infected Pacific islands to Hawaii and continental United Stateswhere possible vectors existed.63 Between June 1945 and the endof hostilities, over 4,000 prisoners from Okinawa were received
60War Department Technical Bulletin (TB MED) 142, February 1945.
61See footnote 6, p. 126.
62See footnote 5, p. 125.
63(1) Newton, W. L., Wright, W. H., and Pratt,I.: Experiments to Determine Potential Mosquito Vectors of Wuchereriabancrofti in ContinentalUnited States. Am. J. Trop. Med. 25: 253-261, May1945. (2) Scott, O. K., Richards, C. S., and Seaman, E. A.: Experimental Infectionof Southern California Mosquitoes With Wuchereriabancrofti. J. Parasitol. 31: 195-197, June 1945.
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in the Hawaiian Islands, 16 percent of whom showedmicrofilariae.64 It was promptly recommended that these men bereturned to one of the islands of the western Pacific or to relativelyuninhabited islands where introduction of the disease would be of smallconsequence.65
CONCLUSIONS
A valuable, though expensive, lesson can belearned from the experience with filariasis in World War II. Medical officersshould be given all the information available about the diseases in the areainto which they go. As information is obtained from one service or area, itshould be passed on rapidly, at least as information bulletins, to otherofficers. While "a little knowledge is a dangerous thing," it isbetter than none. The War Department technical bulletin on filariasis (p. 138)did not appear until the epidemic was over. The importance of a knowledge ofmilitary sanitation for every medical officer in the field, no matter how highhis other professional qualifications, was demonstrated again. To this might beadded the ineffectiveness of such knowledge unless commanders can be convincedof its importance.
It is highly improbable that any number of men infectedoverseas will have symptoms or incapacity attributable to filariasis in thefuture. A few may develop an asymptomatic microfilaremia. A few such cases havebeen reported.66 This is consistent with Neumann's observationsthat microfilariae are not commonly found in the peripheral blood before theseventh year after infection. If no longer exposed to reinfection, suchmicrofilariae may persist for 15 years, which apparently is the average life ofthe worms.67 Such cases, even should they occur, would be soscattered that the chance of establishing a focus of the disease in the UnitedStates is negligible.
There is no specific treatment for the acute attacks offilariasis. The sulfonamides and antibiotics are without effect unless bacterialinfection is superimposed. Rest and administration of mild analgesics, such asacetylsalicylic acid, during the presence of acute symptoms are all that isrequired. Of a large number of drugs studied for effect on microfilariae,
64History of Preventive Medicine, Headquarters, U.S. ArmyForces, Middle Pacific, ch. 34. [Official record.]
65Swartzwelder, J. C.: Filariasis Bancrofti. In MedicalDepartment, United States Army. Preventive Medicine in World War II. Volume VII.Washington: U.S. Government PrintingOffice, 1964.
66(1) Eyles, D. E., Hunter, G. W. III, and Warren, V. G.:Periodicity of Microfilariae in 2 Patients With Filariasis Acquired in SouthPacific. Am. J. Trop. Med. 27: 203-209, March 1947. (2) Conn, H. C., andGreenslit, F. S.: Filariasis Residuals in Veterans With Report of Case ofMicrofilaremia. Am. J. Trop. Med. 1: 474-476, May 1952.
67Neumann, H.: Filariasis in White Man. J. Trop. Med. 47:25-28, June-July 1944.
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diethylcarbamazine (Hetrazan) is the most promising.68 It is quiteeffective in reducing or abolishing microfilaremia. Its effect on adult worms isless definitive.
68(1) Santiago-Stevenson, D., Oliver-Gonzalez, J.,and Hewitt, R. I.: Treatment of Filariasis Bancrofti With 1-Diethylcarbamyl, 4-Methylpiperazine Hydrochloride("Hetrazan"). J.A.M.A. 135: 708-712, 15 Nov. 1947. (2) Kessel, J. F., Thooris, G.C., and Bambridge, B.: Use ofDiethylcarbamazine (Hetrazan or Notezine) in Tahiti as an Aid in Control of Filariasis. Am. J. Trop. Med. 2:1050-1061,November 1953.
