Zoonotic Diseases

Zoonotic Diseases: What Ted Nugent Never Told You!

Sarah Thatcher-Mason, DVM

A zoonotic disease is an illness which can be transmitted from animals to man.  They can be caused by bacteria, viruses, fungi and protozoal organisms.  Most healthy individuals are able to successfully fight these illnesses without ever showing signs of disease.  Young children, elderly individuals and immune compromised individuals however, may not be able to fight these infections so easily.  There are many known zoonotic diseases, the following are a few of the most commonly transmitted from companion animals to man.          

Toxoplasmosis is a protozoal disease caused by Toxoplasma gondii oocysts (eggs) in cat feces.  This disease is a significant risk to HIV+ individuals and pregnant women.  Ingestion of infective oocysts can cause serious birth defects and life-threatening illness in immuno compromised individuals.  Prevention of infection includes frequent (daily) cleaning and changing of cat litter, minimizing contact with cat feces and of course, washing your hands well after handling you cat or cleaning her litterbox. 

Cat Scratch Fever is not just a popular 80’s rock song.  It’s a potentially serious bacterial illness caused by the bacteria Bartonella henselae.  It is most commonly associated with cat scratches and is transmitted from cat to cat by fleas.  Humans become infected when bacteria-laden flea feces is deposited in an open wound (cat scratch).  Infected individuals may develop inflammation and pustules around the scratch itself, the lymph nodes will swell and they may spike a fever.  Most infections are easily treatable with antibiotics but some – the very young, elderly or those who are immunosuppressed can develop life-threatening illness.  Prevention focuses on adequate flea prevention in your cats, keeping nails trimmed, and of course washing all scratches and bites immediately with soap and water. 

Larval migrans is the term used to describe the aberrant migration of parasites (intestinal worms) through the tissues of an abnormal host (ie: human).  This can occur through the ingestion of parasite eggs (that’s right, from poop) or penetration of certain parasites through the skin.  Ingested parasite eggs hatch in the GI tract, then burrow through the tissues to the spinal cord, muscle, brain and even the eye where they cause a severe inflammatory reaction and permanent damage if not removed.  It is extremely important to maintain your companion animals on a regular de-worming schedule to prevent over-infestation with intestinal parasites.  This is why dogs aren’t allowed on the beach!

Giardiasis is an intestinal protozoal infection caused by the ingestion of contaminated feces.  It causes severe diarrhea leading to dehydration, electrolyte imbalance, and weight loss in susceptible individuals.  Infections are usually associated with livestock but can be contracted from infected cats and dogs.  Prevention consists of providing rapid treatment for suspected infections in companion animals, strict litter-box hygiene, careful handling of animal feces and diligent hand-washing after handling animals.  Giardia is the main organism folks are trying to avoid when they filter or treat their water in the wilderness.  Many people and animals have antibodies to Giardia in their blood already:  they have been exposed and overcome the infection naturally

Ringworm is a fungus, and not a “worm” at all.  The round raised lesions that the fungus cause on the skin as it grows outward are the reason for the name.  Young long-haired kittens are especially susceptible to this infection, and it is often passed to children when they handle them.  Young animals and young children are more at risk because their immune systems have not been exposed to the organism previously.  This fungus is very similar to the one that causes athletes’ foot.

Theses examples are just a smattering of examples of zoonotic diseases.  Rabies, leptosporosis, scabies, MRSA, brucellosis, psittacosis, salmonella, e. coli, avian flu, and of course, mad cow disease, are a few others. It can be a dangerous world out there!  Diligent hand-washing, timely deworming and vaccination programs, and good hygiene will all greatly reduce the chances of contracting a zoonotic disease.  Please contact your local veterinarian if you have any questions or concerns. 

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