Zoonotic Disease — From People to Pets to People

How Are Zoonotic Diseases Transmitted?

Parasitic diseases are among the most frequently occurring zoonotic diseases in pets, and they’re the most likely to infect average suburban Americans. The most common intestinal parasite in dogs and cats, the roundworm (Toxocara spp.), can pose a threat to children. Infected dogs and cats shed Toxocara eggs in their feces. People can be infected by accidentally consuming the eggs. Kids playing in dirt or sand might ingest Toxocara eggs, so pay special attention to sandboxes and make sure they are covered when not in use. Once in the body, roundworms in the larval stage migrate through tissues and organs, including the eyes. Roundworms can cause injury, even blindness.

People also get infected with zoonotic diseases through skin contact with parasites. For example, a larval-stage hookworm (Ancylostoma spp.), a common intestinal parasite of cats and dogs, can bore through skin and cause an itchy rash. Cat Scratch disease organisms (Bartonella henselae) are found in flea feces, and when those feces get into the body through scratches, bites or wounds, the organism can cause full-blown illness, including fevers and swollen glands. (Kittens are most frequently associated with transmission of this disease, so effective flea control at an early age is essential.)

Another way zoonotic diseases are passed is when people are exposed to infectious agents by eating contaminated food or undercooked meat and thus accidentally ingesting materials like feces-contaminated dust, dirt or even water. It’s alarmingly easy to consume parasite eggs. The eggs are very tiny and can easily become airborne during any activity that exposes fecal material, such as digging in the soil. These airborne particles can land on the mouth or be present in dirt that gets rubbed across the face and then swallowed. No one willingly eats animal poop, but statistics show about 15 percent of Americans have been exposed to roundworms — meaning they accidentally ate parasite eggs.

Zoonotic diseases also can occur through “bug” bites, such as when a tick carrying the infectious agent that causes Lyme disease bites you or your dog. This method of transmission — tick as delivery service — is the hallmark of what’s called a vector-borne disease. You cannot get Lyme disease from pets; instead, pets can increase exposure to infected ticks by carrying “hitchhiker” ticks into the home. These ticks may introduce the Lyme disease organism to your family. Ticks and fleas carry many potentially harmful organisms, and when they bite, they’re often leaving more than just an unpleasant presence.

Decreasing the Fear Factor

Take these precautions during warm-weather activities and throughout the year to help keep your family safe from zoonotic diseases.

  • Schedule annual or biannual veterinary visits for your pet, which should include fecal examinations.
  • Keep your pet on year-round monthly parasite prevention, as recommended by your veterinarian.
  • Keep pets indoors or supervised to discourage hunting, and do not feed pets raw or undercooked meats.
  • Wash your hands frequently, especially after handling animals and working outdoors. Be sure your children wash their hands after playing outside.
  • Wash wounds, even small cuts, promptly and thoroughly.
  • Wear gloves when gardening.
  • Clean cats’ litterboxes daily, wearing gloves, and always wash your hands immediately afterward.
  • Cover children’s sandboxes.
  • Avoid approaching, touching or handling stray animals.
  • Protect against ticks by wearing long-sleeved shirts, long pants and hats. Check for ticks after hiking, playing or working in tick-infested environments. Also consider using repellants.

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