The effects of demographic, social, and environmental characteristics on pathogen prevalence in wild felids across a gradient of urbanization

Urbanisation and Host Relatedness Shape Virome Composition in a Widespread, Generalist Carnivore

Urban wildlife species have the potential to serve as links in disease transmission between wildlife, humans and domestic animals at the wildland-urban interface (WUI), contributing to both sustained cross-species transmission of pathogens and the emergence of diseases in susceptible populations. However, the relative roles of host and environmental factors in shaping the composition of pathogen communities in urban wildlife is understudied. In this study, we integrated DNA and RNA virome data with host genomic and GPS datasets to investigate factors shaping virome composition in bobcats (Lynx rufus ) at the WUI in the Tucson Mountains, Arizona, USA. Using a hybrid-capture approach for 31 scats and 17 buccal swabs, we identified multiple viruses that could affect carnivore health at the WUI, including canine parvovirus, feline astrovirus, Felis catus papillomaviruses 2 and 3 and Lyon-IARC polyomavirus. Models of virome composition and distribution of viral taxa indicated contributions of host genetic relatedness and factors relating to urbanisation (such as percentages of urban land cover, road and building densities and distances to roads). Genetic associations with virome compositions were particularly influenced by females. While females exhibit significant isolation by distance, partial Mantel tests revealed a significant correlation between beta diversity and host genetic distance in females only. To our knowledge, this study represents the first assessment of factors shaping virome composition in a wild felid. Our finding of known feline and canine pathogens in bobcats underscores the potential of the WUI to facilitate cross-species transmission between wild and domestic animals.

Influence of Host and Landscape-Associated Factors in the Infection and Transmission of Pathogens: The Case of Directly Transmitted Virus in Mammals

BACKGROUND

Among pathogens associated with mammals, numerous viruses with a direct transmission route impact human, domestic and wild species health. Host and landscape factors affect viral infection and transmission dynamics of these viruses, along with barriers to host dispersal and gene exchange. However, studies show biases toward certain locations, hosts and detected pathogens, with regional variations in similar host-virus associations.

METHODS

Using a systematic review, in two electronic repositories for articles published until December 2022, we analysed the available information on host- and landscape-associated factors influencing the infection and transmission of directly transmitted viruses in mammals.

RESULTS

In the analysis, about 50% of papers examined either host traits, landscape composition or configuration measures, while approximately 24% combined host and landscape-associated factors. Additionally, approximately 17% of the articles included climatic data and 30% integrated factors related to anthropogenic impact, as these variables have a role in host density, distribution and virus persistence. The most significant and frequent host traits used as predictor variables were sex, age, body weight, host density and species identity. Land cover was the most evaluated landscape attribute, while some explored configuration variables like edge density and fragmentation indexes. Finally, temperature, precipitation and features such as human population density and human footprint index were also typically measured and found impactful.

CONCLUSION

Given the many contributions host- and landscape-related factors have in pathogen dynamics, this systematic study contributes to a better knowledge of host-virus dynamics and the identification of variables and gaps that can be used for disease prevention.

Exposure of Urban European Hedgehogs (Erinaceus europaeus) to Toxoplasma gondii in Highly Populated Areas of Northeast Spain

Toxoplasma gondii is a generalist zoonotic parasite that involves a wide range of warm-blooded animals as intermediate hosts and felines as definitive hosts. Recent studies have proved significant positive associations between human population density and T. gondii seroprevalence in wildlife. However, there is limited data regarding T. gondii wildlife in urban areas, where the highest human density occurs. The present study aimed to analyse the T. gondii exposure in urban hedgehogs from the Metropolitan Area of Barcelona, NE Spain. One hundred eighteen hedgehogs were analysed for the presence of antibodies (modified agglutination test; n = 55) and parasite DNA (qPCR; heart = 34; brain = 60). Antibodies were detected in 69.09% of hedgehogs. T. gondii DNA was not detected in any of the analysed samples. The present study reports a high T. gondii seroprevalence in urban hedgehogs in areas surrounding Barcelona, the most densely human-populated area of NE Spain, reinforcing the association between human population density and environmental T. gondii oocysts. The lack of detection by molecular techniques warrants more studies. In the last few decades, the distribution and abundance of European hedgehogs have declined, including their urban populations. Further research is needed to investigate the impact of T. gondii on hedgehog populations.

DNA virome composition of two sympatric wild felids, bobcat (Lynx rufus) and puma (Puma concolor) in Sonora, Mexico

With viruses often having devastating effects on wildlife population fitness and wild mammals serving as pathogen reservoirs for potentially zoonotic diseases, determining the viral diversity present in wild mammals is both a conservation and One Health priority. Additionally, transmission from more abundant hosts could increase the extinction risk of threatened sympatric species. We leveraged an existing circular DNA enriched metagenomic dataset generated from bobcat (Lynx rufus, n = 9) and puma (Puma concolor, n = 13) scat samples non-invasively collected from Sonora, Mexico, to characterize fecal DNA viromes of each species and determine the extent that viruses are shared between them. Using the metaWRAP pipeline to co-assemble viral genomes for comparative metagenomic analysis, we observed diverse circular DNA viruses in both species, including circoviruses, genomoviruses, and anelloviruses. We found that differences in DNA virome composition were partly attributed to host species, although there was overlap between viruses in bobcats and pumas. Pumas exhibited greater levels of alpha diversity, possibly due to bioaccumulation of pathogens in apex predators. Shared viral taxa may reflect dietary overlap, shared environmental resources, or transmission through host interactions, although we cannot rule out species-specific host-virus coevolution for the taxa detected through co-assembly. However, our detection of integrated feline foamy virus (FFV) suggests Sonoran pumas may interact with domestic cats. Our results contribute to the growing baseline knowledge of wild felid viral diversity. Future research including samples from additional sources (e.g., prey items, tissues) may help to clarify host associations and determine the pathogenicity of detected viruses.

Urban landscape and infection risk in free-roaming cats

Despite public concern on the role of free‐roaming cats as reservoirs of zoonotic agents, little is known about the influence of urban and peri‐urban landscapes on the exposure risk. We evaluated the seroprevalence of three zoonotic agents (Chlamydia felis, Coxiella burnetii and Toxoplasma gondii) in domestic cats (Felis catus). Two hundred and ninety‐one free‐roaming cats were trapped in Murcia municipality (Southeast Spain), and their sera were tested for specific antibodies against T. gondii using a modified agglutination test (MAT), and for C. felis, C. burnetii and feline immunodeficiency virus (FIV) antibodies with ELISA technique. Pathogen seroprevalence at 95% CI was calculated for each sex and age category (up to and over 12 months) and compared with a chi‐squared test. The role of human population density and urban landscape characteristics on the risk of pathogen exposure in the cat population was explored using generalized linear models. Seropositivity against a single pathogen was found in 60% of the cats, while 19% was seropositive for two or three pathogens. Seroprevalence of C. felis was 8% (CI_95%: 5–11), 37% (CI_95%: 31–42) for C. burnetii and 42% (CI_95%: 36–47) for T. gondii. In addition to these three pathogens, FIV seropositivity was low (1%, CI_95%: −0.1 to 2) and adult cats were more likely to be seropositive to C. burnetii than young individuals (OR: 2.3, CI_95%: 1.2–4.2). No sex or age class differences in seroprevalence were observed for the rest of the pathogens. Seropositivity was correlated with water surface areas for C. felis, and not with crop areas. Coxiella burnetii seropositivity was correlated with the percentage of urban areas (continuous with only buildings and discontinuous, that include buildings, parks, and pedestrian and urban green areas), human population size and peri‐urban areas with shrubs, and not correlated with other agricultural landscapes (orchards and crop areas). However, the seroprevalence of T. gondii was only associated with agricultural landscapes such as orchards. The detection of hotspot areas of high pathogen exposure risk is the basis for municipal services to implement surveillance and risk factor control campaigns in specific‐risk areas, including (a) efficient health management of urban cat colonies by geographical location, population census and health status monitoring of the components of each cat colony, (b) improvement of hygiene and sanitary conditions at the feeding points of the cat colony and (c) free‐roaming cat trapping for health monitoring and, in the long term, to know the evolution of the health status of their populations.

Cougar use of residential areas and interactions with people in periods of population stability and growth

The presence of large carnivores close to people poses unique challenges for wildlife managers working to maintain fully functioning ecosystems while simultaneously minimizing potential risks to public safety and private property. In western North America, cougar (Puma concolor) use of residential areas is relatively commonplace and has contributed to undesirable interactions with people. A common assumption is that cougar population growth translates into greater proximity to people and more interactions, but to our knowledge, direct evaluation of this assumption has not occurred. We used GPS telemetry locations and confirmed cougar–human interaction reports to construct single-sex Leslie matrices, utilization distributions, and a two-stage hurdle model within a Bayesian framework to investigate the effects of population trajectory on cougar use of residential areas and interactions with people in the wildland–urban interface of western Washington. We collected data during two time periods with different expected population growth rates, anticipating greater cougar use of residential areas and interaction levels during the period of increased growth. Contrary to our initial expectations, we did not detect meaningful differences in cougar presence in residential areas or number of interactions with humans between study periods. Instead, we documented consistent space use patterns by all demographic classes that seemed to be governed by different life-history strategies. Interactions with humans were largely a function of individual cougar behaviors during both study periods. The consistent presence of abundant, well-connected wildlands coupled with cougar dispersal likely mitigated the potential effects of population trajectory as the increased expected growth rate in Period 2 manifested primarily as subadult emigration via wildlands. We found that a source population does not necessarily translate into greater proximity to people and more interactions. Cougar management in wildland–urban environments would benefit from the application of strategies that address the complex interplay of biological and anthropogenic factors that contribute to cougar presence in residential areas and their likelihood of interacting with people.

Zoonotic and vector-borne pathogens in tigers from a wildlife safari park, Italy

Infectious diseases by pathogens, including those of zoonotic concern, may act as a primary or contributory cause of threat to wildlife conservation and may represent a risk for human health, mainly for people working at, or visiting the zoological parks. Given the paucity of data on pathogens infecting wild tigers, we investigated the occurrence of infectious agents in this animal species, with a special focus on those of zoonotic concern. Blood and serum samples from tigers (n = 20) living in a wildlife safari park of southern Italy were screened by serological and molecular tests. All animals scored positive for antibodies against Toxoplasma gondii (100%), whereas they displayed different prevalence of seropositivity for Rickettsia conorii (30%), Bartonella henselae (15%) and Leptospira interrogans sv Icterohaemorrhagiae and/or Leptospira kirschneri sv Grippotyphosa (15%). No antibodies against Coxiella burnetii were detected. In addition, 8 tigers (40%) tested molecularly positive to "Candidatus Mycoplasma haemominutum", and 3 (15%) to Hepatozoon canis. No DNA of R. conorii, Bartonella spp., Ehrlichia/Anaplasma spp. and piroplasmids was amplified. The occurrence of tiger infections by bacteria and parasites may represent a risk for morbidity and, in some circumstances, mortality in this endangered species and a source of infection for other animals, including humans. These findings indicate that the circulation of zoonotic pathogens such as T. gondii, R. conorii, L. interrogans sv Icterohaemorrhagiae, "Candidatus Mycoplasma haemominutum" and B. henselae in given environments may represent a relevant health issue considering the close association among animals and humans visiting, or working at, the wildlife safari park. Preventative measures are advocated in order to control ectoparasites and other sources of infection (e.g., small rodents), thus for minimizing the risk of infection for animals as well as for humans.

Feline immunodeficiency virus in puma: Estimation of force of infection reveals insights into transmission

Determining parameters that govern pathogen transmission (such as the force of infection, FOI), and pathogen impacts on morbidity and mortality, is exceptionally challenging for wildlife. Vital parameters can vary, for example across host populations, between sexes and within an individual's lifetime.Feline immunodeficiency virus (FIV) is a lentivirus affecting domestic and wild cat species, forming species-specific viral-host associations. FIV infection is common in populations of puma (Puma concolor), yet uncertainty remains over transmission parameters and the significance of FIV infection for puma mortality. In this study, the age-specific FOI of FIV in pumas was estimated from prevalence data, and the evidence for disease-associated mortality was assessed.We fitted candidate models to FIV prevalence data and adopted a maximum likelihood method to estimate parameter values in each model. The models with the best fit were determined to infer the most likely FOI curves. We applied this strategy for female and male pumas from California, Colorado, and Florida.When splitting the data by sex and area, our FOI modeling revealed no evidence of disease-associated mortality in any population. Both sex and location were found to influence the FOI, which was generally higher for male pumas than for females. For female pumas at all sites, and male pumas from California and Colorado, the FOI did not vary with puma age, implying FIV transmission can happen throughout life; this result supports the idea that transmission can occur from mothers to cubs and also throughout adult life. For Florida males, the FOI was a decreasing function of puma age, indicating an increased risk of infection in the early years, and a decreased risk at older ages.This research provides critical insight into pathogen transmission and impact in a secretive and solitary carnivore. Our findings shed light on the debate on whether FIV causes mortality in wild felids like puma, and our approach may be adopted for other diseases and species. The methodology we present can be used for identifying likely transmission routes of a pathogen and also estimating any disease-associated mortality, both of which can be difficult to establish for wildlife diseases in particular.

Decreased Sensitivity of the Serological Detection of Feline Immunodeficiency Virus Infection Potentially Due to Imported Genetic Variants

Feline immunodeficiency virus (FIV) is a lentivirus of domestic cats worldwide. Diagnosis usually relies on antibody screening by point-of-care tests (POCT), e.g., by enzyme-linked immunosorbent assays (ELISA), and confirmation using Western blot (WB). We increasingly observed ELISA-negative, WB-positive samples and aimed to substantiate these observations using 1194 serum/plasma samples collected from 1998 to 2019 primarily from FIV-suspect cats. While 441 samples tested positive and 375 tested negative by ELISA and WB, 81 samples had discordant results: 70 were false ELISA-negative (WB-positive) and 11 were false ELISA-positive (WB-negative); 297 ambiguous results were not analyzed further. The diagnostic sensitivity and specificity of the ELISA (82% and 91%, respectively) were lower than those reported in 1995 (98% and 97%, respectively). The diagnostic efficiency was reduced from 97% to 86%. False ELISA-negative samples originated mainly (54%) from Switzerland (1995: 0%). Sixty-four false ELISA-negative samples were available for POCT (SNAP^TM/WITNESS^R): five were POCT-positive. FIV RT-PCR was positive for two of these samples and was weakly positive for two ELISA- and POCT-negative samples. Low viral loads prohibited sequencing. Our results suggest that FIV diagnosis has become more challenging, probably due to increasing travel by cats and the introduction of new FIV isolates not recognized by screening assays.

Evidence of high exposure to Toxoplasma gondii in free-ranging and captive African carnivores

Toxoplasma gondii is an ubiquitous intracellular protozoan parasite. Mammals and birds are intermediate hosts and felid species are definitive hosts. In most human altered habitats the domestic cat is the predominant definitive host. Current knowledge of T. gondii infection in African ecosystems is limited. This study aimed to assess exposure to T. gondii in wild carnivores in the Serengeti ecosystem in East Africa. Carnivores can be infected by the consumption of tissue cysts when feeding on infected animals and by incidental ingestion of oocysts from environmental contamination. Incidental ingestion should occur regardless of a species’ diet whereas the consumption of cysts should increase the chance of infection in carnivorous species. This predicts higher seropositivity in carnivorous than in insectivorous carnivores and lower seropositivity in juvenile carnivores with a long dependency on milk than in adults. We found high seropositivity in carnivorous species: 100% (15 of 15 samples) in adult African lions, 93% (38 of 41 samples) in adult spotted hyenas and one striped hyena sample was positive, whereas all four samples from the insectivorous bat-eared fox were negative. Juvenile hyenas (11 of 19 sera) had significantly lower seropositivity than adults (38 of 41 sera). Long-term monitoring of spotted hyenas revealed no significant difference in seropositivity between two periods (1988–1992 and 2000 to 2016). Identical results were produced in lion and hyena samples by a commercial multi-species ELISA (at serum dilution 1:10) and an in-house ELISA based on a recombinant T. gondii protein (at serum dilution 1:100), making the latter a useful alternative for small amounts of serum. We suggest that diet, age and lifetime range are factors determining seropositivity in carnivores in the Serengeti ecosystem and suggest that the role of small wild felids in the spread of T. gondii in the African ecosystem warrants investigation.

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Most Serengeti lions and spotted hyenas had anti-T. gondii antibodies.

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Spotted hyenas' seropositivity remains similar in two time periods across 28 years.

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The proportion of seropositive juvenile spotted hyenas was lower than in adults.

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No evidence of infection in 4 wild bat-eared foxes, which are insectivorous canids.

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An in-house ELISA permits the use of small amounts of serum.