101 - Giardiasis

Abstract

•Cause: Giardia duodenalis (multiple genetic assemblages); a flagellate protozoan (phylum Sarcomastigophora).•First Described: Trophozoites that were likely Giardia spp. were first described in 1681 by Antonie van Leeuwenhoek and the genus was established in the early 1900s. Infections of dogs and cats were first described in the 1960s.1,2•Affected Host Species: Dogs and cats are the definitive hosts for several different Giardia assemblages and pass either trophozoites (diarrhea) or cysts (diarrhea or normal stool) in feces.•Intermediate Hosts: Although there are no intermediate hosts, there are multiple potential transport hosts that may carry Giardia spp. cysts and indirectly infect dogs or cats.•Route of transmission: Fecal-oral.•Geographic Distribution: Worldwide.•Major Clinical Signs: Most dogs and cats harbor subclinical infections. Acute watery diarrhea that can contain mucus can occur. Steatorrhea can be observed. Chronic or intermittent diarrhea and weight loss may be noted in animals with concurrent infections or immunocompromise.•Differential Diagnoses: All causes of small bowel diarrhea including Cystoisospora spp., Cryptosporidium spp., bacterial infections such as salmonellosis, nematode infections, dietary intolerance, exocrine pancreatic insufficiency, and inflammatory bowel disease.•Human Health Significance: Giardia duodenalis assemblages that infect dogs (assemblages C and D) or cats (assemblage F) are usually not associated with clinical disease in humans but can be detected in the feces of immunocompromised people.3 Human assemblages A and B can be found in feces of dogs and cats when animals share human environmental features (such as contaminated water). However, it is unlikely that new human infections with G. duodenalis assemblage A or B infections are acquired from the feces of dogs or cats.