Prevalence of bovine tuberculosis in African buffalo at Kruger National Park

Bovine tuberculosis in African buffalo (Syncerus caffer): Progression of pathology during infection

Background

Bovine tuberculosis (BTB) is a zoonotic disease of global importance endemic in African buffalo (Syncerus caffer) in sub-Saharan Africa. Zoonotic tuberculosis is a disease of global importance, accounting for over 12,000 deaths annually. Cattle affected with BTB have been proposed as a model for the study of human tuberculosis, more closely resembling the localization and progression of lesions in controlled studies than murine models. If disease in African buffalo progresses similarly to experimentally infected cattle, they may serve as a model, both for human tuberculosis and cattle BTB, in a natural environment.

Methodology/Principal findings

We utilized a herd of African buffalo that were captured, fitted with radio collars, and tested for BTB twice annually during a 4-year-cohort study. At the end of the project, BTB positive buffalo were culled, and necropsies performed. Here we describe the pathologic progression of BTB over time in African buffalo, utilizing gross and histological methods. We found that BTB in buffalo follows a pattern of infection like that seen in experimental studies of cattle. BTB localizes to the lymph nodes of the respiratory tract first, beginning with the retropharyngeal and tracheobronchial lymph nodes, gradually increasing in lymph nodes affected over time. At 36 months, rate of spread to additional lymph nodes sharply increases. The lung lesions follow a similar pattern, progressing slowly, then accelerating their progression at 36 months post infection. Lastly, a genetic marker that correlated to risk of M. bovis infection in previous studies was marginally associated with BTB progression. Buffalo with at least one risk allele at this locus tended to progress faster, with more lung necrosis.

Conclusions/Significance

The progression of disease in the African buffalo mirrors the progression found in experimental cattle models, offering insight into BTB and the interaction with its host in the context of naturally varying environments, host, and pathogen populations.

Epidemiology of Mycobacterium bovis infection in free-ranging rhinoceros in Kruger National Park, South Africa

African rhinoceros survival is threatened by poaching, habitat loss, and climate effects. The presence of Mycobacterium bovis in wild populations creates an additional potential threat to health and conservation programs. This study reports a large survey of M. bovis infection in free-ranging rhinoceros. Our findings confirm a widespread, high infection burden in the rhinoceros population of Kruger National Park, South Africa and identify risk factors for infection. These findings provide a foundation for understanding the spread of bovine tuberculosis in complex ecosystems. This study reflects the complexity of investigating a multihost pathogen in a previously naïve system. It provides an opportunity to increase awareness of the global impact that tuberculosis can have on animal populations, food security, and conservation.

Mycobacterium bovis infection, which is a prominent cause of bovine tuberculosis, has been confirmed by mycobacterial culture in African rhinoceros species in Kruger National Park (KNP), South Africa. In this population-based study of the epidemiology of M. bovis in 437 African rhinoceros (Diceros bicornis, Ceratotherium simum), we report an estimated prevalence of 15.4% (95% CI: 10.4 to 21.0%), based on results from mycobacterial culture and an antigen-specific interferon gamma release assay from animals sampled between 2016 and 2020. A significant spatial cluster of cases was detected near the southwestern park border, although infection was widely distributed. Multivariable logistic regression models, including demographic and spatiotemporal variables, showed a significant, increasing probability of M. bovis infection in white rhinoceros based on increased numbers of African buffalo (Syncerus caffer) herds in the vicinity of the rhinoceros sampling location. Since African buffaloes are important maintenance hosts for M. bovis in KNP, spillover of infection from these hosts to white rhinoceros sharing the environment is suspected. There was also a significantly higher proportion of M. bovis infection in black rhinoceros in the early years of the study (2016–2018) than in 2019 and 2020, which coincided with periods of intense drought, although other temporal factors could be implicated. Species of rhinoceros, age, and sex were not identified as risk factors for M. bovis infection. These study findings provide a foundation for further epidemiological investigation of M. bovis, a multihost pathogen, in a complex ecosystem that includes susceptible species that are threatened and endangered.

CYTOKINE-RELEASE ASSAY FOR THE DETECTION OF MYCOBACTERIUM BOVIS INFECTION IN CHEETAH (ACINONYX JUBATUS)

The lack of species-specific assays for the diagnosis of infectious diseases, such as bovine tuberculosis, poses a threat to the management of wildlife populations, especially for vulnerable species such as cheetah (Acinonyx jubatus). The aim of this study was to identify and develop a cell-mediated immunological cytokine-release assay that could distinguish between Mycobacterium bovis-infected and uninfected cheetahs using commercially available feline cytokine ELISA and domestic cat (Felis catus) recombinant proteins. Antibodies against domestic cat cytokines, tumour necrosis factor alpha (TNF-α), interleukin-1 beta (IL-1β), and interferon gamma (IFN-γ), were screened for cross-reactivity with plasma cytokines from cheetah whole blood stimulated using QuantiFERON^®-TB Gold Plus (QFT) tubes. Evidence of cytokine production in response to QFT mitogen stimulation was observed in all four ELISA assays. However only the Mabtech Cat IFN-γ ELISA^Basic kit could distinguish between M. bovis-infected (n = 1) and uninfected (n = 1) cheetahs and was therefore selected for further evaluation. A preliminary cheetah specific cutoff value (11 pg/ml) for detecting M. bovis infection using the Mabtech Cat IFN-γ release assay was calculated using a M. bovis uninfected cheetah cohort. Although this study only included one confirmed M. bovis culture-positive and one M. bovis culture-negative cheetah, the Mabtech Cat IFN-γ release assay demonstrated its potential for diagnostic application in this species.

Pathological findings in African buffaloes (Syncerus caffer) in South Africa

The African buffalo (Syncerus caffer) is an iconic species of South African megafauna. As the farmed buffalo population expands, the potential impacts on population health and disease transmission warrant investigation. A retrospective study of skin biopsy and necropsy samples from 429 animals was performed to assess the spectrum of conditions seen in buffaloes in South Africa. Determination of the cause of death (or euthanasia) could not be made in 33.1% (136/411) of the necropsy cases submitted due to autolysis or the absence of significant lesions in the samples submitted. Infectious and parasitic diseases accounted for 53.5% (147/275) of adult fatal cases and non-infectious conditions accounted for 34.9% (96/275). Abortions and neonatal deaths made up 11.6% (32/275) of necropsy cases. Rift Valley fever, bovine viral diarrhoea, malignant catarrhal fever, tuberculosis, bacterial pneumonia, anaesthetic deaths, cachexia and hepatotoxic lesions were the most common causes of death. The range of infectious, parasitic and non-infectious diseases to which African buffaloes were susceptible was largely similar to diseases in domestic cattle which supports concerns regarding disease transmission between the two species. The similarity between diseases experienced in both species will assist wildlife veterinarians in the diagnosis and treatment of diseases in captive African buffaloes. The present study likely does not represent accurate disease prevalence data within the source population of buffaloes, and diseases such as anthrax, brucellosis and foot and mouth disease are under-represented in this study. Hepatic ductal plate abnormalities and haemorrhagic septicaemia have not, to our knowledge, been previously reported in African buffaloes.

Application of the gamma-interferon assay to determine the prevalence of bovine tuberculosis in slaughter livestock at abattoirs in Gauteng, South Africa

BACKGROUND

Bovine tuberculosis (bTB) is a zoonotic disease with great economic impact estimated at billions of dollars annually worldwide. Meat inspection represents a long-standing form of disease surveillance that serves both food safety and animal health. The objective of this study was to determine the prevalence of bTB in livestock at abattoirs using a cell-mediated immune (CMI) assay, the gamma interferon (IFN-γ) assay. This cross-sectional study was conducted at selected abattoirs (low-throughput, high-throughput and rural/informal) in Gauteng province, where animals were also subjected to routine meat inspection.

RESULTS

A total of 410 fresh blood samples were collected from slaughter livestock (369 cattle and 41 sheep) from 15 abattoirs, and analysed using Bovigam^® test kit with bovine, avian and Fortuitum purified protein derivatives (PPD) as blood stimulating antigens. The estimated prevalence of bTB in cattle was 4.4% (95% CI: 2.4%-7.3%). The prevalence of bTB in cattle varied between abattoirs (p = .005), ranging from 0% to 23%; however, there were no significant differences among genders, breeds, municipality, districts, origins of animals (feedlot, auction or farm) or throughput of abattoirs. The prevalence of avian reactors was 6.0% (95% CI: 3.6%-9.2%) in cattle, varying between abattoirs (p = .004) and ranging from 0% to 20.7%. None of the sheep with valid test results was positive for bTB and none was avian reactors (95% CI: 0%-15%).

CONCLUSION

The detection of bTB reactor cattle in our study clearly shows the limitation of disease surveillance using a meat inspection approach, as all the 410 slaughter animals sampled had passed visual abattoir inspection and been classified as bTB-free. Our findings therefore emphasize the risk of zoonotic transmission of bTB to abattoir workers and potential food safety hazard to consumers. Furthermore, our study highlights the potential for the use of the IFN-γ assay to reduce this risk.

Review of Diagnostic Tests for Detection of Mycobacterium bovis Infection in South African Wildlife

Wildlife tuberculosis is a major economic and conservation concern globally. Bovine tuberculosis (bTB), caused by Mycobacterium bovis (M. bovis), is the most common form of wildlife tuberculosis. In South Africa, to date, M. bovis infection has been detected in 24 mammalian wildlife species. The identification of M. bovis infection in wildlife species is essential to limit the spread and to control the disease in these populations, sympatric wildlife species and neighboring livestock. The detection of M. bovis-infected individuals is challenging as only severely diseased animals show clinical disease manifestations and diagnostic tools to identify infection are limited. The emergence of novel reagents and technologies to identify M. bovis infection in wildlife species are instrumental in improving the diagnosis and control of bTB. This review provides an update on the diagnostic tools to detect M. bovis infection in South African wildlife but may be a useful guide for other wildlife species.

CONSERVATION CHALLENGES: THE LIMITATIONS OF ANTEMORTEM TUBERCULOSIS TESTING IN CAPTIVE ASIATIC LIONS (PANTHERA LEO PERSICA)

Genetic diversity of captive wild animals can be enhanced by moving those individuals with valuable genes between collections and through introduction of a new pair from a range country. This requires movement of animals, which is inherent with disease risks, such as the introduction of pathogenic Mycobacterium sp. (MTBC) into a zoological collection. Decisions need to be made based on the outcome of perimovement disease screening using an array of tests, the majority of which are unvalidated in the species. A pair of endangered Asiatic lions (Panthera leo persica) imported from India to the United Kingdom were screened for MTBC using the comparative intradermal tuberculosis (TB) test, the feline interferon-γ blood test, and the experimental bacteriophage assay. Reactions on all three tests prompted screening of the three resident Asiatic lions using the same tests, all of which were negative for MTBC. Based on these test results, the decision had to be made to exclude the genetically valuable pair from the current collection. MTBC could not be identified using further tests, including culture and PCR on a bronchoalveolar lavage, on feces, or on postmortem tissues. This case series highlights the usefulness of a control group when interpreting unvalidated test results for detection of MTBC, the value of training big cats for conscious blood sampling, and the practical implications of placing the comparative intradermal TB test in the eyelids, when dealing with a species that requires a general anesthetic for most hands-on interventions.

Risk alleles for tuberculosis infection associate with reduced immune reactivity in a wild mammalian host

Integrating biological processes across scales remains a central challenge in disease ecology. Genetic variation drives differences in host immune responses, which, along with environmental factors, generates temporal and spatial infection patterns in natural populations that epidemiologists seek to predict and control. However, genetics and immunology are typically studied in model systems, whereas population-level patterns of infection status and susceptibility are uniquely observable in nature. Despite obvious causal connections, organizational scales from genes to host outcomes to population patterns are rarely linked explicitly. Here we identify two loci near genes involved in macrophage (phagocyte) activation and pathogen degradation that additively increase risk of bovine tuberculosis infection by up to ninefold in wild African buffalo. Furthermore, we observe genotype-specific variation in IL-12 production indicative of variation in macrophage activation. Here, we provide measurable differences in infection resistance at multiple scales by characterizing the genetic and inflammatory variation driving patterns of infection in a wild mammal.

Context-dependent costs and benefits of tuberculosis resistance traits in a wild mammalian host

Disease acts as a powerful driver of evolution in natural host populations, yet individuals in a population often vary in their susceptibility to infection. Energetic trade-offs between immune and reproductive investment lead to the evolution of distinct life history strategies, driven by the relative fitness costs and benefits of resisting infection. However, examples quantifying the cost of resistance outside of the laboratory are rare. Here, we observe two distinct forms of resistance to bovine tuberculosis (bTB), an important zoonotic pathogen, in a free-ranging African buffalo (Syncerus caffer) population. We characterize these phenotypes as "infection resistance," in which hosts delay or prevent infection, and "proliferation resistance," in which the host limits the spread of lesions caused by the pathogen after infection has occurred. We found weak evidence that infection resistance to bTB may be heritable in this buffalo population (h 2 = 0.10) and comes at the cost of reduced body condition and marginally reduced survival once infected, but also associates with an overall higher reproductive rate. Infection-resistant animals thus appear to follow a "fast" pace-of-life syndrome, in that they reproduce more quickly but die upon infection. In contrast, proliferation resistance had no apparent costs and was associated with measures of positive host health-such as having a higher body condition and reproductive rate. This study quantifies striking phenotypic variation in pathogen resistance and provides evidence for a link between life history variation and a disease resistance trait in a wild mammalian host population.

Genetic insights into dispersal distance and disperser fitness of African lions (Panthera leo) from the latitudinal extremes of the Kruger National Park, South Africa

Background

Female lions generally do not disperse far beyond their natal range, while males can disperse distances of over 200 km. However, in bush-like ecosystems dispersal distances less than 25 km are reported. Here, we investigate dispersal in lions sampled from the northern and southern extremes of Kruger National Park, a bush-like ecosystem in South Africa where bovine tuberculosis prevalence ranges from low to high across a north-south gradient.

Results

A total of 109 individuals sampled from 1998 to 2004 were typed using 11 microsatellite markers, and mitochondrial RS-3 gene sequences were generated for 28 of these individuals. Considerable north-south genetic differentiation was observed in both datasets. Dispersal was male-biased and generally further than 25 km, with long-distance male gene flow (75–200 km, detected for two individuals) confirming that male lions can travel large distances, even in bush-like ecosystems. In contrast, females generally did not disperse further than 20 km, with two distinctive RS-3 gene clusters for northern and southern females indicating no or rare long-distance female dispersal. However, dispersal rate for the predominantly non-territorial females from southern Kruger (fraction dispersers ≥0.68) was higher than previously reported. Of relevance was the below-average body condition of dispersers and their low presence in prides, suggesting low fitness.

Conclusions

Large genetic differences between the two sampling localities, and low relatedness among males and high dispersal rates among females in the south, suggestive of unstable territory structure and high pride turnover, have potential implications for spread of diseases and the management of the Kruger lion population.

Electronic supplementary material

The online version of this article (10.1186/s12863-018-0607-x) contains supplementary material, which is available to authorized users.

Genetic responsiveness of African buffalo to environmental stressors: A role for epigenetics in balancing autosomal and sex chromosome interactions?

In the African buffalo (Syncerus caffer) population of the Kruger National Park (South Africa) a primary sex-ratio distorter and a primary sex-ratio suppressor have been shown to occur on the Y chromosome. A subsequent autosomal microsatellite study indicated that two types of deleterious alleles with a negative effect on male body condition, but a positive effect on relative fitness when averaged across sexes and generations, occur genome-wide and at high frequencies in the same population. One type negatively affects body condition of both sexes, while the other acts antagonistically: it negatively affects male but positively affects female body condition. Here we show that high frequencies of male-deleterious alleles are attributable to Y-chromosomal distorter-suppressor pair activity and that these alleles are suppressed in individuals born after three dry pre-birth years, likely through epigenetic modification. Epigenetic suppression was indicated by statistical interactions between pre-birth rainfall, a proxy for parental body condition, and the phenotypic effect of homozygosity/heterozygosity status of microsatellites linked to male-deleterious alleles, while a role for the Y-chromosomal distorter-suppressor pair was indicated by between-sex genetic differences among pre-dispersal calves. We argue that suppression of male-deleterious alleles results in negative frequency-dependent selection of the Y distorter and suppressor; a prerequisite for a stable polymorphism of the Y distorter-suppressor pair. The Y distorter seems to be responsible for positive selection of male-deleterious alleles during resource-rich periods and the Y suppressor for positive selection of these alleles during resource-poor periods. Male-deleterious alleles were also associated with susceptibility to bovine tuberculosis, indicating that Kruger buffalo are sensitive to stressors such as diseases and droughts. We anticipate that future genetic studies on African buffalo will provide important new insights into gene fitness and epigenetic modification in the context of sex-ratio distortion and infectious disease dynamics.

Prevalence and Risk Factors for Mycobacterium bovis Infection in African Lions ( Panthera leo ) in the Kruger National Park

Mycobacterium bovis, the causative agent of bovine tuberculosis (BTB), is endemic in the Kruger National Park (KNP), South Africa. African lions ( Panthera leo ) are susceptible to BTB, but the impact of the disease on lion populations is unknown. In this study, we used a novel gene expression assay for chemokine (C-X-C motif) ligand 9 (CXCL9) to measure the prevalence of M. bovis infection in 70 free-ranging lions that were opportunistically sampled in the southern and central regions of the KNP. In the southern region of the KNP, the apparent prevalence of M. bovis infection was 54% (95% confidence interval [CI]=36.9-70.5%), compared with 33% (95% CI=18.0-51.8%) in the central region, an important difference (P=0.08). Prevalence of M. bovis infection in lions showed similar patterns to estimated BTB prevalence in African buffaloes ( Syncerus caffer ) in the same areas. Investigation of other risk factors showed a trend for older lions, males, or lions with concurrent feline immunodeficiency virus infection to have a higher M. bovis prevalence. Our findings demonstrate that the CXCL9 gene expression assay is a useful tool for the determination of M. bovis status in free-ranging lions and identifies important epidemiologic trends for future studies.

State-shifts of lion prey selection in the Kruger National Park

Aims Indicators of pending state-shifts carry value for policy makers. Predator–prey relations reflect key ecological processes that shape ecosystems. Variance in predator–prey relations may serve as a key indicator of future state-shifts. Methods Lion (Panthera leo) diet in the Kruger National Park was evaluated as such an indicator. Over the three-decade time span reviewed, variance in diet in relation to rainfall, prey abundance, management strategies and disease emergence were reviewed. Key results Rainfall patterns, both seasonal and cyclical, were identified as key drivers of predator–prey selection. However, the intensity of management in the form of artificial waterpoints overrode and confounded natural process. The results suggest that savanna systems are stable and punctuated by climatic events in the form of extreme above-average rainfall that temporarily destabilises the system. However, droughts are a cyclical part of the savanna system. Conclusion Lion prey selection did fluctuate with changing environmental conditions. Abrupt state shifts did occur; however, the ecosystem returned to a stable state. Implications State shifts in ecosystems pose key challenges to conservation managers. State shifts appear to be primarily associated with management interventions and environmental factors.

DIAGNOSIS AND IMPLICATIONS OF MYCOBACTERIUM BOVIS INFECTION IN BANDED MONGOOSES (MUNGOS MUNGO) IN THE KRUGER NATIONAL PARK, SOUTH AFRICA

Bovine tuberculosis (bTB) was first diagnosed in the Kruger National Park (KNP) in 1990. Research has since focused on the maintenance host, the African buffalo ( Syncerus caffer ) and clinically affected lion ( Panthera leo ). However, little is known about the role of small predators in tuberculosis epidemiology. During 2011-12, we screened banded mongooses ( Mungos mungo ) in the bTB high-prevalence zone of the KNP for Mycobacterium tuberculosis complex members. Fecal swabs, tracheal swabs, and tracheal lavages of 76 banded mongooses caught in cage traps within a 2-km radius of Skukuza Rest Camp were submitted for Mycobacterium culture, isolation, and species identification. Lesions and lymph node samples collected from 12 animals at postmortem examination were submitted for culture and histopathology. In lung and lymph nodes of two banded mongooses, well demarcated, irregularly margined, gray-yellow nodules of up to 5 mm diameter were identified with either central necrosis or calcification, characterized on histopathology as caseating necrosis with epithelioid macrophages or necrogranuloma with calcified centre. No acid fast bacteria were identified with Ziehl-Neelsen stain. We isolated Mycobacterium bovis from lung, lymph node, and liver samples, as well as from tracheal lavages and tracheal swab from the same two banded mongooses. Blood samples were positive by ElephantTB STAT-PAK® Assay for 12 and Enferplex™ TB Assay for five animals. Only the two banded mongooses positive on pathology and M. bovis culture were positive on both serologic assays. We provide evidence of bTB infection in banded mongooses in the KNP, demonstrate their ability to shed M. bovis , and propose a possible antemortem diagnostic algorithm. Our findings open the discussion around possible sources of infection and their significance at the human/wildlife interface in and around Skukuza.

Modelling the role of multi-transmission routes in the epidemiology of bovine tuberculosis in cattle and buffalo populations

A mathematical model that describes the transmission dynamics of bovine tuberculosis (BTB) in both buffalo and cattle populations is proposed. The model incorporates cross-infection and contaminated environment transmission routes. A full analysis of the model is undertaken. The reproduction number of the entire model is comprised of cross-infection and contaminated parameters. This underscores the importance of including both cross-infection and contaminated environment transmission routes. Crucially our simulations suggest that the disease has a more devastating effect on cattle populations than on buffalo populations when all transmission routes are involved. This has important implications for agriculture and tourism.

Estimating wildlife disease dynamics in complex systems using an Approximate Bayesian Computation framework

Emerging infectious diseases of wildlife are of increasing concern to managers and conservation policy makers, but are often difficult to study and predict due to the complexity of host-disease systems and a paucity of empirical data. We demonstrate the use of an Approximate Bayesian Computation statistical framework to reconstruct the disease dynamics of bovine tuberculosis in Kruger National Park's lion population, despite limited empirical data on the disease's effects in lions. The modeling results suggest that, while a large proportion of the lion population will become infected with bovine tuberculosis, lions are a spillover host and long disease latency is common. In the absence of future aggravating factors, bovine tuberculosis is projected to cause a lion population decline of ~3% over the next 50 years, with the population stabilizing at this new equilibrium. The Approximate Bayesian Computation framework is a new tool for wildlife managers. It allows emerging infectious diseases to be modeled in complex systems by incorporating disparate knowledge about host demographics, behavior, and heterogeneous disease transmission, while allowing inference of unknown system parameters.

Enemies and turncoats: bovine tuberculosis exposes pathogenic potential of Rift Valley fever virus in a common host, African buffalo (Syncerus caffer)

The ubiquity and importance of parasite co-infections in populations of free-living animals is beginning to be recognized, but few studies have demonstrated differential fitness effects of single infection versus co-infection in free-living populations. We investigated interactions between the emerging bacterial disease bovine tuberculosis (BTB) and the previously existing viral disease Rift Valley fever (RVF) in a competent reservoir host, African buffalo, combining data from a natural outbreak of RVF in captive buffalo at a buffalo breeding facility in 2008 with data collected from a neighbouring free-living herd of African buffalo in Kruger National Park. RVF infection was twice as likely in individual BTB+ buffalo as in BTB- buffalo, which, according to a mathematical model, may increase RVF outbreak size at the population level. In addition, co-infection was associated with a far higher rate of fetal abortion than other infection states. Immune interactions between BTB and RVF may underlie both of these interactions, since animals with BTB had decreased innate immunity and increased pro-inflammatory immune responses. This study is one of the first to demonstrate how the consequences of emerging infections extend beyond direct effects on host health, potentially altering the dynamics and fitness effects of infectious diseases that had previously existed in the ecosystem on free-ranging wildlife populations.

Selective breeding: the future of TB management in African buffalo?

The high prevalence of bovine tuberculosis (BTB) in African buffalo (Syncerus caffer) in regions of southern African has a negative economic impact on the trade of animals and animal products, represents an ecological threat to biodiversity, and poses a health risk to local communities through the wildlife-cattle-human interface. Test and cull methods may not be logistically feasible in many free-range wildlife systems, and with the presence of co-existing BTB hosts and the limited effectiveness of the BCG vaccine in buffalo, there is a need for alternative methods of BTB management. Selective breeding for increased resistance to BTB in buffalo may be a viable method of BTB management in the future, particularly if genetic information can be incorporated into these schemes. To explore this possibility, we discuss the different strategies that can be employed in selective breeding programmes, and consider the implementation of genetic improvement schemes. We reflect on the suitability of applying this strategy for enhanced BTB resistance in African buffalo, and address the challenges of this approach that must be taken into account. Conclusions and the implications for management are presented.

Understanding protected area resilience: a multi-scale, social-ecological approach

Protected areas (PAs) remain central to the conservation of biodiversity. Classical PAs were conceived as areas that would be set aside to maintain a natural state with minimal human influence. However, global environmental change and growing cross-scale anthropogenic influences mean that PAs can no longer be thought of as ecological islands that function independently of the broader social-ecological system in which they are located. For PAs to be resilient (and to contribute to broader social-ecological resilience), they must be able to adapt to changing social and ecological conditions over time in a way that supports the long-term persistence of populations, communities, and ecosystems of conservation concern. We extend Ostrom's social-ecological systems framework to consider the long-term persistence of PAs, as a form of land use embedded in social-ecological systems, with important cross-scale feedbacks. Most notably, we highlight the cross-scale influences and feedbacks on PAs that exist from the local to the global scale, contextualizing PAs within multi-scale social-ecological functional landscapes. Such functional landscapes are integral to understand and manage individual PAs for long-term sustainability. We illustrate our conceptual contribution with three case studies that highlight cross-scale feedbacks and social-ecological interactions in the functioning of PAs and in relation to regional resilience. Our analysis suggests that while ecological, economic, and social processes are often directly relevant to PAs at finer scales, at broader scales, the dominant processes that shape and alter PA resilience are primarily social and economic.

Epidemiology. Opposite effects of anthelmintic treatment on microbial infection at individual versus population scales

Parasitic worms modulate host immune responses in ways that affect microbial co-infections. For this reason, anthelmintic therapy may be a potent tool for indirectly controlling microbial pathogens. However, the population-level consequences of this type of intervention on co-infecting microbes are unknown. We evaluated the effects of anthelmintic treatment on bovine tuberculosis (BTB) acquisition, mortality after infection, and pathogen fitness in free-ranging African buffalo. We found that treatment had no effect on the probability of BTB infection, but buffalo survival after infection was ninefold higher among treated individuals. These contrasting effects translated into an approximately eightfold increase in the reproductive number of BTB for anthelmintic-treated compared with untreated buffalo. Our results indicate that anthelmintic treatment can enhance the spread of microbial pathogens in some real-world situations.

Disease Control in Wildlife: Evaluating a Test and Cull Programme for Bovine Tuberculosis in African Buffalo

Providing an evidence base for wildlife population management is difficult, due to limited opportunities for experimentation and study replication at the population level. We utilized an opportunity to assess the outcome of a test and cull programme aimed at limiting the spread of Mycobacterium bovis in African buffalo. Buffalo act as reservoirs of M. bovis, the causative agent of bovine tuberculosis (BTB), which can have major economic, ecological and public health impacts through the risk of infection to other wildlife species, livestock and surrounding communities. BTB prevalence data were collected in conjunction with disease control operations in Hluhluwe-iMfolozi Park, South Africa, from 1999 to 2006. A total of 4733 buffalo (250-950 per year) were tested for BTB using the single comparative intradermal tuberculin (SCIT) test, with BTB-positive animals culled, and negative animals released. BTB prevalence was spatially and temporally variable, ranging from 2.3% to 54.7%. Geographic area was a strong predictor of BTB transmission in HiP, owing to relatively stable herds and home ranges. Herds experiencing more intensive and frequent captures showed reduced per capita disease transmission risk and less increase in herd prevalence over time. Disease hot spots did not expand spatially over time, and BTB prevalence in all but the hot spot areas was maintained between 10% and 15% throughout the study period. Our data suggest that HiP's test and cull programme was effective at reducing BTB transmission in buffalo, with capture effort and interval found to be the crucial components of the programme. The programme was thus successful with respect to the original goals; however, there are additional factors that should be considered in future cost/benefit analyses and decision-making. These findings may be utilized and expanded in future collaborative work between wildlife managers, veterinarians and scientists, to optimize wildlife disease control programmes and mitigate conflict at the interface of conservation, agricultural and urban areas.

Positive selection of deleterious alleles through interaction with a sex-ratio suppressor gene in African Buffalo: a plausible new mechanism for a high frequency anomaly

Although generally rare, deleterious alleles can become common through genetic drift, hitchhiking or reductions in selective constraints. Here we present a possible new mechanism that explains the attainment of high frequencies of deleterious alleles in the African buffalo (Syncerus caffer) population of Kruger National Park, through positive selection of these alleles that is ultimately driven by a sex-ratio suppressor. We have previously shown that one in four Kruger buffalo has a Y-chromosome profile that, despite being associated with low body condition, appears to impart a relative reproductive advantage, and which is stably maintained through a sex-ratio suppressor. Apparently, this sex-ratio suppressor prevents fertility reduction that generally accompanies sex-ratio distortion. We hypothesize that this body-condition-associated reproductive advantage increases the fitness of alleles that negatively affect male body condition, causing genome-wide positive selection of these alleles. To investigate this we genotyped 459 buffalo using 17 autosomal microsatellites. By correlating heterozygosity with body condition (heterozygosity-fitness correlations), we found that most microsatellites were associated with one of two gene types: one with elevated frequencies of deleterious alleles that have a negative effect on body condition, irrespective of sex; the other with elevated frequencies of sexually antagonistic alleles that are negative for male body condition but positive for female body condition. Positive selection and a direct association with a Y-chromosomal sex-ratio suppressor are indicated, respectively, by allele clines and by relatively high numbers of homozygous deleterious alleles among sex-ratio suppressor carriers. This study, which employs novel statistical techniques to analyse heterozygosity-fitness correlations, is the first to demonstrate the abundance of sexually-antagonistic genes in a natural mammal population. It also has important implications for our understanding not only of the evolutionary and ecological dynamics of sex-ratio distorters and suppressors, but also of the functioning of deleterious and sexually-antagonistic alleles, and their impact on population viability.

Towards establishing a rhinoceros-specific interferon-gamma (IFN-γ) assay for diagnosis of tuberculosis

Mycobacterium bovis is the causal agent of bovine tuberculosis (BTB), with a diverse host range, extending from livestock to domestic and captive wild animals as well as free-ranging wildlife species. In South Africa, BTB is endemic in the Kruger National Park (KNP) and the Hluluwe iMfolozi National Park (HiP), where the high prevalence of M. bovis infections in buffalo herds has led to infection of a number of wildlife species. This has raised concerns about the spillover into the rhinoceros population, a species known to be susceptible to both M. bovis and Mycobacterium tuberculosis, jeopardizing breeding and relocation projects that serve to conserve and protect this species. In view of the advantages of the interferon-gamma (IFN-γ) assay in the diagnosis of BTB in a variety of species worldwide, such an assay has been developed for rhinoceroses by Morar and co-workers in 2007. In this study, this assay was optimized using recombinant eukaryotic rhinoceros IFN-γ and the lower detection limit was calculated to be 0.5 ng/ml. Subsequently, assessing the detection of native rhinoceros IFN-γ protein in whole-blood samples revealed stimulation with each of the mitogens: pokeweed (PWM), phytohaemagglutinin (PHA) & phorbol 12-myristate 13-acetate and calcium ionophore (PMA/CaI), though most prominently with the latter two. In addition, samples collected from 52 clinically healthy rhinoceroses, of presumed negative BTB status, from two different areas in South Africa were used to determine the cut-off value for a negative test result. This was calculated to be 0.10 (OD490 nm ) and as determined in this study is a preliminary recommendation based on IFN-γ responses observed in samples from BTB-free rhinoceroses only.

Preliminary assessment of bovine tuberculosis at the livestock/wildlife interface in two protected areas of northern Botswana

Protected areas of northern Botswana such as the Okavango Delta (OD) or Chobe National Park (CNP) are well-known hot spots for the conservation of African wildlife. However, their infection status regarding bovine tuberculosis (BTB) at the domestic/wildlife interface has never been investigated. To provide preliminary baseline data on the circulation of Mycobacterium bovis in those sites, we performed a cross-sectional survey on 130 buffalo in both protected areas (60 individuals from CNP and 70 from OD) and 818 cattle in their surrounding communal lands (369 in CNP and 449 in the OD). Whole-blood samples were tested using a commercial interferon-gamma assay (IFN-γ) with modifications. The apparent BTB prevalence in buffalo was nil in CNP and 0.7% 95% CI [0.2-1.9] in the OD, while the apparent BTB prevalence in cattle was 0.7% 95% CI [0.2-2.1] in the OD and 2.4% 95% CI [1.2-4.7] in CNP. True prevalence values calculated on the basis of the locally applicable IFN-γ test performance suggested that BTB prevalence was nil in both buffalo populations and in cattle from the OD interface, but reached 2.3% 95% CI [0.2-4.5] in cattle populations around CNP. The results of a questionnaire survey conducted among a sample of farmers living in the communities adjacent to each conservation area (97 and 38 persons in the OD and CNP, respectively) suggested a higher risk of the circulation of M. bovis at the wildlife/livestock interface of the CNP than at that of the OD. However, further comprehensive studies are needed to confirm the circulation of M. bovis and to monitor the inter-species and transboundary transmission of BTB in northern Botswana.

Prevalence and distribution of non-tuberculous mycobacteria (NTM) in cattle, African buffaloes (Syncerus caffer) and their environments in South Africa

It has been hypothesized that a variety of non-tuberculous mycobacteria (NTM) species to which livestock and wildlife species are naturally exposed induce broadly cross-reactive anti-mycobacterial immune responses which interfere with current standard diagnostic assays. Non-tuberculous mycobacteria have also been implicated in Mycobacterium bovis-specific immune responsiveness, hence potentially the development of tuberculosis. Cattle and African buffaloes are both maintenance hosts of bovine tuberculosis (BTB) in South Africa, yet the effective diagnosis and control in these species may be hampered by adverse effects of NTM. As part of an investigation of the role of NTM in the immune responsiveness of cattle and African buffaloes to NTM, we conducted a countrywide survey to establish the prevalent NTM species and their distribution in the natural environments of these animals. A total of 1123 samples (water, soil, nasal and pharyngeal swabs) were collected for mycobacterium isolation. In addition, NTM isolated from tissue samples between 1991 and 2011 were included in the analysis. Mycobacteria were isolated from 56% of the samples from the countrywide survey. A total of 420 NTM isolates from soil, water, animal tissues and animal-derived swab samples were genotyped with the following results: 302 belonged to 40 known NTM species, 79 were found to be closely related to 23 known NTM species, and 38 isolates were found to be potentially novel species that are not currently listed in the RIDOM and NCBI BLAST databases. The four NTM species or closely related groups most frequently isolated in this survey included Mycobacterium terrae (11.2% of isolates), a group of mycobacteria closely related to Mycobacterium moriokaense (referred to as M. moriokaense-like) (8.1% of isolates), Mycobacterium nonchromogenicum (7.4% of isolates) and Mycobacterium vaccae/M. vanbaalenii (5.2% of isolates). The phylogenetic analysis of the M. moriokaense-like isolates, based on the 16S rRNA sequences, revealed at least eight clusters, possibly associated with eight different NTM species. Our findings provide account of NTM species diversity and associated prevalences in cattle and African buffaloes and their environments in South Africa. The identification of the most prevalent NTM species in this study will allow for a targeted investigation of their effects on host immune responses.

Surveys of lions Panthera leo in protected areas in Zimbabwe yield disturbing results: what is driving the population collapse?

The African lion Panthera leo is an iconic species but it has faced dramatic range reductions and possibly as few as 30,000 individuals remain in the wild. In the absence of detailed ground-based surveys, lion populations may be estimated using regression models based on prey biomass availability but these often overestimate lion densities as a result of a variety of compounding factors. Anthropogenic factors can be key drivers of lion population dynamics and in areas with high human impact lion numbers may be significantly lower than those predicted by prey biomass models. This was investigated in two protected areas in Zimbabwe, where lion population densities were found to be significantly lower than would have been predicted by prey-availability models. High hunting quotas either within or around the protected areas are the most likely cause of the low lion numbers, with quotas in some areas being as high as seven lions per 1,000 km2 in some years. Other factors, including persecution, poisoning and problem animal control, as well as disease and competition with spotted hyaenas Crocuta crocuta, are also discussed.

Bovine Tuberculosis and Brucellosis in Cattle and African Buffalo in the Limpopo National Park, Mozambique

Bovine tuberculosis (BTB) and brucellosis are prevalent in buffaloes of the Kruger National Park (KNP, South Africa). Both diseases were considered to have no or a very low prevalence in wildlife and livestock in and around the Limpopo National Park (LNP, Mozambique). The same applies for tuberculosis in Gonarezhou National Park (GNP, Zimbabwe), but just recently, BTB was detected in buffaloes in the GNP and fears arose that the disease might also spread to the LNP as a result of the partial removal of the fences between the three parks to form the Great Limpopo Transfrontier Park. To assess the status of both diseases in and around LNP, 62 buffaloes were tested for bovine tuberculosis (BTB) and bovine brucellosis. The percentage of positive BTB reactors in buffalo was 8.06% using BovidTB Stat-Pak® and 0% with BOVIGAM® IFN-γ test and IDEXX ELISA. The brucellosis seroprevalence in buffalo was found to be 17.72% and 27.42% using Rose Bengal Test (RBT) and ELISA, respectively. In addition, 2445 cattle in and around the LNP were examined for BTB using the single intradermal cervical comparative tuberculin test (SICCT), and an apparent prevalence of 0.98% was found with no significant difference inside (0.5%) and outside (1.3%) the park. This is the first published report on the presence of positive reactors to BTB and bovine brucellosis in buffalo and cattle in and outside the LNP. Monitoring the wildlife-livestock-human interface of zoonotic high-impact diseases such as BTB and brucellosis is of outmost importance for the successful implementation and management of any transfrontier park that aims to improve the livelihoods of the local communities.

Tuberculosis infection in wildlife from the Ruaha ecosystem Tanzania: implications for wildlife, domestic animals, and human health

Mycobacterium bovis, a pathogen of conservation, livestock, and public health concern, was detected in eight species of wildlife inhabiting protected areas bordering endemic livestock grazing lands. We tested tissues from 179 opportunistically sampled hunter-killed, depredation, road-killed, and live-captured wild animals, representing 30 species, in and adjacent to Ruaha National Park in south-central Tanzania. Tissue culture and PCR were used to detect 12 (8.1%) M. bovis-infected animals and 15 (10.1%) animals infected with non-tuberculosis complex mycobacteria. Kirk's dik-dik, vervet monkey, and yellow baboon were confirmed infected for the first time. The M. bovis spoligotype isolated from infected wildlife was identical to local livestock, providing evidence for livestock-wildlife pathogen transmission. Thus we advocate an ecosystem-based approach for bovine tuberculosis management that improves critical ecological functions in protected areas and grazing lands, reduces focal population density build-up along the edges of protected areas, and minimizes ecological stressors that increase animals' susceptibility to bovine tuberculosis.

Relationship between burden of infection in ungulate populations and wildlife/livestock interfaces

In southern African transfrontier conservation areas (TFCAs), people, livestock and wildlife share space and resources in semi-arid landscapes. One consequence of the coexistence of wild and domestic herbivores is the risk of pathogen transmission. This risk threatens local livelihoods relying on animal production, public health in the case of zoonoses, national economies in the context of transboundary animal diseases, and the success of integrated conservation and development initiatives. The level of interaction between sympatric wild and domestic hosts, defining different wildlife/livestock interfaces, characterizes opportunities of pathogen transmission between host populations. Exploring the relationship between infection burden and different types of wildlife/domestic interfaces is therefore necessary to manage the sanitary risk in animal populations through control options adapted to these multi-host systems. Here, we assessed the infection burdens of sympatric domestic cattle (Bos taurus/Bos indicus) and African buffalo (Syncerus caffer) at an unfenced interface and compared the infection burdens of cattle populations at different wildlife/livestock interfaces in the Great Limpopo TFCA. Patterns of infection in ungulate populations varied between wild and domestic hosts and between cattle populations at different wildlife/livestock interfaces. Foot-and-mouth disease, Rift Valley fever and theileriosis infections were detected in buffalo and cattle at unfenced interfaces; bovine tuberculosis was only present in buffalo; and brucellosis and lumpy skin disease only in cattle. At unfenced interfaces, cattle populations presented significantly higher Theileria parva and brucellosis prevalence. We hypothesize that cattle populations at wildlife/livestock interfaces face an increased risk of infection compared to those isolated from wildlife, and that the type of interface could influence the diversity and quantity of pathogens shared. Additional host behavioural and molecular epidemiological studies need to be conducted to support this hypothesis. If it is confirmed, the management of wildlife/livestock interfaces will need to be considered through the prism of livestock and public health.

Surveillance of bovine tuberculosis and risk estimation of a future reservoir formation in wildlife in Switzerland and Liechtenstein

Bovine tuberculosis (bTB) caused by Mycobacterium bovis or M. caprae has recently (re-) emerged in livestock and wildlife in all countries bordering Switzerland (CH) and the Principality of Liechtenstein (FL). Comprehensive data for Swiss and Liechtenstein wildlife are not available so far, although two native species, wild boar (Sus scrofa) and red deer (Cervus elaphus elaphus), act as bTB reservoirs elsewhere in continental Europe. Our aims were (1) to assess the occurrence of bTB in these wild ungulates in CH/FL and to reinforce scanning surveillance in all wild mammals; (2) to evaluate the risk of a future bTB reservoir formation in wild boar and red deer in CH/FL. Tissue samples collected from 2009 to 2011 from 434 hunted red deer and wild boar and from eight diseased ungulates with tuberculosis-like lesions were tested by direct real-time PCR and culture to detect mycobacteria of the Mycobacterium tuberculosis complex (MTBC). Identification of suspicious colonies was attempted by real-time PCR, genotyping and spoligotyping. Information on risk factors for bTB maintenance within wildlife populations was retrieved from the literature and the situation regarding identified factors was assessed for our study areas. Mycobacteria of the MTBC were detected in six out of 165 wild boar (3.6%; 95% CI: 1.4-7.8) but none of the 269 red deer (0%; 0-1.4). M. microti was identified in two MTBC-positive wild boar, while species identification remained unsuccessful in four cases. Main risk factors for bTB maintenance worldwide, including different causes of aggregation often resulting from intensive wildlife management, are largely absent in CH and FL. In conclusion, M. bovis and M. caprae were not detected but we report for the first time MTBC mycobacteria in Swiss wild boar. Present conditions seem unfavorable for a reservoir emergence, nevertheless increasing population numbers of wild ungulates and offal consumption may represent a risk.

Wildlife reservoirs of bovine tuberculosis worldwide: hosts, pathology, surveillance, and control

Bovine tuberculosis due to Mycobacterium bovis is a zoonotic disease classically carried by cattle and spilling over into humans primarily by the ingestion of milk. However, in recent decades, there have been many endemic geographic localities where M. bovis has been detected infecting wildlife reservoirs, limiting the progress toward eradication of this disease from cattle. These include cervids in North America, badgers in Great Britain, feral pigs in Europe, brushtailed possums in New Zealand, and buffalo in South Africa. An overview of these wildlife hosts will provide insight into how these reservoirs maintain and spread the disease. In addition, the authors summarize the pathology, current ongoing methods for surveillance, and control. In many instances, it has proven to be more difficult to control or eradicate bovine tuberculosis in wild free-ranging species than in domesticated cattle. Furthermore, human influences have often contributed to the introduction and/or maintenance of the disease in wildlife species. Finally, some emerging themes regarding bovine tuberculosis establishment in wildlife hosts, as well as conclusions regarding management practices to assist in bovine tuberculosis control and eradication in wildlife, are offered.

Assessing the impact of feline immunodeficiency virus and bovine tuberculosis co-infection in African lions

Bovine tuberculosis (BTB), caused by Mycobacterium bovis, is a disease that was introduced relatively recently into the Kruger National Park (KNP) lion population. Feline immunodeficiency virus (FIV(ple)) is thought to have been endemic in lions for a much longer time. In humans, co-infection between Mycobacterium tuberculosis and human immunodeficiency virus increases disease burden. If BTB were to reach high levels of prevalence in lions, and if similar worsening effects would exist between FIV(ple) and BTB as for their human equivalents, this could pose a lion conservation problem. We collected data on lions in KNP from 1993 to 2008 for spatio-temporal analysis of both FIV(ple) and BTB, and to assess whether a similar relationship between the two diseases exists in lions. We found that BTB prevalence in the south was higher than in the north (72 versus 19% over the total study period) and increased over time in the northern part of the KNP (0-41%). No significant spatio-temporal differences were seen for FIV(ple) in the study period, in agreement with the presumed endemic state of the infection. Both infections affected haematology and blood chemistry values, FIV(ple) in a more pronounced way than BTB. The effect of co-infection on these values, however, was always less than additive. Though a large proportion (31%) of the lions was co-infected with FIV(ple) and M. bovis, there was no evidence for a synergistic relation as in their human counterparts. Whether this results from different immunopathogeneses remains to be determined.

Modification of the QuantiFERON-TB Gold (In-Tube) assay for the diagnosis of Mycobacterium bovis infection in African buffaloes (Syncerus caffer)

African buffaloes (Syncerus caffer) are the most significant wildlife maintenance hosts of Mycobacterium bovis, the causative organism of bovine tuberculosis (BTB). Current diagnostic tests for the detection of M. bovis infection in free-ranging buffaloes have numerous limitations and we wished to evaluate a modification to a human TB assay, the QuantiFERON-TB Gold (In-Tube) assay (QFT), as a practical diagnostic test for BTB in buffaloes. One hundred and seventy-five buffaloes were tested using the single intradermal comparative tuberculin test (SICTT) and a modified QFT (mQFT). An appropriate cut-off point for the mQFT was derived from SICTT results using receiver operator characteristic curve analysis. Twenty-six SICTT-positive buffaloes were killed and subjected to necropsy, and selected tissues were processed for mycobacterial culture and speciation. An optimal cut-off point for the mQFT was calculated as 66pg/ml. The assay correctly detected 39/40 SICTT-positive buffaloes and 129/134 TST-negative buffaloes and M. bovis was cultured from 21/26 slaughtered SICTT/mQFT-positive animals. The mQFT shows promise as a practical test for M. bovis infection in buffaloes and shows a sensitivity and specificity at least similar to that of the TST.

Rainfall-driven sex-ratio genes in African buffalo suggested by correlations between Y-chromosomal haplotype frequencies and foetal sex ratio

Background

The Y-chromosomal diversity in the African buffalo (Syncerus caffer) population of Kruger National Park (KNP) is characterized by rainfall-driven haplotype frequency shifts between year cohorts. Stable Y-chromosomal polymorphism is difficult to reconcile with haplotype frequency variations without assuming frequency-dependent selection or specific interactions in the population dynamics of X- and Y-chromosomal genes, since otherwise the fittest haplotype would inevitably sweep to fixation. Stable Y-chromosomal polymorphism due one of these factors only seems possible when there are Y-chromosomal distorters of an equal sex ratio, which act by negatively affecting X-gametes, or Y-chromosomal suppressors of a female-biased sex ratio. These sex-ratio (SR) genes modify (suppress) gamete transmission in their own favour at a fitness cost, allowing for stable polymorphism.

Results

Here we show temporal correlations between Y-chromosomal haplotype frequencies and foetal sex ratios in the KNP buffalo population, suggesting SR genes. Frequencies varied by a factor of five; too high to be alternatively explained by Y-chromosomal effects on pregnancy loss. Sex ratios were male-biased during wet and female-biased during dry periods (male proportion: 0.47-0.53), seasonally and annually. Both wet and dry periods were associated with a specific haplotype indicating a SR distorter and SR suppressor, respectively.

Conclusions

The distinctive properties suggested for explaining Y-chromosomal polymorphism in African buffalo may not be restricted to this species alone. SR genes may play a broader and largely overlooked role in mammalian sex-ratio variation.

Intradermal tuberculin testing of wild African lions (Panthera leo) naturally exposed to infection with Mycobacterium bovis

African lions in the southern half of Kruger National Park (KNP) are infected with Mycobacterium bovis. Historically, reliable detection of mycobacteriosis in lions was limited to necropsy and microbiological analysis of lesion material collected from emaciated and ailing or repeat-offender lions. We report on a method of cervical intradermal tuberculin testing of lions and its interpretation capable of identifying natural exposure to M. bovis. Infected lions (n=52/95) were identified by detailed necropsy and mycobacterial culture. A large proportion of these confirmed infected lions (45/52) showed distinct responses to bovine tuberculin purified protein derivative (PPD) while responses to avian tuberculin PPD were variable and smaller. Confirmed uninfected lions from non-infected areas (n=11) responded variably to avian tuberculin PPD only. Various non-tuberculous mycobacteria (NTM) were cultured from 45/95 lions examined, of which 21/45 were co-infected with M. bovis. Co-infection with M. bovis and NTM did not influence skin reactions to bovine tuberculin PPD. Avian tuberculin PPD skin reactions were larger in M. bovis-infected lions compared to uninfected ones. Since NTM co-infections are likely to influence the outcome of skin testing, stricter test interpretation criteria were applied. When test data of bovine tuberculin PPD tests were considered on their own, as for a single skin test, sensitivity increased (80.8-86.5%) but false positive rate for true negatives (18.75%) remained unchanged. Finally, the adapted skin test procedure was shown not to be impeded by persistent Feline Immunodeficiency Virus(Ple) co-infection.

Estimating lion population variables: prey and disease effects in Kruger National Park, South Africa

Context. Lion (Panthera leo Linnaeus, 1758) populations experience a range of ecological and human influences that affect their demography. Few lion populations have reliable estimates of population size, trends in these, or demographic profiles. Threats such as those imposed by diseases are thus hard to evaluate and respond to. Aims. To calibrate call-up stations and define survey effort required to achieve estimates with known precision, and extract age structures and estimate survival rates, to estimate lion numbers, sex and age structure and survival rates, and then to evaluate the effect of bovine tuberculosis (bTB) on estimates of lion density and survival. Methods.By using call-up stations, we developed a statistically robust approach to estimate selected population variables and evaluated the perceived threat of bTB in landscapes of varying prey biomass in the Kruger National Park. Key results. The size of the lion population was stable, although long intervals between present and historical estimates limit this conclusion. Density and survival rates associated positively with prey biomass, and a positive association was detected between the survival rate and bTB prevalence, with survival being higher in areas that had high prevalence of bTB. Male survival was lower than female survival, disregarding the effects of prey biomass or bTB prevalence. Body condition of lions was high, with scores lower at low to medium prey density. Conclusions. The effect of an exotic disease on the Kruger lion population may be negligible at present. Intra-specific competition in areas where lions live at high densities affects survival rate. However, droughts could disrupt the hierarchical influences of prey biomass and bTB prevalence on lion densities and survival. Implications. To evaluate the effect of an exotic disease on lion demography, population surveys should include age- and sex-structure assessments, complemented with focal studies of fecundity. This reflects the importance of understanding host–disease dynamics to inform management options.

Classification of worldwide bovine tuberculosis risk factors in cattle: a stratified approach

The worldwide status of bovine tuberculosis (bTB) as a zoonosis remains of great concern. This article reviews the main risk factors for bTB in cattle based on a three-level classification: animal, herd and region/country level. A distinction is also made, whenever possible, between situations in developed and developing countries as the difference of context might have consequences in terms of risk of bTB. Recommendations are suggested to animal health professionals and scientists directly involved in the control and prevention of bTB in cattle. The determination of Millenium Development Goals for bTB is proposed to improve the control/eradication of the disease worldwide.

Habitat quality and heterogeneity influence distribution and behavior in African buffalo (Syncerus caffer)

Top-down effects of predators on prey behavior and population dynamics have been extensively studied. However, some populations of very large herbivores appear to be regulated primarily from the bottom up. Given the importance of food resources to these large herbivores, it is reasonable to expect that forage heterogeneity (variation in quality and quantity) affects individual and group behaviors as well as distribution on the landscape. Forage heterogeneity is often strongly driven by underlying soils, so substrate characteristics may indirectly drive herbivore behavior and distribution. Forage heterogeneity may further interact with predation risk to influence prey behavior and distribution. Here we examine differences in spatial distribution, home range size, and grouping behaviors of African buffalo as they relate to geologic substrate (granite and basalt) and variation in food quality and quantity. In this study, we use satellite imagery, forage quantity data, and three years of radio-tracking data to assess how forage quality, quantity, and heterogeneity affect the distribution and individual and herd behavior of African buffalo. We found that buffalo in an overall poorer foraging environment keyed-in on exceptionally high-quality areas, whereas those foraging in a more uniform, higher-quality area used areas of below-average quality. Buffalo foraging in the poorer-quality environment had smaller home range sizes, were in smaller groups, and tended to be farther from water sources than those foraging in the higher-quality environment. These differences may be due to buffalo creating or maintaining nutrient hotspots (small, high-quality foraging areas) in otherwise low-quality foraging areas, and the location of these hotspots may in part be determined by patterns of predation risk.

Bovine tuberculosis in southern African wildlife: a multi-species host-pathogen system

This review examines the current situation of bovine tuberculosis (bTB) in southern African savannah systems, and uses theory on multi-species host-pathogen systems to suggest possible options for future research and management. In southern Africa, the buffalo (Syncerus caffer) and the Kafue lechwe [Marsh antelope] (Kobus leche) have been found to be maintenance hosts for this disease, but the importance of other host species is becoming apparent. The role of other host species in the maintenance and spread of the disease varies, depending on the spatial distribution and resource utilization patterns of the species, disease susceptibility, transmission modes and the ecology of both host(s) and vector(s). Future research needs to identify the pathogenicity of bTB in each of the host species, and the mechanisms and rates of inter- and intra-specific transmission among different species, in order to develop multi-host models to understand the development and spread of the disease.