In early May 2021, a tamandua was translocated from a drive-through zoo in Virginia (where animals can be viewed from visitors' vehicles) to a zoo in Washington County, Tennessee (Figure 1), where it was kept in an indoor habitat with one other tamandua and isolated from zoo visitors and wildlife. The tamanduas were not permitted out of the enclosure, and no known exposures to other animals occurred.
Timeline for public health investigation of a rabid tamandua (anteater) translocated from Virginia to Tennessee, May–August 2021
On June 29, the tamandua began exhibiting signs of illness including lethargy, anorexia, and diarrhea. A local veterinarian and veterinary technician at veterinary clinic A examined the tamandua on July 1. The animal was treated empirically with an antibiotic for presumed infection and vitamin K injections and returned to the zoo. After progression of clinical signs, including copious salivation, the animal was transported on July 6 to clinic B at a nearby veterinary medical college, where it was examined by a veterinarian, veterinary residents, interns, students, and a visiting veterinary consultant. Rabies was not considered in the differential diagnosis at this time because 1) there was no known bite exposure, 2) rabies had never been reported in a tamandua, and 3) the low basal body temperature of tamanduas (91°F [32.8°C]) was believed to contribute to decreased susceptibility to rabies virus infection. Routine diagnostics failed to reveal a primary cause, and supportive care was unsuccessful in improving the animal's condition, necessitating euthanasia on July 6.
Necropsy, including removal of brain tissue using an electric oscillating saw, was completed at the veterinary medical college. Laboratory gowns and latex gloves were used in the necropsy suite; no additional personal protective equipment, such as eye and respiratory protection, was used. Brain tissue was submitted to an academic laboratory for histopathology. The head was not submitted to the state public health laboratory; therefore, no fresh brain material was available for rabies testing. The academic laboratory reported a preliminary positive rabies result by immunohistochemistry test on August 16, approximately 6 weeks after euthanasia. The process was not expedited because rabies was not in the differential diagnosis at time of death. TDH was notified of the positive test result, fixed brain tissue was requested, and it was submitted to CDC for confirmatory rabies testing. On August 21, rabies virus antigen was confirmed in the brain of the tamandua by immunohistochemistry and by reverse transcription–polymerase chain reaction assay. On August 26, molecular characterization determined that the rabies virus was most similar to the rabies virus variant (RVV) observed in raccoons in the eastern United States and reference sequences from Virginia. RVV was divergent from all available sequences from Tennessee, suggesting that rabies infection occurred while the animal was at the Virginia zoo (Figure 2).
Phylogenetic analysis of rabies virus nucleoprotein gene from the rabid tamandua* identified in Tennessee with raccoon rabies virus variant sequences† from Tennessee, Virginia, and other nearby states, 2021
*Specimen labeled A21–2444 was collected from the rabid tamandua. This specimen clustered with rabies virus sequences from the northeast and mid-Atlantic regions and is separate from specimens from the southeast.
†Branch length is related to the number of nucleotide substitutions. The more substitutions, the longer the branch.
Morbidity and Mortality Weekly Report. 2022;71(15):533-537. © 2022 Centers for Disease Control and Prevention (CDC)