Toxoplasmosis in Dogs

Sad brown dog lying down on floor
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Toxoplasmosis is a disease process that may be more familiar to cat owners than dog owners. That doesn't mean dogs aren't at risk for infection, though. Thankfully, steps can be taken to not only prevent your dog from contracting the disease, but to treat it as well.

What is Toxoplasmosis?

Toxoplasmosis is the disease process that is caused by a protozoal (that is, single celled) parasite called T. gondii. This parasite can infect any warm-blooded animal, including dogs, cats, and people. Although dogs can become infected by this parasite, they are not the definitive host. When a T. gondii organism infects a dog it cannot complete its life cycle but it can still cause a generalize infection as it spreads throughout your dog's body.

A dog becomes infected by T. gondii when it eats another animal that was infected or when it eats stool from an infected cat. Once the parasite enters the dog's gastrointestinal tract, it replicates by cloning and then migrates from the GI system and spreads throughout the dog's body. The replicated clones will cluster together in cysts in various tissues and organs. An infected dog cannot spread the parasite through their stool.

Symptoms of Toxoplasmosis

Since the parasite can spread and encyst itself anywhere throughout the body, the symptoms of infection are varied and depend entirely on where the parasite ends up.

Signs of Toxoplasmosis in Dogs

Depending on where in your dog the cysts form, you may see any of the following in any combination:

  • Fever
  • Vomiting
  • Diarrhea
  • Abdominal pain
  • Cough/difficulty breathing
  • Jaundice
  • Seizures/tremors/uncoordinated gait/other neurological symptoms
  • Depression
  • Lethargy
  • Muscle weakness
  • Partial or complete paralysis
  • Loss of appetite/weight loss
  • Eye infections/inflammation

Can You Get Toxoplasmosis from Your Dog?

Toxoplasmosis is zoonotic and something that people can contract, but because dogs are not definitive hosts and cannot shed any parasite, rest assured that you cannot contract it from your pup. People most often contract the parasite from consuming infected, raw or undercooked meat and from not washing up after gardening. If you also have cats, you should be aware that cats, unlike dogs, are able to shed the parasite in their stool. So good hygiene habits should be taken when cleaning out the litter box to avoid contracting the parasite from your cat.

How to Diagnose Toxoplasmosis

A diagnosis cannot be made from presenting symptoms alone. This is partly because the GI signs from an acute infection are generic symptoms that could be signs of a myriad of other illnesses and partly because signs from a chronic infection will vary depending on where in the body the parasite migrates and encysts. Instead, a definitive diagnosis is made based on a variety of lab work including urinalysis, blood work, spinal taps, and serological tests that will look at the level of Toxoplasma antigens. Bloodwork may show abnormally low numbers of white blood cells (including neutrophils and/or lymphocytes), abnormally high levels of the liver enzymes ALT and/or AST, and in some cases abnormally low levels of albumin. A urinalysis may show abnormally high proteins as well as the presence of bilirubin. Serological testing can also determine if an infection is acute or chronic and whether an infection is active or dormant.

Treatment

Although toxoplasmosis can cause clinical disease, most dogs have a robust enough immune system to prevent the cysts from causing any harm. In these instances, treatment isn't necessary. If your dog does start to exhibit symptoms, though, your vet will prescribe a course of antibiotics. Anticonvulsants may be prescribed if your dog does start suffering from seizures. If your dog becomes debilitated from toxoplasmosis your vet may want to hospitalize for IV fluid therapy and intravenous medications.

How to Prevent Toxoplasmosis

For dogs that have limited exposure to cats or cat litter boxes, T. gondii is most often transmitted through the ingestion of raw or undercooked meat. Try to prevent your dog from hunting or scavenging wild animals as much as possible. If you are interested in feeding your dog a raw diet, there are commercial freeze-dried brands and varieties that undergo a process called high pressure pasteurization. This is a process that kills any potential pathogens within the food without actually cooking it. If you give your dog fresh fruit or vegetables as a treat or as part of a home-made diet, ensure that they are properly washed before feeding.

If your dog shares their home with a cat, you may already be aware of the difficulty in keeping your cat's litter box inaccessible to the dog. Cat stool that contains the parasite isn't immediately infectious, though. It needs to sporulate over the course of several days before the parasitic eggs within are capable of causing infection. Cleaning the litter box on a daily basis can protect your dog from ingesting infectious stool.

Although toxoplasmosis is a disease process that is more often associated with cats, it is something that can effect dogs as well. With proper preventative steps and treatment, though, it is not a disease process that dog owners need to lose sleep over. Talk to your vet about the risk factors that may be effecting your dog and the steps you can take to limit them.