Zoonoses: Pets, People and Parasites

What are parasitic zoonoses?

They are diseases primarily of animals which are caused by parasites that can be transmitted to people.

How do they harm animals and people?

IN ANIMALS: Intestinal parasites can cause gastrointestinal upset, vomiting, diarrhea, blood loss, intestinal obstruction, weight loss, pot-bellied appearance, and general failure to thrive.

IN PEOPLE: Zoonotic parasites can cause a variety of conditions depending on the parasite, the route of infection, the person's age and immune status, and the size of the infectious dose. The signs in humans range from sub-clinical (no noticeable problems) to blindness or even death.

Who is hurt by these diseases?

The most likely candidates for parasitic zoonosis are young children, because they are less careful about hygiene, are likely to put their hands in their mouths, commonly play in dirt or sand, are in very close contact with the pet, and may eat grass or soil contaminated with parasite eggs. Immunocompromised adults are at increased risk for zoonotic disease. Still others are at increased risk because of high exposure due to their occupation, e.g., veterinarians, veterinary technicians, farm and ranch workers, and dog and cat breeders. Campers and travelers may be at more risk because of exposure to parasites from wild or domestic animals via contaminated water and vegetation, or the lack of hygiene facilities.

Where do the parasites come from?

Intestinal parasites (eggs and larvae) are virtually everywhere outdoors, and animals are generally infected with parasites at birth or a very young age. Puppies are almost always born with worms and continue to pick up more parasites via nursing and fecal contamination. Kittens pick up parasites very early through nursing and the environment. Some parasite eggs are particularly resistant and remain viable in the soil for many years. Thus, it is practically impossible to rid the environment of already existing contamination.

Parasites and parasitic larvae can be found in:

• Yards and Homes
• Gardens and Public Parks
• Sandboxes and Litter boxes

How do humans get parasites from animals?

Humans can contract zoonotic parasites in several different ways:

• By accidentally eating parasite eggs or larvae from unwashed fruits or vegetables
• By swallowing a flea that contains the intermediate stage of a parasite.
• By skin contact with parasite larvae while walking barefoot
• By not washing hands after handling or playing with animals
• By not practicing good hygiene and sanitation

Wash hands after handling animals

When animals are very young they pass large numbers of eggs. Puppies and kittens also crawl through feces and groom each other. The mother dog anq cat may shed large numbers of eggs after parturition, and in addition, when grooming their offspring, they are being re-infected constantly. So, the risk of zoonotic infection in people increases around a litter of puppies or kittens. The presence of a single puppy in a household has been positively correlated with human zoonotic disease. Also, people who take their pets to public parks or other common areas, where other pets routinely defecate, are at greater risk because pets can become more heavily, infected from these exposures.

Strategic Deworming is the only sure way to minimize zoonotic parasites

What is strategic deworming?

It is routinely deworming animals at intervals designed to interrupt the parasite life cycle before eggs or larvae are passed into the environment.
Deworming accomplishes two important goals:

1. Ridding the pet of existing parasites
2. Removing parasites before they reproduce, thus preventing further contamination

PARASITES and How They Affect Humans

Hookworms (Ancylostoma caninum)

Hookworms cause red, irritated, inflamed lesions in the skin where larvae burrow under the skin (Cutaneous Larva Migrans, CLM). Victims suffer gastrointestinal distress, such as diarrhea and cramping, when parasites mature in the intestine.

Hookworms infect people who come in contact with contaminated dog or cat feces. People who go barefoot in contaminated sand or soil, or people whose work requires them to lie on the ground, such as plumbers, are vulnerable to hookworms. The CLM lesions generally resolve within several weeks to months.

Roundworms (Toxoccara canis)

Roundworm larvae migrate through and encyst in body tissues, causing allergic responses and tissue damage. Clinical signs include fever; coughing or rashes (Visceral Larva Migrans, VLM). The eye is a known site for parasite migration, resulting in partial vision loss or blindness (Ocular Larva Migrans, OLM). Larvae of certain ascarids may migrate to the brain and produce neurological signs and even death in dogs, paratenic hosts (small mammals, birds) and people. Brain involvement is particularly likely and very dangerous if the roundworm is from a raccoon. Dogs may also become infected with these raccoon roundworms. Roundworm eggs are frequently found in contaminated soil and in unwashed fruits and vegetables.

Tapeworms (Family Taeniidae)

Gastrointestinal discomfort (Dipylidium caninum) is produced by tapeworms in the gut. Hydatid disease (EchinocQccuS spp.) occurS when larvae encyst in body tissues. Cysts within organs, usually the liver, may become extremely large. Symptoms vary depending on the organ affected, but they resemble those of any space- occupying lesion, such as a tumor. Surgery and new anti-parasitic drugs are used to treat infected people, and the success rate has improved in recent years. Nevertheless, the damage can be very serious.

Whipworms (Trichuris Vulpis)

Canine whipworms have been reported only rarely in humans.