The sessions sampling performed during our investigation study revealed the presence of six small mammals species circulating both in Faladjè and/or Bougouni areas including
M. erythroleucus,
M. natalensis,
R. rattus,
P. daltoni,
G. gambianus,
T. gracilis,
Crocidura cf
olivieri, Atelerix cf
albiventris and
Crocidua spp. among them three species frequented the both areas (
M. erythroleucus, M. natalensis,
P. daltoni) and five other species (
R. rattus,
G. gambianus,
T. gracilis,
C. cf
olivieri,
A. cf
abiventris) associated with the genus
Crocidura spp. were captured either in Faladjé or in Bougouni. Variation in relative abundance between Faladjè and Bougouni stands of small mammals was significant, therefore the
M. erythroleucus species was the most dominant (57.33%, 43/75) in the Faladjè stand and
R. rattus dominated (37.5%,18/48) that of Bougouni. Most of these small mammal species sampled in our study represent a source of contamination of infectious diseases such as salmonellosis, leptospirosis, tick-borne relapsing fever borreliosis, murine typghus, Lassa fever, Rift Valley fever, Crimean-Congo hemorrhagic fever, viral meningitis, toxoplasmosis and coxiellosis, through ingestion of contaminated food, water or through the bite of infected arthropod vectors (ticks, fleas, mosquitoes) [2,3,5,6,9,11-15]. Of these infectious diseases cited above, it is particularly important to note that all of the small mammal species captured were found to be naturally infected with
Borrelia crocidurae, the pathogen of tick-borne relapsing fever borreliosis endemic in West African countries (Senegal, Mali, Mauritania and The Gambia) and like so known in that of north Africa (Morocco, Algeria and Tunisia) with a high prevalence of
Borrelia infections in small rodents and insectivores and
Ornithodoros tick vectors [
11,
24].
Mastopmys natalensis frequently captured in both sites seems to be the principal reservoir of Lassa virus in West Africa [
25,
26]. Other small rodents like
P. daltoni and
M. erythrolocus identified as carriers of LASV IgG in Guinea are involved in the transmission of Lassa virus (LASV) to human [
27], then
Rattus rattus and
Crocidura spp. were found positive to LASV IgG in Nigeria [
28]. Human morbidity cases due to LASV are currently reported in Guinea, Sierra Leone, Liberia and Central African Republic [
23]. However, in Mali, a case of death, repatriated to health, observed in 2009 was reported in a member of an NGO working in southern Mali. There are many asymptomatic forms and only 1% of cases are reported to be fatal [
29]. In Senegal, positive serologies have been found in
M. erythroleucus, but no human cases are known. The emergence of hantavirus hemorrhagic fevers in West Africa has been caused by a threat
Crocidura theresae (C. obscurior) found infected by
Tanganya virus (TGNV), the only shrew-associated hantavirus reported to date from sub-Saharan Africa [
30]. Numerous positive serologies have also been reported throughout Senegal, with two hyperendemic foci identified in the southern regions, particularly involving the black rat
R. rattus. In Mauritania, opposite Bakel on the right bank of the Senegal River, positive serologies due to Crimean-Congo haemorrhagic fever virus (CCHF) have been reported in
M. erythroleucus and
Arvicanthis nilotucus [
23]. The CCHV has already been isolated from
Mastomys in the Central African Republic [
31]. Adam and Saluzzo [
32] suggest that small rodents may participate in an epizootic of CCHF and probably still in its amplification, but thus would not be involved in maintenance of infection. In July 2017, 2 imported cases from Mauritania and 1 indigenous case had been recorded in the Matam region. In September and November 2019, 1 human case of CCHF and then 1 other case were confirmed in the Matam and Fatick regions respectively. In August 2020, another case was reported by the epidemiological surveillance system of the Ministry of Health and Social Action of Senegal in the Pikine district of Dakar. An outbreak of human cases of CCHF in the department of Podor was reported in August 2022 by the World Health Organization (WHO). Presumably, there is currently an active outbreak of CCHF in Podor in the Saint-Louis region where 2 additional cases have been reported, one of which represents the first recorded case of CCHF-related death. In May 2022, another case attributed to this disease was detected and confirmed in the Matam region in the north of the country, after another case was recorded two months earlier in the Koumpentoum department of the Tambacounda region in eastern Senegal. CCHF disease, detected four times in a row in Senegal in 2022, appears to be a major public health concern, even at the level of the West African region. Evidence of the passage of antiviral antibodies to this virus has been identified in rodents in Nigeria, Senegal, Ethiopia, Namibia, Madagascar and Egypt, and
R. rattus could be involved in the amplification of the virus. In addition,
M. natalensis, R. rattus, and
C. olivieri abundant in both sites of our study were reported elsewhere with potential role in dissemination of Leptospira [
33], sewage disease frequent in urban and semi-urban areas, then in irrigated crop areas such as the Senegal Valley and that of Niono in Mali.
Mastomys sp. is involved in the spread of this disease in sub-Saharan Africa and its range may expand further when more extensive surveys are conducted [
23]. In Senegal, many species such as
R. rattus, Mastomys huberti,
A. niloticus and
M. erthroleucus identified as carriers of anti-Rift Valley fever (RVF) antibody play as potentiels reservoirs of RVF virus [
34]. Positive serologies have been encountered in the Senegal River valley in
M. erythroleucus and
R. rattus [
23]. Experimental infections have also shown that
M. erythroleucus could be an amplifying host during inter-epidemic transmission of this virus [
35]. The role of rodents as a potential host within the natural cycle of RVF virus in enzootic zone of Senegal is discussed, however highest antibody prevalence was recorded at Richard Toll (9.6%), within the enzootic area of Senegal River delta [
35].
The trapping yield was higher in Faladjè (23.58%) than in Bougouni (13.48%) while the capture effort was greater, and was comparable to that obtained in 3 villages in Mali [
36].
Mastomys erythroleucus and M. natalensis were the most frequently captured species at both study sites, but the predominance of
M. erythrolocus observed in this sampling has also been reported in other localities in Senegal [
10] where it is endemic. In an investigative study on Lassa fever in Mali, Safronetz and colleagues [
36] showed that the predominance of the genus
Mastomys sp. represented 79.6%.
Arvicanthis ansorgei was not collected at either site although this species had been reported in Mali [
37,
38] The absence of
Arvicanthis niloticus and/or A. ansorgei in our sample could be explained by the fact that the sampling was done at night when this species has a diurnal activity.
Rattus rattus which was more abundant in Bougouni was also found to be the predominant species in Algeria [
39]. Bougouni is a continental city, which explains why
Rattus. norvegicus often co-endemic with
R. rattus in African port cities is absent there. Study of small mammalian species reservoirs geographic distribution and habitat associations help define potential diseaseendemic areas and more precisely identify the spacial variation in relative risk to humans [
2].