Amoebic Infections in Dogs

Amoebae

are fascinating single-celled organisms in the Protozoa genus, although this fact isn’t something your dog will appreciate if they infect him.

Amoebae are one of the simplest forms of life, consisting of a cell, a bit like a tiny sack of gel, that doesn’t have a fixed shape. In fact, the name comes from the Greek word amoibe

, which means “to change shape.”

This parasite’s main hosts are people and primates. Dogs pick up the infection by accident, often after contact with infected feces.

Unfortunately for dog families, the bug can be passed from dog to human in what is known as a zoonosis (animal-to-human infection). If you suspect your dog has an amoebic disease, seek veterinary advice immediately to decrease the risk of becoming ill yourself.

Symptoms

If a dog catches an amoebic infection, he may not show any signs of ill health, but he can still become a carrier who sheds the infection and is a risk to others.

It is wise, therefore, as a general rule and not just because of amoebic infections, for families to wash their hands thoroughly after handling their pet, and especially before eating.

The signs most commonly linked to amoebic disease are gut-related. The amoebae invade the gut lining, causing inflammation and ulcers expressed as stomachs cramps and bloodstained, watery diarrhea

. Over time, the poor dog loses weight and his coat becomes dull.

In rare cases, a form of blood poisoning can develop through amoebic infection, which can then lead to organ failure.

Types of Amoebic Infection

There are 2 types of amoebic infection -- entamoeba and acanthamoeba -- that can cause illness, and each has subtly different signs. Entamoeba symptoms: Stomach cramps Watery diarrhea with blood Weight loss Poor coat Organ failure (in extreme cases) Acanthamoeba (very rare) symptoms: Lack of energy Poor appetite Heavy breathing Seizures Head-pressing Dull mental state Eyes flicking from side to side

Causes

Amoebae need a moist environment in which to survive. Those that cause illness in dogs are actually human parasites, and dogs are accidentally infected. The 2 types of amoebae either thrive in human feces (entamoeba) or stagnant bodies of water (acanthamoeba).

Dogs pick up the infection by licking or breathing in infected water, feces or contaminated sewage. The amoebae then develop in the bowel wall, where they reproduce, and more parasites are then passed through the feces, posing a risk to other dogs as well as people.

Diagnosis

The diagnosis of amoebic infection is most commonly made by examining fecal samples. The amoebae are shed intermittently; the lab usually requires 3 samples pooled together to reduce the chances of a false-negative test.

More sophisticated tests include sending small samples of the bowel wall away for histology (examination under the microscope) to look for amoebae embedded in the tissue.

A diagnosis of acanthamoeba is more difficult than entamoeba because it is locked away inside the brain or central nervous system. Testing the cerebrospinal fluid (or CSF, which bathes the spinal cord) for changes consistent with meningitis can help, as can an MRI brain scan to look for thickening linked to protozoan infections.

Treatment

A course of the antibiotic metronidazole

is usually effective against entamoeba. This infection often goes hand in hand with other parasitic conditions such as giardia and salmonella.

Make sure your vet screens for other parasites and treats them all.

Prevention

Good hygiene plays a vital role in preventing infection. The parasite thrives by being passed from animal to animal via feces, and loves conditions where lots of dogs are kept together in poor sanitary conditions.

A simple preventive tip is to clean feces up promptly

so other dogs can’t sniff or eat them. Also, families should always wash their hands after handling their pet, especially if the dog has an upset tummy.

Reference

• Clinical Medicine in the Dog and Cat. Michael Schaer. Publ: Manson Publishing.

This pet health content was written by a veterinarian.