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*18 MED 142 NAVMED P·5052·1

AFP 160·5·14 DEPARTMENT o F THE ARM Y TECHNICAL BULLETIN o EPA R T MEN T

DEPARTMENT OF

OFT H E

THE AIR

N A V Y N A V M E 0 FORCE PAMPHLET

FILARIASIS (WUCHERERIA) WITH SPECIAL REFERENCE TO EARLY STAGES

Departments or the Army. the Navy, and the Air Foree. Washington 25. D. C. 28 March 1956

PIr .... o",.pA PI!.~. Purpose ______________________________________________________________________ .__________________ I General ___________________________________________________________ ". _____________ .______________ 2 Epidemiology ___ _ _ __ _ _ _ _ __ _ _ __ _ _ __ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ ___ __ _ _ _ _ _ _ _ _ _ 3 I COUffle _____________________________________________________________________ . _______ • _____ ._.____ 4 6 DiagnOBis. _ _ _ _ _ __ _ _ _ _ _ _ _ _ __ _ _ _ _ __ _ _ _ _ _ __ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ __ _ __ _ _ __ _ _ _ _;5 8 Treatment____ _ _ _ _ _ _ __ _ _ _ _ __ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ __ _ _ _ _ _ _ __ _ 6 9 Prognosis________________________________________________________________________________________ 7 10 Disp06itioll ___________________ ~ ________________________ ~ _____________________________ "_ _ _ _ _ _ __ _ _ _ _ 8 10 Prevention~~ ___________________________________ ~~_______________________________________________ 9 II

1. Purpose. This technical bulletin is pub­lished to provide Medical Service officers with information concerning the early stages of filari­asis, with particular reference to prevention and management.

2. General. Technically speaking, filariasis is an infection with one of the nematodes belonging to the superfamily Filaroidea. In practice, how­ever, the term is commonly used to refer to an infection of the lymphatic system with nematodes of the genus Wuch.ereria. Many of the infections with other filariae have specific names; e. g., onchocerciasis, loaiasis. In this bulletin the term filariMis will be used in the restricted sense. Wuchereria bancrojti and W. malayi are the only known species found in man. The former is the best known and most widely distributed. In general, except where otherwise noted, theJollow-

*This bulletin supersedes TB Med 142, February 1955.

TAGO 5S89A-Mllr. 360473'-1\6

ing statements apply to infections with either worm. These are the worms associated with the production of elephantiasis. However, overem­phasis of this condition has minimized the more common and painful attacks of filarial fever, the "mumu" of Samoa.

3. Epidemiology. a. Geographic Distribution. Although filariasis is widespread among natives of practically all tropical regions, a high preva­lence of infection is usually found only in limited areas. The exact distribution of filariasis is known for only a relatively small portion of the extensive regions in which the disease occurs.

(1) Infection due to W. bancrqfti is endemic in a wide belt around the world, between latitudes 41 0 north and 300 south (See fig. 1). In most pl!I.Ces its distribution is spotty; large variations in prevalence

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are often noted·in adjacent villages, and it is absent from some tropical regions where conditions for spread are apparent­ly favorable. For example, W. bancrofti has not established itself in Panama al­though it is common on many of the West Indian islands, and large numbers of natives with filariasis have migrated from these islands to the Isthmus. In the United States, an endemic area of W. bancrojti formerly existed in the vicinity of Charleston, South Carolina, but no new cases have been reported in recent years. Similarly, it appears to have dis­appeared completely from southeastern Australia without any specific effort at control, although following its introduc­tion, its prevalence at one time was as high as 10 percent. A more recent intro­duction in the tropics, in Ceylon, appears to have become better established. There has been a marked increase in prevalence in areas of that country where African troops were stationed during World War II. In the South Pacific, east of the 170th Meridian, including the Fiji, the Gilberts and Ellice, Samoa, Tokelau,' Tonga, Society (Tahiti), and Marquesas Islands, the so-called nonperi­odic form of W. bancrojti occurs. The biologic and epidemiologic characteristics of this form are so different from those of the periodic type of the infection which occurs elsewhere in the world that some have concluded that it is caused by a separate species. The name W. philippi­nensis was suggested by Ashburn and Craig, 1906; W. pacifica by-Manson-Bahr, 1941. There have been very few reports of overlapping of this fonn with the peri­odic fonn, but there is some indication that it was introduced into the Carolines north of the equator by migrating Poly­nesians and again early in World War II.

(2) The distribution of W. malayi is limited to the Far East, where it is found in India, Ceylon, Indonesia, Malaya, the Philippines, Indo-China, and East China (See fig. 2); it has also been reported re­cently from New ,Guinea, South Korea, and Hachijo Island in the Japanese Archipelago. There is considerable over-

lapping with the periodic form of W. bancrojti.

b. Transmi8sion. (1) The adult worms live in the lymphatic

system of man. Female worms release large numbers of sheathed microfilariae, precociously active embryos, into the lymph and blood streams. Microfilariae are incapable of development in man and, unless they are taken up by a mosquito of an appropriate species, eventually die. The microfilariae of W. bancrojti show a marked nocturnal periodicity in most endemic areas. The microfilariae of W. malayi show a similar but less pronounced nocturnal periodicity. The "nonperiodic" form of W. bancrojti in the islands of the South Pacific (see above) has no such nocturnal periodicity and, on the con­trary, may even show a slight diurnal periodicity.

(2) In the mosquito, the microfilariae taken up with a blood meal undergo two molts during a period of 6-10 days, under optimum conditions, and then migrate into the mouth parts of the vector. When this mosquito bites again, the larvae are liberated and penetrate the human skin to start a new infection. The interval which is required for the worms to become sexually mature in man and to release a new generation of microfilariae is not known with certainty, but is generally estimated to be at least 1 year. Only one adult worm can develop from each larva which penetrates the skin. A male and a female worm must develop close together before a fertile infection can result, with production of microfilariae. Microfilariae of W. bancrojti disappear from the blood stream in 6~1O years after the last in­fective exposure, indicating the time limit of the adult parasite's reproduc­tivity. This would have an important bearing on long-tenn control procedures and would be of interest in the return of infected personnel to the United States.

(3) A high prevalence of . infection in the human population and a heavy density of efficient mosquito vectors are required for the spread of filariasis. The flight range of the vector, the closeness of asso-

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Figure t. Geographical dutribution of fi-laria8i~ (Wuchereria malayi).

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ciation between exposed and infected individuals, and the presence of favorable climatic conditions for the development. of the parasite in the mosquito are other important factors in transmission. Pro­longed exposure increases the chance of acquiring the disease. It cannot be em­phasized too strongly or repeated too often that the nature of exposure is com­pletely different for periodic and nOll­

periodic filariasis. In the case of nOll­

periodic filariasis, in the South Pacific, the danger is in the daytime in natural cover frequented by the native popula­tion. In the cose of periodic filariasis, the danger is entirely at night, and is particularly great near infected popula.­tions. The nonperiodic form of W. ban­erofti is of particular concern in military operations since it is transmitted by mos­quitoes which feed almost exclusively in the daytime in the natural cover.

c. Vectors. (1) Oukz jaligaw (Oulex quinquejasciatus) is

the most common vector of the periodic form of W. bancrojti. It occurs in nearly every place where this form of the para­site occurs, and often is the only vector of importance. Complete development has been demonstrated experimentally in nearly two score other mosquito species of the genera Oulez, Aedes, Anopheles, Man-­sonia, and Psoroplwra, but most of them are unimportant in the transmission of the infection in nature. The ubiquitous Aedes aegypti has been infected, but usually in only a small percentage of those fed, and in many areas they have been completely refractory. There is no evidence that this species is responsible for disseminating the infection in nature. The important vectors seem to be con­fined to the genera Oulex and Anopheles. In addition to C. jatigans, the following are important vectors in certain localities: Ouler. pipiens and ArwpheLes hyrcanus Bi:rumms in China, Formosa, Okinawa, and- Japan; the Anopheles punctuUUus complex (A. p. pundUlaiU8, A. p. jammi, and A. p. koliensi8) in New Guinea, Celebes, Solomons, and New Hebrides; C. pipuns in India; A. gambiae and A. june8tus in Africa, and A. darlingi on the

1'AGO (1889.-\

(2)

(3)

north coast of South America. All of these are nocturnal in their feeding habits, often take human blood, readily enter human habitations to feed, and become easily adapted to breeding in waters near human dwellings. Two of them, C. jatigans and C. pipUfUI, have become highly domestic and particularly well adapted for breeding in small collections of water such as in rain barrels, eaves, tin cans, and other containers around houses. In most of the islands where the non­periodic form of W. bancrojti occurs it is primarily, if not exclusively, transmitted by Aedes polynesUnsis (Aedes pseudo-8cutellarn). In the Tonga Islands, epi­demiological evidence indicates that Aede8 tongue is the vector. These mos­quitoes feed only in the daytime and are sylvan or wild mosquitoes. The aquatic stages develop in small temporary collec­tions of water in tree holes, coconut shells, fallen banana leaves, coconut fronds, and other similar receptacles in plantations or bush covered areas. They will also develop in water in discarded cans, tires, gun shells, pieces of fuselage, and other similar water containers in areas covered by bush. They are rarely found in any collections of water in clearings. The adults have a very limited flight range, scarcely more than 100 yards, and feed almost entirely in the same naturally shaded areas. They are particularly active on rainy or overcast days, and in the early morning and late afternoon, are less active in the heat of the day, and do not feed at night or in sunlit clearings. They rarely enter houses except those encompassed by or adjacent to bush areas and apparently never rest in human habitations, even the thatched native houses. The mosquitoes known to be good inter­mediate hosts of W. malayi are Mansonia annulata, M. annuiijera, M. indiana, M. lQngipalp~, M. unijorm~ and Anopheles hyrcanu8 sinenm. The larvae of these species of Mansonia, all of the subgenus Mansonoides, develop under water ill association with certain aquatic plants, such as Pistia (water lettuce), Eichhornia (water hyacinth), and Lemna. The

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adults are night feeders, strong fliers, and \\.jJ1 readily enter human habitations to feOO, However, the peculiar require­ments for the larval stages are more commonly provided in rural than in urban areas.

4. Course. Many infections remain asympto­matic for years. The severity of the clinical manifestations appears to be related to the in­tensity of infection and the degree of allergic respo~ses. The ultimate elephantiasis apparently does not occur in transients, such as military peI'!lOnnel, whose exposure to infection, however intense, is of short duration. Even in the native populations, it occurs in varying small percentages rarely over 5 percent, and only after decades of continuous exposure. The interval from infection to the appearance of symptoms varies. During World War II experience in Samoa, the first clinical manifestations commonly occurred be­tween 3 and 6 months after exposure to infection. The symptoms and signs of filariBSis may be divided conveniently into two groups under the headings acute and chronic, or early and late. This is definitely a classification of convenience since the acute or early manifestations may recur as acute exacerbations or attacks of filarial fever throughout the chronic phase of the disellSe if the subject remains in the endemic area.

a. Acutt or Early Symptoms and Sigm. The (ollowing accoun t relates particularly to early events in the course of filariasis acquired on the islands of the southern part of the ~ntral Pacific region where the nonperiodic variety of W.

. ThS til"· bancroftt occurs. e amoan arm mumu 111

often used to designate the clinical picture in question. In less highly endemic areas elsewhere, this clinical picture is less frequently seen and may not be quite as severe.

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(1) The manifestations occur in a series of acute attacks which may last from less than a week to several weeks. Recur­rences are not periodic. I t has been observed that strenuous exercise or hard work may precipitate attacks. In the intervals, patients may appear to be in normal. health. Acute attacks vary greatly in severity, from very mild or hardly noticeable to. incapacitating. Among the symptoms are lack of energy and stamina, constant fatigue, anorexia, nausea. headache. vertigo, drowsiness,

blurring of VISion, photophobia, and muscle spasm .. Pain is common, but rarely severe. I t occurs in the chest, lower abdomen. muscles, and in associa­tion with local swellings and lymphan­gitis. Fever, chills, and prostration nrc unusual , e."tcept in mild degree. Neu­rotic symptoms are frequent and mental depressions may be severe.

(2) The physical signs are largely those of enlarged lymph nodes, other localized swellings, and lymphangitis. [nvolve­menL of the genitalia is especially fre­quent, with retrograde funiculitis, epi­didymitis, orchitill, varicocele, and edema of the scrotal skin. There is no evidence that early filariuis has any luting de1e­terious effect upon the sexual (unctioruJ. Swollen lymph nodes, which are rubbery in consistency and remain discrete, appear in the inguinal, cervical, axillary, or epitrochlear regions. Lymphangitis may develop in the arms, neck, or thighs. It procoods in a retrograde or centrifugal direction, in association with a red streak, under which the enlarged vessel may be palpable. In some instances, circum­scribed, localized areas of swelling occur in the arms or legs, which are dull red, tenlle, and edematous. Urticaria is occasionally seen. Other changes in the skin are rare. Conjunctivitis may be present. Pleural friction rubs have been heard. Anemia does not develop, except from other associated causes. A moder­ate leucocytosis is present in about one­third of the cases. Since intestinal para­sites are often present, they must be taken into account in estimating the significance of the eosinophilia. which occurs in about two-thirds of the cases. The urine shows no significant changes. The swellings which have been mentioned usually involve the genitalia and one or more extremities. They show only moderate tend~rness and ra.re1y su p­purate. All of the changes described may develop rapidly and may regress just as quickly; therefore, the clinica.l ma.nifesta­tions oCten show marked variat.ions with­in 12 to 24 houn. Repeated or prolonged attacks occasionally produce enlarge­ments or thickenings, usually oC lymph

TA.GO li889A

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nodes or genitalia (espacia.lly the sper­matic cord). whi('.h are rarely marked. but may be detectable in the intervals between acute attacks.

(3) It has been demonstrated in many acllte attacks that there is no concomitant bacterial infection. Such infections, therefore, are not necessarily an essential part. of this picture. The clinical mani­Cestations have no relation to the presence of microfilariae in the blood. Further­more, the early swellings are not due to mechanical blockage or lymph channels by adult worms. The theory that an allergic mechanism underlies the early attacks has been suggested by many observen and has much to commend it. Available inrormation is ina.dequate, how. ever, and at present it is impossible to accept this theory without reservation.

b. Chronic or lAt~ Sy1nptoms a/lid Signs. The late symptol1l8 or chronic aspects of filariasis occurred only rarely &Jld Cor only a few years in military personnel following filarial infection acquired during World War II. None have developed elephantiasis. Such conditions develop only after decades of continuous exposure to reinfection in the endemic areas. Chronic or la.te aspects of filariasis are best considered under two separate categories, filarial fever and ele­phantiasis.

(1) Filc.rialf~f#. This is not unlike the acute attack or early sumptoms and signs of filariasis. It is apparently of allergic origin. It appears to be associ­ated with increases in filarial antigen in ilie individual highly sensitized by pre­vious infection. Antigenic increases may result from new infections or dIe death of adult worms or microfilariae. The death of these parasites may be natural or induced by chemotherapy. Attacks of filarial fever may be induced by intradermal tats with filarial antigen. There is some evidence that they may also be precipitated by severe exercise. Although there is no evidence that secondary bacterial invaders play any role in early manifestations or filariasis, discu~d above, there is considerable evidence that bacteria. may be involved in some attacks of filarial fever in long standing infections. 1'he extent and the

TAOO ~89A

frequency of the bacterial involvement is not known. The attacks of filarial fever or acute exacerbations of filariasis in long standing infeetions are character­ized by chills and fever (1020 F. or more), headache, prostration, and sudden ten­derness or the femoral or inguinal and sometimes the epitrochlear lymph nodes. There may be increased swelling of the scrotum, the involved lymph nodes, and exacerbation of the lymphangitis of the arms or legs. The areas over the lymph channels may become tender. erythema­tous, and edematous. Severe mU8cula.r aches a.re common, particularly in the thighs, calves and lumbar regions or thl' back. These attacks may last from a few days to & few weeks.

(2) Hyperpl<uia and elepha1lliMi8. The more commonly recognized manifestations of the later stages of filariasis are associated with permanent ·changes in the tissues. The characterist.ic developmenw include lymph node enlargement and the condi­tion kl)own as elephantiasis. Since this condition is sometimes caused by other infections , the term "elephantiasis" should not be used as an equivalent of "filariasis." Elephan tiasis consist. of pennanent, extensive thickening and swelling of the soft tissues, with enlarge­ment of the part affected. Any pOrtiou of the body may be affected, but the genitalia and the extremities, especiaUy the legs, are most often involved, At least in part, the change is a consequence of more or less complete occlusion of the local lymphatic drainage. Some investi­gators believe tha.t secondary ba.e~ria1 infections contribute significantly to the condition. The development of late manifestations has no relation to the presence of microfilariae in the blood. It is generally believed that many years of repeated infection with fila.riasis are required for the development of ele­pharttiasis. Among natives of endemic areas who are exposed to the disease from birth, the conditi.on is usually not seen before the age of 20. It is by no means an inevitable consequence of in­fection, since only .~ percent or less of heavily infected populations may show

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it. Chylemia and chyluria are common; chylous effusions of the abdomen and even of the chest occur. Extensive abscesses may develop in the soft parts of the extremities or the wall of the trunk but their etiology is not known.

5. Diagnosis. The diagnosis of filariasis should be made not only when the presence of the disease is proved by the demonstration of microfilariae or adult worms, but also when the history and clinical findings provide sufficient evidence thereof. It is important that medical records show this diagnosis in all cases in which a reasonable basis for it exists.

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a. History and Clinical Findings: (1) The most important considerations are

outlined below. Exposure to the disease in an area where it is known to be en­demic is essential. According to expe­rience during World War II, filariasis in military personnel was acquired primar­ily by troops stationed on islands in the South Pacific. Prolonged exposure in endemic areas should be noted. In areas where periodic filariasis occurs, particular attention should be given to a history of night activities and sleeping in the open or in unscreened or unsprayed quarters. In areas where non periodic filariasis oc­curs, particular attention should be given to military or other activities during the daytime in uncleared areas, especially areas frequented by natives. The inter­val between first exposure and the first symptoms is characteristically long (3 or 4 months to 1 year or more). Recurrent attacks, with manifestations of the type described in paragraph 4a, should be given great weight.

(2) The most significant signs are character­istic lymph node enlargement, involve­ment of the genitalia and, especially, retrograde lymphangitis.

(3) The diseases which must be excluded are malaria and various bacterial infec­tions, including streptococcal and gono­coccal infections, syphilis, and tubercu­losis. Appendicitis, hydrocele, and her­nia should not be overlooked. In many cases, the diagnosis is difficult or impos­sible when acute manifestations arc absent. Experience furnishes the only reliable guides. The acute attacks that

can often be precipitated by marching and other exercise may be helpful.

b. Laboratory Stwlus. The demonstration of microfilariae or of the adult worm is the only proof of the presence of filariasis.

(1) Microfilariae were unquestionably demon­strated in only a few instances among personnel infected in the Pacific. N ever­theless, the search for them should always be made and -repeated at intervals. Microfilariae may be discovered in prep­arations of the blood or aspirated con­tents of a lymph node or hydrocele. In most of the endemic areas, they are most readily detected in blood taken at night; they may be 100 to 150 times more nu­merous between 2200 and 0200 hours than at any other time. In the case of the nonperiodic forms, in the islands of the South Pacific east of, but not including the New Hebrides, they may be slightly more numerous in the daytime, particu­larly in the afternoon, than at night. Whenever microfilariae are found, the species should be identified, preferably by a trained parasitologist. In any case, a full description should be recorded im­mediately, the preparation should be preserved, and the finding should be confirmed. In well-established infec­tions, living, active microfilariae may be detected in a drop of fresh blood, preferably mixed with one or two drops of physiological saline. The species may be identified in thin or thick blood films. It may be necessary, particularly in new infections, to use one of the concentra­tion methods. The Knott method is most commonly employed because it requires only the apparatus and solutions available in almost any installation, but the concentration may be more quickly and effectively accomplished if saponin and a centrifuge are available. For the Knott method: Withdraw 1 cc of blood from a vein and discharge into 10 cc of a 2 percent formalin solution in a 15 cc conical tip centrifuge tube. Thoroughly mix and set aside to sediment for 12 to 24 hours. Decant the supernatant fluid and, with a capillary pipette containing a small amount of water, remove the sediment and make an even, fairly thin

TAGO 11889A

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smear on a glass slide. When dry, stain with Loeffler's methylene blue for 2 or more minutes, rinse free of excess stain, and when dry, counterstain for 1 to 2 minutes with ~ percent aqueous solution of eosin. Giemsa stain may also be used. In the formalized sediment the microfilariae lie stretched out and not in the graceful curves seen in thin and thick blood smears. Since the microfilariae measure about 300 microns in length, they are easily visible under the low power of the microscope. In the saponin method, 1 to 10 cc of freshly drawn blood is lysed by frequent agitations over a 20 to 30 minute period in 4 to 5 volumes of a freshly made 2 percent saponin solu­tion. After lysis, the mixture is centri­fuged and the sediment examined either directly or after staining. One distinct advantage of this method is that the microfilariae remain alive and active so that they can be detected easily in the unstained sediment.

(2) Adult worms were demonstrated in about 30 percent of the Pacific cases during World War II in which biopsies of lymph nodes were studied. These gave sub­stantial verification of the general reli­ability of these diagnoses. However, biopsies are not recommended as a routine diagnostic procedure. Excision of lymph nodes or other tissue while acute symptoms are present is sometimes followed by severe exacerbation, and might lead to more serious consequences. In the complete absence of acute mani· festations and under expert guidance, a lymph node may be removed for study. The removal of other tissue is undesir­able at any time. The selected node should be at least moderately enlarged, firm, and free from adhesions. The op­erative technique and post~perative dressing should be in accordance with ths best surgical practice. Patients should be kept in bed for at least 5 days. The preparation and study of sections should be done by a trained pathologist. The findings should be fully recorded and the slides should be carefully labeled and preserved. Sometimes in long-estab­lished infections, the presence of adult

'rAGO 1188DA

wonns may be inferred when wirelike calcifications in the lymphatic system can be demonstrated by roentgeno­grams.

(3) Other laboratory studies are helpful only in connootion with clinical findings. Leucocytosis and eosinophilia may be present but are not specific. Skin tests and complement fixation tests have been used. The antigen usually employed is derived from Dirofilaria immitis, a re­lated species, which occurs in dogs. These tests are not strictly specific and the technique has not been thoroughly standardized. For the skin test, it is important that such antigens be used in very dilute form (1:8000 is recommend­ed) and that adequate controls be con­ducted. The possibility of cross reaction with intestinal nematodes should be con­sidered. The results of these tests may be helpful in conjunction with other find­ings, espooially in groups of patients, but they require critical evaluation. To a certain ~xtent, the microscopic pathology of tissues acutely involved in the early stages of the disease is suggestive, but this fact cannot be applied in routine diagnostic studies.

6. Treatment. a. General Measures. Patients should be kept in bed during acute attacks. Cold compresses should be applied over local inflamed areas. When edema appears, the part should be elevated. A specially devised scrotal support is necessary if the scrotum is enlarged. X-ray radiation of acute filarial lymphangitis or adenitis is of doubtful value and may be harmful. All surgical operations are undesirable during the acute manifestations except those clearly indicated as emergency measures. The treatment of ele­phantiasis will not be discussed herein.

h. Chemotherapy. Attacks of filarial fever, in long standing infections, may be relieved by anti­biotic therapy, preferably penicillin. Antihista­minics have been tried with, apparently, only slight success. Specific therapy does not im­mediately relieve an attack of filarial fever; indeed, it may even induce an attack.

(1) Of the drugs available, only thiacetars­amide (Caparsolate sodium), an arseni­cal, appears to kill the adult worms regularly. The drug must be givE'n intra-

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venously. A dose of 1.0 mg. per kilogram of body weight per day for 15 days is recommended. This is packaged in ampules as a 1 percent solution, hence, the dose is 1.0 cc per 10 kilograms body weight. The drug is sclerosing and peri­vascular leakage should be avoided. If this occurs, the immediate application of ice packs will give relief and may prevent sloughing. Injection of this drug occa­sionally causes diarrhea which may be prevented by giving ascorbic acid. It is, therefore, recommended that 50 mg. of ascorbic acid q. i. d. be given orally. Thiacetarsamide acts primarily against adult wonns and secondarily, and more slowly, upon the microfilariae. Micro­filariae may still be present on the com­pletion of the 15-day course of treatment, but they continue to disappear there­after; a recurrence is unusual.

(2) Diethylcarbamazine (Hetrazan, Banocide, Notezine), one of the piperazines, is primarily microfilaricidal. Eighty to 100 percent of the microfilariae may be killed within 24 hours. The sudden destruction of numerous microfilariae is apt to pro­duce reactions in the patient. These will vary in degree and may consist of fever, chills, headache, muscular aches, and occasional dizziness. The maximal effect usually ends by the 24th hour, and the reaction usually ends by the 72nd hour. Within several days localized abcesses may develop in a small number of cases. Patients respond to group reassurance, particularly, if forewarned that the reac­tions indicate the death of parasites. This drug cannot be depended upon to kill the adult wonns, even after continued administration, and the microfilariae return in less than a year. Diethylcar­bamazine is the only antifilarial agent which is administered orally; it is com­paratively nontoxic. The recommended dose is 2.0 mg. per kilogram body weight t. i. d. for 21 to 30 days.

(3) Antimony compounds, which have been used in the treatment of filariasis for three decades, can TlO longer be recom­mended. Such compounds are quite toxic. The trivalent antimony com­pounds are primarily microfilaricidal.

Both the trivalent and pentavalent com­pounds appear to sterilize the females rather than kill them.

c. Psyclwlcgical Management. Patients with filariasis may suffer greatly from worry over the possible outcome of the disease and fear of trans­mitting it to their families or others. These wor­ries and fears are due to lack of knowledge of the disease, observation of cases of elephantiasis among the natives, and involvement of the geni­talia. Throughout the treatment the medical officer should bear in mind the great importance of gaining the patient's confidence and of explain­ing to him in ordinary language the elementary facts concerning the transmission, nature, and course of filariasis. It is desirable to reassure patients and to explain to them that, although they may have further transient attacks, the chance of serious permanent damage is negligible.

d. Convak8cence. Patients should slowly re­sume normal activities following acute attacks. They should not be kept in bed nor in a regular hospital ward any longer than is necessitated by the occurrence of symptoms. As soon as possible they should enter a reconditioning program which should be modified, if necessary, to suit their needs. Careful supervision and proper psycholog­ical management, with due attention to morale building, are essential.

7. Prognosis. Filariasis itself presents no signif­icant threat to life. In the great majority of in­stances the signs which develop during the early stages are entirely transient. Experience indi­cates that as time goes on remissions lengthen and recurrences become milder. Many persons with the diagnosis of filariasis, in the absence of symp­toms, have demonstrated their ability to perform military duties satisfactorily. The risk of the de­velopment of pennanent lesions, including ele­phantiasis, is not known in statistical terms. In view of the low incidence among heavily infected natives of endemic areas, this risk is negligible for individuals who have not had long exposure to repeated heavy infections if further exposure is prevented.

8. Disposition. The disposition of patients with filariasis should be determined by the severity of the clinical manifestations, by the history of exposure, and by consideration of how critical is the need for personnel. Patients should be hos­pitalized until they are free from symptoms and clinical signs. They may be returned to duty

TAGO :;S89A

after a reasonable period of freedom from clinical 'manifestations and suitable reconditioning. This period is estimated t.o average about 3 months. The presence of microfilariae in the blood alone is not a basis for prolongation of hospitalization or other restriction. Where the need for personnel is critical, mild cases with possible exposure of a year or less may be kept in an endemic area. More severe cases can be transferred to nonendemic areas overseas. Only critical cases need to be evacuated to the United States. From past expe­rience it is apparent that a general policy of evacu­ation back to the United States produces two un­desirable effects. It operates against any attempt to reassure troops that filariasis cannot seriously endanger them, and since many of the symptoms of early, acute filariasis are nonspecific and can be feigned, it provides a method for getting evacuated in medical channels. This tends to remove sea­soned men from areas of requirement and even encourages exposure to gain that end. Where the need for personnel is not critical, it is recommended that individuals in whom the diagnosis was estab­lished be removed to a nonendemic area for treat­ment and future duty assignments.

9. Prevention. a. General. The prevention of filariasis depends entirely upon preventing infected mosquitoes from feeding on personnel. Such pre­vention may be conveniently summarized undcr three main headings; vector control, group pro­tective measures, and individual protective meas­ures. The methods put into practice will vary somewhat, depending on whether the personnel involved are under combat conditions or in per­manent installations, and with the fundamental differences in the epidemiologic factors active in transmission under the locally existing conditions. Differences between the periodic and nonperiodic forms of W. banerofti and the more subtle devia­tions of W. malayi should be remembered.

b. Vector Control. I t will be noted below that most of the methods suggested for vector control are, of necessity, predicated on more or less sta­bilized conditions. All unnecessary natural and artificial water collections within the area should be eliminated to prevent local breeding of the vectors of W. bancrofti, either periodic or non­periodic. This should include continuous policing of the area for such water receptacles as cans, tires, bottles, coconut husks, abandoned vehicles or other objects which may hold water. In areas where the periodic form of W. bancrofti occurs,

TAGO 1i8811A

the elimination of such water containers should be extended to nearby native villages or cities. Necessary impoundments should be kept free of vegetation and checked for mosquito larvae. If indicated, larviciding should be practiced. In areas whe.re the periodic form occurs, the application of residual sprays in both military and native dwellings will contribute significantly to mosquito destruction. In the South Pacific where nonperiodic filariasis occurs, such household spray­ing may be less effective and give a false sense of security. It may be impossible to eliminate all water collections utilized by the vectors of this form in the uncleared areas. Recourse may be had in such areas to low altitude aerial spraying with an insecticide. Such aerial spraying will not reach the protected breeding sites but ,,,ill kill adult mosquitoes. It should be repeated at intervals of 2 to 3 weeks to eliminate broods as they appear. Aerial spraying is less likely to be indicated for the control of the vectors of lV. malayi or the periodic form of W. banerofti. For the control of the vectors of W. malayi, herbicides should be applied to all waters in which such plants as Pistia grow, since they serve as the hosts for the larvae of these mosquitoes. Residual insecticides applied in both military quarters and native houses will yield benefits.

c. Group Protective Measure8. (1) In general, camp sitl's should be at least

a mile from concentrations of native pop­ulations, since they constitute the reservoir from which mosquitoes are infected. Local conditions and the type of parasite involved may make a modification of this generalization desirable or necessary. Since the nonperiodic type of W. ban­crojti is transmitted during the daytime where natural cover is provided by dense vegetation, camp sites should be kept free of undergrowth. In areas where this form is present, and it is necessary for personnel to go into un­cleared terrain, they should be in­structed in the techniques of personal protection. The vectors of this para­site have a very short flight range, scarcely over 100 yards. To a limited degree they may venture into clearings on heavily overcast days. Since both W. malayi and the periodic form of W. bancrofti are transmitted at night, appro­priate precautions should be taken.

11

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The vectors of the former are frequently most plentiful some distance away from human habitations but they are strong fliers and enter houses readily. The vectors of the latter are usually highly domestic. For this reason, every effort should bemade to protect living quarters, mess halls and recreation facilities. Such quarters should be screened when possible and bed nets should be provided. Re­sidual insecticides, such as DDT, should be used and space sprays (aerosols) are valuable. Unprotected buildings out­side the area should be placed off limits at night. Bed nets should be provided for personnel sleeping in the field and in­structions in personal protection should be given.

(2) Consideration has heen given to the possible value of community-wide treat­ment of native populations to reduce the reservoir of infection for mosquitoes. While this has not as yet been demon­strated to be of value, it would be well to consider the possibility of using diethylcarbamazine as an antimicrofi-

larial drug to · reduce or eliminate in­fectivity of labor forces that may be in rather close association with troops. The decision to use this control measure would depend on a knowledge of the epidemiologic characteristics of the dis· ease and local conditions. If this method is used it would be in conjunction with other control measures.

d. Individual Protective Measures. Personal antimosquito measures, as applied against malaria vectors, will also afford some protection against the common vectors of W. malayi and the periodic type of W. bancrojti. Insect repellent and mos­quito bars should be used routinely. Long­sleeved shirts and full-length trousers should be worn at all times, particularly in the evening until retiring under the protection of bed nets. In areas where troops are exposed to the non­periodic type of W. bancrofti, transmitted by day-biting mosquitoes, particular emphasis should be placed on protective clothing and repeated application of repellent during the day. Under combat conditions, insect repellent and protective clothing offer the most practical means of pre­venting infection.

TAGO :i889A

)

By ORDER OF THE SECRETARIES OF THE ARMY, THE NAVY, AND THE AIR FORCE:

OFFICIAL:

JOHN A. KLEIK, Major General, United States Army,

The Adjutant General.

OFFICIAL:

G. L. RUSSELL, Vice Admiral, United Statts Navy,

Deputy Chiej oj Naval Operations (Administratwn).

OFFICIAL:

E. E. TORO, Oolonel, United States A ir Force,

Air Adjutant General.

DISTRIBUTION:

Activ~ Ar7rlV: CNGB (1) Tee Sve, DA (1)

FA Bn (2) Inr Bn (2) Med Bn (2) QM Bn (2) Armd Bn (2)

MAXWELL D. TAYLOR, General, United State~ Army,

Chief of Staff.

B. W. HOGAN, Chiej, Bureau oj Medicine and Surgery,

Department oj the Navy.

N. F. TWINING, Ohief of Staff, United State8 Air Force.

RTC (2) Pers Cen (4) Trans Terminal Comd (2) POE (OS) (2)

Hq CON ARC (6) Army AA Comd (2) OS Maj Comd (6) OS Baae Comd (4) Log Comd (4) MDW (1)

Med Co (2) except TOE B-U7R Army Terminals (2) Disp (2)

Armies (8) COrptl (3) Div (3) Brig (2) Regt (3) Engr Bn (2)

(8) Ft &; Cp (4) USMA (2) Gen &: Br Sve Seh (4) Gen Depote (2) Med See, Gen Depots (2) Med Depot8 (2) AH (6)

Med Lab (4) Mil Dist (1) MAAG (2) Mil Msn (2) ARMA (2) Unit8 organized under following

TOE's: B-500R (AA-AH), Med Svc Org (4)

NG: State AG (6); units----llame !\lI Active Army except allowance is one copy to each unit. USAR: None. For explanation of abbreviations used, see SR 320-50-1. Air FQTC~: X.

Heaclquartere USAF _ _ __ _ _ _ _ _ __ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ __ _ _ _ _ _ _ _ _ _ __ _ __ _ _ _ __ _ _ _ _ _ _ _ _ _ _ __ _ __ _ _ _ _ _ _ __ _ _ 250 Major air commands (Attn: Staff Surgeon)________________________________________________________ 1 Subordinate air commands (Attn: Staff Surgeon)___________________________________________________ 1 Air divisions (Attn: Staff Surgeon) _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 1 Wings (Attn: Staff Surgeon) __________________________ . _________________________________________ _ Bases (Attn: Staff Surgeon) ____________________________________________________________________ _ Hospitals_ _ ____ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 1

TAGO 11889A 13

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