[Susceptibility status of Anopheles gambiae s.s. and An. coluzzii to Organophosphates and Carbamates in the Agricultural Exploitation Zones of oil Palm at Mouila, Gabon]. / Susceptibilité d'Anopheles gambiae s.s. et An. coluzzii aux organophosphorés et aux carbamates en zones d'exploitation industrielle de palmiers à huile à Mouila, Gabon.

This study was conducted during the rainy season of 2017 in the agricultural areas at Mouila, with the aim to assess the determination of susceptibility of Anopheles gambiae complex to insecticides and the detection of Ace 1R mutation. Mosquito larvae were collected by using the dipping method and nursed to adult stage. The susceptibility of adult Anopheles gambiae s.l. populations to organophosphates and carbamates was assessed using the standard WHO susceptibility test protocol. The tested mosquitoes species were identified by PCR. These tested mosquitoes were used to search for the Ace 1R mutation. The insecticides used were pirimiphos-methyl 0.25% and 1.25%, fenitrothion 1%, malathion 5%, propoxur 0.1%, bendiocarb 0.1%, 0.5% and 1%. In the prospected areas, An. gambiae s.l. included An. gambiae s.s. and An. coluzzii sympatric in their larval habitats. However, An. gambiae s.s. was predominant in all studied areas (99.1%) comparatively to An. coluzzii Moreover, the susceptibility tests of Anopheles to organophosphates and carbamates revealed mortality rates of 100% regardless of the origin of the mosquitoes. PCR diagnosis of Ace 1R mutation showed that none tested mosquito (An. gambiae s.s. and An. coluzzii) from prospected areas harbored the Ace 1R gene in all prospected areas. The lack of Ace 1R mutation in An. gambiae s.l. reveals the current effectiveness of organophosphates and carbamates for the control of these mosquitoes. Bboth these classes of insecticides could be used for the anopheline populations control in the agricultural spaces at Mouila.

Cette étude a été menée en 2017 pendant la saison des pluies dans les zones d'exploitations agricoles à Mouila, afin de déterminer le statut de sensibilité des membres du complexe Anopheles gambiae aux insecticides et de rechercher la présence de la mutation Ace 1R. Les moustiques ont été collectés au stade larvaire par la méthode du « dipping ¼, puis élevés jusqu'au stade adulte. La susceptibilité des adultes d'An. gambiae s.l. aux organophosphorés et aux carbamates a été évaluée par la méthode standard de l'OMS concernant les tests de sensibilité aux insecticides. Les classes d'insecticides testées étaient les organophosphorés (pirimiphos-méthyl 0,25 % et 1,25 %, fénitrothion 1 %, malathion 5 %) et les carbamates (propoxur 0,1 %, bendiocarb 0,1 %, 0,5 % et 1 %). Les moustiques testés ont été identifiés par PCR. Les anophèles issus des tests ont été utilisés pour la recherche de la mutation Ace 1R par PCR. Dans les sites d'étude, Anopheles gambiae s.l. était composé d'An. gambiae s.s. et An. coluzzii vivant en sympatrie dans leurs habitats larvaires, avec une prédominance d'An. gambiae s.s. (99,1 %) sur An. coluzzii. Les tests de sensibilité des anophèles aux organophosphorés et aux carbamates ont révélé des taux de mortalité de 100 % quelle que soit l'origine des anophèles. La PCR diagnostique de la mutation Ace 1R a montré qu'aucun moustique issu des tests de sensibilité n'était porteur de gènes de résistance Ace 1R. L'absence de mutation Ace 1R chez An. gambiae s.l. révèle l'efficacité actuelle des carbamates et des organophosphorés dans la lutte contre ces moustiques. Ces familles d'insecticides pourraient être utilisées pour la lutte contre les anophèles dans les espaces agricoles de Mouila.

High Frequency of Trypanosoma congolense Savannah Type (Kinetoplastida: Trypanosomatidae) Among Tsetse Flies (Diptera: Glossinidae) in a Historic Trypanosoma Foci in North-Eastern Gabon: Preliminary Study [corrected].

Human African trypanosomiasis became a neglected disease after the 1960s, when case numbers dropped dramatically. It again became a public health problem in sub-Saharan Africa at the end of the 1990s, when new cases were reported, notably in Central Africa, and specifically in Gabon, where historic foci existed and new cases have been reported. Therefore, the present study reports on an entomological survey conducted in May 2012 to determine the pathogenic trypanosome infection rate in tsetse flies and characterize the diversity of Trypanosoma species in the Ivindo National Park (INP) in northeastern Gabon. Nine Vavoua traps were used to catch tsetse over a 7-days period. All tsetse flies captured were identified to species, dissected, and trypanosome species identified using polymerase chain reaction (PCR). In total, 160 tsetse flies were analyzed, including Glossina palpalis palpalis, Glossina fusca congolense, and Glossina tachinoïdes The trypanosome infection rate of the flies was 6.3 and 31.9% using microscopy and PCR, respectively. The species identified were Trypanosoma congolense savannah type, Trypanosoma brucei brucei, Trypanosoma brucei gambiense, Trypanosoma vivax, and Trypanosoma congolense forest type. Trypanosoma risk index was 0.75 and 7.05 for humans and for animals, respectively. This study illustrates the diversity of Trypanosoma species infecting the tsetse flies in the INP. The simultaneous occurrence of Trypanosoma and tsetse from the palpalis group may suggest that the reservoirs of African animal trypanosomiasis should be carefully monitored in this area.

Inventory of potential vectors of trypanosoma and infection rate of the Tsetse fly in the National Park of Ivindo, Gabon.

BACKGROUND: Trypanosoma's vectors distribution is poorly investigated in Gabon, where Trypanosomiasis historical foci exist. Thus, an active detection of Trypanosoma sp transmission needs to be assessed. OBJECTIVES: The present study aims to identify potential vectors of Trypanosoma sp and to evaluate the infection rate of the Tsetse fly in an area of Gabon. METHODS: An entomological survey was conducted in the National Park of Ivindo in May 2012 using Vavoua traps. All captured insects were identified. Tsetse were dissected and organs were microscopically observed to detect the presence of Trypanosoma sp. RESULTS: 247 biting flies known as vectors of Trypanosomiasis were caught including 189 tsetse flies, 32 Tabanid and 26 Stomoxys. Tsetse flies had the highest bulk densities per trap per day (ADT = 3 tsetse / trap / day), while the lowest density was found among Stomoxys (ADT= 0.41 Stomoxys / trap / day). The infection rate of flies was 6.3%. Infectious organs were midguts and to a lesser extent salivary glands and proboscis. CONCLUSION: The presence of Tsetse infected by Trypanosoma highlights an existing risk of trypanosomiasis infection in the National Park of Ivindo.

Is there a suburban sleeping sickness in Libreville?

BACKGROUND: The transmission of sleeping sickness occurs primarily in rural areas, and exposed populations are those living from rural activities such as agriculture, fishing, animal husbandry or hunting. However, urban and suburban foci are more and more reported in T. b. gambiense areas. In Libreville town, sleeping sickness cases are regularly diagnosed. In order to investigate about the establishment of a transmission cycle of that disease, we have carried out an entomological survey in two quarters in the vicinity of the town. METHODS: Vavoua traps were set out in all suitable biotopes for tsetse flies during four days and examined twice a day. Flies were collected, identified and dissected. RESULTS: Two species of Glossina were caught: G. palpalis palpalis (90.58%) and G. caliginea (9.42%). A total infection rate of 9.37% was observed after dissection of all non-teneral flies captured. CONCLUSION: These results suggest the establishment of a trypanosomiasis transmission cycle in the area. No salivary gland was found infected. Given that infected persons are regularly detected, we can think about the existence of a suburban sleeping sickness focus in Libreville. More analysis is needed concerning the identification of human trypanosomes and the origin of Glossina blood meals that may confirm the existence of that focus.

Spatio-temporal variation of biting flies, Stomoxys spp. (Diptera: Muscidae), along a man-made disturbance gradient, from primary forest to the city of Makokou (North-East, Gabon).

Understanding the pattern of abundance of vector populations is important to control the potential of transmission of associated pathogens. The pattern of abundance of Stomoxys Geoffroy, an ubiquitous blood-sucking fly, is poorly known in tropical Africa. In this study, we investigated the spatio-temporal pattern of abundance of the Stomoxys genus along a gradient of man-made disturbance in north-eastern Gabon. Three sites (one in primary forest, one in secondary forest and one in a man-made environment) were monitored during 13 months using Vavoua traps. Seven species and subspecies were found to live in sympatry, but with distinct patterns of abundance with respect to space and time. The most abundant species was Stomoxys transvittatus Villeneuve, whereas the rarest species was S. xanthomelas Roubaud. Stomoxys calcitrans Linné was preferentially found in man-made environments, whereas S. xanthomelas was preferentially found in primary forest. Stomoxys abundance was the greatest in secondary forest, then in man-made environments and finally in primary forest. A seasonal variation in Stomoxys abundance was also found. In conclusion, forest degradation and deforestation are likely both to favour the concentration of populations of Stomoxys, and to change the specific composition of the Stomoxys community.

[Abundance and species diversity of tabanids (Diptera) in the biosphere reserve Ipassa-Makokou (Gabon) during the rainy season]. / Chorologie des Tabanidae (Diptera) dans la réserve de biosphère Ipassa-Makokou (Gabon) en saison des pluies.

The abundance and species diversity of tabanids were evaluated by trapping of insects using Vavoua traps, during the rainy season, from October 4 to November 30, 2009, in three different habitats: primary forest, secondary forest and village, in the biosphere reserve Ipassa-IRET Makokou in Gabon. Eight species belonging to three genera of tabanids have been identified for a total of 402 specimens caught. The tabanid species numerically the most abundant were: Tabanus secedens Walker, 1854 (55.2%), Tabanus obscurehirtus Ricardo, 1908 (13.9%), Chrysops dimidiatus Wulp, 1885 (11.2%) and Chrysops silaceus Austen, 1907 (10.7%). The less abundant species were Tabanus par Walker, 1854 (3.2%), Tabanus besti arbucklei Austen, 1912 (3%), Tabanus marmorosus congoicola Bequaert, 1930 (1%) and Ancala fasciata fasciata (Fabricius, 1775) (0.5%). Specimens of the genera Tabanus and Chrysops could not be identified, these insects represented respectively 0.7% and 0.5% of the insects trapped. The highest proportion of tabanids was trapped in secondary forest (75.1%) and the lower in primary forest (4.5%).

Landscape, population structure and genetic diversity of Stomoxys calcitrans.

To investigate whether different landscapes could affect genetic diversity and structure of the cosmopolitan diptera Stomoxys calcitrans, populations from Gabon and southern France were studied using dominant amplified fragment length polymorphism (AFLP) markers. Gabon is characterized by a forested closed landscape, and southern France by an open Mediterranean landscape. The genetic diversity between Gabon and France populations did not differ significantly (P > 0.05). Contrary to our expectation, this study shows a moderate level of genetic differentiation between these two distant countries (Fst = 0.0979) and a low genetic structure among Gabonese and French populations (Fst = 0.0291 and 0.0275 respectively). This result could indicate the capacities of S. calcitrans populations to sustain a high level of gene flow, despite geographic distance and isolation.

[Ecology of Stomoxys flies (Diptera: Muscidae) in Gabon. I. First survey in different ecological areas]. / Ecologie des stomoxes (Diptera: Muscidae) au Gabon. I--Premier inventaire dans différentes zones ecologiques.

The stomoxyine flies are hematophagous diptera and potential vectors of various pathogenic agents. Like those of the Afrotropical Region, the stomoxyine flies of Gabon remain nearly unknown. For these reasons, an entomological survey was conducted in a transverse way in eight localities representative of the various ecological zones of Gabon. The survey was based on the use of Vavoua traps. Various environmental factors able to influence the captures were noticed and included into a canonical correspondence analysis. In total, 15,966 Stomoxys spp., belonging to seven species or subspecies, were captured. The apparent densities (DAP) expressed as the number of flies per trap and per day, were highest in Franceville (41), Bakoumba (40), Makokou (25) and Mouila (21). The most abundant species were S. n niger (33.4%), S. transvittatus (33%), then S. calcitrans (17%). The principal factors that could explain the variability of the captures were the degree of anthropisation, the botanical facies (savanna or forest), the presence of wild and domestic fauna and the nature of the vegetal cover of the ground. S. calcitrans, S. niger niger were abundant in the areas where human presence was manifest. S. xanthomelas was present in forest belts. S. transvittatus, S. omega, S. inornatus were ubiquitous species. S. niger bilineatus was found in savannas areas.

[Ecology of stomoxyine fulies (Diptera: Muscidae) in Gabon. II. Blood meals analysis a nd epidemiologic consequences]. / Ecologie des stomoxes (Diptera: Muscidae) au Gabon. II. Origine des repas de sang et conséquences epidémiologiques.

To determine the origin of stomoxyine fly bloodmeals (Diptera: Muscidae) in Gabon, 1,021 flies belonging to seven different species of Stomoxys were captured and dissected in the area of Makokou. In total, 798 were not blood-fed and 223 bloodmeals could be gathered on filter paper. The identification of the origin of these meals was made by amplification of mitochondrial Cytb gene, then heteroduplex technique by using the Gambian rat (Cricetomys gambianus) as driver. Samples of fauna, collected on the local market, consisted of 24 mammal and two reptile blood and muscle samples, to which it is necessary to add human samples (27 potential hosts). 19 meals could not be amplified for technical reasons, 65 were amplified, but the acquired patterns corresponded to none of the tested potential hosts. On the 139 identified meals, 55% were taken on the black-fronted duiker (Cephalophus nigrifrons) and 19% on pig. Stomoxys transvittatus, the most abundant species in Makokou, is very opportunistic: 68 % of meals were taken on six different hosts, among whom 48% on the black-fronted duiker and 32% were not identified using the panel of tested hosts. S. xanthomelas took 50% of its meals on the moustached monkey (Cercopithecus cephus) and 7% on human beings. S. calcitrans, species of anthropised areas, took 33% of its meals on human beings. These three species can therefore take bloodmeals on wild fauna and human beings. They could potentially play an important role in the emergence of zoonotic diseases. The four other species took their bloodmeals only on wild fauna and pig, the only example of domestic fauna in this study. This preliminary study must be followed up using a larger number of specimens and by increasing the diversity of the tested potential hosts.