Murine Typhus from Vietnam, Imported into Japan

hypereosinophilia is an early warning sign, as seroconversion and egg excretion may be slower to evolve. Both elements provide sufficient circumstantial evidence to strongly suspect the diagnosis (2). In this case, the full-blown Katayama syndrome contributed to the evidence. Praziquantel only kills adult worms and does not inactivate schistosomules, nor the miracidium inside the eggs, which will continue to elicit a damaging immunologic response for some time. Early antischistosomal treatment might, in fact, worsen symptoms (7). Because schistosomules may require up to 8 weeks to mature, early postexposure treatment with praziquantel cannot be used to forestall disease after primary infection. Furthermore, Katayama syndrome may occur as early as 3 weeks after exposure. On the other hand, withholding praziquantel until larvae have matured (8 weeks after exposure) would not prevent Katayama syndrome in many cases (7). Acute symptoms, including early neuroschistosomiasis, may therefore still develop during this 5-week window after exposure, despite early praziquantel administration. Artemether has shown promising activity against schistosomules (8). Repeated administration throughout the transmission season has prevented Katayama syndrome in S. japonicum infection (9). Its use, singly or in combination with praziquantel, should be investigated as true postexposure prophylaxis for primary schistosomal infection in nonimmune travelers (10). Jan Clerinx,* Alfons van Gompel,* Lut Lynen,* and Berten Ceulemans† *Institute of Tropical Medicine, Antwerp, Belgium; and †University Hospital Antwerp, Edegem, Belgium