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We describe a case of imported ocular dirofilariasis in Australia, linked to the Hong Kong genotype of Dirofilaria sp., in a migrant from Sri Lanka. Surgical extraction and mitochondrial sequences analyses confirmed this filarioid nematode as the causative agent and a Dirofilaria sp. not previously reported in Australia.

Background Enterocytozoon bieneusi is one of the commonest microsporidians contributing to human microsporidiosis, and is frequently found in animals in various countries. However, there is limited epidemiological information on this microorganism in Australia. Here, we undertook the first molecular epidemiological study of E. bieneusi in cats and dogs in Victoria. Results Genomic DNAs were extracted from 514 individual faecal deposits from cats ( n  = 172) and dogs ( n  = 342) and then tested using PCR-based sequencing of the internal transcribed spacer ( ITS ) of nuclear ribosomal DNA. Four distinct genotypes (designated D, PtEb IX, VIC_cat1 and VIC_dog1) of E. bieneusi were identified in 20 of the 514 faecal samples (3.9%). Genotype D is known to have a broad host range (humans and other animals) and has a wide geographical distribution around the world. The identification of this genotype here suggests that companion animals might represent reservoir hosts that are able to transmit E. bieneusi infection to humans in Australia. A phylogenetic analysis of ITS sequence data revealed that the novel genotype VIC_cat1 is related to the known genotype type IV within Group 1, and the new genotype VIC_dog1 is linked to a contentious “Group 3”, which includes genotypes reported previously in the published literature to represent Group 2 or 3. Conclusions A future, large-scale phylogenetic study of all known E. bieneusi genotypes, including VIC_dog1, should aid in clarifying their relationships and assignment to Groups, and in the identification of new genotypes, thus assisting epidemiological investigations.

Trichinellosis is a globally important food-borne parasitic disease of humans caused by roundworms of the Trichinella complex. Extensive biological diversity is reflected in substantial ecological and genetic variability within and among Trichinella taxa, and major controversy surrounds the systematics of this complex. Here we report the sequencing and assembly of 16 draft genomes representing all 12 recognized Trichinella species and genotypes, define protein-coding gene sets and assess genetic differences among these taxa. Using thousands of shared single-copy orthologous gene sequences, we fully reconstruct, for the first time, a phylogeny and biogeography for the Trichinella complex, and show that encapsulated and non-encapsulated Trichinella taxa diverged from their most recent common ancestor ∼21 million years ago (mya), with taxon diversifications commencing ∼10−7 mya. Trichinellosis is a globally important food-borne disease caused by roundworms of the Trichinella complex. Here the authors present genomic sequences representing all 12 recognized Trichinella species and genotypes, and reconstruct their phylogeny and biogeography.

Haemoparasites are responsible for some of the most prevalent and debilitating canine illnesses across the globe, whilst also posing a significant zoonotic risk to humankind. Nowhere are the effects of such parasites more pronounced than in developing countries in the tropics where the abundance and diversity of ectoparasites that transmit these pathogens reaches its zenith. Here we describe the use of a novel next-generation sequencing (NGS) metabarcoding based approach to screen for a range of blood-borne apicomplexan and kinetoplastid parasites from populations of temple dogs in Bangkok, Thailand. Our methodology elucidated high rates of Hepatozoon canis and Babesia vogeli infection, whilst also being able to characterise co-infections. In addition, our approach was confirmed to be more sensitive than conventional endpoint PCR diagnostic methods. Two kinetoplastid infections were also detected, including one by Trypanosoma evansi , a pathogen that is rarely screened for in dogs and another by Parabodo caudatus , a poorly documented organism that has been previously reported inhabiting the urinary tract of a dog with haematuria. Such results demonstrate the power of NGS methodologies to unearth rare and unusual pathogens, especially in regions of the world where limited information on canine vector-borne haemoparasites exist.

Background This study presents findings from a 15-year longitudinal surveillance program (2009–2024) monitoring Cryptosporidium and Giardia in protected drinking water catchments in Melbourne and environs in the State of Victoria, Australia. As one of the few major cities worldwide sourcing largely unfiltered water from forested catchments, Melbourne presents a unique opportunity to assess the occurrence and prevalence of protozoan parasites in a minimally disturbed ecosystem. Methods A total of 14,960 animal faecal samples were analysed using polymerase chain reaction (PCR)-based sequencing, including 8695 samples collected over the past 9 years. Results Cryptosporidium was detected in 3.15% of samples and Giardia in 0.16%. A total of 12 recognised Cryptosporidium species and genotypes were identified, nine of which have known zoonotic potential, as well as two sub-assemblages (AI and AIII) of Giardia duodenalis , including four novel assemblage AI variants. Parasite diversity was the highest in eastern grey kangaroos, which hosted at least 18 Cryptosporidium variants. Temporal analyses revealed significant inter-annual variation, with peak prevalence during the 2023 La Niña year and seasonal differences by host group. Notably, C. ubiquitum , C. muris and C. occultus were recorded for the first time in these catchments. In spite of the low prevalence of high-risk species such as C. parvum and the absence of C. hominis , the detection of emerging and previously uncharacterised genotypes emphasises the importance of sustained surveillance. Conclusions These findings have broad implications for managing zoonotic risk in unfiltered water systems worldwide. Advances in metagenomics and high-throughput sequencing platforms will be critical for enhancing future pathogen monitoring and catchment management strategies in the context of increasing climate and environmental pressures. Graphical Abstract

This study presents the first detection of Taenia omissa metacestodes in guanaco ( Lama guanicoe ) within the Chilean Patagonia, marking the southernmost record of natural infection in an intermediate host on the continent. Taenia omissa was found in the continental part of the Magallanes region where the top predators are pumas ( Puma concolor ). Conversely, all metacestodes found in guanacos collected from Tierra del Fuego Island, where no pumas exist, were identified solely as Echinococcus granulosus sensu stricto . Additionally, this research highlights a tissue preference of T. omissa for liver, contrasting with E. granulosus , which predominantly affects the lungs in guanacos. We also report the infection of T . pisiformis in 1 guanaco. Our findings emphasize the need for accurate identification of metacestodes during meat inspection in an area where T. omissa and E. granulosus overlap. This research also contributes to increase the knowledge of parasite–host dynamics in wildlife and underscores the importance of considering broader spectrum intermediate hosts in the epidemiology of parasitic infections.

Background The protistan pathogens Cryptosporidium and Giardia can cause significant intestinal diseases in animals and humans. Cattle, particularly calves, carrying these protists can be significant reservoirs for human infections and disease. However, little is known about the genetic make-up of Cryptosporidium and Giardia populations in cattle and other ruminants in some regions of China. Results In the present study, PCR-based tools were used to genetically characterise these protists in faecal samples from a total of 339 pre- and post-weaned calves from four distinct locations in Hubei Province using markers in the large ( LSU ) or small ( SSU ) subunits of nuclear ribosomal RNA genes. Cryptosporidium andersoni , C. bovis , C. ryanae and Giardia duodenalis assemblage E were detected in 0.6%, 10.9%, 4.1% and 22.6% of calves, respectively. Conclusions This study is the first to report the prevalence of Cryptosporidium and Giardia in pre- and post-weaned calves in Hubei Province, and encourages large-scale molecular studies of animals and humans, in an effort to better understand the epidemiology of these enteric pathogens in China.

Background Cryptosporidium is a key genus of parasitic protists that infect humans and other vertebrates (mammals and birds). Birds are typically infected with C. avium , C. baileyi , C. galli and/or C. meleagridis , the latter of which is recognised as being zoonotic. Stimulated by the previous finding of C. meleagridis subtypes IIIbA21G1R1, IIIbA22G1R1 and IIIbA26G1R1 in diarrhoeic children in Wuhan city and environs in Hubei Province, China, we performed a molecular epidemiological survey to explore whether these or similar subtypes might occur in farmed chickens in this province. Methods PCR-coupled sequencing analyses of regions in the small subunit ( SSU ) of the nuclear ribosomal RNA and 60 kDa glycoprotein ( gp60 ) genes were utilised to characterise Cryptosporidium in faecal samples from chickens ( n = 471) from 14 farms from six distinct regions in Hubei Province. Results Cryptosporidium baileyi (33/471; 7.0%) and C. meleagridis (15/471; 3.2%) were identified in chickens on eight farms in five of the six distinct geographical regions. No significant age-associated difference in the prevalence of C. baileyi was evident, whereas the prevalence of C. meleagridis was significantly higher in younger (≤ 4 months) than in older chickens (> 4 months). For C. meleagridis , two subtype families, IIIb and IIIe, were defined; some of the subtypes (i.e. IIIbA26G1R1b and IIIbA22G1R1c) characterised here matched those identified previously in diarrhoeic children in Wuhan. Conclusions This is the first molecular study reporting the genetic identity and prevalence of C. baileyi and C. meleagridis in chickens in Hubei. The findings suggest that C. meleagridis subtypes IIIbA26G1R1b and IIIbA22G1R1c are cross-transmissible between chickens and humans, raising awareness about the significance of birds as potential reservoirs of zoonotic variants of Cryptosporidium. Future studies might focus on investigating the prevalence of ‘zoonotic’ subtypes of Cryptosporidium meleagridis in various species of wild and domesticated birds, and on comparing them with those found in humans in China and other countries.

Background Fasciola hepatica , the causative agent of fascioliasis in sheep and cattle, requires a compatible snail intermediate host to complete its life cycle. The aquatic larval stage of this parasite is well-adapted for host-finding, with chemotactic abilities that enable it to sense potential host biomolecules. The extent of intermediate host recognition, particularly at the species level, and the downstream correlation with successful attachment has not been explored. This study investigated the ability of F. hepatica miracidia to distinguish between native and invasive host and non-host freshwater snail species during the host-finding and host-attachment phases. Methods Quantitative and qualitative measurements of miracidial behaviour were compared pre- and post-exposure with snail-conditioned water (SCW) from both native and invasive host snails (lymnaeids Austropeplea cf. brazieri and Pseudosuccinea columella ) and non-host snails (the lymnaeid Bullastra lessoni and the physid Physa acuta ). Miracidia were also exposed to live snails of each representative species to ascertain whether host-finding correlates with successful miracidial host-attachment. Results Miracidia displayed clear shifts in movement profiles post-exposure to SCW, with no qualitative or quantitative differences observed in the behavioural response to different snail species. When exposed to live snails, miracidia were more likely to attach to both host and non-host native species ( A. cf. brazieri and B. lessoni ) compared with invasive snail species ( P. columella and P. acuta ). Among invasive snails, miracidia had a higher rate of successful attachment with P. columella (host) than with P. acuta (non-host). Conclusions The miracidia of F. hepatica exhibit analogous host-finding responses post-exposure to SCW, regardless of which snail species they are exposed to. Host-finding responses do not correlate with miracidial ability to attach to the snail tissue or with the established host status of the respective snail species. These results provide an insight into host-finding preferences of F. hepatica within the Australian context and lay an important foundation for further exploration into intermediate host–parasite interactions and their mechanisms of action. Graphical Abstract

Background Globally, bacterial vector-borne disease (VBD) exerts a large toll on dogs in terms of morbidity and mortality but nowhere is this more pronounced than in the tropics. Tropical environments permit a burgeoning diversity and abundance of ectoparasites some of which can transmit an extensive range of infectious agents, including bacteria, amongst others. Although some of these vector-borne bacteria are responsible for both animal and human diseases in the tropics, there is a scarcity of epidemiological investigation into these pathogens’ prevalence. The situation is further exacerbated by frequent canine co-infection, complicating symptomatology that regular diagnostic techniques may miss or be unable to fully characterise. Such limitations draw attention to the need to develop screening tools capable of detecting a wide range of pathogens from a host simultaneously. Results Here, we detail the employment of a next-generation sequencing (NGS) metabarcoding methodology to screen for the spectrum of bacterial VBD that are infecting semi-domesticated dogs across temple communities in Bangkok, Thailand. Our NGS detection protocol was able to find high levels of Ehrlichia canis , Mycoplasma haemocanis and Anaplasma platys infection rates as well as less common pathogens, such as “ Candidatus Mycoplasma haematoparvum”, Mycoplasma turicensis and Bartonella spp. We also compared our high-throughput approach to conventional endpoint PCR methods, demonstrating an improved detection ability for some bacterial infections, such as A. platys but a reduced ability to detect Rickettsia . Conclusions Our methodology demonstrated great strength at detecting coinfections of vector-borne bacteria and rare pathogens that are seldom screened for in canines in the tropics, highlighting its advantages over traditional diagnostics to better characterise bacterial pathogens in environments where there is a dearth of research.