Infected monkeys at Michigan research lab threaten health and science


June 21, 2023

A macaque rests on a tree in Dharmsala, India, Friday, April 10, 2020. (AP Photo/Ashwini Bhatia)AP

Monkeys infected with tuberculosis were imported into Michigan earlier this year, sparking a disease investigation by state officials and raising questions from animal rights advocates over national testing shortfalls.

In addition to the monkeys that tested positive for the bacterial infection TB at a West Michigan research facility, there were also two individuals who tested positive, according to the state’s Department of Health and Human Services. It is not clear if the infections were related, however, as only 2% of humans at the lab tested positive and typically about 4% of people, some without knowing it, have TB in the general population.

TB is a disease caused by bacteria that can lay dormant in some individuals, and cause serious illness in others. It’s a zoonotic disease, meaning it can be transmitted from animal to human, sometimes checked by the immune system for years before causing health problems.

The illness not only poses a potential public health threat, it threatens biomedical research, explained Lisa Jones-Engel, a primate scientist and senior advisor for the group People for the Ethical Treatment of Animals (PETA). An undiagnosed TB infection can skew research data and mislead scientists on the effects of experimental therapies.

“It’s scary when you have something that is going to be so deadly to the animals, is a zoonotic threat, can and certainly does represent a scientific threat, and when these animals are co-infected and battling TB infection, anything else they’re infected with are more likely to be shed at that point because the animal is sick, its immune system is distracted,” Jones-Engel said.

“So it’s a mess.”

The Michigan Department of Agriculture and Rural Development (MDARD) was alerted early this year of the TB infections in monkeys. At least three macaques wild caught in Mauritius, an Indian Ocean island nation, and imported to Florida and then Michigan were infected, according to an MDARD report obtained by PETA through a Freedom of Information request.

Dr. Jennifer Calogero, assistant state veterinarian for Michigan, said the owner euthanized the infected monkeys, and additional exposed primates were quarantined before being cleared. The state’s investigation has since concluded.

The humans who were positive for TB were not experiencing symptoms when tested and were referred for treatment, according to MDHHS. Health officials said it’s likely that prompt identification and quarantining of the symptomatic animals may have prevented the potential for transmission to both people and other animals.

According to PETA, the Michigan lab with the TB outbreak was Northern Biomedical Research (NBR) in Norton Shores, which reported having 483 non-human primates in 2020. The state declined to identify the lab, citing a privacy law, and a spokesperson for the lab declined to respond to MLive’s questions.

“We do not comment on specific business activities at our facility to protect client confidentiality and employee privacy,” reads a company statement. “As a general matter, exposure to TB is a health concern in the federally mandated research and development of critical human treatments and cures.”

NBR said it requires negative TB tests as a regular precaution to protect employees and non-human primates from disease. It also proactively tests for many zoonotic diseases in its research models to identify and treat any latent infections, and requires staff to use personal protective equipment.

What concerns Jones-Engel most is infected monkeys were cleared from U.S. Centers for Disease Control and Prevention quarantine prior to arriving in Michigan. She said available skin and blood testing can be inadequate in detecting latent TB, allowing for infections to go undetected.

“Those monkeys should never have left CDC quarantine; they should never have been brought into this country with TB,” she said.

“This goes back to how poor the tuberculin tests really are for detecting in monkeys. Those animals in that room who were there with the three original positive animals, all five of those could go through their testing and come out clean and go back on their experimental study and then a month or two months later when the animals are more fully immunosuppressed, they could pop up positive.”

In a 2021 paper, JoAnn Yee from the University of California National Primate Research Center wrote that while the CDC continues to require a series of negative tuberculin skin test results for monkeys to clear import quarantine, “there are multiple documented cases of animals successfully clearing quarantine and then later developing clinical disease after shipment to other facilities, often after having been enrolled in a research study.”

Monkeys can be imported to the U.S. for three reasons: education, exhibition, and science. The leading exporters of monkeys to the U.S. include Cambodia and Mauritius.

In 2021, there were more than 30,000 monkeys imported into the U.S. Of those shipments, six had monkeys with positive tuberculin skin tests for TB – the most in any year since 2009 – resulting in 24 monkeys being euthanized over suspicion of TB, according to records obtained by PETA through a Freedom of Information Act request and shared with MLive.

TB can attack the lungs, kidney, spine and brain. It’s spread through the air and once it settles in a person’s lungs it can move through the blood to other parts of the body.

Some people who are infected have a latent form of TB, meaning they don’t get sick or exhibit any noticeable symptoms. They can’t spread the bacteria, according to the CDC, and are likely unaware they’ve been infected.

Others can develop symptoms including a bad cough, chest pain, weakness or fatigue, weight loss, lack of appetite, chills, and fever. If left untreated, the disease can lead to organ failure and become deadly.

Latent TB can develop into TB disease as well. That development is more common in people with weakened immune systems from conditions like HIV, kidney disease, diabetes, or some types of cancer.

Last year, Michigan reported 120 positive cases of TB in humans, or about 1.2 cases per 100,000 people. That marked a 12% decrease from 2021 and was on-par with the state’s five-year average.

TB disease can be treated through a combination of drugs taken for 6 to 12 months. There’s a vaccine known as BCG, but it’s not among the typically recommended shots in the U.S., according to the CDC.

Jones-Engel and her PETA colleagues want to see the CDC suspend importation of primates for use in labs and/or revise its requirements for screening imported primates.

A recent audit by the Government Accounting Office, mandated by U.S. Congress, determined the CDC’s current approach in regulating certain imported wildlife species may not be sufficient to prevent outbreaks.

“If CDC comprehensively assessed disease risks to inform decisions about regulating imported wildlife, it could help prevent the introduction of zoonotic diseases into the U.S,” reads the report.