The Pantanal is a large ecosystem located in South America. This preserved area is seasonally flooded due to abundant rainfall during the summer and the subsequent overflow of the Paraguai River. In this paper, we examine the helminth community structure in the wild rodent Thrichomys pachyurus during the wet and dry seasons in two locations of the preserved and cattle ranching areas in the Southern Pantanal. We identified 12 species of helminth, and, although we did not find any differences in species richness between locations within the Pantanal, we found that richness was higher during the wet season. Helminth species were largely aggregated in both farm locations and during seasons. The most common helminth species were more abundant during the dry season than during the wet season, which may have been due to the increased habitat availability and rodent population increase. The intensity of the infection also followed the same pattern for most helminths. The trichostrongylids (Heligmostrongylus crucifer, H. almeidai and Pudica cercomysi) were dominant at both farm locations. The land use of each area was not correlated with helminth diversity. However, species composition of the helminth community of T. pachyurus differed between locations and may be correlated with environmental differences between the habitats. The seasonality of the Pantanal was highly correlated with helminth parasitism in T. pachyurus.
Canine filariasis in domestic and wild dogs, foxes, and wolves is caused by several species of filarids. Although these filarial species inhabit different loci in the vertebrate definitive hosts, they generally release microfilariae into the bloodstream. Data about filarial infection in dogs in Brazil, especially on the Marajo Island, is scarce. For this reason, we conducted an analysis of 188 domestic dogs within two Marajo Island municipalities. The overall prevalence of microfilaremic was 32.45%; taken by blood smear and modified Knott's method. No significant difference of positivity between male and female was observed (X(2) Yates's correction = 0.341; p = 0.559). Significant age-infection ratios were detected (X(2) = 32.943; p < 0.0001). A high occult infection was detected (53.84%). PCR of rDNA and phylogenetic tree indicated that the microfilariae and adult worms found in domestic dogs from Marajo Island were Dirofilaria immitis.
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