Dr. Murai Éva szerk.: Parasitologia Hungarica 21. (Budapest, 1988)

playgrounds were found to be contaminated by Toxocara eggs. During that survey 200 to 300 g sand samples per square metre were taken from each sandy playground and examined: on the average, 8. 7 (0-47) eggs were found in a sample of 100 g. Some authors observed seasonal fluctuations in the incidence of certain helminths: e. g. hookworms exhibited the lowest prevalence in January, then after an increase lasting up to July, a gradual decrease occurred until next January (LIGHTNER, CHRISTENSEN and BERAN, 1978). Summing up the data obtained for the parks surveyed (Table 5), it can be established that nematode eggs were somewhat more prevalent in the autumn months, whereas this was not true for tapeworms developing with an intermediate host. This may be attributed to the fact that together with the anti-rabies vaccination performed in the spring some veterinarians usually carry out deworming as well. Thus, due to the shedding of worms after treatment, mainly the more resistant Toxocara and Trichuris eggs become concentrated in the places where dogs are taken for walks. Animals that ingest the embryonating eggs will shed helminth eggs in the autumn months. In the case of Toxocara infection it should be examined when the number of young animals is higher during the year. In any case, to elucidate the cause underlying the phenomenon, large numbers of samples should be examined. The hazard of zoonoses is not reduced by the fact that eggs are more prevalent in the autumn and winter period when children spend less time in the parks and playgrounds. Namely, Toxo cara eggs remain viable for months; thus, eggs shed in the winter are able to cause infection during the spring and summer. Of the different groups of dogs, obviously those kept in dogs' homes or at pounds proved to have the most prevalent infection since most of them had strayed for weeks and months before they were examined. Dogs of Group B, which showed the second highest prevalence of infection, had come mainly from the country, from houses with gardens, and had worked as service dogs. Sometimes several dogs had been kept together, which rendered their reinfection possible. Furthermore, they mainly received antiparasitic treatment only during the training period spent in Budapest (Table 2). The low prevalence of infection found by surveys conducted by the Veterinary and Food Control Station of Budapest (D) may be due to several factors. One of them is the non-obligatory nature of this examination, i.e. that only those dog owners send faecal samples of their dogs to a laboratory who take great care to preserve their animals' good health status and are interested in the protection of the environment, too. Another possible cause is that these dogs have repeatedly been subjected to veterinary treatment, in some cases even to preventive anthelmintic treatment. Furthermore, most frequently these samples are examined only after a rather long time (not in fresh state), since the local veterinarian has to submit them first to the laboratory of the veterinary station where only a single examination is possible. Repeated faecal examination may furnish more accurate data on the dogs' infection status (BORAY, 1955). A comparison was made between dog faeces samples examined with the two different concentrating fluids. No significant difference was found between Breza's fluid and Flotol (Table 10) in the detectability of parasite eggs. However, when the same faecal samples were examined twice, the overall results indicated an infection of higher prevalence. The other comparison revealed (in addition to the superiority of two examinations to one) that with Breza's concentrating fluid a somewhat higher prevalence was found (Table 11). b) Results obtained in cats The results of faecal examinations in cats revealed (Table 6) that roundworm infection was much more prevalent than the other helminths, primarily in the group of stray cats. Faecal examinations performed abroad (Table 8) and the necropsy findings by KÁVAI (1977) support the above statement. The prevalence of infection with Taenia-type eggs was lower than those reported from abroad. This may be attributed to the different feeding habits (feeding poultry meat in the first place) and to the small number of stray cats.