The aquatic and terrestrial clades of species of Trypanosoma could provide insight into the evolutionary history of the genus, as well as complementary information for biomedical studies of medically and economically important species of Trypanosoma. The ecological interactions and phylogeny of aquatic trypanosomes are currently not well-understood, mostly due to their complex life cycles and a deficiency of data. The species of Trypanosoma from African anuran hosts are of the least understood taxa in the genus. Trypanosomes were collected from South African frogs and subjected to morphological and phylogenetic analyses. This study redescribes Trypanosoma (Trypanosoma) nelspruitense Laveran, 1904 and Trypanosoma (Haematomonas) grandicolor Pienaar, 1962, with morphological and molecular data. The present study aims to create a platform for further future research on African anuran trypanosomes.

Using morphological and molecular studies, the life cycle of Versteria cuja (Cestoda: Taeniidae) was elucidated, involving subterranean rodents (Ctenomyidae) as intermediate hosts, and the lesser grison, Galictis cuja (Mustelidae), as definitive host. Metacestodes (cysticerci and polycephalic larvae) were found mainly in the liver but also in spleen, pancreas, lungs and small intestine of 2 species of tuco-tucos (Ctenomys spp.) from Chubut, Argentina. Identity of the metacestodes with the adult was based primarily on the number, size and shape of rostellar hooks: 40–48 hooks in 2 rows, particularly small (10–16 μm total length by 6–10 μm wide), composed of handle, blade and guard with characteristic shapes. Genetic analysis (cox1 gen mtDNA) performed on metacestodes from both intermediate hosts corroborated their conspecificity with adults of V. cuja from lesser grisons in the same locality. Histopathological study showed the hepatic parenchyma altered by the presence of cysts containing larvae, each surrounded by a capsule of connective tissue with inflammatory infiltrate, atrophied hepatocytes and an increase of bile ducts. In the lung, in addition to the cysts, dilated alveoli, oedema and hyperaemic blood vessels were observed. This is the first report of a natural life cycle of a Versteria species from South America. It shows strong similarities with that described for a North American zoonotic lineage of Versteria, confirming a close relationship between V. cuja and this North American lineage, as previously demonstrated by molecular studies. Consequently, the zoonotic potential of V. cuja should not be disregarded.

Haemosporidia (Apicomplexa, Haemosporida) are protozoa that infect vertebrate blood cells and are transmitted by vectors. Among vertebrates, birds possess the greatest diversity of haemosporidia, historically placed in 3 genera: Haemoproteus, Leucocytozoon and Plasmodium, the causative agent of avian malaria. In South America, existing data on haemosporidia are spatially and temporally dispersed, so increased surveillance is needed to improve the determination and diagnosis of these parasites. During the non-breeding season in 2020 and 2021, 60 common terns (Sterna hirundo) were captured and bled as part of ongoing research on the population health of migratory birds on the Argentinian Atlantic coast. Blood samples and blood smears were obtained. Fifty-eight samples were screened for Plasmodium, Haemoproteus and Leucocytozoon, as well as for Babesia parasites by nested polymerase chain reaction and by microscopic examination of smears. Two positive samples for Plasmodium were found. The cytochrome b lineages detected in the present study are found for the first time, and are close to Plasmodium lineages found in other bird orders. The low prevalence (3.6%) of haemoparasites found in this research was similar to those reported for previous studies on seabirds, including Charadriiformes. Our findings provide new information about the distribution and prevalence of haemosporidian parasites from charadriiforms in the southernmost part of South America, which remains understudied.

Waddycephalus is an understudied genus of pentastomids native to Australia and south-east Asia. The genus was recognized in 1922 but there has been little research on these pentastomid tongue worms over the last century. A few observations suggest a complex life cycle through 3 trophic levels. We aimed to add knowledge to the Waddycephalus life cycle in woodland habitats in the Townsville region of north-east Australia. We used camera trapping to identify the most likely first-intermediate hosts (coprophagous insects), we conducted gecko surveys to identify multiple new gecko intermediate host species and we dissected road-killed snakes to identify additional definitive hosts. Our study paves the way for further research into the intriguing life cycle of Waddycephalus, investigation of spatial variation in prevalence and impacts of the parasite on host species.

Soil-transmitted nematodes (STNs) place a tremendous burden on health and economics worldwide with an estimate of at least 1.5 billion people, or 24% of the population, being infected with at least 1 STN globally. Children and pregnant women carry the heavier pathological burden, and disease caused by the blood-feeding worm in the intestine can result in anaemia and delays in physical and intellectual development. These parasites are capable of infecting and reproducing in various host species, but what determines host specificity remains unanswered. Identifying the molecular determinants of host specificity would provide a crucial breakthrough towards understanding the biology of parasitism and could provide attractive targets for intervention. To investigate specificity mechanisms, members of the hookworm genus Ancylostoma provide a powerful system as they range from strict specialists to generalists. Using transcriptomics, differentially expressed genes (DEGs) in permissive (hamster) and non-permissive (mouse) hosts at different early time points during infection with A. ceylanicum were examined. Analysis of the data has identified unique immune responses in mice, as well as potential permissive signals in hamsters. Specifically, immune pathways associated with resistance to infection are upregulated in the non-permissive host, providing a possible protection mechanism that is absent in the permissive host. Furthermore, unique signatures of host specificity that may inform the parasite that it has invaded a permissive host were identified. These data provide novel insight into the tissue-specific gene expression differences between permissive and non-permissive hosts in response to hookworm infection.

Nile × blue tilapia hybrid (Oreochromis niloticus × O. aureus) has become an important food fish in intensive freshwater aquaculture. Recently, the parasite Myxobolus bejeranoi (Cnidaria: Myxozoa) was found to infect hybrid tilapia gills at high prevalence, causing immune suppression and high mortality. Here, we explored additional characteristics of M. bejeranoi–tilapia interaction, which enable efficient proliferation of this parasite inside its specific host. Highly sensitive quantitative polymerase chain reaction (qPCR) and in situ hybridization analyses of fry collected from fertilization ponds provided evidence to an early-life infection of fish by a myxozoan parasite, occurring less than 3 weeks post-fertilization. Because Myxobolus species are highly host-specific, we next compared infection rates in hybrid tilapia and in both its parental species following a 1-week exposure to infectious pond water. Analysis by qPCR and histological sections showed that while blue tilapia was as susceptible to M. bejeranoi as the hybrid, Nile tilapia appeared to be resistant. This is the first report of differential susceptibility of a hybrid fish vs its parental purebreds to a myxozoan parasite. These findings advance our understanding of the relationship between M. bejeranoi and tilapia fish and raise important questions regarding the mechanisms that allow the parasite to distinguish between very closely related species and to infect a specific organ at very early-life stages.

Cryptosporidium spp. are significant opportunistic pathogens causing diarrhoea in humans and animals. Pigs are one of the most important potential hosts for Cryptosporidium. We evaluated the prevalence of Cryptosporidium in pigs globally using published information and a random-effects model. In total, 131 datasets from 36 countries were included in the final quantitative analysis. The global prevalence of Cryptosporidium in pigs was 16.3% (8560/64 809; 95% confidence interval [CI] 15.0–17.6%). The highest prevalence of Cryptosporidium in pigs was 40.8% (478/1271) in Africa. Post-weaned pigs had a significantly higher prevalence (25.8%; 2739/11 824) than pre-weaned, fattening and adult pigs. The prevalence of Cryptosporidium was higher in pigs with no diarrhoea (12.2%; 371/3501) than in pigs that had diarrhoea (8.0%; 348/4874). Seven Cryptosporidium species (Cryptosporidium scrofarum, Cryptosporidium suis, Cryptosporidium parvum, Cryptosporidium muris, Cryptosporidium tyzzeri, Cryptosporidium andersoni and Cryptosporidium struthioni) were detected in pigs globally. The proportion of C. scrofarum was 34.3% (1491/4351); the proportion of C. suis was 31.8% (1385/4351) and the proportion of C. parvum was 2.3% (98/4351). The influence of different geographic factors (latitude, longitude, mean yearly temperature, mean yearly relative humidity and mean yearly precipitation) on the infection rate of Cryptosporidium in pigs was also analysed. The results indicate that C. suis is the dominant species in pre-weaned pigs, while C. scrofarum is the dominant species in fattening and adult pigs. The findings highlight the role of pigs as possible potential hosts of zoonotic cryptosporidiosis and the need for additional studies on the prevalence, transmission and control of Cryptosporidium in pigs.