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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Keywords
Anthrax, animals, Bacillus anthracis