The Veterinary Significance of Mycoplasmas

Abstract

The reappearance of contagious bovine pleuropneumonia (CBPP) in Italy in 1990 after an absence of 100 years and the continued spread of CBPP in many parts of Africa are powerful reminders that this age-old disease is still a long way from eradication. Control of this disease was almost achieved during the 1970s when it was eradicated from Australia, restricted to a small area in eastern Africa, and was giving rise to only sporadic outbreaks in Europe (1). However, as a result of civil wars and the subsequent breakdown of veterinary services, CBPP began to spread and is today the most important cattle disease in Africa, causing greater losses than rinderpest according to the Office d’International Epizooties (OIE). As a result, CBPP is designated as a list A disease. Mycoplasma mycoides subsp. mycoides small colony (SC) variant, which is the cause of CBPP, was the first mycoplasma to be isolated nearly a century ago. It differs from most other mycoplasmas in that it can be a primary cause of disease just about fulfilling Koch’s postulates. The mechanism of its pathogenicity remains uncertain, but recent work confirms early findings that hydrogen peroxide production is an important factor (2). Evidence has also been provided to explain why European strains were far less virulent than African strains. It showed that African, but not European, strains hydrolyzed glycerol and produced hydrogen peroxide. M. m. mycoides SC is a member of the “mycoides cluster,” which contains six important mycoplasmas of large and small ruminants (Table 1).

Table 1 Members of the Mycoides cluster