Parasites come in two main varieties, external and internal, but all are bad for your pet’s health. In some cases, they endanger human health as well.
With the potential for parasites to harm both animal and human health, veterinarians at Colorado State University consider parasite control a cornerstone of preventive veterinary care.
Got a pot-bellied puppy? A cat that vomits regularly? These are a signs of gastrointestinal parasite infestation. These parasites are often called gut worms, although not all are truly worms.
Common internal parasites
Parasites that commonly infest the gut include roundworms (Toxocara species), hookworms (Ancylostoma species and Uncinaria stenocephala), whipworms (Trichuris species), Giardia and Coccidia (Cystoisospora species).
Signs vary with the parasite, though common symptoms include vomiting, diarrhea, large belly, lack of appetite, pale gum color and failure to gain weight. Puppies and kittens are most often affected: Nearly one-third of puppies and one-fourth of kittens less than 6 months of age are infested, and they shed roundworm eggs in their feces.
Roundworms and hookworms can also affect people, particularly children and those who are immune-compromised.
Another common internal parasite is heartworm, or Dirofilaria immitis. This parasite is transmitted to dogs and cats through mosquito bites, putting it in the category of vector-borne diseases. A few cases have been reported in people as well. Despite the name, adult worms live in the blood vessels of the heart and lungs. This causes coughing, difficulty breathing or exercising, weight loss and vomiting in cats. A large number of worms can cause weakness and physical collapse.
Got a cat losing hair? An itchy dog?
Bald spots and scratching may be signs of external, or ectoparasite, infestation. Common ectoparasites include fleas (Ctenocephalides and Pulex species), ticks (multiple species types), mites (Sarcoptes and Demodex mange mites) and lice (multiple species).
Mites and lice are species specific, meaning they affect only one species; people are not at risk. Fleas and ticks can affect multiple types of mammals in the house, including humans. There are several infectious organisms that cause disease and are transmitted by ticks – again, vector-borne diseases. These may also infect people and include:
- Ehrlichiosis and anaplasmosis are blood diseases that are transmitted by ticks and cause inflammation in the body.
- Lyme disease is caused by the bacterium Borrelia burgdorferi, which is transmitted by infected ticks. Clinical signs in dogs and people include fever and muscle and joint pain.
- Rocky Mountain spotted fever is rare in the Rocky Mountain region but occurs in the southern Atlantic and south central states. The bacterium that causes Rocky Mountain spotted fever, Rickettsia rickettsia, also is transmitted through the bites of infected ticks. Initial signs are fever and pain, but inflammation of the blood vessels, called vasculitis, occurs and is potentially fatal.
Scared yet? No need. However, it’s important to talk to your veterinarian about minimizing the health risks of parasites to your pet and your family – and to get your pet on a recommended schedule for routine de-worming and heartworm preventives.
All puppies and kittens should be screened for intestinal parasites and re-tested until no parasites are detected. Adult animals should be screened at least annually.
Tests for heartworm are recommended annually and can be started when your pet is 7 months of age.
Parasite preventives have minimal side effects and are very effective when given on time. The Companion Animal Parasite Council and Centers for Disease Control and Prevention are excellent resources for additional information.
Dr. Rebecca Ruch-Gallie is a veterinarian with the Community Practice service at Colorado State University’s James L. Voss Veterinary Teaching Hospital. Community Practice provides general care, wellness services, and treatment of minor injuries and illnesses for pets. Read about vaccinations, health insurance, exercise, spay/neuter and screening tests in our Pet Health series, Cornerstones of Preventive Care.