D357 - Neospora caninum

Description:

Neospora caninum is a recognized tissue-cyst-forming protozoan of the phylum Apicomplexa, which in the past was confused with Toxoplasma gondii due to its similar appearance under the microscope. The complete life cycle of this organism is unknown, but a carnivorous definitive host is suspected. Naturally occurring infections in dogs have been documented throughout the world. Seroprevalence of clinically healthy dogs is usually much less than 20% but much greater than the prevalence of clinical illness, suggesting the possibility of subclinical infections. Experimental transmission in dogs can occur after oral and parenteral administration, but transplacental transmission may be the predominant route in natural infections. In general, dogs infected with Neospora caninum display similar to symptoms to dogs with toxoplasmosis, but neurological deficits and muscular abnormalities predominate. Clinical signs may include those of hepatic, pulmonary, and myocardial involvement, but any tissue can become involved. The most severe and frequent infections have been in young dogs that presented with ascending paralysis of the limbs. Features that distinguish neosporosis from other forms of paralysis are gradual muscle atrophy and stiffness, usually as an ascending paralysis; the pelvic limbs are more severely affected than the thoracic limbs.

Diagnosis:

Lesions caused by Neospora caninum are similar to those found in dogs infected by T. gondii. Therefore, in the past conformation of infection conventionally depended on serologic or immunohistochemical methods. Demonstrating serum antibodies to Neospora caninum can help confirm the diagnosis of neosporosis. However, some false-positive titers exist in previously exposed dogs. Also, slight cross-reactivity with sera from dogs infected with Babesia gibsoni has been observed. In the last few years, diagnosis of neosporosis was much improved by the development of PCR tests, which allow a fast and methodically highly sensitive identification of the parasite through the amplification, and subsequent demonstration, of parasite-specific DNA sequences. A PCR-based assay is now available for the detection of N. caninum in a sample. This test can be performed on tissue biopsies or blood samples to definitively confirm the presence of Neospora caninum in a sample.

Treatment:

Drugs used for therapy of toxoplasmosis should be tried early in the course of illness. Laboratory experiments have shown activity of dihydrofolate reductase inhibitors (trimethoprim), ionophone antibiotics (monensin), macrolides (azithromycin, clarithromycin), tetracyclines (doxycycline), and lincosamides (clindamycin). Clindamycin, sulfadiazine, and pyrimethamine alone or in combination have been administered to treat canine neosporosis. However, clinical improvement is not likely in the presence of rapidly advancing paralysis or muscle contracture.

Sample:

1. Whole blood (3 ml) in a lavender (EDTA) top tube.
2. Tissue samples.

Special Handling:

Store samples at 4°C until pick up or shipment.

Test Code:

D357