[The epidemiology of gasterophilosis of horses in Switzerland].

Between March 1988 and December 1989, 198 gastrointestinal tracts from slaughtered horses from different areas of Switzerland have been analysed for the presence and the frequency of Gasterophilus spp. During the same period--always between July and November--200 horses from selected areas of Western Switzerland have been checked for the presence of eggs and their subsequent developmental stages in order to investigate further clinical and biological aspects of this infection. The evaluation has been performed according to origin, age, sex, colour of the horse and seasonal pattern of the cases and the various larval stages, respectively. The prevalence of Gasterophilus spp. amounts to 64.6%, showing a marked seasonal distribution. Only Gasterophilus intestinalis has been detected and the Western part of Switzerland appears to be considerably more contaminated than the other areas of the country. The reasons are discussed. It is possible that an intensive horse-traffic at the border is partly responsible. Horses with a dark coat are more often parasitized whereas no difference occurs with regard to age and sex. The observed high prevalence of this parasite infection in the Swiss horse population confirms that gasterophilosis has to be taken into serious consideration and prophylactic measures might be indicated.