Effect of textile colour on vector mosquito host selection: a simulated field study in Mali, West Africa.

BACKGROUND: The effect of clothing colour on the biting rates of different vector mosquito species is not well understood. Studies under tropical field conditions are lacking. This study aimed to determine the influence of clothing colours on mosquito biting rates in rural and suburban settings in West Africa. METHODS: We performed a simulated field study in a suburban and a rural site in Mali using Mosquito-Magnet traps utilizing CO2 and other attractants, which were covered with black, white, and black/white striped textile sheets covers. These targets operated continuously for 10 consecutive days with bright nights (around full moon) and 10 consecutive days with dark nights (around new moon). Trapped mosquitoes were collected and catch rates counted hourly. Mosquitoes were morphologically identified to the species complex level (Anopheles gambiae s.l. and Culex pipiens s.l.) or species level (Aedes aegypti). A subset of Anopheles specimens were further identified by molecular methods. RESULTS: Under bright-night conditions, An. gambiae s.l. was significantly more attracted to black targets than to white and striped targets; during dark nights, no target preference was noted. During bright nights, Cx. pipiens s.l. was significantly more attracted to black and striped targets than to white targets; a similar trend was noted during dark nights (not significant). For day-active Ae. aegypti, striped targets were more attractive than the other targets and black were more attractive than white targets. CONCLUSIONS: The study firstly demonstrated that under field conditions in Mali, West Africa, mosquito catch rates were influenced by different clothing colours, depending on mosquito species and light conditions. Overall, light colours were least attractive to host-seeking mosquitoes. Using white or other light-coloured clothing can potentially reduce bite exposure and risk of disease transmission in endemic tropical regions.

Effects of insemination and blood-feeding on locomotor activity of wild-derived females of the malaria mosquito Anopheles coluzzii.

BACKGROUND: Behavioural shifts in the canonical location and timing of biting have been reported in natural populations of anopheline malaria vectors following the implementation of insecticide-based indoor vector control interventions. These modifications increase the likelihood of human-vector contact and allow mosquitoes to avoid insecticides, both conditions being favourable to residual transmission of the malarial parasites. The biting behaviour of mosquitoes follows rhythms that are under the control of biological clocks and environmental conditions, modulated by physiological states. In this work we explore modifications of spontaneous locomotor activity expressed by mosquitoes in different physiological states to highlight phenotypic variability associated to circadian control that may contribute to explain residual transmission in the field. METHODS: The F10 generation progeny of field-collected Anopheles coluzzii from southwestern Burkina Faso was tested using an automated recording apparatus (Locomotor Activity Monitor, TriKinetics Inc.) under LD 12:12 or DD light regimens in laboratory-controlled conditions. Activity recordings of each test were carried out for a week with 6-day-old females belonging to four experimental treatments, representing factorial combinations of two physiological variables: insemination status (virgin vs inseminated) and gonotrophic status (glucose fed vs blood fed). Chronobiological features of rhythmicity in locomotor activity were explored using periodograms, diversity indices, and generalized linear mixed modelling. RESULTS: The average strength of activity, onset of activity, and acrophase were modulated by both nutritional and insemination status as well as by the light regimen. Inseminated females showed a significant excess of arrhythmic activity under DD. When rhythmicity was observed in DD, females displayed sustained activity also during the subjective day. CONCLUSIONS: Insemination and gonotrophic status influence the underlying light and circadian control of chronobiological features of locomotor activity. Overrepresentation of arrhythmic chronotypes as well as the sustained activity of inseminated females during the subjective day under DD conditions suggests potential activity of natural populations of A. coluzzii during daytime under dim conditions, with implications for residual transmission of malarial parasites.

Multicentre studies of insecticide-treated durable wall lining in Africa and South-East Asia: entomological efficacy and household acceptability during one year of field use.

BACKGROUND: Indoor residual spraying (IRS) is a primary method of malaria vector control, but its potential impact is constrained by several inherent limitations: spraying must be repeated when insecticide residues decay, householders can tire of the annual imposition and campaign costs are recurrent. Durable lining (DL) can be considered an advanced form of long-lasting IRS where insecticide is gradually released from an aesthetically attractive wall lining material to provide vector control for several years. A multicentre trial was carried out in Equatorial Guinea, Ghana, Mali, South Africa and Vietnam to assess the feasibility, durability, bioefficacy and household acceptability of DL, compared to conventional IRS or insecticide-treated curtains (LLITCs), in a variety of operational settings. METHODS: This study was conducted in 220 households in traditional rural villages over 12-15 months. In all sites, rolls of DL were cut to fit house dimensions and fixed to interior wall surfaces (usually with nails and caps) by trained teams. Acceptability was assessed using a standardized questionnaire covering such topics as installation, exposure reactions, entomology, indoor environment, aesthetics and durability. Bioefficacy of interventions was evaluated using WHO cone bioassay tests at regular intervals throughout the year. RESULTS: The deltamethrin DL demonstrated little to no decline in bioefficacy over 12-15 months, supported by minimal loss of insecticide content. By contrast, IRS displayed a significant decrease in bioactivity by 6 months and full loss after 12 months. The majority of participants in DL households perceived reductions in mosquito density (93%) and biting (82%), but no changes in indoor temperature (83%). Among those households that wanted to retain the DL, 73% cited protective reasons, 20% expressed a desire to keep theirs for decoration and 7% valued both qualities equally. In Equatorial Guinea, when offered a choice of vector control product at the end of the trial (DL, IRS or LLITCs), DL consistently emerged as the most popular intervention regardless of the earlier household allocation. CONCLUSIONS: Just as long-lasting insecticidal nets overcame several of the technical and logistical constraints associated with conventionally treated nets and then went to scale, this study demonstrates the potential of DL to sustain user compliance and overcome the operational challenges associated with IRS.

Hydric stress-dependent effects of Plasmodium falciparum infection on the survival of wild-caught Anopheles gambiae female mosquitoes.

BACKGROUND: Whether Plasmodium falciparum, the agent of human malaria responsible for over a million deaths per year, causes fitness costs in its mosquito vectors is a burning question that has not yet been adequately resolved. Understanding the evolutionary forces responsible for the maintenance of susceptibility and refractory alleles in natural mosquito populations is critical for understanding malaria transmission dynamics. METHODS: In natural mosquito populations, Plasmodium fitness costs may only be expressed in combination with other environmental stress factors hence this hypothesis was tested experimentally. Wild-caught blood-fed Anopheles gambiae s.s. females of the M and S molecular form from an area endemic for malaria in Mali, West Africa, were brought to the laboratory and submitted to a 7-day period of mild hydric stress or kept with water ad-libitum. At the end of this experiment all females were submitted to intense desiccation until death. The survival of all females throughout both stress episodes, as well as their body size and infection status was recorded. The importance of stress, body size and molecular form on infection prevalence and female survival was investigated using Logistic Regression and Proportional-Hazard analysis. RESULTS: Females subjected to mild stress exhibited patterns of survival and prevalence of infection compatible with increased parasite-induced mortality compared to non-stressed females. Fitness costs seemed to be linked to ookinetes and early oocyst development but not the presence of sporozoites. In addition, when females were subjected to intense desiccation stress, those carrying oocysts exhibited drastically reduced survival but those carrying sporozoites were unaffected. No significant differences in prevalence of infection and infection-induced mortality were found between the M and S molecular forms of Anopheles gambiae. CONCLUSIONS: Because these results suggest that infected mosquitoes may incur fitness costs under natural-like conditions, they are particularly relevant to vector control strategies aiming at boosting naturally occurring refractoriness or spreading natural or foreign genes for refractoriness using genetic drive systems in vector populations.

[The treatment of tibia open fractures by Hoffmann external fixation in Niamey. About 50 cases]. / Le fixateur externe de Hoffmann dans la prise en charge des fractures ouvertes de jambe a Niamey. A propos de 50 cas.

UNLABELLED: The authors present the results of a retrospective study performed during 12 months; about 50 open fractures of tibia, treated by Hoffmann external fixation entirely or partially. The mean age was 33 years (6 years to 60 years). Forty (80%) patients had sustained the fracture in road traffic. According to Cauchoix system: 30 (60%) tibia open fracture was type I, 8 (16%) type II, and type III 12 (24%). 20 patients treated by external fixation following by internal fixation (plate), 10 patients treated by external fixation following by cast; 20 patients treated by external fixation only. The mean bone healing time was 7.5 month COMPLICATIONS: infections 6%, non-union 5 patients. Hoffmann external fixation is an excellent and safe method for the management of tibial open fractures.

Outcome of life-threatening malaria in African children requiring endotracheal intubation.

BACKGROUND: Little is known about children undergoing critical care for malaria. The purpose of this survey was to evaluate the outcome in African children requiring endotracheal intubation for life-threatening malaria. METHODS: All children with a primary diagnosis of severe malaria (2000 WHO definition) requiring endotracheal intubation, hospitalised over a five-year period, within a tertiary-care hospital in Dakar, Senegal, were enrolled in a retrospective cohort study. RESULTS: 83 consecutive patients were included (median PRISM h24 score: 14; IQR: 10-19, multiple organ dysfunctions: 91.5%). The median duration of ventilation was 36 hrs (IQR: 4-72). Indications for intubation were deep coma (Glasgow score

Prognostic value of thrombocytopenia in African children with falciparum malaria.

Thrombocytopenia is a common finding in malaria, but its prognostic value has not been addressed in children. The relationship between thrombocytopenia (platelet count < 100,000/mm3 on admission) and severity and outcome was investigated prospectively in children hospitalized with falciparum malaria in Dakar, Senegal, an area that is hypoendemic for malaria. Of 288 falciparum cases, 215 matched the 2000 World Health Organization definition of severe malaria. Median platelet counts were lower (98,000/mm3 versus 139,000/mm3; P < 0.02) among severe cases than in mild cases, and in children who died than among those who recovered (68,500/mm3 versus 109,000/mm3; P < 0.002). In severe cases, children presenting with a platelet count < 100,000/mm3 were more likely to die (odds ratio [OR] = 6.31, 95% confidence interval [CI] = 2.0-26.0). Moreover, multivariate analysis identified thrombocytopenia as an independent predictor of death (OR = 13.3, 95% CI = 3.2-55.1). Our data show an association between thrombocytopenia and either severity or prognosis in childhood falciparum malaria.

The potential role of rodents in the enzootic cycle of Rift Valley fever virus in Senegal.

Wild rodents (214) of fourteen species were trapped at seven sites in Senegal. Arvicanthis niloticus and Mastomys erythroleucus were among the most frequently collected species (77.2% of total capture). All rodents were examined for the presence of anti-Rift Valley fever virus (RVFV) antibody; the prevalence over all sampled species was 3.8%, varying widely with respect to species and location. Four of 14 species of rodents were found to have anti-RVFV antibodies: Rattus rattus (one positive of two tested) Mastomys huberti (13.5%), A. niloticus (4.3%), and M. erthroleucus (2.4%). The highest prevalence of anti-RVFV antibody was recorded within the enzootic area of the Senegal River delta, at Richard Toll (9.6%). A. niloticus and M. erythroleucus and a strain of laboratory-bred mice were experimentally inoculated with two strains of RVFV and examined for viremia, illness, seroconversion and mortality. A. niloticus and M. erythroleucus demonstrated a limited resistance to infection, thus potentially allowing for the replication of virus in these animals and making these species possible candidates as hosts in the maintenance cycle of RVFV in nature.

[Appendicitis in Niger: current prognosis]. / Les appendicites au Niger: pronostic actuel.

Acute appendicitis remains one of the most frequent emergencies in abdominal surgery. Surgery is usually straightforward and prognosis excellent. However, outcome depends essentially on how soon diagnosis is made. In Niger, the 1990s were marked by the development of private medicine and the deterioration of services in state health structures (health centres and hospitals). The goal of this prospective study, carried out over 24 months (March 1997-March 1999) was to analyse existing appendicitis prognosis in our country. The study population was made up of 362 patients and we based our survey on a number of factors found in the medical literature, and in particular on a similar study conducted in the same hospital in 1989 by another group of surgeons. Delays in diagnosis and thus therapy still today tends to transform prognosis for simple acute appendicitis into that of peritonitis. The numerous and varied post-operative complications keep the mortality rate at 4%.

[Surveillance of HIV seroprevalence in Mauritania]. / Surveillance de la séroprévalence du VIH en Mauritanie.

The results of our study in four years, blood donors and tuberculosis patients HIV seroprevalence using ELISA for detection HIV1/HIV2 antibodies and Western-blot for confirmation, indicate that seroprevalence in blood donors is 0.28% without a significant increase tendency. Our data show that 88 HIV seropositive confirmed, 70% were HIV1, 25% HIV2 and 5% double reactivity HIV1/HIV2.

Le fixateur externe de Hoffmann dans la prise en charge des fractures ouvertes de jambe a Niamey; a propos de 50 cas

Introduction : Le fixateur demeure une indication en cas de fracture ouverte des os longs avec perte ou non de substances .Le fixateur externe de Hoffmann; grace au principe de l'osteotaxis presente plusieurs avantages dans la prise en charge des fractures ouvertes de jambe . But : le but de ce travail etait de montrer les avantages lies a l'usage du fixateur externe de Hoffmann dans la prise en charge de la fracture ouverte de jambe .Materiels et Methode : Sur une periode de 12 mois ; les auteurs ont collige 50 fractures ouvertes de jambe ; qui provenaient de la ville de Niamey et des districts sanitaires environ ants . Il s'agissait d'une etude retrospective menee de Septembre 2005 a Aout 2006. Ont ete inclus dans cette etude ; les patients qui ont ete admis aux urgences pour fracture ouverte de jambe ; traitee par le fixateur externe de Hoffmann ; en totalite ou en partie et qui ont ete operes dans la periode de l'etude . Les patients ont ete reparti en en trois groupes : -groupe 1 :le fixateur a ete utilise exclusivement jusqu'a la consolidation. -groupe 2 :le fixateur externe suivi de platre. -groupe 3 : le fixateur externe suivi d'une osteosynthese interne. Resultats : Il s'agissait de 45 hommes et de 5 femmes ;L'age moyen etait de 33ans (6 ans a 60ans). Les AVP constituaient la premiere cause de fractures ouvertes avec 40(80) cas. L'ouverture de type I de Cauchoix representait 30(60) cas ; le type II represente 8(16) ; et le type III 12(24.) ; Sur le plan therapeutique les patients ont ete classes en trois : groupe1 soit 20 cas le fixateur a ete utilise comme l'unique methode de traitement ; groupe II 20 cas chez lesquels le fixateur externe a ete remplace en cours de traitement par une osteosynthese interne ; groupe III chez lesquels le fixateur a ete remplace a mi-parcours par un platre cruro- pedieux soit 10 cas. Le delais moyen de consolidation etait de 7;5 mois .. 6d'infections et 5cas de pseudarthroses ont ete enregistrees. Conclusion : Le fixateur externe de Hoffmann demeure une solution therapeutique accessible dans le contexte de l'etude ; evite pas mal d'amputations; procure une fixation stable; autorise la chirurgie reparatrice et permet au moment propice la conversion en osteosynthese interne ou son remplacement par un appareil platre