Ecological features of the parasite-host system Serpentirhabdias aff. vellardi (Nematoda: Rhabdiasidae) - Amerotyphlops brongersmianus (Squamata: Typhlopidae) in Argentine Humid Chaco.

Amerotyphlops brongersmianus (Vanzolini, 1976) is the only representative of its family in Argentina, and to date, there have been no records of its parasites. Between 2013 and 2018, 46 specimens of A. brongersmianus were collected in Corrientes province and investigated for helminths. Eighty-three specimens of Serpentirhabdias aff. vellardi were collected from the lungs of nineteen hosts. Sixty-nine percent of the nematodes were collected from the vascular lung mostly, with a prevalence of 41.3% and a mean intensity of 3.74 worms. Adult snakes had higher prevalence and mean abundance than juveniles; the mean intensity was similar between sexes and sexual maturity groups. The association between sexual maturity and the presence of lungworms was statistically significant. Lungworm abundance, weight, and length of adult snakes showed weak to strong positive correlations, with stronger correlations in males; however, these were not statistically significant. Nematodes followed a negative binomial distribution. Seasonal differences in parasitological descriptors and mean body length of lungworms were not statistically significant. Nonetheless, a significant negative correlation was observed between lungworm abundance and body length in spring, suggesting a clustering effect. Our results are discussed based on host phenology, ecology, biology, and anatomy. The life cycles of lungworms, the abundance of potential transport hosts, as well as abiotic factors (rainfall and temperature), are also considered. This is the first report of lungworms in A. brongersmianus throughout its range, the second global report of helminths in a Typhlopidae species in the 21st century, and the first in South America and Argentina, providing ecological data.