Washington

A study of smallpox in monkeys has been suspended by the Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia, because of concerns about animal treatment.

Peter Jahrling has clashed with vets over when animals in his study should receive painkillers.

The study, which began last year, is led by virologist Peter Jahrling of the US Army Medical Research Institute of Infectious Diseases in Fort Detrick, Maryland. Jahrling infected cynomolgus macaques with two strains of smallpox virus in an attempt to develop a monkey model for testing new therapies for the disease. But last week, the CDC suspended the study after Jahrling and veterinarians clashed over when the monkeys should receive painkillers.

The Food and Drug Administration (FDA) ruled in May that animal studies can be used to obtain regulatory approval for drugs (such as smallpox therapies) that cannot ethically be tested on humans. Jahrling says he expects the FDA will require experimental treatments to be given without painkillers, and doesn't want to press on with a study that might be ineligible for approval.

A CDC spokesperson says that the institution's animal-care committee had mandated that all the animals in the study should receive painkillers at a certain point, but “word had not gotten to all the vets involved”. The spokesperson says that the agency hopes to resolve the issue at a meeting with institute researchers on 16 July.