Toxoplasmosis In Dogs

Toxoplasmosis (Toxo) is an infectious, cross-species or zoonotic disease, that occurs in both dogs, cats, and other warm-blooded animals and is transmissible to humans. Protected from illness by their healthy immune systems, over 60 million people in the U.S. are infected and don't even know it. Caused by the most prevalent parasite worldwide — a single-celled protozoan named Toxoplasma gondii found in raw and undercooked meat, especially pork or lamb, soil and cat feces — toxoplasmosis invades the tissues and damages the brain in those dogs who are vulnerable.

Veterinarian doctor examining a Maltese puppy
credit: BrianAJackson/iStock/GettyImages

The three types of toxoplasmosis: acute, fetal, and chronic.

Acute toxoplasmosis can be fatal if left untreated in puppies and young dogs with undeveloped immune systems or dogs who have weakened or impaired immune systems.

Pregnant female dogs who ingest the organism will infect their unborn pups with fetal toxoplasmosis through a transplacental transmission which occurs when the parasite multiplies in the placenta, then infects the fetuses which are either stillborn or die shortly after birth.

Mature dogs with strong immune systems may show no sign of illness even after they are affected, and some are able to contain the infection and often eliminate it. Otherwise, it may remain in the dog's system as asymptomatic clusters of organisms called bradyzoites, just one of the structures of the parasite's complex life cycle, for months or years.

Toxoplasma test
credit: jarun011/iStock/GettyImages

How do dogs get toxoplasmosis?

Dogs do not transmit toxoplasmosis. Members of the cat family, both wild and domestic, are the only definitive hosts for Toxoplasma gondii with a wide range of intermediate hosts such as livestock, wildlife, birds, and people. Definitive means that only when the parasite infects a cat will it produce oocysts (eggs). The organism will not produce eggs in intermediate hosts.

In an affected cat, the parasites completes their life cycle in the cat's intestinal tract and pass back into the environment through the cat's feces as sporozoites, which is the infectious spore-like stage of toxoplasma gondii.

How to prevent toxoplasmosis in dogs.

Dogs contract toxo by ingesting infected cats' feces deposited outside in the soil by feral or roaming cats, or inside the home if they have free access to a cat's litter box. Supervised, or leashed walks help you monitor where your dog digs, and you can stop him when he tries to eat something nasty. In the home, litter boxes should always be out of reach of your dog. Place boxes behind closed doors of laundry or utility rooms and install cat doors or use baby gates as barriers for other small rooms. Wear disposable gloves while cleaning the litter box and remove solid waste every day.

The longer the feces sits in the box, the more opportunity the parasites' eggs will have to become infectious. Cover outdoor sandboxes accessible by your dog so that neighborhood cats don't use them as litter boxes.

Woman wearing a gray spaghetti strap cleaning the blue little box or cat toilet, feeling stinky
credit: catinsyrup/iStock/GettyImages

Dogs may also be at risk for toxoplasmosis from eating raw or undercooked meat where the toxoplasma gondii parasite is in the tissue cyst or bradyzoites life stage, one of the three infectious stages of toxoplasmosis. The organism invades the lining of the stomach and lower intestine and rapidly spreads throughout the dog's body. To prevent infection, feed a diet of commercial kibble or canned wet food, freeze raw meat at sub-zero (0-degrees Fahrenheit) temperatures for several days before feeding, or for home-cooked meals, avoid using pork or lamb, and cook other meats and poultry to the USDA recommended minimum safe internal temperatures of 160-degrees Fahrenheit for beef — chicken or turkey should be 165-degrees Fahrenheit.

Other ways your dog may become infected by the parasite is through eating infected rodents, birds, and other animals or drinking feces-contaminated water in the environment. Keeping a close eye on your dog when walking through parks or fields and keeping him on-leash allows you to limit his access to these possible sources of toxoplasmosis.

Signs and symptoms of acute toxoplasmosis.

Cats are more likely to present with symptoms of toxoplasmosis, but the following signs or symptoms may also be seen in dogs. Keep in mind that several symptoms of toxoplasmosis may be seen in other diseases, for example, canine distemper or rabies.

  • Vomiting
  • Diarrhea
  • Tremors
  • Shortness of breath
  • Fever
  • Weight loss
  • Refusal of food
  • Inflammation of the eyes
  • Neurological symptoms
  • Depression
  • Lethargy
  • Muscle weakness
  • Diarrhea
  • Coughing
  • Difficulty breathing
  • Uncoordinated gait
  • Jaundice
  • Seizures
  • Partial or complete paralysis
  • Abdominal pain
  • Inflammation of the tonsils (tonsillitis)
  • Inflammation of the retina (retinitis)
  • Inflammation of the middle part of the eye including iris (uveitis)
  • Inflammation of the cornea (keratitis)
  • Death
dog muzzle close up portrait.
credit: Fly_dragonfly/iStock/GettyImages

Diagnosis of toxoplasmosis.

Your veterinarian will do lab tests on your dog's blood, spinal fluids, and feces to definitively diagnose toxoplasmosis.

Toxoplasmosis treatment, prognosis, and recovery.

Veterinarians will typically prescribe antibiotics if treatment for toxo is warranted. In many cases, treatment is not necessary. There is no treatment currently available for chronic and fetal toxoplasmosis. For acute toxo in immunosuppressed dogs and puppies, anticonvulsant medications are prescribed to control seizures. If a dog is severely dehydrated or debilitated by the infection, fluids and other medication may be given intravenously. Some medications frequently used are sulfadiazine and pyrimethamine, which suppress active multiplication of the parasite. Another commonly prescribed medication is Clindamycin.

Toxoplasma test
credit: jarun011/iStock/GettyImages

Time is of the essence, and if your young dog is taken to the veterinarian as quickly as possible after consuming infected meat, the odds are good he can make a full recovery from the disease.

Recovery from acute toxoplasmosis is often supported with IV fluids and other measures designed to keep your dog as healthy as possible as he battles the infection. During her recuperation, avoid contact with other animals and ensure your dog gets plenty of rest.