Contagious agalactia of sheep and goats. A review

Abstract

Contagious agalactia is a highly infectious disease of sheep and goats which has been included in the List B of dangerous infections issued by the International Office International des Epizooties. The major causal agent of the disease in both sheep and goats is Mycoplasma agalactiae and, in goats, the disease can also be caused by Mycoplasma mycoides subsp. mycoides large colony type (LC), Mycoplasma capricolum subsp. capricolum and Mycoplasma putrefaciens. The infection frequently occurs as an enzootic. In lactating female animals, it is usually manifested by mastitis. Males, young animals and non-lactating females suffer from arthritis, keratoconjunctivitis and respiratory problems. Young animals may often die. The diagnosis is based on the isolation and identification of the infectious agent by conventional methods, such as cultivation, growth inhibition test, epiimmunofluorescence test, etc., as well as on recently developed techniques such as dotimmunobinding test, gene probes and polymerase chain reaction. The routine serological method is the complement-fixation test and, recently, also immunoenzymatic methods. In regions affected by an enzootic, therapy with antibiotics or vaccination of infected animals are used. In economically and socially developed countries, there is a tendency to manage the disease in affected herds by gradual elimination of infected animals or even by killing them all at once. The main prerequisite for disease control is a quick and exact laboratory diagnosis of each mycoplasma species, with a particular emphasis placed on the identification of species included in the "mycoides cluster" group. This is expected to improve greatly with the use of monoclonal antibodies and gene amplification techniques. The development of a new generation of efficient vaccines, e.g., sub-unit vaccines or those based on a synthetic antigen, is considered to be a further essential step in contagious agalactia eradication.