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Other Respiratory Tract Disorders
Hypersensitivity Pneumonitis
Idiopathic Intersitial Lung Disease

Environmental Antigens - Cats

Q: What health risks are associated with inside cats?


A: Cats compete with dogs as the most popular indoor family pet. They are loved, admired, hated and feared, arousing much emotion. Generally humans and cats live together for the betterment of both parties. Occasionally cats elicit disease in humans.

The diseases are categorized as immunological and infectious.

1. Immunological responses include the common allergic reaction and other immunological mediated responses to infections. Cats rank as one of the world's two top allergens in eliciting the allergic response (IgE) in humans. The other is house dust mite. Susceptible individuals develop IgE antibodies to cat proteins. Cat saliva and dander proteins can elicit symptoms of allergic conjunctivitis and allergic rhinitis, known commonly as hay fever. Asthma is the most serious allergic disease in terms of mortality. The falling rate of cat dander is slow, so that it is airborne for a very long time, probably contributing to its ability to elicit a rapid allergic response in allergic individuals(19). Recent studies have shown conflicting data on the exposure to cats early in life, and the resulting increase or decrease in sensitization to cat of the child (20). It is a prevalent antigen, found for many months in a dwelling after the cat is gone.


2. The immunological system responds to some infections by developing antibodies as well as mounting the immediate response to the invasion. Other immune-mediated responses are speculated. The rise of opportunistic infections because of the increased population of immunocompromised individuals has been noted. People on immunosuppressive medications to treat cancer, some immunological diseases, as well as those with human immunodefeciency virus (HIV) have resulted in increased numbers of individuals susceptible to opportunistic infections. The illnesses of this category related to cats are the cat-scratch diseases (21).


3. Infectious diseases spread by cats are viral, bacterial, fungal and parasitic(22). An example of viral disease is rabies controlled in house pets by vaccination. Rabies causes fever and toxic symptoms of the brain. Ringworm is a fungal disease transmitted from cats or other animals to humans. It's a spreading infection on the skin. Bacterial infections are cat-scratch diseases, usually a self-limiting illness of 6-12 weeks, but easily treated with antibiotics. Regional lymphadenopathy is the primary symptom with low-grade fever and malaise. It occurs 1 to 2 weeks after a pustule at the site of a previous cat scratch. Other symptoms can be headache, anorexia, weight loss, nausea, vomiting and enlarge spleen. Rarely is there progression to encephalopathy and other serious illnesses(21).


4. Toxoplasmosis is an infectious (23) disease caused by a protozoan, transmitted to humans in the oocyte stage through the feces of infected cats or raw meat. It is a dangerous illness for the fetus of a pregnant woman and for immunocompromised individuals. If it occurs during pregnancy, 8% of the fetuses will have serious anomalies including mental retardation, chorioretinitis, and hearing loss(23). The usual recommendation for pregnant women is to have someone else clean and safely dispose of the litter box. In healthy, non-pregnant individuals toxoplasmosis causes vague mild symptoms such as fatigue and fever. In immunosuppressed individuals lesions of the central nervous system can occur, toxoplasmosis cysts being one of the many neurological complications of HIV(22).


5. The final infectious human disease associated with cats are the ascarids and hookworms. Disease due to ascarids occurs when the eggs are accidentally ingested. They hatch to the infective larval stage. The infective larvae migrate through the body's major systems wreaking damage and inducing allergic responses at the organ site. The infection may leave children with permanent visual or neurologic damage. The toilet activities of cats, along with the high ascarid/hookworm infestation rate in the U.S. lead to this health hazard(22). Hookworms can infect people when larvae in the soil enter the body through the skin or the mouth. Infections of the skin are the most common, characterized by linear eruptive lesions with intense itching caused by migration of the larvae in the skin. One of the hookworm species can penetrate into deeper tissues and cause eosinophilic enteritis as they migrate to the gut to mature. Ascarids and hookworms are the reason for proper veterinary care of pets to include worming. Also the proper care of litter boxes and the covering of children's sandboxes are part of control.


6. Cats may mark territory by urinating on carpets, upholstery, flooring. Urine on a carpet is wicked to the pad below, and to the concrete slab beneath. Prime conditions are, therefore, set up for unseen microbial growth that can lead to the health problems discussed in this webpage. The range of illnesses ranges from nuisance symptoms to life threatening illnesses.


7. Cats' paws and fur carry in bacteria, molds, and other outside substances into the house, leading to a greater likelihood of home microbial contamination for houses with indoor cats. (24).