Reemergence of Rift Valley Fever, Mauritania, 2010

Ousmane Faye, Hampathé Ba, Yamar Ba, Caio C.M. Freire, Oumar Faye, Oumar Ndiaye, Isselmou O. Elgady, Paolo M.A. Zanotto, Mawlouth Diallo, and Amadou A. Sall

Author affiliations: Institut Pasteur, Dakar, Senegal (O. Faye, Y. Ba, O. Faye, M. Diallo, A.A. Sall); Institut National de Recherche en Santé Publique, Nouakchott, Mauritania (H. Ba, I. O. Elgady);University of São Paulo, São Paulo, Brazil (C.C.M. Freire, P.M.A. Zanotto)

Abstract

A Rift Valley fever (RVF) outbreak in humans and animals occurred in Mauritania in 2010. Thirty cases of RVF in humans and 3 deaths were identified. RVFV isolates were recovered from humans, camels, sheep, goats, and Culex antennatus mosquitoes. Phylogenetic analysis of isolates indicated a virus origin from western Africa.

Rift Valley fever (RVF) is an acute febrile viral disease that affects domestic ruminants and humans. The disease in animals is characterized by abortions among pregnant females and high mortality rates for offspring (1). The causative pathogen, RVF virus (RVFV), is a member of the family Bunyaviridae, genus Phlebovirus, and its genome consists of 3 RNA segments: large (L), medium (M), and small (S) (2). In human infections, symptoms are generally mild but may evolve to severe symptoms, such as hemorrhaging, meningoencephalitis, and retinopathy, with fatal outcomes (3). RVF is endemic to sub-Saharan Africa, Egypt, Saudi Arabia, and Yemen (4). In western Africa, a major RVF outbreak occurred in Mauritania and Senegal in 1987 and resulted in 220 human deaths (5). This outbreak was followed by epizootics/epidemics in 1998 and 2003 in different provinces in Mauritania (Hodh El Gharbi, Assaba, Brakna, Trarza, and Gorgol Provinces) (6,7).

Figure 1

Thumbnail of Location of study sites tested for patients with confirmed Rift Valley fever, Mauritania, 2010.

Figure 1. . Location of study sites tested for patients with confirmed Rift Valley fever, Mauritania, 2010.

In October 2010, the health services of Adrar Province in Mauritania were informed of the deaths of 2 girls with hemorrhagic syndromes and 2 persons with acute fever, arthralgia, and headaches in Amogjar Province. Blood samples collected from a sick patient were sent to Institut Pasteur in Dakar, Senegal where RVFV IgM and RVFV genome were detected. During October 28–November 11, 2010, suspected RVF cases were identified in several cities Adar Province (Atar, Aoujeft, Chinguetti), Inchiri Province (Akjoujt), and Hodh el Gharbi Province (Tintane, Kobeni) (Figure 1), and high mortality rates among camels, sheep, and goats were reported in Adrar and Inchiri Provinces (8). Clinical samples from humans and animals with suspected RVF were positive for this virus.

These cases led to identification of 2 additional confirmed cases of acute RVF (positive for IgM against RVFV or RVFV RNA) in Adrar and Inchiei Provinces. Multidisciplinary investigations involving epidemiologists, virologists, entomologists, and veterinary teams in areas where the cases occurred were conducted in December 2010 as part of other investigations (8), describe the extent of the outbreak, and investigate possible RVF reemergence factors in Mauritania. We report results of laboratory and field investigations among humans, animals, and mosquitoes during the 2010 outbreak.