Based on an article that first appeared at

I got a text from my neighbor this morning, asking me if I could get her into the clinic later today, as she suspected her kitten has worms.  My neighbor has a wonderful family, doting husband, 4 great children, 2 of which are toddlers.  She also is a responsible and loving pet owner to a one year old cat.

I texted her neighbor back, letting her to that she should call the clinic, let the receptionist know she is my neighbor, and that we would get her in today without delay.  I let her know that it would not be wise to delay having her cat seen, as some worms can pose a danger to her little ones.  At this, she was shocked and became nervous that her youngest children may be at risk.  She quickly stopped over and showed me one of the worms, but it was so dried out that I could not definitively ascertain the type of worm it was.

My intention certainly was not to panic my neighbor, nor was my intention in writing this post to panic my readers.  However, it occurred to me that if my neighbor, a responsible, dedicated, and well informed mother and pet owner was not aware that parasites in her cat could pose a danger to her children, how many other parents and pet owners may be unaware of this potential danger.

Generally speaking, parasites tend to be species specific, that is, they can only complete their lifecycle, and therefore reproduce, within the definitive host animals they have evolved to thrive in.  There are many exceptions to this general statement, as dogs and cats, separate and distinct species from one another, share many parasites in common.  Also, even though most parasites cannot complete their life cycle with an animal that is not their host species, they can often reach a stage of development that still poses disease potential for non-host animals…including people.

Roundworms are one of the most common worm parasites found in dogs and cats.  They pose little to no danger to healthy adult humans, but in immune compromised individuals, children under 5, and the elderly, they can reach a stage of larval development that may migrate through the body.  Migration through the skin can cause serious skin rashes that lead to itchiness, infection, and pain.  The most dangerous and potentially tragic consequence of roundworm infection in people is when migration occurs into the eyes can cause irreversible blindness.

There are many species of tapeworms that we commonly see in veterinary medicine that can be transmitted by several different species.  One of the most common types of tapeworms we see dogs and cats, dipylidium caninum, is carried in the gut of the flea, infecting dogs and cats when an infected flea is ingested during routine grooming.  A person can become infected by accidental ingestion of an infected flea that came from the animal.  It may seem a silly notion that a person could accidentally ingest a flea, but insect ingestion while sleeping occurs far more commonly than any of us would care to think about.  For those that allow their pets to sleep in bed with them, they have the biggest likelihood of accidental ingestion of a flea.

Luckily like the roundworm, canine and feline flea tapeworms pose little to no threat to healthy adults, but immune compromised people, children under 5, and the elderly can experience mild to severe GI symptoms if infected.

Lastly, hookworms, another commonly diagnosed worm parasite in dogs and cats, can infect people by an early larval stage passing through their skin.  Hookworm eggs are passed through the feces of a canine or feline and can hatch into an early stage of larvae that can penetrate a person’s skin.  Thus, the most common mode of hookworm transmission to people is walking barefoot in grass where dogs and cats have passed stool.  Direct contact with the stool may not be necessary as the infective larvae can live in the stool well after the feces have been picked up and discarded or washed away.

What makes hookworm different from the aforementioned parasites is that age or immune status does not as significantly affect its ability to infect a person.  Once in the body, hookworms commonly cause hallmark itchy, often painful skin rashes whose distinctive pattern is usually recognizable to a human dermatologist.

In cases where the hookworm parasite eggs or larvae are accidentally ingested, such as when a child may be playing in contaminated dirt or perhaps a contaminated sand box, the larvae can reach a state of development where they may latch onto the walls of the GI tract, causing GI upset and even bleeding.

Again, the purpose of this post was not to create mass hysteria and make people fear pet ownership and fear their pets.  Overall, incidences of human infection from canine and feline parasites remain uncommon, especially viewed in comparison to the high numbers of infected pets we treat every day.  However pet owners should be aware that there are more than just health consequences for their pets if infected with intestinal parasites, but it can also place the human family at risk as well, especially its most vulnerable members.  What’s more, these parasites are all very preventable.

Here are some tips to help you protect your family from canine and feline parasites:

1.) Do not allow young children, immune compromised family members, or the elderly to come in close contact with puppies or kittens until they have had stool screening and broad spectrum deworming by a veterinarian.

2.) In any case of pet diarrhea or vomiting lasting more than 24-48 hours, a veterinary visit should be scheduled with a stool sample brought in for analysis.  Parasites remain among the most common causes for pet GI disturbance.

3.) Engage in good potty patrol: do not leave stool on the ground for prolonged periods of time, as this increases the potential for human contact and contamination of the soil with parasite eggs and larvae.  This is especially true when a pet has diarrhea or under treatment for a parasite.

4.) Engage in at least yearly stool screening that most veterinarians recommend as part of a routine well visit…even if the pet is asymptomatic.  Pets do not always show symptoms of parasite infestation, thus, we find pets positive for parasites on routine stool analysis every day.

5.) Treat all dogs and cats with monthly flea prevention, even if you do not see fleas.  Infestations can break out at any time, with one female flea being capable of making 3000 new fleas in one month’s time.  If pets are fastidious groomers, flea populations can exist in the environment that go under pet owner radar.

6.) Give strong consideration to newer generation “all in one” monthly preventives that kill fleas, heartworm, and multiple species of intestinal worms, such as Trifexis in dogs and Revolution for cats.

Dr. Roger Welton is the President of Maybeck Animal Hospital and CEO/Chief Editor of the veterinary information and blog online community, Web-DVM.