Market Watch: Parasites and their impact on the human-animal bond

I can remember as a kid my mother hollering "Stop kissing the dog! You're going to get worms!" or "No, the dog can't come inside—she has fleas!" This in a time when dogs ate gray mystery meat out of tin cans, garlic was the treatment of choice for worms, and we tossed banana stalks under the house to kill fleas.

Today, wellness and parasite control have progressed to a point that fleas and ticks live in fear, heartworm products are about as good as one could ever want and internal parasites are easily controlled. Right?

Well then how is it that you still hear people say "I let you bring the dog in, and now we have fleas!" or "The cat has maggots coming out her bottom!"

The reasons are clear in most cases. People don't understand parasite lifecycles and, more important, aren't using products that would work if used correctly. Pets are suffering with fleas and ticks and internal parasites—enduring preventable infestations and infections.

Increased awareness—and ignorance

Some years ago, dogs and cats began the migration from the backyard into the house and even into the bedroom. Pets have become members of the family. As we live in closer proximity and share more of our lives with them, we are far more observant of them than we were in the past.

Now picture this scenario: A new mother is sharing her chair with her new baby and the cat she has had since before she was married. Suddenly, Fluffy stands up and presents her rear end. There in all their wriggling glory are a dozen bits of what looks like rice. Before you can say "Hey diddle diddle," the cat and her fiddle are unceremoniously tossed outdoors and mom is in tears.

Fast forward to Thanksgiving when the family is preparing for a Norman Rockwell photo op. Grandma is sitting on the sofa next to the dog and petting its ears when she feels a bump. She looks more closely and lets out a scream that nearly deafens the dog. "Ticks! Your dog has ticks!" The poor dog is scooted out into the backyard where it can only watch the festivities through the window until the trauma is over and the tick can be removed.

Parasites have always existed, but owner awareness has greatly increased as the human-animal bond has expanded. The problem is that the average pet owner knows little about most parasites, their life cycles and the implications to animal and human health.

The threat from within comes to the forefront

While owners may see external parasites, evidence of most internal parasites is not seen. One notable exception is tapeworms. The lifecycle of the most common tapeworm in pets, Dipylidium caninum, involves the passage of tapeworm eggs in proglottids (characteristic "rice grains") passed in a dog's or cat's feces. The eggs are then consumed by flea larvae, which mature into the intermediate host, the adult flea. Infected fleas are ingested by a dog or cat, beginning the cycle again.

Other tapeworms (Taenia species) are transmitted by the ingestion of rabbits or small rodents (the intermediate host). The definitive host for the small tapeworm Echinococcus granulosus is dogs, which may become infected after eating infected sheep carcasses. Sheep and people are intermediate hosts for this tapeworm, making this an important zoonosis (see "Public health considerations for tapeworm infections"). The public health risk associated with Echinococcus species is significant. In regions of the country where it occurs, it is important to differentiate it from more benign parasites.

Public health considerations for tapeworm infections

Surveys have demonstrated a tapeworm infection prevalence of as high as 60 percent in dogs and up to 52.7 percent in cats, depending on geographic and hunting behavior factors. While most tapeworms are generally benign, causing few if any clinical signs, they are often found at very inopportune times and in very invasive locations. Additionally, owing to their relationship with the flea, they can be one of those "Oh no! Not again!" things if external parasites are not addressed as well.

Client education and prevention strategies

In addition to impacting the health of pets and people, parasites disgust and disturb people and interfere with the human-animal bond. They cause disease, cost money to treat and, in some cases, place people at needless risk of infection or infestation. Aggressive flea control is a major part of tapeworm prevention. However, some dogs and cats have strong predatory hunting drives that mean they may consume rabbits or small rodents, becoming reinfected.

The key is to ensure clients have basic knowledge of the external and internal parasites they might encounter and to make sure they are taking appropriate preventive measures using year-round control so they don't have to be alarmed by fleas, ticks, tapeworm proglottids or any other sort of parasitic creepy crawly.

Dr. Paul is a veterinary consultant as well as a founding member and former executive director/CEO of the Companion Animal Parasite Council. He has served as president of the American Animal Hospital Association. He now lives in Anguilla in the British West Indies.