In the 1870s, Puerto Rico’s sugarcane plantation owners faced rats destroying their crops, then the backbone of the local economy, and imported the small Indian mongoose from Asia as a biological control. The plan failed because of differing habits: the U.S. Centers for Disease Control and Prevention (CDC) explained that mongooses are active mainly by day, while the rats in the cane fields were mostly nocturnal.
With no natural predators and abundant resources, the mongooses multiplied quickly and spread across the island as an invasive species. The CDC report says they also began eating birds, reptiles, amphibians and other small native species, damaging native fauna. The same thing happened on other Caribbean islands.
There was a public health consequence as well. According to The Wildlife Society, authorities confirmed a major rabies outbreak among Puerto Rico’s mongooses in 1950, and the animal became the island’s main land-based rabies reservoir. CDC records put mongoose-linked cases at about 75% of animal rabies cases, more than 70% of positive diagnoses in local wildlife.
Studies in El Yunque and Cabo Rojo found neutralizing rabies antibodies in about 39% of animals tested; other areas showed about 17%. According to The Times of India, a 54-year-old man in southeastern Puerto Rico was bitten by a mongoose while working in a chicken coop and did not seek preventive treatment. Weeks later he developed fever, tingling, difficulty swallowing and other symptoms, and he died.
Tests confirmed rabies of the Caribbean mongoose variant, the first documented death in Puerto Rico attributed to a mongoose bite and the first such case in the United States or its territories.