Avaliação do potencial de tilápias do Nilo na eliminação de ovos de Toxocara canis para o meio ambiente

Abstract

The culture of the consumption of raw fish flesh is spreading around the world, and with this also increases the number of cases of zoonoses caused by parasitic agents that use the fish as hosts. Although toxocariasis is primarily a geozoonosis, its transmission is also amenable to the consumption of raw or undercooked meat from paratenic hosts. In humans the larvae migrate from the small intestine to various organs, but the life cycle of the parasite is not complete. There is a scarcity of studies about role of fish in the epidemiological chain of the disease. The objective of this study is to evaluate the ability of fish to promote the dispersion of Toxocara canis eggs in the aquatic environment and to verify the migration of larvae to the organs (liver, gastrointestinal tract (TGI), eyes, central nervous system) and in the musculature of using Nile tilapia as the experimental model. The fish (n = 15) was inoculated experimentally by gavage with 300 embryonic eggs of T. canis, and kept individually in plastic boxes during the experiment. The evaluation of the water contamination was performed by serial filtration in a set of sieves (212 and 38 μm), where the retained sediments were recovered and analyzed by microscopy. The evaluation of the tissue migration was made by acid digestion of the organs, performed at 16, 24, 48, 72 and 240 hours after inoculation. At each moment, three inoculated fish and one fish of the control group were analyzed (Control Group n = 5). The total egg recovery in the experiment was 48.4%, and 76.3% of the parasitic structures were aquatic and 23.7% in TIG. The negative binomial regression model showed a significant decline in both the elimination of embryonated eggs into the aquatic environment (p = 0.001) and in the presence of T. canis eggs in fish TGI (p = 0.007) over time. No larvae was recovered from the tissues. The data show that fish are proficient at eliminating T. canis eggs in the aquatic environment, and that although there is no tissue migration, fish can maintain apparently infective eggs of T. canis in the gastrointestinal tract. Thus, it is necessary to adopt adequate management practices with regular training for workers in the chain of production and fish handling to minimize the impacts of zoonoses transmitted by fish.