This link is not for the squeamish or easily offended.
Canine/feline parasitic worms can and do cause disease in humans. Parasitic infestations are a serious problem in undeveloped areas of the world. Much less so in the US as adequate sanitation is standard. I haven’t found a good source for estimates of US infestations but a CBS report dated May 8 2014 says:
Approximately, 13.9 percent of the U.S. population has antibodies against this parasitic infection. Sadly, the rest of us are at risk for for acquiring it through roundworms often found in the intestines of dogs and cats. About 14 percent of Americans have had exposure to toxocara, and at least 70 people die from the infection each year. According to the CDC, most of the infections are in children and many suffer blindness due to related eye disease.
Still looking for that study.
The most dangerous condition to come from human Toxocaria (roundworm) parasitic infestation is Visceral larva migrans. Significant long-term complications from VLM include blindness/worsened eyesight, encephalitis, cardiac arrhythmia and difficulty breathing. Though rare the condition can be fatal.
I can present many more studies and articles regarding the impact of helminth infestations on human populations but I doubt anyone wants to read too many of those (yes, I’m weird that way.)
An ounce of prevention, as they say, is worth a pound of cure. Helminth infestations in animals are easily eradicated and prevented when the effort is made. In GARD’s case, the absurd lie of “cyclical” worm infestations in dogs is intended to relieve GARD of the expense and effort necessary to eliminate and prevent infestations in the animals they take to stores and sell to unsuspecting people, many with young children who are most likely to contract parasitic infestations from those animals.
It’s reprehensible behavior but what I’ve come to expect out of GARD.