Generalists at the interface: Nematode transmission between wild and domestic ungulates

Helminth Parasite Prevalence in the Endangered Ethiopian Wolf (Canis simensis) in Web Valley, Bale Mountains National Park, Ethiopia

Ethiopian wolves (EWs), Canis simensis, are the rarest canids in the world and Africa's most endangered carnivore, found in only six isolated habitat fragments in the highlands of Ethiopia. Previous reports on the prevalence of parasites in the EW in Bale Mountains National Park (BMNP) are limited, with little information on their helminth fauna. This study seeks to understand the prevalence of helminth parasites in the EW in BMNP, Ethiopia. In this study, fecal samples were collected from 43 EWs in Web Valley (WV), BMNP, from June to October 2020, and the presence of helminth eggs was assessed using fecal sedimentation and centrifugal floatation methods with microscopy. Forty-two out of 43 fecal samples from wolves (98%) contained eggs from two taxonomic groups of helminths. Eggs from Capillaria spp. and Trichuris vulpis were found most frequently, followed by Toxocara canis, Diphyllobothrium spp., Toxascaris leonina, and Capillaria aerophila. One EW (2%) was recorded for harboring the cestode Moniezia expansa. About 9 of the 43 EWs (21%) presented monospecific infection: 9 EWs (21%) harbored 2 parasite species, 9 EWs (21%) hosted 3 parasite species, 11 EWs (26%) had infection involving 4 parasite species, 2 EWs (5%) were infected with 5 parasite species, 1 EW (2%) presented 6 parasite species, 1 EW (2%) harbored 7 parasite species, and 1 EW (2%) was diagnosed without parasite species. Concurrent helminth infection was highly associated with female EW. Megeti 3 was associated with a low level of concurrent helminth infection. The prevalence of helminth parasites found in wolves in the study area suggests that the environment is highly contaminated with intestinal parasites. Regular control of parasite transmission in EW, domestic dogs, and humans in and around BMNP, public education, and further parasite epidemiological studies must be conducted.

A molecular assessment of Ostertagia leptospicularis and Spiculopteragia asymmetrica among wild fallow deer in Northern Ireland and implications for false detection of livestock-associated species

BACKGROUND

Wild deer populations utilizing livestock grazing areas risk cross-species transmission of gastrointestinal nematode parasites (GINs), including GINs with anthelmintic resistance (AR) traits. Wild deer have been shown to carry problematic GIN species such as Haemonchus contortus and Trichostrongylus species in the UK, but the presence of livestock GINs in Northern Ireland deer populations is unknown. Also, is it not known whether AR traits exist among GINs of deer such as Ostertagia leptospicularis and Spiculopteragia asymmetrica in pastureland where anthelmintics are heavily used.

METHODS

Adult-stage GIN samples were retrieved from Northern Irish wild fallow deer abomasa. Individual specimens were subject to a species-specific PCR analysis for common sheep and cattle GIN species with ITS-2 sequence analysis to validate species identities. In addition, the beta-tubulin gene was subject to sequencing to identify benzimidazole (BZ) resistance markers.

RESULTS

ITS-2 sequencing revealed O. leptospicularis and S. asymmetrica, but species-specific PCR yielded false-positive hits for H. contortus, Teladorsagia circimcincta, Trichostrongylus axei, T. colubriformis, T. vitrinus and Ostertagia ostertagi. For beta-tubulin, O. leptospicularis and S. asymmetrica yielded species-specific sequences at the E198 codon, but no resistance markers were identified in either species at positions 167, 198 or 200 of the coding region.

DISCUSSION

From this report, no GIN species of significance in livestock were identified among Northern Ireland fallow deer. However, false-positive PCR hits for sheep and cattle-associated GINs is concerning as the presence of deer species in livestock areas could impact both deer and livestock diagnostics and lead to overestimation of both GIN burden in deer and the role as of deer as drivers of these pathogens. ITS-2 sequences from both O. leptospicularis and S. asymmetrica show minor sequence variations to geographically distinct isolates. AR has been noted among GINs of deer but molecular analyses are lacking for GINs of wildlife. In producing the first beta-tubulin sequences for both O. leptospicularis and S. asymmetrica, we report no BZ resistance in this cohort.

CONCLUSIONS

This work contributes to genetic resources for wildlife species and considers the implications of such species when performing livestock GIN diagnostics.

Gastrointestinal parasites of the wild ungulates (Mammalia: Cetartiodactyla) in the Hemis National Park, Ladakh, India

We evaluated the gastrointestinal parasitic prevalence and intensity of wild ungulates in the Hemis National Park of Ladakh by examining their fresh faecal samples. A total of 327 fresh faecal samples from three wild ungulates, blue sheep Pseudois nayaur (n = 127), Ladakh urial Ovis vignei vignei (n = 110), and Himalayan ibex Ibex siberica (n = 90) were collected between June 2021 and May 2022. The techniques of flotation and sedimentation were used to find parasite eggs and oocysts from the faecal samples. Out of 327 samples examined, 165 samples were infected with gastrointestinal parasites making an overall prevalence of 50.45%. Seven parasitic taxa, including one protozoan (Eimeria spp.), five nematodes (Nematodirus spp., Strongyloides spp., Haemonchus sp., Trichuris sp., and Trichostrongylus spp.), and one cestode (Monezia spp.), were found during the current investigation. Mixed infection was reported in 36 (11%) of the total examined samples. The prevalence of gastrointestinal parasites was found to be highest in blue sheep (55.11%), followed by Ladakh urial (49.09%) and Himalayan ibex (45.55%). The highest prevalence was recorded in the summer (64.42%), and the lowest in the winter (33.82%). A significant difference in parasitic prevalence was observed across seasons in each of the three wild ungulate hosts. However, there was no significant difference in the prevalence of parasites between these hosts.

Cattle aggregations at shared resources create potential parasite exposure hotspots for wildlife

Globally rising livestock populations and declining wildlife numbers are likely to dramatically change disease risk for wildlife and livestock, especially at resources where they congregate. However, limited understanding of interspecific transmission dynamics at these hotspots hinders disease prediction or mitigation. In this study, we combined gastrointestinal nematode density and host foraging activity measurements from our prior work in an East African tropical savannah system with three estimates of parasite sharing capacity to investigate how interspecific exposures alter the relative riskiness of an important resource - water - among cattle and five dominant herbivore species. We found that due to their high parasite output, water dependence and parasite sharing capacity, cattle greatly increased potential parasite exposures at water sources for wild ruminants. When untreated for parasites, cattle accounted for over two-thirds of total potential exposures around water for wild ruminants, driving 2-23-fold increases in relative exposure levels at water sources. Simulated changes in wildlife and cattle ratios showed that water sources become increasingly important hotspots of interspecific transmission for wild ruminants when relative abundance of cattle parasites increases. These results emphasize that livestock have significant potential to alter the level and distribution of parasite exposures across the landscape for wild ruminants.

Endoparasite loads and the efficacy of conventional anthelmintics against gastrointestinal nematodes in captive European bison

Although little information exists on the efficacy of deworming in wild ruminants, gastrointestinal nematodes have been found to demonstrate increasing drug resistance. The spread of drug-resistant strains may be increased by transmission among livestock and susceptible wildlife species, thus posing a potential threat to endangered species, such as the European bison. The aim of the study was twofold: to identify the parasite loads in captive European bison with the use of coprological techniques, and to test the influence of other nearby ungulates on the richness of bison parasitofauna. Additionally, the efficacy of deworming procedures against gastrointestinal nematodes in bison was evaluated. The survey was based on a coprological investigation of 285 fecal samples from 156 European bison in 15 enclosures. The parasitofauna of the captive European bison was consistent with those of free-ranging populations. The highest prevalence was noted for Eimeria spp. oocysts (60.7%), strongyle eggs (50.9%), Fasciola hepatica eggs (13.1%), Dictyocaulus viviparus larvae (12.3%) and Trichuris sp. Eggs (9.47%). Moreover, the close proximity of other ungulate species resulted in a higher diversity of parasite species. In all cases, deworming with albendazole, fenbendazole and ivermectin proved to be ineffective against strongylids and Trichuris sp. The results of fecal egg count reduction test (FECRT) ranged from 37.2 to 99.6% (95% CI <90%) for albendazole; values >95% (95% CI = 41-100) were noted for fenbendazole, and FECRT ranged from 63.2 to 97.5 (95% CI = 0-99) for ivermectin. As the results of anthelmintic treatment are unsatisfactory, it seems justified to continue study in this area. Our study is the first large-scale attempt to evaluate the efficacy of anthelminthics in captive European bison. The potential sharing of parasite species between bison and other ungulates should also be further investigated from the perspective of minimizing the risk of the spread of drug-resistant parasite strains.

Refugia or reservoir? Feral goats and their role in the maintenance and circulation of benzimidazole-resistant gastrointestinal nematodes on shared pastures

Gastrointestinal nematodes threaten the productivity of grazing livestock and anthelmintic resistance has emerged globally. It is broadly understood that wild ruminants living in sympatry with livestock act as a positive source of refugia for anthelmintic-susceptible nematodes. However, they might also act as reservoirs of anthelmintic-resistant nematodes, contributing to the spread of anthelmintic resistance at a regional scale. Here, we sampled managed sheep and cattle together with feral goats within the same property in New South Wales, Australia. Internal transcribed spacer 2 (ITS-2) nemabiome metabarcoding identified 12 gastrointestinal nematodes (Cooperia oncophora, Cooperia punctata, Haemonchus contortus, Haemonchus placei, Nematodirus spathiger, Ostertagia ostertagi, Teladorsagia circumcincta, Oesophagostomum radiatum, Oesophagostomum venulosum, Trichostrongylus axei, Trichostrongylus colubriformis and Trichostrongylus rugatus). Isotype-1 β-tubulin metabarcoding targeting benzimidazole resistance polymorphisms identified 6 of these nematode species (C. oncophora, C. punctata, H. contortus, H. placei, O. ostertagi and T. circumcincta), with the remaining 3 genera unable to be identified to the species level (Nematodirus, Oesophagostomum, Trichostrongylus). Both ITS-2 and β-tubulin metabarcoding showed the presence of a cryptic species of T. circumcincta, known from domestic goats in France. Of the gastrointestinal nematodes detected via β-tubulin metabarcoding, H. contortus, T. circumcincta, Nematodirus and Trichostrongylus exhibited the presence of at least one resistance genotype. We found that generalist gastrointestinal nematodes in untreated feral goats had a similarly high frequency of the benzimidazole-resistant F200Y polymorphism as those nematodes in sheep and cattle. This suggests cross-transmission and maintenance of the resistant genotype within the wild ruminant population, affirming that wild ruminants should be considered potential reservoirs of anthelmintic resistance.

Challenges of copro-parasitological surveys in wild Iberian ibex (Capra pyrenaica) populations addressed through a combination of molecular and statistical tools

Copro-parasitological surveys in wildlife face challenges due to the secretive nature of many species and the unknown performance of the diagnostic tests employed. To overcome these issues, we used a combination of hierarchical models (site-occupancy and N-mixture models) applied to copro-parasitological data obtained from fecal samples assigned to the host species by molecular methods in the Iberian ibex in north-western Iberian Peninsula. The aims were to compare the performance of four diagnostic tests (Mini-FLOTAC, McMaster, Willis flotation, and natural sedimentation) and to use this methodological approach (molecular analysis with hierarchical models) to better estimate positivity proportion and shedding intensity in a wild ibex population. Pooled fecal samples were collected, and those confirmed by molecular analyses to be the host species in question were included in the study. Hierarchical models confirmed different performances of each diagnostic test, with Mini-FLOTAC showing higher sensitivity for eimeriid coccidia, Willis flotation (for proportion positive) and McMaster (for shedding intensity) in gastrointestinal Strongylida, and equal performance of MiniFlotac/Willis flotation (for proportion positive) and MiniFlotac/McMaster (for shedding intensity) in Moniezia spp. This study employed a combination of molecular and statistical methods that improved the estimates of prevalence and shedding intensity and allowed us to compare the performance of four diagnostic tests while assessing the effect of covariates. Such improvements are critical to enhancing inference in non-invasive wildlife copro-parasitological studies.

Influence of habitat alteration on the structure of helminth communities in small mammals: a systematic review and critical appraisal of theory and current evidence

Despite the extensive information on the effects of habitat alteration on the structure of helminth communities in small mammals, the evidence is still inconclusive. A systematic review was carried out using the PRISMA (Preferred Reporting Items for Systematic Review and Meta-Analysis) guideline to compile and synthesize available literature on the influence of habitat alteration on the structure of helminth communities in small mammals. The aim of this review was to describe the variation in infection rates of helminth species associated with habitat alteration and to discuss the theoretical framework that may explain such changes in relation to parasite, host, and environmental features. Twenty-three scientific articles published between 2005 and 2022 were reviewed, 22 of which investigated parasite prevalence, 10 parasite burden, and 14 parasite richness in both altered and natural habitats. Information in assessed articles suggests that the structure of helminth communities in small mammals can be impacted by anthropogenic habitat alteration in various ways. Infection rates of monoxenous and heteroxenous helminths may increase or decrease in small mammals depending on whether their hosts (definitive and intermediate) are available, and environmental and host conditions modify the survival and transmission of parasitic forms. Also, given that habitat alteration may favor inter-species contacts, transmission rates of low host-specific helminths could be increased due to exposure to new reservoir hosts. In a continually changing world, it is essential to assess the spatio-temporal variations of helminth communities in wildlife inhabiting altered and natural habitats to determine potential impacts on wildlife conservation and public health.

Contact between European bison and cattle from the cattle breeders' perspective, in the light of the risk of pathogen transmission

Pathogens transmitted between wildlife and domestic animals can pose a threat to endangered species, undermine conservation efforts in wildlife, and affect productivity and parasite control in domestic animals. There are several examples of pathogen transmission between European bison and other animals. The present study surveyed breeders from the vicinity of four large wisent populations in eastern Poland about observed contacts between wisent and cattle. Such contacts were noted by 37% of breeders, indicating a significant risk of contact between European bison and cattle in the study areas, even in the areas where the European bison live mainly in a forest complex, i.e., in the Borecka Forest. A higher potential risk of contacts between European bison and cattle was noted in the Białowieska Forest and the Bieszczady Mountains than in the Borecka and Knyszyńska Forests. In the Białowieska Forest, the risk of viral pathogen transmission resulting from contacts is higher (more direct contacts), and in the case of the Bieszczady Mountains, the probability of parasitic diseases is higher. The chance of contacts between European bison and cattle depended on the distance of cattle pastures from human settlements. Moreover, such contact was possible throughout the year, not only in spring and fall. It appears possible to minimize the risk of contacts between wisent and cattle by changing management practices for both species, such as keeping grazing areas as close as possible to settlements, and reducing the time cattle graze on pastures. However, the risk of contact is much greater if European bison populations are large and are dispersed beyond forest complexes.

Investigation of Parasitic Nematodes Detected in the Feces of Wild Carnivores in the Eastern Qinghai-Tibet Plateau, China

Wildlife shares grazing areas with herders in the eastern Qinghai-Tibet Plateau, and humans can be infected by zoonotic nematodes through direct contact with animals or contaminated water. In this study, fecal samples (n = 296) from wild carnivores were collected to explore the infection rate and molecular genetic characteristics of nematodes by stratified random sampling in the survey areas. Host species and the nematodes they carried were then identified using 16S rRNA and 18S rRNA gene sequencing, respectively. Statistical analysis, neutrality tests, genetic diversity analysis and Bayesian inferred trees were performed to complete the study. In total, 10 species of nematodes were detected in 240 feces from six species of carnivores identified (including dominant Vulpes ferrilata and Vulpes vulpes), namely Uncinaria stenocephala, Toxascaris sp., Crenosoma vulpis, Parapharyngodon bainae, Oesophagostomum muntiacum, Aspiculuris tetraptera, Mastophorus muris, Nematodirus spathiger, Muellerius capillaris, and Molineus patens. Among these nematodes, U. stenocephala (35.83%, 86/240) and Toxascaris sp. (14.58%, 35/240) were detected at higher rates than the other nematodes (χ2 = 516.909, p < 0.05). Of 17 and 18 haplotypes were found based on the ITS1 gene for U. stenocephala and nad1 gene for Toxascaris sp., respectively. For the first time, using molecular methods, we report the infection of V. ferrilata by U. stenocephala, a potential zoonotic parasite, and suggest Toxascaris sp. may be a newly discovered nematode that lives within the fox intestine.

The Prevalence and Control of Lungworms of Pastoral Ruminants in Iran

Lungworms of the genera Dictyocaulus, Muellerius, Protostrongylus, and Cystocaulus are common helminths of domestic and wild ruminants with substantial veterinary and economic importance. Several studies have assessed the presence and prevalence of lungworm infections in ruminants in Iran. This report compiles the available scientific information about the occurrence of lungworms in domestic and wild ruminants in Iran between 1931 and June 2022 to give an insight into their epidemiology, and where possible to describe drug treatment efficacy. For this purpose, national and international scientific databases were searched. Overall, 54 publications comprising 33 articles in peer-reviewed journals, 8 conference papers, and 13 dissertations were evaluated regarding prevalence data; and an additional 4 peer-reviewed articles were evaluated regarding drug efficacy. Seven species of lungworms, namely Dictyocaulus filaria, Dictyocaulus viviparus, Dictyocaulus eckerti, Protostrongylus rufescens, Protostrongylus raillietti, Muellerius capillaris, and Cystocaulus ocreatus have been recorded from different ruminant hosts in Iran. Thirty-three studies conducted on small ruminant (sheep and goat) lungworms reported prevalences of lungworm infection of 11.6%, 45.81% and 66.29% using abattoir meat inspection, Baermann technique and fecal flotation, respectively. Eight studies conducted on large ruminants (cattle and water buffalo) reported prevalences of infection of 14.83%, 13.98% and 5% using abattoir meat inspection, the Baermann technique and fecal flotation, respectively. The prevalence of infection in wild ruminants was variable across examined species; 38% in urial, 37% in wild goats, 5% in goitered gazelles and 67% in red deer, in addition to a single case report in roe deer. There are few contemporary studies assessing the efficacy of currently available broad-spectrum anthelmintic compounds against lungworms in Iran. The high prevalence of multiple lungworm species in Iran, combined with a lack of information about drug efficacy, supports the need to improve the understanding of these important nematode parasites and inform the development of sustainable control strategies. The aim of this review and meta-analysis is to provide a baseline for future conventional parasitology and next generation molecular epidemiological studies of lungworm infection in pastoral ruminants in Iran.

Generalist nematodes dominate the nemabiome of roe deer in sympatry with sheep at a regional level

The growth of livestock farming and the recent expansion of wild ungulate populations in Europe favor opportunities for direct and/or indirect cross-transmission of pathogens. Comparatively few studies have investigated the epidemiology of gastro-intestinal nematode parasites, an ubiquitous and important community of parasites of ungulates, at the wildlife/livestock interface. In this study, we aimed to assess the influence of livestock proximity on the gastrointestinal nematode community of roe deer in a rural landscape located in southern France. Using ITS-2 rDNA nemabiome metabarcoding on fecal larvae, we analysed the gastrointestinal nematode communities of roe deer and sheep. In addition, we investigated Haemonchus contortus nad4 mtDNA diversity to specifically test parasite circulation among domestic and wild host populations. The dominant gastrointestinal nematode species found in both the roe deer and sheep were generalist species commonly found in small ruminant livestock (e.g. H. contortus), whereas the more specialised wild cervid nematode species (e.g. Ostertagia leptospicularis) were only present at low frequencies. This is in marked contrast with previous studies that found the nemabiomes of wild cervid populations to be dominated by cervid specialist nematode species. In addition, the lack of genetic structure of the nad4 mtDNA of H. contortus populations between host species suggests circulation of gastrointestinal nematodes between roe deer and sheep. The risk of contact with livestock only has a small influence on the nemabiome of roe deer, suggesting the parasite population of roe deer has been displaced by generalist livestock parasites due to many decades of sheep farming, not only for deer grazing close to pastures, but also at a larger regional scale. We also observed some seasonal variation in the nemabiome composition of roe deer. Overall, our results demonstrate significant exchange of gastrointestinal nematodes between domestic and wild ungulates, with generalist species spilling over from domestic ungulates dominating wild cervid parasite communities.

Parasitic strongyle nemabiome communities in wild ruminants in Sweden

Background

Wildlife hosts may serve as reservoirs for strongyles, which can be transmitted to domestic livestock. Therefore, studies evaluating nemabiome compositions in wildlife ruminants are of great use in assessing the possibility of transmission of important nematode pathogens to domestic sheep in Sweden.

Methods

First, fecal samples were collected from roe deer (n = 125), fallow deer (n = 106), red deer (n = 18) and mouflon (n = 13) in south central Sweden during the hunting season in 2019. Second, after fecal examination samples were cultured and the larvae were harvested, followed by DNA extractions. Third, all samples were barcoded and processed for sequence analysis on the PacBio platform. Finally, bioinformatic sequence analysis was conducted with DADA2, while species diversity and richness, as well as interactions between the different hosts, were calculated and analyzed in R.

Results

Nematode ITS2 sequences were found in 225 of 262 (86%) samples. In total, 31 taxa were identified, among which 26 (86%) to the species level. These were found in different combinations, among which 24 (77%) occurred in roe deer, 19 (61%) in fallow deer, 20 (65%) in red deer and 10 (32%) in mouflon. Five of the species found are known to be associated with livestock (Chabertia ovina, Haemonchus contortus, Oesophagostomum venulosum, Teladorsagia circumcincta and Trichostrongylus axei). However, in the present study the relative abundance and prevalence of most of these species were low. The most striking exception was T. axei, which was relatively abundant in all wildlife hosts. Mostly a wide range of wildlife specific nematodes such as Ostertagia leptospicularis and Spiculopteragia spp. were identified including the invasive nematode Spiculopteragia houdemeri, which was found for the first time in red deer, fallow deer, and mouflon in Sweden. The difference in the number of shared species between mouflon and all cervids (n = 6) was less than among all three cervids (n = 8).

Conclusion

In this study, we investigated the community structure of parasitic intestinal nematodes in four wildlife hosts, and we found that the majority of the parasite species identified were wildlife specific. We also found a new, potentially invasive species not reported before. After comparing the nemabiome of the wildlife hosts in this study with a previous study in sheep from the same geographical region, we conclude that the horizontal transmission potential appears to be relatively low. Still, cross-infections of nematodes between game and sheep cannot be completely ignored.

Graphical Abstract

Gastrointestinal symbiont diversity in wild gorilla: a comparison of bacterial and strongylid communities across multiple localities

Western lowland gorillas (Gorilla gorilla gorilla) are Critically Endangered and show continued population decline. Consequently, pressure mounts to better understand their conservation threats and ecology. Gastrointestinal symbionts, such as bacterial and eukaryotic communities, are believed to play vital roles in the physiological landscape of the host. Gorillas host a broad spectrum of eucaryotes, so called parasites, with strongylid nematodes being particularly prevalent. While these communities are partially consistent, they are also shaped by various ecological factors, such as diet or habitat type. To investigate gastrointestinal symbionts of wild western lowland gorillas, we analysed 215 faecal samples from individuals in five distinct localities across the Congo Basin, using high-throughput sequencing techniques. We describe the gut bacterial microbiome and genetic diversity of strongylid communities, including strain-level identification of amplicon sequence variants (ASVs). We identified strongylid ASVs from eight genera and bacterial ASVs from twenty phyla. We compared these communities across localities, with reference to varying environmental factors among populations, finding differences in alpha diversity and community compositions of both gastrointestinal components. Moreover, we also investigated covariation between strongylid nematodes and the bacterial microbiome, finding correlations between strongylid taxa and Prevotellaceae and Rikenellaceae ASVs that were consistent across multiple localities. Our research highlights complexity of the bacterial microbiome and strongylid communities in several gorilla populations and emphasizes potential interactions between these two symbiont communities. This study provides a framework for ongoing research into strongylid nematode diversity, and their interactions with the bacterial microbiome, amongst great apes.

Dilution of Epidemic Potential of Environmentally Transmitted Infectious Diseases for Species with Partially Overlapping Habitats

AbstractSpecies diversity may play an important role in the modulation of pathogen transmission through the dilution effect. Infectious disease models can help elucidate mechanisms that may underlie this effect. While many modeling studies have assumed direct host-to-host transmission, many pathogens are transmitted through the environment. We present a mathematical modeling analysis exploring conditions under which we observe the dilution effect in systems with environmental transmission where host species interact through fully or partially overlapping habitats. We measure the strength of the dilution effect by the relative decrease in the basic reproduction number of two-species assemblages compared with that of a focal host species. We find that a dilution effect is most likely when the pathogen is environmentally persistent (frequency-dependent-like transmission). The magnitude of this effect is strongest when the species with the greater epidemic potential is relatively slow to pick up pathogens in the environment (density-dependent transmission) and the species with the lesser epidemic potential is efficient at picking up pathogens (frequency-dependent transmission). These findings suggest that measurable factors, including pathogen persistence and the host's relative efficiency of pathogen pickup, can guide predictions of when biodiversity might lead to a dilution effect and may thus give concrete direction to future ecological work.

Metabarcoding in two isolated populations of wild roe deer (Capreolus capreolus) reveals variation in gastrointestinal nematode community composition between regions and among age classes

Background

Gastrointestinal nematodes are ubiquitous for both domestic and wild ungulates and have varying consequences for health and fitness. They exist as complex communities of multiple co-infecting species, and we have a limited understanding of how these communities vary in different hosts, regions and circumstances or of how this affects their impacts.

Methods

We have undertaken ITS2 rDNA nemabiome metabarcoding with next-generation sequencing on populations of nematode larvae isolated from 149 fecal samples of roe deer of different sex and age classes in the two isolated populations of Chizé and Trois Fontaines in France not co-grazing with any domestic ungulate species.

Results

We identified 100 amplified sequence variants (ASVs) that were assigned to 14 gastrointestinal nematode taxa overall at either genus (29%) or species (71%) level. These taxa were dominated by parasites classically found in cervids—e.g. Ostertagia leptospicularis, Spiculopteragia spp. Higher parasite species diversity was present in the Trois Fontaines population than in the Chizé population including the presence of species more typically seen in domestic livestock (Haemonchus contortus, Bunostomum sp., Cooperia punctata, Teladorsagia circumcincta). No differences in parasite species diversity or community composition were seen in the samples collected from three zones of differing habitat quality within the Chizé study area. Young roe deer hosted the highest diversity of gastrointestinal nematodes, with more pronounced effects of age apparent in Trois Fontaines. The effect of host age differed between gastrointestinal nematode species, e.g. there was little effect on O. leptospicularis but a large effect on Trichostrongylus spp. No effect of host sex was detected in either site.

Conclusions

The presence of some livestock parasite species in the Trois Fontaines roe deer population was unexpected given the isolation of this population away from grazing domestic livestock since decades. Overall, our results illustrate the influence of host traits and the local environment on roe deer nemabiome and demonstrate the power of the nemabiome metabarcoding approach to elucidate the composition of gastrointestinal nematode communities in wildlife.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-05087-5.

Simultaneous Infection of Elaphostrongylus Nematode Species and Parasite Sharing between Sympatrically Occurring Cervids: Moose, Roe Deer, and Red Deer in Poland

It is important to assess the distribution of parasite species across wildlife populations, to design strategies for game management and effective disease control in nature. In this project we quantified the prevalence of Elaphostrongylus species in eight moose populations. We used molecular methods for identification of parasite species and host individual genotypes from fecal samples. We also demonstrated sharing of parasite species between three cervid hosts sympatrically occurring in the Biebrza River valley, North-Eastern Poland, which is occupied by the largest autochthonous, non-harvested moose population in Central Europe. Nematode species from the genus Elaphostrongylus are ubiquitous in the studied moose populations. The presence of a single parasite species (e.g., E. alces) in moose individuals was more common than simultaneous infection with E. alces and E. cervi. The prevalence of both E. alces and E. cervi was higher in males than females. The distribution of E. alces and E. cervi prevalence in moose, roe deer, and red deer were in accordance with the membership of a host to a subfamily. Simultaneous occurrences of both Elaphostrongylus species were significantly more frequently noted in red deer fecal samples than those collected from moose or roe deer. Thus, we consider red deer to play a dominant role in sharing of those nematodes to other cervids. Our findings promote applications of molecular methods of identifying parasite species and the assessment of the exchange of parasite community between wild ruminant species in management and health monitoring of game animal populations.

Comparative survey of gastrointestinal parasites in sympatric Iberian ibex (Capra pyrenaica) and domestic goats using molecular host specific identification

An isolated population of several hundred Iberian ibex (Capra pyrenaica) inhabits the Gerês-Xurés Transboundary Biosphere Reserve (GXTBR) in north-western Iberian Peninsula, in partial sympatry with tens of thousands domestic goats (Capra hircus). This study aimed to assess the prevalence and shedding intensity of gastrointestinal parasites from sympatric herds of domestic goat and Iberian ibex in autumn 2018. A total of 93 pooled faecal samples were collected from GXTBR (39 from domestic goats and 54 from Iberian ibex) and the host species was identified using molecular techniques, whenever defecation was not visualised in the field. Parasitological analysis was achieved by joint Willis flotation/sedimentation, McMaster and Mini-FLOTAC techniques. Seventy-two samples (25 domestic goats and 47 Iberian ibex) were retained for analysis after discarding the least fresh and those with uncertain specific identification. Generalized linear mixed models compared prevalence and shedding intensity between caprine species. Domestic goats showed a non-significant tendency to be more parasitized than Iberian ibex, as assessed by overall prevalence (100.0%, CI₉₅ 86.7-100.0 vs. 74.5%, CI₉₅ 69.5-84.8), and shedding intensity. This study reveals a similar community of gastrointestinal parasites in an abundant livestock species and an isolated population of wild caprine, living in partial sympatry. It is the first study on the health status of this endangered Iberian ibex population, in close contact with livestock, highlighting the need for further sanitary surveillance.

Sheep nemabiome diversity and its response to anthelmintic treatment in Swedish sheep herds

BACKGROUND

A novel way to study the species composition and diversity of nematode parasites in livestock is to perform deep sequencing on composite samples containing a mixture of different species. Herein we describe for the first time the nematode community structures (nemabiomes) inhabiting Swedish sheep and how these are/were affected by host age and recent anthelmintic treatments.

METHODS

A total of 158 fecal samples were collected (n = 35 in 2007 and n = 123 in 2013-2016) and cultured from groups of sheep on 61 commercial farms in the south-central part of the country where most animals are grazed. Among the samples, 2 × 44 (56%) were paired collections from the same groups pre- and post-treatment with anthelmintics such as macrocyclic lactones, benzimidazoles or levamisole. Samples were analyzed for their nemabiome using the PacBio platform followed by bioinformatic sequence analysis with SCATA. Species richness and diversity were calculated and analyzed in R.

RESULTS

Nematode ITS2 sequences were found in all larval culture samples except two, even though the fecal egg counts were below the McMaster threshold in 20 samples. Sequencing yielded, on average, 1008 sequences per sample. In total, 16 operational taxonomical units (OTU), all with ≥ 98 % identity to sequences in the NCBI database, were recognized. The OTUs found represented nematode species of which ten are commonly associated with sheep. Multiple species were identified in all pre-anthelmintic treatment larval culture samples. No effects on nematode diversity were found in relation to host age. On the other hand, recent anthelmintic treatment lowered species richness, especially after use of ivermectin and albendazole. Interestingly, despite zero egg counts after use of levamisole, these samples still contained nematode DNA and especially H. contortus.

CONCLUSIONS

Our findings provide evidence that nemabiome analysis combined with diversity index analysis provides an objective methodology in the study of the efficacy of anthelmintic treatment as both high and low abundant species were detected.

Gastrointestinal parasites of a reintroduced semi-wild plains bison (Bison bison bison) herd: Examining effects of demographic variation, deworming treatments, and management strategy

Bison (Bison spp) are being reintroduced into semi-wild, spatially constrained herds across North America and Europe. Herd managers are concerned about gastrointestinal (GI) nematode parasites as they care for the health of their bison. We examine how demographics, grazing location, herd management, and anthelmintic treatments affect the fecal egg counts (FECs) of GI nematodes within a reintroduced Plains bison (Bison bison bison) herd in the Great Plains. Our results suggest that younger bison (<2 years of age) experience higher GI parasite eggs/oocysts per gram (epg/opg) and that some taxa are more prevalent throughout different periods of a bison's early years. Demographic findings suggest that calf and yearling (0–2 yrs age) bison have the highest FECs and that these decline until reaching a low in peak adulthood and thereafter (x > 6 yrs of age). FECs of both Trichuris spp. and particularly Nematodirus spp. were much more abundant, relatively, during the first year of a bison's life. This pattern was also true of Moniezia spp. and Eimeria spp., however, strongyle-type spp. FECs appeared to peak in relative abundance during the second year of life. Our data also indicate that FECs are influenced by differences in land-use histories of pastures previously grazed by cattle or by the proportion of frequent flooding in different pastures. Treatment results suggest that fenbendazole may more effective than moxidectin at lowering FECs of bison over the long-term, and lasting effects of at least one administered anthelmintic treatment. Multiplex PCR assays revealed that American bison share GI nematodes with cattle including: Ostertagia spp., Haemonchus placei, Cooperia onchophora, and Oesophagostomum spp, but did not detect the presence Trichostrongylus columbriformis. Our results may have wider conservation implications for reintroduction efforts of American bison, as well as the endangered European bison (Bison bonasus).

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Younger plains bison (<2 years of age) are more likely to have higher fecal egg counts of gastrointestinal nematodes.

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Eimeria spp., Trichuris spp., Moniezia spp., and Nematodirus spp. are more prevalent in plains bison between zero and 1 years of age, while strongyle-type nematodes are more prevalent in bison between 1 and 2 years of age.

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Both land-use histories and landscape features may influence higher fecal egg counts of gastrointestinal nematodes in plains bison.

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Plains bison share many of the same type of gastrointestinal parasites found in cattle.

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Fenbendazole anthelmintic was more effective than moxidectin treatments in reducing fecal egg counts of gastrointestinal parasites in plains bison.

Twenty Years of Passive Disease Surveillance of Roe Deer (Capreolus capreolus) in Slovenia

Simple Summary

Wildlife can serve as a reservoir for highly contagious and deadly diseases, many of which are infectious to domestic animals and/or humans. Wildlife disease surveillance can be considered an essential tool to provide important information on the health status of the population and for the protection of human health. Between 2000 and 2019, examinations of 510 roe deer carcasses were conducted by comprehensive necropsy and other laboratory tests. In conclusion, the results of this research indicate a broad spectrum of roe deer diseases, but no identified disease can be considered a significant health threat to other wildlife species and/or to humans.

Abstract

In this paper, we provide an overview of the causes of death of roe deer (Capreolus capreolus) diagnosed within the national passive health surveillance of roe deer in Slovenia. From 2000 to 2019, postmortem examinations of 510 free-ranging roe deer provided by hunters were conducted at the Veterinary Faculty, Slovenia. A comprehensive necropsy was performed. According to the results of the necropsy, the samples were subjected to microscopic, histopathological, bacteriological, parasitological, or virological examination. The most frequent causes of death in roe deer were infectious diseases (67%), followed by noninfectious diseases (28%). Of all deaths, parasitic infections represented 48%, bacterial infections 14.8%, trauma 12.5%, and metabolic disorders 9.8%. Less frequent causes were diseases like neoplasia and mycotic infections, winter starvation, hernias, and lightning strike. This study covered an estimated 1% of the total disease-related mortality of roe deer in Slovenia. Comparisons of sex/age structure indicated that hunters did not provide random samples (e.g., young males were disproportionately represented). Therefore, such monitoring does not ensure an unbiased assessment of the significance of the individual disease for the mortality of the population; however, it can provide credible evidence of whether or not a particular disease is present in a population. We show that no identified disease in roe deer in Slovenia can be considered a significant health threat to roe deer, other wildlife species, or humans.

Investigation on Parasites and Some Causes of Mortality in Captive Punjab urial (Ovis vignei punjabiensis), Pakistan

BACKGROUND

The present study was conducted in Jul 2019 and Jan 2020 in two wildlife parks of the Nowshera district, Khyber Pakhtunkhwa, Pakistan, where the endangered Punjab urial (Ovis vignei punjabiensis) is successfully bred in captivity. We determined diversity of internal and external parasites that take advantage of the situation of congestion, resulting in massive mortalities of wild animals in captivity.

METHODS

Internal parasites of living urial were determined by direct wet smear and flotation methods, while dead urial was necropsied for any pertaining observation.

RESULTS

All examined fecal samples were found infected with gastrointestinal parasites, which had significant difference in the total abundance in winter and summer. S. papillosus and H.contortus, and a single protozoan, Eimeria spp. were the dominant parasites in fecal samples. Ticks collected from urial enclosures and dead animals were of single species H. anatolicum. Theileria spp. was observed in blood, while hydatid cysts were found in lungs and liver of necropsied urial.

CONCLUSION

The study indicates that internal parasites such as Haemonchus contortus and Strongyloides papillosus, while external parasites as Hyalomma anatolicum ticks played major role in the population decline. Strict veterinary control of infectious diseases, provision of hygienic and supplementary diet, and proper maintenance of urial population are necessary measures for the control of mortalities.

Effects of latitude, host body size, and host trophic guild on patterns of diversity of helminths associated with humans, wild and domestic mammals of Mexico

Parasites are strictly associated with their hosts and present a great diversity of life histories, often resulting in different diversity patterns than those observed in free-living species. However, ecological approaches have detected that, in some cases, mammal-associated helminths respond similarly to non-parasitic species in terms of diversity patterns. Using 2200 recorded interactions, we analysed the diversity patterns of helminths (Acanthocephala, Nematoda and Platyhelminthes) harbored by humans, wild and domestic mammals of Mexico, depending on latitude, host body mass and trophic guild (carnivore, herbivore, insectivore, omnivore), considering helminth richness and average taxonomic distinctness, and host phylogenetic diversity and phylogenetic clustering. Latitude was positively correlated with the average taxonomic distinctness encompassing the three parasite phyla and nematodes. Northern latitudes had less taxonomically related parasite assemblages. Host body mass had a significant negative relationship with the average taxonomic distinctness of acanthocephalans and the richness of helminths associated to wild hosts. The omnivore hosts had greater parasite richness, while insectivores had a less taxonomically related parasite assemblage and herbivores had a more heterogeneous parasite assemblage. Our results highlight the importance of incorporating different dimensions of diversity, such as average taxonomic distinctness and to consider the composition of parasite assemblages to better understand their diversity patterns.

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Four diversity measures were used to describe diversity patterns of helminths.

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Latitude was positively correlated with helminth average taxonomic distinctness.

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Host body mass was negatively related with the helminth richness of wildlife hosts.

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Helminth sets of omnivore hosts were richer in parasite species.

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Helminth sets of insectivore hosts had a wider taxonomic breadth.

Ecology eclipses phylogeny as a major driver of nematode parasite community structure in a graminivorous primate

Understanding the relative strength of ecology and phylogeny in shaping parasite communities can inform parasite control and wildlife conservation initiatives while contributing to the study of host species evolution.We tested the relative strengths of phylogeny and ecology in driving parasite community structure in a host whose ecology diverges significantly from that of its closest phylogenetic relatives.We characterized the gastrointestinal (GI) parasite community of wild geladas (Theropithecus gelada), primates that are closely related to baboons but specialized to graminovory in the Ethiopian Highlands.Geladas exhibited very constrained GI parasite communities: only two genera (Oesophagostomum and Trichostrongylus) were identified across 303 samples. This is far below the diversity reported for baboons (Papio spp.) and at the low end of the range of domestic grazers (e.g., Bos taurus, Ovis aries) inhabiting the same region and ecological niche.Using deep amplicon sequencing, we identified 15 amplicon sequence variants (ASVs) within the two genera, seven of which matched to Oesophagostomum sp., seven to Trichostrongylus sp., and one to T. vitrinus.Population was an important predictor of ASV richness. Geladas in the most ecologically disturbed area of the national park exhibited ~4x higher ASV richness than geladas at a less disturbed location within the park.In this system, ecology was a stronger predictor of parasite community structure than phylogeny, with geladas sharing more elements of their parasite communities with other grazers in the same area than with closely related sister taxa.

Wild ruminants as reservoirs of domestic livestock gastrointestinal nematodes

Gastrointestinal nematode (GIN) infections in cattle cause appetite suppression which leads to poor feed conversion, reduced weight gain and reduced milk production. Overuse and exclusive reliance on anthelmintic drugs has resulted in widespread resistance in many parasitic nematode species infecting livestock making control increasingly difficult. Wild ruminants are competent hosts of a number of nematode species that typically infect and are best adapted for cattle, sheep, and goats. Thus, the potential exists for wild ruminants to act as reservoirs in the translocation of domestic GIN, including those carrying anthelmintic resistance mutations as well as susceptible genotypes. The potential for parasite exchange is heightened by interfaces or ecotones between managed and wild rangelands, and by perturbations linked to climate warming that can increasingly alter the distributions of wild ungulates and their interactions with domestic and free-ranging ruminants. To investigate the extent to which wild ruminants harbour parasites capable of infecting domestic ruminants we first performed an epidemiological study of feces from wildlife hosts that spanned 16 states and included white-tailed deer (85 % of the samples), pronghorn, elk, mule deer, bighorn sheep, moose, cattle, and caribou across the United States. All samples were cultured to third stage larvae and nematode DNA was isolated and PCR amplified. Among the 548 wild ruminant samples received, 33 % (181 samples) were positive for nematode DNA, among which half (84 samples) contained DNA from GIN species commonly found in cattle. DNA from cattle GIN species was detected in 46 % of samples from the Northeast, 42 % from the Southeast, 10 % from the Midwest, 0 % from the Southwest and 11 % from the West. Deep amplicon sequencing of the ITS-2 rDNA indicated that Ostertagia and Trichostrongylus were present in 90 % and 69 % of the nematode DNA positive samples, respectively, whereas Haemonchus, Cooperia and Oesophagostomum were present in 26 %, 2 % and 10 % of the samples, respectively. These data clearly show that wild ruminants commonly harbour multiple parasite species whose primary hosts are domestic cattle, and suggest that further work is warranted to investigate their specific roles in the management of anthelmintic resistance.

The effect of livestock on the physiological condition of roe deer (Capreolus capreolus) is modulated by habitat quality

Free-range livestock grazing is a widespread human activity that not only modifies natural vegetation but also leads to interactions with wild ungulates. Most commonly, the interactions between cattle and wild ungulates have been studied with a focus on competition for high-quality forage. However, other mechanisms, such as the risk of parasite infection, might better describe this interaction. We aim to determine whether livestock affect roe deer (Capreolus capreolus Linnaeus, 1758) by reducing habitat quality and increasing the probability of infection by shared parasites. We measured noninvasive fecal cortisol metabolites as an indicator of habitat quality as well as the lung nematode larvae burden from the Dictyocaulus genus. A higher Dictyocaulus larvae load was found in the presence of livestock in pines, and feces collected in winter had a higher parasite load than feces collected in autumn. Additionally, fecal cortisol metabolite levels in the roe deer were affected by the interaction between habitat quality and livestock presence and were higher in the poorest habitat and when living in sympatry with cattle. Our results suggest that physiological stress responses in roe deer were mediated by the habitat type and the presence of competitors. The long-term implications of altered physiological responses such as those demonstrated here should be considered in management strategies for deer.

Molecular Study of Benzimidazole Resistance in Teladorsagia circumcincta Isolated from Sheep in North of Iran

BACKGROUND

Resistance to benzimidazole (BZ) compounds is common in Teladorsagia circumcincta populations in sheep and goats worldwide. Given the importance of anthelmintic resistance and shortage of information on single nucleotide polymorphisms (SNPs) in this prevalent nematode in Iran, this study was conducted.

METHODS

From June to September 2016, abomasa of 139 sheep of different sexes and ages in Amol City slaughterhouse, northern Iran were examined for isolation of nematodes. Totally 45 male T. circumcincta confirmed by both microscopical and nested-PCR-RFLP methods were included in this study. Susceptibility or resistance of each single T. circumcincta worm to benzimidazoles was assessed using allele-specific PCR.

RESULTS

Frequency of genotypes in the present study were 33.33% heterozygote BZ and 66.67% BZ homozygote sensitive. No homozygote resistant worm was found.

CONCLUSION

Resistance against BZs in T. circumcincta of sheep has occurred at a low prevalence in the north of Iran. However, mutated genes might get dominant under drug selection in future. Hence, periodic investigations for early detection of mutated alleles in nematode populations using accurate and sensitive molecular methods such as PCR-RFLP is recommended.

100 Questions in Livestock Helminthology Research

An elicitation exercise was conducted to collect and identify pressing questions concerning the study of helminths in livestock, to help guide research priorities. Questions were invited from the research community in an inclusive way. Of 385 questions submitted, 100 were chosen by online vote, with priority given to open questions in important areas that are specific enough to permit investigation within a focused project or programme of research. The final list of questions was divided into ten themes. We present the questions and set them briefly in the context of the current state of knowledge. Although subjective, the results provide a snapshot of current concerns and perceived priorities in the field of livestock helminthology, and we hope that they will stimulate ongoing or new research efforts.

Lurking in the dark: Cryptic Strongyloides in a Bornean slow loris

Within host communities, related species are more likely to share common parasitic agents, and as a result, morphological similarities have led researchers to conclude that parasites infecting closely related hosts within a community represent a single species. However, genetic diversity within parasite genera and host range remain poorly investigated in most systems. Strongyloides is a genus of soil-transmitted nematode that has been reported from several primate species in Africa and Asia, and has been estimated to infect hundreds of millions of people worldwide, although no precise estimates are available. Here we describe a case of infection with a cryptic species of Strongyloides in a Bornean (Philippine) slow loris (Nycticebus menagensis) living within a diverse community of several primate species in the Lower Kinabatangan Wildlife Sanctuary, Malaysian Borneo. Fresh fecal samples were collected from five primate species and nematode larvae cultured from these samples were selected for phylogenetic analyses. Sequences obtained for most larvae were identified as S. fuelleborni, grouping into three different clusters and showing no aggregation within specific hosts or geographic location. In contrast, a set of parasite sequences obtained from a slow loris clustered closely with S. stercoralis into a different group, being genetically distinct to sequences reported from other primate hosts, humans included. Our results suggest that although S. fuelleborni infects all haplorrhines sampled in this primate community, a different species might be infecting the slow loris, the only strepsirrhine in Borneo and one of the least studied primates in the region. Although more data are needed to support this conclusion, we propose that Strongyloides species in primates might be more diverse than previously thought, with potential implications for ecological and evolutionary host-parasite associations, as well as epidemiological dynamics.

Transmission of Helminths between Species of Ruminants in Austria Appears More Likely to Occur than Generally Assumed

Helminth infections of the gastrointestinal tract and lungs can lead to devastating economical losses to the pastoral based animal production. Farm animals can suffer from malnutrition, tissue damage, and blood loss resulting in impaired production traits and reproduction parameters. In Austria, pastures grazed by sheep, goats, and cattle overlap with the habitats of several species of wild cervids (roe deer, red deer, sika deer, and fallow deer) and bovids (mouflon, chamois, and ibex), and transmission of parasites between different ruminant species seems likely. A complete and updated overview on the occurrence of helminths of domestic and wild ruminants in Austria is presented. Based on these data, intersections of the host spectrum of the determined parasites were depicted. The “liability index” was applied to identify the ruminant species, which most likely transmit parasites between each other. A degree for host specificity was calculated for each parasite species based on the average taxonomic distance of their host species. Of the 73 identified helminth species 42 were identified as generalists, and 14 transmission experiments supported the assumed broad host specificity for 14 generalists and 1 specialist helminth species. Overall, 61 helminths were found to infect more than one host species, and 4 were found in all 10 ruminant species investigated. From these analyses, it can be concluded that a number of helminth parasites of the gastrointestinal tract and the lungs are potentially transmitted between domestic and wild ruminants in Austria. For some parasites and host species, experimental evidence is in support for possible transmission, while for other such studies are lacking. Host preference of different genotypes of the same parasite species may have a confounding effect on the evaluation of cross-transmission, but so far this has not been evaluated systematically in helminths in Austria. Further studies focusing on experimental cross-transmission and genetic characterization are needed to define the potential consequences for the epidemiology of those parasites, animal welfare, and economic impact.

Prediction and attenuation of seasonal spillover of parasites between wild and domestic ungulates in an arid mixed-use system

Transmission of parasites between host species affects host population dynamics, interspecific competition, and ecosystem structure and function. In areas where wild and domestic herbivores share grazing land, management of parasites in livestock may affect or be affected by sympatric wildlife due to cross-species transmission.We develop a novel method for simulating transmission potential based on both biotic and abiotic factors in a semi-arid system in Botswana. Optimal timing of antiparasitic treatment in livestock is then compared under a variety of alternative host scenarios, including seasonally migrating wild hosts.In this region, rainfall is the primary driver of seasonality of transmission, but wildlife migration leads to spatial differences in the effectiveness of treatment in domestic animals. Additionally, competent migratory wildlife hosts move parasites across the landscape.Simulated transmission potential matches observed patterns of clinical disease in livestock in the study area. Increased wildlife contact is correlated with a decrease in disease, suggesting that non-competent wild hosts may attenuate transmission by removing infective parasite larvae from livestock pasture.Optimising the timing of treatment according to within-year rainfall patterns was considerably more effective than treating at a standard time of year. By targeting treatment in this way, efficient control can be achieved, mitigating parasite spillover from wildlife where it does occur. Synthesis and applications. This model of parasite transmission potential enables evidence-based management of parasite spillover between wild and domestic species in a spatio-temporally dynamic system. It can be applied in other mixed-use systems to mitigate parasite transmission under altered climate scenarios or changes in host ranges.

Uncertain links in host-parasite networks: lessons for parasite transmission in a multi-host system

For many parasites, the full set of hosts that are susceptible to infection is not known, and this could lead to a bias in estimates of transmission. We used counts of individual adult parasites from historical parasitology studies in southern Africa to map a bipartite network of the nematode parasites of herbivore hosts that occur in Botswana. Bipartite networks are used in community ecology to represent interactions across trophic levels. We used a Bayesian hierarchical model to predict the full set of host-parasite interactions from existing data on parasitic gastrointestinal nematodes of wild and domestic ungulates given assumptions about the distribution of parasite counts within hosts, while accounting for the relative uncertainty of less sampled species. We used network metrics to assess the difference between the observed and predicted networks, and to explore the connections between hosts via their shared parasites using a host-host unipartite network projected from the bipartite network. The model predicts a large number of missing links and identifies red hartebeest, giraffe and steenbok as the hosts that have the most uncertainty in parasite diversity. Further, the unipartite network reveals clusters of herbivores that have a high degree of parasite sharing, and these clusters correspond closely with phylogenetic distance rather than with the wild/domestic boundary. These results provide a basis for predicting the risk of cross-species transmission of nematode parasites in areas where livestock and wildlife share grazing land.This article is part of the themed issue 'Opening the black box: re-examining the ecology and evolution of parasite transmission'.

Frequency of gastrointestinal and pulmonary helminth infections in wild deer from western Romania

A survey was carried out to assess the prevalence and the intensity of helminth infections in the roe deer (Capreolus capreolus L.), red deer (Cervus elaphus L.) and fallow deer (Dama dama L.) from 16 hunting areas in western Romania. Overall, 122 deer shot during the hunting season 2013-2015 were examined. Haemonchus contortus, Nematodirus filicollis, Oesophagostomum venulosum and Dictyocalus spp. were found in all the deer species. Trichuris spp. and Dicrocoelium dendriticum were found in the roe deer and red deer and Moniezia expansa in roe deer, only. Overall, the prevalences (<35%) and the mean intensities (<20) were quite low in the abomasums and intestine, but H. contortus in fallow deer (>50%). No >2 or 3 helminth species were found in the abomasum, small and large intestine. Lung helminthes in the roe deer and follow deer accounted for 57.1% and 71.4%, respectively. The only specie with a prevalence >50% was in the red deer. D. dendriticum was found in the liver of roe deer and fallow deer.

Evolution and Biogeography of Haemonchus contortus: Linking Faunal Dynamics in Space and Time

History is the foundation that informs about the nuances of faunal assembly that are essential in understanding the dynamic nature of the host-parasite interface. All of our knowledge begins and ends with evolution, ecology and biogeography, as these interacting facets determine the history of biodiverse systems. These components, relating to Haemonchus, can inform about the complex history of geographical distribution, host association and the intricacies of host-parasite associations that are played out in physiological and behavioural processes that influence the potential for disease and our capacity for effective control in a rapidly changing world. Origins and evolutionary diversification among species of the genus Haemonchus and Haemonchus contortus occurred in a complex crucible defined by shifts in environmental structure emerging from cycles of climate change and ecological perturbation during the late Tertiary and through the Quaternary. A history of sequential host colonization associated with waves of dispersal bringing assemblages of ungulates from Eurasia into Africa and processes emerging from ecosystems in collision and faunal turnover defined the arena for radiation among 12 recognized species of Haemonchus. Among congeners, the host range for H. contortus is exceptionally broad, including species among artiodactyls of 40 genera representing 5 families (and within 12 tribes of Bovidae). Broad host range is dramatically reflected in the degree to which translocation, introduction and invasion with host switching, has characterized an expanding distribution over time in North America, South America, southern Eurasia, Australia and New Zealand, coincidental with agriculture, husbandry and global colonization by human populations driven particularly by European exploration after the 1500s. African origins in xeric to mesic habitats of the African savannah suggest that historical constraints linked to ecological adaptations (tolerances and developmental thresholds defined by temperature and humidity for larval stages) will be substantial determinants in the potential outcomes for widespread geographical and host colonization which are predicted to unfold over the coming century. Insights about deeper evolutionary events, ecology and biogeography are critical as understanding history informs us about the possible range of responses in complex systems under new regimes of environmental forcing, especially, in this case, ecological perturbation linked to climate change. A deeper history of perturbation is relevant in understanding contemporary systems that are now strongly structured by events of invasion and colonization. The relaxation of abiotic and biotic controls on the occurrence of H. contortus, coincidental with inception and dissemination of anthelmintic resistance may be synergistic, serving to exacerbate challenges to control parasites or to limit the socioeconomic impacts of infection that can influence food security and availability. Studies of haemonchine nematodes contribute directly to an expanding model about the nature of diversity and the evolutionary trajectories for faunal assembly among complex host-parasite systems across considerable spatial and temporal scales.

On the benefits of systematic reviews for wildlife parasitology

Systematic reviews and meta-analyses are widely accepted as the best means to synthesise quantitative or qualitative scientific evidence. Many scientific fields have embraced these more rigorous review techniques as a means to bring together large and complex bodies of literature and their data. Unfortunately, due to perceived difficulties and unfamiliarity with processes, other fields are not using these options to review their literature. One way to provide guidance for a specific field is to examine critically recent reviews and meta-analyses and to explain the advantages and disadvantages of the various review techniques. In this paper, we examine review papers in the emerging field of wildlife parasitology and compare five different literature review types-configurative narrative review, aggregative scoping review, aggregative literature review, aggregative meta-analysis, and aggregative systematic review. We found that most literature reviews did not adequately explain the methodology used to find the literature under review. We also found that most literature reviews were not comprehensive nor did they critically appraise the literature under review. Such a lack severely reduces the reliability of the reviews. We encourage all authors to consider using systematic reviews in the future, and for authors and peer-reviewers to be aware of the limitations of non-systematic reviews.