Last week in Family Pets, Zoonoses & An Upcoming COCA Call, we briefly discussed a recent story of a man, and his dog, who had contracted plague in Colorado. While rare – the United States sees perhaps a dozen human cases each year.
But what made this case doubly unusual is that the man was diagnosed with pneumonic plague.
Bubonic Plague (Yersinia Pestis) is a bacterial infection transmitted by fleas, carried by infected rats. The infection generally sets up in the lymphatic system, resulting in the tell-tale buboes, or swollen lymph glands in the the groin, armpits, and neck.
In rare cases Pneumonic Plague may develop. Here the infected person develops a severe pneumonia, with coughing and hemoptysis (expectoration of blood), and may spread the disease from human-to-human.
Since plague is fairly easily treated with antibiotics, it isn’t much of a public health menace in the developed world. In areas where treatment isn’t readily available, however, mortality rates run 40%-60% and untreated pneumonic plague is almost always fatal.
Today, the Colorado Department of Public Health has announced that three contacts of the originally infected dog developed mild infections, but have recovered following antibiotic therapy.
It isn’t entirely clear from this release the type of plague infection (bubonic, septicemic, or pneumonic) that these contacts developed but a Denver Post story (Three more cases of plague identified in Colorado) indicates two developed the pneumonic version.
First the statement, then I’ll be back with just a bit more:
FOR IMMEDIATE RELEASE: July 18, 2014
Mark Salley, Communications Director
The Colorado Department of Public Health and Environment has identified three additional Colorado residents with plague, for a total of four cases. The investigation of the original case identified three individuals, each of whom had direct contact with the previously reported dog that had died of plague. They all had mild symptoms, were treated with appropriate antibiotics, recovered, and no longer are contagious. The initial patient remains hospitalized.
The dog likely was exposed to a prairie dog or rabbit with plague-infected fleas in eastern Adams County.
Tri-County Health Department officials, the Centers for Disease Control and Prevention and the Colorado Department of Public Health and Environment are continuing to work together to investigate these cases and prevent further illnesses. Although person-to-person transmission of plague is extremely rare, individuals who may have been exposed through close contact with the four cases have been identified, and have received antibiotic treatment or are being monitored for symptoms when indicated.
Plague is spread by fleas from rodents, most commonly prairie dogs. Flea samples recently collected from eastern Adams County tested positive for plague bacteria. Tri-County Health Department staff members have gone door-to-door in the area with information about plague and to assess prairie dog populations. People and pets walking in open spaces and trails should avoid contact with prairie dogs, rabbits and other rodents.
Contact your physician if you develop a high fever and other plague symptoms following a fleabite or direct contact with dead rodents, or exposure to a sick cat or dog that may have had contact with plague-infected rodents. Symptoms of plague include a sudden onset of high fever, muscle pain, nausea and vomiting, or a general feeling of being ill. Individuals with pneumonic plague (the lung form) develop fever, headache, weakness, shortness of breath, chest pain and coughing, which can lead to respiratory failure. Pneumonic plague is the most serious form of the disease and is the only form of plague that can be spread from person to person (by infectious droplets from coughing). Although human cases occur infrequently, plague can be severe and potentially life-threatening if not detected and quickly treated with common antibiotics.
Dr. Jennifer House, public health veterinarian at the Colorado Department of Public Health and Environment, encourages people take the following precautions to prevent plague exposure:
- Do not directly handle any dead rodents, including prairie dogs, rabbits, squirrels, mice and rats.
- Keep pets away from wildlife, especially dead rodents.
- Don’t let dogs or cats hunt prairie dogs or other rodents.
- Don’t allow pets to roam freely.
- Treat pets for fleas according to a veterinarian's advice.
- Do not feed prairie dogs or other rodents. This attracts them to your property, brings them in close contact with other rodents and increases the risk of disease transmission.
- Be aware of rodent populations in your area, and report sudden die-offs or multiple dead animals to your local health department.
Plague often is identified when there is an unusual die-off of prairie dogs in an area. When an infected animal dies, the fleas leave the carcass to find another host, thus spreading the disease. Most human plague cases occur when humans are bitten by infected fleas. Less commonly, people are infected by direct contact with blood or tissues from an infected animal or from pets (primarily cats) that become infected and transmit the disease. Since 1957, Colorado has identified 60 cases of human plague, nine (15 percent) of which were fatal.
Additional information on plague can be found at: http://www.cdc.gov/plague
Contact CO-HELP (Colorado Health Education Line for the Public) at 303-389-1687, or outside the metro area call 1-877-462-2911 for more information or to report a dead prairie dog.
The last major urban outbreak of plague in the United States occurred in 1924-25 in Los Angeles. Since then, only scattered cases have been reported, with about 7-15 cases each year in the U.S..
According to the CDC: Between 1,000 and 2,000 cases each year are reported to the World Health Organization(WHO), though the true number is likely much higher. The last really big plague outbreak was in India nearly 20 years ago, as summarized by the WHO, where a total of 5150 suspected pneumonic or bubonic plague cases and 53 deaths were reported from eight states of India, primarily in the south-central and southwestern regions.
Although there is no vaccine available, with the advent of effective antibiotics, large scale outbreaks of plague are increasingly rare. Still, the risk of infection is not zero, and so the CDC has some advice on how to avoid this illness by way of this 2-page PDF file.