Wesselsbron Virus

Wesselsbron Virus Background

Wesselsbron disease (WSL) is an acute arthropod-borne flavivirus infection of sheep, cattle, and goats, causing relatively high mortalities in new-born animals and occasional abortion in adults. In humans it causes a non-fatal influenza-like illness.

The first known outbreak was reported in 1955 on a sheep farm in the town of Wesselsbrons in Orange Free State Province, South Africa and WSLV was isolated from the blood of a febrile man and a dead lamb (Weiss et al., 1956; Weyer et al., 2013). Immunohistochemical staining of sections of formalin-fixed liver has been used to confirm the diagnosis of WSL in new-born lambs using polyclonal antibodies against WSL virus (van der Lugt et al., 1995). WSLV has since been isolated from Cape short-eared gerbil in southern Africa and there is serological evidence for circulation in humans since the 1970s, more recently in eastern Senegal with 2 human cases and isolation of the same strain from a black rat (Diagne et al., 2017).

Flavivirus serological relationships are important in determining diagnosis and epidemiology of infections in Africa. No significant antigenic variation has been observed between WSLV, Potiskum (POT) and Yellow fever virus (YFV) viruses in cross-haemagglutination-inhibition (Cross-HI) and cross-complement fixation (Cross-CF) studies. However, differences in antigenicity were observed between these viruses and Uganda S, Banzi and Zika viruses (Baba et al.,1998).  A flavivirus haemagglutination-inhibition (HI) test adopted to the solid-phase immunosorbent technique (SPIT) was used to confirm the high prevalence of IgM in people of younger age groups in Nigeria. Although not as sensitive as the conventional HI test, it was found to be more specific and potentially feasible for the detection of early WSLV infections in flavivirus hyperendemic environments (Baba et al., 1999).

WSLV is one of a number of lesser known mosquito transmitted flaviviruses but highlights the potential of such viruses to emerge (Smith, 2017). Further investigations are needed to understand the life cycle and the impact on public health. Rodents may act as a reservoir and are abundant worldwide; Aedini populations are expanding their range, all of which may suggest WSLV could have a larger distribution than expected.

References

• Baba et al. (1998). Antigenic relatedness of selected flaviviruses: study with homologous and heterologous immune mouse ascitic fluids. Rev Inst Med Trop Sao Paulo. 40(6):343-9.
• Baba et al. (1999). Preliminary studies on the use of solid-phase immunosorbent techniques for the rapid detection of Wesselsbron virus (WSLV) IgM by haemagglutination-inhibition. Comp Immunol Microbiol Infect Dis. 22(1):71-9.
• Barnard (1997). Antibodies against some viruses of domestic animals in southern African wild animals. Onderstepoort J Vet Res. 64(2):95-110.
• Diagne et al. (2017). Emergence of Wesselsbron virus among black rat and humans in Eastern Senegal in 2013. One Health. 3:23-28.
• Smith (2017) Waiting in the wings: The potential of mosquito transmitted flaviviruses to emerge, Critical Reviews in Microbiology, 43:4, 405-422.
• van der Lugt et al. (1995). The diagnosis of Wesselsbron disease in a new-born lamb by immunohistochemical staining of viral antigen. Onderstepoort J Vet Res. 62(2):143-6.
• Weiss et al. (1956). Wesselsbron virus—a virus not previously described, associated with abortion in domestic animals. Onderstepoort Vet. J. 27:183–195.
• Weyer et al. (2013). Human Cases of Wesselsbron Disease, South Africa 2010–2011. Vector-Borne and Zoonotic Diseases. 13 (5): 330–337.