Establishing risk factors for nematode parasitism

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How many dogs are infected with gastrointestinal nematodes on average in the United States? Are there any risk factors for nematode parasitism? A recent study in the Journal of the American Veterinary Medical Association reviewed the electronic records of 1,213,061 dogs that had undergone at least one fecal flotation test looking for Ancylostoma, Toxocara, and Trichuris species nematodes from January 2003 to December 2006 at 547 Banfield practices located in 44 states. Overall, when examining the results of the first fecal test in each dog, 5.04% of dogs were infected with Toxocara species, 4.5% were infected with Ancylostoma species, and 0.81% were infected with Trichuris species. Over the course of entire study, 82.67% of the fecal test results that were positive for intestinal nematodes were positive for only one genus of nematode. Fecal test results that were positive for two and three genera of nematodes were 16.79% and 0.53% of the positive test results, respectively. The following risk factors were found:

Age-Dogs less than 6 months old were more likely to have Toxocara or Ancylostoma species infections than those more than 5 years old. On the other hand, dogs less than 6 months old were less likely to have Trichuris species infections than dogs more than 5 years old.

Weight-Dogs that weighed less than 11 lb (5 kg) also had a higher prevalence of Toxocara and Ancylostoma species infection than those weighing more than 52.8 lb (24 kg). And dogs less than 11 lb were less likely to have Trichuris species infections than dogs more than 52.8 lb.

Sex-Intact dogs of both sexes had a higher prevalence of all three intestinal nematodes than did neutered and spayed dogs.

Breed-Toy breeds were the least likely to have any of the three intestinal parasites. Mixed-breed dogs had a higher prevalence of infection with Toxocara and Ancylostoma species, and herding dogs had a higher prevalence of infection with Trichuris species.

Geographic region-Dogs living in the west south central region had the highest prevalence of infection with all three parasites, while dogs living in the mountain region had the lowest prevalence of all three parasites.

The prevalence of intestinal parasitism was low in this study compared with the results of previous studies. The researchers thought that their findings might be underestimations because, at the time of the study, fecal centrifugation (a more sensitive testing method) was not used in the practices.

Mohamed AS, Moore GE, Glickman LT. Prevalence of intestinal nematode parasitism among pet dogs in the United States (2003-2006). J Am Vet Med Assoc 2009;234(5):631-637.

Link to abstract: http://avmajournals.avma.org/doi/abs/10.2460/javma.234.5.631