ABSTRACT
The immunohistochemical test (IH) was compared with the bioassay in mice to diagnose experimental infection of goats with Toxoplasma gondii. The first technique is specific and fast, while the bioassay, a technique widely used to confirm the diagnostic, is sensible but takes many weeks to be done. This study was conducted with the aim to observe the possibility of IH to substitute bioassay in mice. Nine goats received 105 oocists of T. gondii (AS 28) per os and two were kept as non-infected controls, receiving a placebo. Diarrhoea, inapetence and fever were present in all infected goats from 3 to 8 days post-infection and in one of them until the 13th. Control animals showed no symptoms. Eight weeks later all these animals were slaughtered and fragments of brain, spinal cord, retina, liver, spleen, cervical and mesenteric lymph nodes, kidneys, lungs, heart and skeletal muscles, diaphragm, pancreas, adrenal gland, salivary glands and small intestine were collected and submitted to bioassay and IH. Macroscopic lesions were not observed to the necropsy. Eight slides of each fragment were submitted to IH, but no taquizoites, cysts or fragments of the parasite were detected. All the infected goats were positive to the bioassay, and brain and spinal cord were the tissue with many positive cases. None of the controls were positive to these tests. In conclusion: the bioassay is still the best technique to diagnose chronic toxoplasmosis in goats without clinical symptoms.
KEY WORDS:
Toxoplasma gondii; goats; diagnosis; immunohistochemical test; bioassay.