Giardia Statistics by State

Not every parasite in our state-by-state series follows the same map. Giardia — a microscopic intestinal parasite dogs pick up from contaminated water or feces, sometimes called "beaver fever" among hikers — spreads completely differently from mosquito-borne heartworm or tick-borne Lyme disease, and its geography shows it.

The figures below come from the Companion Animal Parasite Council's (CAPC) live Parasite Prevalence Maps: real canine giardia test results from veterinary clinics and labs nationwide, year-to-date 2026.

Canine Giardia Positivity Rate by State

Giardia is a microscopic intestinal parasite spread through contaminated water and feces — not by mosquitoes or ticks — and the Companion Animal Parasite Council's (CAPC) 2026 data shows a geographic pattern that looks nothing like heartworm or Lyme disease.

A Different Map: The Mountain West, Not the Southeast

Wyoming (9.38%), Arizona (8.57%), New Mexico (7.49%), Montana (7.00%), and South Dakota (6.96%) top the list — a Mountain West cluster that's almost the opposite of the states that lead our heartworm and hookworm data. In fact, the classic "heartworm belt" states run in the opposite direction here: Mississippi has the lowest giardia rate of any state (1.81%), and Louisiana, Arkansas, North Carolina, and Tennessee all sit in the bottom five.

This tracks giardia's actual transmission route. Unlike heartworm (mosquitoes) or Lyme (ticks), giardia spreads through drinking or contact with water contaminated by infected feces — streams, lakes, and other surface water sources dogs encounter while hiking or playing outdoors. States with more wilderness recreation, natural surface water, and dogs with off-leash access to streams and lakes — exactly the profile of Wyoming, Montana, and the wider Mountain West — see it more often, regardless of climate warmth.

What This Data Does and Doesn't Show

These are positivity rates among tested dogs, not the infection rate across each state's full dog population, and giardia testing often happens specifically because a dog has GI symptoms, which can skew results toward dogs already suspected of infection. Still, the geographic pattern here — concentrated in states with heavy outdoor/wilderness dog activity rather than in warm, humid climates — lines up with giardia's known water-based transmission route.

For general national pet health statistics, see our pet health statistics page.

The Big Picture

Giardia's map is essentially the inverse of heartworm's: Mountain West states with heavy outdoor and wilderness dog activity top the list, while the Deep South states that dominate every other CAPC map in this series — Mississippi, Louisiana, Arkansas — rank at the bottom. That's a useful reminder that "regional pet health risk" isn't one single map; it depends entirely on how a given parasite or disease actually spreads, and giardia's water-based transmission route points toward wilderness exposure rather than climate.