Introduction

• First recognized as a disease of dogs in Norway in 1984.
• Cause:Neospora caninum Neospora caninum similar protozoal parasite toToxoplasma gondii Toxoplasma gondii.
• Signs: typically paresis and mortality mainly affecting young dogs (but can produce a wide variety of signs in dogs of all ages).
• Diagnosis: serology, demonstration of parasites in tissues with specific staining. 5-17% of dogs in the UK are seropositive.
• Treatment: appropriate antibiotics.
• Prognosis: fair.
• Widespread cause of abortion in dairy cattle.
• No natural infections reported in cats or humans.

Pathogenesis

Etiology

• Protozoan parasite (N. caninum Neospora caninum ).

Predisposing factors

• Immunosuppression may re-activate subclinical infection.

Specific

• Administration of corticosteroids can exacerbate acute and chronic neosporosis.

Pathophysiology

• Ingestion of tissue cysts and tachyzoites may occur in dogs fed uncooked meat (beef) → rapid multiplication of tachyzoites → kills host cells → tissue cyst rupture → host reaction.
• Mononuclear cell infiltration into CNS and spinal nerves suggests immune-mediated pathology.
• Lesions include hypo- or demyelination and inflammatory response but exact mechanism of paralysis unknown.
• Immunosuppression may reactivate latent infection.
• N. caninumcan be transmitted transplacentally and is a possible cause of abortion/resorption or stillbirth.
• As well as vertical transmission (placenta and colostrum) horizontal transmission is considered possible, perhaps via oocyte shedding in feces, although this does not occur in significant numbers except in immunocompromised dogs.
• In cattle, prevalence of antibodies can be high, eg up to 35% in New Zealand, but abortion is probably triggered by an immunomodulating event, eg infection with bovine viral diarrhea virus.

Timecourse

• Clinical signs do not usually occur until puppies are 3-5 weeks old.
• Neurological signs may progress over days to months → dysphagia and death.
• Myocarditis may present as sudden collapse or death.

Epidemiology

• Transmission by ingestion and transplacentally.
• Chronically infected bitches may show recurrent parasitemia without clinical signs.
• Not all puppies in a litter may be affected.
• Full lifecycle is not known. The only stages identified are tachyzoites and tissue cysts.

Diagnosis

Treatment

Prevention

Outcomes