Parasites can strongly influence host populations, particularly when the host is an ecosystem engineer. Oysters are ecosystem engineers that support estuarine communities and fisheries but are susceptible to 2 protozoan parasites, Perkinsus marinus (causing Dermo) and Haplosporidium nelsoni (causing MSX). Although both parasites are known to be influenced by environmental conditions, fine-scale temporal and spatial patterns remain underexplored in southeastern US estuaries. We examined parasite prevalence and intensity biweekly from April to October 2023 across 4 intertidal reefs on Sapelo Island, Georgia, and analysed concurrent water quality data (temperature, salinity, dissolved oxygen, pH) to identify potential environmental drivers of parasite prevalence and intensity. Parasite prevalence was high overall, 88% of oysters were infected with at least 1 parasite, and 34% were co-infected. Haplosporidium nelsoni prevalence was consistently high across sites, while P. marinus prevalence showed greater spatiotemporal variability, increasing through late summer and fall. Models indicated a time-lagged effect of environmental conditions on P. marinus prevalence, specifically with temperature and dissolved oxygen. Prevalence of H. nelsoni remained high throughout the year among sites and was best explained by temperature variability, salinity, and dissolved oxygen. Intensity levels did not differ among sites for either parasite. Our results demonstrate that even at small spatial scales and over time, oyster–parasite dynamics are shaped by multiple, interacting environmental factors, with time-lagged responses particularly evident for P. marinus. Understanding these dynamics is essential for predicting disease impacts under changing environmental conditions and informing management, restoration, and aquaculture strategies.

Haemonchus contortus, a highly pathogenic gastrointestinal nematode, significantly impacts small ruminant production, causing substantial economic losses in sheep and goat farming. This study examined the genetic diversity and population structure of 171 H. contortus isolates collected from the abomasa of sheep slaughtered across 8 distinct regions in Xinjiang, China. Using sequence analysis, phylogenetic reconstruction and population genetic analyses of the mitochondrial nad4 gene, we identified 163 haplotypes, with haplotype diversity ranging from 0.995 to 1.000 and nucleotide diversity from 0.02007 to 0.03145. The Tacheng population displayed the highest nucleotide diversity. Analysis of molecular variance revealed that 91.83% of genetic variation occurred within populations, with minimal differentiation among them (Fst: −0.01296 to 0.04274). Neutrality tests (Tajima’s D and Fu’s Fs) indicated no recent population bottlenecks. Phylogenetic and haplotype network analyses showed no distinct geographic clustering, suggesting extensive gene flow, likely facilitated by host movement. These findings provide critical insights into the genetic structure of H. contortus in Xinjiang, informing strategies for managing anthelmintic resistance and controlling this economically significant parasite.

Although venomous snakes from the family Viperidae, such as Bothrops atrox, are recognized for their medical importance due to snakebite accidents, few studies on parasitological aspects have been carried out with them, especially in the Amazonia region. Using morphological and molecular tools, we described a novel haemogregarine species infecting the common lancehead snake B. atrox from Eastern Amazonia, Brazil. Hepatozoon atrocis sp. nov. has mature gamonts that are morphologically distinct from those reported in the literature, which are often compact, with dispersed or encapsulated cytoplasm and chromatin. In the phylogeny recovered from the 18S rRNA gene, the Hepatozoon atrocis sp. nov. sequences formed a new clade, comprising a sister group to Hepatozoon spp. detected in other snakes, anurans, lizards and marsupials. This study reports the first Hepatozoon species described in the common lancehead snake. In addition, it provides a robust review of haemogregarine species infecting viperids from all over the world.

Research on helminth parasites of amphibians and reptiles has a long-standing history and has seen continuous growth. Recent efforts by various authors to compile comprehensive checklists are crucial for advancing our understanding of parasite diversity, ecology and evolution. Nematodes belonging to the family Molineidae parasitize vertebrates worldwide, with the genera Kentropyxia, Oswaldocruzia, Poekilostrongylus, Schulzia and Typhlopsia identified as infecting amphibians and reptiles across the Neotropical and Panamanian regions. While these parasites are relatively common, there is a lack of updated identification keys and incomplete information about their morphology, biology, distribution and host range. In this paper, we conducted an extensive bibliographic survey of Molineidae nematodes in amphibians and reptiles and provide a checklist of 53 species found in the Neotropical and Panamanian regions, including the Caribbean islands, along with updated details on their diversity, host range and geographic distribution.

The heligmosomid nematodes Heligmosomum mixtum and Heligmosomoides glareoli are dominant helminths infecting bank voles (Clethrionomys glareolus) in the temperate forests of NE Poland. Both are relatively long-lived species that accumulate in hosts with increasing host age. Based on studies showing that the closely related species, Heligmosomoides bakeri is immunomodulatory in murine hosts, we hypothesized that heligmosomid-infected bank voles should show higher prevalence and abundance with other helminths. To test this hypothesis, we analysed a database containing quantitative data on helminth parasites of bank voles (n = 922), comprising worm burdens recorded during 4 surveys, conducted at 3- to 4-year intervals, in 3 forest sites, during late summer of each year. After controlling for both intrinsic and extrinsic factors, the presence of heligmosomid nematodes was significantly associated with higher species richness of other helminth species, with the greater likelihood of voles carrying other helminth species, with higher worm burdens of other helminths and with significant positive covariance of heligmosomid burdens with those of other concurrently residing helminths. These patterns might be explained by a number of biological processes, including correlated host exposure or correlated host susceptibility not driven by the parasitic infections themselves. However, we consider it most likely that these results are consistent with the idea that like H. bakeri, the heligmosomid nematodes of bank voles employ non-specific immunomodulation to facilitate their own long-term survival, with the consequence that other concurrently infecting intestinal helminths benefit.