The oriental rat flea (Xenopsylla cheopis) shown here is the most important vector of plague historically. However, in New Mexico, the rock squirrel flea (Oropsylla montana) is the most important plague vector for humans. Photo by Ken Walker, Museum Victoria, Melbourne Australia, bugwood.org.

The New Mexico Department of Health recently announced a laboratory-confirmed case of plague in a 73-year-old woman from Santa Fe County. The case was confirmed at the Department of Health’s Scientific Laboratory Division. This is the fourth human case of plague in New Mexico this year and the second in Santa Fe County. The woman was hospitalized and is back home recovering. The other cases in the state occurred in a 52-year-old woman from Santa Fe County, who died from the illness, and in a 65-year-old man and a 59-year-old woman, both from Bernalillo County, who have recovered.

“This is the fourth case of plague in New Mexico with the patient presenting clinical signs of septicemic plague,” said Department of Health Secretary Retta Ward, MPH. “Though septicemic plague is less common and harder to recognize than the more common form of bubonic plague, health care providers need to consider plague in their diagnosis when the patient has a fever of unknown origin and when the patient is from plague endemic areas of the state.”

Septicemic plague accounts for approximately 20-25 percent of New Mexico cases. No detectable swollen lymph node (bubo) is found.

Plague is a potentially fatal illness in people that occurs in many parts of New Mexico. It is caused by a bacteria found in rodents, especially ground squirrels, rabbits and pack rats. Most human cases of plague are acquired through the bite of infected fleas. Dogs and cats are also susceptible to plague and are infected either through bites of infected fleas or by eating an animal that has died from the disease.

“Several of our plague cases this year have most likely been exposed to plague-infected rodent fleas brought into the home and bedroom by dogs and cats that are allowed to roam and hunt and aren’t treated with a flea-control product,” said Paul Ettestad, state public health veterinarian with the Department of Health.

Symptoms of plague in people usually develop two to eight days after exposure. Plague symptoms are sudden fever, chills, headaches, and swelling of the lymph nodes in the neck, armpit, or groin areas. As previously stated, in some cases, infection may progress without swollen lymph nodes making it harder to diagnose.

In addition to the four human cases, there have been eight cases of plague this year in dogs and cats, including pets from Bernalillo, Santa Fe, and Torrance counties.

To reduce the risk of plague, the New Mexico Department of Health recommends the following:

• Use insect repellent on exposed skin and clothing when you go outdoors. The Centers for Disease Control and Prevention recommends repellents containing DEET, Picaridin, oil of lemon eucalyptus, or IR3535 for use on skin, and permethrin for use on clothing. Always follow label directions when using insect repellents.

• Keep your pets from roaming and hunting.

• Talk to your veterinarian about using an appropriate flea and tick control product on your pets as not all products are safe for cats, dogs, or your children.

• Clean up areas near the house where rodents could live, such as woodpiles, brush piles, junk and abandoned vehicles.

• Don’t allow children or others to handle sick or dead wildlife.

• Sick pets should be examined promptly by a veterinarian.

• See your health care provider immediately about any unexplained illness involving a sudden and severe fever.

• Put hay, wood, and compost piles as far as possible from your home.

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– Plague in New Mexico