Toxoplasma gondii spreading in an urban area evaluated by seroprevalence in free-living cats and dogs.

Infection by the protozoan parasite, Toxoplasma gondii is widely prevalent in humans and animals throughout the world. Transmission takes place mainly by ingestion of raw or undercooked meat that contains parasite cysts or by ingestion of oocysts excreted in cat faeces, which can contaminate water and raw vegetables. The incidence of toxoplasmosis in urban areas can thus be also related to environmental contamination with oocysts. A direct measure of this environmental contamination by oocyst counting is unfeasible for technical reasons. An interesting alternative for measuring T. gondii urban spreading is the seroprevalence in free-living urban animals, used as sentinels, once they are exposed to similar risks of Toxoplasma infection-like humans. With this aim, we tested serum samples from stray cats and dogs for antibodies to T. gondii by indirect haemagglutination assay (IHA) and enzyme-linked immunosorbent assay (ELISA). Antibodies to T. gondii were found in 40% (40 of 100) of the cats, less than the 50.5% (101 of 200) found in dogs by ELISA (P < 0.05). Haemagglutination showed low resolution and concordance, precluding their use for diagnosis of T. gondii infection compared with ELISA. The prevalence of T. gondii was lower among stray cats probably due to their selective alimentary habits and lower water and food intake. Toxoplasma gondii seroprevalence in stray dogs and cats could be an indirect indicator of the parasite spreading in urban areas.

Infectivity of cysts of the ME-49 Toxoplasma gondii strain in bovine milk and homemade cheese.

OBJECTIVE: Analyze the infectivity and storage resistance of cysts of the ME-49 strain of Toxoplasma gondii in artificially infected bovine milk and homemade fresh cheese. METHODS: Pasteurized bovine milk was infected with 10 cysts/ml of the ME-49 strain of T.gondii and inoculated in different groups of mice, immediately or after storage at 4 degrees C for 5, 10 and 20 days. Homemade fresh cheese was prepared with artificially infected milk, and also tested in groups of mice, using the same storage process. Infection was identified by the presence of cysts in the brain or serological testing in challenged mice after 5 weeks, confirmed by Western Blot and histology. RESULTS: The infectivity of cysts of the ME-49 strain of T.gondii was maintained in the milk even after storage for 20 days at refrigerator temperatures. Cysts were also able to survive the production process of homemade fresh cheese and storage for a period of 10 days in the same conditions. CONCLUSIONS: These data demonstrated that milk and dairy products could be an important source of T.gondii in human contamination, reinforcing the importance of milk pasteurization before any processing or ingestion.

The prevalence and avidity of Toxoplasma gondii IgG antibodies in pigs from Brazil and Peru.

Raw or inadequately cooked pork is an important source of Toxoplasma gondii infection, and the infection rate in animals used as human food, is an important risk predictor. The prevalence of this infection was estimated in 396 sera from 5-month old pigs obtained at abattoirs in São Paulo, Brazil (300) and Lima, Peru (96). The seroprevalence was higher in pigs from Peru (32.3%) as compared to Brazil (9.6%), as detected by ELISA and Western blot. Hemagglutination gave poor resolution which was not useful for the diagnosis of T. gondii infection. Specific antibody avidity is correlated with infection time, as shown in experimentally infected piglets. Using an arbitrary cut-off of 50% avidity index, Brazilian pigs were found to be more recently infected than Peruvian pigs. Pork should be considered a significant source of human T. gondii infection both in Brazil and Peru. Avidity assays could help in the detection of the time of T. gondii infection in pigs, allowing preventive management.