Anthrax in Dogs

Overview of Canine Anthrax

Though anthrax has recently been brought to the public’s attention, it is actually one of the oldest recorded infectious diseases. Dog owners want to know more about anthrax which we will answer below.

Anthrax is caused by the bacteria Bacillus anthracis, anthrax outbreaks periodically occur throughout the United States, but since it usually affects horses, cattle, sheep and goats, there is little media coverage. Typically, an outbreak will occur after periods of drought followed by heavy rains. There are several areas within the United States that are considered endemic with anthrax.

Anthrax affects all warm-blooded animals, including humans. It is a bacterial infection that has been reported all over the world. The bacteria is very resistant to heat, chemical and environmental changes due to its ability to become encapsulated in a spore. These spores then live in the soil, waiting to be inhaled or ingested by grazing livestock.

Horses and livestock are most often affected, but dogs and cats can become infected, despite their natural relative resistance to the bacteria. Though inhalation is the cause of the recent human cases, dogs and cats are most often infected after ingesting meat from a carcass infected with anthrax. Other routes of infection include inhalation as well as migrating through the skin.

Once the bacteria enters the body, it begins to invade body tissues. If not treated, the bacteria continues to multiply and then begins to release a toxin. Infected dogs and cats initially develop swelling of the throat and gastrointestinal disease. Without treatment, facial swelling occurs, the bacteria spreads and the animal succumbs to kidney failure, shock and respiratory failure. From the time of exposure to development of symptoms, 3 to 7 days have passed.

Anthrax is a disease with zoonotic potential. This means the disease can be passed from animal to humans, but the disease is not as communicable as a virus. The anthrax spores are the contagious part of the disease. To become a spore, the anthrax bacteria must be exposed to oxygen.

This means that direct contact with a contaminated animal does not automatically result in an infection. A person must be in contact with the infected animal’s bodily fluids or abnormal discharge to be at risk for infection.

Although there have been reports of inhaled spores recently, skin contact with anthrax is the most common way people contract the disease. The spores are exposed to skin abrasions, lacerations, etc. and a superficial wound develops.

Anything that would expose the body tissues containing anthrax bacteria to oxygen should be avoided in an attempt to reduce the number of spores in the environment. Any animal that dies from anthrax should be cremated to avoid development and spread of additional spores.

Animals diagnosed with anthrax should be handled with extreme caution. Body fluids should be avoided and necropsy should not be performed.

What to Watch For

Signs of anthrax in dogs may include:

• Difficulty swallowing
• Facial swelling
• Vomiting
• Diarrhea
• Loss of appetite
• Lethargy
• Bloody discharge from mouth, nose and rectum

Diagnosis of Anthrax in Dogs

Diagnosis can be difficult. An accurate and thorough history is very important. Since anthrax is uncommon in dogs, exposure to carcasses known to be infected with anthrax is a crucial part of the medical history and diagnosis. Dogs rarely ingest or inhale enough spores from the soil to cause illness.

If there is an index of suspicion for anthrax, examination of the blood or any blood-tinged discharge can reveal the bacteria. The fluid is prepared and appropriately stained. Rod shaped bacteria will be seen when the fluid is microscopically examined.

Additional tests, such as fluorescent antibody exam of smears prepared from blood or body fluid, can be used to confirm the diagnosis. Lymph node biopsy can also reveal the signs of anthrax bacterial invasion.

Treatment of Anthrax in Dogs

Early treatment is crucial. Successful treatment involves hospitalization and supportive care. Intravenous fluids and high doses of penicillin, ampicillin or enrofloxacin are administered.

Despite aggressive treatment, some animals do not survive. After death, extreme care must be taken. Necropsies are not recommended and neither is burial.

Home Care and Prevention

There is no home care for anthrax. It is highly contagious and extreme caution is necessary when treating infected animals. Since anthrax is most often associated with ingestion of infected carcasses, do not allow your pet to roam. Keep dogs in a fenced in yard or on a leash.