Seroprevalence of Rift Valley fever virus infection in camels (dromedaries) in northern Tanzania

Rift Valley fever (RVF) is an arthropod-borne viral zoonotic disease that affects a wide range of animals including sheep, goats, cattle, camels and humans. Camels have only recently been introduced into Tanzania and, as a result, there is no credible diseases status information concerning this population, estimated to be in the low hundreds. As part of a broader study on camel diseases in different localities of northern Tanzania, serum samples (n=109) were collected from apparently healthy, non-vaccinated camels during the period June to August 2010 and tested for antibodies specific to RVF virus (RVFV) using the inhibition enzyme-linked immunosorbent assay (ELISA). Overall, herd and individual camel IgG seroprevalence was 78.5%(11/14) and 27.5%(30/109), respectively. IgG was found to be most prevalent in camels from Kilindi and Hai districts (45 %, each) and in introduced camels from other areas (37.1 %). The relationship between age and seropositivity showed that the seroprevalence was the highest (84.6 %) in age group of >= 10 years and lowest (11.9 %) in age group of <= 5 years. The results of this study reveal that evidence of camels being exposed to RVFV and that the risk of seropositivity varied according to district, being higher in Kilindi and Hai compared with other districts sampled. The risk of seropositivity increased with increasing animal age and the introduction of camels into the herd. Based on these study findings, continuous disease surveillance of camels for RVFV is indicated.