West Nile virus serosurveillance in camelids

West Nile virus (WNV) encephalitis in camelids may result in clinical signs of disease ranging from anorexia, fever and facial tremors to incoordination, recumbency and death. Similar to humans and horses in which <1% of WNV infected individuals become severely ill, it appears that the majority of camelids infected by WNV are asymptomatic and recover uneventfully. Since camelids are reported to be at “low risk” for WNV infection, the objective was to determine the prevalence of subclinical WNV infection through a nationwide serosurveillance study. Jugular venous blood samples were collected from 322 camelids on 35 farms in 20 states. Owners provided information about each animal including species, gender, age, coat type (Huacaya or Suri), and coat color. End-point virus-neutralizing antibody titers were used to determine seropositive rate. Sixty-nine percent (18/26) of camelid farms from areas of known WNV activity had one or more seropositive animals. There was no effect of gender, age coat type or coat color on the seropositive rate. Alpacas produced a significantly higher titer compared to llamas following subclinical infection. However, significantly more llamas were seropositive compared to alpacas. Camelid owners should be vigilant in carrying out WNV preventative measures (e.g. vaccination, mosquito control). In addition, camelid owners should be aware of the sign of WNV related illness, since early treatment yields the best results.