It's a Small World: Infectious Threats to the UK Horse Industry

Specific risks for introduction of disease
Increases in the international movement of equids, trade in biological products and the removal of many pre-export veterinary checks for travel within Europe could all contribute to dissemination of specific pathogens in the UK. Climate related changes in vector distribution and survival also could enhance the maintenance of reservoirs of infection for specific vector-borne viruses should they arrive. Significant infections occurring in the UK over the last year have included equine infectious anaemia (EIA), equine viral arteritis (EVA) and contagious equine metritis (CEM). Of the 14 notifiable and endemic diseases considered by the London 2012 Equestrian Games Risk Register (Slater 2012), 2 were assessed as needing particular monitoring with regard to biosecurity measures and are discussed here: African horse sickness and EIA.

Aetiopathogenesis of African horse sickness
African horse sickness (AHS) is caused by an Orbivirus, of which there are 9 main serotypes, with some cross-neutralisation. Following infection and spread to the regional lymph nodes, horses undergo a viraemia lasting 4–8 days prior to progressive microvascular endothelial cell injury. The development of pulmonary oedema, pleural and pericardial effusions and myocardial damage may be extremely rapid, and fatal in up to 95% naïve individuals (peracute ‘dunkop’ pulmonary form). Indigenous zebras and donkeys in sub-Saharan Africa are more adapted to the virus and develop repeated subclinical infections with prolonged viraemia, acting as reservoirs of the virus. [...]