GENERAL INTRODUCTION: BABESIOSES

BABESIOSES

A General Introduction has been added to each disease chapter in an attempt to give a brief updated overview of the taxonomic, biological and other characteristics of the virus family or group of bacteria /protozoa that cause disease in livestock and, where relevant, involve wildlife. As the text of the three-volume book Infectious Diseases of Livestock is currently under revision the Editors are aware that there are inconsistencies between the updated introductions to chapters and the content of the chapters themselves. Once the chapters have been updated – a process that is currently underway – these inconsistencies will be removed.

Babesiosis is caused by infection with species of tick-borne, intra-erythrocytic and generally host-specific protozoan parasites of the genus Babesia which belong to the phylum Apicomplexa, class Sporozoasida, order Eucoccidiorida, suborder Piroplasmorina and family Babesiidae. It occurs in a wide variety of vertebrate hosts, including humans, and has a very wide distribution around the world. In southern Africa the resulting disease is often given one or more colloquial names in the regions where it occurs, such as redwater or rooiwater (Afrik.) in cattle, and biliary fever or galkoors (Afrik.) in horses and dogs. The general disease manifestations are similar in all vertebrate host species and, as the popular names imply, tend to be characterized in varying degrees by intravascular haemolysis, haemoglobinaemia and the development of haemoglobinuria (which is responsible for the urine being coloured red), and icterus. Babesia equi is thought also to have a stage of development in lymphocytes of the equine host. The genus Babesia is named after Dr Victor Babes who, in 1887, established the aetiology of a cattle disease in Romania associated with haemoglobinaemia. The disease in cattle is particularly prevalent in tropical and subtropical countries where the vector ticks are widespread.

In southern Africa, bovine babesiosis and other tick-borne diseases such as heartwater, gallsickness (anaplasmosis) and some of the theilerioses (e.g. East Coast fever, Corridor disease, and Zimbabwe theileriosis) are of considerable economic importance. The true importance of equine babesiosis in the subcontinent in Africa has not been adequately assessed, but it remains an important disease. In addition, it is a hindrance to the free movement of horses, as many countries prohibit their importation from southern Africa. Outbreaks of porcine babesiosis are rare and are not of economic importance. Babesia motasi and Babesia ovis infections in sheep and goats have not been recorded in southern Africa. Biliary fever in dogs caused by Babesia canis remains a very important, if not the most important, infectious disease of dogs and is widespread in southern Africa. On the other hand, the prevalence of Babesia felis infection in cats is low and encountered mainly in the coastal parts of KwaZulu-Natal and the Eastern and Western Cape provinces of South Africa. Babesiosis is a zoonosis, but cases of disease in humans caused by Babesia spp. are rare and usually occur in immuno-compromised (e.g. splenectomized) patients. However, on Nantucket Island and the island off the coast of Massachusetts and New York in the USA, babesiosis caused by the rodent parasite Babesia microti has been reported in immunocompetent humans.