[Characterization of contacts of the population of Guinea with synanthropic rodents as Lassa fever virus carriers].

Questionnaire surveys made in 17 villages from 3 ecological zones of Guinea have provided evidence for the population's contact with synanthropic rodents as Lassa fever virus carriers. Over 100 rodents are quarterly captured in the houses of the traditional type in the villages located in the savanna woodland. Less than 10 specimens are captured at the food warehouses. There are more than 100 rodents in the majority of houses of the traditional type in the villages located in the secondary forest. In the villages of rainy tropical forests, the capture rate is low--10 to 100 rodents. The main rodent capturers are boys and young men (aged 7 to 20 years) who are principal rodent meat eaters; although almost the whole population, particularly in rural areas, consumes this meat in varying degrees. The proportion of captured rats of the genus Mastomys (the carrier of Lassa fever virus) in the town of Kindia is 11%. In the rural area, it is much higher (as high as 94%) in the villages located in the rainy tropical forests. It is estimated that one trapper quarterly catches 0.2 (in the savanna woodland) to 6.9 (in the secondary forests) infected rats, which agrees with the data of a serological survey of Guinea's population. By and large, the majority of the Guinean population may be referred to as a group at risk for Lassa fever due to their permanent contacts with rodents.

[Problems with envenomations in Guinea]. / Problématique des envenimations en Guinée.

Only a few years after its creation, the Kindia Pasteur Institute (currently Institut de Recherche de Biologie Appliquée de Guinée, IRBAG), owing to its geographical situation, began regularly supplying the Paris Pasteur Institute with snake venom for manufacturing antivenom. The diversity of the biotopes in Guinea due mainly to the diversity of vegetation (savannah, forest, mangrove) and altitudes (coastal zone, mountains of Fouta-Djalon and mountain of High Guinea), induces a wide variety of the herpetological fauna. Envenomations are consequently a significant cause of morbidity and mortality in a country where agriculture is an important economic activity. Unfortunately, precise statistics for envenomations are unavailable. A retrospective study was performed based on IRBAG registers (1980-1990). A total of 584 snakebites were reported with a 2.2% case fatality rate. Between 1997 and 1999, 379 cases of snakebites were reported with 18.2% death, mainly due to the lack of antivenom, and 2.1% amputations. By combining the fang marks and victim or relative assessments, we were able to identify most of the snakes involved in the envenomations: Naja (21.3%), Bitis (15%), Dendroaspis (12.4%) and Causus (12.9%). In 38.2% of the cases, the snake was not identified. This survey confirmed that envenomations are a problem in Guinea. However, more studies are necessary to appreciate the real importance of the herpetological Guinean fauna and its consequences on morbidity and mortality in order to improve the management of envenomations.

Lassa fever in Guinea: II. Distribution and prevalence of Lassa virus infection in small mammals.

Rodents of the genus Mastomys form the reservoir for Lassa virus (LV), an arenavirus that causes a potentially severe hemorrhagic illness, Lassa fever (LF). Although Mastomys rodents exist throughout sub-Saharan Africa, areas of human LF appear to be quite focal. The distribution of small mammals and LV-infected Mastomys has been assessed in only a few countries. We conducted a survey of small mammals in selected regions of Guinea to assess the degree to which LV poses a public health risk in that country. A total of 1,616 small mammals, including 956 (59%) Mastomys, were captured from 444 households and seven bush sites. Mastomys made up > 90% of the captured animals in the savannah, savannah-forest transition, and forest regions of Guinea, while Mus musculus dominated in coastal and urban sites. Animals were analyzed via enzyme-linked immunosorbent assay (ELISA) for LV-specific antigen (blood and spleen homogenate) and IgG antibody (blood only). Virus isolation from spleen homogenates was also performed on a subset of animals. Lassa antibody and antigen were found in 96 (11%) and 46 (5%), respectively, of 884 tested Mastomys. Antibody and antigen were essentially mutually exclusive and showed profiles consistent with vertical transmission of both LV and antibody. LV was isolated only from Mastomys. ELISA antigen constituted an acceptable surrogate for virus isolation, with a sensitivity and specificity when performed on blood of 78% (95% confidence interval: 68-83%) and 98% (95-99%), respectively. The proportion of LV-infected Mastomys per region ranged from 0 to 9% and was highest in the savannah and forest zones. The proportion of infected animals per village varied considerably, even between villages in close proximity. Infected animals tended to cluster in relatively few houses, suggesting the existence of focal "hot spots" of LV-infected Mastomys that may account for the observed heterogeneous distribution of LF.

Hunting of peridomestic rodents and consumption of their meat as possible risk factors for rodent-to-human transmission of Lassa virus in the Republic of Guinea.

In this population-based study, we correlated possible risk factors for rodent-to-human transmission of Lassa virus with markers of Lassa fever in two different regions of the Republic of Guinea (Prefectures of Pita and Gueckedou). Antibody prevalence was 2.6% (6 of 232) in Pita compared with 14.0% (105 of 751) in Gueckedou, with up to 35.0% seropositivity in selected villages of the higher prevalence area. We observed three major risk factors in Gueckedou favoring Lassa virus transmission: rodent infestation was much higher, food was more often stored uncovered and most strikingly, peridomestic rodents were hunted as a protein source by 91.5% of the population as opposed to 0% in Pita. To control for the confounding effects of differences in rodent infestation and food storage, rodent consumption was analyzed as a risk factor for transmission of Lassa virus comparing rodent consumers (RC) and nonconsumers (NC) in Gueckedou only: 14.6% of RC had Lassa virus antibodies versus 7.4% of NC (P = 0.1) and 23.0% of RC reported a history of a febrile illness with hearing loss (the most common sequel of Lassa fever) versus 6.1% of NC (P = 0.003).

[Clinico-epidemiologic and laboratory research on hemorrhagic fevers in Guinea]. / Eléments de recherches clinico-épidémiologiques et de laboratoire sur les fièvres hémorragiques en Guinée.

In 1982-1983, were reported the cases of haemorrhagic fevers among populations living in the Madina-Ula district of Guinea. Clinico-epidemiological and serological studies (experimental studies) reveal into presumption of Ebola and Lassa fever viruses significance in the etiology of the disease outbreaks. Antibodies to Ebola virus were recognized in 19% from total number of sweating reconvalescent patients with the same clinical features, in order to 8% in healthy local populations. Antibodies to Lassa virus were detected in 3 cases, in 4 cases was revealed Lassa virus antigen in small rodents.

[Isolation of the Fomédé virus from Chiroptera, Nycteris nana, in the Republic of Guinea]. / Isolement du virus Fomédé à partir de chéiroptères Nycteris nana en République de Guinée.

In October 1978, a new virus named Fomédé was recovered from the bat, Nycteris nana, during the studies of arbovirus infections in Guinea (West Africa). When the virus was tested, it did not fit any prototype patterns. These findings have led to a presumption that the ch. s. 654 strain of virus is a previously unknown virus due to its biological, physico-chemical and antigenic patterns.