Helminth communities and host-parasite relationships in argentine brown rat (Rattus norvegicus)

Abstract

The aims of this research were: 1) to determine the helminth parasite fauna of seventy two <i>Rattus norvegicus</i> (Berkenhout, 1769) individuals inhabiting poultry farms in the Pampean region of Argentina; 2) to examine the relationship between parasitism and individual characteristics of the hosts, and 3) to analyze the associations among helminths. The study was carried out in twenty-four poultry farms from autumn 2000 to winter 2001. Nematodes were found in the intestine or caecum rectum of the 74 % of rats and cestodes were found along all the intestine of the 28 % of rats. <i>Heterakis spumosa</i> (Travassos 1914) was a central species, whereas <i>Syphacia muris</i>, Yamaguti 1941, <i>Nippostrongylus brasiliensis</i> (Travassos 1914) and <i>Hymenolepis diminuta</i> (Rudolphi 1819) were satellite species. Helminths do not affect rat survival and growth of rats. Rats parasitized with <i>H. spumosa</i> and <i>H. diminuta</i> were larger and older than non-parasitized rats. The intensity of infection with <i>H. spumosa</i> significantly increased with rat age. Rats parasitized with <i>Nippostrongylus brasiliensis</i> and <i>Syphacia muris</i> did not differ in size and age with respect to non-parasitized ones. The mean intensity of infections per host was 33.74, 74.28, higher than 200, and 3.10 for <i>H. spumosa</i>, <i>S. muris</i>, <i>N. brasiliensis</i> and <i>H. diminuta</i>, respectively. The mean intensity of infection with <i>H. spumosa</i> was higher in summer than in the other seasons, while the higher mean intensity of infection with <i>N. brasiliensis</i> and <i>S. muris</i> occurred in autumn. Infections with <i>Heterakis spumosa</i> and <i>Syphacia muris</i>, and with <i>Syphacia muris</i> and <i>Nippostrongylus brasiliensis</i> were independent; while <i>Heterakis spumosa</i> and <i>Nippostrongylus brasiliensis</i> were negatively associated.