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Volume 22, Number 12—December 2016

African Horse Sickness Caused by Genome Reassortment and Reversion to Virulence of Live, Attenuated Vaccine Viruses, South Africa, 2004–2014

Camilla Weyer, John D. Grewar, Phillippa Burger, Esthea Rossouw, Carina Lourens, Christopher Joone, Misha le Grange, Peter Coetzee, Estelle H. Venter, Darren P. Martin, N. James MacLachlan, and Alan J. GuthrieComments to Author 
Author affiliations: University of Pretoria, Onderstepoort, South Africa (C.T. Weyer, P. Burger, C. Lourens, C. Joone, M. le Grange, P. Coetzee, E. Venter, N.J. MacLachlan, A.J. Guthrie); Western Cape Department of Agriculture, Elsenburg, South Africa (J.D. Grewar); Wits Health Consortium, Johannesburg, South Africa (E. Rossouw); University of Cape Town, Cape Town, South Africa (D.P. Martin); University of California, Davis, CA, USA (N.J. MacLachlan)

Main Article

Table 2

Epidemiologic parameters for 4 outbreaks involving AHS virus type 1 in the AHS controlled area in Western Cape Province, South Africa, 2004–2014*

Parameter† 2004 Stellenbosch 2011 Mamre 2014 Porterville 2014 Robertson
No. confirmed cases 23 (16)‡ 84 (73)§ 89 22
No. deaths 18 (16)‡ 64 (64)§ 13 1
Case-fatality rate, %
78.3 (100)‡
76.2 (87.7)§
No. subclinical cases 0 15 (4)† 52 17
% Subclinical
17.9 (5.5)§
No. vaccinated cases 2/23 2/84 35/89 3/22
% Vaccinated
No. properties affected 10 (8)‡ 47 (45)§ 31 8

*AHS, African horse sickness.
†The parameters were calculated by using the current World Organization for Animal Health (OIE) case definition. Parameters calculated by using the case definitions when the outbreaks occurred are in parenthesis for the 2004 and 2011 outbreaks.
‡An additional 5 clinical cases and 2 deaths that met the criteria of the current OIE AHS case definition were not included based on the case definition in place at the time of this outbreak (13).
§An additional 11 subclinical cases that met the criteria of the current OIE AHS case definition were not included based on the case definition in place at the time of this outbreak (15).

Main Article

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