An investigation into Toxoplasma gondii at the human-livestock-wildlife interface, South Africa.

Interface areas shared by humans, domestic and wild animals may serve as high transmission contexts for Toxoplasma gondii. However, knowledge about the epidemiology of T. gondii in such areas is currently limited. The present study assessed the seroprevalence of T. gondii in different hosts from Mpumalanga, South Africa. Furthermore, we investigated the local knowledge and related practices about T. gondii by conducting a questionnaire study in the community. Blood samples were obtained and analysed for T. gondii antibodies using a commercial multispecies latex agglutination kit. The seroprevalence detected in humans (n = 160; patients showing signs of acute febrile illness), cats (n = 9), chickens (n = 336) and goats (n = 358) was 8.8%, 0.0%, 4.2% and 11.2%, respectively. Seroprevalence in impalas (n = 97), kudus (n = 55), wild dogs (n = 54), wildebeests (n = 43), warthogs (n = 97) and zebras (n = 68) was calculated at 5.2%, 7.3%, 100.0%, 20.9%, 13.4% and 9.1%, respectively. The questionnaire revealed that 63.0% of household owners were subsistence farmers, and 35.9% were pet owners. A high level of female participation was found (75.3%) when compared to male participation (24.7%). The results show a low circulation of T. gondii in the domestic cycle and suggest the presence of possible bridges between the wildlife cycle and the surrounding domestic cycle.Contribution: The study contributes to identifying transmission patterns and risk factors of T. gondii within human and animal populations. This topic fits within the scope of the journal presenting original research in veterinary science, with the focus on wild and domestic populations on the African continent on a topic of universal importance.

Ranging behaviours across ecological and anthropogenic disturbance gradients: a pan-African perspective of giraffe (Giraffa spp.) space use.

Animal movement behaviours are shaped by diverse factors, including resource availability and human impacts on the landscape. We generated home range estimates and daily movement rate estimates for 149 giraffe (Giraffa spp.) from all four species across Africa to evaluate the effects of environmental productivity and anthropogenic disturbance on space use. Using the continuous time movement modelling framework and a novel application of mixed effects meta-regression, we summarized overall giraffe space use and tested for the effects of resource availability and human impact on 95% autocorrelated kernel density estimate (AKDE) size and daily movement. The mean 95% AKDE was 359.9 km2 and the mean daily movement was 14.2 km, both with marginally significant differences across species. We found significant negative effects of resource availability, and significant positive effects of resource heterogeneity and protected area overlap on 95% AKDE size. There were significant negative effects of overall anthropogenic disturbance and positive effects of the heterogeneity of anthropogenic disturbance on daily movements and 95% AKDE size. Our results provide unique insights into the interactive effects of resource availability and anthropogenic development on the movements of a large-bodied browser and highlight the potential impacts of rapidly changing landscapes on animal space-use patterns.

African wild dogs (Lycaon pictus) from the Kruger National Park, South Africa are currently not inbred but have low genomic diversity.

African wild dogs (Lycaon pictus) have undergone severe population reductions and are listed as endangered on the International Union for Conservation of Nature Red List. Small, isolated populations have the potential to suffer from threats to their genetic diversity that may impact species viability and future survival. This study provides the first set of population-wide genomic data to address conservation concerns for this endangered species. Whole genome sequencing data were generated for 71 free-ranging African wild dogs from the Kruger National Park (KNP), South Africa, and used to estimate important population genomic parameters. Genomic diversity metrics revealed that variation levels were low; however, this African wild dog population showed low levels of inbreeding. Very few first- and second-order relationships were observed in this cohort, with most relationships falling into the third-order or distant category. Patterns of homozygosity could have resulted from historical inbreeding or a loss in genome variation due to a population bottleneck. Although the results suggest that this stronghold African wild dog population maintains low levels of inbreeding, likely due to their cooperative breeding system, it may lead to a continuous population decline when a reduced number of suitable mates are available. Consequently, the low genomic variation may influence species viability over time. This study highlights the importance of assessing population genomic parameters to set conservation priorities. Future studies should include the investigation of the potential of this endangered species to adapt to environmental changes considering the low genomic diversity in this population.

Viral dynamics and immune responses to foot-and-mouth disease virus in African buffalo (Syncerus caffer).

Foot-and-mouth disease (FMD) is one of the most important livestock diseases restricting international trade. While African buffalo (Syncerus caffer) act as the main wildlife reservoir, viral and immune response dynamics during FMD virus acute infection have not been described before in this species. We used experimental needle inoculation and contact infections with three Southern African Territories serotypes to assess clinical, virological and immunological dynamics for thirty days post infection. Clinical FMD in the needle inoculated buffalo was mild and characterised by pyrexia. Despite the absence of generalised vesicles, all contact animals were readily infected with their respective serotypes within the first two to nine days after being mixed with needle challenged buffalo. Irrespective of the route of infection or serotype, there were positive associations between the viral loads in blood and the induction of host innate pro-inflammatory cytokines and acute phase proteins. Viral loads in blood and tonsil swabs were tightly correlated during the acute phase of the infection, however, viraemia significantly declined after a peak at four days post-infection (dpi), which correlated with the presence of detectable neutralising antibodies. In contrast, infectious virus was isolated in the tonsil swabs until the last sampling point (30 dpi) in most animals. The pattern of virus detection in serum and tonsil swabs was similar for all three serotypes in the direct challenged and contact challenged animals. We have demonstrated for the first time that African buffalo are indeed systemically affected by FMD virus and clinical FMD in buffalo is characterized by a transient pyrexia. Despite the lack of FMD lesions, infection of African buffalo was characterised by high viral loads in blood and oropharynx, rapid and strong host innate and adaptive immune responses and high transmissibility.

Detection of African Swine Fever Virus in Ornithodoros Tick Species Associated with Indigenous and Extralimital Warthog Populations in South Africa.

We investigated the possibility that sylvatic circulation of African swine fever virus (ASFV) in warthogs and Ornithodoros ticks had extended beyond the historically affected northern part of South Africa that was declared a controlled area in 1935 to prevent the spread of infection to the rest of the country. We recently reported finding antibody to the virus in extralimital warthogs in the south of the country, and now describe the detection of infected ticks outside the controlled area. A total of 5078 ticks was collected at 45 locations in 7/9 provinces during 2019-2021 and assayed as 711 pools for virus content by qPCR, while 221 pools were also analysed for tick phylogenetics. Viral nucleic acid was detected in 50 tick pools representing all four members of the Ornithodoros (Ornithodoros) moubata complex known to occur in South Africa: O. (O.) waterbergensis and O. (O.) phacochoerus species yielded ASFV genotypes XX, XXI, XXII at 4 locations and O. (O.) moubata yielded ASFV genotype I at two locations inside the controlled area. Outside the controlled area, O. (O.) moubata and O. (O.) compactus ticks yielded ASFV genotype I at 7 locations, while genotype III ASFV was identified in O. (O.) compactus ticks at a single location. Two of the three species of the O. (O.) savignyi complex ticks known to be present in the country, O. (O.) kalahariensis and O. (O.) noorsveldensis, were collected at single locations and found negative for virus. The only member of the Pavlovskyella subgenus of Ornithodoros ticks known to occur in South Africa, O. (P.) zumpti, was collected from warthog burrows for the first time, in Addo National Park in the Eastern Cape Province where ASFV had never been recorded, and it tested negative for the viral nucleic acid. While it is confirmed that there is sylvatic circulation of ASFV outside the controlled area in South Africa, there is a need for more extensive surveillance and for vector competence studies with various species of Ornithodoros ticks.

Extension of Sylvatic Circulation of African Swine Fever Virus in Extralimital Warthogs in South Africa.

Sylvatic circulation of African swine fever virus (ASFV) in warthogs and Ornithodoros ticks that live in warthog burrows historically occurred in northern South Africa. Outbreaks of the disease in domestic pigs originated in this region. A controlled area was declared in the north in 1935 and regulations were implemented to prevent transfer of potentially infected suids or products to the rest of the country. However, over the past six decades, warthogs have been widely translocated to the south where the extralimital animals have flourished to become an invasive species. Since 2016, there have been outbreaks of ASF in pigs outside the controlled area that cannot be linked to transfer of infected animals or products from the north. An investigation in 2008-2012 revealed that the presence of Ornithodoros ticks and ASFV in warthog burrows extended marginally across the boundary of the controlled area. We found serological evidence of ASFV circulation in extralimital warthogs further south in the central part of the country.

Shedding of Mycobacterium bovis in respiratory secretions of free-ranging wild dogs (Lycaon pictus): Implications for intraspecies transmission.

It has recently been discovered that Mycobacterium bovis (M. bovis) causes disease in the endangered African wild dog (Lycaon pictus) in areas endemic for bovine tuberculosis (bTB), including the Kruger National Park (KNP). However, information on M. bovis infection dynamics within this species is limited and requires investigation as M. bovis can cause conservation consequences due to movement restrictions, crucial for genetic management. This study had two aims: firstly, to investigate mycobacterial shedding in free-ranging wild dogs from KNP by culturing oropharyngeal swab (OS) and bronchoalveolar lavage (BAL) samples. Secondly, to determine the relationship between ante-mortem culture and interferon gamma release assay (IGRA) results as well as agreement between OS culture and BAL culture results. Mycobacterial culture revealed that 6 of 173 (3.5%) OS samples and 1 of 32 (3.1%) BAL samples (from 7 different wild dogs) were M. bovis culture positive, suggesting that wild dogs can shed M. bovis through respiratory secretions. However, the possibility of contamination by ingestion of infected prey cannot be excluded in wild dogs with positive OS culture results. Furthermore, the test outcomes between IGRA and culture (OS and BAL) differed substantially. Samples from 172 wild dogs were available for IGRA screening and 134 had positive results (detectable M. bovis immune sensitization). Seven wild dogs had culture-positive results, which included one additional wild dog that did not have an IGRA result (total 173 wild dogs). Out of these 7 M. bovis culture-positive wild dogs, 3 were IGRA positive initially, however, after repeat sampling and testing, 5 out of 7 were IGRA positive. These findings suggest that intraspecies transmission of M. bovis may be possible among wild dogs. Although the risk of intraspecies transmission is currently unknown, this knowledge is important for assessing the risk of M. bovis transmission from infected wild dogs to uninfected populations during translocations.

Mycobacterium bovis Infection in Free-Ranging African Elephants.

Mycobacterium bovis infection in wildlife species occurs worldwide. However, few cases of M. bovis infection in captive elephants have been reported. We describe 2 incidental cases of bovine tuberculosis in free-ranging African elephants (Loxodonta africana) from a tuberculosis-endemic national park in South Africa and the epidemiologic implications of these infections.

Persistent Infection of African Buffalo (Syncerus caffer) with Foot-and-Mouth Disease Virus: Limited Viral Evolution and No Evidence of Antibody Neutralization Escape.

African buffaloes (Syncerus caffer) are the principal "carrier" hosts of foot-and-mouth disease virus (FMDV). Currently, the epithelia and lymphoid germinal centers of the oropharynx have been identified as sites for FMDV persistence. We carried out studies in FMDV SAT1 persistently infected buffaloes to characterize the diversity of viruses in oropharyngeal epithelia, germinal centers, probang samples (oropharyngeal scrapings), and tonsil swabs to determine if sufficient virus variation is generated during persistence for immune escape. Most sequencing reads of the VP1 coding region of the SAT1 virus inoculum clustered around 2 subpopulations differing by 22 single-nucleotide variants of intermediate frequency. Similarly, most sequences from oropharynx tissue clustered into two subpopulations, albeit with different proportions, depending on the day postinfection (dpi). There was a significant difference between the populations of viruses in the inoculum and in lymphoid tissue taken at 35 dpi. Thereafter, until 400 dpi, no significant variation was detected in the viral populations in samples from individual animals, germinal centers, and epithelial tissues. Deep sequencing of virus from probang or tonsil swab samples harvested prior to postmortem showed less within-sample variability of VP1 than that of tissue sample sequences analyzed at the same time. Importantly, there was no significant difference in the ability of sera collected between 14 and 400 dpi to neutralize the inoculum or viruses isolated at later time points in the study from the same animal. Therefore, based on this study, there is no evidence of escape from antibody neutralization contributing to FMDV persistent infection in African buffalo.IMPORTANCE Foot-and-mouth disease virus (FMDV) is a highly contagious virus of cloven-hoofed animals and is recognized as the most important constraint to international trade in animals and animal products. African buffaloes (Syncerus caffer) are efficient carriers of FMDV, and it has been proposed that new virus variants are produced in buffalo during the prolonged carriage after acute infection, which may spread to cause disease in livestock populations. Here, we show that despite an accumulation of low-frequency sequence variants over time, there is no evidence of significant antigenic variation leading to immune escape. Therefore, carrier buffalo are unlikely to be a major source of new virus variants.

Fatal Tuberculosis in a Free-Ranging African Elephant and One Health Implications of Human Pathogens in Wildlife.

Tuberculosis (TB) in humans is a global public health concern and the discovery of animal cases of Mycobacterium tuberculosis (Mtb) infection and disease, especially in multi-host settings, also has significant implications for public health, veterinary disease control, and conservation endeavors. This paper describes a fatal case of Mtb disease in a free-ranging African elephant (Loxodonta africana) in a high human TB burden region. Necropsy revealed extensive granulomatous pneumonia, from which Mtb was isolated and identified as a member of LAM3/F11 lineage; a common lineage found in humans in South Africa. These findings are contextualized within a framework of emerging Mtb disease in wildlife globally and highlights the importance of the One Health paradigm in addressing this anthroponotic threat to wildlife and the zoonotic implications.

Conservation of White Rhinoceroses Threatened by Bovine Tuberculosis, South Africa, 2016-2017.

During 2016-2017, when Kruger National Park, South Africa, was under quarantine to limit bovine tuberculosis spread, we examined 35 white and 5 black rhinoceroses for infection. We found 6 infected white rhinoceroses during times of nutritional stress. Further research on Mycobacterium bovis pathogenesis in white rhinoceroses is needed.

Differential Persistence of Foot-and-Mouth Disease Virus in African Buffalo Is Related to Virus Virulence.

UNLABELLED: Foot-and-mouth disease (FMD) virus (FMDV) circulates as multiple serotypes and strains in many regions of endemicity. In particular, the three Southern African Territories (SAT) serotypes are maintained effectively in their wildlife reservoir, the African buffalo, and individuals may harbor multiple SAT serotypes for extended periods in the pharyngeal region. However, the exact site and mechanism for persistence remain unclear. FMD in buffaloes offers a unique opportunity to study FMDV persistence, as transmission from carrier ruminants has convincingly been demonstrated for only this species. Following coinfection of naive African buffaloes with isolates of three SAT serotypes from field buffaloes, palatine tonsil swabs were the sample of choice for recovering infectious FMDV up to 400 days postinfection (dpi). Postmortem examination identified infectious virus for up to 185 dpi and viral genomes for up to 400 dpi in lymphoid tissues of the head and neck, focused mainly in germinal centers. Interestingly, viral persistence in vivo was not homogenous, and the SAT-1 isolate persisted longer than the SAT-2 and SAT-3 isolates. Coinfection and passage of these SAT isolates in goat and buffalo cell lines demonstrated a direct correlation between persistence and cell-killing capacity. These data suggest that FMDV persistence occurs in the germinal centers of lymphoid tissue but that the duration of persistence is related to virus replication and cell-killing capacity. IMPORTANCE: Foot-and-mouth disease virus (FMDV) causes a highly contagious acute vesicular disease in domestic livestock and wildlife species. African buffaloes (Syncerus caffer) are the primary carrier hosts of FMDV in African savannah ecosystems, where the disease is endemic. We have shown that the virus persists for up to 400 days in buffaloes and that there is competition between viruses during mixed infections. There was similar competition in cell culture: viruses that killed cells quickly persisted more efficiently in passaged cell cultures. These results may provide a mechanism for the dominance of particular viruses in an ecosystem.