Diversidade de helmintos ictioparasitos da bacia do Rio Tramandaí, sul do Brasil

Abstract

Fish have the highest indices of parasite infections because the water environment facilitates the spread, reproduction and life cycle of most pathogenic agents. Parasites are an essential part of aquatic communities and parasitic diseases occur as a consequence of the imbalance between environment, host and parasite. The activity of different parasite species, mainly those that cause injuries or even great mortality to their hosts, have been the object of study especially in fish of economic interest. The reduction of the assimilation and growth rates of the hosts, caused by helminths, may limit their survival, either directly or indirectly. Additionally, parasitic helminths comprise a group of diseases that is connected to socio-environmental conditions and may lead to problems in public health, including zoonoses. Among the main food-borne parasitic zoonosis, those caused by the consumption of fish have been highlighted due to the increase in their incidence in several regions of the world in recent years. Studies directed to the knowledge of the parasite biodiversity associated to the freshwater fish fauna in Rio Grande do Sul are still scarce and, so far, no research study directed to the description of ichthyo-parasitic helminth species of the Tramandaí river has been conducted. Therefore, this work aims to know the diversity and occurrence of the helminth fauna associated with fish species collected in the Tramandaí river basin. For this purpose, we collected 300 fish between August 2015 and February 2017 and in the Laboratory of Ichthyology of Unisinos they were identified and underwent a necropsy. The helminths that were found were preserved, stained and identified. We calculated the parasitic indices such as prevalence, mean infection intensity and mean abundance. To evaluate the influence of parasitism on the development of fish, we performed a t-test, a Mann Whitney U test and calculated the Condition Factor. From the necropsy, we surveyed 3048 helminths distributed in the phyla Nematoda and Acanthocephala and in the class Trematoda. Among the identified trematodes, Clinostomum sp. and Ascocotyle sp. have zoonotic potential. For the fish evaluated regarding the effect of parasitism, Statistical analysis results indicated that the infection caused by the helminths does not interfere with the development of the analyzed fish.