Epidemiology of Giardia species infection among dogs in the United States (2003 - 2009) risk factors, time-series and spatial analysis
Abstract
Giardia species infections have gained a substantial amount of attention lately in light of the recent changes in the taxonomy of this protozoan. The recent taxonomy of Giardia divides G. duodenalis into eight assemblages (A-H), most of which are fairly host specific. Assemblages A and B however have been found to infect domestic and wild animals including dogs, and are considered to be zoonotic. Studies of giardiasis in dogs in the United States have been largely limited to small geographic locations or selected populations. The objective of this research was to (1) characterize the patient risk factors of Giardia among dogs, (2) describe and compare its temporal characteristics including seasonality among dogs and humans, using a large sample of dogs from over 700 veterinary hospitals and human surveillance data in the United States from 2003 through 2009, and (3) to describe its geographic distribution, clustering, and association with water sources in high risk area(s) for the same period. A logistic regression model defined high risk groups by age, sex, breed, and region. Additionally, dogs from the states of Colorado and Maine were at highest risk of Giardia infection. Time series analysis revealed that canine incidence of Giardia declined steadily from 2003 through 2009 with a weak and irregular seasonal pattern, whereas human incidence over the study period remained stable with a strong, regular seasonal pattern. The peak seasons of human giardiasis were during the summer and fall, potentially coinciding with increases in outdoor activities and travel. These findings suggest that underlying processes of giardiasis in humans and dogs are different and that zoonotic transmission is minimal. A spatial analysis, using data in the state of Colorado, was conducted and concluded that Giardia prevalence among dogs in this state was substantially higher in Grand Junction, Mesa County. No significant associations between canine giardiasis and water treatment source could be demonstrated in the state of Colorado in the study period.
Degree
Ph.D.
Advisors
Moore, Purdue University.
Subject Area
Parasitology|Epidemiology|Veterinary services
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