Necropsies disclose a low helminth parasite diversity in periurban howler monkeys.

Primate-parasite interactions are often investigated via coprological studies given ethical and conservation restrictions of collecting primate hosts. Yet, these studies are inadequate to recover adult helminths for taxonomic identification and to accurately assess their prevalence, intensity, abundance, and site of infection. Fresh carcasses found in anthropogenic landscapes come as informative and reliable alternatives. In this study, we identified the helminths of brown howler monkeys (Alouatta guariba clamitans) and their sites of infection, and measured their prevalence, intensity, and abundance of infection. We necropsied 18 adult males, 11 adult females, and 7 juvenile males that died in conflicts with the anthropogenic environment (domestic dog attacks, n = 11; electrocutions and road-kills, n = 10 each; unknown, n = 5) in periurban landscapes of southern Brazil between 2013 and 2019. We found three nematodes (Trypanoxyuris minutus, Dipetalonema gracile, and Parabronema bonnei) and one cestode (Bertiella cf. studeri), a diversity estimated to account for a sampling completeness of 99%. Prevalence ranged from 3% for P. bonnei to 100% for T. minutus. Mean abundance ranged from 2 (D. gracile and B. cf. studeri) to 55,116 (T. minutus) and mean intensity of infection ranged from 4 (B. cf. studeri) to 55,116 (T. minutus). Trypanoxyuris minutus sex ratio was strongly male-biased. The intensity of infection with T. minutus was higher in juvenile males and adult females than in adult males. The low parasite diversity and the helminths' mode of transmission are compatible with howlers' arboreality and folivorous-frugivorous diet. The howlers were not infected with soil-transmitted helminth parasites of humans and domestic animals on the ground and probably did not eat invertebrates to complement the diet. Given the lack of evidence of howler health problems, we suggest that the causes of death of the necropsied howlers are the major threats to the long-term conservation of the species at the study periurban landscapes.

The relationship between pinworm (Trypanoxyuris) infection and gut bacteria in wild black howler monkeys (Alouatta pigra).

Gut bacteria may coexist with other groups of organisms, such as nematode parasites, that inhabit the gastrointestinal tract of primates; however, the possible effects of endoparasites on bacterial communities are frequently overlooked. Here we explored whether infection with Trypanoxyuris, an oxyurid gastrointestinal parasite, is associated with changes in the gut bacterial community of wild black howler monkeys (Alouatta pigra), by comparing gut bacterial communities of consistently infected individuals and individuals that never tested positive for Trypanoxyuris throughout different months across the year. We additionally controlled for other sources of variation reported to influence the primate microbiome including individual identity, social group, and seasonality. Trypanoxyuris infection was not related to differences in gut bacterial alpha diversity, but was weakly associated with differences in gut bacterial community structure. In contrast, among the covariates considered, both individual identity and social group were more strongly associated with variation in the howler gut bacterial community. Our results suggest that gastrointestinal parasites may be associated, to some extent, with shifts in the gut bacterial communities hosted by free-ranging primates, although a causal link still needs to be established. Further studies of wild primate hosts infected with parasite species with different pathogenicity are needed to better elucidate health-related consequences from the parasite-microbiome interplay.

Ocorrência de Trypanoxyuris (Trypanoxyuris) minutus (Schneider, 1866) (Nematoda, Oxyuridae) em Alouatta guariba clamitans Cabrera, 1940 (Primates, Atelidae) em Minas Gerais, Brasil / Occurrence of Trypanoxyuris (Trypanoxyuris) minutus (Schneider, 1866) (Nematoda, Oxyuridae) in Alouatta guariba clamitans Cabrera, 1940 (Primates, Atelidae) in Minas Gerais, Brazil

Este trabalho teve como objetivo registrar a ocorrência de Trypanoxyuris (Trypanoxyuris) minutus em Alouatta guariba clamitans no estado de Minas Gerais, Brasil, e fornecer dados quantitativos sobre as infrapopulações desses nematoides, além de dados morfológicos e biométricos de machos e fêmeas. Dois espécimes de A. guariba clamitans, mortos acidentalmente, foram necropsiados, visando aos estudos parasitológicos. Apenas o intestino grosso e o ceco estavam parasitados por T. (T.) minutus. A intensidade do parasitismo no intestino grosso foi de 6650 parasitos e a densidade de 2,6 parasitos/cm³ de intestino. No ceco, observou-se uma intensidade média de 6.753 ± 490,73 parasitos, com uma densidade média de 6,23 ± 5,13 parasitos/cm³. O presente trabalho fornece informações sobre a biometria dos adultos de T. (T.) minutus nessa espécie de hospedeiro, e se constitui no primeiro registro dessa espécie em A. guariba clamitans em Minas Gerais, Brasil.

This study aims to register the occurrence of Trypanoxyuris (Trypanoxyuris) minutus in Alouatta guariba clamitans, in Minas Gerais state, Brazil. Two specimens of A. guariba clamitans, died accidentally, have been necropsied for parasito-logical studies. Only the large intestine and caecum were infected by T. minutus. The parasitism intensity was 6650 parasites and the density was 2.6 parasites/cm³ of large intestine. In the caecum, the mean intensity was 6753 ± 490.73 parasites, with mean density of 6.23 ± 5.13 parasites/cm³. The present study supplies information on adult nematodes biometry and this is the first record of T. (T.) minutus in A. guariba clamitans from Minas Gerais State, Brazil.