A recent report on the prevalence and impact of toxocariasis in the U.S. is a reminder of the veterinarians obligation to help people see the connection between animal health and human health.
"All veterinarians should view themselves as public health veterinarians." -Dr. Jenifer Chatfield (Shutterstock.com)Millions of children in the U.S. have been exposed to a parasite that can cause respiratory, vision, liver and cognitive problems, according to a New York Times article, “The Parasite on the Playground.” Yet awareness of this issue in the public and among human medical professionals remains low. How can that be?
The parasitic culprits in question are Toxocara canis and Toxocara cati. Infected dogs and cats shed Toxocara eggs in their feces, which can easily find their way into the hands (and, eventually, mouths) of children playing in contaminated playgrounds and backyards, the Times article explains. Once ingested, the eggs hatch and release larvae into the body, where they can find their way into various organs, such as the liver, eyes and brain.
Though children are the focus of the Times piece, it includes data to show that they aren't the only age group affected. According to the results of the National Health and Nutrition Examination Survey from the Centers for Disease Control and Prevention published last year in PLoS Neglected Tropical Diseases, an estimated 5 percent of the entire U.S. population (roughly 16 million people) have Toxocara antibodies in their blood. Still, research on and interest in toxocariasis is lacking. Why aren't these roundworms a household name?
The Times article offers a couple of possible explanations. First, the infection rate is higher among African Americans (7 percent) and those living below the poverty line (10 percent). “If this were a disease of wealthy kids in Brookline, Massachusetts, and Bethesda, Maryland, and Westchester, New York, we'd be all over it,” says Peter Hotez, MD, PhD, dean of the National School of Tropical Medicine at Baylor College of Medicine in Houston, in the article.
A recent survey of 21 New York City playgrounds found Toxocara eggs in nine of them, the article reports. Seventy-five percent of Bronx playground samples contained larval-stage eggs (which are more infectious). No larval-stage eggs were found in Manhattan playgrounds.
The second reason offered: Infected individuals often don't have any symptoms-or at least ones that are easily recognized by physicians.
“Nobody is dying here,” says Dr. Hotez in the article, “but it is potentially causing developmental delays that are affecting quality of life [by infecting and affecting the central nervous system], and the economic impact is far greater. It could trap children in poverty.” Which, of course, is more difficult to prove and quantify, though a 2012 study published in the International Journal for Parasitology reported that children seropositive for Toxocara scored significantly lower on intelligence and achievement tests, even after accounting for ethnicity, gender and socioeconomic status.
One person not surprised by both the prevalence of Toxocara and the ignorance surrounding it: Jenifer Chatfield, DVM, DACZM, the staff veterinarian at 4J Conservation Center, an instructor for FEMA/DHS courses, and a regional commander for the National Disaster Medicine System Team.
“Zoonotic diseases aren't typically at the top of a differential list for most human physicians,” she says. “When was the last time your doctor asked you about your contact with animals? Or your kid's pediatrician asked about your child's contact with animals? Though pets continue to climb the social ladder and become more integrated into the lives of their owners, human medicine remains largely oblivious.”
Dr. Chatfield doesn't let veterinarians off the hook, however: “While stray, feral and free-roaming dogs are no longer viewed as acceptable by communities, stray, feral and free-roaming cats seem to be rising in population and popularity. These cats may receive some vaccinations, but they aren't typically receiving a monthly dewormer and can be sources of zoonotic disease transmission,” she says.
Dr. Chatfield is active in her state's veterinary medicine association and uses it as a vehicle for reaching out to local medical societies to educate human doctors on the impact of zoonoses on their profession and the community as a whole.
“It never fails that if I'm talking about zoonotic diseases from companion animals, such as toxocariasis, toxoplasmosis, tick-borne disease and cat scratch disease, the ophthalmologists in the room will come up after my lecture and tell me that they're seeing these diseases every day and that they're so glad someone's talking about it,” says Dr. Chatfield.
Dr. Chatfield describes the veterinarian's role as “helping clients understand how to live safely with the animals they love.” She urges veterinary professionals to talk about the connection between pets and human health during every exam.
If you aren't sure where to start, you can borrow one of Dr. Chatfield's lighthearted approaches: “I sometimes begin with something like, ‘I strongly recommend that you and your kids avoid eating your pet's poop, but let's remember I'm not just talking about the times you know you're doing it,'” she says. “Help your clients be cognizant of how they can unwittingly be exposed to zoonotic parasites and how to safeguard themselves. Such conversations are especially important if the client has small children.”
This includes encouraging hand washing after touching animals, after spending time outside and before consuming food. Dr. Chatfield also urges parents to talk to their children about avoiding strange animals (although some parents might need to give themselves that same speech), and encourages pet owners to keep their pets contained (in a home or yard and on a leash)-including cats. This naturally leads into a discussion on the importance of preventives. Monthly deworming medication is recommended along with heartworm, flea and tick preventives. “Regular deworming is especially important for young pets, as well as those that are particularly active and social,” says Dr. Chatfield.
The key is to stress that the pet's health can have a direct effect on the health of the client and the client's family. “All veterinarians should view themselves as public health veterinarians,” says Dr. Chatfield.