Effects of permethrin-impregnated bednets on Anopheles gambiae s.l. in the Gambia.

A National Impregnated Bednet Programme (NIBP) was implemented in The Gambia covering all the villages with a primary health centre (PHC). The evaluation of the programme included epidemiology, entomology and social aspects. This thesis is part o f the entomological evaluation. Populations of Anopheles gambiae s.l. were found to be as long lived, abundant and infective in villages with permethrin-impregnated bednets as in villages with untreated bednets, confirming the lack of a "mass-killing effect", and the absence of a repellent effect of treated bednets at village level. Movements of mosquitoes between PHC villages was assessed and found that overall, 17% (C.I. 11.02%-26.71%) were immigrant mosquitoes from neighbouring villages. This amount of movements between villages may explain the difference between The Gambia and other African countries in which a clear "mass-killing effect" has been seen after the introduction of impregnated bednets. In the absence of a "mass-killing effect" the question arises of how protection against malaria in children is therefore achieved. Studies on the biting behaviour of the vector population were made to see if mosquitoes were diverted to bite outdoors, shifted the biting time, were prevented or delayed to feed or were diverted to bite other hosts rather than children. No evidence was found for a difference between treated and untreated villages in biting location ( Indoors:Outdoors), mean biting time or human blood index of indoor resting mosquitoes. An indication was observed that the gonotrophic cycle length of An. gambiae s.l. was 2 days in untreated villages. No evidence of a change in the gonotrophic cycle length was found in the presence of treated bednets, although the number of mosquitoes were low to be conclusive. The density of indoor resting mosquitoes was significantly lower in the presence of treated bednets than in the presence of untreated ones, difference probably due to the excito-repellent effect of the insecticide. A study in which mosquito bloodmeals from children could be differentiated from bloodmeals from other hosts (adults and animals) was undertaken. A significant reduction in the proportion of bloodmeals that were apparently taken from children was found in the presence of treated bednets. However, it is not clear whether these results are reliable. Assuming that they are, this could explain the way in which children are protected against malaria by the use of treated bednets. A comparative study was carried out in two villages to see if entomological factors were part of the reasons that caused the NIBP not to be as effective in Zone 5 as in the other Zones. Some entomological differences were found between Zones 5 and 3 and those included: a higher proportion of An. arabiensis in Zone 5 (40%) than in Zone 3 (20%), a significantly higher frequency of the inversions j and d in the chromosome 2R in An. gambiae s.s.. an exophilic tendency of fed females in Zone 5 and lower densities but higher sporozoite rates, resulting in a higher EIR in Zone 5 than in Zone 3. Other parameters evaluated showed no significant difference including biting cycle, Indoor:Outdoor ratios, persistence of the insecticide in the bednets and no evidence was found that the treatment had a differential effect regarding the type of rooms. Levels of bednet usage were probably more significant than these entomological parameters as a cause of the observed differences between zones of the epidemiological impact of treated bednets. The relative sampling efficiency of human landing collections were compared with light traps, exit traps and pyrethrum spray catches. In general there were few significant correlations between methods, due probably to night to night and house to house vernation and a limited sampling in both duration and geographical extension. DNA probes were compared with cytogenetics for the determination of the species of the An. gambiae complex. For the identification of An. gambiae s.s. and An. arabiensis DNA probes were shown to be as reliable as cytogenetics. However, a limitation was the variability between batches of probes. Also, the cross-reaction between the probes pAngss and pAnM14 made difficult the differentiation of An. gambiae s.s. and An. melas

Advantages and Limitations of Commercially Available Electrocuting Grids for Studying Mosquito Behaviour.

Mosquito feeding behaviour plays a major role in determining malaria transmission intensity and the impact of specific prevention measures. Human Landing Catch (HLC) is currently the only method that can directly and consistently measure the biting rates of anthropophagic mosquitoes, both indoors and outdoors. However, this method exposes the participant to mosquito-borne pathogens, therefore new exposure-free methods are needed to replace it. Commercially available electrocuting grids (EGs) were evaluated as an alternative to HLC using a Latin Square experimental design in Dar es Salaam, Tanzania. Both HLC and EGs were used to estimate the proportion of human exposure to mosquitoes occurring indoors (πi), as well as its two underlying parameters: the proportion of mosquitoes caught indoors (Pi) and the proportion of mosquitoes caught between the first and last hour when most people are indoors (Pfl). HLC and EGs methods accounted for 69% and 31% of the total number of female mosquitoes caught respectively and both methods caught more mosquitoes outdoors than indoors. Results from the gold standard HLC suggest that An. gambiae s.s. in Dar es Salaam is neither exophagic nor endophagic (Pi ≈ 0.5), whereas An. arabiensis is exophagic (Pi < < 0.5). Both species prefer to feed after 10 pm when most people are indoors (Pfl > >0.5). EGs yielded estimates of Pi for An. gambiae s.s., An. arabiensis and An. coustani, that were approximately equivalent to those with HLC but significantly underestimated Pfl for An. gambiae s.s. and An. coustani. The relative sampling sensitivity of EGs declined over the course of the night (p ≤ 0.001) for all mosquito taxa except An. arabiensis. Commercial EGs sample human-seeking mosquitoes with high sensitivity both indoors and outdoors and accurately measure the propensity of Anopheles malaria vectors to bite indoors rather than outdoors. However, further modifications are needed to stabilize sampling sensitivity over a full nocturnal cycle so that they can be used to survey patterns of human exposure to mosquitoes

Comparative Genotyping of Campylobacter jejuni Strains from Patients with Guillain-Barré Syndrome in Bangladesh

Background: Campylobacter jejuni is a common cause of acute gastroenteritis and is associated with post-infectious neuropathies such as the Guillain-Barré syndrome (GBS) and the Miller Fisher syndrome (MFS). We here present comparative genotyping of 49 C. jejuni strains from Bangladesh that were recovered from patients with enteritis or GBS. All strains were serotyped and analyzed by lipo-oligosaccharide (LOS) genotyping, amplified fragment length polymorphism (AFLP) analysis, multilocus sequence typing (MLST), and pulsed-field gel electrophoresis (PFGE). Methodology/Principal Findings: C. jejuni HS:23 was a predominant serotype among GBS patients (50%), and no specific serotype was significantly associated with GBS compared to enteritis. PCR screening showed that 38/49 (78%) of strains could be assigned to LOS classes A, B, C, or E. The class A locus (4/7 vs 3/39; p<0.01) was significantly associated in the GBS-related strains as compared to enteritis strains. All GBS/oculomotor related strains contained the class B locus; which was also detected in 46% of control strains. Overlapping clonal groups were defined by MLST, AFLP and PFGE for strains from patients with gastroenteritis and GBS. MLST defined 22 sequence types (STs) and 7 clonal complexes including 7 STs not previously identified (ST-3742, ST-3741, ST-3743, ST-3748, ST-3968, ST-3969 and ST-3970). C. jejuni HS:23 strains from patients with GBS or enteritis were clonal and all strains belonged to ST-403 complex. Concordance between LOS class B and ST-403 complex was revealed. AFLP defined 25 different types at 90% similarity. The predominant AFLP type AF-20 coincided with the C. jejuni HS:23 and ST-403 complex. Conclusion/Significance: LOS genotyping, MLST, AFLP and PFGE helped to identify the HS:23 strains from GBS or enteritis patients as clonal. Overall, genotypes exclusive for enteritis or for GBS-related strains were not obtained although LOS class A was significantly associated with GBS str

Yeasts associated with the production of distilled alcoholic beverages

Distilled alcoholic beverages are produced firstly by fermenting sugars emanating from cereal starches (in the case of whiskies), sucrose-rich plants (in the case of rums), fructooligosaccharide-rich plants (in the case of tequila) or from fruits (in the case of brandies). Traditionally, such fermentations were conducted in a spontaneous fashion, relying on indigenous microbiota, including wild yeasts. In modern practices, selected strains of Saccharomyces cerevisiae are employed to produce high levels of ethanol together with numerous secondary metabolites (eg. higher alcohols, esters, carbonyls etc.) which greatly influence the final flavour and aroma characteristics of spirits following distillation of the fermented wash. Therefore, distillers, like winemakers, must carefully choose their yeast strain which will be very important in providing the alcohol content and the sensory profiles of spirit beverages. This Chapter discusses yeast and fermentation aspects associated with the production of selected distilled spirits and highlights similarities and differences with the production of wine

Man-biting Activity of Anopheles (Nyssorhynchus) albimanus and An. (Kerteszia) neivai (Diptera: Culicidae) in the Pacific Lowlands of Colombia

The daily man-biting activity of Anopheles (Nyssorhynchus) albimanus and An. (Kerteszia) neivai was determined in four ecologically distinct settlements of the Naya River, Department of Valle, Colombia. Differences were found among the settlements with respect to the mosquito species present, intradomiciliary and extradomiciliary biting activity and population densities

Effectiveness of influenza vaccine against laboratory-confirmed influenza, in the late 2011-2012 season in Spain, among population targeted for vaccination

Background: In Spain, the influenza vaccine effectiveness (VE) was estimated in the last three seasons using the observational study cycEVA conducted in the frame of the existing Spanish Influenza Sentinel Surveillance System. The objective of the study was to estimate influenza vaccine effectiveness (VE) against medically attended, laboratory-confirmed influenza-like illness (ILI) among the target groups for vaccination in Spain in the 2011-2012 season. We also studied influenza VE in the early (weeks 52/2011-7/2012) and late (weeks 8-14/2012) phases of the epidemic and according to time since vaccination. Methods: Medically attended patients with ILI were systematically swabbed to collect information on exposure, laboratory outcome and confounding factors. Patients belonging to target groups for vaccination and who were swabbed 4 months, respectively, since vaccination. A decrease in VE with time since vaccination was only observed in individuals aged ≥ 65 years. Regarding the phase of the season, decreasing point estimates were only observed in the early phase, whereas very low or null estimates were obtained in the late phase for the shortest time interval. Conclusions: The 2011-2012 influenza vaccine showed a low-to-moderate protective effect against medically attended, laboratory-confirmed influenza in the target groups for vaccination, in a late season and with a limited match between the vaccine and circulating strains. The suggested decrease in influenza VE with time since vaccination was mostly observed in the elderly population. The decreasing protective effect of the vaccine in the late part of the season could be related to waning vaccine protection because no viral changes were identified throughout the season