A dog potentially exposed more than 100 people to the Black Death in Colorado

At least 116 people and 46 Colorado animals were potentially exposed to the Black Death after veterinarians had difficulty diagnosing a critically ill dog in 2017.

The unusual case prompted health experts to issue an equally unusual – and perhaps surprising – warning. That is, dogs in the United States can contract the deadly bacterial infection at any time of the year and that signs can be difficult to detect.

"[P]Neutron plague, although rare, should be considered in dogs with fever and respiratory signs that may be exposed in areas where the disease is endemic, irrespective of season and lobar. [lung] distribution, "concluded the Colorado health experts. They published the details of the case and their warning this week in the review Emerging infectious diseases.

Plague is endemic in the western parts of the United States, which means that it circulates continuously. Although best known for provoking the catastrophic Black Death in Europe in the 14th century, he arrived in the United States around 1900 on steam-infested steamships. Since then, it has spread to rural rodent populations, including rock squirrels, wood 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 recent decades, an average of seven human cases have been recorded each year, ranging from one to 17 cases.

The bacteria behind the deadly disease is Yersinia pestis, which is transmitted by flea bites and by contact with infectious individuals and animals. The infection can manifest itself in different ways once it has entered the life of the victim. The three main pathways are bubonic (infection usually begins with the skin after a flea bite and spreads to the lymphatic system, causing swollen lymph nodes, called buboes), septicemia (infection of the blood) and pneumonia (infection of the lungs, which may occur spread). from person to person via airborne droplets).

In dogs, plague is rare but usually presents as bubonic or sepsis, resulting in a bite of an infected flea. And, as the authors of the report note, plague cases in the United States tend to occur when fleas are most active, usually between April and October. But that's not always the case, as the story of the poor Colorado puppy shows.

Special plague

In December 2017, a three year old mixed breed dog presented to a veterinarian suffering from lethargy and fever. Four days earlier, the dog's human had noticed that the dog was sniffing a dead prairie dog. The vet started antibiotic treatment, but the condition of the dog quickly worsened. The next day, the dog began to spit blood and the vet sent the case back to the Colorado State University veterinary teaching hospital.

Despite the contact with the dead prairie dog, veterinarians did not suspect the plague at first, because it is rare, it is in December. In addition, the clinical images of the dog's diseased lungs did not correspond to the usual pattern of plague infection, which usually affects both lungs. Instead, only part of the lung was affected, and it seemed more than the dog had inhaled a foreign body, a more common dog problem. To get rid of the suspected source of infection, veterinarians performed a pulmonary lobectomy, removing the severely damaged part of the dog's lungs.

With the lung tissue removed, the veterinarians tried for several days to develop any bacteria that could cause the infection. But, this gave confused results, indicating a bacterium related to Y. pestis this would not cause the symptoms observed in the dog. They then turned to PCR (Polymerase Chain Reaction), a method of selecting and copying specific DNA segments, which can help identify organisms. But by that time, the condition of the dog had continued to worsen and the vets had to slaughter it.

By following the CDC PCR protocol to search Y. pestisveterinarians have found the deadly bacteria. Realizing that they had the sore on their hands, the vets traced the dog's several days stay at the hospital to evaluate the exposures. Based on surveys of staff and location of the dog, they concluded that at least 116 staff members and 46 co-housed animals were potentially exposed. Humans at risk talked to their doctors about whether they should take antibiotics as a precaution. All co-housed animals received prophylactic antibiotics.

As far as veterinarians can judge, no one has fallen ill from the plague because of their exposure. Nevertheless, they report that the hospital is updating its protocols to better identify the plague and prevent it from spreading to staff and patients.

Emerging infectious diseases, 2018. DOI: 10.3201 / eid2504.181195 (About DOIs).