A recent paper in the journal Veterinary Parasitology (Upjohn et al 2010) described a study looking at Giardia infections in dogs in a central London shelter. The researchers collected a fecal samples from dogs within 1 day of arrival and tested them for Giardia.
- 21% of dogs were shedding Giardia on arrival at the shelter.
- Shedding rates were higher in younger dogs.
- Of the samples that were genotyped, almost all were Assemblages (types) C and D, the dog-specific types that are not thought to be able to cause disease in people.
This is one more study highlighting a couple of important facts about the protozoal parasite Giardia:
- Giardia is common and can be found in healthy and diarrheic dogs. Studies of healthy pet populations typically reported lower rates than the 21% found here, but it is not uncommon to find Giardia in approximately 7% of healthy pet dogs.
- Young dogs are more likely to be infected. That’s also true for various other intestinal microorganisms that can cause disease.
- The majority of dogs that are shedding Giardia are infected with types that do not infect people. This is an important point and it needs to be considered when people are worried about infections from dogs (or trying to blame pets for human infections). There is limited risk of transmission of Giardia from pets to people. That doesn’t, however, mean no risk. Since a small percentage of dogs can shed Giardia types that can infect people, common sense should be used when handling dog feces. Even if a zoonotic strain of Giardia is present in a dog’s stool, it has to make it to someone’s mouth to have a chance of causing an infection. Proper handling of feces and basic hygiene practices (especially hand hygiene) should greatly reduce the already low risks.