[The infection risk for dogs raised helminth-free in conventional conditions in an urban area].

The present investigations were carried out to clarify whether or not and to what extent helminth-free raised dogs acquire patent and impatent helminth infections when exposed to an urban area contaminated with dog faeces. Groups of each 3 bitches at an age of 3, 6 or 9 months were taken out to an urban area (with average dog density of 1.5 per ha) for 3 hours daily on 5 days per week for a period of 3 month. During the whole trial the bitches and puppies born during this period were maintained under conditions which excluded other infections than those acquired during exposure in the urban area. The examination of the animals had the following results: All 9 bitches remained coproscopically negative until the end of the trial. In these bitches neither intestinal stages nor somatic helminth larvae were found. Seven out of 45 puppies from these bitches shed Toxocara canis eggs with the faeces. Shedding of eggs began 21 to 28 days after birth. Eggs excretion in most cases was low (< 33 eggs per gram). In 12 puppies from 5 litters intestinal stages of T. canis were found with a maximum of 4 specimens per animal. In 9 puppies only male or female T. canis were found.