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Chapter 278 - TrssuE NEMAToDES (TRtcHrNosts, DRAcuNcuLtAsts, FtLARtAsts)

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2943

that can be given in a dose of 25 mgkg twice a day for 2(maximum of 3 g/day).s Albendazole, although currently not

by the Food and Drug Administration for this purpose,also be used at a dose of 200 p"gkglday for 1 t9 2 days. In therinfection syndrome, early diagnosis and treatment for 2 to 3

may be lifesaving, but the mortality is very high despitePatients with a past history of exposure to S. stercoralis

be thoroughly examined and treated before undergoing any Tissue Nematodes (Trichinosis,Dracunculiasis, Filariasis)

DAVID I, GROVE

1. Bundy DAP, Cooper ES. Trichudmis. In: Wmen KS, Mahmoud AAF, eds. Tropical' and Geographical Medicine. Znd ed. New York: McGraw-Hill; 1990:399-404.

people infected with S. stercoralis should be treated with the aimeradicating the infection. Thiabendazole (Mintezol) is an effective

EFERENCES

Ramdath DD, Simeon DT, Wong MS, Granthm-McGregor SM. Iron status ofschml children with varying intensities of Trichuris trichirra infection. Parasitology.1995:1 10:347-35 1.

i. Gilman RH, Chong tItI, Davis C, et al. The adverse consequences of heavy: Trichuris infection. Trans R Soc Trop Med Hyg.1983;77:432438.4. Booth M, Bundy DA, Albonico M, et al. Associations among multiple geohelminth' species infctions in school children from Pemba Islmd. Paasitology. 1998;116:85-' 93.

.15. Drugs for Pmitic Infections. Med lf,tt Drug Ther. 1998;40:l-8.6. Pawlowski, ZS. Enterobiasis. In: Pawlowski ZS, ed. Clinical Tropical Medicine md

t:10. DeSilva lr{R, Chan MS, Bundy DA. Morbidity md inortality due to ascariasis:i-i, F-eestimation and sensitivity analysis of global nurnbers a-t r'isk. Trop Med IDt

He:.itl:. : )9'l l:5 19-528.

11!. K-huroo ,q?55. Asctriasis. Gastroenterol Clin Norri Am- 199$;25:553-5'.17.

,. 12. Crmpton DWT. Nesheim MC. Pawlowski ZS. eds. Ascriasis and lts Public Heafuh

l:,'r'' Significmce. London: Taylor and Francis; 1985.

fi!3. Sinniah B. Daily egg production of Ascaris lumbicoides: The distribution of eggs

fi, , in ttre feces and the vaiability of egg counts. Parasitology. 1982;84:167.?t14. Anderson TJ. ,4rcarm infections in humms from North America: Molecular evidence

f.. for.ross infection. Partritology. lgg5:110:2L5-21,9.

f*S. C"tpi AP, Mustafa A. Ascariipneumonia. Am f Med. L968:44:377.

t'16 Strephenson LS. The contribution of Ascais lumbricoides to malnutrition in chil-i.:,i .. dren. Prasitology. 1980:81:221-233.fl:17, Blumenthal DS, Schults MG. Effects of Ascaris infection on nutritioml status inir-. children. Am J Trop Med Hyg. 1976;25:682.

f:1&. Blumenthal DS, Schultz MG. Incidence of inrestinal obstruction in children infmted$:r. with Ascaris lumbricoides. Am J Trop Med Hyg. 1974;24:801.

!':19. WasaOitar PP, Kulkami AB. tntestinal obstruction due to asctriasis. Br J Surg.

F,. 1997:84:410412.

5120. Desilva NR, Guyatr ItL, Bundy DA- Morbidity atrd mortality due ro Ascaris-!-:.i.. induced intestinal obstruction. Trans R Soc Trop Med Hyg. 1997;91:31-36.

].,21, Sanaout fl Haffar S, Zada M, et al. Pancreatic-Lifiary asiriasis: Experience of 300$.,' cases. Am J Gasfioenterol. 1997:92:2261-2267.

!22. eti M, Khan AN. Sonography of heparobitiary ascariasis. J Clin Ultrasound.?.. 1996:24:235-241.

:23, Guyatt HL, Chan MS, Medley GF, Bundy DA. Control of Ascaris infection by

$!' chemotherapy: Which is the most cost-effective option? Trans R Soc Trop Med::. Uyg 1995;89:16-20.

!:24. Schad GA, Banwell JG. Hookwoms. In: Wanen KS, Mahmoud AAfl eds. Tropical1 and Geographical Medicine. Znd ed. New York: McGraw-Hill; 1990;379-393.

1!5. Prociv P, Croese J. Human enteric infection with Arcylostoma caninum: hookwomsf-.: reappraised in the light of a "new" zoonosis. Acta Tropica. 1996.62:2344.!:126. Stoltzfus RJ, Albonico M, Chawaya HM, et al. Hemoquant detemination of hook-

i..l. worm-related blood loss and its role in iron deficiency in Africm children. Am J

il 'Irop Med Hyg. 1996;55:399-404.f,.:!?. Mahmoud AAF. Strongyloi<liasis. Clin Infect Dis. 1996:23:949-952.ii.28. Grove DI. Human strongyloidiasis. Adv Puasitol. i996;38:251-309.

1:29. Wehner JH, Kirsch CM. Pulmonary manifestations of strongyloidimis. Semin Respir+,: lofect. 1997:12:122-l?9.

|.30. Heyworth MF. Ptrasitic diseases in imunocompromised hosts. Cryptosporidiosis,!.,. isosporiasis md strongyloidiasis. Gastroenterol Clin ttorttr Am. 1996;25.69\-701.f,;'31. Gompels MM, Todd J, Peters BS, et al. Disseminated strongyloidiasis in AIDS:!1, Uncommon but important. AIDS. 1991;5:329.:.:32. Sato Y, Kobayashi J, Tona H, Shiloma Y Efficacy of stool exmination for detection

i.', of strongyloides infection. Am J Trop Med Hyg. 1995'53:248-250.

33. Sato Y, Kobayashi J, Shiroma Y Serodiagnosis of strongyloidiasis. The application

and significance. Rev Inst Med Crop Sao Paulo. 1995;37:35-41.34. Ramachandran S, Thompson RW, Gam AA, Neva FA. Recombinmt cDNA clones

for immunodiagnosis of strongyloidiilis. J Infoct Dis. 1998l,177:196-203.

The tissue-dwelling roundworms constitute a major global healthproblem. They are widely scattered around the world, especially inthe tropics, and infect millions of people. Some are parasites ofhumans only, whereas others have an animal reservoir. All theseparasites have complex Iife cycles involving artfuopod intermediatehosts except for Trichinella spiralis, which is transmitted directlyfrom one host to the next by ingestion of infective larvae. Like mosthelminths, the adult woffns do not multiply within the human host;therefore, the worm load and severity of disease depend in largemeasure on the intensity and frequency of exposure to the infectiveforms. The relative pathogenicity of the adult wonns versus thelarval forms varies according to the species of infecting worm.Definitive diagnosis requires isolation and identification of the para-site. but in some infections this may be difficult. Eft'ective therapyis available for only some of these infections. Some parasites presentalmost insurmountable control prciblerns, but others can be avoidedby simple preventive measures. infections acquired by ingestion ofcontaminated food or water are considered first, and then thosetransmitted by blood-sucking flies are discussed. Historical informa-tion concerning all of these parasites, including the circumstances oftheir discovery and elucidation of their life cycles, together with theclinical illness they cause as well as modes of treatment that havebeen developed may be found elsewhere.t

TRICHINOSIS

Trichinosis develops when undercooked flesh contaminated withinfective larvae of Trichinella spp. is eaten. Most infections areasymptomatic, but heavy exposure may lead to diarrhrila, periorbitaledema, myositis, fever, and prostration.

T. spiralis is the species that has been recognized for years, butthe genus has been revised taxonomically. Five species have nowbeen described on the basis of genetic, biochemical, and biologicdata (Table 278-l). In addition, tlree other phenotypes are acknowl-edged in the genus, but their taxonomic level is uncertain atpresent.2'l

Lo,,-, 278- 1 Species within the Genus Trichinetta

Species Name Code Distribution Common Hosts

T. spiralisT. nalivaT. britoviT. pseudospiralis

T. nelsoni

TIT2T3T4T5T6wT8

Worldwide Pigs, rats, horses, bears, foxesArctic, subtrctic Bears, horsesTemperate, subarctic Bou, horses, foxesArctic, Tasmania Birds, omivorous mamalsTemperate,subarctic BearsSubarctic BemsSouthem Africa HyenasTropical Africa Lions, panthers

2944 Part lll - rNFEcrous DrsEAsEs AND THE|R ETroLoGrc AGENTS

Life Cycle

YPl rqy or inadequately cooked meat conraining viable larvae ofTrichinella spp. is eaten, the organisms are freed f6m the cyst wallsby acid-pepsin digestion in the stomach and pass into the smallintestine. Larvae invade the columnar epithelium at the bases of thevilli of the small intestine and then develop into adult worms. Theseare obligate intracellular parasites occupying the cytoplasm of a rowof enterocytes. The males are about t.j X O.OS mm and the females3.5 X 0.06 mm in size. The number of larvae released bv a fertilizedfemale-varies with the species of both parasite and hosi. T. spiralisprobably produces about 500 larvae over a period of 2 weeks andthen the fertilized female is expelled in th-e feces. The newbornIarvae seed the skeletal muscles via the blood stream. They burrowinto individuat muscle fibers and then over the next 3 weeki increase10 times in length, coil, and become capable of infecting a new host.A cyst wall develops around the larva and may eventually calcify.Larvae may remain viable for several vears.

Epidemiology

Trichinella spp. are distributed throughout the world and are widelyspread in nature among a large number of camivorous animalilo^**. being an incidental host (see Table 27g_l). Most humaninfections are due to T. spiralis; a few are due to Trichinella britovi,Trichinella nativa, and Trichinella nelsoni. Only one case of humaninfection with Trichinella pseudospiralis has bien reported.a Z spi_ralis is the only species with good infectivity for swinL and rats. Formost of_the other species, the different reservoir hosts reflect primar-l! jhe fauna present in the region. The vast majority of swini in theUnited States are fed with grain and are geneial-ly uninfected. Thesmal!, proportion fee o,lth g*rhage rray ,ba.;+l.lir ;nitrctecl when giveruncooked trichinous ;cn,.rps. usuali) pig nr*rt. ,-:r ,.r,iren the carc"assesof infected wild animals s*ch as.ratJ.are e&t€n; In Europe, the fox isthe primary reservcir.of the sylvatic cycle of Trichineia and humaninfections usually oicur in rural areas where.traditional swine-rearingpractices are used.s

Fewer than 100 human cases are usually reported each year in theUnited States. About three quarters of these are due to inadequatelyprocessed pork; most of the rest have been due to ingestion of poorlycooked bear meat, walrus meat, or cougar jerky.6,? Some epiOiemlcsin Europe have followed the consumption of lnfected horie meat8and in^ Caaada the ingestion of wild boar meat.e Epidemics occurwhen families or small communities consume trichinous meat froma common source.

Pathologic Char:acteristics

There have been indications that the various species have differentpathogenicities for humans and other hosts., Foi example, trichinosisin the Inuit population in Canada after ingestion of infected walrusseems to be associated with prolonged diarrhea and few musclesymptoms. T nativa produces primarily an enteral illness, whereasT. britovi causes few if any intestinal symptoms. T nelsoni is ofrelatively low pathogenicity in both its enteral and parenteral phases.3

_ During the first 2 to 3 weeks after infection, the small intestineshows a mild, partial villous atrophy and an inflammatory infiltrateof polymorphs, eosinophils, lymphocytes, and macrophages in themucosa and submucosa. Adult worms may be seen in the epitheliallayer near the bases ofthe vilii. The most ,t itirg changes are in theskeletal muscles. The fibers become edematoui, lose their cross_striations, undergo basophilic degeneration, and their nuclei prolifer-ate. The typical coiled worm, the cyst wall derived from the hostcell, and the surrounding lymphocytic and eosinophilic infiltrate maybe seen within the muscle fiber. In severe cases, focal interstitialmyocarditis, meningitis, and encephalitis may occur.

Most infections are subclinical. The development of symptomspends mainly on the size of the inoculu- of ,iubl" larvie. Coquently, the frequencies of the symptoms and signs of trivary widely from outbreak to outbriak. Their relative frer

Clinical Features

are shown in Table 278-2.

appear during the second week after infection. Fever is

Diagnosis

Antibodies are not detectable until at least 3 weeks after

Symptoms or Sign Mean Range

FeverMyalgiaWeakness and malaisePeriorbital edemaHeadacheCutaneous rashTrunk md limb edemaDianheaNauseaSubconjunctival hemonhagesSubungual splinter hemorrhagesCoughVorniting

Symptoms attributable to adult worms in the intestines may,found during the first week after infection. Diarrhea is the i:9t rmol slmptom, but patients may also complain of abdordiscomfort and-vomiting. patients with extremely heavy wormdens may develop a fulminant enteritis. Symptoms associatedsystemic invasion by larvae are much more-common and us

present, although it is of variable intensify and duration. perio;edema may be associated with subconjunctival hemorrhageschemosis. Myositis with pain, swelling, and weakness is alsomon; it usually develops f,rst in the extraocular muscles andinvolves the masseters, neck muscles; limb flexors, and lumbar

:l"tj.y. patients may complain of headache,-co"gh, ,h;;;;;breath, hoarseness, and dysphagia. Occasionaliy, irash that mbe macular or petechial is observed. Retinal oi subungualhemorrhages are sometimes seen. These systemic symptomspeak 2 to 3 weeks after infection and then slowly subside, a

11lld* and weakness may persist for weeks. Occasionally, adies, usually_from myo"arditis but sometime, f.o*

"""Jpfrufitii,pneumonia. It has been claimed that there may be longJastisequelae of infection including muscle aches, eye'disturbanles,diac complaints, and headaches.lo

P,"V.*lV be measured by a variety of techniques including e1linked, immunofluorescent, indirect hemaggiutinin, pr".ipitibentonite flocculation assays. A rising titei may help estdiagnosis.3 Tests for detection of Tiichinella bNA in ,

blood- using the polymerase chain reaction are being devel,The skin test for Trichinella remains positive for yea:rs aftersure; therefore, it does not differentiate between past andinfections. Muscle biopsy is usually unnecessary; if doubt rr

TA I L E 2 7 I -2 Frequencies oi Symptoms and Signs of TrichinosisCondensed from Nine Reported Ouibreaks

918982775220t81615

9963

(71-100)(68-100)(50-94)(29-1oo)(0-100)(v67)(o-75)(M8)(u67)(0-6s)(M0)(M0)(0-13)

s!.

;i:: Chapter 278 - TtssuE NEMAToDEs (TRrcHtNosts, DRAcuNcuLtASts, FtLARtAsts) 2g4Sait,

-- a sample taken from a tender swollen muscie may confirm the of about I year, and the influence of climate on the types of water:t ..L olagnosrs' sources used. The disability resulting from infection may be off... The protean manifestations of trichinosis require differentiation great economic importance if tne tinring of clinical manifestationsi. of this int'ection from a large number of other diseases. The gastroin- coincides with a busy period of the agrlcultural year and causes af;testina symptoms may mimic those of gastroenteritis. Systemic significantlossof timeinschoolforchildren.rs,r6$., symptoms may cause confusion with influenza, typhoid fever, sinusi-f- tis, dermatomyositis, glomerulonephritis, and angioneurotic edema.

f;. The rash may resemble that found in measles, scarlet fever, and ty- Clinical Features; Phus':''ti;. There are often no clinical signs until the worm reaches the surface:-:' and is ready to discharge larvae. A stinging papule develops at thisfl Treatment point, usually on the lower portions of the legs. At this time, some

F-..;,tt"." is no satisfactory treatment for trichinosis. In the rare case patients may have a generalized reaction with urticaria, nausea,

$1 tfrut u patient is known to have ingested trictrinous me"t ;ithi;"; vomiting, diarrhea, and dyspnea' Over the next few days the lesion

?::week oi so, thiabendazole should be administereA n * o.uf Jo." oi vesiculates, and then the blister ruptures and forms a painful ulcer

{::,25 mglkglday for 1 week. This drug is active against int"rtlrui within which part of the worm is often visible. If the area is douched

$,"Worms Uut tris little effect on muscle larvae and has"not b";,h;;; with fluid, a milky fluid containing larvae wells up. Discharge contin-

*:,,: to alter the course of the disease in established Uf""tion* rt " ues intermittently, and the worm is slowly absorbed or extruded over

! mainstays of treatment are bed rest and salicylates. Corticosteroid, ft" next few weeks, after which the ulcer heals. Multiple ulcers are

;,.may be used for critically ill patients, but the evidence for benefit is cornmon, and secondary infection is frequent. In endemic areas,"-equivocal. It was claimed that mebendazole was "}f*,i"" *fr* patients are often bedridden for a month or so. Immunity to reinfec-

*-gir"n 5 months after the onset of infection;r2 tr,i, ,".o"t.ou"a, .ingi" tion does not develop.

!, case report must be viewed with some skepticism. Albendazole lias: been compared with a combination of thiabendazole and flubenda-!., zole, and a marginal benefit was claimed ror aruenaarG ;;;;";;. Diagnosis

'' no untreated control group was-a-vailable for comparison'r3.A..subse- The clinical picture is characteristic. Larvae can be found on micro-:- quent study suggested that the efficacy of thiabendazole and albenda- ,"opi" examination of the discharge fluid.j: zole is similar but that albendazole is better tolerated.Ia Albendazoleir,.. may be given in a dose of 400 mg/day for 5 days.

The most effective method of: i{tiilng 'ttichineli.a {arr,ae is iry propercooking: the thermal death p*int is 55'C, so.i:rreat,sh'..rr"rkl trr *rioked.uutil there is no trace of prtk firtiei or .fiestr" Star.irge in ra'homelfreezer (-15'C) for 3 weeks usually sterilizes meat, but smoking,salting, and drying are unreliable.

DRACUNCULIASIS

Dracunculiasis (dracontiasis, guinea worm infection) develops afterdrinking water containing crustaceans infected with Dracunculusmedinensis. It is characterized by a chronic cutaneous ulcer fromwhich the worm protrudes.

When water containing infected copepods is drunk, laryae are re-leased in the host stomach, pass into the small intestine, penetratethe mucosa, and reach the retroperitoneum, where they miture andmate. The female worm (1 to 2 mm in diameter and up to 1 m long)migrates to the subcutaneous tissue, usually of the legs, about I yearlater. The overlying skin ulcerates, and a portion of the worm pro-trudes. On contact with water, large numbers of larvae are releasedfrom a loop of uterus prolapsed through either the mouth or a rupturein the body wall. These are in turn ingested by crustaceani, inwhich they undergo further development whereby the life cycle iscontinued.

Epidemiology

D. medinensis is now found mostly in tropical Africa. Shallowponds, cisterns, and wells are the usual habitat of the crustaceanintermediate hosts. The disease is prevalent in areas where peoplebathe or wade in water used for drinking purposes. Manifesiationsin a community are markedly seasonal. Thii reflects both the devel-opmental cycle of the parasite, which requires an incubation period

Treatment

Thiabendazole, 25 mglkg twice daily for 2 days,'and metronidazole,5 mglkg twice dai.ly,,for.l .week, have no.eifect on the wormsthemselves but plcd'rrcr-:.ltesr;l-rtion.of,,infanx**.iion within severaldays. This perrnil.s eas,v lrri'noval ol the E,,)nir rrircr a woek or sc byprogressively rolling out the emerging worm onto a small stick.Corticosteroid ointments shorten the time to complete healing, andthe addition of topical antibiotics reduces the risk of secondarybacterial infection.rT

Ivermectin has no effect on prepatent guinea worms.lE Mebenda-zole in high dosage is not recommended, because it does not lessenthe duration of disease or disability but increases the incidence ofnonemerged worms, thus exacerbating the danger of release of larvaeinto joints.te Alternatively, unerupted wonns may be removed com-pletely and painlessly in several minutes by surgical means withlocal anesthesia.2O Secondary bacterial infection should be treated asnecessary.

Prevention

Guinea worm infection can be prevented by boiling or chlorinatingdrinking water or by sieving it through a cloth. Control on a publichealth scale requires health education and improved water supplies.In 1986, the World Health Organization initiated a program to eradi-cate dracunculiasis by 1995. Strategies include documentation of theextent of the disease as a national problem, demonstration that it canbe prevented by targeted provision of protected rural water supplies,mobilization of community participation and political support, andthen implementation of interventions nationwide.

Although success has not yet been achieved, dramatic progresshas been made. The number of cases has fallen from an estimated 4million in 1981 to 150,000 in 1996, 120,000 of whom were in theSudan, where civil war was raging. Infection has been eradicatedfrom Kenya and Pakistan, and only nine cases were reported in 1996in India, once the home of countless cases of dracunculiasis. Guineaworm disease may soon become the second human infection to beeradicated.2i

2946 Part lll - rNFEcrous DrsEAsEs AND THEIR ETroLoGrc AGENTS

BANCROFTIAN AND BRUGIAN FILARIASIS

Bancroftian filariasis and brugian (Malayan) firariasis are similarclinical conditions resulting from the trinsmission of wuchereriabancrofti, Brugia malayi, and Brugia timori tq humans by mosqui_to^es. Symptomatic patients have acute lymphatic inflammaiion or'theeffects of chronic lymphatic obstruction suih as hydrocele, elephanti-asis of the limbs, and chyluria.

Life Cycle

After the bite of an infected mosquito, infective larvae pass into thelymphatics and lymph nodes, whire they mature over the next fewmonths into white, threadlike adult worns, the males being about 40X 0.1 mm and the females 100 X 0.25 mm in size. The idults livefor 5 years or more, and the fertilized females discharge microf,lariaeapproximately 150 X 7 pm in size via the lymphatici into ttre ttooastream. The number of microfilariae found in the peripheral bloodvaries. There is usually a surge of microfilariad- into the bloodduring the middle of the night, i phenomenon known u, iori*otperiodicity- Patipnts from the south pacific with w bancrofti infec-tion have a- much less pronounced peak that is maximal dirring thed1y. B, malayi infections produce nocturnal peaks of varying iiten_sity. If microfilariae are ingested by a mosquito during feedlng, theorganisms develop into infective larvae over the next 2 weeki andare ready to repeat the cycle.

Epidemiology

W. bancrofii is distributed_widely throughout the tropics and subtrop_ics; B. malalti is restricted to South and Southeast Asia. B. timoi isrestricted to the eastern Indonesian archipelago. It is estimated that120 million.ppople ale infer:ted,,rvil_b,tl.:ese -parasites.

There is ni;animal res+r.voir for. ts/ br-mcrafii, b*t,,ll" ma[ayi has been found infelines audprimates. Even in encieirric u."u., orrly a small proportion(less than lva) of mosquito bites are infective. It is proiabie thatpatent.infections are produced only when a susceptibie person re_ceives a large number of infective larvae and that obstructive diseasedevelops only when exposure continues for many years. Filariasis ismainly a disease of adults and is more

"o*onin men.zz.23

Pathologic Characteristics

lymphatics harboring adult worms display endothelial proliferation,fibrin deposition, and a granulomatous lnflammatory infiltrate oieosinophils, lymphocytes, and macrophages. Molting and the deathof worms probably exacerbate the infllmmation, which is succeededby fibrosis and obstruction of lymph flow. All of these processes areassociated with complex immunologic events.

It is possible that a proportion of the population in endemicareas generates protective immunity that may be T celt mediated.2aSecondary bacterial infection may be an important cofactor in thedevelopment of elephantiasis.2s

Clinical Features

Many patients are asymptomatic despite the presence of a microfila_remia. clinical manifestations are due eithei to acute inflammation9r t9 ct]ro.nic lymphatic obstruction. Attacks of lymphangitis orlymphadenitis with fever, headache, backache, and nausea occasion_ally occur. Acute funiculitis, epididymitis, or orchitis may be seen.These acute episodes usually iubside after a few days io severalweeks but may recur.26 Chronic lymphadenopathy is frequently foundand may be the only manifestation of filariasis. In l,ong_siandingcases lymphedema may develop. Chronic hydrocele is-the most:o*gl feature and may cause considerable iexual disability. Thelower Iimbs are involved less frequently; at first there is pitting

:edema that is most marked pretibially, but eventually nonoittino .,edema may involve the whole limb. In elephantia.ir, ttl .n"li'iilE .leg or scrotum becomes thickened, fissurid, and *arty. Ul;;;;,il

=and secondary infection may occur.27 Occasibnally, fyr"pf, ,*.1"-,.1imay be seen, especially in the genital region. Cnyfutu d.";;;; -,when swollen lymphatics burst into the urin-ary tract. ,,,:a

.:iDiagnosls I .]iThe deflnitive diagnosis of bancroftian filariasis and brugian Rtariasrsrjjdepends on demonstration of the parasite. Unfortunaiely, d;;fi.=lariae are-frequently absent from the^ blooGin both the

"u.iy *a tug,i

stages of the disease. A blood sample should be taten "-ral,,:imidnig-ht unless the patient is from thi South paciflc. irr.-,,,,.*'i, ,.:stained and examined for.microfilariae (Fig. 27g_l). If none *i"Li-:.=

a concentration method should be used. ' ...,

, Microfllariae may occasionally be found in hydrocele fluid or,.,Tchylous urine. Eosinophilia.is usuilly absent excepi dr.i;;.p;;; _jof acute inflammation. Serologic testi for antibody suct as u&tonite.:iflocculation, indirect hemaggiutination,

"nry-"_iink"d i;;;;;;;,,.:bent assay, and indirect flubiescent antibody tests may iJ;i;iil..ihelp but do not differentiate among the various fo.r", 6f nf*lu;;';; jbetween past and current infectior. I*-unoursay. to m.asu;;flft; ,.iantigen in serum have been described.2' polymerase .t,"1, i"l"tiil. -itests todetect W. bancrofti in blood are being developed.2e --

:iAdult worms can sometimes be found In fymg,i node biopsy,,,,*specimens, but this procedure is not generally;usiinea. uicrontariai:iEor y:11 fragments may be seen with fine_needle aspiration .V,J_ ,jogy.30 Ultrasonography of the lymphatic vessels in ttre spermati";;.1 ,;may reveal motile adult worms in dilated lymphatics'.3, AbnormJ*lymphatic drainage in the legs may be demonstrated by lydh;;""..jtigraphy.32 If microfllariae cannot be found, the diagnosis must bii,,::r,l€m:xie c,n clinir::..ri qlr:r,r*,ir,, il,1 lhe exclusion *f other

"iar,,,.,,.

-- - '-:i.i_.i

' aj1:

Treatment ._

There is no satisfactory trcatment for filariasis. Diethylcarbam urir* jcitrate has been used tbr 50 years. Given in an orA aose oi i i:,r*r.;..&daily for 2 weeks, it reduces the number of microfilaria; i;:ffi '-Eperipheral blood. Diethylcarbamazine kills some uauf, *..*, Urt .j

A

' t;;( tr W €'.."-boncrofli moloyt loo .:'','ffi

iffi

\'{l €H H H&I fu {€ozzordi slrcptoccrco yo/yulus #

Comparative features of sheathed (A) and unsheathed fB) ,=ffi

Bflporslons

FIGURE 278-1,microfilariae.

Chapter 278 - TtssuE NEMAToDES (TRtcHtNosts, DRAcuNcuLtAsts, FtLAR|AStS) 2947

not others. When it does kill wofins, it may precipitate acute in-flammation that culminates in an exuberant granulomatous processwith progressive fibrosis. Ivermectin in a single dose of 200 to 400pglkg has been shown to have a microfllaricidal effect similar tothat of diethylcarbamazine. Ultrasonography showed that it has noeffect on adult worms, and microfilariae often reappear in the periph-eral blood after a few months.33 Even if patients remain amicrofilar-emic after diethylcarbamazine or ivermectin treatment, Wuchereriaantigens persist in the serum for at least 2 to 3 years.3a Althoughdiethylcarbamazine and, ivermectin have no or limited therapeuticvalue for the individual patient, repeated administration of either orboth drugs every 6 to 12 months may reduce transmission in acommunity.33 Single-dose therapy with ivermectin at 200 to 400 pg/kg plus albendazole at 400 mg may be even more effective.3s Rarely,repeated treatment with diethylcarbamazine has succeeded in eradi-cating infection. This was achieved in Kinmen Island; acute inflam-matory filarial illnesses disappeared but, as expected, chronic ob-structive disease persisted for the next 2 decades.36

Acute inflammatory reactions should be treated with anti-in-flammatory agents. Mild lymphedema may be controlled with elasticstockings. Surgery is useful in the management of hydrocele but haslittle place for patients with elephantiasis of the legs. Laparoscopicligation of lymphatic vessels has been used successfully to treatrecalcitrant chyluria.3?

Prevention

The most effective preventive measure is avoidance of mosquitoesby the use of screens, nets, and insect repellents.

LOIASIS

Loiasis is caused by f-on 1,"o ani is !-rai',smittcd t.: ,:umans bytabanid fiies. It is charsii.-'i.";d:.,, .-;i:,:ii",i sul-,r'r-:ii:,rr,.,, swellings.Occasionatly, the wonn :s,,r.iea.n lriigr:.r.iing. trrrough.:1.....:e ,;;,1-.l..njunctiva

or other lissues.

Life Cycle

The white, threadlike adult worms, measuring 30 to 70 X 0.3 mm,migrate through the connective tissues. The sheathed microfllariae,300 X 8 pm, appear in the blood during the day and may be ingestedby tabanid (horse) flies, in which they develop into infective larvae.

Epidemiology

L. loa is irregularly distributed in West and central Africa. Thevectors are diumally biting flies (Chrysops spp.) that live in thecanopy of the rain forest. They are attracted by people movingthrough opetr spaces in the jungle. Infection rates in populations andparasite loads in individuals change little over time in endemic ar-eas.38

Clinical Features

Many patients are asymptomatic, although they may have high eosin-ophil levels in the peripheral blood. Transient swellings of localizedsubcutaneous edema, called Calabar swellings, may develop.3e Usu-ally only one swelling occurs ar a time. The onset may be precededby localized pain and itching for several hours. It is nonerythematous,10 to 20 cm in diameter, and lasts for several days to weeks. Calabarswellings are commonly seen around joints such as the wrist or theknee and recur irregularly at either the same or different sites. Otherpatients complain of pruritus or have urticaria. (Occasionally, a wonnmay be seen passing tfuough the subconjunctiva, where it producesan intense conjunctivitis lasting several days. Worms have also beenseen in the penis or around the nipple.) Infected visitors to areas of

endemicity may have a hyperreactive state characterized by morefrequent recurrences of fugitive swellings, greater eosinophilia, in-creased debilitation, and more complications, particularly the devel-opment of renal disease, either before or after treatment with diethyl-catbamazine.ao These features are associated with differences inimmunologic responses from those of people living in endemic ar-eas.a t

Other complications that may be seen are endomyocardial fibro-sis, retinopathy, encephalopathy, peripheral neuropathy, arthritis,pleural effusion, and breast calciflcation. Pulmonary infiltrates havealso been ascribed to loiasis, but it is difficult to differentiate thiscondition from tropical pulmonary eosinophilia. Splenectomy hasbeen performed on patients with suspected lymphoma that turnedout to be granulomas associated with L loa microfilariae.a2

Diagnosis

The disease should be suspected in a patient with a typical historywho has lived in West or central Africa. The diagnosis is establishedby flnding microfllariae in the daytime blood as described under"Bancroftian and Brugian Filariasis." Failure to find microfilariaedoes not rule out the diagnosis, and the diagnosis is usually madeon clinical grounds. A polymerase chain reaction test has beendescribed that is positive in some amicrofllaremic individuals but isnot generally availabie.a3 Occasionally, the. adult worm can be ex-tracted from the eye.

Treatment

Diethylcarbamazine eliminates microfllariae from the blood and oftendoes not kill adult worms,4 It is administerdd as described under"Onchocerciasis." Encephalitis, may be precipitated by treatment,especially if niicrrrfilaial,loads are trigh-+l ireatment with ivermectinin a single a:isi;'*T l.t:t1;Xi{k},rieLreai'es,rr*iqrofrlarial densities in theperipheral bib6di16 P;rientsiiwiih'higii'iiriiiiiii'arial counts (>30,000/ml) often experience fever, pruritus, headache, and artfualgia within36 hours of ivermectin therapy.aT Albendazole at 200 mg twice dailyfor 3 weeks slowly reduced microfilarial levels, possibly as a resultof an embryotoxic effect on the adult worms.a8

Prevention

Personal protection depends on avoiding places where biting fliesare numerous, wearing protective clothing. and using insect repel-lents. Mass treatment of villages interrupts transmission; diethylcar-bamazine is administered in doses of 5 mg&g/day fo.r 3 consecutivedays each month, or ivermectin may be given at 3lmonthly inter-vals.ae Diethylcarbamazine in a dose of 300 mg once weekly iseffective in preventing loiasis in persons resident temporarily inendemic regions.so

ONCHOCERCIASIS

Onchocerciasis (river blindness) is caused by Onchocerca volyulusand is transmitted to humans by blackflies. It is characterized by anitchy dematitis, subcutaneous nodules, keratitis, and chorioretinitis.

Life Cycle

After the bite of an infected Simulium blackfly, larvae penetrate theskin and migrate into the connective tissues. They develop into whitefiliform adults, the males being 3 X 0.2 mm and the females 400X 0.3 mm in size. The worms are often found tangled together innodules of fibrous tissue, where they may live for years. Each femaleproduces large numbers of unsheathed microfilariae 200 to 300 X 6to 8 pm in size that migrate through the skin and connective tissues.

2948 PArt III _ INFECTIOUS DISEASES AND THEIR ETIOLOGIC AGENTS

The life cycle is continued when they are ingested by female black_flies and develop into infective larvae.

Epidemiology

O. volvulus infects 20 million people in West, central, and EastAfrica and another 1 million people in scattered foci in centralAmerica and South America. There is no known animal .reservoir.onchocerciasis tends to be focal in distribution within areas in whichit is endemic. In Africa, the flies breed in fast_flowing streams inboth the savannah and rain forest and tend to bite low 6n the body.In America, the flies breed in smalr streams on the hillsides and biiemore fiequently around the head. Heavy parasite loads and severedisease require repeated infection.

Pathologic Characteristlcs

A granulomatous inflammatory reaction followed by fibrosis devel_ops around the..adult wonns. The microfilariae in the subcutaneoustissues may pro'buce a low-grade inflammatory reaction, destructionof the elastic fibers, and fibrosis. Different puit"*, of cell_mediatedand humoral immunity are seen in patienti with different clinicalsyndromes and in the presence or absence of microfilaridermia"5r

Clinical Features

Early skin lesions produce an itchy, erythematous, papular rash. Insevere infections, cutaneous lymphedema with reatireiy thickeningand depigmentation may be seen.52 Ultimately, loss of eiasticity wittchronic- lymphadenopathy may produce pendulous sacs containingi;:guina,!;.-r4d,femcr;rl l../rjtlli,,n":.l::i:. Firm, nontenrier, freely nr:}-rilif,i,rr:r;ir , ,*.iil{ls :hri ,;;,:,r,'l-..,:- _:.:i;,:,iel *iiii*"idr't.

".rti**i"rr-.;,,s.ize alrd.nray qontalli:iher a'rjiill worars may be found. They u.u,-r:ii..,cor,tiro.til loqared r..i'tr bonv irr+tninences. In addition. there mav.b:systernic f'eatures including weight loss and musculoskeletal pains.5:, .

Impaired visual acuity is the most serious complication. The rnostcommon lesion is punctate keratitis followed by pannus formationand corneal fibrosis. Microfirariae can often be-seen in the c.meaand anterior chamber with a slit lamp. Iridocyclitis, glaucoma, cho-roiditis, and optic ahophy may develop.sa.55 Not surprisingly, blind_ness in endemic areas is associated with a three- to fourfold increasein the mortality rate. It has been suggested that onchocerciasis maybe associated with an increased prevalence of epilepsy.56

Diagnosis

The diagnosis is made either by demonstrating microfilariae in skinsnips or in the cornea or anterior chamber orilit_lurnp examinationor by finding adult worms in a nodule biopsy specimen. Impalpablenodules can sometimes be demonstrated by ultrasound techniques.s?Bloodless skin snips are taken without anesthesia by raising smallcones of skin about 3 mm in diameter with the tip of a needle andthen cutting them off with a razor blade. Snips should be taken fromover the scapulas and iliac crests and from ihe buttocks and thighs.They are allowed to stand for half an hour in a drop of O.9Vo salineand are then examined under a microscope for microfllariae.

Microfilariae are sometimes found in urine. A red_dot card testhas, been proposed as a useful aid in screening for the presence ofoptic nerve disease.5s ultrasound detection of changes in ihe vitreoushumor has been described.5e Eosinophilia is com_iton. Reliable im_munodiagnostic tests are not yet generally available, but moleculartechniques are under development.6o

^ If the diagnosis is strongly suspected but parasites cannot befound, a single oral test dose of 50 mg of diethylcarbamazine can begiven. If an exacerbation of the rash occurs within a few hours, thediagnosis is likely (Mazzotti reacrion).

Treatrnent

Traditionally, patients with skin disease have been treared with dierh-ylcarbamazine. This drug kirrs microfilariae bur has lirtre .ir..il"the adult worm. Severe reactions such as rash, fever, g.nerulizejbody pains, keratitis, and iritis rnay occur, so the dose ,i" U" triiiup gradually as follows: day 1.5-0 mg: day 2.50 mg rfre. times;day 3, 100 mg three times; and days 4 to 21,3 mglig tfuee times ,

a day. " ---" .

. In the past few years, many studies have shown that ivermectin .

is safer and more effective than diethylcarbamazine.33,6r The rad ;;,,decrease in numbers of microfilariae in the,skin and anterior

"rru*t". ,of the eye and the severity of Mazzotti reactions are less "nJ

,fre ,

duration of the reduction in microfirariar loads is greater wittriv-ei ,

mectin than with diethylcarbamazine. Ivermectin is now the A.og ofchoice' unfortunately, rike diethyrcarb amazine, ivermectin ril;rii;kills microfilariae but not adult worms. When given in u ,irrgf"-Aori ,

it has little effecr on the viability or fertilir/ of adult w;ns, bu; l

courses of treatment with 150 pglkg repeated at 3-month rnteivJs ,for 2 to 3 years prevent embryogeneiis to the microfil*irf .irg. ,"jmay cause slow but steady attrition of adult 1"ofirr.ez. e: noth-singig l,

and repeated courses of fteatment result in marked reductions? ',,

microfilarial skin densities and the numbers of microfirariae rn *," ,

anterior chamber of the eye, and there is a significant reduction inl-transmission of infection. Ivermectin therapy liads to i-pror"-.ni

.in severe skin disease and regression of earty lesions of trr" "r*.i., 'segment of the eye, especially iridocyclitis, but posterior segment :,,lesions remain stable.6a. 65 A practicai approach to t

"u,rr"rfir-to ,administer ivermectin, 150 1;,g/kg orally once, rtnd repeat i i-_ ,,,

monthly intervals if there are continuing ,ymptom. o. "uia..r." of .,,

eye infection. Side effects appear to Ue rltativety mild in patients in ..,endemic areas but may be more severe in infecteil .*put.iut"r, *t o ,<;11en rir:i!ir:i: i-.i1;; p,;uritlrs, and arr. urticariai ,,,.,*. ii.,-,i,r,i..- :,

irs.'.un!ir..iJ;.;ii 1:i..r;;rrr.?:ai'1:ri 'onchocerciasis and loiasi.s :ir.r,,;r i;,iveil* lni": .,.eacepli:l.lgpiihlz li:,rai.rtreated with ivermectin.6? InarJ . rr re:.rr o.imi.,i._ ,

t.ation of ivsrixcetin ;iuring pregnancy was not asriciorr.a wiii-a.r .increased number of birth deficti. --

,Adult worms can be killed by.suramin, but this drug is not

generally recommended.6t Albendazole does not kilt micifitariaebut,interferes with embryogenesis.58 Amocarzine is a novel drug stillunder development that appears to have both macro_ and microfilar_icidal effects. Unfortunately, it does not prevent the evolution ofchorioretinopathy.6e Surgical removal of nodules should be performeilwhenever practical. Expert ophthalmologic advice shouldie soughtbefore the treatment of eye lesions.

,

Prevention

Personal protection depends on avoiding places where biting flies'are numerous and on wearing protective clothing. A major controlprogram is in progress in West Africa. The vector is being artackedby larvicides applied to breeding places; the onchocerciasii-infecredgoO-u^l1!on is gradually being replaced by a healthy popularion.To 71

In 1991 a program was set in motion io eradicaie onchocerciasislrom the Americas, and there is hope that one of the three majorfoci of infection will shortly be eliminated.Tz '

MANSONELLAINFECTIONS

Mansonella ozzardi, transmitted by blackflies and midges, is foundin Latin America. Adult worms are found in the visceral fattv issues,Unsheathed microfilariae that are not periodic may be found in the.peripheral blood. Most patients are asymptomatic.

. -Mansonella perstans, also transmitted by midges, is found in

Africa and South America. Adult worms fivL in ti'e body cavities.Unsheathed microfllariae may be found in the peripheral blood,especially at night. Most patients are asymptomatit, aithough somehave conjunctival nodules.73 If treatment ii required, dieth*ylcarba- ::::

:.i:

Chapter 278 _ TIssUE NEMAToDES (TRICHINos|s, DRACUNCULIASIS, FILARIASIS) 2g4g

.'diethylcarbamazine;76 the value of ivermeCtin is unproved.

TROPICAL PULMONARY EOSINOPHILIA

Ir.oni11t pulmonary eosinophilia is a disease syndrome caused bylariae in the tissues, especially the lungs. It is probably dul

fiBzine should be tried because ivermectin does not appear to beeffective.la Albendazole may be of some value when given at a doseof 400 mg twice daily for at least I month.Ts

Mansonella streptocerca is transmitted to humans by biting,midges. It is found in central Africa and is characterized by aermaltitis. Microfilariae are found in skin snips, and treatment is with

17. Magnussen P, Yaluba A, Bloch P The effect of mtibiotic- and hydrocortisone-containing ointments in preventing secondary infections in guinea worm disease.Am J Trop Med Hyg. 1994:,51:797J99.

18. Issaka-Tinorgah A, Magnussen P, Bloch p, yakuba A. Lack of effect of ivermectinon prepatent guinea-wom: A single-blind, placebo-controlled trial. Trans R SocTrop Med Hyg. 1994;88:346-348.

19. Chippaux JP. Mebendazole treatment ofdracunculiasis. Trans R Soc Trop Med Hyg.l99l;85:280.

20. Rohde JE, Shma BL, Patton H, et al. Surgical extraction of guinea worm:Disability reduction and contribution to disease control. Am J Trop Med Hyg.1993:48:71-76.

21. Hopkins DR, Ruiz-Tiben E, Ruebush TK. Dracunculiasis eradication: Almost areality. Am J Tmp Med Hyg. 1997;57:252-259.

22. MichaelE, Bundy DA, Grenfell BT. Re-assessing the glob4l prevalence and distribu_tion of lympharic filariasis. Parasitolo Ey 1996i112:4094r9.

23. Kazura JW, Bockrie M, Alexmdq N, et al. Trmsmission intensity md its relation-ship to infection and disease dte to Wuchereria bancrcfti in papua New Guinea. JInfect Dis. 1997 ;17 6:242-246.

24. Steel C, Guinea A, Ottesen EA. Evidence for protective immunity to bmcroftianfllariasis in the Cook Islands. J Infecr Dis. 1996;174:598405.

25. Olszewski WL, Jamal S, Manokmm G, et al. Bacteriologic studies of skin, tissuefliid, lymph md lymph nodes in patients with filaial lymphedema. Am J Trop MedHyg. 1997:57:7-15.

26. Ramaiah KD, Ramu K, Kuma KN, Guyatt H. Epidemiology of acute filarialepisodes caused by Wuchereria bancrufi infection in two rural villages in TmilNadu, south India. Trans R Sm Trop Med Hyg. 1996;90:639_643.

27. Burri H, Loutan L, Kumaraswami V, Vijayasekuan V. Skin changes in chronicfilarimis. Tms R Soc Trop Med Hyg. 1996;9O:671-674.

28. Freedma DO, de Almeida A, Miranda J, et al. Field trial of a mpid cud test forWuchereria bmcrufti. Lmcet. 1997;350: 1681.

29. R.awy RM, Farid tIA, Kamal IH, et al. A polymbmse chain reaction-bmed assayfbr detetion of Wuchereria bancrofii in hmm blood nd Culex pipiens. Trans iSoc Trop Med Hyg. 1997;91:156-160.

30. Arcra VI( Singh N, Bhatia A. Cytomorphologic profile of lymphatic filuimis. ActaCy rol. 1996;4O:948 -9 52.

31. Noroes J, Addiss D, Santos A, et al. Ultrasonographic evidence of abnomallymphatie vessels in young men with adult Wuch?reria bmqrofii infection in ssotaluem. J Urol. 1996;156:4W412

J2. Dissanayake.s. Watma L, Piessens WF- Lymphatic,pathology in Wuchereria ban:' - ' .crofri'liiatdfilaraemic infrcrions. Trms R Sm Trop ,lvled HrE.,ISq5;S9:StiZ-5d1- r .:',l;r

:-33. Grove Dl:,i(lher-notherapy of the fitriases. Cun:Cdpcq,Flililic'i,i.Efu: .l9i.fii:439+,iarr,,

' *. li.1;nru rou. Higt,.*., evr,.:,eoais DG. L;#"-rji 3i".1'rl';.rr,L',",iui -i'

ban :rolti .dniig6 afler ueatmefii with diethytcai.b'fuirr.rH. ?,i'iu.fi""ti,il ai, j frop "i

Med Hyg. 1997 ;57 :483486.35. Addiss DG, Beach MJ, Streit TG, et al. Randomised placebo-controlled comparison

of ivemectin and albendazole alone md in combination for Wuchereria bincroJtimicrofiluaemia in Haitim children. Lancet. 1997 :350:480494-

36. Fan PC, Peng HW, Chen CC. Follow-up investigations on clinical mmifestationsafter filtriasis eradication by diethylcmbmuine medicated comon salt on Kimen(Quemoy) Island, Republic of China. J Trop Med Hyg. 1995;98:461-464.

37. Chiu AW, Chen MT, Chmg LS. Laproscopic nephrolysis for chyluria: Case reportof long-tem success. J Endourol. 1995;9:319-322.

38. Garcia A, Abel L, Ranque S. Longitudinal suruey of 1za laa filaiasis in southemCmeroon: Long{em stability md factors influencing individual microfiluial status.Am J Trop Med Hyg. 1995:57:37O-375.

39. Noireau F, Apembet JD, Nzoutmi A, et al. Clinical manifestations of loirois in anendemic area in the Congo. Trop Med pilasitol. 199O;41:37_39.

40. Churchill DR, Moris C, Fakoya A, et al. Clinical md laboratoryTeatures ofpatientswith loiasis (Iaa loa filuiasis) in the U.K. J Infect. 1996;33:103-109.

41. Klion AD, Musougbodji A, Sadeler BC, et al. Loiasis in endemic md nonendemicpopulations: Imunologically mediated differences in clinical presentation. J InfectDis. l99l ;163:13 l8-t325.

42. Burchard GD, Reimold-Jetrle U, Burkte y, et al. Splenectomy for suspected malig-nant lymphoma in two patients with loiasis. Clin Infect Dis. 1996:23:9j9_992.

43- Toure FS, Bain O, Nerrienet E, et al. Detection of lna loa-spxific DNA in bloodfrom mcult-infecred individuals. Exp ptrasitol. 1997 i86:163-170.

44. Klion AD, Onesen EA, Numan TB. Effectiveness of diethylcarbmzine in treatingloiasis by expatriate visitors to endemic regions: Long{em follow-up. I Infect DisI1994;169:604-61O.

45. Came B, Boulesteix J, Boutes H, et al. Five cases of encephalitis during treafinentof loiuis with diethylcarbmazine. Am J Ttop Med Hyg. 199l;44:68449}.

46. Gudon J, Kamgno J, Folefack G, et al. Marked decrcase in Ina loa microfil?d:rernasix and twelve months after a single dose of ivemectin. Trans R Soc Trop MedHyg. t997;91:593-594.

.47. Ducorps M, Gardon-Wendel N, Rmque S, et al. Effets s6condaires du traitement dela loase hypermicrofilar6mique par I'ivermectine. Bull Soc pathol Exot.1995;88:105-l 12.

48. Klion AO, Massougbodji A, Horton J, et al. Albendazole in human loiasis: Resultsof a double-blind, placebo-conrrolled trial. J Infecr Dis. 1993:168:202-206.

49. Rmque S, Garcia A, Boussircsq M, et al. Decreased prevalence and intensity ofIna /oa infection il a comunity heated with ivemectin every three months fortwo yeils. Trans R Soc Trop Med Hyg. 1996;90:429430.

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to immunologic hyperresponsiveness to W. bancrofii or- B. malayi. Itis scattered throughout the tropics but is most iommonly seen insouthern Asia. Patients have recurrent episodes of a paroxysmal, drycoug-h, wheezing, and dyspnea. Malaise, anorexia, and weight losiere frequently seen. Physical examination often reveals scatteredrvheezes and crackles. Some patients may have hepatomegaly andIymphadenopathy. The symptoms usually fluctuate in ser"ity ou".

,:,*nany months. The absence of microfilariae from the blood makes a

2 weeks is an effective treatment. There may be an initial exac;rba_.ji) z wcrr! rs aI} errecuve ueatment. lnere may be an rmtial exacerba_!.tion of symptoms, but the eosinophil level falls, aild the chest!.,1adiograph clears over a few weeks. A small proDortion of Datients-proportion of patients,

!!. found in the serum. A presumptive clinical diagnosis can usually be

:definitive diagnosis difficult. Eosinophilia is almost always present,..often at exhemely high levels. Chest radiographs usuilly revealscattered reticulonodular opacities. Antibodies to f,larial worms are

|:,m1de without recourse to lung biopsy, and the diagnosis is eitab_. lished by a successful response to therapy. The administration of

diethyJcarbamazine orally in a dole of Z igtkg three times daily for

:, however, have persistent subtle clinical, radiologic, or fxnctionall;,ahnorrnalities indicatingr chonic low-grade alveolitis;? in.sueh in_.rr:stadceg' it may be appmgriate to repeat the courserof Gatiiient.ivittr

1lig.i!1y!;41h.urrazine. T.hc:role of ivermectin in the tealrnent of tl.rpi-,eai:prilmonary ecsinuph.iir has not yet been determiried. ' ..1: '::': '

i..R E F E R E N C E S...

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