'One Health´ approach to end zoonotic TB

Mycobacterium bovis has a wide host range causing TB in animals, both in wildlife and cattle (bovine TB bTB), and in humans (zoonotic TB zTB). The real burden of bovine and zoonotic TB (b/zTB) remains unknown due to diagnostic challenges. Although progress has been made to reduce the burden of TB, b/zTB has been neglected in low- and middle-income countries (LMICs) with little improvement in prevention, diagnosis or treatment. Using Tanzania as a case study, because of its high TB burden, large wildlife diversity and wide reliance on livestock, we developed an approach to comprehensively estimate the burden and implement multidisciplinary actions against b/zTB. We performed a review of the literature on b/zTB, but there is a lack of available data on the b/zTB burden in Tanzania and, notably, on epidemiological indicators other than incidence. We propose a five-action programme to address b/zTB in Tanzania, and we believe our proposed approach could benefit other LMICs as it operates by implementing and strengthening surveillance and health delivery. The resulting knowledge and system organisation could further prevent and mitigate the effects of such conditions on human and animal health, livestock production, population livelihood and the economy.

How can we realise the full potential of animal health systems for delivering development and health outcomes?

Animal health services play an essential role in supporting livestock production, with the potential to address the challenges of hunger, poverty, health, social justice and environmental health as part of the path towards the Sustainable Development Goal (SDG) defined in the United Nations, 2030 Agenda. However, the provision of animal health services remains chronically underfunded. Although the aspiration that ‘no one will be left behind' is core to the SDG agenda, animal health service provision still fails to meet the basic needs of many of the poorest livestock owners. This review draws largely on experience from Tanzania and highlights the obstacles to equitable provision of animal health services, as well as identifying opportunities for improvement. Delivery models that rely on owners paying for services, whether through the private sector or public?private partnerships, can be effective for diseases that are of clear economic importance to animal keepers, particularly in more market-orientated production systems, but are currently constrained by issues of access, affordability, availability and quality. Substantial challenges remain when attempting to control diseases that exert a major burden on animal or human health but are less well recognised, as well as in the delivery of veterinary public health or other public good interventions. Here, the authors propose solutions that focus on: improving awareness of the potential for animal health services to address the SDGs, particularly those concerning public and environmental health; linking this more explicitly with advocacy for increased investment; ensuring that the voices of stakeholders are heard, particularly those of the rural poor; and embracing a cross-cutting and expanded vision for animal health services to support more adaptive development of livestock systems.

Analysing livestock network data for infectious disease control: an argument for routine data collection in emerging economies

Livestock movements are an important mechanism of infectious disease transmission. Where these are well recorded, network analysis tools have been used to successfully identify system properties, highlight vulnerabilities to transmission, and inform targeted surveillance and control. Here we highlight the main uses of network properties in understanding livestock disease epidemiology and discuss statistical approaches to infer network characteristics from biased or fragmented datasets. We use a 'hurdle model' approach that predicts (i) the probability of movement and (ii) the number of livestock moved to generate synthetic 'complete' networks of movements between administrative wards, exploiting routinely collected government movement permit data from northern Tanzania. We demonstrate that this model captures a significant amount of the observed variation. Combining the cattle movement network with a spatial between-ward contact layer, we create a multiplex, over which we simulated the spread of 'fast' ( R₀ = 3) and 'slow' ( R₀ = 1.5) pathogens, and assess the effects of random versus targeted disease control interventions (vaccination and movement ban). The targeted interventions substantially outperform those randomly implemented for both fast and slow pathogens. Our findings provide motivation to encourage routine collection and centralization of movement data to construct representative networks. This article is part of the theme issue 'Modelling infectious disease outbreaks in humans, animals and plants: epidemic forecasting and control'. This theme issue is linked with the earlier issue 'Modelling infectious disease outbreaks in humans, animals and plants: approaches and important themes'.

Street-level diplomacy and local enforcement for meat safety in northern Tanzania: knowledge, pragmatism and trust

BACKGROUND

With increasing demand for red meat in Tanzania comes heightened potential for zoonotic infections in animals and humans that disproportionately affect poor communities. A range of frontline government employees work to protect public health, providing services for people engaged in animal-based livelihoods (livestock owners and butchers), and enforcing meat safety and food premises standards. In contrast to literature which emphasises the inadequacy of extension support and food safety policy implementation in low- and middle-income countries, this paper foregrounds the 'street-level diplomacy' deployed by frontline actors operating in challenging contexts.

METHODS

This research is based on semi-structured interviews with 61 government employees, including livestock extension officers/meat inspectors and health officers, across 10 randomly-selected rural and urban wards.

RESULTS

Frontline actors combined formal and informal strategies including the leveraging of formal policy texts and relationships with other state employees, remaining flexible and recognising that poverty constrained people's ability to comply with health regulations. They emphasised the need to work with livestock keepers and butchers to build their knowledge to self-regulate and to work collaboratively to ensure meat safety. Remaining adaptive and being hesitant to act punitively unless absolutely necessary cultivated trust and positive relations, making those engaged in animal-based livelihoods more open to learning from and cooperating with extension officers and inspectors. This may result in higher levels of meat safety than might be the case if frontline actors stringently enforced regulations.

CONCLUSION

The current tendency to view frontline actors' partial enforcement of meat safety regulations as a failure obscures the creative and proactive ways in which they seek to ensure meat safety in a context of limited resources. Their application of 'street-level diplomacy' enables them to be sensitive to local socio-economic realities, to respect local social norms and expectations and to build support for health safety interventions when necessary. More explicitly acknowledging the role of trust and positive state-society relations and the diplomatic skills deployed by frontline actors as a formal part of their inspection duties offers new perspectives and enhanced understandings on the complicated nature of their work and what might be done to support them.

Proof of concept of mass dog vaccination for thecontrol and elimination of canine rabies

For more than 100 years, canine rabies vaccination has been available as a tool for rabies control and elimination. However, domestic dogs still remain a major reservoir for rabies, and although canine rabies has been eliminated through mass dog vaccination in some parts of the world, the disease continues to kill tens of thousands of people every year in Africa and Asia. This review focuses on the situation on those two continents, presenting evidence to show that canine rabies elimination is both epidemiologically and operationally feasible, and could be achieved across a wide range of settings in Africa and Asia. The challenges of achieving the large-scale, comprehensive dog vaccination coverage that is required are discussed, and opportunities for developing new strategies that generate multiple benefits for human and animal health and welfare are highlighted. Finally, the substantial progress that has been made in developing the tools, partnerships and frameworks needed to move towards global canine rabies elimination is outlined.

Direct detection and characterization of foot-and-mouth disease virus in East Africa using a field-ready real-time PCR platform

Effective control and monitoring of foot-and-mouth disease (FMD) relies upon rapid and accurate disease confirmation. Currently, clinical samples are usually tested in reference laboratories using standardized assays recommended by The World Organisation for Animal Health (OIE). However, the requirements for prompt and serotype-specific diagnosis during FMD outbreaks, and the need to establish robust laboratory testing capacity in FMD-endemic countries have motivated the development of simple diagnostic platforms to support local decision-making. Using a portable thermocycler, the T-COR™ 8, this study describes the laboratory and field evaluation of a commercially available, lyophilized pan-serotype-specific real-time RT-PCR (rRT-PCR) assay and a newly available FMD virus (FMDV) typing assay (East Africa-specific for serotypes: O, A, Southern African Territories [SAT] 1 and 2). Analytical sensitivity, diagnostic sensitivity and specificity of the pan-serotype-specific lyophilized assay were comparable to that of an OIE-recommended laboratory-based rRT-PCR (determined using a panel of 57 FMDV-positive samples and six non-FMDV vesicular disease samples for differential diagnosis). The FMDV-typing assay was able to correctly identify the serotype of 33/36 FMDV-positive samples (no cross-reactivity between serotypes was evident). Furthermore, the assays were able to accurately detect and type FMDV RNA in multiple sample types, including epithelial tissue suspensions, serum, oesophageal-pharyngeal (OP) fluid and oral swabs, both with and without the use of nucleic acid extraction. When deployed in laboratory and field settings in Tanzania, Kenya and Ethiopia, both assays reliably detected and serotyped FMDV RNA in samples (n = 144) collected from pre-clinical, clinical and clinically recovered cattle. These data support the use of field-ready rRT-PCR platforms in endemic settings for simple, highly sensitive and rapid detection and/or characterization of FMDV.

One Health contributions towards more effective and equitable approaches to health in low- and middle-income countries

Emerging zoonoses with pandemic potential are a stated priority for the global health security agenda, but endemic zoonoses also have a major societal impact in low-resource settings. Although many endemic zoonoses can be treated, timely diagnosis and appropriate clinical management of human cases is often challenging. Preventive 'One Health' interventions, e.g. interventions in animal populations that generate human health benefits, may provide a useful approach to overcoming some of these challenges. Effective strategies, such as animal vaccination, already exist for the prevention, control and elimination of many endemic zoonoses, including rabies, and several livestock zoonoses (e.g. brucellosis, leptospirosis, Q fever) that are important causes of human febrile illness and livestock productivity losses in low- and middle-income countries. We make the case that, for these diseases, One Health interventions have the potential to be more effective and generate more equitable benefits for human health and livelihoods, particularly in rural areas, than approaches that rely exclusively on treatment of human cases. We hypothesize that applying One Health interventions to tackle these health challenges will help to build trust, community engagement and cross-sectoral collaboration, which will in turn strengthen the capacity of fragile health systems to respond to the threat of emerging zoonoses and other future health challenges. One Health interventions thus have the potential to align the ongoing needs of disadvantaged communities with the concerns of the broader global community, providing a pragmatic and equitable approach to meeting the global goals for sustainable development and supporting the global health security agenda.This article is part of the themed issue 'One Health for a changing world: zoonoses, ecosystems and human well-being'.

Evaluation of Two Lyophilized Molecular Assays to Rapidly Detect Foot-and-Mouth Disease Virus Directly from Clinical Samples in Field Settings

Accurate, timely diagnosis is essential for the control, monitoring and eradication of foot-and-mouth disease (FMD). Clinical samples from suspect cases are normally tested at reference laboratories. However, transport of samples to these centralized facilities can be a lengthy process that can impose delays on critical decision making. These concerns have motivated work to evaluate simple-to-use technologies, including molecular-based diagnostic platforms, that can be deployed closer to suspect cases of FMD. In this context, FMD virus (FMDV)-specific reverse transcription loop-mediated isothermal amplification (RT-LAMP) and real-time RT-PCR (rRT-PCR) assays, compatible with simple sample preparation methods and in situ visualization, have been developed which share equivalent analytical sensitivity with laboratory-based rRT-PCR. However, the lack of robust 'ready-to-use kits' that utilize stabilized reagents limits the deployment of these tests into field settings. To address this gap, this study describes the performance of lyophilized rRT-PCR and RT-LAMP assays to detect FMDV. Both of these assays are compatible with the use of fluorescence to monitor amplification in real-time, and for the RT-LAMP assays end point detection could also be achieved using molecular lateral flow devices. Lyophilization of reagents did not adversely affect the performance of the assays. Importantly, when these assays were deployed into challenging laboratory and field settings within East Africa they proved to be reliable in their ability to detect FMDV in a range of clinical samples from acutely infected as well as convalescent cattle. These data support the use of highly sensitive molecular assays into field settings for simple and rapid detection of FMDV.

A field vaccine trial in Tanzania demonstrates partial protection against malignant catarrhal fever in cattle

Malignant catarrhal fever (MCF) is a fatal lymphoproliferative disease of cattle that, in East Africa, results from transmission of the causative virus, alcelaphine herpesvirus 1 (AlHV-1), from wildebeest. A vaccine field trial involving an attenuated AlHV-1 virus vaccine was performed over two wildebeest calving seasons on the Simanjiro Plain of northern Tanzania. Each of the two phases of the field trial consisted of groups of 50 vaccinated and unvaccinated cattle, which were subsequently exposed to AlHV-1 challenge by herding toward wildebeest. Vaccination resulted in the induction of virus-specific and virus-neutralizing antibodies. Some cattle in the unvaccinated groups also developed virus-specific antibody responses but only after the start of the challenge phase of the trial. PCR of DNA from blood samples detected AlHV-1 infection in both groups of cattle but the frequency of infection was significantly lower in the vaccinated groups. Some infected animals showed clinical signs suggestive of MCF but few animals went on to develop fatal MCF, with similar numbers in vaccinated and unvaccinated groups. This study demonstrated a baseline level of MCF-seropositivity among cattle in northern Tanzania of 1% and showed that AlHV-1 virus-neutralizing antibodies could be induced in Tanzanian zebu shorthorn cross cattle by our attenuated vaccine, a correlate of protection in previous experimental trials. The vaccine reduced infection rates by 56% in cattle exposed to wildebeest but protection from fatal MCF could not be determined due to the low number of fatal cases.

Effective vaccination against rabies in puppies in rabies endemic regions

In rabies endemic regions, a proportionally higher incidence of rabies is often reported in dogs younger than 12 months of age, which includes puppies less than 3 months of age; this presents a serious risk to public health. The higher incidence of rabies in young dogs may be the effect of low vaccination coverage in this age class, partly as a result of the perception that immature immune systems and maternal antibodies inhibit seroconversion to rabies vaccine in puppies less than three months of age. Therefore, to test this perception, the authors report the virus neutralising antibody titres from 27 dogs that were vaccinated with high quality, inactivated rabies vaccine aged three months of age and under as part of larger serological studies undertaken in Gauteng Province, South Africa, and the Serengeti District, Tanzania. All of these dogs seroconverted to a single dose of vaccine with no adverse reactions reported and with postvaccinal peak titres ranging from 2.0 IU/ml to 90.5 IU/ml. In light of these results, and the risk of human beings contracting rabies from close contact with puppies, the authors recommend that all dogs in rabies endemic regions, including those less than three months of age, are vaccinated with high quality, inactivated vaccine.

Ecology and conservation: contributions to One Health

Although One Health is widely promoted as a more effective approach towards human, animal and ecosystem health, the momentum is still driven largely by health professionals, predominantly from the veterinary sector. While few can doubt the merits of interdisciplinary One Health approaches to tackle complex health problems, operating across the disciplines still presents many challenges. This paper focuses on the contributions of partners from ecology and conservation to One Health approaches, and identifies four broad areas which could act as a focus for practical engagement and bring ecological and conservation objectives more to the forefront of the One Health agenda: i) developing initiatives with shared conservation and health objectives, particularly in and around protected areas and including programmes addressing human reproductive health and mental health; ii) broadening concepts of health to extend beyond indicators of disease to include the assessment of ecological impacts; iii) the integration of ecological and epidemiological monitoring systems within protected areas to support conservation management and wildlife disease surveillance; iv) building partnerships to bring conservation, health, development and animal welfare agencies together to combat threats to global biodiversity and health from the international trade in wildlife and wildlife products.

Urban domestic dog populations as a source of canine distemper virus for wild carnivores in the Coquimbo region of Chile

Urban areas can support dog populations dense enough to maintain canine distemper virus (CDV) and can be a source of infection for rural dogs and free-ranging carnivores. The aim of this study was to investigate the relationships between urban and rural domestic dog and wild carnivore populations and their effects on the epidemiology of CDV to explain retrospectively a CD outbreak in wild foxes in 2003. From 2005 to 2007 a cross-sectional household questionnaire survey was conducted in Coquimbo and Ovalle cities, in three towns and in rural sites along two transects from these cities to the Fray Jorge National Park (FJNP) in the Coquimbo region, Chile. Blood samples were collected from unvaccinated dogs at surveyed households and from free-ranging foxes in rural areas along the transects. The seroprevalence of CDV in domestic dogs was higher in urban than in rural areas and in the later was highest in dogs born before 2001-2002. The seroprevalence of CDV in foxes was higher in areas closer to human settlements. A high seroprevalence in dogs born before 2001-2002 further supports a link between CDV patterns in rural dog and fox populations. In our study area, urban dogs are proposed to be the source of CDV infection to wild carnivores. The large dog population size and density detected in Coquimbo and Ovalle provides optimal conditions for maintaining a large and dense susceptible population of dogs, which can act as a reservoir for highly infectious diseases and could have been the source of infection in the CD outbreak in wild foxes.

Demography of domestic dogs in rural and urban areas of the Coquimbo region of Chile and implications for disease transmission

A cross-sectional household questionnaire survey was conducted along two transects (80 and 45km long) from Coquimbo and Ovalle cities to the Fray Jorge National Park (FJNP) in the Coquimbo region of Chile in 2005-2007 to investigate the demography of dogs in the context of a study of canine infectious diseases. Data were collected on the number of dogs per household, fecundity, mortality, and sex and age distribution. The results from 1021 households indicated that dog ownership was common, with a higher proportion of households owning dogs in rural areas (89%), than in towns (63%) or cities (49%). Dog density ranged from 1380+/-183 to 1509+/-972 dogs km(-2) in cities, from 119+/-18 to 1544+/-172 dogs km(-2) in towns, and from 1.0+/-0.4 to 15.9+/-0.4 dogs km(-2) in rural sites. The dog population was estimated to be growing at 20% in cities, 19% in towns and 9% in rural areas. The human:dog ratio ranged from 5.2 to 6.2 in cities, from 2.3 to 5.3 in towns, and from 1.1 to 2.1 in rural areas. A high percentage of owned dogs was always allowed to roam freely in the different areas (27%, 50% and 67% in cities, towns and rural areas, respectively). Observations of free-roaming dogs of unknown owner were reported from a greater proportion of respondents in cities (74%), followed by towns (51%) and finally by rural areas (21%). Overall only 3% of dogs had been castrated. In addition, only 29% of dogs were reported to have been vaccinated against canine distemper virus (CDV) and 30% against canine parvovirus (CPV). The higher population size and density, higher growth rate and a higher turnover of domestic dogs in urban than in rural areas and the poorly supervised and inadequately vaccinated dog populations in urban areas suggest that urban areas are more likely to provide suitable conditions for dogs to acts as reservoirs of pathogenic infections.

Development and use of real-time PCR to detect and quantify Mycoplasma haemocanis and "Candidatus Mycoplasma haematoparvum" in dogs

Two canine haemoplasma species have been recognised to date; Mycoplasma haemocanis (Mhc), which has been associated with anaemia in splenectomised or immunocompromised dogs, and “Candidatus Mycoplasma haematoparvum” (CMhp), recently described in an anaemic splenectomised dog undergoing chemotherapy. The study aim was to develop quantitative real-time PCR assays (qPCRs) incorporating an endogenous internal control to detect Mhc and CMhp and to apply these assays to DNA samples extracted from canine blood collected in Northern Tanzania (n = 100) and from dogs presented to a Trinidadian veterinary hospital (n = 185).

QPCRs specific for Mhc and CMhp were designed using 16S rRNA gene sequence data, and each was duplexed with an assay specific for canine glyceraldehyde-3-phosphate dehydrogenase (GAPDH). The assays detected ≤10 copies of a sequence-specific haemoplasma plasmid per reaction and neither assay showed cross-reactivity with 10⁶ copies of the sequence-specific plasmid from the non-target canine haemoplasma species.

Nineteen of the 100 Tanzanian samples (19%) were positive for Mhc alone and one (1%) was dually infected. One Trinidadian sample was negative for canine GAPDH DNA and was excluded from the study. Of the 184 remaining Trinidadian samples, nine (4.9%) were positive for Mhc alone, five (2.7%) for CMhp alone, and two (1.1%) dually infected.

This is the first report of canine haemoplasma qPCR assays that use an internal control to confirm the presence of amplifiable sample DNA, and their application to prevalence studies. Mhc was the most commonly detected canine haemoplasma species.

Rabies control in rural Africa: evaluating strategies for effective domestic dog vaccination

Effective vaccination campaigns need to reach a sufficient percentage of the population to eliminate disease and prevent future outbreaks, which for rabies is predicted to be 70%, at a cost that is economically and logistically sustainable. Domestic dog rabies has been increasing across most of sub-Saharan Africa indicating that dog vaccination programmes to date have been inadequate. We compare the effectiveness of a variety of dog vaccination strategies in terms of their cost and coverage in different community settings in rural Tanzania. Central-point (CP) vaccination was extremely effective in agro-pastoralist communities achieving a high coverage (>80%) at a low cost (US$5/dog) and inadequate (<20% coverage); combined approaches using CP and either house-to-house vaccination or trained community-based animal health workers were most effective with coverage exceeding 70%, although costs were still high (>US$6 and >US$4/dog, respectively). No single vaccination strategy is likely to be effective in all populations and therefore alternative approaches must be deployed under different settings. CP vaccination is cost-effective and efficient for the majority of dog populations in rural Tanzania and potentially elsewhere in sub-Saharan Africa, whereas a combination strategy is necessary in remote pastoralist communities. These results suggest that rabies control is logistically feasible across most of the developing world and that the annual costs of effective vaccination campaigns in Tanzania are likely to be affordable.

Molecular epidemiology identifies only a single rabies virus variant circulating in complex carnivore communities of the Serengeti

Understanding the transmission dynamics of generalist pathogens that infect multiple host species is essential for their effective control. Only by identifying those host populations that are critical to the permanent maintenance of the pathogen, as opposed to populations in which outbreaks are the result of 'spillover' infections, can control measures be appropriately directed. Rabies virus is capable of infecting a wide range of host species, but in many ecosystems, particular variants circulate among only a limited range of potential host populations. The Serengeti ecosystem (in northwestern Tanzania) supports a complex community of wild carnivores that are threatened by generalist pathogens that also circulate in domestic dog populations surrounding the park boundaries. While the combined assemblage of host species appears capable of permanently maintaining rabies in the ecosystem, little is known about the patterns of circulation within and between these host populations. Here we use molecular phylogenetics to test whether distinct virus-host associations occur in this species-rich carnivore community. Our analysis identifies a single major variant belonging to the group of southern Africa canid-associated viruses (Africa 1b) to be circulating within this ecosystem, and no evidence for species-specific grouping. A statistical parsimony analysis of nucleoprotein and glycoprotein gene sequence data is consistent with both within- and between-species transmission events. While likely differential sampling effort between host species precludes a definitive inference, the results are most consistent with dogs comprising the reservoir of rabies and emphasize the importance of applying control efforts in dog populations.

Low-coverage vaccination strategies for the conservation of endangered species

The conventional objective of vaccination programmes is to eliminate infection by reducing the reproduction number of an infectious agent to less than one, which generally requires vaccination of the majority of individuals. In populations of endangered wildlife, the intervention required to deliver such coverage can be undesirable and impractical; however, endangered populations are increasingly threatened by outbreaks of infectious disease for which effective vaccines exist. As an alternative, wildlife epidemiologists could adopt a vaccination strategy that protects a population from the consequences of only the largest outbreaks of disease. Here we provide a successful example of this strategy in the Ethiopian wolf, the world's rarest canid, which persists in small subpopulations threatened by repeated outbreaks of rabies introduced by domestic dogs. On the basis of data from past outbreaks, we propose an approach that controls the spread of disease through habitat corridors between subpopulations and that requires only low vaccination coverage. This approach reduces the extent of rabies outbreaks and should significantly enhance the long-term persistence of the population. Our study shows that vaccination used to enhance metapopulation persistence through elimination of the largest outbreaks of disease requires lower coverage than the conventional objective of reducing the reproduction number of an infectious agent to less than one.

The epidemiology of animal bite injuries in Uganda and projections of the burden of rabies

OBJECTIVES

Rabies is a global problem, although it is often under-reported in developing countries. We aimed at describing the profile of patients presenting to health centres with animal bite injuries in Uganda, and use a predictive model to estimate the mortality of rabies at a national level.

METHODS

We conducted a passive surveillance study in Uganda based in a random sample of health centres supplied with rabies vaccine to determine the characteristics of bite injury patients and establish the age and sex profiles of patients, the site of bites and their severity, wound management techniques and details of the vaccination course given. We also applied a decision tree model to the data to estimate the rabies mortality from the bite injury data using an established protocol.

RESULTS

We found that most patients are bitten by dogs, and that a considerable proportion of these are young children, who are at greater risk of developing rabies in the absence of treatment due to the location of the bites they receive. From conservative parameter estimates, we estimate that in the absence of post-exposure prophylaxis (PET), 592 (95% CI 345-920) deaths would occur, and that if one dose of PET is sufficient for protection following a rabid animal bite, 20 (95% CI 5-50) deaths would occur annually. If a complete course of PET is required for protection following a rabid animal bite, up to 210 (95% CI 115-359) deaths would occur, as 41% of patients did not complete their course of PET.

CONCLUSIONS

Active animal bite surveillance studies are required to improve our mortality estimates and determine the true burden of rabies in the Ugandan population. We emphasize the need for small-scale active case detection studies and improved data on the recognition of rabies in dogs as inputs for improving national-level estimates of rabies mortality.

Tuberculosis in Tanzanian Wildlife

Bovine tuberculosis, caused by Mycobacterium bovis, is a pathogen of growing concern in free-ranging wildlife in Africa, but little is known about the disease in Tanzanian wildlife. Here, we report the infection status of Mycobacterium bovis in a range of wildlife species sampled from protected areas in northern Tanzania. M. bovis was isolated from 11.1% (2/18) migratory wildebeest (Connochaetes taurinus) and 11.1% (1/9) topi (Damaliscus lunatus) sampled systematically in 2000 during a meat cropping program in the Serengeti ecosystem, and from one wildebeest and one lesser kudu (Tragelaphus imberbis) killed by sport hunters adjacent to Tarangire National Park. A tuberculosis antibody enzyme immunoassay (EIA) was used to screen serum samples collected from 184 Serengeti lions (Panthera leo) and 19 lions from Ngorongoro Crater sampled between 1985 and 2000. Samples from 212 ungulates collected throughout the protected area network between 1998 and 2001 also were tested by EIA. Serological assays detected antibodies to M. bovis in 4% of Serengeti lions; one positive lion was sampled in 1984. Antibodies were detected in one of 17 (6%) buffalo (Syncerus caffer) in Tarangire and one of 41 (2%) wildebeest in the Serengeti. This study confirms for the first time the presence of bovine tuberculosis in wildlife of northern Tanzania, but further investigation is required to assess the impact on wildlife populations and the role of different wildlife species in maintenance and transmission.

Mycobacterial adenitis: role of Mycobacterium bovis, non-tuberculous mycobacteria, HIV infection, and risk factors in Arusha, Tanzania

OBJECTIVE

To assess risk factors and mycobacterial agents in mycobacterial adenitis.

DESIGN

Cross sectional involving comparison analysis of high-risk groups.

SETTING

Seven hospitals in rural and semi-rural districts of Arusha.

SUBJECTS

The study comprised of 457 patients of clinically diagnosed mycobacterial adenitis.

INTERVENTIONS

Biopsy materials were cultured and identification of mycobacterial isolates, and HIV infection testing were performed using standard methods. A questionnaire was used to establish information for assessing risk factors.

MAIN OUTCOME MEASURES

Proportions of mycobacterial isolates, risk factors and odds ratios.

RESULTS

Of the 457 specimens, 65(14.2%) were culture positive. Isolates identified were M. bovis, 7(10.8%) M. tuberculosis, 27(41.5%) and non-tuberculous mycobacteria 31(47.7%). HIV infection and ingestion of raw milk were linked with increased risk of M. bovis infection by OR of 13.6 (95% CI, 1.7 - 109.9) and 15.28 (3.26 - 71.7), respectively. On multivariate analysis, an OR of 16.2 (1.3 - 201.3) for having M. bovis adenitis was linked to HIV infection, raw milk and houses with poor ventilation. An OR of 5.2 (1.2 - 20.6) for non-tuberculous mycobacterial adenitis was linked to history of TB in the family, HIV infection, raw milk, raw animal products and poor knowledge on transmission of tuberculosis.

CONCLUSIONS

M. bovis caused one out of ten cases of culture positive mycobacterial adenitis. Non-tuberculous mycobacteria were more common than M. tuberculosis (50% and 40% of the cases, respectively). HIV infection and raw animal products are among the risk factors identified for M. bovis and non-tuberculous mycobacterial adenitis.

Tribal differences in perception of tuberculosis: a possible role in tuberculosis control in Arusha, Tanzania

SETTING

Arusha, Tanzania.

OBJECTIVE

To determine tribal differences in knowledge and practices that might influence tuberculosis control.

METHOD

Twenty-seven villages were selected randomly out of 242 villages in four districts. In each village, a general and a livestock keeping group were selected at random. The households were home-visited and 426 family members were interviewed.

RESULTS

On average, 40% of respondents practised habits that might expose them to both bovine and human tuberculosis. The Barabaig tribe had a significantly higher number of respondents (50%, chi2(2) = 5.1, P = 0.024) who did not boil milk. Eating uncooked meat or meat products was practised by 17.9% of all respondents. The habit was practised more by Iraqw (21.1%, chi2(2) = 6.9, P = 0.008) and Barabaig (31.6%, chi2(2) = 5.6, P = 0.016) than other tribes. About 75% of the respondents had a poor knowledge of tuberculosis.

CONCLUSION

All tribes had habits and beliefs that might expose them to both bovine and human tuberculosis. The Iraqw and Barabaig tribes practised such habits more than other tribes. Knowledge of tuberculosis was limited in all tribes.

The role of livestock keeping in tuberculosis trends in Arusha, Tanzania

SETTING

Arusha, Tanzania.

OBJECTIVE

To assess risk factors that might influence TB control in the general population and in livestock-keepers.

METHODS

Of 242 villages in four districts, 27 were selected randomly. In each village, a general and a livestock-keeping group were selected at random. The households were home-visited and 426 family members were interviewed.

RESULTS

On average, three-quarters of households practised at least one risk activity for transmission of zoonotic tuberculosis, and respondents had poor knowledge about tuberculosis. In the livestock-keeping group, the risks of having a tuberculosis patient in the family were determined by poor ventilation (OR 2.6, 95% CI 1.1-6.5), confining livestock indoors with people (OR 2.3, 95%CI 1.1-5.0) and multiple determinants including poor ventilation (OR 13.5, 95% CI 2.5-71.7). Risk activities and the risks of having a tuberculosis patient in a family were significantly higher in the livestock-keeping group.

CONCLUSIONS

The respondents had limited knowledge about tuberculosis, and the households had practices that posed potential risks for both human and bovine tuberculosis infection. Poor ventilation and confining livestock indoors were associated with tuberculosis spread in the households. These risks were observed more in the livestock-keeping group than in the general population group.

A dog rabies vaccination campaign in rural Africa: impact on the incidence of dog rabies and human dog-bite injuries

Despite the availability of safe and effective rabies vaccines, the incidence of dog rabies has been increasing throughout much of sub-Saharan Africa. Here we describe a vaccination strategy that has resulted in successful control of rabies in a rural dog population of Northwestern Tanzania. From October 1996 to February 2001, four central-point dog vaccination campaigns were conducted in villages within Serengeti District with a mean interval between campaigns of 338, 319 and 456 days. Vaccination coverage of the dog population was estimated from household questionnaires as 64.5, 61.1, 70.6 and 73.7% following each of the four campaigns, respectively. The incidence of dog rabies declined significantly in Serengeti District falling by 70% after the first campaign and by 97% after the second campaign. Over the same period, the incidence of dog rabies did not differ significantly in unvaccinated control villages of Musoma District. The incidence of human bite injuries from suspected rabid dogs declined significantly in Serengeti District after dog vaccination but not in adjacent unvaccinated districts. Vaccination of 60-70% of dogs has been sufficient to control dog rabies in this area and to significantly reduce demand for human post-exposure rabies treatment. Dog-bite injuries can provide a valuable and accessible source of data for surveillance in countries where case incidence data are difficult to obtain.

Diseases of humans and their domestic mammals: pathogen characteristics, host range and the risk of emergence

Pathogens that can be transmitted between different host species are of fundamental interest and importance from public health, conservation and economic perspectives, yet systematic quantification of these pathogens is lacking. Here, pathogen characteristics, host range and risk factors determining disease emergence were analysed by constructing a database of disease-causing pathogens of humans and domestic mammals. The database consisted of 1415 pathogens causing disease in humans, 616 in livestock and 374 in domestic carnivores. Multihost pathogens were very prevalent among human pathogens (61.6%) and even more so among domestic mammal pathogens (livestock 77.3%, carnivores 90.0%). Pathogens able to infect human, domestic and wildlife hosts contained a similar proportion of disease-causing pathogens for all three host groups. One hundred and ninety-six pathogens were associated with emerging diseases, 175 in humans, 29 in livestock and 12 in domestic carnivores. Across all these groups, helminths and fungi were relatively unlikely to emerge whereas viruses, particularly RNA viruses, were highly likely to emerge. The ability of a pathogen to infect multiple hosts, particularly hosts in other taxonomic orders or wildlife, were also risk factors for emergence in human and livestock pathogens. There is clearly a need to understand the dynamics of infectious diseases in complex multihost communities in order to mitigate disease threats to public health, livestock economies and wildlife.

Serological and demographic evidence for domestic dogs as a source of canine distemper virus infection for Serengeti wildlife

Following an epidemic of canine distemper virus (CDV) in Serengeti lions in 1994, the role of domestic dogs in the epidemiology of the disease was investigated by serological and demographic analyses. From 1992 to 1994, data were collected from two domestic dog populations bordering the Serengeti National Park. Several lines of evidence indicated that patterns of CDV infection differed significantly between higher-density dog populations of Serengeti District to the west of the park and lower-density populations of Ngorongoro District to the south-east: (a) CDV age-seroprevalence patterns differed significantly between years in Ngorongoro District populations but not in Serengeti District populations; (b) CDV seropositive pups (<12 months of age) were detected in Ngorongoro District only in 1994, whereas a proportion of pups in Serengeti District were seropositive in each year of the study; (c) in Ngorongoro District, the proportion of deaths attributed to disease was significantly higher in 1994 than in 1993, whereas in Serengeti District, there was no significant difference in disease-related mortality between years; (d) in Ngorongoro District, significantly more CDV seronegative dogs than seropositive dogs died in 1994, whereas there was no difference in survival of CDV seropositives and seronegatives between years in Serengeti District. We concluded that, between 1992 and 1994, CDV persisted in higher-density dog populations of Serengeti District, but occurred only sporadically in lower-density Ngorongoro District populations. Data from Ngorongoro District are consistent with exposure of dogs to CDV in 1991 and 1994, but not in 1992 and 1993. These findings suggest that higher-density domestic dog populations to the west of the Serengeti National Park were a more likely source of CDV infection for wildlife during 1994 than lower-density pastoralist dogs to the south and east of the park.

A rabies serosurvey of domestic dogs in rural Tanzania: results of a rapid fluorescent focus inhibition test (RFFIT) and a liquid-phase blocking ELISA used in parallel

During a serosurvey of domestic dogs in Tanzania, a rapid fluorescent focus inhibition test (RFFIT) and a liquid-phase blocking ELISA (LPBE) were used to measure rabies antibodies in vaccinated and unvaccinated dogs. Post-vaccination titres measured by LPBE correlated closely with those found by RFFIT. Of 567 unvaccinated dogs tested using the LPBE, 42 (7.4%) were seropositive, with titres exceeding 32. Of this group, 233 dogs were tested using the RFFIT and 115 (49.4%) were seropositive, with titres exceeding 0.5 IU/ml. Two lines of evidence pointed to the greater specificity of the LPBE when measuring rabies antibodies induced by natural infections: (a) no seropositive dogs were detected among the 162 unvaccinated dogs from the rabies-free island of Pemba, Tanzania, when using LPBE, whereas 15/145 (10.3%) dogs of the same group were seropositive using RFFIT; (b) among Tanzanian dogs there was a close association between the location of rabies cases and location of seropositive dogs when using LPBE, but not when using RFFIT. These results suggest that LPBE may be of value in rabies seroepidemiological studies and could be developed as a reference technique for the detection of rabies antibody in domestic dogs.

Royal Society of Tropical Medicine and Hygiene meeting at Manson House, London, 20 March 1997. Epidemiology and control of rabies. The growing problem of rabies in Africa

Although rabies in Africa is relatively insignificant in terms of human mortality, the disease is still relevant because of the high costs of rabies prevention. Over the past 2 decades, demographic, economic and sociopolitical trends in Africa have increasingly favoured the persistence and spread of rabies, while limiting the effectiveness of control measures. Dog rabies predominates throughout most of Africa; the domestic dog is the principal reservoir host as well as the most important source of infection for people. However, wild-life rabies is increasingly a concern, both as a threat to endangered wildlife populations and because of the possible emergence of new maintenance hosts.

A canine distemper virus epidemic in Serengeti lions (Panthera leo)

Canine distemper virus (CDV) is thought to have caused several fatal epidemics in canids within the Serengeti-Mara ecosystem of East Africa, affecting silver-backed jackals (Canis mesomelas) and bat-eared foxes (Otocyon megalotis) in 1978 (ref. 1), and African wild dogs (Lycaon pictus) in 1991 (refs 2, 3). The large, closely monitored Serengeti lion population was not affected in these epidemics. However, an epidemic caused by a morbillivirus closely related to CDV emerged abruptly in the lion population of the Serengeti National Park, Tanzania, in early 1994, resulting in fatal neurological disease characterized by grand mal seizures and myoclonus; the lions that died had encephalitis and pneumonia. Here we report the identification of CDV from these lions, and the close phylogenetic relationship between CDV isolates from lions and domestic dogs. By August 1994, 85% of the Serengeti lion population had anti-CDV antibodies, and the epidemic spread north to lions in the Maasai Mara National reserve, Kenya, and uncounted hyaenas, bat-eared foxes, and leopards were also affected.

Maintenance of a microparasite infecting several host species: rabies in the Serengeti

Whether and how microparasites such as rabies persist in their host populations are among the fundamental questions of infectious disease epidemiology. Rabies is fatal disease of all mammalian species, but not all mammalian species can maintain the infection as reservoirs. The approach to control depends on which of the affected species do act as reservoirs. Bringing together old and new data, we examine here the role of wild and domestic animals in maintaining rabies in the Serengeti region of Tanzania, presenting our findings in two parts. In Part I, we argue that domestic dogs are the likely reservoirs because: (1) rabies has been continuously present in the dog population since its (re)introduction in 1977, whilst (2) wildlife cases have been very rare over this period, despite intensive study of Serengeti carnivores; (3) outbreaks of rabies in wild canids (jackals) elsewhere in Africa (Zimbabwe) have followed, rather than preceded, outbreaks in the dog population; (4) all viruses isolated from wild carnivores in the Serengeti ecosystem (including the Kenyan Masai Mara) are antigenically and genetically indistinguishable from the typical domestic dog strain; (5) dog rabies control in the Serengeti between 1958-77 apparently eliminated the disease from both dogs and wildlife. Having identified dogs as reservoirs, Part II explores some possible mechanisms of maintenance in dog populations. In theory, infection is more likely to be maintained at higher dog densities, and we provide evidence that rabies is maintained in one district with a dog density > 5/km2, but not in two other districts with densities < 1/km2. Because 5 dogs/km2 is much lower than the expected density required for persistence, we go on to investigate the role of atypical infections, showing: (1) from serology, that a substantial proportion of healthy dogs in the Serengeti have detectable serum levels of rabies-specific antibody; (2) from mathematical models that, whilst we cannot be sure what seropositivity means, persistence in low-density dog populations is more likely if seropositives are infectious carriers, rather than slow-incubators or immunes.