Rift Valley Fever in Ruminants, Republic of Comoros, 2009

To the Editor: Rift Valley fever (RVF) is caused by a Phlebovirus (family Bunyaviridae) transmitted by a wide range of mosquitoes (1). This zoonotic disease is present in Africa, the Middle East, and Madagascar. Infections by RVF virus (RVFV) in ruminants cause massive abortions in livestock and high death rates in young animals, which result in major economic consequences. Humans are infected by mosquito bites, contact, or inhalation of aerosols. RVF is frequently unapparent or mild for humans, inducing an infl uenza-like illness that occasionally leads to more serious complications such as hemorrhage, meningoencephalitis, retinopathy, or even death (2). Cattle are socially important in Republic of Comoros because massive slaughtering occurs during traditional wedding ceremonies known as " Grands Mariages, " especially on the main island, Grande Comore. Because of low meat production (only 20,000 head of local cattle), a large number of live ruminants enter Grande Comore from Anjouan and Mohéli, the other 2 islands of the Republic, from Madagascar and Tanzania without quarantine or any other preliminary veterinary control. We report results from a serosurvey of the ruminant populations on the 3 islands of the Republic of Comoros during the 2009 dry season (April–August). A total of 488 blood samples were collected from randomly selected sheep, goats, and horned cattle and sent to laboratory facilities in Mayotte to be tested by an RVFV immunoglobulin (Ig) G competitive ELISA (3). Fifty IgG RVFV-negative and-positive serum samples were randomly selected for confi rmation by a seroneutralization assay using the reference method described in the World Organisation for Animal Health manual (4,5). Of the 488 serum samples tested, 160 were positive for RVFV, for a seroprevalence of 32.8% (95% confi dence interval [CI] 28.6%– 36.9%). The 3 species were positive for IgG, with prevalence of 30.6% 2 test, we found no statistically signifi cant differences regarding species and gender, but more adults than young animals were seropositive for RVFV IgG (p<0.001). Signifi cant differences in RVFV seroprevalence were found between islands (p<0.005), RVFV IgG ELISA-positive serum samples were confi rmed as positive for RVFV (Table). The serologic evidence of RVFV circulation in the ruminant population of the Republic of Comoros is in accordance with the epidemiologic situation described in other countries in the area. Actually, the serosurvey was implemented after the RVF outbreaks reported in several countries in eastern Africa in 2007 during El Niño rains (6). In August 2007, RVFV …