References
Sheep-associated malignant catarrhal fever in cattle: an update
Abstract
Sheep-associated malignant catarrhal fever (SA-MCF) is a frequently fatal disease of many species including cattle, caused by ovine herpes virus-2. Sheep are the main reservoir host species and transmit the virus to other species, usually via aerosol. Clinical signs in affected animals can impact various body systems, and infection can be sub-clinical and become latent. No specific treatments exist, and empirical treatments are generally unrewarding. Occasionally some animals may survive, but there remains a chronic arteriopathy. Currently, the disease is controlled on farms is by reducing contact between susceptible hosts and sheep as much as possible, although a vaccine would be a useful protective strategy should one be developed.
Malignant catarrhal fever (MCF) is caused by Gammaherpesviruses of the Macavirus genus, namely ovine herpesvirus 2 (OvHV-2), caprine herpesvirus 2 (CpHV-2) and alcelaphine herpesvirus 1 (AlHV-1) (Russell et al, 2009). In the USA, Canada and Europe (including the UK) the sheep-associated (SA-MCF) form caused by OvHV-2 appears most commonly and has been documented in more than 30 species; however those of most interest to the UK are cattle, bison, water buffalo, deer and pigs (Flach et al, 2002; Russell et al, 2009; Li et al, 2014; Amin, 2015).
Sheep are considered the main reservoir host, and until recently were considered to be clinically unaffected. While this generally remains the case, there have been a small number of reports where sheep have died and been found to demonstrate pathologies similar to those found in other species affected by MCF in the absence of other causes of disease (Pesavento et al, 2019). An MCF-like syndrome can also be generated experimentally when sheep are exposed to large doses of OvHV-2 (O'Toole and Li, 2014).
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