Study suggests treating animals to fight resurgent tropical disease

A University of Washington (UW) study suggests that monitoring, and potentially treating, the monkeys that co-exist with humans in affected parts of the world may be part of the World Health Organization (WHO) strategy to eradicate a once-rampant tropical disease.

Yaws, an infectious disease that stems from a bacterium, Treponema pallidum, and causes disfiguring skin lesions and bone destruction, has been found in certain primates in Africa and Asia. Treatable with a one-time dose of penicillin or, as part of the renewed eradication effort, the antibiotic azithromycin, the disease has experienced a significant resurgence in the past two decades.

Prone to spread in areas that are overcrowded, under-resourced or have inadequate sanitation, yaws afflicts mostly children. It had a massive reach, affecting more people than malaria in some parts of the world: from 1952 to 1964, the WHO and the United Nations Children's Fund (UNICEF) treated 50 million cases and contacts in 46 countries. But officials scaled back efforts when it appeared to be contained, only to see it gradually re-emerge at the end of the 1970s.

Today, aiming for yaws' global eradication by 2020, the WHO estimates tens of thousands of cases in a dozen countries in Africa and Asia.

In a study published online in Emerging Infectious Diseases, a journal of the U.S. Centers for Disease Control and Prevention (CDC), UW researchers and colleagues examined macaques in South and Southeast Asia, where the monkeys live in the wild, temples and villages, or are kept as pets. While they could not identify how a particular animal became infected, treponemal infections are known to be transmitted by contact with the skin lesion of an infected individual, so a pet macaque could potentially pick up the bacteria, said Lisa Jones-Engel, a UW research assistant professor of anthropology who led the study.

It's not yet clear whether the infection can pass from human to animal and vice versa, said Sheila Lukehart, a UW professor of medicine and global health who co-authored the study, and the prevalence of the animals in daily life in many countries makes them an important factor in how to approach eradication efforts.

Involving their colleagues from universities in Asia, Europe and Canada, the UW researchers examined blood samples of more than 700 macaques in the study, and fewer than 2 percent were tested positive for the bacteria, mostly on the island of Sulawesi in Indonesia, where a yaws outbreak was active at the time samples were collected.

"Although yaws is endemic in a number of regions that we tested, infected monkeys were seen only in a region that had experienced a recent upsurge in reported yaws cases. So if you go through and treat only the villagers, then your eradication effort may be compromised," Jones-Engel was quoted as saying in a news release from UW. "If you go into a village where you know yaws is prevalent in the human population, and animals are part of that population, then those animals may need to be targeted for treatment."

Treating animals for a disease that can spread to humans is not unprecedented: the rabies vaccine routinely administered to pets in the developed world, for example, prevents the infection in animals, which in turn protects people. Endit