Household Hazards

How everyday products make us sick.

Not Trying to be Peevish

Pet risks as well as benefits

A recent New York Times report carried the somewhat tongue-in-cheek header, "Add to the Recall List: Millions of Frozen Mice." (http://www.nytimes.com/2010/07/30/business/global/30mice.html) The story concerned an international epidemic of a serious diarrheal illness, salmonella, linked to contaminated reptile food in the form of frozen mice. These wholesome snacks for snakes had been internet marketed by a company aptly named MiceDirect. This outbreak may be noteworthy in part because of its internet flourish, but it is, in fact, but one example of a variety of potential human health issues linked to pet ownership.

Not long ago I was dressed-down by a colleague for including pet-related issues in a review of respiratory hazards linked to hobbies, avocations, and pastimes. "Pets are not a hobby - they are a part of the family!" I was scolded. Family or not, pet enthusiasts should be aware of the possible exposures that can be involved, just as others in contact with animals should also be aware of potential risks, whether on the job (for example, animal husbandry) or through an avocation (which can range from taxidermy to spelunking).

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In this regard, salmonella is hardly a new problem, having been linked to pet turtles and snakes long before the magic word of mail-order mice-paks. As with this new exposure scenario, children often have been the most vulnerable. Indeed, the risk of certain infections to those who live with pets has been the subject of many a learned medical review. A lengthy and erudite article on the subject, for example, appeared in the New England Journal of Medicine in 1985, devoted almost entirely to various parasites and other infections transmissible by dogs or cats. (http://www.ncbi.nlm.nih.gov/pubmed/3900726)


In the past quarter of a century since that publication appeared, the pet role-call list of disease candidates has expanded way beyond the passé canine-feline dyad and has even transcended snakes, lizards and, the occasional amphibian. In 2003, for example, the Centers for Disease Control reported an outbreak across the Midwest of an otherwise exotic viral disease, human monkey pox. The infection was traced to pet prairie dogs that had been infected when sharing quarters with an infected Gambian giant rat, also destined for an ill-fated pet owner with unusual tastes. (http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5223a1.htm)


Nor is infection the sole risk to consider. Allergy to common household pets, of course, is commonplace and extends not only to cohabitants and to visitors, but also to those who are sensitized and come into contact with animal antigen tracked along in the pet owner's clothing. This is particularly well documented with cat antigen, which, through such carriage, can be detected in any number of public spaces. Moreover, allergy-related phenomena are not limited to common furry friends. For example, insect larva, worms or crustaceans used in feeding pets birds or aquarium fish can be potent sensitizers linked to asthma and related responses.

One of the most important non-infectious human illnesses tied directly to pet keeping is a serious and potentially life-threatening lung disease called hypersensitivity pneumonititis (also known as extrinsic allergic alveolitis). This insidious, immunological ailment is often linked to domestic birds, including canaries, parrots, budgerigars and love birds. Some affected pet owners have gone on to require lung transplantation.

Needless to say, living with a pet animal has its benefits even if there may be risks entailed such as those enumerated here. My colleague who was so displeased with my lumping of pet ownership with hobbies and other pastimes might not be surprised to learn that an earlier usage of "pet" in English (a century before it might refer to a cat or dog) was solely meant to describe an indulged or favorite child.

Paul D. Blanc, M.D., M.S.P.H., is Professor of Medicine and Endowed Chair in Occupational and Environmental Medicine at the University of California San Francisco.

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