Ectoparasites are ubiquitous and are often harmful to host fitness. Whereas protective responses to ectoparasitism in vertebrate hosts are well documented, our understanding of such defences in invertebrates remains limited. Here, we examined attachment-resistance in adult Drosophila to their naturally co-occurring ectoparasitic mites, Gamasodes pachysetis (Parasitidae). Significant differences in mite attachment duration were documented among 6 species of Drosophila, providing evidence for interspecific differentiation in attachment-resistance. Experiments with D. malerkotliana, a species exhibiting a relatively high rate of mite detachment, revealed that pre-infesting flies significantly reduced mite attachment duration compared to naïve controls, indicating a priming effect. In contrast, a reduction in attachment duration was not observed in D. malerkotliana after experimentally wounding the abdominal cuticle. These results suggest that the priming effect is not simply a response to cuticle damage, and that its activation may depend on mite-specific factors. Eight genes were individually tested for their effects on the rate of mite detachment from adult flies by deploying the GAL4-UAS gene knockdown system in D. melanogaster. Knockdown of heat shock protein 70Ba (Hsp70Ba) and prophenoloxidase 2 (PPO2), which underlie general stress and melanization responses, respectively, significantly prolonged mite attachment duration, implicating their involvement in host attachment-resistance to mites. Together the results support the existence of inducible protective mechanisms mediating parasitism by mites in a naturally occurring invertebrate host–ectoparasite symbiosis.

Comparative histopathological and ultrastructural investigations were performed on the livers of 2 fish species, namely, flounder (Platichthys flesus (L.)) naturally infected with the nematode Anisakis simplex (s.l.) (Rudolphi, 1809) larvae (L3) and tuvira (Gymnotus inaequilabiatus) (Valenciennes, 1839) harbouring the nematode Brevimulticaecum sp. (L3) (Shikhobalova and Mozgovoi, 1952). The intensity of infection by A. simplex (s.l.) larvae (L3) in flounders ranged from 3 to 10 parasites per organ. The worms were encapsulated by the peritoneal visceral serosa on the external surface of the liver. Infected P. flesus livers showed hepatocyte cytoplasmic rarefaction and cell swelling. A few immune cell types, such as macrophages, limited numbers of mast cells (MCs), lymphocytes and some epithelioid cells, were observed within the granuloma. The intensity of infection by Brevimulticaecum sp. (L3) in G. inaequilabiatus ranged from 4 to over 340 larvae per organ, and the nematode larvae were encircled by round-to-oval granulomas. Each granuloma possessed 3 concentric layers of cells and tissue: an inner layer in close proximity to the Brevimulticaecum sp. (L3) cuticle, formed by densely packed layers of epithelioid cells showing several desmosomes between each other; a middle layer of numerous MCs entrapped in a thin fibroblast-connective mesh; and an outer layer of fibrous connective tissue with thin, elongated fibroblasts. High numbers of macrophages and macrophage aggregates were scattered within the granuloma. This is the first study to compare the cellular nature of granulomas and the immune responses in the livers of paratenic fish hosts of 2 nematode species.

Lagostonema ecasiense is a bursate nematode parasite of Lagostomus maximus in Argentina. New morphological data, geographical distribution, ecological data, molecular characterization and exploratory phylogenetic analysis are provided. The general morphology and measurements agree with the original description with minimal discrepancies. The geographical distribution of Lagostonema is expanded with 3 new provinces and 9 new departments in Argentina. The molecular characterization constitutes the first molecular contribution for the genus Lagostonema. The analysis of genetic distances and phylogenetic exploration allow considering L. ecasiense as a nominal species, confirming its nomenclatural taxonomic identity. Likewise, although morphological studies allow the identification of specimens from all populations as L. ecasiense, molecular studies show a major genetic distance in the population from Santiago del Estero Province concerning the rest of the populations. Consequently, the haplotypes are mentioned as Lagostonema sp. with the possibility that these specimens belong to a new species. This study is valuable because it contributes to the ratification of a nominal species described decades ago, adding new morphological aspects and providing an understanding of their value as a marker of host populations.

The Galapagos sea lion (Zalophus wollebaeki) is an endemic and endangered species that plays a vital role in the ecosystem dynamics of the archipelago. In recent decades, they have faced a significant population decline, related to the effects of climate variability and anthropogenic influences. Thus, the co-occurrence of sea lion resting areas with mosquito breeding sites and the presence of free-roaming domestic dogs present significant health risks related to parasite transmission. This research demonstrates the occurrence of Dirofilaria immitis (canine heartworm) in Z. wollebaeki, indicating their possible function as a definitive host for this parasite. Blood samples collected in August 2023 from 50 individuals (juveniles and adults) in 2 rookeries of San Cristóbal Island, revealed a 2% prevalence of D. immitis in juvenile females, as confirmed by Knott’s test and polymerase chain reaction analysis. Results of this work emphasize the critical necessity for effective monitoring and conservation strategies to address the threat posed by D. immitis and to safeguard this endangered species.

Snakes serve as important hosts for parasites at the interface of wildlife, humans and domestic animals. However, their helminth fauna in tropical regions, particularly Thailand, remains poorly documented. This study investigates the helminth fauna, community structure, infection patterns and their co-occurrence dynamics in the monocled cobra (Naja kaouthia) from urbanized areas of central Thailand, based on comprehensive analyses of 34 wild-caught individuals. Using integrated morphological and molecular approaches (e.g. mitochondrial 16S rRNA and COI gene sequencing), 11 helminth species were identified – 9 nematodes (Kalicephalus bungari, Kalicephalus sp. I and II, Paracapillaria najae, Paracapillaria siamensis, Serpentirhabdias orientalis, Strongyloides sp., a filarioid nematode and an unknown encysted nematode), 1 cestode (Duthiersia expansa) and 1 acanthocephalan (Sphaerechinorhynchus sp.) – including 2 newly described species: P. siamensis (infected in gastrointestinal tract) and S. orientalis (in respiratory tract). Serpentirhabdias orientalis and K. bungari were the most prevalent species (75.8%), while encysted nematodes exhibited the highest infection intensities (up to 500 parasites per host). Host–parasite network analysis revealed strong organ tropism in some helminth species (e.g. Paracapillaria spp.) and non-random co-occurrence patterns. Parasite abundance was positively correlated with host body condition, and females harboured greater species richness than males (11 vs. 8 taxa). The absence of trematodes is consistent with the host’s terrestrial ecology, while the low prevalence of filarioids (3.0%) suggests limited transmission. These findings underscore the value of integrative taxonomy in revealing hidden parasite diversity and highlight ecological drivers of infection patterns in snakes, with implications for wildlife health and zoonotic risk in human-modified landscapes.

A species of acanthocephalan collected from the hindgut of Larimichthys crocea was identified as Longicollum pagrosomi Yamaguti, 1935 based on morphological characteristics. The complete mitochondrial genome of this parasite was sequenced. The mitogenome exhibited a circular structure with a total length of 14 632 bp, containing 12 protein coding genes (PCGs), 2 ribosomal RNAs (rRNAs), 22 transfer RNAs (tRNAs) and 2 major non-coding regions. The most frequently used start codon was GTG, and the most abundant amino acid was valine. The phylogenetic analyses of the mitogenome using Bayesian inference and maximum likelihood methods showed that the genus Longicollum formed a sister clade to the genus Pomphorhynchus, supporting the monophyly of Pomphorhynchus. This study reported a new host for L. pagrosomi and revealed the first complete mitogenome sequence of the genus Longicollum.

The water buffalo farm with intensive breeding techniques promotes the spread of lice (Haematopinus tuberculatus), leading to a reduction in meat and milk productions. Current control measures include the use of chemicals, which in the long-term lead to the development of resistance. Given the lack of alternative solutions, the aim of this study was to evaluate the repellent effect of a low impact by-product, the wood vinegar (WV), against H. tuberculatus using a new in vitro bioassay test. The test consisted of a glass Petri dishes subdivided in 3 separate areas. WV was tested at different concentrations (100%, 75%, 50%, 25%). Each of the 3 replicates was performed with 10 adults, at 27 °C and 75% relative humidity. Observations were made 5, 15, 30, 60, 90, 120 and 180 min after application to evaluate movement, the living/dead ratio and the ability to overcome the obstacle area of the lice, in terms of comparative avoidance (%). Additional in vitro cytotoxicity tests were performed. The test performed showed a repellent effect of 77% for the 100% WV concentration against lice of both sexes 30 min after exposure, similar (P < 0.05) to the repellent effect of deltamethrin (77%). The in vitro bioassay developed during the experiment proved to be reliable and can be used to evaluate the repellent effect of new molecules against lice before testing them in vivo. Furthermore, WV has a potential to be a valid tool for the control of buffalo pediculosis, although in vivo studies have to be undertaken.

Identifying interactions between species is essential for understanding ecosystem dynamics. With their central position in trophic networks, anurans underscore the importance of studying their interactions with other organisms. Traditionally, collecting and describing anuran helminth parasites rely on lethal methods, posing challenges for studying threatened species. In this study, we tested the effectiveness of non-invasive fecal metabarcoding and compared its accuracy to traditional invasive methods for identifying parasites and dietary components. We collected anurans from 6 families in the Brazilian Atlantic Rainforest and analysed their feces using the 18S marker while performing necropsies for traditional identification. Traditional methods identified 12 parasite taxa and 3 dietary items at lower taxonomic resolution. Fecal metabarcoding, on the other hand, revealed greater diversity and fine taxonomic resolution for dietary items, although with lower accuracy for parasites due to database limitations. The metabarcoding approach demonstrated a high potential for non-lethal biodiversity assessments, offering a more comprehensive view of dietary diversity and a viable alternative for studying parasites in vulnerable populations. However, its effectiveness depends on improving reference databases, especially for parasite taxa. The advancement of non-invasive approaches that integrate parasitological data holds great potential to improve conservation strategies and enhance the ecological understanding of amphibian-parasite interactions.

Heartwater is a tick-borne disease (TBD) of wild and livestock ruminants that threatens food security and the economy throughout much of Africa. Furthermore, the geographic range of heartwater is expanding and is predicted to continue doing so. Despite this, our understanding of heartwater dynamics lags far behind that of many other TBDs. We are therefore limited in our ability to design effective disease control strategies. In this study, we derive and analyse a mathematical model of heartwater dynamics. We analyse our model to predict the most influential parameters for disease risk, both in terms of new outbreaks and in heartwater-endemic regions. We show that the host-finding efficiency of ticks is the most influential parameter affecting outbreak risk. Also, outbreak risk is highly sensitive to the impact of the heartwater pathogen on tick fitness – a previously unexplored concept for any TBD system. In areas where heartwater is established, we show that disease can be controlled via enzootic stability (prolonged host immunity attained via frequent pathogen exposure). However, the maintenance of enzootic stability was dependent on several ecological and physiological parameters. Regarding practical output, we suggest prioritizing tick control measures during periods when ticks are most active in terms of dispersing towards hosts, so as to mitigate heightened outbreak risk. In addition, given the specificity of conditions required for enzootic stability, we caution against relying solely on enzootic stability for long-term heartwater protection. More broadly, our study highlights important tick life history parameters that have been neglected by previous TBD models.