[Toxocara canis infection. Environmental parasitologic and epidemiologic studies]

Due to the large number of differential diagnostic possibilities, the etiology of endogenous uveitis is still hard to determine. One reason for uveitis may be the occurrence of parasites. However, too little attention is paid to this underlying disease.

To identify certain sources of infection, ovoscopic probes of 98 dog feces from the urban area of Halle were taken. The material was collected from children's playgrounds, parks and swimming pools. A retrospective analysis of patient case data from the records of the University Eye Hospital for the years 1986-1995 complemented the environmental and parasitological examination of patients with Toxocara canis and T. cati infections.

From the ovoscopic examinations, 16% of the fecal samples contained T. canis eggs. Seventeen percent contained coccicidal sporocysts. Eggs of Trichuris vulpis and not clearly identifiable nematodal larvae were found in 1% of the samples. The reasons for the morphology was, in one instance, suspected Echinococcus eggs. The fact that 12 or 15 parasitologically positive dog excrement samples were taken from the immediate vicinity of children's playgrounds and another three directly from these grounds should be regarded as particularly critical. The investigated patient case data records revealed for the period studied nine uveitic patients with T. conis infection. The diagnosis was based on the larva precipitation test in all cases. After correct diagnosis and appropriate treatment, the prognosis was favorable. The specific treatment had to be repeated in two patients.

The environmental parasitological study presented proves the relatively high prevalence of pathogenic causal agents in dog excrement samples from the area of urban recreation and leisure grounds, in particular, children's playgrounds. Parasite infestation is a mirror of the efficiency of hygienic and social measures. Public health education must be reinforced. Differential diagnosis of chronic endogenous eye diseases must pay more attention to infections by parasites.