The Colorado Department of Public Health and Environment revealed last week that a man whose dog has died of plague was found to have pneumonic plague, a rare but infectious bacterial disease that is highly fatal when left untreated.
Pneumonic plague is one of the three forms of plague, which is caused by the Yersinia pestis bacterium. Individuals who contract the disease, which is marked by severe infection of the lungs and manifests itself with symptoms that include fever, rapidly developing pneumonia and coughing of blood, require immediate treatment to reduce the risks of death.
On July 18, state health officials said that three more people have been diagnosed with the human plague, two of whom had pneumonic plague and one who had a milder form of the disease. All three cases are believed to be linked with the dog owned by the first patient, who now remains hospitalized but whose current condition was not revealed by health officials. The three other infected individuals have come in direct contact with the infected dog.
Jennifer House, public health veterinarian at the Colorado Department of Public Health and Environment, said that the dog may have been infected after exposure to plague-ridden fleas from a rabbit or prairie dog. The flea samples that were collected from eastern Adams County were found to be positive for the plague bacteria.
Plague is transmitted from rodent to humans or animals by fleas that become infected by feeding on prairie dogs, mice, squirrels and other rodents that have been infected with the bacteria Yersinia pestis, also called pneumonic plague. The most serious form of the disease can be contracted when a person inhales respiratory droplets from an infected person through coughing and sneezing.
"Contact your physician if you develop a high fever and other plague symptoms following a flea bite or direct contact with dead rodents, or exposure to a sick cat or dog that may have had contact with plague-infected rodents," the Colorado Department of Public Health and Environment advised.
Health officials said that the three individuals who were newly-found to be infected had mild symptoms and have fully recovered after they were treated with antibiotics. They are also no longer contagious.
State health officials also said that individuals who were possibly exposed through close contact with the four patients have already been identified, given antibiotic treatment and monitored for symptoms. It also said that it is working with Tri-County Health Department officials and the Centers for Disease Control and Prevention in investigating the cases and adopting measures to prevent more incidents of the disease.
Pneumonic plague is one of three forms of plague and, after initial infection of a human via fleas from an infected animal, it can be spread from human to human. The Centers for Disease Control and Prevention notes that it requires agressive treament: "Early treatment of pneumonic plague is essential. To reduce the chance of death, antibiotics must be given within 24 hours of first symptoms. Streptomycin, gentamicin, the tetracyclines, and chloramphenicol are all effective against pneumonic plague. Antibiotic treatment for 7 days will protect people who have had direct, close contact with infected patients. Wearing a close-fitting surgical mask also protects against infection."