Morgan Island, often called “Monkey Island,” is a unique landmass off the coast of South Carolina hosting a large, non-native colony of rhesus macaques (Macaca mulatta). Situated in Beaufort County, the island is uninhabited by humans and serves as a controlled, free-ranging environment for these primates. The colony’s management is tied directly to biomedical research, creating specific public health considerations. The primary concern is the potential for zoonotic disease transmission to humans, necessitating strict quarantine and restricted access.
The History of the Morgan Island Colony
The rhesus macaque colony was established on Morgan Island due to a public health concern in the Caribbean. The monkeys originally resided at the Caribbean Primate Research Center in Puerto Rico. Incidents of free-ranging monkeys escaping and interacting with the local population, along with concerns over a viral infection, prompted relocation. Between 1979 and 1980, over 1,400 macaques were moved to the secluded Morgan Island. This strategic move created a quarantined, self-sustaining breeding colony far from human population centers.
The colony is owned by the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health (NIH). It supplies primates for biomedical research projects across the United States, including studies on diseases like HIV and Ebola. The population has flourished, growing to an estimated 3,500 to 4,000 individuals, making it one of the largest free-ranging rhesus macaque colonies globally.
Identifying the Primary Health Concern
The disease that prompted the initial relocation and remains the most significant health concern is the Herpes B Virus, scientifically known as Macacine herpesvirus 1. This virus is a naturally occurring and highly prevalent agent in Old World macaques, including the rhesus species. It belongs to the Simplexvirus genus and is related to the herpes simplex viruses found in humans.
For the rhesus macaque, the virus is generally benign, causing mild symptoms or remaining asymptomatic. Infected monkeys may develop minor oral or genital lesions, but the infection is typically latent. The virus is shed intermittently from these sites, which is the primary mechanism of transmission to other macaques and humans. A significant percentage of the adult macaque population is seropositive, confirming the virus as an endemic agent within the colony. The primary health concern is the risk the virus poses to any person who comes into contact with the animals.
Implications for the Monkeys and Human Safety
The presence of Herpes B Virus creates a serious, though rare, risk of zoonotic transmission to humans. Unlike in macaques, human infection can lead to rapidly ascending encephalomyelitis—a severe inflammation of the brain and spinal cord. If untreated, human B virus infection has a high fatality rate, historically ranging between 70% and 80%. Survivors often suffer severe neurological damage.
Transmission occurs through direct contact with the macaque’s bodily fluids or tissues, typically via bites, scratches, or contact with the eyes, nose, or mouth. It can also be transmitted through percutaneous inoculation, such as a needle-stick injury. Prompt diagnosis and immediate antiviral therapy are necessary for human survival and to limit central nervous system damage following exposure.
To mitigate this severe risk, a strict safety protocol is enforced around Morgan Island. Unauthorized access is prohibited, with the perimeter clearly marked to prevent public exposure. Personnel who interact with the animals, such as veterinary staff and researchers, follow rigorous biosafety procedures, including the use of personal protective equipment and post-exposure treatment guidelines.