Canine Schistosomiasis

Protect your pup! Watch out for areas of vegetation in the water at Lake Mead NRA, Galba humilis could be hiding in those shrubs.

NPS Photo

 

Canine Schistosomiasis or Heterobilharzia americana (HA) was recently identified in raccoon feces within Lake Mead National Recreation Area. The presence of the intermediate host, Galba snails, further indicates the potential for disease transmission within the park.

H. americana is a parasitic flatworm that infects mammals, most commonly raccoons and dogs. While historically limited to the Gulf Coast and southeastern U.S., HA has recently been detected along the Colorado River in southern California, western Arizona, and now there is evidence the parasite is within Lake Mead National Recreation Area.

While evidence of HA has been found within park boundaries, there are currently no reported cases of dogs becoming ill after visiting Lake Mead NRA. The overall risk of infection is considered low, but dog owners should exercise caution and avoid allowing pets into freshwater areas with emergent vegetation. Dogs showing signs of illness should receive prompt veterinary evaluation and care.

 

Galba snails are most commonly found in areas with vegetation, like cattails, in the water.

NPS / R. Rackliffe

Source of Infection

• Dogs can become infected when swimming or wading in freshwater containing the parasite and its snail host (Galba species).
• The parasite is not spread directly between dogs.
• Parasite eggs in feces of dogs or other animals are not infectious.

 

Galba snails are hosts for Canine Schistosomiasis (Heterobilharzia americana).

C. Goldy at UC-Riverside

Illness in Dogs

• Most infections do not cause illness, but severe cases can cause systemic inflammation, organ failure, and death.
• Watch for signs such as lethargy, diarrhea, vomiting, increased thirst/urination, anorexia, and weight loss.

 

Diagnosis & Treatment

• Veterinary testing of fresh feces and bloodwork can confirm infection and determine disease severity.
• Treatment with anti‑parasitic drugs and supportive care may help, though effectiveness varies.
• Dogs remain vulnerable to re‑infection if exposed again to contaminated water.

 

This is an example of a cove with emerging vegetation that could be a home for the host snails.

NPS / R. Rackliffe

Prevention

• Best protection: Do not allow dogs to swim or wade in freshwater where HA is present. Current risk is considered highest in Lake Mohave near emergent vegetation and along riverbanks where more suitable habitats for Galba snails exist.
  • Areas around Lake Mead that HA can be present include: Virgin River, Muddy River, and the Las Vegas Wash.
  • Areas around Lake Mohave that HA can be present include: Colorado River below Davis Dam and surrounding coves.
• If exposure is unavoidable, monitor closely for illness and seek prompt veterinary care.

 

Public Health

• There is no risk of transmission from infected dogs or their feces.
• Heterobilharzia larva can cause swimmer's itch in humans, which is an unpleasant experience for people and clears up on its own. Meanwhile, in dogs exposure can on rare occasions cause death.
• Further information on “swimmer’s itch” caused by Heterobilharzia americana can be found on the Centers for Disease Control and Prevention website.