Staph infections in dogs can be difficult to eradicate
without appropriate, consistent treatment
By Kim Campbell Thornton
Andrews McMeel Syndication
I was scratching my dog, Harper, beneath the chin a few weeks ago and felt a couple of unusual bumps. I couldn’t really get a good look at them because they were hidden beneath her wavy, mid-length coat. A few days later, they had multiplied.
Our veterinarian diagnosed a staph infection based on the appearance of the bumps and the prevalence of that type of bacteria on canine skin. Usually it doesn’t cause any problems, but licking, scratching, trauma or metabolic changes can cause staph populations to grow out of control. He prescribed a course of antibiotics and daily baths with medicated shampoo for a week.
Staph — short for staphylococcus — infections are common in dogs, says William H. Miller, a veterinary dermatologist at Cornell University College of Veterinary Medicine in Ithaca, New York. In rare instances, staph infections can be triggered by an immunodeficiency in which the skin’s protective barrier is weakened, but more typically they follow damage to the skin by some underlying disease.
“Allergies are the primary culprit,” he says. “Everyone has bacteria and yeast on their skin surface, and they typically do no harm as long as the individual’s skin and immune system are normal. With allergy, the skin is easily damaged by licking and scratching, and that sets up the perfect climate for infection with the animal’s own bacteria.”
The most common signs are hair loss and itching. If you have a shorthaired dog, you may notice small, red, raised bumps, known as papules, or pimples, also called pustules. These are hidden in dogs with thick, dense coats — unless they appear on less-furry areas, such as the belly. As the infection progresses, you may see more hair loss — caused by the dog scratching the itchy area — and scaling, or flaky skin. Harper’s infection was localized to her neck, but dogs with widespread infections can suffer intense itchiness.
A variety of skin disorders cause pustules in dogs, but infection is the No. 1 cause, Dr. Miller says. Staph infections can be tentatively diagnosed simply by looking at the lesions, but cytology — examining the pus in the pustule microscopically — is required to confirm it. If the bacteria present are round — cocci — it is most likely a staph infection, but a bacterial culture is necessary to be certain the bacteria are staph.
“Although that is a valid reason to do a culture, the real benefit of a culture is to identify which antibiotics can be effective in treating the infection,” Dr. Miller says. “If the bacteria are susceptible to the antibiotic being used, the drug has to be used at the correct dosage to kill the bacteria, and it must be used long enough to kill all the bacteria.”
Treatment can take weeks to months, depending on the extent of the infection and whether it is superficial or descends far down the hair follicle. Topical treatments such as ointments, mousses, sprays and shampoos can help to shorten the course of treatment. Dogs should be treated until the lesions disappear, plus a few extra days to ensure that the deep part of the infection is wiped out. Stopping treatment too soon can cause infection to recur, this time with antibiotic-resistant bacteria.
Infections can’t be transmitted, but bacteria or yeast can be transferred from one animal to another through proximity. Owners themselves may transfer the microbes if they pet an animal with abnormal skin and then pet another animal without first washing their hands. If you know that one pet has a skin infection, hand hygiene is important to prevent spreading it to other animals in the home.
Take treatment seriously.
“For any number of reasons, we are seeing more and more cases of resistant bacteria, and some are so resistant that we have few or no antibiotics that can be used,” Dr. Miller says. “In some cases, the animal has to be euthanized because we have no effective means of treating the infection.”
PHOTO CAPTION: Wounds caused by excessive scratching or licking at the skin are one of the ways that normal populations of staphylococcus bacteria can grow out of control.