Likely Human-to-Human Plague Transmission Reported

Ricki Lewis, PhD

May 06, 2015

A man hospitalized in Colorado in July 2014 contracted pneumonic plague from his dog, as did three other people who had contact with either the man or his dog, investigators report in the April 30 issue of the Morbidity and Mortality Weekly Report.

Janine K. Runfola, MS, from the Tri-County Health Department in Colorado, and colleagues report that "patient A" presented on June 28, 2014, with fever and cough 4 days after his pit bull began coughing up bloody mucus and developed fever, jaw rigidity, and right forelimb ataxia. The man had been in close contact with the dog as it was euthanized the day after it developed symptoms.

Patient A was initially incorrectly diagnosed with Pseudomonas luteola infection through an automated testing system. When his condition continued to deteriorate his specimens were sent to the Colorado Department of Public Health and Environment for retesting and he was correctly diagnosed with Yersinia pestis on May 8, 10 days after initially falling ill. The error delayed accurate diagnosis by a week, exposing more people, the researchers write.

Three other people who had been in contact with the dog developed fever and respiratory symptoms: patients B and C worked at the veterinary clinic, and patient D had helped move the body of the dog, coming in contact at one point with its blood. She also had close extended contact with patient A when he was symptomatic, including hemoptysis. The incubation period between her exposure to patient A and her symptom onset suggests human-to-human transmission, the first seen in the United States since 1924.

All the patients had evidence of Y pestis infection. Patient C was the only one without radiographic evidence of pneumonia, possibly because she began taking oral doxycycline the day after the dog visited the clinic.

After treatment with antibiotics and a 23-day hospitalization, patient A recovered. The other patients were treated and recovered as well.

The investigators contacted 114 people who had had close contact with the dog or the patients and recommended antimicrobial prophylaxis for 88 of them.

This is the first case reported in the United States of pneumonic plague contracted from a pet dog. "Although symptomatic plague in dogs is rare, veterinarians should consider the possibility of Y. pestis infection in ill dogs with wildlife exposure in areas where plague is endemic," the researchers write.

The investigators caution that human plague is still a public health concern in western states where Y pestis lives in wild rodents, such as prairie dogs, and is transmitted by fleas or through contact with infected mammals. In endemic areas, rodent die-offs and suspected human plague cases should be reported immediately to public health officials, the researchers advise.

The researchers have disclosed no relevant financial relationships.

Morb Mortal Wkly Rep. 2015;64:429-433.


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