Equine Health Update Issue 1 Volume 16 - Page 7

appetite, weight loss, abortion, and incoordination, followed by paralysis of the hind limbs. Researchers divide these clinical signs in two or three stages of the disease: subacute, acute, and chronic. In the chronic stage, horses usually exhibit cachexia (chronic wasting) associated with neurological signs and limb paralysis. Neurological signs are the result of the parasite travelling to the brain, where it causes an inflammatory response leading to encephalitis and cellular necrosis. Trypanosomiasis caused by T. evansi can be clinically confused with other diseases, including equine protozoal myeloencephalitis in the chronic stages. Where surra is suspected, it is important to rule out other causes of equine neurologic disease. Most available diagnostic methods include the parasitological, serological, and polymerase chain reaction (PCR). The parasitological test is fast, but it lacks specificity and sensitivity due to low numbers of the parasite in the bloodstream. Serology, employing a card agglutination test kit known as CATT/T. evansi, has been a method used for disease surveillance in several countries. PCR testing on blood samples is a specific and sensitive method; however, it is not 100 percent reliable since T. evansi may only be present in the tissues. Like any infectious agent, T. evansi stimulates an immune response in the infected animal. While this response is unable to clear the infection from the host, it controls and maintains the parasitemia at low levels, resulting in the disease becoming chronic. In many countries, the disease is treated with diminazene aceturate. However this drug, even when used at the recommended dose, has no significant curative