African horse sickness in Zimbabwe: 1972 to 1981.

This research paper focuses on the spread and impact of African Horse Sickness (AHS) in Zimbabwe from 1972 to 1981, revealing multiple serotypes of AHS virus along with high death rate in horses including the vaccinated ones, warranting further studies regarding vaccine-induced and maternal immunity.

Research Objective and Methodology

• The primary objective of this study was to understand the prevalence and consequences of AHS among equine populations in Zimbabwe over a nine-year period, spanning from October 1972 to September 1981.
• The investigators isolated the AHS virus from suspected disease cases and used a complement fixation test to identify the AHS antibody titres, indicative of recent infection.
• Additionally, a survey was conducted in 1980 where horse owners in Zimbabwe were asked about their experiences and observations of AHS, specifically regarding clinically diagnosed cases and resultant mortalities.

Findings

• The researchers found that the AHS virus was detected in 23 suspected cases of the disease during the study period. Moreover, recent infection was detected through antibody titres in an additional 49 horses.
• The isolated viruses belonged to seven of the nine known serotypes of AHS, indicating a diverse representation of virus strains.
• In the 1980 survey, it was found that out of approximately 8,000 horses, owners of 1,654 (or 20%) reported 207 clinically diagnosed AHS cases and 107 deaths between 1975 and 1980. Of these, 56 cases with 50 deaths occurred in foals while many other cases occurred in vaccinated horses.

Conclusion

• The study concluded that AHS was a significant disease among horses in Zimbabwe during the study period, with the virus being detected in multiple cases and resulting in a significant number of deaths.
• The fact that many cases were reported among vaccinated horses raised questions about the efficacy of the vaccine, suggesting the need for further investigation into vaccine-induced immunity.
• The high occurrence of infections and deaths in foals also indicated the need for studies on maternal immunity and how it could possibly be improved for a better protective effect.