INVESTIGATION OF ANTHRAX OUTBREAKS IN ANIMALS IN ETHIOPIA: ISOLATION AND MOLECULAR DETECTION OF BACILLUS ANTHRACIS

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2019-06

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Abstract

Anthrax is a zoonotic disease caused by Bacillus anthracis (B. anthracis), a grampositive, non-motile, and spore-forming bacterium. Animal anthrax is an important and zoonotic disease in Ethiopia and only few of those cases were isolated by laboratory. Outbreak investigation of anthrax suspected cases was conducted from November 2018 to June 2019 in south Gonder, Illubabor, Wolayita, Gurage Zone and Zone 4 of Afar region of Ethiopia, where five different outbreaks in different animal species were reported. Purposive sampling method was used in suspected outbreak cases in domestic animals (cattle and goat) and wild animals such as hippopotamus. Anthrax suspected samples were tested under appropriate biosafety and containment. A total of 63 different samples like nasal swab, rectal swab, tissue, and swab from old carcasses and environmental samples were collected, labeled, packed and transported to NAHDIC, Sebeta for further processing. Isolations of B. anthracis was conducted by culturing on blood agar, colony characterization, Gram staining, spore and capsule staining and biochemical tests. The molecular detection was conducted by real-time polymerase chain reaction. 9.8% (6/61) of B. anthracis was identified from dried meat (Quwanta) samples from outbreak cases in South Gondor, Farta District and the Bacillus isolates were nonhemolytic, non-motile and susceptible to penicillin, which is typical of B. anthracis. The identified colonies were further confirmed by real-time PCR, where B. anthracis virulent plasmid markers namely protective antigen (on plasmid pXO1) and capsule (on plasmid pXO2) were detected. This is the first report of PCR confirmed anthrax outbreak case from animals in Ethiopia. Anthrax still remains endemic in the country and causes diseases in livestock. A multi-sectoral collaborative approach and capacity buildings are essential for successful prevention and control of the disease and joint outbreak investigation, proper and timely animal immunization.

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Anthrax, animals, Bacillus anthracis

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