Abstract:
A convenience sample of sheep and cattle herds around the cities of Harare, Kwekwe and
Bulawayo, located in the Highveld region of Zimbabwe, was used to estimate the seroprevalence
and sero-incidence of bluetongue virus (BTV) and epizootic haemorrhagic disease
virus (EHDV) antibodies. A competitive enzyme-linked immunosorbent assay was used to
identify serum antibodies against BTV and EHDV across three rainy seasons. The median
sero-prevalence of BTV and EHDV antibodies in cattle was 62% (interquartile range [IQR]:
30–89) and 56% (IQR: 5–77), respectively. In sheep, the median sero-prevalence of BTV and
EHDV was 41% (IQR: 19–63) and 0% (IQR: 0–21), respectively. Median sero-incidences of BTV
and EHDV antibodies in cattle of 43% (IQR: 22–67) and 27% (IQR: 9–57) respectively were
recorded. The median sero-incidence of BTV in sheep was 14% (IQR: 6–23). Based on these
preliminary findings, animal health workers in Zimbabwe should continue to monitor the
exposure rates of cattle and sheep to BTV and consider the possibility of strains emerging with
increased pathogenicity. There are no previous published reports of antibodies against EHDV
in Zimbabwe so the possibility of epizootic haemorrhagic disease existing in domestic livestock
should now be considered by Zimbabwean animal health officials. Seroconversions to BTV
and EHDV occurred predominantly at the end of each rainy season (March and April), which
generally corresponds to high numbers of the Culicoides vectors. BTV isolations were made
from three individual cows in two of the sentinel herds and all three were identified as
serotype 3. This is the first time BTV serotype 3 has been recorded in Zimbabwe, although its
presence in neighbouring South Africa is well documented.
