Global warming is widely recognized as a key driver of current and future changes in marine ecosystems. Parasitic trematodes are highly sensitive to temperature changes, which can lead to drastic impacts on surrounding communities. Copiatestes spp. (Family Syncoelidae) are relatively little-known trematodes with atypical life cycles that have been associated with a mass mortality event of seabirds in the Chatham Islands. As they forage at sea, seabirds get their legs tangled with the sticky, free-living infective stages of Copiatestes, which impairs their ability to take off and land. We tested the impact of seasonally fluctuating sea temperature on the dynamics of Copiatestes thyrsitae at various life stages (infecting second-intermediate host, Nyctiphanes australis euphausiid, and the third free-living infective stage in the water column) by sampling plankton biweekly for 12 months in Otago Harbour, New Zealand. We reveal that higher temperatures are significantly correlated with increases in prevalence and abundance of Copiatestes infections in euphausiids, with a rapid response observed within days to weeks following temperature increases. No correlation was observed between temperature and abundance of free-living stages. Infected euphausiids were smaller in size compared to uninfected individuals. The higher infection levels in euphausiids following warmer temperatures suggest a heightened risk of entanglement for coastal seabirds at these times. Smaller-bodied, surface-feeding seabird species that consume euphausiids are particularly at risk of entanglement. Our findings suggest that even short-term heatwaves can lead to higher risk of seabirds being entangled with Copiatestes filaments, with potentially dire ecological consequences during mass parasite releases.

The Liolopidae Dollfus, 1934 is a small family of digenetic trematodes with sexual adults parasitic in aquatic reptiles and amphibians. Liolopids exploiting snakes are constrained to Harmotrema Nicoll, 1914, but the genus includes species with presumably freshwater life cycles parasitic in terrestrial snakes as well as species with presumably marine life cycles parasitic in viviparous sea snakes and amphibious kraits. We hypothesize that this ecological distinction implies substantial separation in evolutionary history and propose Sagaratrema De Silva, Pathirana & Martin n. g. to accommodate the liolopids in marine snakes. Three species are delineated through an integrated approach, from novel collections of viviparous sea snakes in Sri Lanka, Sagaratrema rajapaksei De Silva, Pathirana & Martin n. sp., Sagaratrema rajakarunae De Silva, Pathirana & Martin n. sp. and Sagaratrema indicum (Chattapadhyaya, 1970) n. comb. (= H. indica) originally reported from India. Three other species known from marine snakes are transferred from Harmotrema to the new genus: S. laticaudae (Yamaguti, 1933) n. comb. (designated as the type-species), S. eugari (Tubangui & Masilungan, 1936) n. comb. and S. linguiforme (Wang, 1987) n. comb. (= H. linguiforme). The 3 species from Sri Lanka are similarly genetically distinct in sympatry as each is relative to S. laticaudae from Japan. Following these proposals, Harmotrema is revised and rendered monotypic for the type-species H. infecundum. Morphologically, Sagaratrema is distinguished from Harmotrema and other liolopid genera by the arrangement of the excretory vesicles, distribution of the vitellarium and size and shape of the body.

A fossil assigned to the extant ixodid genus Haemaphysalis was previously described from the Late Cretaceous (ca. 99 Ma) Burmese amber. Haemaphysalis (Alloceraea) cretacea was considered the oldest, and only, fossil representative of this genus. Significant criticism was raised regarding possible misidentification of this amber fossil. Microtomography of the original holotype and new material allows new perspectives on this controversy. A new fossil nymph is described and both fossils are considered Alloceraea cretacea comb. nov. nymphs based on a series of morphological characters: no genital aperture, eyeless, 11 festoons, coxa I simple with a short, wide triangular spur. Specific morphological features for the ‘structurally primitive’ Alloceraea are discussed and include palpi elongate, with long setae on palps, the hypostome dorsally longer than the chelicera and the corona visible distally and with a specific distribution of the denticles. Alloceraea and its sister genus Archaeocroton (that includes amber fossil taxa), share a common ancestor with Haemaphysalis sensu stricto, indicating a minimum divergence time of at least 100 MYA for these lineages. In addition, a fossil of Bothriocroton has also been described from Burmese amber. This genus with Cryptocroton groups basal to the Alloceraea/Archaecroton-Haemaphysalis assemblage forming a monophyletic clade named Haematobothrion. A synthesis of the fossil information and the current systematic understanding of the Haematobothrion allows new hypotheses about the origins of this group and the various lineages it comprises. Notably that the major Haematobothrion lineages originated and diverged during the time period when the Burma terrane was migrating from Australia to Asia.

Naegleria fowleri, Acanthamoeba spp., Balamuthia mandrillaris and Sappinia spp. are free-living amoebae that can infect humans and cause serious disease; therefore, these organisms are commonly referred to as pathogenic free-living amoebae (pFLA). Diagnosis and treatment of pFLA infections have historically been very challenging. If a diagnosis is made, treatment regimens currently include a combination of antifungals, antimicrobials and anticancer agents that have, to date, proven to be of little help in resolving the disease. Discovery of new therapies is critical to reduce the >90% mortality rate for the brain infections that these microbes can cause. Molecular tools that allow for the study of gene function, generation of reporter cell lines and drug target validation would greatly improve drug discovery efforts. To date, transfection approaches for use with pFLA have been limited, hindering these types of molecular studies. Based on sequence comparisons, the pFLA harbour proteins that are involved in cargo delivery to the nucleus and DNA repair mechanisms, suggesting that fundamental pathways believed to be required for stable transfection are present. However, the amoebae lack homologs to genes connected to stable maintenance of transgenes and RNA interference in other systems. While these differences may limit our ability to alter gene expression, it is also possible that unrecognized components fulfill the roles of the missing homologs. Given the value of robust transfection approaches in drug discovery and gene function studies, resolving these mechanisms would be impactful, leading to improved understanding of amoebae biology and enhancement of drug discovery efforts.

Ricinid lice are exceptionally large-bodied relative to their hosts and tend to form small infrapopulations. They exhibit a more pronounced female bias (predominance of females) than most other lice. Sex ratios (SRs; the proportions of males) of 10 hummingbird-ricinid species pairs collected from South and North America were examined. There was a significant positive relationship between infrapopulation size and SR in 5 cases, and similar non-significant tendencies in 4 cases. Two formerly constructed hypotheses had been considered to explain this relationship. First, Wolbachia infections may account for the female bias, but male aggression during mating could elevate female mortality resulting in higher male proportions in large infrapopulations. Second, the Local Mate Competition (LMC) Hypothesis predicts that highly inbred infrapopulations should exhibit female-biased SRs. Small infrapopulations are likely to be inbred because of stronger genetic drift and are also more likely to originate from single infestations. Conversely, multiple infestations can generate larger and more outbred infrapopulations that are less affected by genetic drift, leading to a shift towards more balanced SRs. This results in a positive correlation between infrapopulation size (infestation intensity) and SR. Both hypotheses provide explanation for the positive association between infestation intensity and the proportion of males, although the LMC aligns more strongly with the actual values of the observed SR bias. Notably, the former hypothesis refers to the physiological mechanism, whereas the latter refers to the adaptive value of the SR bias. These 2 hypotheses are not mutually exclusive.

Environmental change can impact host–parasite interactions, but the effects of multiple stressors on parasites are rarely measured. Considering stressor interactions may allow parasitologists to evaluate how parasite burdens change in nature, where stressors rarely occur in isolation. This study aimed to understand how combined stressors such as warming, nutrients and pollution (i.e. metal concentrations) influence myxozoan prevalence and abundance in the Pearl River, Louisiana, USA. Fish were seined between 1963 and 2005 upstream and downstream of a pulp-mill outfall and were then preserved and accessioned into the Royal D. Suttkus Fish Collection of the Tulane University Biodiversity Research Institute. In 2024, we dissected 1188 fish individuals across 7 host species, and we identified myxozoans in 6 species. Six myxozoan genera were detected, including Chloromyxum, Henneguya, Myxidium, Myxobolus, Thelohanellus and Unicauda, with some novel host–parasite combinations. The abundance of Myxobolus infecting Carpiodes velifer gills declined by 86% over the study period, while the abundance of Myxobolus infecting Pimephales vigilax gills was significantly lower downstream of the pulp mill outfall. Among the drivers analyzed, temperature had a significant negative effect on this parasite’s abundance, metal concentrations had a positive effect, and these 2 drivers interacted. Our results highlight the differential susceptibility of wild fishes to myxozoan infections and the usefulness of museum collections for understanding historical change in myxozoan burdens in fish. Since stressor-driven changes in myxozoan abundance do not follow a single pattern across species, we expect a shift in freshwater myxozoan communities with progressing climate change and pollution.

Host–parasite coevolution resulted in parasites optimizing their life cycle to obtain the most benefit from the host’s behaviour. In passerines, for instance, some parasite groups have found means to match their egg shedding rhythms with the hours of the day when hosts are most active. In other bird groups, such as shorebirds, whose active times are not determined by day–night cycles but by other external factors such as tidal or lunar cycles, it is not yet known whether their endoparasites exhibit any predictable pattern in their egg shedding rhythms. Here we used a simple wild-caught (captive) system, to provide a first approximation of the parasite egg shedding patterns in wintering Rufous-chested dotterels (Zonibyx modestus). We collected faeces every 2 hours over 10 days until completing a 24-hour cycle, which was coupled with continuous video recordings to determine their feeding and drinking habits. Contrary to our expectation, we showed that parasite egg shedding followed a cyclic pattern, characterized by 2 peaks: one at midnight and another in the afternoon. Importantly, this shedding pattern was not related to the birds’ feeding or drinking habits. We discuss possible environmental and physiological cues that parasites might use to trigger egg production, including the potential influence of tidal cycles on our results.

Bat flies (Diptera: Nycteribiidae and Streblidae) are obligate blood-feeding ectoparasites of bats and are increasingly recognised for their potential role in host-specific co-evolution and disease transmission. Despite their ecological importance, the diversity, host associations and evolutionary relationships of bat flies in Australia remain poorly characterised. This study provides the first integrative assessment of nycteribiid bat flies parasitising Pteropus species in North Queensland, combining morphological taxonomy with cytochrome c oxidase subunit 1 (COX1) sequencing and phylogenetic analysis. A total of 304 bat flies were collected from 79 rescued pteropodids, representing three host species: the little red flying fox (Pteropus scapulatus), the black flying fox (Pteropus alecto) and the spectacled flying fox (Pteropus conspicillatus). Morphological examination of the bat flies identified two taxa, Cyclopodia australis and Cyclopodia albertisii, which were further confirmed by maximum likelihood phylogenetic analysis of COX1 sequences with distinct clade formations delineating species. C. australis was found almost exclusively on little red flying foxes. C. albertisii was mainly associated with both black flying foxes and spectacled flying foxes, with very limited association with the little red flying foxes. These findings underscore the utility of integrative taxonomic approaches in researching bat fly diversity and host specificity. They also highlight the potential for co-evolutionary divergence and emphasise the need for expanded geographic sampling and genomic analysis. This research provides critical baseline data for understanding ectoparasite biodiversity in Australia and contributes to future studies of host–parasite interaction, vector ecology and wildlife disease surveillance.

Chagas disease (CD) is a neglected tropical disease caused by the protozoan parasite Trypanosoma cruzi affecting more than 6 million people worldwide. Its treatment is based in old and toxic nitroderivative drugs necessitating for new alternatives. Imatinib (IMB) is a tyrosine kinase inhibitor used in cancer therapy, and previous reports demonstrate that some derivatives are active against T. cruzi justifying further synthesis screening of novel compounds derived from IMB. Our results demonstrate that all test derivatives are highly active against the intracellular forms of T. cruzi being similar or even more potent than the reference drug for CD – benznidazole (BZ). Besides, they were much more active than the parent molecule, displaying low EC90 values (<10 µm) and good selectivity indexes (>10), which are relevant characteristics of a novel hit compound for CD therapy. However, when screened against bloodstream trypomastigotes, only 1 derivative, named PLDC 23/19, was as active (EC50 = 18.8 µm) as BZ (EC50 = 18.8 µm), while the others did not show activity up to 20 µm.

Giardiasis remains a significant global health burden, constrained by limited diagnostic tools, the emergence of drug-resistant Giardia lamblia strains, and the absence of a licenced human vaccine. To address these critical gaps, this review provides a comprehensive functional analysis of the Giardia proteome, emphasizing molecular targets essential for the parasite’s survival and pathogenesis. We systematically examine the structural proteome, specifically the tubulin reservoir and the diverse giardin family (α-, β-, γ- and δ-giardins), elucidating their indispensable roles in the ventral disc attachment mechanism. Beyond structural components, we detail the ‘pathoproteome’, and moonlighting enzymes, highlighting how the secretome – including cathepsin B-like cysteine proteases (notably giardipain-1) and variant-specific surface proteins facilitate immune evasion and host intestinal epithelial damage. Furthermore, the review explores the metabolic and encystation proteomes, identifying unique enzymes such as carbamate kinase and fructose 1,6-bisphosphate aldolase that offer high therapeutic selectivity. By synthesizing these proteomic insights, this work identifies high-priority candidates for the development of next-generation therapeutics, prophylactic, and diagnostic interventions aimed at mitigating the global impact of this neglected disease.

Dientamoeba fragilis transmission is a basic aspect of this intestinal parasite’s biology that is poorly understood. Early historical reports reflecting the absence of a cyst are often cited as a central argument in debates supporting the lack of a D. fragilis cyst. While D. fragilis cysts have been described since Dobell’s original description, their existence is not universally accepted. Here, Dobell’s, Wenyon’s and Hoare’s collection of historical faecal smears stored at the Natural History Museum (London), dating back to the 1890s and the early 1900s, was examined for forms consistent with modern descriptions of D. fragilis cysts, and an example was found in 1 slide. Such rare forms were also detected during examination of stained faecal smears archived in the parasite reference laboratory collection at the United States Centers for Disease Control and Prevention. We discuss these observations in the context of literature describing cyst formation in parabasalids. Additionally, we report some incidental findings from past immunofluorescence experiments on cultured D. fragilis, which suggest differential staining that appears to correlate with life cycle stages. Considering published literature on the subject of D. fragilis cysts and the broader picture of cyst formation across diverse members of Parabasalia, we recommended that future investigations on D. fragilis transmission consider mounting evidence for the role of a true cyst despite its rarity in human faecal specimens. The factors leading to cyst formation and further characteristics of this life cycle stage require further study.