Schistosomiasis: clinical relevance to surgeons in Australasia and diagnostic update

Schistosomiasis in Swedish travellers to sub-Saharan Africa: can we rely on serology?

In the absence of egg excretion, laboratory diagnosis of recently acquired schistosomiasis is dependent on serology. 42 of 83 Swedish adventure tourists to sub-Saharan Africa had serum anti-schistosome antibodies indicating recent infection. There is little doubt regarding the specificity and sensitivity of serology for the demonstration of infection, but there is a need for alternative serological methods which could be more widely used than the standard immunofluorescence assay (IFA) for antibodies against gut-derived antigens (anti-GAA). We present results suggesting that 40/42 anti-GAA positive cases also react with keyhole limpet haemocyanin (KLH), a readily available commercial antigen. High anti-GAA titres were seen for more than 2 y despite treatment with praziquantel. Thus we are faced with several questions. How likely is it that positive serology means treatment failure? What is the risk involved in chronic infection? What is the prospect for monitoring treatment outcome by serology? We conclude that there is a need for better information on the risk of becoming infected, for improved methods for testing and for monitoring the therapeutic effects in adventure tourists.

Schistosomiasis in patients in the Sultanate of Oman

BACKGROUND

Following an intensive public health eradication program, the focus of schistosomiasis mansoni at Salalah in Southern Oman (the only focus of schistosomiasis in Oman), appeared to have been eradicated in 1994. Since the vector snails for Schistosoma mansoni (and also for S. haematobium) were widely endemic in freshwater springs at Salalah, and reintroduction of infection (or introduction in the case of S. haematobium) was possible, we undertook a prospective study in 1995 for schistosomiasis in patients at the Sultan Qaboos University Hospital (SQUH), and to obtain evidence of visits by these patients to Salalah.

PATIENTS AND METHODS

From May 1995 to May 2000, Omani and expatriate patients presenting at SQUH were evaluated for possible schistosomiasis (residence in an endemic region, suggestive clinical features) by a search for ova in stool, urine, or in tissue biopsies, or when ova were absent, by serodiagnosis. A retrospective survey of schistosomiasis patients diagnosed in SQUH from 1990 to April 1995 was also performed. Ministry of Health (MOH) data on reports of schistosomiasis (a notifiable disease) in Oman from 1991 to 2000, were obtained.

RESULTS

Thirty patients with schistosomiasis were identified, 10 retrospectively and 20 in the prospective study. Patients were aged 9 to 60 years, and 25 of them (10 Omanis, 14 Egyptians, 1 Sudanese) contracted the infection in Africa, while 5 Omanis became infected in Salalah (3 in 1999). Twelve patients had schistosomiasis mansoni, 6 had schistosomiasis haematobia, and in the rest, infection by both parasites was confirmed or possible. The most common presentation (23%) was hepatosplenic schistosomiasis with portal hypertension. No patient admitted to contaminating freshwater with excreta in Salalah. MOH data revealed 3 to 14 cases of schistosomiasis were reported annually between 1991 and 2000, and that all schistosomiasis cases reported from 1994 to 1998 originated from Africa.

CONCLUSION

Schistosomiasis remains an important health problem in Oman. Many doctors are unfamiliar with the clinical features and methods of diagnosis, thereby frequently causing delays in diagnosis. Because vector snails are endemic in Salalah, schistosomiasis patients must be detected and treated early. At infested freshwater sites at Salalah, mollusciciding should continue indefinitely, and notices should warn visitors not to contaminate the spring water.