21-05-2025
New research reports New Mexico drug-resistant bacterial infection spread from humans to primates
This is a medical illustration of drug-resistant, Shigella bacteria, (Courtesy of Centers for Disease Control and Prevention; illustrated by Stephanie Rossow)
New Mexico researchers on Tuesday published findings in the journal Nature Communications that a strain of bacteria resistant to several common antibiotic treatments spread from humans to primates at the Albuquerque BioPark Zoo between May 2021 and November 2023.
Shigellosis is a highly infectious gastrointestinal infection caused by a type of bacteria called Shigella. New Mexico recorded more 202 cases during the outbreak, including more than half in people experiencing homelessness, while others included daycare workers and attending children.
Nearly 70% of people with the infection were hospitalized, and there was one death. Research published Tuesday found the infection spread into the zoo, causing six primate deaths.
The outbreak is the first to be caused by drug-resistant bacteria and was the largest in the state.
The study's researchers urge further surveillance due to the 'threat of antimicrobial resistant organisms to vulnerable human and [non-human primate] populations.'
The infection is passed through contact with the bacteria — found in feces —including contact with other surfaces; contaminated food or water; or person-to-person contact. Antibiotics are commonly prescribed to treat severe cases, but growing drug resistance is limiting treatment options.
Anti-microbial resistance is growing in the U.S. Shigella populations. In 2023, the Centers for Disease Control and Prevention warned that about 5% of Shigella infections resisted antibiotic treatments compared to 0% in 2015.
That figure included the New Mexico outbreak, from which researchers found that the bacterial infections were resistant to multiple drugs including the 'first line treatment option which led to treatment failures in human and [non-human primate] populations.'
Researchers studied the genetic makeup of the Shigella strain in the New Mexico outbreak, which included the 202 New Mexico cases, 15 out of state cases and four non-human primates, to help understand how the outbreak spread.
Shortly after human cases were identified in May of 2021, 15 primates at the zoo displayed shigellosis. Four primates — a gorilla and three siamangs, including a mother and her 2-month old baby — died of Shigella infection. Almost a year later in July 2022, a chimpanzee tested positive and also died.
The only surviving siamang was transferred to another zoo, but despite testing negative, infected others there with shigella, was transferred back and ultimately euthanized.
Researchers don't have an answer for how the infection spread from humans to primates in the zoo, hypothesizing it could have spread through objects or from houseflies as a vector. Further tests ruled out municipal water and zoo staff did not report Shigellosis-like illness.
'It may have been introduced, indirectly, when a zoo visitor threw a contaminated item into the enclosure,' researchers wrote. 'It may also have been introduced on cardboard tubes used as enrichment items, although this common zoo practice was discontinued as part of the initial response to the 2021 primate infections, and cannot explain the 2022 chimpanzee infection.'
The latest update in the outbreak was in September 2024, when the the New Mexico Department of Health reported four additional Shigella cases, mostly impacting people experiencing homelessness. The study's authors included researchers from the state Department of Health, the University of New Mexico, Los Alamos National Laboratory, New Mexico Institute of Mining and Technology and the City of Albuquerque.
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