African horse sickness in Spain.

Area of Science:

• Veterinary Virology
• Epidemiology
• Equine Infectious Diseases

Background:

• African horse sickness (AHS) is a severe, insect-borne viral disease affecting equids, caused by an Orbivirus with nine known serotypes.
• Recent outbreaks in the Iberian Peninsula (1987-1990) highlight the re-emergence of AHS outside its endemic African range.

Purpose of the Study:

• To review the aetiology, pathogenesis, and epizootiology of African horse sickness.
• To analyze recent outbreaks in the Iberian Peninsula, focusing on the causative serotype and clinical presentations.
• To discuss factors contributing to the recurrence and spread of AHS in Spain.

Main Methods:

• Review of existing literature on African horse sickness.
• Analysis of epidemiological data from outbreaks in the Iberian Peninsula between 1987 and 1990.
• Examination of clinical presentations and serotype identification during outbreaks.

Main Results:

• Outbreaks in Spain (1987-1990) were primarily associated with AHS serotype 4, unlike previous extra-African outbreaks caused by serotype 9.
• Clinical manifestations varied, predominantly acute (pulmonary) form, with a notable prevalence of the subacute (cardiac) form in 1988.
• Control measures including animal culling, movement restrictions, and expanding vaccination campaigns were implemented, successfully containing further spread.

Conclusions:

• The 1987 outbreak was likely linked to imported infected zebras.
• Recurrence may be attributed to favorable climatic conditions for vectors, potential subclinical virus circulation in mules/donkeys, and incomplete herd immunity from vaccination gaps.
• Effective containment strategies combining veterinary interventions and public health measures are crucial for managing AHS outbreaks.