Helminth zoonoses remain a global problem to public health and the economy of many countries. Polymerase chain reaction-based techniques and sequencing have resolved many taxonomic issues and are now essential to understanding the epidemiology of helminth zoonotic infections and the ecology of the causative agents. This is clearly demonstrated from research on Echinococcus (echinococcosis) and Trichinella (trichinosis). Unfortunately, a variety of anthropogenic factors are worsening the problems caused by helminth zoonoses. These include cultural factors, urbanization and climate change. Wildlife plays an increasingly important role in the maintenance of many helminth zoonoses making surveillance and control increasingly difficult. The emergence or re-emergence of helminth zoonoses such as Ancylostoma ceylanicum, Toxocara, Dracunculus and Thelazia exacerbate an already discouraging scenario compounding the control of a group of long neglected diseases.

To best understand parasite, host, and vector morphologies, host-parasite interactions, and to develop new drug and vaccine targets, structural data should, ideally, be obtained and visualised in three dimensions (3D). Recently, there has been a significant uptake of available 3D volume microscopy techniques that allow collection of data across centimetre (cm) to Angstrom (& ANGS;) scales by utilising light, X-ray, electron, and ion sources. Here, we present and discuss microscopy tools available for the collection of 3D structural data, focussing on electron microscopy-based techniques. We highlight their strengths and limitations, such that parasitologists can identify techniques best suited to answer their research questions. Additionally, we review the importance of volume microscopy to the advancement of the field of parasitology.

Invasive wild mammals are present in all continents, with Europe, North America, and the Asian-Pacific region having the largest number of established species. In particular, Europe has been the continent with the highest number of zoonotic parasites associated with invasive wild mammals. These invasive species may represent a major threat for the conservation of native ecosystems and may enter in the transmission cycle of native parasites, or act as spreaders of exotic parasites. Here, we review the role of invasive wild mammals as spreaders of zoonotic parasites, presenting important examples from Europe, America, and the Asia-Pacific region. Finally, we emphasize the need for more research on these mammals and their parasites, especially in areas where their monitoring is scantily performed.

Giardia duodenalis, Giardia enterica, Giardia intestinalis and Giardia lamblia are the synonyms for a species complex of 8-11 phylogenetically distinct species of Giardia infecting a broad range of animals including humans. Retrospective alignment of 8409 gene sequences from 3 loci confirmed host associations of Assemblages and sub-Assemblages within this species complex and molecular species delimitation testing confirmed that the Assemblages and sub-Assemblages AI and AII should be recognised as distinct species. It is recommended to synonymise the Assemblages with historic species descriptions based on host associations and consider descriptions for new species where no corresponding description exists. Synonyms, Giardia duodenalis, Giardia intestinalis and Giardia enterica, to be removed from synonymy: synonymise "Giardia duodenalis-Assemblage AI" syn. n. to Giardia duodenalis (Davaine, 1875), Kofoid and Christansen, 1915, synonymise "Giardia duodenalis-Assemblage AII" syn. n. to Giardia intestinalis (Lambl, 1859; Blanchard, 1885), Alexeieff, 1914 and synonymise "Giardia duodenalis-Assemblage B" syn. n. to Giardia enterica (Grassi, 1881), Kofoid, 1920. Host specific Assemblages synonymised: synonymise canid-associated "Giardia duodenalis-Assemblage C" syn. n. to Giardia canisHegner, 1922; synonymise artiodactyl-associated "Giardia duodenalis-Assemblage E" syn. n. to Giardia bovisFantham, 1921; synonymise feline-associated "Giardia duodenalis-Assemblage F" syn. n. to Giardia catiDeschiens, 1925; and synonymise rodent-associated "Giardia duodenalis-Assemblage G" syn. n. to Giardia simoniLavier, 1924. New description for parasite type infecting specific host: canid-associated "Giardia duodenalis-Assemblage D" named Giardia lupus, sp. n. (LSID: urn:lsid:zoobank.org:act:1651A8CB-CBA8-40D9-AB59-D4AB11AC18A3). New proposed names and descriptions for consideration for parasite types infecting specific hosts: cervid-associated "Giardia duodenalis-sub-Assemblage AIII" for consideration "cervus" and Pinnipedia-associated "Giardia duodenalis-Assemblage H" for consideration "pinnipedis".

Lamb survival is an important welfare and productivity issue for sheep industries worldwide. Lower lamb survival has been reported for primiparous ewes, but the causes of this are not well studied. The aim of this study was to determine causes of perinatal deaths for lambs born to primiparous ewes in Western Australia, and identify if infectious diseases are implicated. Lamb mortality from birth to marking were determined for 11 primiparous ewe flocks on 10 farms in Western Australia. Lamb mortality from birth to marking averaged 14% for single-born and 26% for multiple-born lambs. Lamb necropsies ( n = 298) identified starvation–mismosthering–exposure (34%), dystocia (24%) and stillbirth (15%) as the most common causes of perinatal lamb death. There was no evidence of exotic abortigenic pathogens in aborted and stillborn lambs ( n = 35). Chlamydia pecorum was detected by qPCR in 15/35 aborted and stillborn lambs on 5/6 farms. Preliminary molecular characterisation of C. pecorum detected in samples from aborted and stillborn lambs ( n = 8) using both Multilocus Sequence Typing and omp A genotyping indicated all strains were genetically identical to previously described pathogenic livestock strains, denoted ST23, and dissimilar to gastrointestinal strains. High frequency of detection of a pathogenic C. pecorum strains ST23 associated with ovine abortion and stillbirth on multiple farms located across a wide geographic area has not been previously reported. Chlamydia pecorum may contribute to reproductive wastage for primiparous sheep in Western Australia. Further investigation to understand C. pecorum epidemiology and impact on sheep reproduction is warranted.

A growing number of indigenous trypanosomes have been reported to naturally infect a variety of Australian wildlife with some species of Trypanosoma implicated in the population decline of critically endangered marsupials. However, the mode of transmission of Australian trypanosomes is unknown since their vectors remain unidentified. Here we aimed to fill this current knowledge gap about the occurrence and identity of indigenous trypanosomes in Australian invertebrates by conducting molecular screening for the presence of Trypanosoma spp. in native ticks collected from south-west Australia. A total of 231 ticks (148 collected from vegetation and 83 retrieved directly from 76 marsupial hosts) were screened for Trypanosoma using a High-Resolution Melt (HRM) qPCR assay. An overall Trypanosoma qPCR positivity of 37% (46/125) and 34% (26/76) was detected in questing ticks and host-collected (i.e., feeding) ticks, respectively. Of these, sequencing revealed 28% (35/125) of questing and 28% (21/76) of feeding ticks were infected with one or more of the five species of trypanosome previously reported in this region (T. copemani, T. noyesi, T. vegrandis, T. gilletti, Trypanosoma sp. ANU2). This work has confirmed that Australian ticks are capable of harbouring several species of indigenous trypanosome and likely serve as their vectors.

Tabanids (syn. horse flies) are biting-flies of medical and veterinary significance because of their ability to transmit a range of pathogens including trypanosomes - some species of which carry a combined health and biosecurity risk. Invertebrate vectors responsible for transmitting species of Trypanosoma between Australian wildlife remains unknown, thus establishing the role of potential vector candidates such as tabanids is of utmost importance. The current study aimed to investigate the presence of indigenous trypanosomes in tabanids from an endemic area of south-west Australia. A total of 148 tabanids were collected, with morphological analysis revealing two subgenera: Scaptia (Pseudoscione) and S. (Scaptia) among collected flies. A parasitological survey using an HRM-qPCR and sequencing approach revealed a high (105/148; 71%) prevalence of trypanosomatid DNA within collected tabanids. Individual tissues - proboscis (labrum, labium and mandibles, hypopharynx), salivary glands, proventriculus, midgut, and hindgut and rectum - were also tested from a subset of 20 tabanids (n = 140 tissues), confirming the presence of Trypanosoma noyesi in 31% of screened tissues, accompanied by T. copemani (3%) and T. vegrandis/T.gilletti (5%). An unconfirmed trypanosomatid sp. was also detected (9%) within tissues. The difference between tissues infected with T. noyesi compared with tissues infected with other trypanosome species was statistically significant (p < 0.05), revealing T. noyesi as the more frequent species detected in the tabanids examined. Fluorescence in situ hybridisation (FISH) and scanning electron microscopy (SEM) confirmed intact parasites within salivary glands and the proboscis respectively, suggesting that both biological and mechanical modes of transmission could occur. This study reveals the presence of Australian Trypanosoma across tabanid tissues and confirms intact parasites within tabanid salivary glands and the proboscis for the first time. Further investigations are required to determine whether tabanids have the vectorial competence to transmit Australian trypanosomes between wildlife.

The illegal wildlife trade (IWT) is a criminal practice bringing several ecological and public health consequences, such as the spreading of zoonotic pathogens and/or the introduction of exotic species of animals into new geographical areas. Here, we discuss potential risks of IWT on the spreading and emergence of zoonotic pathogens. IWT as a Threat to Wildlife and Public Health

A forum article aiming to stimulate discussions on the risks of introduction and spreading of infectious diseases through the illegal wildlife trade (IWT) has been recently published [ 1. Bezerra-Santos M.A. et al. Illegal wildlife trade: a gateway to zoonotic infectious diseases. Trends Parasitol. 2021; 37: 181-184 Abstract Full Text Full Text PDF PubMed Scopus (34) Google Scholar ]. A letter by Nijman [ 2. Nijman V. Illegal and legal wildlife trade spreads zoonotic diseases. Trends Parasitol. 2021; (in press) Abstract Full Text Full Text PDF PubMed Scopus (4) Google Scholar ] argued that the majority of the concerns raised in that article (e.g., illegal trade in wet markets, illegal transport of wildlife or their derivatives, illegal importation of exotic pets) apply also to the legal wildlife trade. Though we recognize that it may be risky to emphasize the IWT only, the legal trade, by definition, should be under regulatory laws to reduce the risk of pathogen spread and disease introduction. Illegal and Legal Wildlife Trade Spreads Zoonotic DiseasesVincent NijmanTrends in ParasitologyFebruary 24, 2021In BriefParasites do not read legal documents. They cannot distinguish between animals or animal products that are traded with or without permits. Bezerra-Santos et al. [1] discussed the potential risks that the illegal wildlife trade has on the spreading and emergence of zoonotic pathogens. They highlight open wildlife (‘wet’) markets, the illegal transport of wildlife or their derivatives, as well as the illegal importation of exotic pets and the risk of zoonotic pathogens in the spread and introduction of diseases. Full-Text PDF

Trypanosomes are blood-borne parasites infecting a range of mammalian hosts worldwide. In Australia, an increasing number of novel Trypanosoma species have been identified from various wildlife hosts, some of which are critically endangered. Trypanosoma noyesi is a recently described species of biosecurity concern, due to a close relationship to the South American human pathogen, Trypanosoma cruzi. This genetic similarity increases the risk for introduction of T. cruzi via a local vector. Unfortunately, there is a lack of knowledge concerning the vectorial capacity of Australian invertebrates for native Trypanosoma species. Australian ixodid ticks (Ixodidae), which are widespread ectoparasites of mammalian wildlife, have received the most attention as likely candidates for trypanosome transmission and have been previously implicated as vectors. However, as all studies to date have focused on blood-fed ticks collected directly from infected mammalian hosts, the question of whether ticks maintain a trypanosome infection between blood meals is unknown. In this study, we investigated the presence of Trypanosoma within 148 Australian adult and nymph questing ticks of the species Amblyomma triguttatum, Ixodes australiensis, Ixodes myrmecobii and larvae Ixodes spp., collected from an endemic region of south-west Australia. Using a novel HRM-qPCR detection method that can discriminate between species of Trypanosoma based on primer melting temperature (Tm), we report the first molecular detection of Trypanosoma DNA in Australian questing ticks, with 6 ticks DNA positive for T. noyesi. Additionally, the presence of intact T. noyesi parasites within all (n = 3) smeared gut and gland contents of questing ticks was confirmed using a fluorescence in situ hybridisation (FISH) assay. Whilst this study was unable to determine the in situ tissue location of trypanosomes for the purpose of discerning a potential route of transmission, these combined molecular and FISH smear data indicate that trypanosomes can persist in ticks between blood meals and that ticks are possibly vectors in the transmission of T. noyesi between native wildlife. Transmission experiments are still required to evaluate the competency of Australian ticks as vectors for T. noyesi. Nevertheless, these novel findings warrant further investigation concerning potential life stages and the development of trypanosomes in both Australian, and other, tick species.

Context Proximity sensors were used recently to determine the maternal pedigree of lambs on a small plot with high accuracy. If this accuracy is maintained under commercial grazing conditions, this method could be a useful alternative to improving genetic gain in sheep, including reproduction traits. Aims To investigate using proximity sensors to determine the maternal pedigree of lambs and to define the level of interactions required to determine maternal pedigree confidently irrespective of differences in ewe age, lamb age, birth type, paddock size, flock size or stocking rate under commercial grazing conditions. Methods We compared maternal pedigree determined using the proximity sensors to DNA profiling (n = 10 flocks) and lambing rounds (n = 16 flocks). Ewes (n = 7315) and lambs (n = 8058) were fitted with proximity sensors under normal grazing conditions for each property for 1–3 days. Flocks varied in ewe age (adults, hoggets and ewe lambs), lamb age (up to 100 days old, except for 1 flock), birth type (singles, multiples), paddock size (0.25–320 ha), flock size (37–420 lambs) and stocking rate (2–100 dry sheep equivalents/ha, except for 1 flock). Key results An interaction ratio of >2 was required for a confident ewe–lamb match (ewe with the most interactions compared with the ewe with the second-most interactions for each lamb). Using this criterion, the average success of proximity sensors at matching a lamb to a ewe was 95% and the sensors were 97% accurate when compared with the pedigree results from lambing rounds or DNA. For lambs matched successfully, over 90% of this success was achieved in the first 7 h and over 99% in the first 20 h. While the success rate of matching a lamb to a ewe was not influenced significantly by ewe age, birth type, paddock size, flock size or stocking rate, the time to achieve sensor success was significantly quicker for singles than for twins and sensor accuracy was significantly higher for smaller paddocks with higher stocking rates. Conclusions Our results showed that proximity sensors can establish maternal pedigree effectively and accurately across a range of conditions experienced on commercial properties. Implications Private industry can now develop more cost-effective sensor technologies with greater confidence that will enhance recording of maternal pedigree and, hence, the rate of genetic gain across the sheep industry.

Anthelmintic resistance (AR) has thus far only rarely been reported for intestinal helminths of dogs and cats, in contrast to parasites of livestock and horses. We highlight possible reasons for this striking and important discrepancy, including ecological, biological and genetic factors and/or intervention regimens of key intestinal helminths concerning both host groups. In view of the current knowledge related to the genetics, mechanisms and principles of AR development, we point at issues which in our view contribute to a comparatively lower risk of AR development in intestinal helminths of dogs and cats. Finally, we specify research needs and provide recommendations by which, based on the available information about AR in ruminant and equine helminths, the development of AR in dog and cat helminths may best be documented, prevented or at least postponed.

Phenotypic screening of a 900 compound library of antitubercular nitroimidazole derivatives related to pretomanid against the protozoan parasite Trypanosoma cruzi (the causative agent for Chagas disease) identified several structurally diverse hits with an unknown mode of action. Following initial profiling, a first proof-of-concept in vivo study was undertaken, in which once daily oral dosing of a 7-substituted 2-nitroimidazooxazine analogue suppressed blood parasitemia to low or undetectable levels, although sterile cure was not achieved. Limited hit expansion studies alongside counter-screening of new compounds targeted at visceral leishmaniasis laid the foundation for a more in-depth assessment of the best leads, focusing on both drug-like attributes (solubility, metabolic stability and safety) and maximal killing of the parasite in a shorter timeframe. Comparative appraisal of one preferred lead (58) in a chronic infection mouse model, monitored by highly sensitive bioluminescence imaging, provided the first definitive evidence of (partial) curative efficacy with this promising nitroimidazooxazine class.

Conventional nested PCR and Sanger sequencing methods are currently the gold standards for detecting trypanosomes in wildlife. However, these techniques are time-consuming and can often overlook mixed infections. True trypanosome prevalence can thus be underrepresented. Here, we designed an 18S rDNA-based real-time quantitative PCR (qPCR) assay coupled with High-Resolution Melting Analysis (HRMA) to detect and discriminate three Trypanosoma species (T. copemani, T. noyesi, and T. vegrandis) commonly infecting Australian marsupials. A total of 68 genetically characterised samples from blood and tissue were used to validate the High-Resolution Melting - Real Time Quantitative Polymerase Chain Reaction (HRM-qPCR) assay. A further 87 marsupial samples consisting of blood, tissue and in vitro cultures derived from wildlife blood samples, were screened for the first time using this assay, and species identity confirmed using conventional PCR and Sanger sequencing. All three Trypanosoma species were successfully detected in pure cultures using the HRM-qPCR assay, and in samples containing mixed trypanosome infections. Of the 87 marsupial samples screened using the HRM-qPCR assay, 93.1% were positive for trypanosomes, and 8.0% contained more than one trypanosome species. In addition to the three targeted Trypanosoma species, this assay was also able to detect and identify other native and exotic trypanosomes. The turnaround time for this assay, from sample preparation to obtaining results, was less than 2 h, with a detection limit of 10 copies of the amplicon in a reaction for each of the targeted trypanosome species. This more rapid and sensitive diagnostic tool provides a high throughput platform for the detection, identification and quantification of trypanosome infections. It will also improve understanding of host diversity and parasite relationships and facilitate conservation management decisions.

Population genetic studies of Trichomonas vaginalis have detected high genetic diversity associated with phenotypic differences in clinical presentations. In this study, microscopy and next generation-multi-locus sequence typing (NG-MLST) were used to identify and genetically characterise T. vaginalis isolates from patients in Australia and Ghana. Seventy-one polymorphic nucleotide sites, 36 different alleles, 48 sequence types, 24 of which were novel, were identified among 178 isolates, revealing a geneticallly diverse T. vaginalis population. Polymorphism was found at most loci, clustering genotypes into eight groups among both Australian and Ghanaian isolates, although there was some variation between countries. The number of alleles for each locus ranged from two to nine. Study results confirmed geographic expansion and diversity of the T. vaginalis population. Two-type populations in almost equal frequencies and a third unassigned group were identified in this study. Linkage disequilibrium was observed, suggesting T. vaginalis population is highly clonal. Multillocus disequilibrium was observed even when analysing clades separately, as well as widespread clonal genotypes, suggesting that there is no evidence of recent recombination. A more comprehensive study to assess the extent of genetic diversity and population structure of T. vaginalis and their potential impact on varied pathology observed among infected individuals is recommended.

Kapsulotaenia tidswelli is a proteocephalidean cestode that utilizes varanid lizards as definitive hosts. Fresh specimens of this cestode were observed with endogenous red pigmentation in the neck region that disappeared rapidly if specimens were not preserved in glutaraldehyde. The ultrastructural characteristics of the red pigment, which are described, suggest it is a carotenoid. Phylogenetic analysis confirmed a close relationship between K. tidswelli and other species of Kapsulotaenia for which sequence information is available. There is thus no reason to consider that the red pigmentation is because K. tidswelli is atypical, and it is proposed the carotenoids are likely to be associated with the diet of its varanid host.

Parasites are important drivers of ecosystem functions and play a key role in the maintenance of ecosystem health. However, parasites may be threatened by host conservation, as well as by host extinction. Captive management is of increasing importance for conserving threatened host species, but captivity represents a drastic environmental change that may in turn threaten parasites. To address this concern, we examined how host captivity affects the odds of parasite infection and identified which parasite life-history traits (particularly modes of transmission) are the strongest predictors of parasite decline. Data were collated from 45 studies examining parasite prevalence in both captive and free-range host populations across a total of 55 host and 158 parasite species. We performed meta-analyses of these studies and found that overall, the odds of infection by parasites were not different between host populations in captive and free-range environments. However, the odds of infection by helminths were lower in captivity. Parasites with indirect life cycles, especially helminths with complex life cycles and vector-borne protozoa, also had lower odds of infecting hosts in captivity. Finally, parasites transmitted through the environment with direct life cycles, particularly environmentally-transmitted helminths, had lower odds of infecting hosts in captivity. Parasite losses in captivity are likely caused by the use of antiparasitic drugs, and the biotic and abiotic differences between captive and free-range environments. If the goals of activities such as captive breeding are to re-establish self-sustaining ecosystems, then conservation efforts need to include both hosts and their parasites in captive management programs.

At least 25% of lambs born in Australia die before marking. Research across southern Australia has demonstrated that reducing mob size at lambing by 100 ewes will, on average, increase the survival of single-born lambs by 0.8% and twin-born lambs by 2.2%. In this paper we assessed the economic value of lambing ewes in smaller mobs to improve lamb survival. The analysis considered scenarios for Merino and non-Merino flocks where producers subdivided lambing paddocks using temporary or permanent fencing, or where ewes were reallocated within existing paddocks based on ewe pregnancy status. Optimum mob sizes were most sensitive to the type of fencing used for subdivision, whether ewes were single- or twin-bearing, whether the effect of paddock size on potential stocking rate was included and the target return on investment. Breed, ewe stocking rate, scanning percentage and lamb price also impacted optimum mob size but had a smaller effect. The optimum mob size for twin-bearing Merino and non-Merino ewes was between 34% and 60% that of single-bearing ewes and this was similar for scenarios where paddocks were subdivided or ewes were reallocated within existing paddocks. Permanent subdivision of paddocks also presents an opportunity to increase stocking rate by capitalising on the benefits of improved pasture utilisation in smaller paddocks. The relationship between paddock size and pasture utilisation is not well quantified but it has an important effect on optimum mob and paddock size. The value of reallocating ewes within existing paddocks was greatest at a scanning percentage of 150% as this presents the greatest opportunity to alter mob sizes for single- and twin-bearing ewes. The economic return from adjusting the relative mob size of twin-bearing ewes from 100% to 50% that of single-bearing ewes was up to $0.27/Merino ewe/yr and $0.44/non-Merino ewe/yr with lamb at $6/kg carcass weight. Overall, these analyses demonstrate that reducing mob size at lambing can be a profitable strategy for improving lamb survival depending on the current size of lambing mobs. However, it is difficult to provide generic recommendations to producers for the optimum mob size of ewes and value of paddock subdivision because these are dependent on enterprise-specific factors.

Molecular epidemiology (ME) is the application of molecular tools to determine the causation of disease. With infectious diseases, such as echinococcosis, this applies to identifying and characterising the aetiological agents and elucidating host range. Such an approach has been very successful with the causative agents of echinococcosis, species ofEchinococcus, initially by providing a workable and practical taxonomy and subsequently determining transmission patterns in endemic areas. This review summarises the taxonomy and nomenclature of species ofEchinococcusand provides an update on ME investigations of the ecology ofEchinococcustransmission, particularly in areas where more than one species ofEchinococcusis maintained in cycles of transmission that may interact.