Trypanosoma vivax detection test kit by using qPCR. Trypanosoma vivax is the causative agent of the disease nagana, also known as animal trypanosomiasis, affecting cattle and wild mammals. Symptoms of T. vivax include fever, anorexia, lethargy, anemia, progressive emaciation, a rapid decline in milk production, stillborn offspring, and a return to oestrus. T. vivax transmission occurs through a biological vector, the tsetse fly.