SEROTYPING AND MOLECULAR CHARACTERIZATION OF FMD VIRUS ISOLATED FROM OUTBREAK CASES IN SELECTED AREAS OF OROMIA REGION AND ADDIS ABABA, ETHIOPIA
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2017-06
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Abstract
Foot and mouth disease (FMD) is an epitheliotropic and trans-boundary viral disease affecting cattle, sheep, goats and wild animals around the globe including Ethiopia. Outbreak investigation and cross-sectional study design was conducted from September 2016 to April 2017 with the objectives of isolation, serotyping, molecular characterization and to determine risk factors for the occurrence of the disease in selected outbreak areas of Oromia region and Addis Ababa, Ethiopia. Purposive sampling was done in the respective districts and kebeles where the outbreaks occurred. A total of 586 accessible cattle were examined in six districts and 226 (38.6%) showed clinical signs of the disease. Out of this, 352 animals were examined at Adea Berga dairy farm. Hence, outbreaks were investigated by collecting 123 samples from sick animals out of which 37 samples for virus isolation, 41 samples for identification of serotypes and 35 samples for molecular assays. Moreover, 312 bovine sera were collected from Welmera district during outbreak. The risk factor outbreak analysis showed that the overall morbidity and mortality at Adea Berga dairy farm was 36.9% and 3.12%, respectively. The risk of FMD infection in this farm was increased by 4.2 times (OR = 4.2, 95% CI (1.925-8.810) in calves than adult cattle. Among 312 sera samples, 30.8% (n=96) were FMD seropositive. The occurrence was (38.5%) in females and (15.8%) in males and it was statistically significant (χ2= 16.93, p = 0.001). Cross bred cattle were three times more likely to be infected (OR = 3.47, 95% CI: 2.10 -5.74) than local breeds. Furthermore, out of 37 cultured samples, 56.8% (n=21) exhibited FMDV cytopathic effect (CPE) and the viruses were isolated. A total of 41 samples were processed for antigen typing and 39.02% (n=16) were positive. The identified serotypes were; serotype O (34.2%), serotype A (17.1%), serotype SAT1 (4.9%) and serotype SAT2 (2.4%). Out of 50 samples tested by rRT- PCR, 18.1% (n=9) were positive for FMDV genome with Ct values ranging from 16.03-26.98 that were recorded in epithelial tissues and probang samples. Of the four serotypes identified, only serotype O virus isolates were characterized at molecular level by phylogenetic tree reconstruction. The isolates belonged to East Africa topotype-4 (EA-4). In conclusion, the study showed four serotypes were prevalent in the study areas; FMD control therefore depends to be instituted based on the availability of matching and potent vaccine against the serotypes per area.
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Addis Ababa, Cattle, FMDV, Risk factor, Seroprevalence