At least 116 people and 46 animals in Colorado were potentially exposed to Black Death after veterinarians struggled to diagnose a severely ill dog in 201
The unusual case prompted health experts to release an equally unusual – and perhaps surprising – warning. That is, that dogs in the United States can contract the deadly bacterial infection at any time of the year, and the signs can be difficult to spot.
"[P] the neumonic plague, although rare, should be considered in dogs that have fever and respiratory signs with potential exposure in endemic areas, regardless of the season and the lobar distribution [lung]", the experts of the Colorado health. They published the details of the case and their warning this week in the journal Emerging Infectious Diseases .
The plague is endemic in areas of the western United States, which means that it is constantly circulating. Although he is best known for causing the catastrophic Black Death pandemic in Europe during the fourteenth century, he arrived in the United States around 1900 on mouse-infested steamships. Since then it has spread, and quietly lurked, in rural rodent populations, including squirrels, wooden rats, ground squirrels, prairie dogs, chipmunks, mice, voles and rabbits. Infected populations tend to appear in parts of Arizona, California, Colorado, Oregon, Nevada and New Mexico. The Centers for Disease Control and Prevention report that in the last few decades an average of seven human cases documented every year has occurred, with an interval from one to 17 cases.
The bacterium behind the deadly disease is Yersinia pestis which spreads through flea bites and contact with infected people and animals. Once it finds its way into a victim, the infection can manifest itself in several ways. The three main ways are bubonic (infection that typically starts from the skin after a flea bite and spreads to the lymphatic system, causing swollen lymph nodes, called bubbons), septicemic (blood infection) and pulmonary (infection in the lungs, which can spread from person to person through droplets carried by the air).
In dogs, the plague is rare but usually occurs as bubonic or septicemic, resulting from a bite of an infected flea. And, as the report's authors note, plague cases in the United States tend to come up when fleas are more active, generally between April and October. But this is not always the case, as the story of the poor puppy in Colorado shows.
In December 2017, a mixed breed dog of three years showed up at the veterinary office with lethargy and fever. Four days earlier, the dog's human noticed that the dog had smelled a dead prairie dog. The vet began antibiotic treatment, but the dog's condition deteriorated rapidly. The following day, the dog started coughing up blood, and the vet reported the case to the Colorado State University Veterinary Hospital.
Despite contact with the dead prairie dog, the vets did not suspect the plague in the beginning because, well, it is rare, and it was December. Furthermore, the clinical images of the dog's diseased lungs did not match the usual pattern of a sore, which usually affects both lungs. Instead, only a part of a lung was affected, and it seemed more as if the dog had inhaled a foreign body, a more common problem than sheep. To get rid of the alleged source of infection, veterinarians performed a pulmonary lobectomy, removing the heavily damaged part of the dog's lung.
With the lung tissue removed, veterinarians tried for several days to cultivate all the possible bacteria that caused the infection. But this has produced confusing results, indicating a bacterium related to Y. pestis that would not cause the symptoms seen in the dog. They then turned to PCR (polymerase chain reaction), a method for taking and making copies of specific DNA segments, which can help identify organisms. But at that point, the dog's condition continued to deteriorate and the vets had to kill the dog.
Following the PCR PCR protocol to search for Y. pestis veterinarians found deadly bacteria. Realizing that they had the plague on their hands, the veterinarians reflected the dog's long hospital stay to evaluate the exposures. Based on staff surveys and dog positions, they concluded that at least 116 people and 46 animals in chambers were potentially exposed. Humans at risk spoke to their doctors to see if they should take antibiotics as a precaution. All co-housed animals have prophylactic antibiotics.
As far as veterinarians knew, no one fell ill with the plague because of their exposures. Again, they report that the hospital is updating its protocols to better identify the plague and prevent it from spreading to personnel and patients.
Emerging infectious diseases 2018. DOI: 10.3201 / eid2504.181195 (Information on DOI).