A model of lineage-1 and lineage-2 rinderpest virus transmission in pastoral areas of East Africa

EFSA Panel on Animal Health and Welfare (AHAW), Nielsen SS, Alvarez J, Bicout DJ, Calistri P, Canali E, Drewe JA, Garin‐Bastuji B, Gonzales Rojas JL, Gortázar C, Herskin M, Michel V, Miranda Chueca MÁ, Padalino B, Pasquali P, Spoolder H, Ståhl K, Velarde A, Viltrop A, Winckler C, De Clercq K, Gubbins S, Libeau G, Gervelmeyer A, Roberts HC. Assessment of the control measures of category A diseases of the Animal Health Law: Infection with rinderpest virus (Rinderpest)

EFSA received a mandate from the European Commission to assess the effectiveness of control measures against diseases included in the Category A list according to Regulation (EU) 2016/429 on transmissible animal diseases ('Animal Health Law'). This opinion belongs to a series of opinions where these control measures are assessed, with this opinion covering the assessment of control measures for rinderpest (RP), the only animal disease to have been globally eradicated. In this opinion, the AHAW Panel reviewed the effectiveness of: (i) clinical and laboratory sampling procedures, (ii) monitoring period and (iii) the minimum radius of the protection and surveillance zone, and the minimum length of time the measures should be applied in these zones. The general methodology used for this series of opinions has been published elsewhere. The transmission kernels used for the assessment of the minimum radius of the protection and surveillance zones are shown. Several scenarios for which control measures had to be assessed were agreed prior to the assessment. Considering that RP has been eradicated globally, a re-emergence that is not stopped in its early phases could have a devastating impact on animal health and the economy. The panel concludes that no suitable strategies are available to entirely mitigate the risk associated with granting derogations from killing of animals in an affected establishment or for animal movements. Therefore, the panel recommends to not grant any derogations. The monitoring period of 21 days was assessed as effective, except for the hypothetical first re-emergence of RP, when lack of awareness and diagnostic capability may extend the time to detection. It was concluded that the protection and the surveillance zones would contain 90% and > 99%, respectively, of the infections from an affected establishment. Enlarging the protection zone to 4 km would contain the disease spread with 95% probability.

Transboundary Animal Diseases, an Overview of 17 Diseases with Potential for Global Spread and Serious Consequences

Animals provide food and other critical resources to most of the global population. As such, diseases of animals can cause dire consequences, especially disease with high rates of morbidity or mortality. Transboundary animal diseases (TADs) are highly contagious or transmissible, epidemic diseases, with the potential to spread rapidly across the globe and the potential to cause substantial socioeconomic and public health consequences. Transboundary animal diseases can threaten the global food supply, reduce the availability of non-food animal products, or cause the loss of human productivity or life. Further, TADs result in socioeconomic consequences from costs of control or preventative measures, and from trade restrictions. A greater understanding of the transmission, spread, and pathogenesis of these diseases is required. Further work is also needed to improve the efficacy and cost of both diagnostics and vaccines. This review aims to give a broad overview of 17 TADs, providing researchers and veterinarians with a current, succinct resource of salient details regarding these significant diseases. For each disease, we provide a synopsis of the disease and its status, species and geographic areas affected, a summary of in vitro or in vivo research models, and when available, information regarding prevention or treatment.

Measles virus and rinderpest virus divergence dated to the sixth century BCE

Many infectious diseases are thought to have emerged in humans after the Neolithic revolution. Although it is broadly accepted that this also applies to measles, the exact date of emergence for this disease is controversial. We sequenced the genome of a 1912 measles virus and used selection-aware molecular clock modeling to determine the divergence date of measles virus and rinderpest virus. This divergence date represents the earliest possible date for the establishment of measles in human populations. Our analyses show that the measles virus potentially arose as early as the sixth century BCE, possibly coinciding with the rise of large cities.

"Can we agree on that"? Plurality, power and language in participatory research

Participatory epidemiology (PE) is a method that gathers data from groups through focus group interviews and participatory visual and scoring exercises. The method is often used in poor communities in low-income countries where it is hard to obtain conventional epidemiological data. This paper draws on research on the public sphere and democratic deliberation, along with research on language and interpretation, to suggest how PE research could be better equipped to account for diversity in local knowledge, include minority views and acknowledge power dynamics. These aspects are discussed under the three themes of 'plurality', 'power' and 'language'. A review of highly-cited PE literature suggests that PE research engages with plurality and power to a very limited extent, and only marginally more so with language and translation. Examples are taken from the authors' own PE research on African swine fever in -Uganda, classical swine fever in Germany, peste des petits ruminants (PPR) in Eastern Europe, and Ugandan pastoralists' understanding of cattle disease to provide more detail as to why conventional PE studies might fail to record issues of plurality, power and language, and also to suggest how this can be addressed. With reference to the literature on the public sphere and democratic deliberation, and on language and interpretation, this paper concludes with some suggestions as to how to take plurality, power and language into greater consideration in PE studies in future, thus improving the validity and reliability of PE data.

Strategies for the Global Eradication of Peste des Petits Ruminants: An Argument for the Use of Guerrilla Rather Than Trench Warfare

Many historical disease eradication campaigns have been characterized by large-scale mobilization and long-term campaigns of mass vaccination. As the duration of a program increases, the total cost also increases, but the effectiveness and sustainability decrease, sometimes resulting in premature loss of stakeholder support, field team fatigue, and failure or major set-backs. In contrast to this trench warfare approach, this paper proposes an eradication strategy modeled on guerrilla tactics: use exceptionally good, locally relevant and timely intelligence; strike rapidly and effectively in small areas; achieve your goals; and keep moving. For peste des petits ruminants eradication, this means a shift away from long-term mass vaccination, focusing instead on addressing some of the challenges that have plagued previous eradication programs: ineffective surveillance and movement management. Recent developments in surveillance have shown that it is now feasible to capture information about almost all cases of disease, all movements and all control activities, from the entire population in real time. Developing powerful, effective and sustainable surveillance systems is an essential prerequisite for rapid, affordable PPR eradication. PPR can be rapidly eliminated from small populations by achieving very high levels of vaccination coverage for only a short period. The key challenge is then to prevent the re-introduction of disease as immunity wanes, and to respond rapidly and effectively in the case of further local outbreaks. A comprehensive understanding of movement patterns and their drivers will allow rapid progressive eradication to be implemented. The population can be divided into manageably small units, targeted sequentially for high-coverage short-duration vaccination, then moving to the next unit based on the distribution of disease and the direction of animal flow. This approach optimizes the use of available resources, and minimizes the challenge and disruption of managing retrograde movement from infected to uninfected areas. High levels of community engagement are required to achieve the quality of surveillance, movement management and rapid response necessary for success. Traditionally, long-term vaccination has been used to first eliminate the virus from a population, and then to protect it against re-introduction of the disease. Under the guerrilla strategy, continuous real-time information, not long-term vaccination, is the main tool for disease eradication.

Modeling the transmission dynamics of foot and mouth disease in Amhara region, Ethiopia

Foot and mouth disease (FMD) is contagious, acute viral disease of all cloven-hoofed animals. The disease is endemic in Ethiopia and causes multiple outbreak every year all over the country. While it is important to understand to the transmission dynamics of FMD outbreaks for appropriate control intervention, no such study has been done in Ethiopia. Thus, the aims of this study were to estimate the basic reproduction number (R₀) of FMD and simulate FMD transmission dynamics of FMD in Amhara region of Ethiopia. Basic reproduction number (R₀) was estimated from age stratified sero-prevalence data through maximum likelihood estimation. A stochastic SIR (susceptible-infectious-recovered) compartmental FMD model was formulated and parameterized using literature and age stratified sero-prevalence field data. The R₀ of FMD in the region was estimated to be 1.27 (95%CI: 1.20-1.34). The simulation of the SIR model showed only 24% (95% CI: 16-32%) of the infection introduced in the region caused major outbreaks. Out of the major outbreaks 25% of them tend to persist in the region. Major outbreaks cause 38.9% (95% CI: 38.8-39.1%) morbidity and 0.0019% (95% CI: 0.0018-0.0020%) mortality in cattle and the outbreaks stayed for an average of 690 days (95%CI: 655-727). Validation of the model prediction with farmer's field experience indicated a fairly similar result especially for the predicted morbidity caused by outbreaks. This study revealed low transmission of FMD within the Amhara region cattle population indicating not very high vaccination coverage is needed, if control through vaccination is envisaged at regional level. However, owing to several simplified assumptions made during the modeling, this conclusion should be taken cautiously.

Decision Support for Mitigation of Livestock Disease: Rinderpest as a Case Study

A versatile, interactive model to predict geographically resolved epidemic progression after pathogen introduction into a population is presented. Deterministic simulations incorporating a compartmental disease model run rapidly, facilitating the analysis of mitigations such as vaccination and transmission reduction on epidemic spread and progression. We demonstrate the simulation model using rinderpest infection of cattle, a devastating livestock disease. Rinderpest has been extinguished in the wild, but it is still a threat due to stored virus in some laboratories. Comparison of simulations to historical outbreaks provides some validation of the model. Simulations of potential outbreaks demonstrate potential consequences of rinderpest virus release for a variety of possible disease parameters and mitigations. Our results indicate that a rinderpest outbreak could result in severe social and economic consequences.

The Opportunity To Eradicate Peste des Petits Ruminants

Peste des petits ruminants (PPR) is a highly infectious disease of sheep and goats that is caused by PPR virus, a member of the genus Morbillivirus that includes the viruses that cause rinderpest (RP) in cattle. RP was the first animal disease to be globally eradicated in 2011 and is only the second disease, after smallpox, to have ever been eradicated. PPR is one of the principal constraints to small ruminant production in Africa, Asia, and the Middle East. The epidemiology of PPR and RP as well as the technologies available for their diagnosis and control are similar. The conditions that favored the eradication of RP are also largely present for PPR. In this work, we outline the evolving strategy for eradication in light of current opportunities and challenges, as well as the lessons from other eradication programs in animal and human health. The global PPR situation and technology for its control are summarized. A strategy based on the lessons from previous eradication efforts that integrate epidemiology, social science, and economics as tools to target and motivate vaccination is summarized. Major aspects of the cost and benefit-cost analysis of the indicated program are presented. The overall undiscounted cost of eradication was estimated as $3.1 billion, and the benefit-cost ratio for the most likely scenario was estimated at 33.8. We close with a discussion of the possible next steps.

Integrative modelling for One Health: pattern, process and participation

This paper argues for an integrative modelling approach for understanding zoonoses disease dynamics, combining process, pattern and participatory models. Each type of modelling provides important insights, but all are limited. Combining these in a '3P' approach offers the opportunity for a productive conversation between modelling efforts, contributing to a 'One Health' agenda. The aim is not to come up with a composite model, but seek synergies between perspectives, encouraging cross-disciplinary interactions. We illustrate our argument with cases from Africa, and in particular from our work on Ebola virus and Lassa fever virus. Combining process-based compartmental models with macroecological data offers a spatial perspective on potential disease impacts. However, without insights from the ground, the 'black box' of transmission dynamics, so crucial to model assumptions, may not be fully understood. We show how participatory modelling and ethnographic research of Ebola and Lassa fever can reveal social roles, unsafe practices, mobility and movement and temporal changes in livelihoods. Together with longer-term dynamics of change in societies and ecologies, all can be important in explaining disease transmission, and provide important complementary insights to other modelling efforts. An integrative modelling approach therefore can offer help to improve disease control efforts and public health responses.This article is part of the themed issue 'One Health for a changing world: zoonoses, ecosystems and human well-being'.

Modelling the Dynamics of Post-Vaccination Immunity Rate in a Population of Sahelian Sheep after a Vaccination Campaign against Peste des Petits Ruminants Virus

Background

Peste des petits ruminants (PPR) is an acute infectious viral disease affecting domestic small ruminants (sheep and goats) and some wild ruminant species in Africa, the Middle East and Asia. A global PPR control strategy based on mass vaccination—in regions where PPR is endemic—was recently designed and launched by international organizations. Sahelian Africa is one of the most challenging endemic regions for PPR control. Indeed, strong seasonal and annual variations in mating, mortality and offtake rates result in a complex population dynamics which might in turn alter the population post-vaccination immunity rate (PIR), and thus be important to consider for the implementation of vaccination campaigns.

Methods

In a context of preventive vaccination in epidemiological units without PPR virus transmission, we developed a predictive, dynamic model based on a seasonal matrix population model to simulate PIR dynamics. This model was mostly calibrated with demographic and epidemiological parameters estimated from a long-term follow-up survey of small ruminant herds. We used it to simulate the PIR dynamics following a single PPR vaccination campaign in a Sahelian sheep population, and to assess the effects of (i) changes in offtake rate related to the Tabaski (a Muslim feast following the lunar calendar), and (ii) the date of implementation of the vaccination campaigns.

Results

The persistence of PIR was not influenced by the Tabaski date. Decreasing the vaccination coverage from 100 to 80% had limited effects on PIR. However, lower vaccination coverage did not provide sufficient immunity rates (PIR < 70%). As a trade-off between model predictions and other considerations like animal physiological status, and suitability for livestock farmers, we would suggest to implement vaccination campaigns in September-October. This model is a first step towards better decision support for animal health authorities. It might be adapted to other species, livestock farming systems or diseases.

The Economic Impact of Eradicating Peste des Petits Ruminants: A Benefit-Cost Analysis

Peste des petits ruminants (PPR) is an important cause of mortality and production loss among sheep and goats in the developing world. Despite control efforts in a number of countries, it has continued to spread across Africa and Asia, placing an increasing burden on the livelihoods of livestock keepers and on veterinary resources in affected countries. Given the similarities between PPR and rinderpest, and the lessons learned from the successful global eradication of rinderpest, the eradication of PPR seems appealing, both eliminating an important disease and improving the livelihoods of the poor in developing countries. We conducted a benefit-cost analysis to examine the economic returns from a proposed programme for the global eradication of PPR. Based on our knowledge and experience, we developed the eradication strategy and estimated its costs. The benefits of the programme were determined from (i) the averted mortality costs, based on an analysis of the literature, (ii) the downstream impact of reduced mortality using a social accounting matrix, and (iii) the avoided control costs based on current levels of vaccination. The results of the benefit-cost analysis suggest strong economic returns from PPR eradication. Based on a 15-year programme with total discounted costs of US$2.26 billion, we estimate discounted benefits of US$76.5 billion, yielding a net benefit of US$74.2 billion. This suggests a benefit cost ratio of 33.8, and an internal rate of return (IRR) of 199%. As PPR mortality rates are highly variable in different populations, we conducted a sensitivity analysis based on lower and higher mortality scenarios. All the scenarios examined indicate that investment in PPR eradication would be highly beneficial economically. Furthermore, removing one of the major constraints to small ruminant production would be of considerable benefit to many of the most vulnerable communities in Africa and Asia.

Potential risk of regional disease spread in West Africa through cross-border cattle trade

BACKGROUND

Transboundary animal movements facilitate the spread of pathogens across large distances. Cross-border cattle trade is of economic and cultural importance in West Africa. This study explores the potential disease risk resulting from large-scale, cross-border cattle trade between Togo, Burkina Faso, Ghana, Benin, and Nigeria for the first time.

METHODS AND PRINCIPAL FINDINGS

A questionnaire-based survey of livestock movements of 226 cattle traders was conducted in the 9 biggest cattle markets of northern Togo in February-March 2012. More than half of the traders (53.5%) operated in at least one other country. Animal flows were stochastically simulated based on reported movements and the risk of regional disease spread assessed. More than three quarters (79.2%, range: 78.1-80.0%) of cattle flowing into the market system originated from other countries. Through the cattle market system of northern Togo, non-neighbouring countries were connected via potential routes for disease spread. Even for diseases with low transmissibility and low prevalence in a given country, there was a high risk of disease introduction into other countries.

CONCLUSIONS

By stochastically simulating data collected by interviewing cattle traders in northern Togo, this study identifies potential risks for regional disease spread in West Africa through cross-border cattle trade. The findings highlight that surveillance for emerging infectious diseases as well as control activities targeting endemic diseases in West Africa are likely to be ineffective if only conducted at a national level. A regional approach to disease surveillance, prevention and control is essential.

Rinderpest: the veterinary perspective on eradication

Rinderpest was a devastating disease of livestock responsible for continent-wide famine and poverty. Centuries of veterinary advances culminated in 2011 with the UN Food and Agriculture Organization and the World Organization for Animal Health declaring global eradication of rinderpest; only the second disease to be eradicated and the greatest veterinary achievement of our time. Conventional control measures, principally mass vaccination combined with zoosanitary procedures, led to substantial declines in the incidence of rinderpest. However, during the past decades, innovative strategies were deployed for the last mile to overcome diagnostic and surveillance challenges, unanticipated variations in virus pathogenicity, circulation of disease in wildlife populations and to service remote and nomadic communities in often-unstable states. This review provides an overview of these challenges, describes how they were overcome and identifies key factors for this success.

Rinderpest eradication: appropriate technology and social innovations

Rinderpest is only the second infectious disease to have been globally eradicated. In the final stages of eradication, the virus was entrenched in pastoral areas of the Greater Horn of Africa, a region with weak governance, poor security, and little infrastructure that presented profound challenges to conventional control methods. Although the eradication process was a development activity rather than scientific research, its success owed much to several seminal research efforts in vaccine development and epidemiology and showed what scientific decision-making and management could accomplish with limited resources. The keys to success were the development of a thermostable vaccine and the application of participatory epidemiological techniques that allowed veterinary personnel to interact at a grassroots level with cattle herders to more effectively target control measures.

Participatory epidemiology: approaches, methods, experiences

Participatory epidemiology (PE) is an evolving branch of veterinary epidemiology which uses a combination of practitioner communication skills and participatory methods to improve the involvement of animal keepers in the analysis of animal disease problems, and the design, implementation and evaluation of disease control programmes and policies. This review describes the origins of PE and how the application of PE requires attention to both a participatory approach and participatory methods, supported by triangulation of data with conventional veterinary diagnostic methods. The review summarizes the various adaptations and uses of PE, including the design of primary veterinary service delivery systems, veterinary research and disease surveillance. In contrast to conventional data collection methods, an integral aspect PE is the concept of applying and evaluating new disease control programmes or surveillance systems in partnership with animal owners. In the developing regions where PE has been most commonly used, this action-orientated approach raises important challenges for veterinary institutions with limited financial resources. Information derived from PE studies can also question longstanding disease control policies and norms, nationally and internationally.

Disease properties, geography, and mitigation strategies in a simulation spread of rinderpest across the United States

For the past decade, the Food and Agriculture Organization of the United Nations has been working toward eradicating rinderpest through vaccination and intense surveillance by 2012. Because of the potential severity of a rinderpest epidemic, it is prudent to prepare for an unexpected outbreak in animal populations. There is no immunity to the disease among the livestock or wildlife in the United States (US). If rinderpest were to emerge in the US, the loss in livestock could be devastating. We predict the potential spread of rinderpest using a two-stage model for the spread of a multi-host infectious disease among agricultural animals in the US. The model incorporates large-scale interactions among US counties and the small-scale dynamics of disease spread within a county. The model epidemic was seeded in 16 locations and there was a strong dependence of the overall epidemic size on the starting location. The epidemics were classified according to overall size into small epidemics of 100 to 300 animals (failed epidemics), epidemics infecting 3,000 to 30,000 animals (medium epidemics), and the large epidemics infecting around one million beef cattle. The size of the rinderpest epidemics were directly related to the origin of the disease and whether or not the disease moved into certain key counties in high-livestock-density areas of the US. The epidemic size also depended upon response time and effectiveness of movement controls.

Immune protection in animals: the examples of rinderpest and foot-and-mouth disease

Fading immune protection in farmed animals may present a problem, particularly in free-ranging animals in nomadic and transhumant pastoral systems, where animals are not readily available for large-scale blanket vaccination programmes. Two veterinary examples of fading immune protection are discussed: rinderpest and foot-and-mouth disease (FMD). Both are devastating viral diseases of cattle that have a huge impact on the farming economy. Both diseases can be controlled by vaccination, although the post-vaccination immunity afforded by the rinderpest vaccine is markedly different from that induced by FMD vaccines. These differences may in part explain the respective advancement of international eradication campaigns: while global eradication of rinderpest is imminent, FMD viruses are still actively circulating in many parts of the world.

Impact of drought-related vaccination on livestock mortality in pastoralist areas of Ethiopia

Under a national Livestock Policy Forum in Ethiopia the impact of livestock vaccination during drought was assessed in order to inform the development of a best-practice guideline. For each of the different types of vaccine used during drought years there was no significant difference in livestock mortality, for any species, in vaccinated compared with non-vaccinated herds. The limited impact of vaccination on livestock mortality was attributed to weaknesses in the design and implementation of vaccination programmes, including use of inappropriate vaccines, low vaccination coverage, problems with vaccine dosing, incorrect timing of vaccination and problems with vaccine storage. If these weaknesses could be overcome vaccination could be a useful means to protect livestock assets, with considerable benefit-cost ratios. Vaccination should be conducted as a standard preventive measure during normal years, and programme design should be informed by participatory epidemiological studies.

The animal story

The UN Food and Agriculture Organisation's global rinderpest eradication programme (GREP)—the first and only attempt to eradicate an animal pathogen—provides several learning points from the veterinary perspective