In a substantial leap for wildlife conservation, two young elephants at the Cincinnati Zoo & Botanical Garden have turned a corner in their fight against the potentially deadly Elephant Endotheliotropic Herpesvirus (EEHV) after receiving an innovative mRNA vaccine. As reported by KHOU, the elephant calves named Sanjay and Kabir, were among a group transferred from Dublin Zoo and were identified as lacking critical maternal antibodies against EEHV, placing them at a high risk of the infection.
In response to the elevated threat level, the Cincinnati Zoo set up an in-house PCR lab specifically to monitor EEHV and administered plasma transfusions from exposed elephants to Sanjay and Kabir. Nevertheless, despite their efforts, the antibody levels from the transfusions did not reach those seen in elephants that naturally survived the infection. "We are incredibly grateful for this collaboration and that it helped save Sanjay and Kabir’s lives," Dr. Mike Wenninger, director of animal health at the Cincinnati Zoo, told WLWT.
The vaccines administered in Fall 2024 led to both elephants developing robust antibody responses, mirroring levels seen in naturally infected survivors—an outcome highlighting the success of the vaccine formulated by the Baylor College of Medicine and Houston Zoo. The Cincinnati Zoo remarked on the effectiveness of their approach, asserting the importance of this vaccine not only for the safety of zoo elephants but also for the conservation of the endangered Asian species in the wild.
When a herd mate began shedding the virus in February 2025, Sanjay's health was monitored closely. Early detection of low levels of EEHV in his system hinted at an infection, but with no symptoms developing, the virus cleared without the need for further treatment, a testament to the vaccine's efficacy. Kabir too, weathered a mild infection and swiftly recovered, as per details shared by KHOU. These cases are notably the first documented instances of natural EEHV exposure after vaccination.
Touted as a beacon of hope for Asian elephant conservation, the collaborative effort in developing the vaccine included the involvement of the International Elephant Foundation (IEF), Colossal Biosciences, and the Houston Methodist Center for RNA Therapeutics. The progress points to potential national and international distribution, which could significantly reduce the mortality rate caused by EEHV, presently the leading cause of death for juvenile Asian elephants in North America and Europe.
