Serological screening for Schmallenberg virus in exotic and indigenous cattle in Nigeria.
Schmallenberg virus (SBV), a recently emerged Orthobunyavirus, is associated with abortions, stillbirths and congenital malformations in ruminants. Considering that Culicoides species which transmit this disease have previously been identified in Nigeria as vectors of bluetongue, another livestock disease that causes abortions, it is speculated that SBV also circulates in the Nigerian ruminant population. We therefore conducted a pilot study to investigate the occurrence of anti-SBV antibodies in a limited population of cross-breed, exotic and indigenous cattle in Nigeria. Serum samples obtained from 60 Friesian-White Fulani (FWF), 7 Jersey and 53 indigenous cattle were screened for SBV antibodies using a commercial indirect ELISA kit that detects antibodies against recombinant SBV nucleoprotein in ruminant sera. An overall seropositivity of 29.2% (35/120) was obtained with antibodies being detectable in 23.3% FWF (14/60), 42.9% Jerseys (3/7) and 34.0% (18/53) indigenous cattle. All indigenous breeds of cattle tested had seropositive animals: White Fulani (13/38, 34.2%), Sokoto Gudali (2/8, 25.0%), Red Bororo (1/5, 20.0%) and Bunaji (2/2, 100.0%). The detection of antibody-positive animals among unvaccinated cattle provides evidence of possible SBV infection in Nigeria. However, there is also the probability of cross-reactivity with other Simbu serogroup viruses, especially considering that some of these viruses have previously been reported in Nigeria. Further studies to confirm these preliminary findings using serum neutralisation assay, viral isolation or detection of SBV RNA from ruminants or Culicoides are necessary.