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Posted: 2004-02-01
Zoonotic Diseases


Zoonotic diseases are the ones that animals can transmit to people. As veterinarians it is our job to make sure that doesn't happen. Here are the important ones:


1. Rabies: Thankfully rabies is rare in Rockland County. It is imperative that all dogs and cats are currently immunized against this fatal disease. Also it is imprudent to feed stray animals because they are generally not vaccinated. In addition food left outdoors attracts racoons, skunks and other wildlife that can be important rabies vectors. 

2. Toxacara: Toxacara is the common roundworms of dogs and cats. This is not a parasite of people, but people can become incidentally infected. Puppies contract the parasite from their mother. Virtually all puppies are infected neonatally. When the parasite matures microscopic eggs are passed in the puppies stool. These eggs are not immediately infectious because they require a period of several days to mature. When people (usually children) ingest the mature roundworm eggs they can be infected. The parasite can migrate aberrantly and end up in unfortunate places, like the eye. It is recommended that pet's stools be picked up immediately and not allowed to contaminate the yard. Children should be taught to wash their hands after handling pets and certainly before eating. Puppies and kittens should have their stools examined more than once during their pediatric examination series and should be given worming medications as a matter of routine. Interceptor (milbemycin) the monthly heartworm preventative effectively kills this parasite. 

3. Ringworm: Ringworm is not a worm at all. It is a fungal infection of the skin. It is most commonly found in kittens and puppies, but adult animals can carry it as well. Long haired kittens like Himalayans and Persians seem to be predisposed and can often carry the infection without showing signs. Ringworm infections can immitate a number of skin conditions, but typically infected pets have crusty hairless areas most commonly on the face and paws. Sometimes (less than 50%) these affected areas will fluoresce (light up with a green color) when illuminated with ultraviolet light. Confirmation of the infection is done by performing a fungal culture. This is done by plucking some hairs from the lesions and embedding them in a special culture plate. If there are no lesions, suspected pets are combed with a toothbrush from head to toe and the hairs caught in the bristles are cultured. Ringworm can be highly contagious, especially to children. The fungal spores can be difficult to eliminate from the environment. We recommend that all long-haired kittens be cultured on their first exam. In people ring worm usually presents as typical annular itchy lesions. Children often snuggle with pets and present with lesions on their neck and face. In humans the infection is treated with topical creams. In pets a combination of topical and oral medications are used. 

4. Scabes: Scabes is a form of mange caused by the mite Sarcoptes scabei. It is a highly contagious parasitic infestation of the skin. Puppies are most commonly affected, but adult dogs can carry it as well. Affected dogs are scratch incessantly. The mites burrow through the superficial layers of the pet's skin. There is hairloss and crusting of the skin especially on the tips of the ears the elbows, hocks and lower half of the body. The diagnosis is made by scraping the skin with a blade dipped mineral oil and the resulting scale is examined microscopically. The mites are often difficult to find and the treatment is often done based on a high index of suspicion. People in close contact with affected animals can become infected as well, but the infection is self limiting. Once the pet is treated the human infections generally resolve. Lotions or creams may be prescribed by the physician.

5. Toxoplasmosis: Toxoplasmosis is caused by a single-celled protozoan parasite called Toxoplasma gondii. Cats are the definitive host for Toxoplasma and are the only species in which it can complete it's life cycle. Almost all species of mammals and birds can become infected. Cats usually become infected by hunting and eating small rodents and birds. Young kittens who hunt can shed the infective stage of Toxoplasma in their stools for 10-14 days. Thereafter they usually mount an immune response capable of suppressing the parasite for the rest of their lives, although intermitiant shedding of the parasite in the stools is a concern especially if the cats become immunosuppressed later in life. Similar to roundworms the parasite stages passed in the stool must mature for a few days before they are infectious to people so prompt cleaning of the litter box is recommended. More than 50% of the human population in the United States have toxoplasma antibodies. Most of us contracted the parasite by eating inadequately cooked meat (usually pork and lamb). Most of us had inapparent infections that will cause us little harm unless we are severly immunosuppressed (with AIDs for example). Initial infection early in pregnancy is the big threat with this parasite, which can seriously impair fetal development. It is recommended that pregnant women be excused from litterbox chores (sorry fella's!) and that they wear plastic or rubber gloves when preparing meat for the family. All meat should be thoroughly cooked (well done). Gloves should be worn when gardening because feral cats may be defecating in the garden. Cats should be kept indoors to prevent hunting. There is absolutely NO reason to give up the family cat. Cats should have stool examinations perfomed as part of their routine medical care, but blood testing cats is not very useful. 

6. Bartonella: Bartonella is the bacterium that causes Cat Scratch Fever. The infection is generally asymptommatic in cats. There appears to be an association between the presence of this bacterium in the cat and chronic conjuncitivits and gingivitis, but cause and effect has not yet been established. In humans Bartonella causes a flu-like illness characterized by fever and aches. Sometimes there is enlargement of lymph nodes tha causes concern for physicians. The disease in cats and people is readily treated with antibiotics. We recommend that all kittens especially strays and thoses from animal shelters be tested. Only a small amount of blood is needed so even very young kittens can be tested. We usually do this at the same time that they are tested for the feline leukemia and feline aids viruses. Kittens that test positive are treated with the antibiotic zithromycin for 10 day and retested 1 year later. 

7. Psitticosis or Chlamidiosis: This is an infection of birds. It is most important in psittisine (parakeets and parrots) and pigeons. It is a common cause of illness in birds, but can also be asymptommatic. Disease in people can vary from upper respiratory symptoms to a flu-like syndrome to pneumonia. Elderly and immunosuppresed individuals are at greatest risk. Affected people often think that they have developed allergies to their birds. It is recommeded that newly aquired birds be tested for Chlamydia. Cages should be kept clean because the disease is often spread by aerosolized bird droppings. Physicians should be informed when patients have birds as pets. Birds are treated with doxycycline, most commonly by a series of injections. People usually respond well to tetracycline or erythromycin type antibiotics.