IN ANIMALS
AETIOLOGY AND EPIDEMIOLOGY • Dogs are primarily infected with Giardia canis (Assemblages C and D) which are canine host adapted. Cats are primarily infected with Giardia cati (Assemblage F), a feline adapted species. These species are not considered zoonotic. In addition to their host adapted species, both dogs and cats are susceptible to infection with G. duodenalis and G. enterica , which have a wide host range, including humans. 1,3 • Giardia has a simple two stage life cycle. 4 Trophozoites are the actively replicating stage that attach to the surface of the small intestine causing functional changes and damage to the intestinal villi. Trophozoites become encysted and are shed in faeces. Cysts are environmentally resistant and immediately infective after shedding. 4 • Ingestion of cysts leading to giardiasis and subsequent clinical signs is dependent on host factors (e.g. co-infections, age, sex, genetic predisposition, immune competence) and also agent factors (e.g. assemblage, production of proteolytic enzymes). 4,5 • The prepatent period ranges from 3-14 days in dogs and 5-16 days in cats. 6,7 Patency can persist for several weeks or months. Prolonged shedding is common and may be intermittent and inconsistent.
Scanning electron microscopic (SEM) image of Giardia spp. cyst undergoing “excystation”, with a flagellated trophozoite emerging from the right side of the cyst (Public Health Image Library, CDC)
PREVALENCE AND RISK FACTORS • Pooled global prevalence data for Giardia infection in dogs and cats from a recent meta-analysis was
15.2% and 12.0% respectively. 8 Studies conducted in Australia reported a prevalence of cyst shedding ranging from 3-50% in dogs 9-14 and 0-16% in cats. 9,11,13,14 High rates of faecal shedding
Life cycle of Giardia duodenalis
D.H. Dog and cat
Life cycle of Giardia duodenalis
Animals eliminate either trophozoites or cysts via faeces
Mature cyst
Trophozoite
Faeces
Humans ingest cysts shed by pets or, more likely, other humans
Faecal-oral transmission (contamination of food/water)
Mature cyst
D.H. = definitive host
Humans eliminate cysts via faeces
Extracted from the Textbook of Clinical Parasitology in dogs and cats, Beugnet F., Halos L., Guillot J., Ed Servet, 2018. Life cycles adapted from Pet Owner Educational Atlas. Parasites, Carithers D. and Miro G., Ed Servet, 2012. Life cycle from Beugnet, F., et al (2018) Textbook of Clinical Parasitology in Dogs and Cat. Grupo Asis Biomedica, S.L.; Adapted from Carithers, D., et al (2012) Pet Owner Educational Atlas.
CONTENTS
Companion Animal Zoonoses Guidelines 45
Made with FlippingBook - professional solution for displaying marketing and sales documents online