References
An update on Rhodococcus equi pneumonia in foals
Abstract
Rhodococcus equi is one of the most common causes of pneumonia in foals. Despite the widespread presence of R.equi in the environment, there is marked variation in disease prevalence. Several studies have investigated the factors that may play a role in this variation, although further research is required. The insidious nature of R.equi can make early diagnosis challenging, therefore screening of foals is common practice on endemic farms. A consequence of this has been the mass overtreatment of foals with subclinical infection, which has contributed to the development of antimicrobial resistance. Further strategies are required to better identify foals that require treatment, in order to reduce antimicrobial use without resulting in increased mortality. Effective preventative measures are also an area of great importance. Currently, the administration of hyperimmune plasma is the mainstay of prevention, but vaccination represents the ideal prevention strategy and is a major goal for the future.
Rhodococcus equi is a soil saprophytic, Gram-positive, intracellular bacteria and one of the most common causes of pneumonia in foals worldwide. The bacteria are ubiquitous and can be cultured from the environment of virtually all horse farms. However, the prevalence of clinical disease varies from endemic on some farms to sporadic or unseen on others.
Bronchopneumonia is the most common clinical manifestation of R.equi in foals aged between 1 and 6 months. Disease in adult horses has been described, although this is limited to cases with severe underlying immunodeficiency. Similarly, R.equi infection has also been reported in immunodeficient humans, for example those with HIV or those undergoing chemotherapy for cancer. In addition to pneumonia, R.equi can also result in infections in other body systems, for example bone infection, ocular disease, diarrhoea and abdominal abscesses. On farms where the disease is endemic, costs associated with treatment and foal losses can be substantial. This article provides an update on the epidemiology, diagnosis and treatment of R.equi, in addition to current strategies for the prevention of disease.
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