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Neospora Caninum

Disclaimer: I am not a veterinarian - the following information is based on my understanding of this disease as a layperson. Please talk to your veterinarian with any questions regarding your dog's health and wellbeing.

What is Neosporosis?
Neosporosis is a neuromuscular disease, caused by Neospora caninum a coccidian parasite, similar to Toxoplama gondii. Puppies and adult dogs can be affected, there have been no known cases in humans.

How are dogs infected?
The lifecycle of Neospora caninum involves two hosts. A dog eats infected tissue (e.g. raw infected meat) containing Neospora caninum tissue cysts and is infected with the parasite. The parasites reproduce in the intestine of the dog, oocytes (spores) being passed in the feces, contaminating food and water. These oocytes are then eaten by an intermediate host (e.g. cow or sheep), where they travel to the intestines and reproduce, migrating to other body tissues including those of any fetus. Infection with Neospora caninum causes abortions, stillborn young, or normal looking young that have a life long infection. These animals if bred can infect their offspring. Infection can occur through successive breedings. Dogs can also transmit Neospora caninum, infecting multiple litters of puppies. Not all puppies in a litter will be infected, and of those infected, not all will show clinical signs. The lifecycle is completed when infected tissue from an intermediate host is eaten by a dog.

What breeds of dog are affected and at what age?
Neospora caninum affects any breed of dog. It can be seen in adult dogs and puppies, with puppies showing signs as early as two to three weeks of age.

What are the signs that a dog may be infected?
The first signs seen often involve changes in the hindlimbs. One or both limbs may be affected. Dogs may have muscle atrophy and stiffness that gradually leads to paresis (partial paralysis), rigid hyperextension, and paralysis. Paralysis can be ascending, affecting the forelimbs as well as the hindlimbs. Untreated, dogs develop dysphagia (difficulty eating/swallowing) and often die. Infections in older dogs are less common. Signs in adults include hepatitis, myocarditis, seizures, ataxia and paresis. Dogs typically remain bright, alert and responsive as the disease progresses.

Can other diseases result in the same or similar signs?
Yes. The same signs may be seen in cases of trauma, intervertebral disc disease (IVDD), toxoplasmosis, distemper, neoplasia, and other muscle and nervous system diseases.

What tests are available?
Diagnostic testing often starts with bloodwork (complete blood count and chemistry profile), radiology and cerebrospinal fluid analysis. Blood may also be sent for serological testing, and tissue for immunohistochemistry. A definitive diagnosis of Neospora caninum is based on finding cysts in tissue or cerebrospinal fluid, however a dog can be assumed to be infected if it has clinical signs with positive serology or antibodies found in the cerebrospinal fluid. It should be noted however that some infected dogs will test negative.

Will my dog be OK?
According to one author (Barber, 1998), 50% of treated dogs will make a full recovery. Others may be left with an unusual gait or may be roachbacked. Prognosis is poorer for dogs with neurologic signs, and dogs with rigid hyperextension are unlikely to see changes to their hindlimbs.

References:

Dubey J.P., Neosporosis in Dogs, 30th World Congress of World Small Animal Veterinary Association, Mexico City, 2005, May.

Barber J.S.,Canine Neosporosis, Waltham Focus, Vol 8 No 1, 1998