In May 2021, an anteater was relocated from a zoo in Virginia to one in Washington County, Tennessee.
After a little more than a month, the animal started exhibiting signs of illness: lethargy, anorexia and diarrhea. After receiving treatment on July 1, the anteater’s condition worsened and it was euthanized on July 6 — with no known cause of death at the time.
The veterinary clinic where the animal was euthanized performed a necropsy using limited personal protective equipment further, and submitted brain tissue from the anteater for testing. On Aug. 16, testing reveled a preliminary positive rabies test, which was confirmed by the US Centers for Disease Control and Prevention five days later.
Further testing of the brain sample led investigators to conclude the anteater was likely infected by raccoons at a drive-through Virginia zoo, as the variant of the rabies that anteater had was different from all available sequences of raccoon rabies variants in Tennessee. The CDC analysts said they ruled out local transmission of this variant, which is not enzootic to Washington County.
“Expansion of rabies zones in the United States through translocation has significant adverse public health implications, including threatening the health of humans, domestic animals, and other wildlife; and potentially requiring changes in wildlife rabies control measures,” a report from the CDC said.
It is the first case of rabies documented in this species of anteater, Tamandua tetradactyla, a lesser anteater called the South American collared anteater. Rabies was not considered as a possible cause of death, because there was no known bite exposure, rabies had never been reported in the species before and, prior to this case, the low body temperature of tamanduas was believed to make them less susceptible to rabies infection.
“This case study was really unique because it did expand our understanding of the mammalian species that can become infected with rabies,” said Dr. Heather Grome with the Tennessee Department of Health, one of the lead investigators on the case. “We know that rabies can infect all mammals, theoretically, but not all of them have a documented infection, and so by documenting it in an anteater, it was just a very unique finding.
“And I think it also emphasizes the work of public health overall to remind people who routinely work with animals about the importance of rabies pre-exposure vaccines to help protect them in case of unexpected exposures to rabies,” Grome continued.
According to the CDC’s April 15 report, 13 people received a post-exposure rabies vaccine due to contact with the animal, but no human cases were reported as a result. Seven people received treatment because of known or presumed exposure to the animal’s saliva or because it couldn’t be determined if saliva made it into a scratch or open wound, while six others received it because of potential aerosolization of brain tissue during the necropsy.
Rabies is typically spread by a bite or saliva entering an open wound and is almost 100% fatal once clinical symptoms appear, according to the World Health Organization.
Grome said the case highlights the importance of rabies vaccination for both people and animals. Another tamandua at the zoo had to receive a rabies vaccine and was quarantined for six months because of exposure to the rabid one.
“I think that’s kind of our best method of preventing rabies transference is to make sure that animals are vaccinated or at least consideration of that before moving animals as opposed to testing them, for example,” Grome said. “I think vaccination is a much better approach, but I think it also goes back to our other key point where the people most at risk in this case investigation were the animal handlers who, unfortunately, weren’t aware that the animal was incubating or carrying rabies virus whenever it arrives to Tennessee.
“It’s just really important that we continue to support people who routinely work with animals being vaccinated themselves against rabies,” she continued.
The CDC report urged pre-exposure rabies vaccination for “all employees who work with animals in areas where rabies is endemic,” writing that three people at the Washington County zoo and veterinary staff involved in the case had not been vaccinated against the virus. Washington County has a skunk rabies variant enzootic to the area.
“This case also highlights the importance of continued public health efforts to expand awareness and education about rabies prevention and control, responsible animal ownership, routine rabies vaccination, appropriate personal protective equipment for barrier protection when performing laboratory procedures with potentially infected animals, and consistent interdisciplinary communication,” the report said.