Search

Poor microbiological quality of surface water such as lakes, rivers and canals used for recreational purposes by large groups of people may lead to many cases of disease. Microbiological contamination can originate from various sources, including both human and animal faeces, but can also result from increased levels of naturally occurring microorganisms. In Europe, the European Bathing Water Directive applies to all official bathing sites. At these locations, water quality must be checked regularly and must meet requirements for maximum faecal contamination. However, the most common recreational water-related health conditions in the Netherlands are skin complaints, predominantly 'swimmers itch'; this is caused by Trichobilharzia, a parasite of non-faecal origin. The number of disease outbreaks in any summer is strongly linked to the number of days when the maximum temperature is 25°C (77°F ) or above. Besides the impact of climate on recreational water-related pathogens, human behaviour also plays a role; the outcome of the interaction between these and other factors is as yet uncertain.

A 35-year-old man presented with fever and severe urticaria after visiting Uganda. His symptoms were caused by acute invasive schistosomiasis, also known as Katayama fever.

A 32-year-old woman from Cameroon presented with rectal blood loss due to a focally infiltrating adenocarcinoma of the rectosigmoid in the presence of an active intestinal schistosomiasis (Schistosoma intercalatum). A correlation between chronic intestinal schistosomiasis and the development of colorectal cancer has been suggested in the literature, but is not uniformly accepted. However, the case presented here reinforces this suggestion. In a patient with rectal blood loss who comes from an area where intestinal schistosomiasis is endemic, the possibility of a colorectal carcinoma should be considered in the diagnosis.

Despite treatment for malaria two travellers who acquired fever in Africa continued to have complaints: a 25-year-old Dutch woman and a 25-year-old Australian man. On questioning they appeared to have swum in Lake Malawi and a diagnosis of acute schistosomiasis was made, confirmed by serological tests. This syndrome, also called Katayama fever, is characterized by fever, oedema, urticaria and eosinophilia. The aetiology is not fully elucidated but it is supposed to be caused by immune complexes initiated by maturing worms and eggs. Patients who acquired fever in an endemic area must be questioned about contact with fresh water. Serological tests are important for the diagnosis. Treatment is with praziquantel but it is advised to treat only after the acute phase. During the acute manifestations corticosteroids may be necessary. Prevention is by avoiding contact with infected water. There is no vaccine. The role of artemisinin drugs in prevention is currently being studied.

Between 1918 and 1982, millions of patients suffering from bilharzia (infection by Schistosoma mansoni) in Egypt were treated with a series of injections with potassium-antimony tartrate. During large campaigns, aimed at the eradication of the parasite, syringes and needles were re-used without being properly sterilized. This has led to a wide spread of the hepatitis C virus, by which the prevalence of hepatitis C in Egypt is now the highest in the world. The results of this iatrogene epidemic will be devastating.

By combining field and experimental investigations, we were able to study several new aspects of fundamental problems concerning human and animal schistosomiasis in Senegal. Because of the controversy about the identity of Schistosoma curassoni and the possibly connected zoonosis, this parasite has been described once more. A great variety of experimental techniques were used. The eggs of S. curassoni are significantly smaller than those of the two other African species of Schistosoma we know of in ruminants (S. bovis and S. mattheei). But eggs of S. curassoni cannot be distinguished from those of the human, pathogenic S. haematobium. The study of the tegument of adult male worms shows a clear difference between S. bovis on one hand, and S. curassoni and S. haematobium on the other hand. S. bovis' tubercles are well formed, but have no stings at all. The tubercles of S. haematobium and of S. curassoni definitely possess stings. S. curassoni, S. haematobium and S. bovis are also clearly different as to their development in hamsters (Mesocricetus auratus). S. curassoni develops more rapidly and gets bigger than S. bovis and S. haematobium. Finally, different enzymatic systems allow us to distinguish S. curassoni from other schistosoma's of the haematobium group. S. curassoni has a typical pattern for phosphoglucomutase and hexokinase, differing from S. haematobium's patterns. In S. bovis, it differs by the patterns of phosphoglucomutase, glucosephosphate-isomerase, hexokinase and acid phosphatase. Epidemiological studies proved that, in Senegal, Bulinus guernei is the main vector of S. bovis, Bulinus senegalensis of S. haematobium (Northern Senegal) and Bulinus umbilicatus of S. curassoni and S. haematobium (Southern Senegal). There is no indication to consider S. curassoni as a zoonosis. When ruminants are infested by S. curassoni, the symptoms are light and the most important lesions can be found in the liver, the intestines and, in a lesser degree, in the bladder. S. curassoni develops easily in laboratory animals, giving severe lesions in liver and bowels. That makes it an interesting new model for studying the pathogenesis of schistosomes of the haematobium group and the action of new anthelmintics to be used against them.