Schistosomniasis

Schistosomniasis - July 30, 1993 / Vol. 42 / No. 29 565...

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Unformatted text preview: July 30, 1993 / Vol. 42 / No. 29 565 Schistosomiasis in U.S. Peace Corps Volunteers — Malawi, 1992 570 Update: Hantavirus Disease — Southwestern United States, 1993 572 Tuberculosis in Imported Nonhuman Primates — United States, June 1990— May 1993 Prevalence of Sedentary Lifestyle — Behavioral Risk Factor Surveillance System, United States, 1991 587 Quarterly AIDS Map Printed and distributed by the Massachusetts Medical Socrety, 576 publishers of The New England Journal of Medicine NGWL: ‘ii‘iis mtecten International Notes I! 13w “me 17: U! COde)« Schistosomiasis in U.S. Peace Corps Volunteers — Malawi, 1992 Schistosomiasis (i.e., "snail fever" or "bilharzia") is a parasitic infection caused by trematodes (flukes) and is endemic in 74 countries in Africa, South America, the Car— i55‘é’5"fij‘“3fi'a'”lt§i‘a. U.S. residents who work or travel inmt'heSe countries may be at risk for schistosomiasis. During 1992, two U.S. Peace Corps volunteers (PCVs) were evacu— ated from Africa because of Schistosoma hematobium infection of the central nervous systernwlng). Both were exposed to fresh water while vacationing at Cape Maclear, a popular resort area on Lake Malawi (Figure 1), in December 1991. This re- port summarizes the investigation of these two cases and a follow-up investigation of expatriates residing in Malawi. Patient 1 In March 1992, a 30-year-old PCV was evacuated from Namibia and evaluated at a U.S. medical center because of a 2-week history of headaches, unilateral (left) vision loss, and one episode of loss of consciousness consistent with a seizure. The patient had been a PCV for 2 years in Tunisia and was serving an additional 2 years in Na— mibia. He had no history of recreational freshwater exposure in Tunisia or Namibia. However, in December 1991, he had snorkeled during a 2-day period at Cape Maclear in Lake Malawi. A physical examination and white blood cell count (including eosinophil count) were normal. However, computed tomography (CT) and magnetic resonance imaging (MRI) scans detected an enhancing left parietal lesion with extensive edema. Because the lesion was initially presumed to be a meningioma, an open brain biopsy was per— formed. The biopsy specimen demonstrated a granulomatous abscess containing distorted eggs that had peripheral spines consistent with schistosome eggs. 5. hema- tobium eggs were identified in his urinary sediment but not in his stool. Schisto- somiasis serology using the Falcon assay screening test—enzyme—linked immunosor— bent assay (FAST-ELSA) was positive at CDC (7). A confirmatory immunoblot was positive for S. hematobium antibody but not 5. mansoniantibody. 566 MMWR July 30, 1993 Schistosomiasis — Continued The patient was treated with praziquantel (60 mg per kg body weight per day, orally in three divided doses) for schistosomiasis, phenytoin for his seizure disorder, and dexamethasone forthe cerebral edema. in June, his symptoms had resolved, and a CT scan documented continuing improvement. He returned to Namibia to complete his Peace Corps service. ' Patient 2 In January 1992, a 26-year-old PCV had onset of urinary frequency. In April 1992 she was evaluated in Botswana by a Peace Corps medical officer. Although a urinalysis was normal, she was treated in Botswana with antibiotics for a presumed bacterial cystitis. The patient had been stationed in an arid area of southern Botswana since 1990 and reported no recreational freshwater exposure in that country. However, in December 1991 she had snorkeled during a 7-day period at Cape Maclear, Lake Malawi. Because of progressive symptoms, including incontinence, lower extremity pain, and difficulty walking, in August 1992 she was referred to a medical center in the Re- public of South Africa for further evaluation, where an MRI scan revealed a mass in the conus medullaris of her spinal cord. A cauda equina tumor was suspeCted,-and she was evacuated on August 25 to the United States for neurosurgical consultation. On admission to the hOSpital in the United States, her general physical and neurologic examinations, complete blood count (including eosinophil count), uri- nalysis, and liver function tests were normal. On September 1, an exploratory laminectomy revealed that the area of the spinal cord opposite the body of the T11 vertebra was swollen, hyperemic, and firm to the touch. Examination of a biopsy FIGURE 1. Location of Malawi and southwestern region of Lake Malawi Vol. 42 I No. 29 MMWR 567 Schistosomiasis — Continued specimen was negative for a neoplasm or other definitive diagnoses. She was treated with dexamethasone to reduce the spinal cord inflammation. A schistosomiasis FAST- ELISA was positive at CDC, and an immunoblot confirmed the presence of antibody to S. hematobium but not S. mansoni. Routine stool and urine examinations, a 24-hour filtered urine examination, and a rectal biopsy specimen were all negative for schis- tosome eggs. 5. hematobium infection of the spinal cord was presumptively diagnosed based on the clinical presentation, exposure history, and positive serology. She was treated with praziquantel (60 mg per kg body weight per day, orally in three divided doses) and discharged from the hospital on September 9. By October 7, her leg pains and gait disturbance had improved. However, she has remained incontinent of urine and re- quires oxybutynin chloride and periodic self-catheterizations. Follow-Up Investigation These two cases prompted an investigation of the occurrence of and risk factors for schistosomiasis among expatriates in Malawi by CDC in collaboration with the Malawian Ministry of Health, the US. Department of State (DOS) (Malawi), the US. Peace Corps (Malawi), and the US. Agency for International Development (Malawi). In March 1993, a total of 995 resident expatriates in Malawi were surveyed to determine the prevalence of schistosomal antibody and to examine the seroprevalence in rela- tion to recreational water exposure at Lake Malawi. In addition, the southwestern shoreline of the lake was searched for vector snails (Figure 1). Of the 917 persons serologically tested, 302 (33%) had schistosomal antibody de- tectable by immunoblot; of these, 293 (97%) had antibody to S. hematobium. In addition, the seroprevalence was 33% among the 427 persons whose only reported recreational water exposure was at Lake Malawi (i.e., these persons reported no other recreational water contact in any coumry in which schistosomiasis is endemic). Infected Bulinus globosus snails (an intermediate host of S. hematobium) were identified inrotected coves adjacent to resort areas along the southern shore of Lake Malawi. This species of snail and B. nyassanus were found also on aquatic vegetation fl: 7 , at Cape Maclear. ' Reported by: M Wolfe, MD, D Parenti, MD, J Pol/net; MD, A Kobrine, MD, A Schwartz, MD, George Washington Univ Medical Center, Washington, DC. Office of Medical Svcs, US Peace Corps, Washington, DC. US Agency for international Development, Lilongwe, Malawi. Malawian Ministry of Health, Lilongwe. Parasitic Diseases Br, Div of Parasitic Diseases, National Center for Infectious Diseases, CDC. Editorial Note: Worldwide, an estimated 200 million persons are infected with and more than 600 million are at risk for schistosomiasis (2). S. mansoni and S. japoni— cum primarily affectthegenitourinary tract; chronic infection can lead to hepato— splenomegaly, variceal bleeding, ‘and cirrhosis. S. hematobium" primarily affects the genitourinary tract; chronic infection can lead to persistent cystitis, pyelonephritis, ob- structive renal disease, and increased incidence of bladder cancer. Infection is acquired by exposure to cercariae that penetrate the skin of persons in contact with fresh water containing infected snails. In the human host, cercariae ma- ture into adult worms that mate and deposit eggs (Figure 2). Adult worm pairs are generally located in the venous plexi surrounding the intestines (S. mansoni) or blad- der (8. hematobium). Migration of either adult worm pairs or ova may result in the dissemination of eggs to ectopic locations such as the CNS. Schistosome ova have i 568 MMWR July 30, 1993 Schistosomiasis —— Continued been found in a variety of host tissues (2—5 ), but the factors influencing ectopic migra— tion are not understood. Both 8. hematobium and S. mansoni are endemic throughout much of Africa, in- cluding Malawi, although Lake Malawi has been widely regarded as "risk—free” for Schistosoma Schistosoma hematobium Free-swimming cercariae penetrate intact skin in contact with infested fresh water. The cer— cariae mature into adult worms“ Adult worms, developing within the human host, mate and begin depositing eggs in the vasculature surrounding the intestine (S. mansoni) or bladder (S. hematobium). Eggs released into the stool or urine develop into forms infective for inter- Vol. 42 / No. 29 MMWR 569 Schistosomiasis —- Continued All PCVs and most DOS employees in Malawi have been serologically screened for schistosomiasis. Clinical evaluation of seropositive eXpatriates in Malawi is planned to determine the rates of egg excretion and morbidity associated with infection. To pre~ vent future morbidity associated with schistosomiasis, CDC recommends that expatriates and travelers with a history of freshwater exposure returning from areas with endemic schistosomiasis be serologically screened and that seropositive expatri- ates receive treatment with praziquantel following thorough clinical evaluation (i.e., quantitative stool and urine examinations for schistosome eggs). All persons traveling in Africa should be advised of the risk for schistosomiasis associated with freshwater lakes, streams, and rivers throughout the continent, in- cluding Lake Malawi. The only completely effective method of prevention is avoiding contact with fresh water in areas with endemic disease. If contact with fresh water is unavoidable, water should be heated to 122 F (50 C) for 5 minutes or treated with iodine or chlorine. In addition, water can be strained with paper filters or allowed to stand for 3 days before use. Physicians who treat travelers, expatriates, and immigrants should consider the possibility of neuroschistosomiasis in all patients who have a history of freshwater exposure in schistosomiasis—endemic areas and CNS abnormalities, even in the ab- sence of classic signs and symptoms of acute schistosomiasis (e.g., fever, nausea, vomiting, abdominal pain, diarrhea, and hematuria). Neuroschistosomiasis can occur several months after exposure to infested waterl10) and in low-intensity infections in which eggs may be undetectable or difficult to identify in urine or stool (70). Sensitive and specific serologic tests for diagnosing schistosomiasis (1 ) are available through CDC’s Parasitic Diseases Branch, National Center for Infectious Diseases, telephone (404) 4884050. Treatment with a single dose of praziquantel (40—60 mg per kg body weight) is safe and effective therapy against the adult worms of the three major species of schis- tosomes infecting humans (5. hematobium, S. mansoni, and S. japonicum). Corti- costeroids are often useful in neuroschistosomiasis to reduce edema and inflamma- tion. Although CNS schistosomiasis is rare, substantial morbidity from this condition is preventable by early diagnosis and rapid treatment (9). References 1. Tsang VCW, Wilkins PP. lmmunodiagnosis of schistosomiasis: screen with FAST-ELISA and confirm with immimoblot. Clin Lab Med 1991;11:1029—39. 2. Chen MG, Mott KE. Progress in assessment of morbidity due to S. hematobium infection: a review of recent literature. In: Tropical diseases bulletin. Geneva: World Health Organization, Parasitic Diseases Program, 1989:R2. (Vol 86, no. 4). 3. Gelfand M. Schistosomal involvement of the brain and spinal cord. In: Schistosomiasis in South Central Africa: aclinico-pathological study. Cape Town, Cape Province: Post-Graduate Press, 1950:194-202. 4. Scrimgeour EM, Gajdusek DC. Involvement of the CNS in S. mansoni and S. hematobium infection. Brain 1985;108:1023w-38. 5. Alves W. The distribution of Schistosoma eggs in human tissues. Bull World Health Org 1958;18:1092—7. 6. Marcial-Rojas RA, Fiol RE. Neurologic complications of schistosomiasis: review of the litera- ture and report of two cases of transverse myelitis due to S. mansoni. Ann Intern Med 1963;59:215—30. 7. Blair DM. Bilharziasis survey in British West and East Africa, Nyassaland and the Rhodesias. Bull World Health Org 1956;15:203—73. 570 MMWR July 30, 1993 Schistosomiasis -— Continued 8. Blunt SB, Boulton J, Wise R. MRI in schi cord {Letter}. Lancet 1993;341:557. 9. Blanchard TJ, Milne LM, Pollok R, Cook GC. tosomiasis [Letter]. Lancet 1993;341:959. 10. lstre GR, Fontaine RE, Tarr J, Hopkins RS. Acute schistosomiasis among Americans rafting the Omo River, Ethiopia. JAMA 1984;251:508—10. ...
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Schistosomniasis - July 30, 1993 / Vol. 42 / No. 29 565...

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