Sources and epidemiology of Streptococcus uberis, with special emphasis on mastitis in dairy cattle.
Zadoks, R. N.
[History] Received: 1 February 2007; Accepted: 25 April 2007
CAB Reviews: Perspectives in Agriculture, Veterinary Science, Nutrition and Natural Resources, 2007, 2, 030, 15 pp.
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Streptococcus uberis is an important cause of mastitis in dairy cattle around the world. The organism has also been associated with mastitis in goats, sheep, camels and buffaloes, and with a variety of other conditions in ruminants and non-ruminant species. S. uberis has been reported in humans but the accuracy of its identification is debated. Many extra-mammary sources harbour S. uberis, including body sites, the gastro-intestinal tract, soil, water, forage and insects. Faecal shedding by cows may be needed to maintain S. uberis in the environment. Because of its occurrence in the environment and because of its epidemiology, S. uberis is considered an environmental organism. In addition, S. uberis can spread as contagious pathogen. Evidence for environmental and contagious modes of transmission derived from management data and molecular typing studies is reviewed. Potential mechanisms of host-adaptation are discussed, and results from field studies on treatment are interpreted in the context of a proposed conceptual framework, which encompasses environmental and contagious manifestations of S. uberis mastitis. Vaccine development strategies and current control measures are summarized. The relative importance of transmission mechanisms and control measures differs between herds and geographic areas. Standard mastitis prevention measures may reduce the prevalence of contagious S. uberis mastitis, resulting in a shift to predominantly environmental S. uberis mastitis. Overemphasis on environmental mastitis may result in a re-emergence of contagious mastitis.