Study links Ebola outbreaks to animal carcasses

Awareness and wildlife health monitoring is key to preventing future fatalities

All recent Ebola virus outbreaks in humans in forests between Gabon and the Republic of Congo were the result of handling infected wild animal carcasses, according to a study by the Wildlife Conservation Society (WCS) and its regional partners. Appearing in the February edition of the journal Emerging Infectious Diseases, the study found that many animal carcasses tested for Ebola between 2001 and 2003 produced positive results, and found direct links between the deadly disease in animal populations and humans.

“This research proves that hunting and consumption of great apes represent a serious health risk for people in Central Africa, and a risk that can be avoided,” said Dr. William Karesh, field veterinarian for the Wildlife Conservation Society and a co-author on the paper. “What we need now is improved awareness of this risk in communities where bushmeat is still a source of sustenance and continued monitoring of wildlife in the region. We have identified a ’win – win’ opportunity by using this information to both protect endangered apes from illegal hunting and to protect humans from deadly outbreaks.”

The paper provides definitive proof for the assumption that Ebola moves from wildlife populations to humans through the consumption or handling of carcasses or bushmeat.

Specifically, the researchers found that Ebola infections in wild animals such as gorillas, chimpanzees, and occasionally duikers (a diminutive antelope species), move across the human-wildlife divide through hunters taking either sick animals or carcasses for meat. Hunters can then spread the disease to families and hospital workers, creating the conditions for an epidemic in the process.

Between August 2001 and June 2003, researchers noted that wildlife outbreaks occurred prior to five human outbreaks in the same relative locations. During this same period, 98 animal carcasses were discovered in the region straddling northeast Gabon and the northwest Republic of Congo. Of these carcasses, 21 gorilla, chimp and duiker carcasses were tested for the Ebola virus, with 14 samples being found positive. In 11 cases, instances of human infection were directly linked to gorilla, chimpanzee and duiker carcasses.

To prevent future outbreaks from becoming health crises, health officials and wildlife researchers must continue to work together in monitoring the region’s wildlife for signs of Ebola. Shortly after August 2001, participating agencies founded the Animal Mortality Monitoring Network in collaboration with Gabonese and Congolese Ministries of Forestry and Environment to predict and prevent outbreaks. On two occasions since then, the network alerted health authorities about potential human outbreaks weeks before they occurred.

“The signs of potential outbreaks often occur in remote areas, where roads are barely usable and communications limited,” added Karesh. “Conservation organizations such as WCS are therefore critical to the early detection of the conditions that can lead to deadly health emergencies.”