First PCR Confirmed anthrax outbreaks in Ethiopia—Amhara region, 2018–2019

Abstract

Background

Anthrax is a disease that affects humans and animals. In Ethiopia, anthrax is a reportable disease and assumed to be endemic, although laboratory confirmation has not been routinely performed until recently. We describe the findings from the investigation of two outbreaks in Amhara region.

Methods

Following reports of suspected outbreaks in Wag Hamra zone (Outbreak 1) and South Gondar zone (Outbreak 2), multi-sectoral teams involving both animal and public health officials were deployed to investigate and establish control programs. A suspect case was defined as: sudden death with rapid bloating or bleeding from orifice(s) with unclotted blood (animals); and signs compatible with cutaneous, ingestion, or inhalation anthrax ≤7 days after exposure to a suspect animal (humans). Suspect human cases were interviewed using a standard questionnaire. Samples were collected from humans with suspected anthrax (Outbreak 1 and Outbreak 2) as well as dried meat of suspect animal cases (Outbreak 2). A case was confirmed if a positive test was returned using real-time polymerase chain reaction (qPCR).

Results

In Outbreak 1, a total of 49 cows died due to suspected anthrax and 22 humans developed symptoms consistent with cutaneous anthrax (40% attack rate), two of whom died due to suspected ingestion anthrax. Three people were confirmed to have anthrax by qPCR. In Outbreak 2, anthrax was suspected to have caused the deaths of two livestock animals and one human. Subsequent investigation revealed 18 suspected cases of cutaneous anthrax in humans (27% attack rate). None of the 12 human samples collected tested positive, however, a swab taken from the dried meat of one animal case (goat) was positive by qPCR.

Conclusion

We report the first qPCR-confirmed outbreaks of anthrax in Ethiopia. Both outbreaks were controlled through active case finding, carcass management, ring vaccination of livestock, training of health professionals and outreach with livestock owners. Human and animal health authorities should work together using a One Health approach to improve case reporting and vaccine coverage.

Author summary

Anthrax is a bacterial disease that causes rapid death in livestock, particularly cattle. Humans can be infected when they touch or eat animal carcasses or animal products, or when they inhale bacterial spores that have been aerosolized from the environment. Depending on how the bacterium enters the body, it causes cutaneous, gastrointestinal/oropharyngeal or respiratory disease in humans; death is rare for cutaneous anthrax but is more common with ingestion and inhalation forms of the disease. Anthrax has a global distribution but some areas of the world–such as Ethiopia–experience annual outbreaks in animals and humans. In this report, we present the findings from the first PCR-confirmed outbreaks in Ethiopia. In both outbreaks, the lack of farmer awareness and inherent economic value of livestock led farmers to salvage carcasses of animals that died, for meat and hides. Community members who participated in skinning and butchering of carcasses, eating or handling the meat, or processing hides/skins of suspect animal cases developed clinical signs consistent with anthrax (22 humans in Outbreak 1 including two suspected deaths; and 18 in Outbreak 2 including one suspected death). Further, animal parts from index cases (one cow in Outbreak 1; and one cow and one goat from Outbreak 2) were improperly discarded around the environment, leading a further 48 cows to become infected and die in Outbreak 1. Three humans in Outbreak 1 tested positive for anthrax on PCR. In addition, a swab taken from the dried meat of an animal that died in Outbreak 2 was positive by PCR. In both outbreaks, control was enacted through recalling and disposing remaining animal products, vaccination of livestock in surrounding areas and community education.