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

In contrast to the above data, in the present survey helminths belonging to the family Ancylostomatidae were more frequent in groups comprising older animals (stray and service dogs) (Table 2). The prevalence of Toxocara infection was found to decrease after the age of 6 months (Fig. 1). In the group of dogs treated at the university clinics, 3.22 and 1. 96% of the females and males older than one year, respectively

, were infected with Toxocara w

orms It has been reported in the literature that, when cleaning their puppies, the bitches may ingest 3rd-4th stage larvae shed by the pups, which may develop into mature worms in their small intestine. In pregnant bitches that became infected earlier, at whelping the larvae may be activated and may get not only into the mammary gland but some of them from the lungs, via the respiratory passages and pharynx, into the digestive tract where they reach maturity (KOBULEJ, 1977). British researchers arrived at the same conclusion as regards T. canis, adding that parallel with age the other roundworm species, T. leonina, did not show the abrupt decrease in prevalence characteristic for T. canis (ELSE et al., 1977). This is supported by the present findings. Our data obtained on the age distribution of Trichuris infection are mostly consistent with the results of other authors (HOSKINS, MALONE and SMITH, 1982; LIGHTNER, CHRISTENSEN and BERAN, 1978). After the age of one ye*ar a certain decrease can be observed in prevalence and this level remains characteristic for the other age groups too (Fig. 2). Data obtained on tapeworm infection indicate that in Hungary the prevalence of Dipylidium eggs was much lower than e. g. in Prague (VOKOUN and SLEZÁKOVÁ, 1977). Taenia-type eggs also occur less frequently than in most other countries surveyed. The detectability of tapeworms is rendered difficult by the periodical excretion of segments. Furthermore, Taenia spp. and E. granulosus cannot be differentiated on the basis of eggs demonstrated by faecal examination (BORAY, 1955). Therefore, in every dog found to shed Taenia-type eggs the possibility of Echinococcus infection should also be reckoned with. Faecal samples collected from the ground in city parks showed a lower prevalence of infection than the other samples. On the other hand, in the former Dipylidium eggs were somewhat more prevalent (Table 1). The examination of faeces excreted by dogs in downtown parks of Budapest revealed tapeworm eggs. T. vulpis eggs were detected most frequently: in some parks they were very rare while in others fairly common. In the latter places usually other helminth eggs were also common (Table 4). Trichuris eggs are resistant to environmental factors: in some places they greatly increase in number, making reinfection highly probable. In spite of the lesser public health importance of this helminthosis, it should be noted that this high prevalence can be considered an indicator of the hygienic status of the environment (parks, playgrounds). In the case of samples collected in parks it cannot be ruled out that faecal samples excreted by the same animal were collected repeatedly, since usually the same dogs are taken for walks in a given park. Of the surveys conducted abroad, the data obtained in West Berlin in 1981 indicate a lower prevalence of infection. In that survey 605 faecal samples were collected from the streets and exercise-grounds for dogs and were examined by tne flotation method. The prevalence of T. canis

, T. leonina

, Trichuris vulpis

, Ancylostomatidae and Taenia-type eggs in the samples was 3.5, 1.3, 1.2, 0.3 and 0.2%, respectively (HÖRCHNER, UNTERHOLZNER and FRESE, 1981). Several authors have reported on surveys aimed at determining Toxocara infection and on the examination of soil and sand samples. The data of these examinations are summarized in Table 9. The strikingly high prevalence of infection (58. 4%) found in Hungary by a survey conducted in 1970 (KOBULEJ, 1977) can be attributed to the fact that up to 1973 breeding had been practised in the studied population and thus most of the population was constituted by pups. By 19 74 the proportion of positive animals had decreased to 37.9%. Data from the College Faculty of Health were obtained from an unpublished thesis work (NAGY, 1981). In the survey conducted in Frankfurt (DÜWEL, 1983), shown in the same table, 27 out of 31 sandy