Diagnosis of Neosporosis in individual animals
Aborted fetuses and fetal material
- Histology in tissues from aborted fetuses– Widely disseminated changes are present in many organs.
The most diagnostically significant lesions are found in the brain and consist of scattered foci of nonsuppurative cellular infiltrates with occasional foci of necrosis.
Other histological lesions include:- nonsuppurative epicarditis and/or myocarditis
- focal nonsuppurative myositis
- nonsuppurative portal hepatitis, frequently with focal hepatic necrosis
- focal nonsuppurative interstitial pneumonia.
- Immunohistochemistry– to identify tachyzoites and tissue cyst stages of the parasite in fetal tissue.
Immunohistochemistry is most successful on sections of fetal brain, although the parasites are also frequently present in the lung, kidney and skeletal muscle. - Polymerase chain reaction (PCR) – detection of Neospora caninum specific DNA.
- Serology in fetal fluids
Two different tests are used IFAT(Indirect fluorescence antibody test) and ELISA( Enzyme linked immunosorbent assays).
A positive result is strongly indicative of N. caninum infection however a negative result is not always reliable because:
- Fetuses less than 6 months old do not elicit an adequate immune response to produce antibodies.
- The interval between infection and death may be too short for an adequate immune response.
- Autolysis may cause degradation of foetal immunoglobulins (antibodies).
Individual aborting dam
Cows and heifers that abort due to N. caninum do not exhibit clinical signs. See clinical signs.
Often the aborted material is not available or is very autolysed. In these cases serology from the dam can be used to help in the diagnosis. The limitations of individual serology from aborting cows and heifers are:
- A positive serological result will confirm that the animal had been exposed to the parasite however can not be used to confirm N. caninum as the cause of abortion.
- Paired serology (two samples four weeks apart) will not necessarily show an increase in antibody titres. Decreased antibody levels have been noted in cattle shortly after an abortion due to Neosporosis.
Congenitally infected calves
These are calves that have been infected in utero with the parasite but are usually born healthy. In order to identify them blood samples collected prior to colostrum intake can be tested for the presence of antibodies against N. caninum using serology (IFAT, ELISA).
