Peste des petits ruminants (PPR) in Ethiopia: analysis of a national serological survey

An Integrated Ecological Niche Modelling Framework for Risk Mapping of Peste des Petits Ruminants Virus Exposure in African Buffalo (Syncerus caffer) in the Greater Serengeti-Mara Ecosystem

Peste des petits ruminants (PPR) is a highly contagious viral disease of small ruminants that threatens livelihoods and food security in developing countries and, in some cases, wild ungulate species conservation. The Greater Serengeti-Mara Ecosystem (GSME) encompasses one of the major wildlife populations of PPR virus (PPRV)-susceptible species left on earth, although no clinical disease has been reported so far. This study aimed to gain further knowledge about PPRV circulation in the GSME by identifying which factors predict PPRV seropositivity in African buffalo (Syncerus caffer). Following an ecological niche modeling framework to map host-pathogen distribution, two models of PPRV exposure and buffalo habitat suitability were performed using serological data and buffalo censuses. Western Maasai Mara National Reserve and Western Serengeti National Park were identified as high-risk areas for PPRV exposure in buffalo. Variables related to wildlife-livestock interaction contributed to the higher risk of PPRV seropositivity in buffalo, providing supportive evidence that buffalo acquire the virus through contact with infected livestock. These findings can guide the design of cost-effective PPRV surveillance using buffalo as a sentinel species at the identified high-risk locations. As more intensive studies have been carried out in Eastern GSME, this study highlights the need for investigating PPRV dynamics in Western GSME.

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.

Sero-Prevalence and Associated Risk Factors of Peste Des Petits Ruminants in Dera and Gerar Jarso Districts of Oromia Region, Ethiopia

Introduction

Peste des petits ruminants is a transboundary disease of major economic importance and imposes significant constraints on small ruminant production.

Methods

A cross-sectional study was employed in Dera and Gerar Jarso districts of the North Shewa zone, Oromia Region from February 2021 to March 2022, to estimate the antibody of PPRV and assess the associated risk factors. Blood samples (n = 662) were collected from sheep and goats. Cluster sampling strategy was employed to collect the data. Villages/Kebeles and individual small ruminants were randomly selected, while households were designated using a systematic random sampling method.

Results

An overall individual animal and flock level sero-prevalence was 10.3% (95% CI = 8.2-12.8) and 100% (95% CI = 96.3-100), respectively, from the c-ELISA test result. A sero-prevalence of 11.2% (95% CI = 8.7-14.4) in Dera and 8% (95% CI = 5-12.7) in Gerar Jarso districts was recorded.

Discussion

Flock size, age, sex, communal grazing, and watering system, new small ruminant introduction into a flock, and mixed rearing were significantly associated with PPR sero-positivity in sheep and goats. The chance of PPR occurrence in goats was 4 times (OR = 4; P = 0.000) more than sheep. Female sheep and goats were more likely to be sero-positive to PPR by 3 times (OR = 3.2; P = 0.003) than males. The newly introduced small ruminants had 4 times more odds (OR = 4.4; P = 0.000) of sero-positivity than animals being born at home. Small ruminants kept under communal grazing and watering system were nearly 12 times (OR = 11.5; P = 0.024) more likely sero-positive than privately managed small ruminants. Likewise, sheep and goats reared together were almost 9 times (OR = 9.4; P = 0.000) a higher chance of being sero-positive compared with separately reared small ruminants.

Conclusion

The finding of PPR virus antibodies in small ruminants from all study areas indicates endemic circulation of the virus. The implementation of regular vaccination could minimize the occurrence of PPR.

Urbanization and Habitat Characteristics Associated with the Occurrence of Peste des Petits Ruminants in Africa

As a highly contagious viral disease, peste des petits ruminants (PPR) can cause severe socio-economic impacts in developing countries due to its threat to sheep and goat production. Previous studies have identified several risk factors for PPR at the individual or herd level. However, only a few studies explored the impacts of landscape factors on PPR risk, particularly at a regional scale. Moreover, risk factor analyses in Africa usually focused on sub-Saharan Africa while neglecting northern Africa. Based on regional occurrence data during 2006–2018, we here explored and compared the risk factors, with a focus on factors related to ruminant habitats, for the occurrence of PPR in sub-Saharan and northern Africa. Our results demonstrated different risk factors in the two regions. Specifically, habitat fragmentation was negatively correlated with PPR occurrence in sub-Saharan Africa, while positively correlated with PPR occurrence in northern Africa. Moreover, urbanization showed a positive association with PPR occurrence in sub-Saharan Africa. Our study is among the first, to our knowledge, to compare the risk factors for PPR in sub-Saharan and northern Africa and contributes to a better understanding of the effects of habitat characteristics on PPR occurrence at a regional scale.

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.

Seroepidemiology of Peste des Petits ruminants in sheep and goats in the selected district of Horu Guduru Zone, Western Ethiopia

Peste des Petits Ruminants (PPR) is an acute, highly contagious, economically important transboundary viral disease of small ruminants. The objectives of this cross-sectional study were to estimate the seroprevalence and associated risk factors of PPR in small ruminants in selected districts of Horo Guduru Zone, Western Ethiopia. A total of 806 blood samples, corresponding to 124 flocks comprised of 387 sheep and 419 goats, were collected using multi-stage sampling. The sera were tested using competitive Enzyme-Linked Immunosorbent Assay (c-ELISA). A pre-tested questionnaire was used to collect data on potential risk factors for PPRV infection. Pearson's Chi-Square and logistic regression analyses were used to see the association of the seroprevalence with potential risk factors. The flock-level overall seroprevalence of PPR was 27.42% (95% confidence interval [CI]: 19.79-36.15%). An overall animal level seroprevalence of 5.71% (95% CI: 4.21-7.54%) was recorded with 6.98% (95% CI: 4.65-10.00%) seroprevalence in sheep and 4.53% (95% CI: 2.75-6.99%) in goats. There was a significant association between the seroprevalence and risk factors that were sharing common grazing land (P = 0.032), the introduction of newly purchased animals into the flock (P = 0.011), and uncontrolled animal movements in goats (P = 0.018). Sharing common grazing land with other flocks in goats (P = 0.026) and midland altitude in sheep (P = 0.029) were the other predictors of PPR. The seropositivity in unvaccinated small ruminants suggests the circulation of the virus. Therefore, awareness creation, vaccination, strengthening the disease surveillance system and large-scale epidemiological and molecular studies are suggested.

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.

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.

Post-vaccination herd immunity against peste des petits ruminants and inter-vaccination population turnover in small ruminant flocks in northwest Ethiopia

Vaccination is the main tool for control of peste des petits ruminants (PPR) because of the availability of effective and safe vaccines that provide long lasting protection. However vaccination campaigns may not always provide sufficient herd immunity needed to prevent disease outbreaks because of logistic problems with vaccination such as inappropriate cold chain and vaccine delivery methods, and the rapid population turnover of small ruminants. This study was carried out to assess post-vaccination herd immunity against PPR and inter-vaccination population turnover in small ruminant flocks in Metema district, northwest Ethiopia where frequent PPR outbreaks occur despite regular vaccination. A total of 412 serum samples were collected from selected small ruminants in 72 flocks (average flock size of 33.4 and standard deviation of 30) above three months of age in three kebeles immediately before a vaccination program. One month after the vaccination using freeze dried live attenuated vaccine, 359 serum samples were collected from randomly selected small ruminants in the same flocks. The collected serum samples were analyzed to determine the seropositivity using a monoclonal antibody-based C-ELISA. The pre-vaccination seropositivity of 72.3% (95% CI: 67.8-76.4) increased to 93.9% (95% CI: 90.9-95.9) post-vaccination (P < 0.001). The observed seropositivity following vaccination was above the recommended herd immunity threshold (80%) required to reduce the transmission of infection in the population sufficient to eliminate virus. A survey of sampled flocks six months post-sampling indicated only 68% of animals were still present in these flocks. This population turnover reduces the herd immunity to about 64% which is below the required threshold for control. The high level of herd immunity achieved post-vaccination indicates good vaccine quality, cold chain maintenance and effective vaccine delivery in the district's vaccination campaigns. The decrease in herd immunity associated with population turnover and annual vaccination intervals represents a challenge to effective control and suggests changes to the timing or frequency of the vaccination is required.

Pastoralist knowledge of sheep and goat disease and implications for peste des petits ruminants virus control in the Afar Region of Ethiopia

Pastoralist areas of Ethiopia are vulnerable to drought, causing livelihood loss and famine. One approach to increasing pastoralist resilience is the control of livestock disease, but there is limited information from pastoralist areas to inform control strategies. This study aimed to explore pastoralist concepts of small ruminant disease and implications for infectious disease surveillance and control in the pastoralist Afar Region.

During 2013–14, qualitative and quantitative methods were applied in two villages of one district in the mid-west of the region. Semi-structured group interviews, incorporating participatory tools, explored pastoralist knowledge of small ruminant diseases and their impact. These were followed by multiple visits in different seasons to 70 households for semi-structured and informal interviews, observation of management practices, clinical examinations, and weekly questionnaires of mortality and morbidity. Thematic analysis was applied to interview transcripts and field notes, and descriptive statistical analysis to quantitative data.

Afar concepts of disease causation, terminology and treatment were predominantly naturalistic, related to observable signs and physical causes, rather than personalistic factors (misfortune due to magical or spiritual agents). Disease occurrence was associated with malnutrition and adverse weather, and disease spread with contact between animals during grazing, watering and migration. Disease occurrence varied by season with most syndromes increasing in frequency during the dry season.

Names for disease syndromes were related to the main clinical sign or body part affected; 70 terms were recorded for respiratory syndromes, diarrhoea, sheep and goat pox, lameness, skin diseases, ectoparasites, urinary and neurological syndromes and abortion. Some syndromes with pathognomonic signs could be linked to biomedical diagnoses but most were non-specific with several possible diagnoses. The syndromes causing greatest impact were diarrhoea and respiratory disease, due to mortality, reduced milk production, weight loss, abortion, weak offspring and reduced market value. Afar applied a range of traditional methods and modern medicines to prevent or treat disease, based on livestock keeper knowledge, advice of local specialists and occasionally advice from district veterinarians or animal health workers.

In relation to surveillance for peste des petits ruminants (PPR), several terms were used for PPR-like syndromes, depending on the predominance of respiratory or diarrhoea signs. Therefore, whenever these terms are encountered during surveillance, the associated disease events should be fully investigated and samples collected for laboratory confirmation. The Afar naturalistic concepts of disease parallel biomedical concepts and provide a good foundation for communication between veterinarians and pastoralists in relation to PPR surveillance and control measures.

Epidemiological Survey of Peste des Petits Ruminants in Ethiopia: Cattle as Potential Sentinel for Surveillance

Peste des petits ruminants (PPR) is a highly contagious viral disease of small ruminants; it emerged in countries previously free of the disease following the eradication of rinderpest. PPR is classified by international organizations as the next priority animal disease for global eradication campaign. Assessment of the local situations is the first step in the eradication efforts. The objective of this study was to investigate and compare the seroprevalence of PPR in cattle, sheep, and goats under two livestock production systems in Ethiopia: North Shewa zone of Amhara region represents a highland sedentary life style characterized by mixed livestock-crop production system; Zone Three of Afar region represents a lowland nomadic life style characterized by pastoral livestock production system. N-competitive ELISA PPR test was performed on sera from 2,993 animals ≥6 months old sampled at watering and grazing points. Multivariable logistic regression models comparing the seropositivity between the two production systems were built by classifying doubtful results as positive, negative, or excluding them from the data. The odds ratio (OR) comparing overall PPR seroprevalence in the sedentary North Shewa Zone compared to the nomadic Zone Three ranged from 19 to 27 (P < 0.001), depending on how doubtful results were classified, which contrasts with what has been reported in the literature. This is not likely to be related solely to vaccination, since seroprevalences in cattle and small ruminants were similarly high or low in the respective zones (0-4% for Zone Three and 20-40% for North Shewa Zone), and cattle were not likely to be vaccinated. The OR of seropositivity for goats compared to cattle ranged from 1.9 [95% confidence interval (CI): 1.3-2.7; P < 0.001] to 2.2 (95% CI: 1.5-3.1; P < 0.001) when doubtful results were excluded or classified as negative, respectively. When doubtful results were classified as positive, association between seropositivity and animal species was not significant (P > 0.05). Our results suggest to further investigate cattle as sentinel animals for PPR surveillance.

Prevalence of Pneumonia in Sheep and Goats Slaughtered at Elfora Bishoftu Export Abattoir, Ethiopia: A Pathological Investigation

Accurate clinical diagnosis of pneumonia, the leading cause of mortality in small ruminants, is difficult and usually requires postmortem examination of the lungs. An active abattoir survey was conducted between November 2017 and April 2018 to estimate the prevalence and characterize the gross and histopathological lesions of pneumonic lungs in 864 clinically healthy young small ruminants (490 sheep and 374 goats aged 1.5 to 3 years) raised for meat in different parts of the country and slaughtered at Elfora Bishoftu export abattoir, Ethiopia. Out of the total lungs examined grossly, pneumonic lesions were found in 158 (18.29%) lungs. On histopathological examination of the lungs with gross pneumonic lesion, however, typical pneumonic lesions were diagnosed in 148 (17.13%) lungs only. No significant (p>0.05) difference was noted in the prevalence of pneumonia between sheep (17.14%) and goats (17.11%) in histopathological examination. Based on the predominant histopathological findings, the pneumonic lesions were characterized as interstitial pneumonia (41.9%), acute suppurative bronchopneumonia (25.7%), acute fibrinous bronchopneumonia (24.3%), chronic bronchopneumonia (6.1%), aspiration pneumonia (4.7%), bronchointerstitial pneumonia (3.4%), and ovine pulmonary adenomatosis (3.4%). The study further showed the spread of ovine pulmonary adenomatosis and ovine progressive pneumonia (Maedi) from the central highlands to areas that were previously free from these diseases. Due to its better diagnostic capacity, histopathology should be employed routinely as an ancillary test in the major abattoirs and regional veterinary laboratories to generate additional epidemiological data for a better disease control and prevention measures. Further studies are also recommended to identify the etiological agents of pneumonia in sheep and goats and thereby to formulate feasible and cost-effective interventions.

Molecular detection and phylogenetic analysis of Peste des petits ruminants virus circulating in small ruminants in eastern Amhara region, Ethiopia

Background

Peste des Petits Ruminants (PPR) is a severe, highly infectious and fatal viral disease of small ruminants. Four lineages of PPR virus have been identified globally based on sequence analysis of the nucleoprotein (N) and fusion (F) gene. The aim of this study was to isolate and genetically characterize recently circulating PPR virus in small ruminants in the eastern Amhara region in Ethiopia. A total of 28 anti-mortem samples (gum debris, nasal and ocular swab) were collected from clinically suspicious animals and examined for the presence of PPRV by a one-step RT-PCR assay. Samples positive with RT-PCR were subjected to isolation of the virus which were subsequently genetically characterized by sequencing of the nucleoprotein (N) gene and phylogenetic analysis of PPR virus (PPRV) strains.

Results

Of the 28 clinical samples examined, 46.4% were positive with RT-PCR for viral nucleic acid. The PPRV was successfully isolated on CHS-20 cell line with the ovine signaling lymphocyte activation molecule (SLAM) receptor expressed on the cell surface and confirmed with RT-PCR and IFAT assay. The nucleotide sequence and phylogenetic analysis indicated that the PPRV obtained were clustered genetically with Lineage IV isolates of the virus.

Conclusion

The successful isolation of the virus and molecular findings of this study confirmed active lineage IV PPRV infections among populations of sheep and goats in eastern Amhara, suggesting risks for potential spread of the disease to currently free areas. Thus, we recommend systematic vaccination to contain outbreaks in affected districts and geographically linked surrounding districts to which the disease could potentially spread due to different epidemiological linkages.

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.

Serological Investigation of Peste Des Petits Ruminants in East Shewa and Arsi Zones, Oromia Region, Ethiopia

Peste des petits ruminant (PPR) is an economically important disease of small ruminants with a rapidly expanding geographical distribution. There are fragmented reports to the occurrence and distribution of the disease in Ethiopia. A total of 700 serum samples were collected from goats and sheep to detect the presence of antibody against PPR virus using Competitive Enzyme-Linked Immunosorbent Assay (C-ELISA). An overall PPR seropositivity was reported to be 48.43% in the area. There is no statistically significant difference in the seroprevalence of the disease between sheep and goats (50.85% and 46.68%), respectively. However, there was statistically significant variation (P < 0.05) in the seroprevalence of the disease in young (33.9%) and adult (55.8%) age categories. The seroprevalence in male and female was 42.07% and 50.09%, respectively, where the variation was statistically not significant (P > 0.05). High seroprevalence of Peste des petites ruminants in the study area indicated the virus circulation and endemicity of the disease. The disease causes substantial economic losses by affecting the livelihood of the farmers. Therefore, control measures should be put in place to minimize the loss associated with the disease.

Peste des petits ruminants (PPR): A neglected tropical disease in Maghreb region of North Africa and its threat to Europe

BACKGROUND

Peste des petits ruminants (PPR) is a contagious disease listed by the World Organisation for Animal health (OIE) as being a specific hazard. It affects sheep, goats, and wild ungulates, and is prevalent throughout the developing world particularly Asia, the Middle East, and Africa. PPR has been targeted for eradication by 2030 by the Food and Agriculture Organization of the United Nations (FAO) and the OIE, after the successful eradication of the related disease, rinderpest in cattle. PPR was first reported in 1942 in the Ivory Coast in Western Africa and has since extended its range in Asia, the Middle East, and Africa posing an immediate threat of incursion into Europe, South East Asia and South Africa. Although robust vaccines are available, the use of these vaccines in a systematic and rational manner is not widespread, resulting in this devastating disease becoming an important neglected tropical disease in the developing world.

METHODOLOGY

We isolated and characterized the PPR virus from an outbreak in Cheraga, northern Algeria, during October 2015 by analyzing the partial N-gene sequence in comparison with other viruses from the Maghreb region. As well as sequencing the full length viral genome and performing real-time RT-PCR on clinical samples. Maximum-likelihood and Bayesian temporal and phylogeographic analyses were performed to assess the persistence and spread of PPRV circulation from Eastern Africa in the Maghreb region of North Africa.

CONCLUSIONS

Recent PPR outbreaks in Cheraga, in the northern part of Algiers (October 2015) and North-West Morocco (June, 2015) highlight that PPRV has spread to the northern border of North Africa and may pose a threat of introduction to Europe. Phylogeographic analysis suggests that lineage IV PPRV has spread from Eastern Africa, most likely from the Sudan 2000 outbreak, into Northern Africa resulting in the 2008 Moroccan outbreak. Maximum-likelihood and Bayesian analysis shows that these North African viruses cluster closely together suggesting the existence of continual regional circulation. Considering the same virus is circulating in Algeria, Morocco and Tunisia, implementation of a common Maghreb PPR eradication strategy would be beneficial for the region.

Seroprevalence, distribution and risk factor for peste des petits ruminants (PPR) in Algeria

Peste des petit ruminants (PPR) is a highly contagious and infectious viral disease of small ruminants with severe socio-economic implications. The disease was first reported in the Southern part of Algeria in 2011 and by February 2012 it has reached the central part of the country. Estimating national prevalence, distribution and identification of risk factors remains a key component in understanding the epidemiology and control of the disease. The present study was carried out between January and June 2014, to include a detailed description of flock and within-flock seroprevalence and risk association between PPR seropositivity and various flock management factors in Algeria. A total of 150 flocks randomly sampled across the country were investigated and 4552 serum samples were collected from 3336 sheep and 1216 goats, respectively. C-ELISA was used to detect the presence of antibodies in small ruminant animals as an indicator of PPRV exposure. The results showed an overall true flock seroprevalence of 30.45% [95% CI 23.76-37.14] with a mean of the true within-flock prevalence as 29.87%±2.11. The mean of the true within-flock prevalence in mixed flocks (12.93%±1.85) was however found to be significantly higher than sheep flocks (5.74%±1.06). Also the mean of the true within-flock prevalence was found to be significantly higher in adult (35.36%±3.13) compared to young animals (21.83%±2.47) and in females (33.11%±2.87) compared to males (22.14%±2.31). The univariate analysis revealed that PPR overall flock seroprevalence was significantly higher (P<0.20) in large flock (50.61%) than in small flock (33.33%), in mixed flock (56.7%) than in sheep flock (35.35%) and in the flocks that had contact with other flocks (46.5%) compared to those who had not (30.6%). However the differences among studied regions and grazing system were not statistically significant. For the risk factor analysis, univariate analysis of variables followed by a multiple logistic regression identified mixed flocks [OR=2.64, 95% CI 1.30-5.38; P=0.007] and contact with other flocks [OR=2.27, 95% CI 0.99-5.21; P=0.053] as risk factors in the spread of the disease. In conclusion, this study revealed a high seroprevalence of PPR in Algerian small ruminants, therefore the establishment of early warning systems and comprehensive implementation of control measures are advocated to improve animal welfare and reduce economic losses.

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

BACKGROUND

Peste des petits ruminants (PPR) is a contagious viral disease of small ruminants. Serum samples from sheep (n = 431) and goats (n = 538) of all ages were collected in a cross-sectional study in Turkana County, Kenya. The objective was to estimate the sero-prevalence of PPR virus (PPRV) infection and associated risk factors in both species. PPRV competitive enzyme-linked immuno-sorbent assay (c-ELISA) analysed the presence of antibodies in the samples. All analyses were conducted for each species separately. Multivariable logistic regression models were fitted to the data to assess the relationship between the risk factors and PPRV sero-positivity. Mixed-effect models using an administrative sub-location as a random effect were also fitted to adjust for possible clustering of PPRV sero-positivity. Intra-cluster correlation coefficients (ρ) that described the degree of similarity among sero-positive responses for each species in each of the six administrative divisions were estimated.

RESULTS

Goats had a significantly higher sero-prevalence of 40% [95% confidence interval (CI): 36%, 44%] compared to sheep with 32% [95% CI: 27%, 36%] (P = 0.008). Combined sero-prevalence estimates were heterogeneous across administrative divisions (n = 6) (range 22% to 65%) and even more across sub-locations (n = 46) (range 0% to 78%). Assuming that PPRV antibodies are protective of infection, a large pool of PPRV susceptible middle age group (>6 months and < 24 months) in both species was estimated. This was based on the low sero-prevalence in this group in goats (14% [95% CI: 10%, 20%]) and in sheep (18% [95% CI: 13%, 25%]). Regression analysis returned significant risk factors across species: in sheep - vaccination status, age and administrative division; in goats - sex, age, administrative division and sex*age interaction. The intra-sub-location correlation coefficients varied widely across divisions (range <0.001 to 0.42) and across species within divisions.

CONCLUSIONS

Biological, spatial and socio-ecological factors are hypothesized as possible explanations for variation in PPRV sero-positivity in the Turkana pastoral ecosystem.

Theileria infection in domestic ruminants in northern Ethiopia

Piroplasmosis caused by different tick-borne hemoprotozoan parasites of the genera Theileria and Babesia is among the most economically important infections of domestic ruminants in sub-Saharan Africa. A survey for piroplasm infection was conducted in three locations in Northern Ethiopia. Of 525 domestic ruminants surveyed, 80% of the cattle, 94% of the sheep and 2% of the goats were positive for different Theileria spp. based on PCR of blood followed by DNA sequencing. Sheep had a significantly higher rate of infection compared with cattle (P<0.0003) and both sheep and cattle had higher rates of infection compared to goats (P<0.0001). Four species of Theileria were detected in cattle: T. velifera, T. mutans, T. orientalis complex and T. annulata with infection rates of 66, 8, 4, and 2%, respectively. This is the first report of T. annulata, the cause of Tropical Theileriosis in Ethiopia. Of the two Theileria spp. detected in small ruminants, T. ovis was highly prevalent (92%) in sheep and rare in goats (1.5%) whereas T. seperata was infrequent in sheep (2%) and rare in goats (0.4%). None of the animals were positive for Babesia spp.; however, Sarcocystis capracanis and S. tenella were detected in one goat and a sheep, respectively. The widespread distribution of Theileria spp. among cattle in northern Ethiopia including the virulent T. annulata and more mildly pathogenic T. mutans and T. orientalis, and the high infection rate in sheep with the usually sub-clinical T. ovis indicate extensive exposure to ticks and transmission of piroplasms with an important economic impact.

Prevalence and distribution of Peste des petits ruminants virus antibodies in various districts of Tanzania

Despite the widespread prevalence of infection with Peste des petits ruminants virus (PPRV) in goats and sheep industry in Asia and sub-Saharan Africa, there have been few, if any, structured population-based studies examining the epidemiology of this infection in Tanzania. In this study, we investigated the seroprevalence, and risk factors, of Peste des petitis ruminants(PPR) in sheep and goat flocks from seven different geographical administration authorities (Ngorongoro, Monduli, Longido, Karatu, Mbulu, Siha and Simanjiro) located in Northern Tanzania. Serum samples from 657 and 892 sheep and goats, respectively, corresponding to 91 sheep/goat flocks and 43 villages were collected. Competitive enzyme linked immunosorbent assay (c-ELISA) was used to detect the presence of antibodies in the serum against PPRV. Chi-square analysis and multivariable logistic regression model were used to identify risk factors for PPRV seropositivity. Findings suggested that the sero-positive cases were significantly higher in goats than in sheep (49.5% versus 39.8%; P=0.002). The overall seroprevalence of PPRV infection in small ruminants was 45.8%. Highest seroprevalence (42.6-88.02%) was observed in Mbulu, Siha, Longido, Ngorongoro districts, while antibodies less than 40% to none were found in serum from Monduli, Karatu and Simanjiro, respectively. These findings confirm natural transmission of PPRV under field condition for the first time in Tanzania. Results may be correlated with variations in the sheep and goat husbandry practices within different geographic localities, the uncontrolled movement of animals, the levels of natural immunity and the sharing of grazing field amongst agro and pastoralists.

Risk factors associated with observed clinical lumpy skin disease in Ethiopia

A cross-sectional study based on a questionnaire survey was conducted to determine the distribution of lumpy skin disease (LSD) and associated risk factors in three main agro-climatic zones of Ethiopia. A total of 330 questionnaire surveys were collected from 44 peasant associations (PA) distributed in 15 districts. Across agro-climate zones, herd-level LSD prevalence in the midland agro-climate was significantly higher 55.2% [95% confidence interval (CI) 47.5-62.6] than in highland and lowland agro-climate zones. Overall observed LSD prevalence at animal-level was 8.1% (95% CI 7.3-8.9) and observed mortality was 2.12% (95% CI 1.73-2.6). The odds ratio (OR) of LSD occurrence in midland vs. highland and lowland vs. highland zones was 3.86 (95% CI 2.61-5.11) and 4.85 (95% CI 2.59-7.1), respectively. Significantly high risk of LSD occurrence was associated with communal grazing and watering management (OR 4.1, 95% CI 2.02-6.18) and introduction of new cattle (OR 8.5, 95% CI 6.0-11.0). Our findings describe the distribution of LSD in different agro-climates in Ethiopia along with associated risk factors, and can help shed light on the epidemiology of LSD in other African countries suffering from the disease.