QJM vol. 98 no. 1 © Association of Physicians 2005; all rights reserved.
Correspondence |
Schistosomiasis among travellers returning from Malawi: a common occurrence
Sir,In August 2001, 11 pupils accompanied by four teachers, from a secondary school in London, visited Malawi for 4 weeks. During their trip they swam in Lake Malawi, having been assured by local people that this area was free of schistosomiasis.
Five weeks later, one of the pupils, a 17-year-old boy, presented with a history of ‘flu-like’ symptoms, an itchy rash and swelling of the eyelids. On direct questioning, he remembered a generalized itchy rash that occurred immediately after swimming. Clinically, he was apyrexial with an extensive urticarial rash. The rest of the examination was unremarkable. He had an eosinophilia at 0.98 x 109/l and elevated alanine transaminase, but otherwise investigations were normal. Stool and urine microscopy and schistosomiasis serology were negative. He was admitted and diagnosed with Katayama fever, an acute manifestation of schistosomiasis. He was given two doses of praziquantel, 20 mg/kg and prednisolone 20 mg daily for 5 days.
On the day of his discharge, his friend, a 16-year-old boy, presented with a 10-day history of ‘flu-like’ symptoms, fever and swelling of the lips, eyes and hands. He had wheals on his limbs, but examination was otherwise normal. Investigations revealed an eosinophilia of 2.21 x 109/l. Stool and urine examinations were negative, but his schistosomal serology was weakly positive. He was also diagnosed with acute schistosomiasis and treated with praziquantel and prednisolone.
We subsequently screened all 15 members of the party 8 weeks after their exposure using a structured questionnaire, clinical examination and laboratory testing. In all, 13 had acquired schistosomiasis; all 13 had an eosinophilia. Twelve had positive schistosomal ELISA and two had eggs of S. haematobium seen in their urine. No cases of S. mansoni were found. The two index cases displayed the most florid clinical picture of Katayama fever, but ten others complained of a range of symptoms (Table 1). Of the two that did not become infected, one spent less time in the lake than the others (3 h compared to an average of 8.5 h) and the other had applied copious amounts of mosquito repellent. Prophylactic DEET has been shown to reduce the risk of acquiring schistosomiasis infection.1
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Schistosomiasis has three distinct clinical syndromes.2 The first, ‘swimmer's itch’, occurs in response to cercarial penetration of the skin. Katayama fever, the second clinical entity, classically occurs 4–6 weeks later, and is thought to be precipitated by the onset of ovulation by maturing schistosomulae. The syndrome is most marked in primary infections in patients who have not previously been exposed.3 Chronic schistosomiasis results from the deposition of schistosome eggs and subsequent fibrosis, classically involving the liver with S. mansoni and S. japonicum, and the urogenital tract with S. haematobium. Significant morbidity may also be associated with ectopic disease at various sites.4 The high prevalence of infection among this group reinforces the frequency with which schistosomiasis is acquired in Lake Malawi.5 The range of symptoms they experienced were very non-specific, and could easily have been attributed to a viral infection; indeed several had consulted primary health care services and been given this diagnosis. The key to diagnosis is to suspect it in anyone with exposure to potentially infected waters 4–8 weeks previously, and the presence of a peripheral blood eosinophilia. A negative serology result and normal microscopy of stool and urine does not rule out schistosomiasis.
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Hospital for Tropical Diseases London e-mail: Tom.Doherty{at}lshtm.ac.uk
Acknowledgments
This study was supported by the Special Trustees of the Hospital for Tropical Diseases.
References
1. Jackson F, Doherty JF, Behrens RH. Schistosomiasis prophylaxis in vivo using N,N-Diethyl-m-toluamide (DEET). Tran Roy Soc Trop Med Hyg 2003; 97:449–50.[CrossRef]
2. Davis A. Schistosomiasis. In: Cook GC, Zumla A, eds. Manson's Tropical Diseases, 21st edn. London, WB Saunders, 2003; Chapter 72:1413–56.
3. Doherty JF, Moody AH, Wright SG. Katayama fever: an acute manifestation of schistosomiasis. Br Med J 1996; 313:1071–2.
4. Blunt SB, Boulton J, Wise R. MRI in schistosomiasis of conus medullaris and lumbar spinal cord. Lancet 1993; 341:557.[Medline]
5. Cetron MS, Chitsulo L, Sullivan JJ, Pilcer J, Wilson M, Noh J, Tsang VC, Hightower AW, Addiss DG. Schistosomiasis in Lake Malawi. Lancet 1996; 348:1274–8.[Medline]
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