Borrelia infection in small mammals in West Africa and its relationship with tick occurrence inside burrows.
Tick-borne relapsing fever (TBRF) is a zoonotic disease caused by several Borrelia species transmitted to humans by Ornithodoros tick vectors. In West Africa, Borrelia crocidurae is a common cause of disease in many rural populations. Small mammals act as reservoirs of infection. We report here the results of surveys that investigated the occurrence of B. crocidurae infection in rodents and insectivores from eight countries of West and Central Africa. Animals were identified at the species level and tested for Borrelia either by examination of thick blood film, intra-peritoneal inoculation of blood or brain tissues into laboratory mice, or by molecular techniques. A total of 4358 small mammals belonging to 38 species and 7 families were collected, including 3225 specimens collected in areas where the occurrence of Ornithodoros sonrai tick in rodent burrows was documented, and 1133 in areas where this tick was absent. In areas with O. sonrai, Borrelia infection was demonstrated in 287 of 3109 (9.2%) small mammals tested, and none was documented in 1004 animals tested from other areas. There was no relationship between the occurrence of Rhipicephalus, Hyaloma and Argas ticks in burrows and the distribution of Borrelia infection in small mammals. The 287 specimens infected by Borrelia belonged to 15 rodent and shrew species, including three Saharo-Sahelian species - Gerbillus gerbillus, Gerbillus occiduus and Gerbillus tarabuli - identified as reservoirs for TBRF with a distribution restricted to this area. In Sudan and Sudano-Sahelian areas, Arvicanthis niloticus, Mastomys erythroleucus and Mastomys huberti were the main reservoir of infection. Although most small mammals species collected had a large distribution in West and Central Africa, the fact that only animals collected in areas with O. sonrai were found infected suggest that this tick is the only vector of TBRF in rodents and insectivores in this part of Africa.
Institut de Recherche pour le Développement (IRD), Campus International de Recherche IRD-Université Cheikh Anta Diop (UCAD) de Dakar, Hann Mariste, BP 1386, CP 18524 Dakar, Senegal. Electronic address: georges.diatta@ird.fr.
Georges
G
Diatta
Institut de Recherche pour le Développement (IRD), Centre de Biologie pour la Gestion des Populations, UMR 22, Campus de Baillarguet, CS 30016, 34988 Montferrier sur Lez cedex, France.
Jean-Marc
JM
Duplantier
Institut de Recherche pour le Développement (IRD), Centre de Biologie pour la Gestion des Populations, UMR 22, Campus de Baillarguet, CS 30016, 34988 Montferrier sur Lez cedex, France; Institut de Recherche pour le Développement (IRD), Centre de Biologie pour la Gestion des Populations, UMR 22, Campus ISRA-IRD de Bel Air, BP 1386, Dakar, Senegal.
Laurent
L
Granjon
Institut de Recherche pour le Développement (IRD), Centre de Biologie pour la Gestion des Populations, UMR 22, Campus ISRA-IRD de Bel Air, BP 1386, Dakar, Senegal.
Khalilou
K
Bâ
Institut de Recherche pour le Développement (IRD), Campus International de Recherche IRD-Université Cheikh Anta Diop (UCAD) de Dakar, Hann Mariste, BP 1386, CP 18524 Dakar, Senegal.
Gilles
G
Chauvancy
Département de Biologie Animale, Faculté des Sciences et Techniques, Université Cheikh Anta Diop (UCAD) de Dakar, BP 5005, Senegal.
Mady
M
Ndiaye
Institut de Recherche pour le Développement (IRD), Laboratoire de Paludologie et de Zoologie Médicale, UMR MIVEGEC, Campus International de Recherche IRD-Université Cheikh Anta Diop (UCAD) de Dakar, Hann Mariste, BP 1386, CP 18524 Dakar, Senegal.
Jean-François
JF
Trape
D000354:Africa, Western; D000818:Animals; D001899:Borrelia Infections / Q000635:transmission*; D004197:Disease Reservoirs; D017753:Ecosystem; D006801:Humans; D008297:Male; D026861:Ornithodoros; D011891:Rain; D048494:Rhipicephalus; D012377:Rodentia
Africa; Borrelia crocidurae; Borreliosis; Ornithodoros sonrai; Relapsing fever; Small mammals