Anthrax is killing wildlife, and it’s putting humans at risk, too
A suspected anthrax outbreak is raising alarm at Lake Nakuru National Park in Kenya after the sudden deaths of 10 buffalo since last month, and officials are working to make sure the outbreak doesn’t put humans at risk.
Anthrax outbreaks in wildlife and livestock often stir concern because the disease can spread to humans who might come in contact with an infected animal or eat meat or drink milk from an infected animal.
In people, anthrax can be fatal if left untreated, and symptoms depend on the type of infection, such as small blisters for cutaneous anthrax; fever and chills for inhalation anthrax; or sore throat and nausea for gastrointestinal anthrax.
“Visitors to our park are at no risk if they observe park rules on avoiding contact with wild animals and we encourage them to continue with their tours,” Susan Koech, principal secretary of Kenya’s State Department of Wildlife, said in a news release Monday.
The first case in the outbreak was confirmed to be anthrax last week; the death was reported March 29, according to the release.
The release also noted that the outbreak has been contained and officials are monitoring the situation. A team of veterinarians and park rangers is vaccinating animals to prevent further spread of the disease. The park lost buffalo and rhinos in 2015 in a similar anthrax outbreak.
Sporadic cases of anthrax occur in animals worldwide, and there are occasional outbreaks in Africa and central Asia, according to the World Health Organization. Before the use of veterinary vaccines, anthrax was a major cause of deadly disease in livestock such as cattle, sheep, goats, camels, horses and pigs throughout the world.
“Having contact with animals that have died from anthrax is actually the most common route for humans to become infected with anthrax,” said Caitlin Cossaboom, an epidemic intelligence service officer in the Bacterial Special Pathogens Branch at the US Centers for Disease Control and Prevention.
“Anthrax is difficult to control, and outbreaks can be very difficult to predict,” she said. “A seasonal pattern of anthrax outbreaks has actually been described, particularly related to cycles of heavy rainfall that are followed by periods of drought when it’s very dry and hot.”
One massive anthrax outbreak among wildlife in Namibia killed more than 200 hippopotamuses and Cape buffalo between September and December 2017, putting people and livestock at huge risk of becoming infected.
In that case, even though more than 1,000 people were identified as having contact with or consuming meat from animals involved in the outbreak, there were no reported human cases or deaths.
The details about how humans were protected in the outbreak are shared in a paper led by Cossaboom and published in the journal Emerging Infectious Diseases on Wednesday.
The key to keeping anthrax away from humans
Dozens of hippopotamus and Cape buffalo carcasses were found along the Kavango River in Bwabwata National Park in Namibia in fall 2017, the first eerie evidence of that anthrax outbreak.
Namibia’s Ministry of Environment and Tourism, the Ministry of Health and Social Services and the Ministry of Agriculture, Water and Forestry worked together to contain the outbreak. The CDC also helped the Namibian ministries.
The CDC worked closely with Namibia to collect specimens from affected wildlife carcasses for use with the newly developed Active Anthrax Detect Rapid Test. The paper described this use of the test in the field as “successful.”
Namibia’s Ministry of Health and Social Services developed and administered a questionnaire to identify people living in communities adjacent to Bwabwata National Park who were exposed to the carcasses.
Through the questionnaire, 1,050 people were identified as having contact with or consuming meat from the carcasses, according to the paper. They were immediately provided with post-exposure prophylactic antibiotics.
Meanwhile, the Ministry of Agriculture, Water and Forestry secured about 10,000 doses of livestock anthrax vaccine and administered the vaccines to prevent spillover of anthrax from wildlife to susceptible domestic animals — and subsequently to humans.
“Anthrax is only one of many, many diseases that are zoonotic, meaning they can be spread between animals and humans,” Cossaboom said. “Some examples of this include rabies, which can be spread through bites from infected animals to humans, and rabies, also like anthrax, can be controlled by controlling it in animals.”
As prevention efforts were employed, the Ministry of Environment and Tourism started removing all of the dead animal carcasses from the Bwabwata National Park.
“The response in this outbreak — including rapidly identifying people that had been exposed to the dead animals, providing them with antibiotics post-exposure and then starting the community engagement to raise awareness on what was going on — was so critical,” Cossaboom said.
“All of those actions together — or this really rapid multisectorial response — was the key to having a successful outcome,” she said. “Fortunately, because of all of those efforts and the rapid response, there were no human cases, despite over 1,000 people being exposed in this case.”
‘Human risk always exists’
The paper shows how a fast-acting multidisciplinary approach can prevent an outbreak in wildlife from becoming an outbreak in humans, said Dr. Amesh Adalja, a senior scholar at the Johns Hopkins Center for Health Security and member of the Infectious Diseases Society of America, who was not involved in the research.
“Human risk always exists with anthrax outbreaks in animals,” Adalja wrote in an email.
“Anthrax is a zoonotic disease with human cases often tied to animal exposure. For example, multiple cases have occurred at African drumming events when individuals were exposed to animal drum skins that contained anthrax spores,” he said.
“Because of the risk of spillover into humans, it is crucial to monitor animal anthrax outbreaks and delimit the exposure of humans while promptly administering post-exposure antibiotics to those exposed. It is also important to emphasize Anthrax is a major biowarfare threat and being prepared for outbreaks of animal origin directly enhances abilities to respond to a potential bioattack using anthrax.”