Clinical Effect of Dimethylsulphoxide in Sheep Suffering froin Heartwater

Abstract

Clinical heartwater, an often-fatal tick-borne disease, is caused by the rickettsia Cowdria ruminantium transmitted by the Amblyomma tick species. This disease is characterized by pyrexia (rectal temperature exceeding 40°C/104°F), listlessness and depression, inappetence and forestomach atony, hyperesthesia, hypermetria, lateral recumbency and agonal paddling of the limbs. Petechiation of the mucous membranes is common and chemosis (edema) of the conjunctiva may be evident. There are numerous strains of the causative organism that result in various presentations of clinical disease. The disease is the third most important cause of financial loss to livestock farmers in sub-Saharan Africa.

Heartwater is known to occur on Guadeloupe, and it has been suggested that the disease may spread to the American mainland either via subclinically infected imported livestock or on migrating cattle egrets that carry the vector. Climatic conditions suitable for establishment of the vector exist, and large populations of susceptible white-tailed deer offer the possibility of widescale spread of the disease.

Oxytetracyclines are the therapeutic drug group of choice in treatment of the disease. While anecdotal evidence of the beneficial effects of other symptomatic treatments exist none of these have been subjected to scientific scrutiny. Dimethylsulphoxide (DMSO), an aprotic hygroscopic solvent that, by its oxygen radical scavenging effect, displays anti-inflammatory properties, has been used as a symptomatic treatment with anecdotal beneficial effect. In a trial comparing anti-inflammatory agents in the treatment of mice suffering from heartwater, the group treated with DMSO had a higher survival rate. Based on this data, a trial was designed to gauge the clinical effect of DMSO in sheep suffering from heartwater.