Friday, June 5, 2009

Look What The Cat Brought In!

It seems like I'm on a roll with the posts about zoonoses, so here's a reprint of an article I wrote for Pediatrics for Parents a couple of years ago:


Gayle Robison, DVM

While cats make wonderful house pets and companions, these intelligent, graceful creatures have the potential to carry several diseases that can infect their human friends. Among these are bacterial and fungal diseases, and worm infestations. Children, by virtue of their immature immune systems, are particularly susceptible to the most common of these: cat scratch disease, ringworm, and ocular/visceral larva migrans.

Cat Scratch Disease
Otherwise known as cat scratch fever or bartonellosis, this bacterial infection is most often associated with kittens, though an obvious scratch is not always involved. Human infection results in fever, swollen lymph nodes, fatigue, and rarely more serious disease in immunosuppressed individuals.
Cats infected with Bartonella bacteria often have no signs of illness. They acquire the disease by means of flea bites, which spread the bacteria from other cats. When fleas subsequently feed on an infected cat, they leave bacteria-laden droppings in the cat’s fur. As the cat scratches at its fur in response to the crawling fleas, the claws pick up the flea feces, which then are inoculated into the skin of an unsuspecting person if they are scratched by the cat.
Feline bartonellosis is entirely preventable by adequate flea control, particularly while the cat is still young. Since the introduction of monthly flea control products such as fipronil and imidacloprid ten years ago, this disease has become less common, but it remains a concern for vulnerable people.
To minimize the risk of human infection, cats’ claws should be clipped short (front and back). Cats suspected of harboring the bacteria should be treated with antibiotics after consulting with a veterinarian. Children should be taught how to handle the cat or kitten so as to decrease opportunities for scratching. Aggressive flea control on pets is vital to avoid this unpleasant condition in people.

Properly called dermatophytosis, this pesky infection is caused, not by a worm, but by a common fungus that ordinarily inhabits the soil. Most people are familiar with the scaly, reddened, circular skin lesions typically seen with ringworm. The condition may or may not be itchy, and can be highly contagious.
Cats acquire ringworm infection from either the environment, another infected cat, or rarely from a person with fungal lesions. Skin lesions may not be apparent on the cat, but can be quite dramatic when they do appear, also as reddened, circular, flaky patches with a raised rim. Kittens are more commonly infected than adult cats due to their immature immune systems. Some cats have no visible skin lesions at all, and require special testing to determine whether they might be the source of a human infection.
Dermatophytosis prevention in the cat consists of avoiding contact with affected individuals and housing in a clean, dry environment. Treatment of cats, which can in some cases be prolonged and expensive, involves a combination of clipping the fur, bathing or dips, topical medication, and systemic medication. Prevention of human infection requires good hygiene (i.e. handwashing after petting the cat) and avoidance of contact with affected cats. Children especially should not hold affected cats close to their skin. Normal, healthy skin is ordinarily quite resistant to fungal infection, but minor abrasions or constantly damp skin can allow the fungus entry.

Ocular/Visceral Larva Migrans
Cats and kittens commonly harbor a variety of roundworm and hookworm intestinal parasites that can cause devastating illness and permanent injury to children. These worms, while usually only causing mild disease in their feline victims, shed their eggs in the pet’s stool to contaminate the environment. Children become infected by inadvertently ingesting the eggs, which then develop into larvae and migrate throughout the body, causing organ dysfunction and even severe damage to the eyes.
Kittens become infected during nursing (the worm eggs are passed in the queen’s milk), the worms develop inside them, and then the mature worms shed millions of eggs in the stool. These can build up in the soil to astonishing levels, and persist in the soil. Warm, moist conditions favor this ongoing environmental contamination, so we see more intestinal parasites in the southeastern United States, but they can be found everywhere. Sandboxes and loose garden soil can become special problem areas.
While roundworms and hookworms cannot be prevented in cats, they can be treated easily and cheaply. Veterinarians recommend frequent deworming of kittens beginning as early as two weeks of age. Proper disposal of fecal material from litter boxes is important. Routine deworming of adult cats may be necessary, depending on its risk of exposure to other sources of parasites such as prey ingestion.
Children should be taught to wash their hands after playing out of doors, and should avoid placing their hands in their mouths. Sandboxes should have latching lids that cannot accidentally close while the box is in use, and should be kept latched closed when not in use, as cats instinctively favor them for toilet use. The cat’s litterbox should not be accessible to small children.
In order to make our cats safe members of our families, it is important to be aware of the potential risks of the relationship, and take appropriate measures to minimize that risk. Pet cats can enrich our children’s lives in so many ways!