Epidemiology and Identification of Peste des petits Ruminants (ppr) Virus Circulating in Small Ruminants of Eastern Amhara Region Bordering Afar, Ethiopia
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Date
2014-06
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Addis Ababauniversity
Abstract
A cross-sectional study design was employed between November 2013 and April 2014 to determine antibody/immunity level of vaccinated sheep and goats at herd level, to determine the sero-prevalence and risk factors of PPR in non-vaccinated areas and to investigate incidence and recent circulation of PPR virus in field samples collected from small ruminants of eastern Amhara region bordering Afar, Ethiopia. A total of 969 serum samples were collected from sheep and goats in the study districts. Multistage sampling, with four hierarchical stages, was used as sampling strategy. Peasant Association /villages and individual animal were selected by random sampling. A total of 32 samples, comprising 18 swab samples and 14 heparinized whole blood samples were collected from the suspected animals for the presence of PPR viral antigen. 28 samples were examined for the presence of PPRV RNA by one step RT-PCR assays. Anti-mortem samples were collected from active cases with the aim of virus isolation. In addition five years retrospective data on PPR outbreak was used in the present study. Questionnaire survey was also conducted to assess the association of seroprevalence of PPR and possible risk factors. Proportions were calculated for seroprevalence visa-vis fixed factors that included animal species, sex and age, districts and village. Univariable analysis for the proportions was carried out using Chi-square analysis in Epi Info software. A confidence limit of less than 5% was used to indicate a significant level. All variables with P < 0.05 (two-sided) in the univariable analysis were further tested by multivariable logistic regression model to assess their effect on PPR seropositivity. Clinical signs of PPR were observed in both sheep and goats, in both sex and all age
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groups, in the all study districts. The clinical signs included high fever, ocular and nasal discharge, few abortions, respiratory distress and diarrhea. The disease outbreak was severe in Habru district with morbidity, mortality and case fatality rates of 21.9%, 8.4% and 38.4 % in small ruminants, respectively. The overall seroprevalence of PPR virus antibody was 28.1%, 64.5% and 56.5% in unvaccinated, vaccinated and unknown vaccination status of small ruminants, respectively. The multivariable logistic regression model revealed residing in Rayakobo district, adult age, communal grazing and recent introduction of new animals as risk factors for PPR seropositivity in sheep and goats. There was statistically significant (p= 0.000) differences in the level of seroconversion among the vaccinated districts with similar vaccine response of different age groups, sex, and species involved. In unvaccinated population around 28.1% and only 24.5% were with PI > 50% and 76%, respectively, whereas in vaccinated population around 64.5% and 58.8% of animals were with PI > 50% and 76%, respectively. The median value of PI is 26 and 83 for unvaccinated and vaccinated population, respectively indicating the success of the vaccine administered as the population has gained protection with 57 additional value of PI due to vaccination. 31.3% and 46.4 % of clinical samples examined were positive with Ic-ELISA for PPR viral antigen and RT-PCR for viral nucleic acid, respectively. The species-wise disease outbreaks were more severe in goats than sheep with both tests. The PPR virus were also successfully isolated on CHS-20 cell lines and confirmed with RT-PCR and IFAT assay only from samples collected from Habru district. The clinical and molecular findings of this study confirmed the circulation of PPR virus among populations of sheep and goats in the study areas and prevalence in actual outbreaks situation, which should be kept in mind while deciding the vaccination strategy for the control of the disease. The restriction of movement of animals from endemic areas, with rigorous quarantine and surveillance procedures should be practiced to prevent the spread of the disease and the transmission of the virus to different localities.
Key words: PPRV, small ruminants, risk factors, herd immunity, Eastern Amhara
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Keywords
PPRV, small ruminants, risk factors, herd immunity, Eastern Amhara