Plague in Dogs

Plague is a serious disease that may spread from dogs to humans. Many dogs do not exhibit clinical signs of the condition, but if your dog is behaving strangely, and if you know you live in an area where plague is endemic, visit the veterinarian immediately. Measures will need to be taken as soon as possible to prevent transmission of the disease.

Dogs that contract plague are less likely to develop clinical illness and are often asymptomatic. If they do show clinical signs of the disease, these will be nonspecific and may include:

• Lethargy
• Fever
• Loss of appetite
• Swollen lymph nodes

Types

There are three forms of plague, any of which may affect your dog.

• Bubonic plague - The most common form of plague. It affects the lymph glands and exhibits as swollen lymph nodes.
• Pneumonic plague - Occurs when Y pestis infects the lungs, which typically leads to pneumonia and which is highly contagious.
• Septicemic plague - Blood infection in which the bacteria multiply in the blood.

The bacteria Yersinia pestis is the direct cause of the plague, which is commonly found in rodents (rats, mice, squirrels, hamsters) and in the fleas that feed on them. When a dog comes into touch with an infected rodent’s saliva, feces, or tissue, he becomes exposed to Y pestis. A dog may also contract the disease if bitten by an infected flea. Dogs that live in regions where Y pestis is endemic, such as in the rural west of the United States, are at higher risk for plague. In these areas, it is recommended that you keep your dog indoors or on a leash when outside.

Because the symptoms for plague are nonspecific, the veterinarian may not suspect plague immediately. Provide the veterinarian with a complete history during the initial examination, including the onset and extent of any clinical signs you observed. The veterinarian will perform a meticulous physical examination and conduct blood tests and urinalysis to eliminate other possible conditions as a cause for your dog’s symptoms.

Plague is typically diagnosed by detecting Y pestis in your dog’s blood or tissue. Samples may be obtained through a lymph node aspirate, whole blood test, or a swab of a draining lesion. These cultures are most effective if they are taken before any antibiotics are administered, though tests should still be conducted even if your dog has already been given medication. By identifying the specific organism, the veterinarian is better able to prescribe appropriate treatment. Samples will be sent to an associated laboratory for testing due to the risk of animal-to-human transmission.

Treatment is typically started before a definitive diagnosis is made, as the disease can progress very quickly. The veterinarian will administer different antibiotics depending on the extent of your dog’s illness. Possible drugs that may be prescribed include:

• Streptomycin
• Gentamicin
• Doxycycline
• Tetracycline
• Chloramphenicol

Because there is a risk that the plague may transfer from your dog to you, your dog will need to be hospitalized during the infectious period if the veterinarian suspects that he has the plague. The incubation period for plague in dogs ranges from one day to one week. Antibiotics will most likely be injected, though once your dog shows signs of clinical improvement, the veterinarian may recommend administering medication orally.

Plague is a zoonotic disease, and although dog-to-human transmission is rare, it is still possible. This is why it is vital that you limit contact with your dog during the infectious period. Once the plague diagnosis has been confirmed, the veterinarian will keep your dog hospitalized until your dog has recovered sufficiently to reduce the risk of transmission.

If you live in an area in which Y pestis is endemic, make sure that you apply flea control medication regularly and that you not allow your dog to roam freely, as otherwise your dog may be reinfected. Limit your dog from coming into contact with wild rodents or their burrows, and contact your local public health officials immediately if you suspect that your dog may have contracted the plague.