Foot and mouth disease control strategies in Africa

Understanding what shapes disease control: An historical analysis of foot-and-mouth disease in Kenya

Interpreting the interplay between politics, social demographics and epidemiology is essential for understanding how a disease's occurrence and control evolve over time. Foot-and-mouth disease (FMD) virus was first detected in Kenya in 1915 and serotyped in 1932. This review aims to describe and appraise initiatives to control FMD in Kenya since its independence from British rule in 1964, using information from the scientific literature. We describe the historical dynamics of FMD epidemiology in the country and determine socio-political factors that have shaped the control strategies used. PubMed, Scopus, CAB abstracts, Science Direct, Web of Science and Google Scholar were used to search and retrieve papers, using predetermined search criteria encompassing FMD, Kenya and disease control programme descriptors. In total 1234 papers were identified and screened for relevance using the World Health Organization's guidelines for rapid review. Ultimately 69 references from this search were included, and information extracted and consolidated. These papers highlight that following independence, there was a structured effort to control FMD consisting of a compulsory subsidised vaccination programme in the Rift Valley with movement controls and quarantine when outbreaks occurred. This programme led to an initial decrease in recorded FMD outbreaks. However, endemic circulation continued and this programme was discontinued due to multiple factors, including political deprioritisation and changes in the structure of veterinary services. Only low levels of active surveillance have been applied since 1964; most surveillance is passive and relies on outbreak reports. Currently control focuses on outbreak management and a mixture of public- and privately-funded vaccination. This review highlights critical drivers influencing disease control programme implementation including veterinary service structure, the active participation of stakeholders with farming systems and availability of affordable and matched FMD vaccine. Additionally, it appraises the availability of historical information and draws attention to gaps in the historical record.

Economic impact assessment of foot-and-mouth disease burden and control in pastoral local dairy cattle production systems in Northern Nigeria: A cross-sectional survey

Milk has been envisaged as a major source of high-quality protein and bioavailable nutrients to humans. Its production is constraint by foot and mouth disease (FMD), a contagious viral disease of very high economic importance worldwide. This study was aimed at assessing the economic impact of FMD in pastoral dairy cattle herds in Nigeria and determines returns to investments in its control to better inform policy decisions. An interview questionnaire-based cross-sectional study was conducted in 660 nomadic and agro-pastoral dairy cattle herds in 2019. Economic impact analyses were conducted using the total economic cost and benefit-cost analysis models. Of the 660 pastoralists enrolled, 92.6% (n = 611) participated. Nomadic pastoralists constituted 50.7% (n = 310) of the respondents while 49.3% (n = 301) were agro-pastoralists. Most of the respondents (66.4%, n = 406) had no formal education. The value of visible losses to the herders was estimated at USD 15,591,694.30 and the cost of control by treatment of secondary infections was USD 463,673.70. The economic impact of FMD due to production losses and costs of treatment to pastoralists was estimated to be USD 16,055,368.00. Return on investment in FMD control was positive with a benefit-cost ratio of 33.6. The estimated total economic costs due to FMD have indicated that it is a disease of high economic importance to dairy production herds and must be controlled to assure food security, local incomes to herders, and protein requirement of human population, especially the children in FMD endemic countries.

Unrecognized circulation of SAT 1 foot-and-mouth disease virus in cattle herds around Queen Elizabeth National Park in Uganda

Background

Foot-and-mouth disease (FMD) is endemic in Uganda in spite of the control measures used. Various aspects of the maintenance and circulation of FMD viruses (FMDV) in Uganda are not well understood; these include the role of the African buffalo (Syncerus caffer) as a reservoir for FMDV. To better understand the epidemiology of FMD at the livestock-wildlife-interface, samples were collected from young, unvaccinated cattle from 24 pastoral herds that closely interact with wildlife around Queen Elizabeth National Park in Uganda, and analysed for evidence of FMDV infection.

Results

In total, 37 (15 %) of 247 serum samples had detectable antibodies against FMDV non-structural proteins (NSPs) using a pan-serotypic assay. Within these 37 sera, antibody titres ≥ 80 against the structural proteins of serotypes O, SAT 1, SAT 2 and SAT 3 were detected by ELISA in 5, 7, 4 and 3 samples, respectively, while neutralizing antibodies were only detected against serotype O in 3 samples. Two FMDV isolates, with identical VP1 coding sequences, were obtained from probang samples from clinically healthy calves from the same herd and are serotype SAT 1 (topotype IV (EA-I)). Based on the VP1 coding sequences, these viruses are distinct from previous cattle and buffalo SAT 1 FMDV isolates obtained from the same area (19–30 % nucleotide difference) and from the vaccine strain (TAN/155/71) used within Uganda (26 % nucleotide difference). Eight herds had only one or a few animals with antibodies against FMDV NSPs while six herds had more substantial evidence of prior infection with FMDV. There was no evidence for exposure to FMDV in the other ten herds.

Conclusions

The two identical SAT 1 FMDV VP1 sequences are distinct from former buffalo and cattle isolates from the same area, thus, transmission between buffalo and cattle was not demonstrated. These new SAT 1 FMDV isolates differed significantly from the vaccine strain used to control Ugandan FMD outbreaks, indicating a need for vaccine matching studies. Only six herds had clear serological evidence for exposure to O and SAT 1 FMDV. Scattered presence of antibodies against FMDV in other herds may be due to the occasional introduction of animals to the area or maternal antibodies from past infection and/or vaccination.

The evidence for asymptomatic FMDV infection has implications for disease control strategies in the area since this obstructs early disease detection that is based on clinical signs in FMDV infected animals.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-015-0616-1) contains supplementary material, which is available to authorized users.

Impacts of constrained culling and vaccination on control of foot and mouth disease in near-endemic settings: a pair approximation model

Many countries have eliminated foot and mouth disease (FMD), but outbreaks remain common in other countries. Rapid development of international trade in animals and animal products has increased the risk of disease introduction to FMD-free countries. Most mathematical models of FMD are tailored to settings that are normally disease-free, and few models have explored the impact of constrained control measures in a 'near-endemic' spatially distributed host population subject to frequent FMD re-introductions from nearby endemic wild populations, as characterizes many low-income, resource-limited countries. Here we construct a pair approximation model of FMD and investigate the impact of constraints on total vaccine supply for prophylactic and ring vaccination, and constraints on culling rates and cumulative culls. We incorporate natural immunity waning and vaccine waning, which are important factors for near-endemic populations. We find that, when vaccine supply is sufficiently limited, the optimal approach for minimizing cumulative infections combines rapid deployment of ring vaccination during outbreaks with a contrasting approach of careful rationing of prophylactic vaccination over the year, such that supplies last as long as possible (and with the bulk of vaccines dedicated toward prophylactic vaccination). Thus, for optimal long-term control of the disease by vaccination in near-endemic settings when vaccine supply is limited, it is best to spread out prophylactic vaccination as much as possible. Regardless of culling constraints, the optimal culling strategy is rapid identification of infected premises and their immediate contacts at the initial stages of an outbreak, and rapid culling of infected premises and farms deemed to be at high risk of infection (as opposed to culling only the infected farms). Optimal culling strategies are similar when social impact is the outcome of interest. We conclude that more FMD transmission models should be developed that are specific to the challenges of FMD control in near-endemic, low-income countries.

Dynamics and control of foot-and-mouth disease in endemic countries: a pair approximation model

Previous mathematical models of spatial farm-to-farm transmission of foot and mouth disease (FMD) have explored the impacts of control measures such as culling and vaccination during a single outbreak in a country normally free of FMD. As a result, these models do not include factors that are relevant to countries where FMD is endemic in some regions, like long-term waning natural and vaccine immunity, use of prophylactic vaccination and disease re-importations. These factors may have implications for disease dynamics and control, yet few models have been developed for FMD-endemic settings. Here we develop and study an SEIRV (susceptible-exposed-infectious-recovered-vaccinated) pair approximation model of FMD. We focus on long term dynamics by exploring characteristics of repeated outbreaks of FMD and their dependence on disease re-importation, loss of natural immunity, and vaccine waning. We find that the effectiveness of ring and prophylactic vaccination strongly depends on duration of natural immunity, rate of vaccine waning, and disease re-introduction rate. However, the number and magnitude of FMD outbreaks are generally more sensitive to the duration of natural immunity than the duration of vaccine immunity. If loss of natural immunity and/or vaccine waning happen rapidly, then multiple epidemic outbreaks result, making it difficult to eliminate the disease. Prophylactic vaccination is more effective than ring vaccination, at the same per capita vaccination rate. Finally, more frequent disease re-importation causes a higher cumulative number of infections, although a lower average epidemic peak. Our analysis demonstrates significant differences between dynamics in FMD-free settings versus FMD-endemic settings, and that dynamics in FMD-endemic settings can vary widely depending on factors such as the duration of natural and vaccine immunity and the rate of disease re-importations. We conclude that more mathematical models tailored to FMD-endemic countries should be developed that include these factors.

Foot and mouth disease in Zambia: Spatial and temporal distributions of outbreaks, assessment of clusters and implications for control

Zambia has been experiencing low livestock productivity as well as trade restrictions owing to the occurrence of foot and mouth disease (FMD), but little is known about the epidemiology of the disease in these endemic settings. The fundamental questions relate to the spatio-temporal distribution of FMD cases and what determines their occurrence. A retrospective review of FMD cases in Zambia from 1981 to 2012 was conducted using geographical information systems and the SaTScan software package. Information was collected from peer-reviewed journal articles, conference proceedings, laboratory reports, unpublished scientific reports and grey literature. A space–time permutation probability model using a varying time window of one year was used to scan for areas with high infection rates. The spatial scan statistic detected a significant purely spatial cluster around the Mbala–Isoka area between 2009 and 2012, with secondary clusters in Sesheke–Kazungula in 2007 and 2008, the Kafue flats in 2004 and 2005 and Livingstone in 2012. This study provides evidence of the existence of statistically significant FMD clusters and an increase in occurrence in Zambia between 2004 and 2012. The identified clusters agree with areas known to be at high risk of FMD. The FMD virus transmission dynamics and the heterogeneous variability in risk within these locations may need further investigation.

Foot-and-mouth disease: past, present and future

Foot-and-mouth disease (FMD) is a highly contagious disease of cloven-hoofed animals including cattle, pigs, sheep and many wildlife species. It can cause enormous economic losses when incursions occur into countries which are normally disease free. In addition, it has long-term effects within countries where the disease is endemic due to reduced animal productivity and the restrictions on international trade in animal products. The disease is caused by infection with foot-and-mouth disease virus (FMDV), a picornavirus. Seven different serotypes (and numerous variants) of FMDV have been identified. Some serotypes have a restricted geographical distribution, e.g. Asia-1, whereas others, notably serotype O, occur in many different regions. There is no cross-protection between serotypes and sometimes protection conferred by vaccines even of the same serotype can be limited. Thus it is important to characterize the viruses that are circulating if vaccination is being used for disease control. This review describes current methods for the detection and characterization of FMDVs. Sequence information is increasingly being used for identifying the source of outbreaks. In addition such information can be used to understand antigenic change within virus strains. The challenges and opportunities for improving the control of the disease within endemic settings, with a focus on Eurasia, are discussed, including the role of the FAO/EuFMD/OIE Progressive Control Pathway. Better control of the disease in endemic areas reduces the risk of incursions into disease-free regions.

Improving Smallholder Farmer Biosecurity in the Mekong Region Through Change Management

Transboundary animal diseases including foot-and-mouth disease and haemorrhagic septicaemia remain a major constraint for improving smallholder large ruminant productivity in the Mekong region, producing negative impacts on rural livelihoods and compromising efforts to reduce poverty and food insecurity. The traditional husbandry practices of smallholders largely exclude preventive health measures, increasing risks of disease transmission. Although significant efforts have been made to understand the social aspects of change development in agricultural production, attention to improving the adoption of biosecurity has been limited. This study reviews smallholder biosecurity risk factors identified in the peer-reviewed literature and from field research observations conducted in Cambodia and Laos during 2006-2013, considering these in the context of a change management perspective aimed at improving adoption of biosecurity measures. Motivation for change, resistance to change, knowledge management, cultural dimensions, systems theory and leadership are discussed. Due to geographical, physical and resource variability, the implementation of biosecurity interventions suitable for smallholders is not a 'one size fits all'. Smallholders should be educated in biosecurity principles and empowered to make personal decisions rather than adopt prescribed pre-defined interventions. Biosecurity interventions should be aligned with smallholder farmer motivations, preferably offering clear short-term risk management benefits that elicit interest from smallholders. Linking biosecurity and disease control with improved livestock productivity provides opportunities for sustainable improvements in livelihoods. Participatory research and extension that improves farmer knowledge and practices offers a pathway to elicit sustainable broad-scale social change. However, examples of successes need to be communicated both at the 'evidence-based level' to influence regional policy development and at the village or commune level, with 'champion farmers' and 'cross-visits' used to lead local change. The adoption of applied change management principles to improving regional biosecurity may assist current efforts to control and eradicate transboundary diseases in the Mekong region.

Laboratory capacity for diagnosis of foot-and-mouth disease in Eastern Africa: implications for the progressive control pathway

BACKGROUND

Accurate diagnosis is pertinent to any disease control programme. If Eastern Africa is to work towards control of foot-and-mouth disease (FMD) using the Progressive Control Pathway for FMD (PCP-FMD) as a tool, then the capacity of national reference laboratories (NRLs) mandated to diagnose FMD should match this task. This study assessed the laboratory capacity of 14 NRLs of the Eastern Africa Region Laboratory Network member countries using a semi-structured questionnaire and retrospective data from the World Reference Laboratory for FMD annual reports and Genbank® through National Centre for Biotechnology Information for the period 2006-2010.

RESULTS

The questionnaire response rate was 13/14 (93%). Twelve out of the 13 countries/regions had experienced at least one outbreak in the relevant five year period. Only two countries (Ethiopia and Kenya) had laboratories at biosecurity level 3 and only three (Ethiopia, Kenya and Sudan) had identified FMD virus serotypes for all reported outbreaks. Based on their own country/region assessment, 12/13 of these countries /regions were below stage 3 of the PCP-FMD. Quarantine (77%) and vaccination (54%) were the major FMD control strategies employed. The majority (12/13) of the NRLs used serological techniques to diagnose FMD, seven used antigen ELISA and three of these (25%) also used molecular techniques which were the tests most frequently requested from collaborating laboratories by the majority (69%) of the NRLs. Only 4/13 (31%) participated in proficiency testing for FMD. Four (31%) laboratories had no quality management systems (QMS) in place and where QMS existed it was still deficient, thus, none of the laboratories had achieved accreditation for FMD diagnosis.

CONCLUSIONS

This study indicates that FMD diagnostic capacity in Eastern Africa is still inadequate and largely depends on antigen and antibody ELISAs techniques undertaken by the NRLs. Hence, for the region to progress on the PCP-FMD, there is need to: implement regional control measures, improve the serological diagnostic test performance and laboratory capacity of the NRLs (including training of personnel as well as upgrading of equipment and methods, especially strengthening the molecular diagnostic capacity), and to establish a regional reference laboratory to enforce QMS and characterization of FMD virus containing samples.

Foot and mouth disease in Tanzania: an overview of its national status

The presence of foot-and-mouth disease (FMD) in Tanzania is a major obstacle to the development of the national livestock industry because of its adverse effects on livestock production and on trade of animals and animal products into lucrative export markets. FMD is endemic in Tanzania, the affected area is extensive and lack of funding makes eradication unrealistic. Uncontrolled livestock movements, the presence of large populations of wildlife in regular contacts with livestock, and the general lack of enthusiasm for FMD control among the key stakeholders, are some of the factors favouring the persistence of FMD in Tanzania. This review examines the epidemiology, dynamics and socio-economic significance of FMD in the national herd. Various control options available in Tanzanian context are also explored.

Vaccination as a means of control of foot-and-mouth disease in sub-saharan Africa

The presence of foot-and-mouth disease (FMD) in a country is a major obstacle to the development of agriculture because of its adverse effects on livestock production and agricultural exports. The eradication of FMD in sub-saharan Africa by the implementation of slaughtering-out is impractical for various reasons, but vaccination with good quality FMD vaccines can help prevent losses in stock production and reduce the overall incidence of the disease. Oil based FMD vaccines have been used with success in South American countries and have logistic and immunological advantages which would make them useful in sub-saharan African countries. The wide intratypic variation of SAT strains prevalent in sub-saharan Africa and their endemicity in African buffalo, presents a challenge to vaccine producers and requires constant epidemiological surveillance to ensure the relevance of vaccines to field conditions.