Dear Dr. Pierce,
Every now and then there are news articles about bubonic plague being detected in the local rodent population. What exactly is plague and how do I protect my pets and my family from it?
Any mention of the plague is always good for stirring up dark and dramatic fears of some monstrous, unstoppable disease sweeping across the continent and wiping out a third of the population in a matter of months. The truth of the matter is that in this era of modern medicine the plague, although potentially very serious, is actually often fairly simply treated with ordinary antibiotics. Plague is a natural part of the ecosystem in the western United States and we all can learn to live with it without panic and terror.
The disease we call plague is caused by a bacterium, known by people who like to use two long words when one short one will do , as Yersenia Pestis. This bacterium lives quietly in rodents in low levels, usually minding its own business and not causing much of a disturbance. Enter the flea. Fleas pick up the Yersenia Pestis when they bite the rodents and carry it along in their bodies. When a flea bites a new victim it may leave behind under the skin a little souvenir package of plague bacteria as a bonus to the red itchy spot they usually give. The wily Yersenia Pestis have developed a way of encapsulating themselves so that the immune system of the new victim does not destroy it, and instead transports it to a lymph node where it makes itself at home, multiplying and causing a swollen, painful lump or two, usually on the neck just under the jaw.
The main way that pets could expose your family to the plague is by bringing home infected fleas and giving them to you. Don’t say the cat never got you anything. We are very fortunate to live in a dry, high altitude climate where fleas don’t thrive just anywhere, but fleas do like rodent burrows with their relatively higher humidity and ready supply of warm bodies to feed on. In general fleas stick with a good deal when they find it, so as long as the rodent is warm they are satisfied to stay on an all rodent diet. When the cat kills a rodent , however, its body temperature starts dropping rapidly and this is the cue for fleas to find another host, usually the closest mammal, the cat. Dogs can create the same effect by rolling in dead carcasses or otherwise being in areas where recently homeless fleas are looking for a new host. Good flea prevention for your pets, (and by that I mean the types of products you can get from your veterinarian, not those silly, toxic, and mostly useless flea collars from days of yore) should keep unwanted piggy backers from coming in to your family. This is especially helpful if you live near a prarie dog colony, as they are a common reservoir for Yersenia Pestis and potentially contaminated fleas.
At this point dog owners can yawn and go do something else. Dogs are naturally very resistant to the plague organism and rarely develop significant disease themselves if bitten by infected fleas. Cat owners, however, should pay close attention. Cats are particularly susceptible to plague and can become very ill very quickly. A cat with plague is usually running a high fever and is flat as a rug. You will not be in doubt that there is something seriously wrong going on, and if you notice the telltale swelling under the jaw you need to pack up the cat and get her in for treatment immediately. With the most common forms of plague in cats the contagious potential from cats to people is fairly low, but in rare cases cats can develop lung involvement that can be easily coughed on to people which in turn could cause severe and possibly fatal respiratory infection in the recipient of the cough. Limiting your exposure to plague infected cats is usually wise, but of course you don’t know the cat has plague until after the visit to the vet. If your animal is diagnosed with plague you should talk with your doctor about possibly starting some prophylactic antibiotics for those who have had contact with the cat.
And so with good flea control, limits on pet’s exposure to rodent populations and awareness of the clinical signs of plague we can usually successfully thwart the dreaded disease that wiped out much of the European continent during the dark ages. We live in a region where plague is here to stay, but with a little understanding of the situation our families and our pets can remain well protected.
