Sero-epidemiology of Peste des petits ruminants virus infection in Turkana County, Kenya

Modelling flock heterogeneity in the transmission of peste des petits ruminants virus and its impact on the effectiveness of vaccination for eradication

Peste des petits ruminants (PPR) is an acute infectious disease of small ruminants targeted for global eradication by 2030. The Global Strategy for Control and Eradication (GSCE) recommends mass vaccination targeting 70% coverage of small ruminant populations in PPR-endemic regions. These small ruminant populations are diverse with heterogeneous mixing patterns that may influence PPR virus (PPRV) transmission dynamics. This paper evaluates the impact of heterogeneous mixing on (i) PPRV transmission and (ii) the likelihood of different vaccination strategies achieving PPRV elimination, including the GSCE recommended strategy. We develop models simulating heterogeneous transmission between hosts, including a metapopulation model of PPRV transmission between villages in lowland Ethiopia fitted to serological data. Our results demonstrate that although heterogeneous mixing of small ruminant populations increases the instability of PPRV transmission-increasing the chance of fadeout in the absence of intervention-a vaccination coverage of 70% may be insufficient to achieve elimination if high-risk populations are not targeted. Transmission may persist despite very high vaccination coverage (>90% small ruminants) if vaccination is biased towards more accessible but lower-risk populations such as sedentary small ruminant flocks. These results highlight the importance of characterizing small ruminant mobility patterns and identifying high-risk populations for vaccination and support a move towards targeted, risk-based vaccination programmes in the next phase of the PPRV eradication programme. Our modelling approach also illustrates a general framework for incorporating heterogeneous mixing patterns into models of directly transmitted infectious diseases where detailed contact data are limited. This study improves understanding of PPRV transmission and elimination in heterogeneous small ruminant populations and should be used to inform and optimize the design of PPRV vaccination programmes.

Prokaryotic expression of the V protein of the peste des petits ruminants virus and development of an indirect ELISA

In this study, we recombinantly expressed the V protein of the peste des petits ruminants virus (PPRV) and evaluated its diagnostic value for PPRV infection using an indirect ELISA (i-ELISA). The optimal concentration of the coated antigen of V protein was 15 ng/well at a serum dilution of 1:400, and the optimal positive threshold value was 0.233. A cross-reactivity assay showed that the V protein-based i-ELISA was specific to PPRV with consistent reproducibility and showed a specificity of 82.6% and a sensitivity of 100% with a virus neutralization test. Using the recombinant V protein as an antigen in ELISA is useful for seroepidemiological studies of PPRV infections.

Seroprevalence and risk factors of Peste des petits ruminants in different production systems in Uganda

Peste des petits ruminants (PPR) is a highly contagious and fatal disease of mostly domestic goats and sheep. First reported in Uganda in 2007, the extent of peste des petits ruminants virus (PPRV) exposure, geographical distribution and risk factors of its transmission and spread are not clearly understood. In this study, we used cluster random sampling methodology to select study villages from three districts representing three different production systems along Uganda's "cattle corridor". Between October and December 2022, 2520 goat and sheep serum samples were collected from 252 households with no history of PPR vaccination in the past one year. The household heads were interviewed to assess possible risk factors of PPRV transmission using a structured questionnaire. The serum samples were screened with a commercial competitive enzyme-linked immunosorbent assay (cELISA) for PPRV antibodies. The determined overall true seroprevalence of PPRV was 27.3% [95% CI: 25.4-29.1]. The seroprevalence of PPRV antibodies in different production systems was 44.1% [95% CI: 40.6-47.7], 31.7% [95% CI: 28.4-35.0] and 6.1% [95% CI: 4.4-7.9] for pastoral, agropastoral and mixed crop-livestock production systems respectively. A mixed-effects multivariable logistic regression model revealed strong statistical evidence of association between female animals and PPRV antibody seropositivity compared to males [OR= 2.45, 95% CI: 1.7-3.5, p < 0.001]. The likelihood of being PPRV antibody seropositive significantly increased with increasing small ruminant age. Animals older than 3 years were more than three times as likely to be PPRV seropositive compared to animals aged under 1 year [OR= 3.41, 95% CI: 2.39-4.85, p < 0.001]. There was no statistical evidence of association between small ruminant species and PPRV antibody seropositivity (p = 0.423). Village flocks that interacted with neighboring flocks daily during grazing (IRR = 1.59, 95% CI: 1.19-2.13) and watering around swamps (IRR = 1.59, 95% CI: 1.19-2.13) were highly correlated with increased number of PPRV seropositive animals as compared to flocks that were more restricted in grazing and watered around other water sources other than swamps. Flocks from pastoral and agropastoral production systems were more than 10 times more likely to have seropositive animals than mixed crop-livestock flocks. Targeting PPR control interventions (vaccination and livestock movement control) to pastoral and agro-pastoral small ruminant production systems that are very prone to PPR incursions is recommended to prevent PPRV spread to low-risk smallholder mixed crop-livestock production systems.

Modeling for Smart Vaccination against Peste des Petits Ruminants (PPR) in the Emirate of Abu Dhabi, United Arab Emirates

Peste des petits ruminants (PPR) is a contagious and economically important transboundary viral disease of small ruminants. The United Arab Emirates (UAE) national animal health plan aimed to control and eradicate PPR from the country by following the global PPR control and eradication strategy which adopts small ruminants' mass vaccination to eradicate the disease from the globe by 2030. A smart vaccination approach, which is less expensive and has longer-term sustainable benefits, is needed to accelerate the eradication of PPR. In this study, a mathematical algorithm was developed based on animals' identification and registration data, belonging to the Abu Dhabi Agriculture and Food Safety Authority (ADAFSA), and other different parameters related to PPR risk occurrence. The latter included animal holding vaccination history, the number of animals per holding, forecasting of the number of animals and newborns per holding, the proximity of an animal holding to a PPR outbreak and the historical animal holding owner vaccination rejection attitude. The developed algorithm successfully prioritized animal holdings at risk of PPR infection within Abu Dhabi Emirate to be targeted by vaccination. This in turn facilitated the mobilization of field vaccination teams to target specific sheep and goat holdings to ensure the generation of immunity against the disease on a risk-based approach. The vaccination coverage of the targeted livestock population was increased to 86% and the vaccination rejection attitude was reduced by 35%. The duration of the vaccination campaign was reduced to 30 compared to 70 working days and hence can alleviate the depletion of human and logistic resources commonly used in classical mass vaccination campaigns. The results obtained from implementing the algorithm-based PPR vaccination campaign will reduce the negative impact of PPR on the UAE livestock sector and accelerate the achievement of the national PPR eradication plan requirements.

Seroprevalence of Peste des Petits Ruminants and Contagious Caprine Pleuropneumonia Coinfections in Goats in Kwale County, Kenya

Goats are among the most important small ruminants affected by Peste des Petits ruminants (PPR) and contagious caprine pleuropneumonia (CCPP) diseases, two of the most significant constraints worldwide to the production of small ruminant species. Herein, the competitive enzyme-linked immunosorbent assay (cELISA) and the latex agglutination test (LAT) were used to determine the coinfections of PPR and CCPP in goats in Kwale County on Kenya's South Coast. A total of 368 serum samples were collected from goats of various ages and sexes exhibiting respiratory distress in the four subcounties of Kwale County (Kinango, Lunga Lunga, Matuga, and Msambweni) and screened for PPR and CCPP antibodies. Of the 368 goats sampled, 259 (70.4%) were females and 109 (29.6%) were males, and 126 (34.2%), 71 (19.3%), 108 (29.3%), and 63 (17.1%) samples were collected from Kinango, Matuga, Lunga Lunga, and Msambweni, respectively. The overall PPR seropositivity rate was 48.6% (179/368); rates in Kinango, Lunga Lunga, Matuga, and Msambweni were 70.6%, 29.6%, 49.3%, and 36.5%, respectively. The overall CCPP seropositivity rate was 45.4% (167/368), while rates in Kinango, Lunga Lunga, Matuga, and Msambweni were 51.6%, 49.1%, 36.6%, and 36.5%, respectively. Notably, the seropositivity of PPR was higher in male (53.3%) than in female (46.72%) goats, though not statistically significant. In addition, the CCPP seropositivity rates were not significantly different between male (44.0%) and female (45.9%) goats. Regarding age, the PPR seropositivity rates were 45.9%, 55.8%, and 52.3% in adults, kids, and weaners, respectively. For CCPP, the seropositivity rates were 48.3%, 40.4%, and 42.3% in adults, kids, and weaners, respectively. The coinfection rate of PPR and CCPP was 22.3% (82/368). Despite the high coinfection, univariate analysis revealed no relationship between PPR and CCPP infections. However, given the high PPR and CCPP infection rates, as a result of separate or coinfection, there is a need to upscale or intensify vaccination in the county.

Prevalence, Risk Factors for Exposure, and Socio-Economic Impact of Peste Des Petits Ruminants in Karenga District, Karamoja Region, Uganda

Peste des petits ruminants (PPR), a disease caused by small ruminant morbillivirus (SRM), is highly contagious with high morbidity and mortality. Controlling PPR requires a proper understanding of the epidemiological dynamics and impact of the disease in a range of geographical areas and management systems. Karenga district, located in the pastoral region of Karamoja in northeastern Uganda, and in the vicinity of Kidepo Valley National Park, is characterised by free cross-border (South Sudan and Kenya) livestock trade, communal grazing, and transhumance. This study was conducted from November through December 2020 to determine the seroprevalence of anti-SRM antibodies, the risk factors associated with the occurrence, and the socio-economic impact of PPR in Karenga. A total of 22 kraals were randomly selected from all administrative units, and 684 small ruminants (sheep = 115, goats = 569) were selected for serum collection using systematic random sampling. Exposure to SRM was determined using a competitive enzyme-linked immunosorbent assay. The overall true seroprevalence of SRM antibodies was high, 51.4 (95% confidence interval [CI] 45–52.6). Multivariate logistic regression for risk factors showed that seroprevalence varied significantly by location (26.8% to 87.8%, odds ratio (OR) ≤ 14.5). The odds of exposure to SRM were higher in sheep (73.9%) than in goats (43.8%) (OR = 1.7, p = 0.08), and seropositivity was higher in animals greater than two years old (65.5%; OR = 11.1, p < 0.001), or those one to two years old (24.7%; OR = 1.6, p = 0.2), compared to small ruminants less than one year old (16.1%). Using participatory epidemiology approaches (semi-structured interviews, clinical examinations, pairwise ranking, proportional piling, impact matrix scoring) with 15 key informants and 22 focus groups of pastoralists, PPR was the second most important small ruminant disease: relative morbidity 14%, relative mortality 9%, and case fatality rate 78%, and impacted productivity mainly in terms of treatment costs, mortality, marketability, and conflicts. These findings provide evidence to support the implementation of disease surveillance and control strategies to mitigate the impact of PPR in Karamoja and other pastoral areas in eastern Africa.

Impact of Peste des petits ruminants for sub-Saharan African farmers: A bioeconomic household production model

Peste des petits ruminants (PPR), a contagious viral disease affecting small ruminants, has been targeted by the global community for eradication within the next 10 years. However, eradication will require substantial money, human resources, coordination among actors, and individual commitments. The objective was to estimate the cost of PPR at a household level, thereby providing information on the potential economic benefits of PPR eradication and the incentives for small ruminant keepers to actively participate in the PPR Global Eradication Programme. This study focused on four sub-Saharan countries: Ethiopia, Malawi, Mali and Rwanda. Publicly available household level data assembled by FAO were used. A bioeconomic model was built to estimate impacts of PPR for a standardized theoretical area, where each household raised an average small ruminant herd or flock. Model outputs were used to estimate, at a household level, income loss due to a PPR outbreak. We constructed various income scenarios to account for the variability of small ruminant income as a proportion of total household annual income. Household income losses ranged from 2% to 40% of total annual income; percentages varied depending on the income scenario and on the gross annual economic impact of PPR on small ruminant production, which ranged from 20% to 80%, based on results of the bioeconomic model. As expected, the more small ruminant production contributed to household income the greater the impact. Estimates provided herein warn decision makers that, given the heterogeneous impact of PPR on household income, the willingness of small ruminant decision makers to participate in the PPR Global Eradication Programme may vary widely and tailored approaches should be devised and implemented.

Peste des Petits Ruminants Virus Infection at the Wildlife-Livestock Interface in the Greater Serengeti Ecosystem, 2015-2019

Peste des petits ruminants (PPR) is a viral disease of goats and sheep that occurs in Africa, the Middle East and Asia with a severe impact on livelihoods and livestock trade. Many wild artiodactyls are susceptible to PPR virus (PPRV) infection, and some outbreaks have threatened endangered wild populations. The role of wild species in PPRV epidemiology is unclear, which is a knowledge gap for the Global Strategy for the Control and Eradication of PPR. These studies aimed to investigate PPRV infection in wild artiodactyls in the Greater Serengeti and Amboseli ecosystems of Kenya and Tanzania. Out of 132 animals purposively sampled in 2015–2016, 19.7% were PPRV seropositive by ID Screen PPR competition enzyme-linked immunosorbent assay (cELISA; IDvet, France) from the following species: African buffalo, wildebeest, topi, kongoni, Grant’s gazelle, impala, Thomson’s gazelle, warthog and gerenuk, while waterbuck and lesser kudu were seronegative. In 2018–2019, a cross-sectional survey of randomly selected African buffalo and Grant’s gazelle herds was conducted. The weighted estimate of PPRV seroprevalence was 12.0% out of 191 African buffalo and 1.1% out of 139 Grant’s gazelles. All ocular and nasal swabs and faeces were negative by PPRV real-time reverse transcription-polymerase chain reaction (RT-qPCR). Investigations of a PPR-like disease in sheep and goats confirmed PPRV circulation in the area by rapid detection test and/or RT-qPCR. These results demonstrated serological evidence of PPRV infection in wild artiodactyl species at the wildlife–livestock interface in this ecosystem where PPRV is endemic in domestic small ruminants. Exposure to PPRV could be via spillover from infected small ruminants or from transmission between wild animals, while the relatively low seroprevalence suggests that sustained transmission is unlikely. Further studies of other major wild artiodactyls in this ecosystem are required, such as impala, Thomson’s gazelle and wildebeest.

Prioritizing smallholder animal health needs in East Africa, West Africa, and South Asia using three approaches: Literature review, expert workshops, and practitioner surveys

Managing the health needs of livestock contributes to reducing poverty and improving the livelihoods of smallholder and pastoralist livestock keepers globally. Animal health practitioners, producers, policymakers, and researchers all must prioritize how to mobilize limited resources. This study employed three approaches to prioritize animal health needs in East and West Africa and South Asia to identify diseases and syndromes that impact livestock keepers. The approaches were a) systematic literature review, b) a series of expert workshops, and c) a practitioner survey of veterinarians and para-veterinary professionals. The top constraints that emerged from all three approaches include endo/ ectoparasites, foot and mouth disease, brucellosis, peste des petits ruminants, Newcastle disease, and avian influenza. Expert workshops additionally identified contagious caprine pleuropneumonia, contagious bovine pleuropneumonia, mastitis, and reproductive disorders as constraints not emphasized in the literature review. Practitioner survey results additionally identified nutrition as a constraint for smallholder dairy and pastoralist small ruminant production. Experts attending the workshops agreed most constraints can be managed using existing veterinary technologies and best husbandry practices, which supports a shift away from focusing on individual diseases and new technologies towards addressing systemic challenges that limit access to veterinary services and inputs. Few research studies focused on incidence/ prevalence of disease and impact, suggesting better incorporation of socio-economic impact measures in future research would better represent the interests of livestock keepers.

Peste des petits ruminants (PPR) in Africa and Asia: A systematic review and meta-analysis of the prevalence in sheep and goats between 1969 and 2018

BACKGROUND

Peste des petits ruminants (PPR) is a prevalent viral disease of sheep and goats that impacts productivity and international animal trade. Despite the substantial economic consequences related to PPR, little is known about the prevalence of this disease at the broad geographical levels.

OBJECTIVE

The present study aimed to use a systematic approach to assess the regional prevalence of PPR in sheep and goats, and the associated factors that contribute to prevalence estimates.

METHODS

Published articles on PPR in sheep and goats were searched in PubMed, Web of Science, Scopus, Google Scholar and the reference lists of articles reporting the prevalence from 1 January 1969 to 31 December 2018. Articles were selected using inclusion and exclusion criteria. Since the heterogeneity among the studies was significant, pooled prevalences were estimated by a random effect meta-analysis model.

RESULTS

Data on the prevalence of PPR were obtained from Africa and Asia, where the pooled prevalence estimates were 40.99% (95% CI: 37.20%-44.79%) and 38.43% (95% CI: 35.64%-41.22%) respectively. Overall, the estimated pooled prevalence at Africa-Asia level in sheep was 39.31% (95% CI: 35.75%-42.88%) and in goats was 39.57% (95% CI: 36.66%-42.48%). Significant heterogeneity (I²  > 80%) was noted in most pooled estimates.

CONCLUSION

The results on the regional prevalence estimates of PPR presented here will be useful in raising awareness and advocating for Governments to engage in initiatives to eradicate PPR and prevent it from spreading to other continents.

Sentinel surveillance of selected veterinary and public health pathogens in camel population originating from Southern Punjab province, Pakistan

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Camels are susceptible to a wide range of infectious diseases with varying rate of morbidity and mortality.

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Blutongue, peste des petits ruminants and brucellosis are prevalent among camels in southern part of the Punjab provinvce, Pakistan.

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Genome corresponding to Brucella abortus and multiple serotypes of bluetongue were detected among camels.

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Camels should be included for disease control interventions reltaed to brucellosis, blutongue and PPR from their endemic setting worldwide.

An extended range of host susceptibility including camel has been evidenced for some of the important veterinary and public health pathogens, such as brucellosis, peste des petits ruminants (PPR) and bluetongue (BT). However, in disease endemic settings across many parts of the globe, most of the disease control interventions accounts for small and large ruminants, whereas unusual hosts and/or natural reservoirs, such as camels, remain neglected for disease control measures including routine vaccination. Such a policy drawback not only plays an important role in disease epizootiology particularly in settings where disease is endemic, but also serves an obstacle in disease control and subsequent eradication in future. With this background, using pre-validated ELISA and molecular assays [multiplex PCR, reverse transcriptase (RT)-PCR and real-time (rt)-PCR], we conducted a large-scale pathogen- and antibody-based surveillance for brucellosis, peste des petits ruminants and bluetongue in camel population (n = 992) originating from a wide geographical region in southern part of the Punjab province, Pakistan. Varying in each of the selected districts, the seroprevalence was found to be maximum for bluetongue [n = 697 (70.26%, 95% CI: 67.29–73.07)], followed by PPR [n = 193 (19.46%, 95% CI: 17.07–22.09)] and brucellosis [n = 66 (6.65%, 95% CI: 5.22–8.43)]. Odds of seroprevalence were more significantly associated with pregnancy status (non-pregnant, OR = 2.23, 95% CI: 1.86–5.63, p<0.01), farming system (mixed-animal, OR = 2.59, 95% CI: 1.56–4.29, p<0.01), breed (Desi, OR = 1.97, 95% CI: 1.28–4.03, p<0.01) and farmer education (illiterate, OR = 3.17, 95% CI: 1.45–6.93, p<0.01) for BTV, body condition (normal, OR = 3.54, 95% CI: 1.92–6.54, p<0.01) and breed (Desi, OR = 2.19, 95% CI: 1.09–4.40, p<0.01) for brucellosis, and feeding system for PPR (grazing, OR = 2.75, 95% CI: 1.79–4.22, p<0.01). Among the total herds included (n = 74), genome corresponding to BT virus (BTV) and brucellosis was detected in 14 (18.92%, 95 CI: 11.09–30.04) and 19 herds (25.68%, 95% CI: 16.54–37.38), respectively. None of the herds was detected with genome of PPR virus (PPRV). Among the positive herds, serotype 1, 8 and 11 were detected for BTV while all the herds were exclusively positive to B. abortus. Taken together, the study highlights the role of potential disease reservoirs in the persistence and transmission of selected diseases in their susceptible hosts and, therefore, urges necessary interventions (e.g., inclusion of camels for vaccine etc.) for the control of diseases from their endemic setting worldwide.

Peste des Petits Ruminants at the Wildlife-Livestock Interface in the Northern Albertine Rift and Nile Basin, East Africa

In the recent past, peste des petits ruminants (PPR) emerged in East Africa causing outbreaks in small livestock across different countries, with evidences of spillover to wildlife. In order to understand better PPR at the wildlife-livestock interface, we investigated patterns of peste des petits ruminants virus (PPRV) exposure, disease outbreaks, and viral sequences in the northern Albertine Rift. PPRV antibodies indicated a widespread exposure in apparently healthy wildlife from South Sudan (2013) and Uganda (2015, 2017). African buffaloes and Uganda kobs <1-year-old from Queen Elizabeth National Park (2015) had antibodies against PPRV N-antigen and local serosurvey captured a subsequent spread of PPRV in livestock. Outbreaks with PPR-like syndrome in sheep and goats were recorded around the Greater Virunga Landscape in Kasese (2016), Kisoro and Kabale (2017) from western Uganda, and in North Kivu (2017) from eastern Democratic Republic of the Congo (DRC). This landscape would not be considered typical for PPR persistence as it is a mixed forest-savannah ecosystem with mostly sedentary livestock. PPRV sequences from DRC (2017) were identical to strains from Burundi (2018) and confirmed a transboundary spread of PPRV. Our results indicate an epidemiological linkage between epizootic cycles in livestock and exposure in wildlife, denoting the importance of PPR surveillance on wild artiodactyls for both conservation and eradication programs.

Expanding Diversity of Susceptible Hosts in Peste Des Petits Ruminants Virus Infection and Its Potential Mechanism Beyond

Peste des petits ruminants (PPR) is a severe respiratory and digestive tract disease of domestic small ruminants caused by PPR virus (PPRV) of the genus Morbillivirus. Although the primary hosts of PPRV are goats and sheep, the host range of PPRV has been continuously expanding and reported to infect various animal hosts over the last decades, which could bring a potential challenge to effectively control and eradicate PPR globally. In this review, we focused on current knowledge about host expansion and interspecies infection of PPRV and discussed the potential mechanisms involved.

Spatial Multicriteria Evaluation for Mapping the Risk of Occurrence of Peste des Petits Ruminants in Eastern Africa and the Union of the Comoros

Peste des petits ruminants virus (PPRV), responsible for peste des petits ruminants (PPR), is widely circulating in Africa and Asia. The disease is a huge burden for the economy and development of the affected countries. In Eastern Africa, the disease is considered endemic. Because of the geographic proximity and existing trade between eastern African countries and the Comoros archipelago, the latter is at risk of introduction and spread, and the first PPR outbreaks occurred in the Union of the Comoros in 2012. The objective of this study was to map the areas suitable for PPR occurrence and spread in the Union of the Comoros and four eastern African countries, namely Ethiopia, Uganda, Kenya, and Tanzania. A Geographic Information System (GIS)-based Multicriteria Evaluation (MCE) was developed. Risk factors for PPR occurrence and spread, and their relative importance, were identified using literature review and expert-based knowledge. Corresponding geographic data were collected, standardized, and combined based on a weighted linear combination to obtain PPR suitability maps. The accuracy of the maps was assessed using outbreak data from the EMPRES database and a ROC curve analysis. Our model showed an excellent ability to distinguish between absence and presence of outbreaks in Eastern Africa (AUC = 0.907; 95% CI [0.820-0.994]), and a very good performance in the Union of the Comoros (AUC = 0.889, 95% CI: [0.694-1]). These results highlight the efficiency of the GIS-MCE method, which can be applied at different geographic scales: continental, national and local. The resulting maps provide decision support tools for implementation of disease surveillance and control measures, thus contributing to the PPR eradication goal of OIE and FAO by 2030.

Seroprevalence, geographical distribution, and risk factors of peste des petits ruminants in the Republic of Chad

Objective:

The objective of this study was to determine the prevalence, geographical distribution, and main risk factors for peste des petits ruminants (PPR) in the Republic of Chad.

Materials and methods:

A total of 3,546 sera collected from unvaccinated small ruminants including 1,699 goats and 1,847 sheep in 19 of the 23 regions in Chad were randomly sampled. The competitive enzyme-linked immunosorbent assay technics were used for serological analysis.

Results:

The overall seroprevalence at the individual level was 52.9%±1.6% (48.9% for goats and 56.2% for sheep). Seroprevalence observed in the Chari Baguirmi, Ouaddaï, and N’Djamena regions was significantly higher than those in the other regions. Transhumant herds are the most exposed than the sedentary ones. Older animals were more affected than the young ones. Kababich sheep are the most affected than other breeds.

Conclusion:

This study has shown that the PPR virus is circulating in the Republic of Chad. In view of the results obtained, the disease is enzootic in the country. Epidemiological information obtained including seroprevalence rate, risk factors (sex, breed, age, and mode of rearing), and geographical distribution will help to define an appropriate strategy for PPR control in the Republic of Chad.

A dynamic model of transmission and elimination of peste des petits ruminants in Ethiopia

Peste des petits ruminants (PPR), a devastating viral disease of sheep and goats, has been targeted by the global community for eradication within the next 15 years. Although an efficacious attenuated live vaccine is available, the lack of knowledge about the transmission potential of PPR virus (PPRV) may compromise eradication efforts. By fitting a metapopulation model simulating PPRV spread to the results of a nationwide serological survey in Ethiopia, we estimated the level of viral transmission in an endemic setting and the vaccination coverage required for elimination. Results suggest that the pastoral production system as a whole acts as a viral reservoir, from which PPRV spills over into the sedentary production system, where viral persistence is uncertain. Estimated levels of PPRV transmission indicate that viral spread could be prevented if the proportion of immune small ruminants is kept permanently above 37% in at least 71% of pastoral village populations. However, due to the high turnover of these populations, maintaining the fraction of immune animals above this threshold would require high vaccine coverage within villages, and vaccination campaigns to be conducted annually. Adapting vaccination strategies to the specific characteristics of the local epidemiological context and small ruminant population dynamics would result in optimized allocation of limited resources and increase the likelihood of PPR eradication.

Analysis of pastoralists' perception on challenges and opportunities for sheep and goat production in Northern Kenya

Small ruminants' production contributes to livelihood of pastoral communities, but this faces myriad constraints. This study aimed at identifying challenges facing producers of small ruminants, prioritizing diseases and their control measures and documenting opportunities for improvement. Sixteen focus group discussions with livestock owners and 13 key informant interviews were done in selected areas in Mandera County, Northern Kenya, and both quantitative and qualitative data collected using a questionnaire guide. Occurrences of diseases (27.4%) and drought (25%) were consistently ranked high in all groups. Other production challenges included increased predation of livestock, inadequate delivery of veterinary services, and increased livestock mortalities. Peste des Petit ruminants was ranked high with a median rank of 21.5%, while contagious caprine pleuropneumonia and sheep and goat pox were ranked second and third, respectively. Other diseases included tick-borne diseases, helminthosis, and pneumonia. Vaccination was ranked as the most effective control strategy for infectious diseases. Other control measures included recitation of Quran and cauterization. However, several opportunities exist for support of small ruminants' production: increased budgetary allocation for disease control by government, initiation of projects that enhance livestock production in the region by government and its development partners. These findings are useful for policy makers for disease control and organizations that are working on projects that focuses on enhancement of pastoralists' resilience, while future research could also identify appropriate technologies that reduces these impacts.

Cross-sectional sero-prevalence study of Peste des Petits Ruminants (PPR) in goats of Syangja and Kaski districts of Nepal

A cross-sectional study was conducted to determine sero-prevalence of Peste des Petits Ruminants (PPR) among goat population of outbreak suspected areas; Kaski and Syangja districts of Nepal. A total of 460 goat serum samples were tested by using c-ELISA for the presence of antibodies against PPR. Out of the 460 samples tested, 380 samples were found positive, giving overall sero-positivity of 82.60%. Significantly higher sero-prevalence was found (*P < 0.05) in females (87.50%) compared to males (70.45%) and crossbreed goats were found highly susceptible than the pure breed goats (*P < 0.05). Likewise, higher sero-prevalence of PPR was observed in adults and cross breed goats compared to their counterparts and significantly higher sero-prevalence was observed in Syangja district compared to Kaski. Thus, adults, females and cross-breeds populations of goats are at higher risk of PPR whereas geographically, goat population of Syangja district were found significantly prone to PPR. Appropriate control measures, such as ring vaccination can be followed to prevent the potential outbreak situation.

Seroprevalence and risk factors for peste des petits ruminants and selected differential diagnosis in sheep and goats in Tanzania

Introduction: Livestock husbandry is critical for food security and poverty reduction in a low-income country like Tanzania. Infectious disease is one of the major constraints reducing the productivity in this sector. Peste des petits ruminants (PPR) is one of the most important diseases affecting small ruminants, but other infectious diseases may also be present.

Objective: The objective of this study was to determine the seroprevalence and risk factors for exposure to PPR, contagious caprine pleuropneumonia (CCPP), foot-and-mouth disease (FMD), bluetongue (BT), and bovine viral diarrhoea (BVD) in sheep and goats in Tanzania.

Methods: Serum samples were collected in 2014 and 2015, and analysed using enzyme-linked immunosorbent assays to detect antibodies to the five pathogens.

Results and discussion: This is the first description of seroprevalence of FMD and BT among small ruminants in Tanzania. Risk factor analysis identified sex (female) (OR for 2014: PPR: 2.49, CCPP: 3.11, FMD: 2.98, BT: 12.4, OR for 2015: PPR: 14.1, CCPP: 1.10, FMD: 2.67, BT: 1.90, BVD: 4.73) and increasing age (>2 years) (OR for 2014: PPR: 14.9, CCPP: 2.34, FMD: 7.52, BT: 126, OR for 2015: PPR: 8.13, CCPP: 1.11, FMD: 2.98, BT: 7.83, BVD: 4.74) as risk factors for exposure to these diseases.

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.