Thesis (Ph.D.)--University of the Witwatersrand, Faculty of Health Sciences, 2013. / Anopheles arabiensis is one of the major African malaria vectors, and DDT and pyrethroid resistance in this species is widespread. The aim of this study was to investigate, in detail, what detoxification enzymes are associated with insecticide resistance using the An. gambiae “detox chip”, a small-scale microarray based on genes that are putatively involved in metabolic detoxification of insecticides. The first part of the study focused on two DDT and pyrethroid resistant laboratory strains of An. arabiensis – one that originated from Sudan, and a second that originated from South Africa. One P450 was over-transcribed in the Sudanese strain, while 20 genes were over-transcribed in the South African strain. The majority of these were P450s although GSTs and redox genes were also over-transcribed. The use of synergist assays indicated that DDT and permethrin resistance were related to the presence of a kdr mutation (determined by PCR), while deltamethrin resistance was based on insecticide metabolism. In order to evaluate the role of enzymatic detoxification in permethrin resistance, a permethrin selected strain was used. No kdr mutations were present in this strain. Here, 29 genes were over-transcribed. Most of these were CYP genes (55%), followed by redox genes (21%), and GSTs (14%). A certain degree of overlap in the gene over-transcription was observed between the deltamethrin and permethrin resistant phenotypes. These genes are potentially functional against both pyrethroids, while those that differed were possibly more substrate specific. The final part of the study aimed to assess whether genes that are associated with insecticide resistance are also induced in mosquitoes infected with the entomopathogen, Beauveria bassiana. Using microarray data, a subset of important insecticide resistance genes was chosen for analysis following fungal infection. This study was based on the use of qPCR to detect changes in expression. None of the genes that were investigated were overtranscribed suggesting that virulence factors, such as toxins, produced by B. bassiana may not be inhibited by genes that are already over-expressed in insecticide resistant mosquito populations. This is promising for biological control and suggests that the fungi are viable alternatives to insecticides.

No description available.

No description available.

Thesis (Ph.D.(Virology))--University of the Witwatersrand, Faculty of Health Sciences, 2012 / Morphological similarity between malaria vectors and non-vectors occurring in sympatry has serious consequences if the killer diseases have to be controlled. Malaria in Malawi is transmitted by Anopheles gambiae, An. arabiensis and An. funestus. This vector diversity is further complicated by the recently discovered An. funestus-like species which is morphologically similar to An. funestus, and found in association with humans. Currently there is no single assay available that differentiates An. funestus-like from the other African members in the An. funestus group. The objective of this study was to investigate the biology and behavior of the newly discovered An. funestus-like species and its possible role in malaria transmission. This information will assist in the implementation of vector control programs. In addition to this, the study investigated the development of a DNA based assay to differentiate between the members of the An. funestus group and to morphologically described An. funestus-like species. Anopheles mosquitoes were collected resting indoors and outdoors from Karonga in Malawi. Specimens were identified morphologically and molecularly using chain reaction PCR. Identified samples were analyzed by ELISA for blood meal source and Plasmodium sporozoite infection. Anopheles funestus-like was morphologically compared with An. funestus. Real time based PCR was developed and compared to the current multiplex or allele-specific PCR (AS-PCR) assay for sensitivity and performance. The IGS region of the rDNA gene was investigated for development of AS-PCR. Phylogenetic relationship of mosquitoes was constructed from ITS2 and D3 sequences. Adult An. funestus mosquitoes (n = 391) were collected during April and September, 2010. Karonga contributed 63.9% and Likoma Island 36.1%. Of the identified specimens (n = 347) An. funestus-like comprised 10.4%, An. rivulorum 31.7%, An. funestus 57.3% and An. parensis 0.6%. Most of the An. funestus-like species were collected resting indoors 91.7% (33/36) compared to outdoors 8.3% (3/36). The species was predominant during the dry season 63.9% (23/36) compared to the wet season. A total of 19 An. funestus-like females were analyzed for blood meal source. Mixed blood meal from goat and bovine was found in 7 specimens and a single blood meal from goat in 3 specimens.. The rest of the An. funestus-like was negative for blood meal. An overall dry season infection rate of An. funestus-like species by Plasmodium vivax was 5% (1/20) in this study and 3.1% (2/64) from samples collected in 2009 was found. However, the possibility of false positivity could not be excluded and further study is urgently needed to investigate this. Real-time PCR for the identification of members of the An. funestus group was found to be more sensitive (0.02ng/μl) than AS-PCR (0.04ng/μl) and had performance comparable to AS-PCR. AS-PCR developed from the intergenic spacer region of rDNA discriminates An. funestus, An. rivulorum, An. vaneedeni and An. parensis. Of all assays developed in this study, the hydrolysis probe assay is the most reliable assay for identifying members in the An. funestus group. This study confirmed the existence of An. funestus-like species in sympatry with An. funestus group members. An. funestus-like was predominantly found resting indoors (endophilic) but preferring animal over human blood (zoophilic). No consistent morphological characters were found to discriminate between An. funestus and An. funestus-like based on morphological data, An. funestus-like is very similar and closely related to An. funestus which is supported by phylogenetic analysis. However, Restriction Fragment Length Polymorphism separates the two species.

Abstract Malaria vector control relies principally on the use of insecticides. However, the increasing incidence of insecticide resistance threatens to undermine the effectiveness of this approach, necessitating resistance management strategies. Multiple insecticide resistance is becoming common in West Africa including Ghana. In particular, a population of the major malaria vector Anopheles gambiae, from the Ahafo region of Ghana, shows resistance to all classes of insecticide currently available for use in public health. Insecticide resistance is a primary adaptive characteristic of epidemiological importance although other adaptive traits such as staggered larval time-to-hatch may also be important. Typically, An. gambiae oviposits in small, temporary, sun-lit water bodies and eggs generally hatch 2-3 days post-oviposition. However, staggered distribution of hatching has previously been shown and was also observed in a newly colonized strain (GAH) from Ahafo. The broad aims of this project were therefore to assess and characterize multiple insecticide resistance in An. gambiae from Ahafo as well as to quantify and describe staggered time-to-hatch in a laboratory colony of this population in terms of its adaptive significance and pleiotropic effects on resistance.

Thesis (Ph. D.)--Michigan State University. Dept. of Entomology, 2006. / Title from PDF t.p. (viewed on Nov. 20, 2008) Includes bibliographical references. Also issued in print.

La lutte anti-vectorielle est une composante importante de la lutte contre les maladies à transmission vectorielle. La connaissance des populations vectorielles, tant dans leur composition spécifique que dans leur répartition spatio-temporelle, est fondamentale pour la conception des stratégies de lutte contre ce type de maladie.Cette thèse a modélisé la distribution spatiale des formes moléculaires M et S d’Anopheles gambiae s.s., des vecteurs majeurs du paludisme au Burkina Faso. La modélisation a été faite à partir de l’analyse d’une série d’observations portant à la fois sur les vecteurs et l’environnement. Elle procède d’une combinaison de concepts et méthodes de biogéographie avec des techniques et outils d’analyse spatiale, d’analyse des données et des systèmes d’informations géographiques.Nous retenons de ce travail de recherche que l’abondance de la forme moléculaire S d’Anopheles gambiae s.s., diminue au fur et à mesure que l’on évolue des régions humides du sud et du sud-ouest vers celles les plus arides du nord et du nord-est. Le NDVI, l’ETP, et l’insolation sont les facteurs les plus déterminants de sa distribution spatiale. Par contre, l’abondance de la forme moléculaire M d’Anopheles gambiae s.s. augmente des régions humides du sud et du sud-ouest vers celles plus arides du nord et du nord-est. L’altitude, la pression, l’insolation, la densité de végétation sont les facteurs les plus déterminants de cette répartition spatiale. De ces résultats, ont été dérivés deux modèles qui ont servi à l’élaboration des cartes de distribution des formes moléculaires M et S d’Anopheles gambiae s.s.Enfin, cette thèse révèle le rôle de l’approche géographique dans la réflexion sur les questions de santé et sa méthodologie pourrait être testée sur d’autres sites et pour d’autres vecteurs de maladies. Elle peut s’enrichir d’une analyse multi échelle et d’une modélisation de la variabilité temporelle. / The anti-vectorial fight is an important constituent for vectorial borne diseases control. The knowledge of the vectors populations as well as their specific composition and spatiotemporal distribution is fundamental for the conception of the strategies of fight against this type of disease.This thesis modeled the spatial distribution of the molecular forms M and S of Anopheles gambiae s.s., major vectors of malaria in Burkina Faso. The modeling was made from the analysis of a series of observations concerning both the vectors and the environment.It proceeds of a combination of concepts and methods of biogeography with techniques and tools of spatial analysis, data analysis and the geographical information systems.We retain of this research work that the abundance of the molecular form S of Anopheles gambiae s.s., decreases as we move from wet regions of the south and the southwest to those the driest of the north and the northeast. The NDVI, the ETP, and the sunshine are the most determining factors of its spatial distribution.In contrast, the abundance of the molecular form M of Anopheles gambiae s.s. increases from the wet regions of the South and the southwest to those drier of the north and the northeast. The temperatures, the pressure, the sunshine and the NDVI are the most determining factors of this spatial distribution.Of these results, were diverted two models which we use to elaborate the Maps of distribution of the molecular forms M and S of Anopheles gambiae s.s.This thesis highlights also the role of the geographical approach in the reflection on health issues and its methodology could be tested on the other sites and for the other vectors of diseases. This methodology could be improved by multi-scale analysis and of temporal variability modeling.

MSc (Med), Faculty of Health Sciences, University of the Witwatersrand, 2009 / Malaria is on the increase in Mozambique since 2001 and impacts primarily on children < 5 years of age. Insecticide resistance in the malaria vector mosquitoes is on the increase in Mozambique and Africa and is cause for serious concern. Maragra sugar estate is situated in close proximity to the nKomati river floodplain in a rural area in Mozambique and requires intense irrigation for cane growing and as a result provides extensive breeding sites for An. funestus and other mosquitoes. In the areas surrounding the estate there are two important vectors of malaria, Anopheles funestus group and An. gambiae complex. There is intense malaria transmission in the areas surrounding the sugar estate and the last entomological study on the vectors in the Manhica area was done in 1998. It was becoming increasingly urgent to identify to species level the vectors in this area and to monitor the insecticide resistance status of these vectors. Due to leakage (theft) of insecticides and a change by the National Malaria Control Programme (NMCP) to an insecticide to which the predominant vector is resistant, an entomological survey was carried out in this area from January 2009 to March 2009 to ascertain by Polymerase chain reaction (PCR) what species of malaria vectors were present inside and outside of the Maragra vector control area, their population levels and their vectorial status in these two areas. Insecticide resistance studies by insecticide exposure and the synergist piperonyl butoxide (pbo) were carried out using the World Health Organisation (WHO) bioassay method on collected An. funestus mosquitoes. This was done to establish this species resistance status to the four classes of insecticides recommended by the WHO for malaria vector control. The collections of An. arabiensis and An. merus that were identified were too few to carry out insecticide resistance tests on these two species. Enzyme linked v immuno-sorbent assay (ELISA) tests were undertaken to establish the vectorial capacity of Anopheles funestus and An. gambiae complex in this area. The predominant malaria vector species in this area is An. funestus s.s., with the secondary vector being An. arabiensis. An. funestus has a high vectorial capacity in this area and found to have a Plasmodium falciparum sporozoite rate of 6.02%. This is an increase in the sporozoite rate of 1.2% from 1998 when the last survey in this regard was carried out. Coupled with this increase is an increase in the An. funestus populations in this area since this time. One An. gambiae complex sample was found to be positive but the species is not known as this particular sample did not amplify on PCR. Anopheles funestus is highly resistant to synthetic pyrethroids and exhibits a lower level of resistance to bendiocarb, a carbamate insecticide in use at Maragra sugar estate. The synergist pbo mediates the resistance mechanism in both these insecticides indicating that the metabolic resistance mechanism present in this mosquito is strongly mediated by monooxygenase detoxification. The role of the medical entomologist is increasingly necessary and important in the monitoring of this resistance phenomenon in malaria vector mosquitoes, as is the role of the vector control programme manager in implementing and managing vector control programmes. The implication of cane sugar farming and its impact on vector production and malaria transmission is discussed. Insecticide resistance and the change by the NMCP to a synthetic pyrethroid to which the predominant vector of malaria is resistant is discussed.

Thesis (M.Sc. (Environmental Biology))--Mahidol University, 1986.

Heidelberg, Univ., Diss., 2007.