Pets and parasites. Learn about the symptoms and how to avoid infection

Pets are our friends and family members. But did you know that even a well-groomed dog or cat can carry parasites that are dangerous to humans?

We talk with internist Anna Płaczkiewicz about why it's worth deworming not only your pets, but also yourself.

Doctor, is it true that if you have a dog or cat at home, it is also worth deworming… yourself?

The answer is yes, in many cases it's worth considering preventative deworming for people living with animals. We deworm our pets, but we don't give much thought to deworming ourselves. Parasites that dogs and cats can infect us with are not a myth, but a real threat. A prime example is toxocariasis – a disease caused by the larvae of the dog or cat roundworm, which can lead to serious neurological and ophthalmological complications, and even blindness.

So even an animal that appears healthy can be a carrier of parasites that are dangerous to humans?

Exactly. Parasitic infections are very often asymptomatic – in both animals and humans. A pet can appear healthy, be well-groomed, and regularly vaccinated, yet still shed parasite eggs in the home environment: on its fur, in its feces, on the floor, or in its bedding. This is especially true for outdoor animals, but even an indoor cat can become infected with roundworms if, for example, the owner brings in parasite eggs on their shoes.

What parasites are most often transmitted from animals to humans?

Primarily, roundworms, namely Toxocara canis and Toxocara cati, can enter the human body through accidental ingestion of roundworm eggs (which are excreted in feces), eating with dirty hands, contact with soil or sand contaminated with animal feces (e.g., in sandboxes, city squares and parks, home gardens, and children's playgrounds), or eating unwashed vegetables or fruit. Their larvae can migrate throughout the body and cause serious complications, from liver lesions to retinal damage. Tapeworms, such as Dipylidium caninum, transmitted by fleas, and protozoa such as Giardia lamblia, which are responsible for troublesome intestinal infections, are also dangerous.

Which groups of people are most at risk of infection?

Definitely children – because they play with their pets on the floor, put their hands in their mouths, and often share beds with dogs or cats. But also the elderly, pregnant women, immunocompromised patients, and people with chronic illnesses. In them, any parasitic infection can be more severe and lead to complications.

What symptoms should worry us?

Parasitic infections are often asymptomatic, but may include abdominal pain, chronic fatigue, perianal itching, diarrhea, constipation, skin lesions, and weight loss. Children typically experience chronic abdominal pain and a significantly reduced appetite, which may be associated with a lack of weight gain or even weight loss. Various rashes, usually diagnosed as allergic, may also occur. In allergy sufferers, Toxocara can exacerbate allergy symptoms, such as atopic dermatitis or bronchial asthma. Children without a history of allergies may develop symptoms (rashes, cough with shortness of breath) suggesting this possibility. In such cases, diagnostic testing is recommended.

What tests are most effective?

The basic test is a stool sample for parasite eggs, preferably three times. If giardiasis is suspected, Giardia antigen testing should be performed. Serological tests, such as for toxocariasis, can also be performed. In individuals with general symptoms, a complete blood count with an eosinophil count can also be helpful – elevated levels may indicate a parasitic infection.

Are there any recommendations on how often dog and cat owners should deworm themselves?

There's no set schedule, but for dogs and cats, preventative deworming is recommended every 6–12 months, especially if there are children in the household. It's also a good idea to do this if your pet is found to have parasites.

What about prevention? Is hygiene enough?

Hygiene is essential! Washing your hands after playing with your pet, cleaning their bedding, vacuuming carpets, bathing them regularly, and protecting them from fleas. But hygiene is no substitute for deworming—these elements must work together.

Finally, what is the most important advice you would give to families with pets?

First, deworm your pets regularly – every 3 to 6 months. Second, take care of their health: consider checkups and preventative care not only for your children but also for yourself. Third, practice good hygiene. And most importantly, love your pets, but do so wisely. Their presence is a tremendous value, but also a responsibility.

Thank you for the interview