The QRS response of the electrocardiogram to bleeding has been a source of interest to the physiologist for more than a century. Studies in the dog, cat and chicken have shown a reduction in QRS amplitude in response to bleeding. This effect has been explained by the so-called Brody effect, in which the intraventricular mass of blood acts as a conducting medium, augmenting radial conduction, thus resulting in the subsequent reduction in QRS amplitude in conditions where the intraventricular mass of blood is reduced. The aim of this study was to evaluate whether the Brody effect will be present in the ovine heart and, furthermore, to evaluate if the right and left ventricles will demonstrate the same QRS change if the Brody effect is indeed present. This study clearly demonstrated that the Brody effect is present in the ovine heart. Furthermore, two unique aspects emanating from this study are firstly the fact that this is the first study to show that premature ventricular complexes are able to induce the Brody effect and, secondly that there is a very clear difference in the response of the right and the left ventricles when the Brody effect is induced in the ovine heart.

The QRS response of the electrocardiogram to bleeding has been a source of interest to the physiologist for more than a century. Studies in the dog, cat and chicken have shown a reduction in QRS amplitude in response to bleeding. This effect has been explained by the so-called Brody effect, in which the intraventricular mass of blood acts as a conducting medium, augmenting radial conduction, thus resulting in the subsequent reduction in QRS amplitude in conditions where the intraventricular mass of blood is reduced. The aim of this study was to evaluate whether the Brody effect will be present in the ovine heart and, furthermore, to evaluate if the right and left ventricles will demonstrate the same QRS change if the Brody effect is indeed present. This study clearly demonstrated that the Brody effect is present in the ovine heart. Furthermore, two unique aspects emanating from this study are firstly the fact that this is the first study to show that premature ventricular complexes are able to induce the Brody effect and, secondly that there is a very clear difference in the response of the right and the left ventricles when the Brody effect is induced in the ovine heart.

Babesiosis is a tick-borne disease affecting humans and many domestic and wild animals. Domestic animals showing appreciable morbidity and mortality include dogs, cats, cattle and horses. Both canine and feline babesiosis are diseases characterised by haemolytic anaemia, icterus and haemoglobinuria. Canine babesiosis can range from chronic or subclinical to peracute and fatal, depending on the virulence of the species and the susceptibility of the host. This paper deals with canine babesiosis with specific reference to pathogenesis, clinical findings, complications, diagnosis and treatment, as well as newly identified prognostic factors in Babesia rossi babesiosis.

Eighty ixodid tick species, 25 argasid tick species and Nuttalliella namaqua occur in South Africa. Twenty-one of the 80 ixodid species and two of the argasid species occur only in this country, while N. namaqua is present only in South Africa and Namibia. Forty-six of the 80 ixodid species and 16 of the 25 argasid species as well as N. namaqua have been described as new species since 1908. People working in South Africa have written or contributed to the descriptions of 24 of these 63 new species, while foreign researchers have described the remainder. New species indigenous to South Africa are still being discovered, while the names of some species, well known because of their veterinary importance, have been altered.

Heartwater is an economically serious tick-borne disease of ruminants caused by the intracellular bacterium Ehrlichia ruminantium. The disease has traditionally been controlled by four different approaches: controlling the tick vector by dipping, establishing endemic stability, performing immunisation by infection and treatment, and preventing the disease by regular administration of prophylactic antibiotics. The first three of these methods are subject to failure for various epidemiological reasons, and serious disease outbreaks can occur. Prophylaxis is effective, but very expensive, and the logistics are daunting when large herds of animals are involved. The development of a safe, cheap and effective vaccine is the only likely way in which heartwater can be economically controlled, and over the past 15 years three new types of experimental vaccine have been developed: inactivated, attenuated, and recombinant vaccines. These new vaccines have shown varying degrees of promise, but none is as yet sufficiently successful to be marketable. We describe the experimental products, and the various technical and biological difficulties which are being encountered, and report on ways in which new technologies are being used to improve vaccine effectiveness.