Environmental changes in the Brazilian Pantanal and Cerrado facilitate the spread of parasitic diseases in wildlife, with significant implications for public health owing to their zoonotic potential. This study aimed to examine the occurrence and diversity of gastrointestinal parasites in wild felids within these regions to assess their ecological and health impacts. We collected and analyzed helminth-positive samples from 27 wild felids using specific taxonomic keys. Diverse parasitic taxa were detected, including zoonotic helminths, such as Ancylostoma braziliense, Ancylostoma caninum, Ancylostoma pluridentatum, Toxocara cati, Toxocara canis, Dipylidium caninum, Taenia spp., Echinococcus spp., and Spirometra spp. Other nematodes, such as Physaloptera praeputialis and Physaloptera anomala, were identified, along with acanthocephalans from the genus Oncicola and a trematode, Neodiplostomum spp. (potentially the first record of this parasite in wild felids in the Americas). Human encroachment into natural habitats has profound effects on wild populations, influencing parasitic infection rates and patterns. This study underscores the importance of continuous monitoring and research on parasitic infections as a means of safeguarding both wildlife and human populations and highlights the role of wild felids as bioindicators of environmental health.

A new species of nematode, Pterygodermatites (Paucipectines) sinopiensis n. sp. is described based on specimens recovered from the intestine of the white-bellied woolly mice opossum, Marmosa constantiae, trapped in the municipality of Sinop, Mato Grosso state, Brazil. The genus Pterygodermatites has 21 species described in mammals worldwide, and to date, only two species have been described for marsupials in Brazil. The new species is characterized by the presence of 23 small denticles and by the presence of 38–40 and 65 pairs of the cuticular processes in male and female species, respectively. Additionally, male species possess three ventral precloacal fans, and in female species, the cuticular processes are divided into 41 pairs of comb-like and 24 pairs of spine-like processes; the vulva opens approximately in pair 41. This study describes the parasite species fifth of marsupials in the Neotropical region.

Parasitic otitis is an inflammatory process that can affect the external to internal cattle ear, causing discomfort in animals, impairing performance, and even leading to animal death. The infection was initially associated with nematodes of the Rhabditis genus in tropical and subtropical regions. Currently, the nematode species described as associated with bovine otitis are Metarhabditis costai, Metarhabditis freitasi, and, more recently, M. blumi. It is worth highlighting that there is still a lack of robust information regarding the morphological details, ultrastructural aspects, and molecular biology data of these species. The Metarhabditis genus is composed of seven species and two more have recently been added. The objective of this study is to update the morphological data using advanced microscopy techniques to emphasize and clarify the main morphological differences between three species of Metarhabditis currently associated with parasitic otitis. Samples of inflammatory exudate were collected from four adult female Gir cattle (Bos taurus indicus) on a farm in Itabira, Minas Gerais state, Brazil. Specimens were analyzed using light microscopy and scanning electron microscopy. Two species, M. costai and M. freitasi, were morphologically identified, consistent with previous reports. Scanning electron microscopy revealed new structural characteristics of the nematode species involved in parasitic otitis compared with M. blumi obtained from the CGC Center. Significant differences were observed in the male posterior region, bursa, and tail. Molecular analysis was conducted to differentiate these three species, and it was observed that the species first associated with otitis formed distinct clusters compared to M. blumi. However, it is important to note that further studies are needed to genetically characterize species of the Metarhabditis genus.

The municipality of Sumidouro in the state of Rio de Janeiro, southeastern Brazil, is considered an area with low endemicity of Schistosoma mansoni. In this municipality, the wild water rat Nectomys squamipes is a wild reservoir of S. mansoni. A helminth community survey was carried out on N. squamipes populations in Sumidouro from 1997 to 1999. In the present study, we compared the helminth fauna and the helminth community structure of N. squamipes with a recent survey after a 22-year time interval, considering that the prevalence of S. mansoni infection in humans remained stable and that the area showed the same environmental characteristics. Seventy-three host specimens of N. squamipes collected between 1997 and 1999 and 21 specimens collected in 2021 were analyzed in this study. Seven helminth species were found in each collection period. The nematode Syphacia evaginata was recorded for the first time in N. squamipes in 2021. Syphacia venteli was the most abundant species in both periods and the most prevalent in 2021. During the period from 1997 to 1999, the most prevalent species was Hassalstrongylus epsilon. Significant differences in prevalence and abundance in relation to host sex were observed only for S. mansoni in 1997–1999. Significant differences in the abundance of the helminth species over time were observed only in Physaloptera bispiculata. Hassalstrongylus epsilon, S. venteli and S. mansoni were the dominant species in both periods. Litomosoides chagasfilhoi, Echinostoma paraensei paraensei and P. bispiculata became dominant, codominant and subordinate, respectively, over time. In conclusion, the helminth community of N. squamipes remained stable, with similar species richness, prevalence and abundance values and low beta-diversity over time. The occurrence of S. mansoni in the water rat has remained stable for decades, highlighting its importance for schistosomiasis control.

A new species of nematode parasite of the genus Delicata (Molineidae: Anoplostrongylinae) is described from the small intestine of a road-killed Greater Naked-tailed Armadillo Cabassous tatouay (Cingulata: Chlamyphoridae) on the BR-040 highway in Rio de Janeiro state, Brazil. The genus Delicata includes 13 species of parasitizing armadillos and anteaters distributed in Brazil, Argentina, and Trinidad and Tobago. The present species is distinguished from almost all species of Delicata by the longest length of the body, except for D. khalili and D. appendiculata. However, these can be distinguished from each other by the length of the spicules. The species that closely resembles, Delicata tatouay n. sp. is D. speciosa, but it can be distinguished by a robust branch from rays 2 and 3, rays 4 larger, and rays 8 longer compared to those of the new species. The new species is the only one with a tail, characterized by a terminal spine with rattlesnake tail-like transversal striations.

Marmosa constantiae is a species of marsupial, restricted to the central portion of South America. In Brazil, it is restricted to the states of Acre, Amazonas, Mato Grosso, Paraná and Rondônia. However, there is no study of the helminth fauna or helminth community structure for this marsupial. The aims of this study were to describe the species composition and to analyse the structure of the helminthic community of M. constantiae at the infracommunity level in an area of the Amazon Arc in Sinop, north of the state of Mato Grosso, Brazil. Parasites were searched in 53 specimens of this marsupial, among which 44 were infected with at least one helminth species. Parasitic helminths were counted and identified. Nine species were collected: seven nematodes, one cestode and one acanthocephalan. The most abundant species were Gracilioxyuris agilisis, Travassostrongylus scheibelorum, Pterygodermatites sinopiensis and Subulura eliseae. These species were the only dominants in the component community. No significant differences were observed in the abundance and prevalence of helminths between male and female hosts. Host body size significantly influenced the helminth abundance in males. The pattern of community structure considering the infracommunities in this locality indicated more species replacement than species loss along the environmental gradient. This is the first study to analyse the helminth fauna and the helminth community structure of M. constantiae.