Anthrax in Dogs

Can dogs get sick from anthrax?

You may have heard anthrax discussed as a potential bioweapon. Most mammals are susceptible to anthrax, but different animals have different levels of susceptibility. In general, herbivores are more susceptible to anthrax than carnivores. Under normal circumstances, cases of anthrax in dogs are very rare and dogs seem relatively resistant to infection.

What causes anthrax?

Anthrax is an infection caused by a bacterial microorganism called Bacillus anthracis. This type of bacterium can develop small spherical bodies (spores) within the bacterial cell, and each spore can develop into a new anthrax bacterial cell. Spores can survive in the environment much better than the more fragile parent cell and are more resistant to disinfectants. 

Some reports indicate that spores may survive in the environment for up to 40 years under certain conditions. Fortunately, it takes many spores to cause an infection that results in clinical signs of anthrax.

Is anthrax a new disease?

No, anthrax has been described in the medical and veterinary literature for hundreds of years. It occurs in all parts of the world as a sporadic disease in farm animals and occasionally in wild animals.

How is anthrax spread?

Anthrax is not normally contagious from animal to animal. Most livestock infections occur by inhalation or ingestion of spores from a pasture contaminated by a decomposing, infected carcass. In predators such as dogs, ingestion of infected meat is the usual route of infection. In people, anthrax is typically diagnosed in farm workers, veterinarians, and slaughterhouse personnel who have handled infected carcasses. Even then, it usually takes a high dose of spores to cause more than a local skin infection. In the past, sheep fleeces were a common source of anthrax spores, and anthrax in those workers was called "wool-sorters disease".

What are the symptoms of anthrax?

Anthrax can cause different types of disease.

• The most common type of infection in people is the dermatological (skin) form, which occurs due to contact with the anthrax organism or its spores. It causes local inflammation and the formation of black pustules on the skin.
• An intestinal form occurs when large numbers of organisms are ingested, causing inflammation of the intestinal lining and bloody diarrhea.
• A pneumonic form develops when large numbers of the anthrax organism or spores are inhaled into the lungs, causing pneumonia and respiratory problems.
• The infection can also have a generalized form, affecting most or all body systems, including the brain. The general form causes fever, poor appetite, and weight loss.

The rare cases reported in pet animals have usually been the intestinal form of anthrax, caused by eating infected meat. With this form, symptoms include acute gastroenteritis with vomiting and diarrhea. The throat may swell and there may be visible swelling of the neck extending to the face and head. Infected dogs usually have a fever, poor appetite, and weight loss. If the lungs are infected, coughing and difficulty breathing can occur. Rarely, focal necrotic skin lesions may occur. The tongue and lips may also be affected.

Diagnosis is made by culturing the anthrax organism.

How is anthrax treated?

The anthrax bacterium is susceptible to a number of antibiotics. Currently, the antibiotics of choice are penicillins, enrofloxacin, and doxycycline. Ciprofloxacin has also shown efficacy; however, absorption of this drug is variable in dogs so higher dosing and/or combination with other antibiotics may be needed. Treatment is highly effective in the early stages of infection.

Can my dog be vaccinated against anthrax?

There is currently no commercial anthrax vaccine licensed for use in dogs, although vaccines of varying effectiveness have been produced for livestock. In some parts of the world, domestic livestock and humans employed in high-risk occupations may be vaccinated.