African Horse Sickness Caused by Genome Reassortment and Reversion to Virulence of Live, Attenuated Vaccine Viruses, South Africa, 2004–2014
Published Date:Dec 15 2016
Source:Emerg Infect Dis. 22(12):2087-2096.
Keywords:African Horse Sickness
African Horse Sickness Caused By Genome Reassortment And Reversion To Virulence Of Live, Attenuated Vaccine Viruses, South Africa, 2004–2014
Asymptomatic Viral Infections
Environmental Vaccine Identification
Live Attenuated Vaccine
Vaccine Progenitor Availability
Pubmed Central ID:PMC5189153
Description:African horse sickness (AHS) is a hemorrhagic viral fever of horses. It is the only equine disease for which the World Organization for Animal Health has introduced specific guidelines for member countries seeking official recognition of disease-free status. Since 1997, South Africa has maintained an AHS controlled area; however, sporadic outbreaks of AHS have occurred in this area. We compared the whole genome sequences of 39 AHS viruses (AHSVs) from field AHS cases to determine the source of 3 such outbreaks. Our analysis confirmed that individual outbreaks were caused by virulent revertants of AHSV type 1 live, attenuated vaccine (LAV) and reassortants with genome segments derived from AHSV types 1, 3, and 4 from a LAV used in South Africa. These findings show that despite effective protection of vaccinated horses, polyvalent LAV may, paradoxically, place susceptible horses at risk for AHS.
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