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Environmental risk factors for malaria : a matched case-control study in Piura, PeruGuthmann, Jean-Paul January 2000 (has links)
No description available.
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Impact of changed feeding behaviour of An. funestus on malaria transmission in southern TanzaniaAzizi, Salum January 2012 (has links)
A research report submitted to the Faculty of Health Sciences, University of the
Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the
degree of Master of Science in Biology and Control of African Disease
Vectors.
Johannesburg, February 2012 / In Tanzania both Anopheles funestus and An. gambiae s.l. play a role as major vectors of malaria. Different species exist in the An. funestus group and the An. gambiae complex and play different roles in disease transmission. For malaria vector control programmes knowledge of vector species and their behaviour is key. A recent report on increased exophagy of An. funestus in southern rural Tanzania as a response to increased use of insecticide treated bed nets raised the question of whether there was misidentification of species and/or behavioural insecticide resistance playing a part. The present study used molecular tools to identify the species and determine human biting rates indoors and outdoors along with development and field evaluation of a new tool for sampling malaria vectors which is more effective than human landing catches.
The results showed that the majority (96.2%) of the An. funestus group that were collected were An. funestus s.s. by PCR assay. Also, the exophagic proportion (45.9%) of An. funestus was lower than the endophagic proportion (54.1%), similar to other places in Africa, although in this study the difference was insignificant when untreated bed nets and treated bed nets were used. In addition, there was significant outdoor biting activity early in the evening that could lead to the malaria transmission cycle being unaffected by ITNs. The new trap, “Sticky Bucket Trap”, caught considerably fewer mosquitoes (14.2%) than that caught by human landing catches (85.8%), with statistical significance of P>0.05. These results imply that the sticky bucket trap is not a suitable substitute for human landing catches and some modifications are needed to make it more effective. Whereas indoor and outdoor
proportions insignificant difference in feeding preference imply that both indoor and outdoor interventions should be used to control this vector.
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Fitness assessments of Anopheles arabienesis laboratory colonies from Southern Africa and their suitability for the sterile insect techniqueEssop, Leyya 13 April 2015 (has links)
In order to employ the Sterile Insect Technique (SIT), biologically fit mosquitoes able to compete with their wild counterparts, suitable field sites for mass release of sterilized male mosquitoes, and appropriate methods of rearing genetic sex-separation (GSS) mosquito strains are required. The life history traits and biological fitness of four laboratory-reared, southern African Anopheles arabiensis strains were investigated. Despite being colonized at different times, the four strains demonstrated comparable levels of biological fitness. Three sites in the Kruger National Park were assessed as possible SIT field sites. Mosquito collections were conducted at each site during three summer months. Anopheles arabiensis was predominant at Malahlapanga during each collection period, establishing Malahlapanga as the most appropriate site for SIT field trials. A standard larval diet was shown to be appropriate for rearing An. arabiensis GSS. This work formed the laboratory basis for the evaluation of a SIT strategy for South Africa.
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Influence of environmental characteristics on the habitat of and behavioural interactions between anopheles species in South AfricaDavies, Craig January 2016 (has links)
A dissertation submitted to the Faculty of Health Sciences, University of the Witwatersrand,
South Africa in fulfilment of the requirements for the degree of Master of Science.
2016 / This project explored the ecological conditions of aquatic breeding sites of Anopheles
gambiae sensu lato immatures in the Lowveld region of eastern Mpumalanga Province,
South Africa. The aim was to determine the environmental conditions influencing anopheline
abundance as well as abiotic parameters which associated with vector productivity. In
addition to this, the levels of insecticide resistance to the three dominant compounds used in
vector control in the region were assessed. Taking into account the sympatric occurrence of
the major malaria vector in South Africa (An. arabiensis Patton) and its sibling, non-vector
species (An. quadriannulatus Theobald), a laboratory study was devised which investigated
the outcome of intra- and inter-specific competition under constant and fluctuating
temperature regimes.
There was a heterogenous distribution of anophelines across aquatic habitats in Mpumalanga
with small-scale variation in salinity and Total Dissolved Solids (TDS) influencing species
composition and Anopheles arabiensis was found in all sites surveyed with low numbers
occurring where salinity levels were elevated. Anopheles merus associated with high salinity
and TDS (Pearson’s Product Moment, r = 0.922, p < 0.05) whilst An. quadriannulatus
dominated in breeding sites within 50m of a building or road. Anopheles gambiae complex
members were susceptible to the insecticides tested with possible resistance (97%) to DDT in
An. merus.
Under laboratory conditions, temperature and competitive scenarios affected the life-history
traits of both species studied here. The treatment 18 - 35°C generally reduced survivorship
except for An. arabiensis in mixed, larval species treatments where it was similar to values
reported for 25°C. Survivorship of both species at 20 - 30°C was not significantly impacted
and the adult production was high across species treatments. The development rates at 25°C
and 20 - 30°C were significantly different between species when reared alone and in mixed
species treatments from larvae and from eggs. The effect of temperature was more
pronounced at 18 - 35°C with An. arabiensis developing faster under both competitive
scenarios and An. quadriannulatus slower, notably when in the presence of its competitor (p
< 0.05).
In the field component of this study, Anopheles arabiensis exploited all the habitats surveyed.
It is therefore recommended that larval control operations should include all available
breeding sites, focusing efforts during the dry season when these sites are limited and
discreet within the landscape. In the laboratory component, it was possible to test whether or
not community composition of anophelines at the adult stage was regulated by different
temperature and competitive conditions at the larval stage to better understand the ecological
conditions that determine anopheline composition and relative abundance. Taken together,
the results of each component emphasize the need for local scale studies, especially under
conditions of changing temperatures and rainfall patterns. The results of responses to
temperatures and biotic interactions are necessary data for use in models predicting the
impact of climate change on malaria vector mosquitoes. / MT2016
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Culicídeos associados às bromélias na Mata Atlântica do município de Cananéia, São Paulo, Brasil / Bromeliad associated mosquitoes from Atlantic Forest, in Cananéia, São Paulo, BrasilMarques, Tatiani Cristina 21 September 2010 (has links)
Introdução: A Mata Atlântica não possui fisionomia uniforme, pois seu relevo determina diferentes condições ambientais que definem a composição de sua fauna e flora. Em uma mesma região, a diversidade de espécies pode variar de acordo com a heterogeneidade dos habitats. Objetivo: Caracterizar a fauna de Culicidae em fitotelmatas de bromélias (Bromeliaceae), no município de Cananéia, São Paulo, Brasil. Métodos: Larvas e pupas de culicídeos foram obtidas, mensalmente, do conteúdo aquático de bromélias de três ambientes: planície, encosta e morro. As coletas ocorreram entre julho de 2008 e junho de 2009. Para estimar a variedade de espécies foram utilizados os índices de Margalef e de Menhinick. O índice de Jaccard e o de Sorensen indicaram a semelhança entre bromélias de dois ambientes. Para avaliar a dominância, empregou-se o índice de Simpson e de Berger-Parker. A eqüidade na distribuição das espécies foi avaliada pelo índice de Pielou e a constância em cada ambiente pelo índice c. Os testes estatísticos empregados foram: análise de variância (ANOVA) com o teste de Fisher; teste Kruskal-Wallis e valor p; teste de associação qui-quadrado e regressão linear simples por meio do coeficiente de correlação de Pearson. Resultados: O teste Kruskal-Wallis mostrou diferenças significantes para o volume hídrico das bromélias de cada ambiente (p=0,002, IC= 95 por cento) mas não para o valor do pH (p= 0,775). Foram identificados 2024 mosquitos, 786 (38,83 por cento) na planície, 606 (29,94 por cento) na encosta e 632 (31,23 por cento) no morro, dentre eles: Culex (Microculex) (62,25 por cento), Culex ocellatus (21,20 por cento), Anopheles (Kerteszia) (15,17 por cento), Wyemoyia (Phoniomyia) (1,33 por cento) e Runchomyia (Runchomyia) (0,05 por cento). O índice de riqueza de Margalef foi maior na planície (d1=2,55) e menor no morro (d1=1,86), e o de Sorensen indicou encosta e morro como os ambientes mais similares (QS=0,79) e planície e morro como os menos similares (QS=0,65). O teste 2 não mostrou associação entre os ambientes e o tipo de bromélia (p=0,060). O coeficiente de Pearson não mostrou correlação significativa entre o número de imaturos e a temperatura (p=0,111) ou precipitação acumulada (p=0,828). Conclusões: Planície apresentou os maiores índices de diversidade. A prevalência de An. homunculus foi maior do que a encontrada em estudos anteriores. Culex ocellatus, Cx. (Mcx.) retrosus, Cx. (Mcx.) neglectus, Cx.(Mcx.) imitator e An. (Ker.) homunculus foram as espécies mais dominantes quando os três ambientes foram analisados conjuntamente / Introduction: Atlantic Forest is not uniform and its relief determines different environmental conditions that define the composition of its fauna and flora. Thus, in the same region, species diversity may vary according to habitat heterogeneity. Objective: To assess mosquito (Culicidae) fauna in bromeliads phytotelmate (Bromeliaceae), in Cananéia, São Paulo, Brazil. Methods: The larvae and pupae of mosquitoes were collected monthly in the water content of bromeliads from three regions: the lowland, hillside and hilltop. Sampling occurred between July 2008 and June 2009. To estimate richness, Margalef and Menhinick indices were used. Jaccard and Sorensen indices indicated the similarity between bromeliads from two regions. To assess dominance, we employed Simpson and Berger-Parker indices. Equity in the distribution of species was assessed by Pielou index and c index evaluated species constancy in each region. Statistical analyses applied were: ANOVA with Fisher\'s exact test, Kruskal-Wallis test and p value; Chi-square association test and linear regression using Pearson correlation coefficient. Results: Kruskal-Wallis test showed significant differences in water volume for bromeliads from each region (p=0,002, CI=95 per cent) but not for the pH value (p=0,775). In all, 2024 mosquitoes were identified, 786 (38,83 per cent) in the lowland, 606 (29,94 per cent) on the hillside and 632 (31,23 per cent) on the hilltop, among them: Culex (Microculex) (62,25 per cent), Culex ocellatus (21,20 per cent), Anopheles (Kerteszia) (15,17 per cent), Wyemoyia (Phoniomyia) (1,33 per cent) and Runchomyia (Runchomyia) (0,05 per cent). Margalef richness index was higher in the lowland (d1=2,55) and lower on the hilltop (d1=1,86). According to the Sorensen similarity index, species from the hillside are more likely to be found on the hilltop (QS=0,79) than in the lowland (QS=0,73). The greatest differences occurred between the hilltop and the lowland (QS=0,65). The 2 test showed no association between the regions and the type of bromeliad (p=0.060). Pearson coefficient showed no significant correlation between the number of immatures and temperature (p=0,111) or rainfall (p=0,828). Conclusions: Lowland region had the highest diversity index. The prevalence of Anopheles homunculus was higher than that found in previous studies. Culex ocellatus, Cx. (Mcx.) retrosus, Cx. (Mcx.) neglectus, Cx. (Mcx.) imitator and An. (Ker.) homunculus were the most dominant species when the three regions were analyzed together
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Analysis of anopheline mosquito behavior and identification of vector control targets in the post-genomic eraJenkins, Adam January 2015 (has links)
Thesis advisor: Marc A.T. Muskavitch / The protozoan Plasmodium falciparum, the mosquito-borne pathogen that causes human malaria, remains one of the most difficult infectious parasites to combat and control. Campaigns against malaria eradication have succeeded, in most instances, at the level of vector control, rather than from initiatives that have attempted to decrease malaria burden by targeting parasites. The rapid evolution and spread of insecticide-resistant mosquitoes is threatening our ability to combat vectors and control malaria. Therefore, the development, procurement and distribution of new methods of vector control are paramount. Two aspects of vector biology that can be exploited toward these ends are vector behaviors and vector-specific insecticide targets. In this thesis, I describe three aspects of vector biology with potential for the development of improved means of vector control: photopreference behavior, long non-coding RNA (lncRNA) targets and epigenetic gene ensemble targets. My studies of photopreference have revealed that specific mosquito species within the genus Anopheles, An. gambiae and An. stephensi, exhibit different photopreference behaviors, and that each gender of mosquito in these species exhibits distinct light-dependent resting behaviors. These inter-specific behavioral differences may be affected by differing numbers of long-wavelength sensing Opsin genes in each species, and my findings regarding species-specific photopreferences suggest that some behavioral interventions may need to be tailored for specific vector mosquito species. Based on the advancement of next-generation sequencing technologies and the generation by others of assembled genomes of many anopheline mosquito species, I have identified a comprehensive set of approximately 3,000 lncRNAs and find that RNA secondary structures are notably conserved within the gambiae species complex. As lncRNAs and epigenetic modifiers cooperate to modulate epigenetic regulation, I have also analyzed the conservation of epigenetic gene ensembles across a number of anopheline species, based on identification of homologous epigenetic ensemble genes in An. gambiae compared to Drosophila melanogaster. Further analyses of these ensembles illustrate that these epigenetic genes are highly stable among many anopheline species, in that I detect only eight gene family expansion or contraction events among 169 epigenetic ensemble genes within a set of 12 anopheline species. My hope is that my findings will enable deeper investigations of many behavioral and epigenetic processes in Anopheles gambiae and other anopheline vector mosquitoes and thereby enable the development of new, more effective means of vector and malaria control. / Thesis (PhD) — Boston College, 2015. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Biology.
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Mapeamento físico de genes expressos de resposta imune e sensorial de Anopheles (Nyssorhynchus) Darlingi, vetor da malária neotropicalBridi, Letícia Cegatti 23 August 2016 (has links)
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Previous issue date: 2016-08-23 / Fundação de Amparo à Pesquisa do Estado do Amazonas - FAPEAM / Malaria in Brazil occurs especially in the Amazon (99% of cases), where
environmental conditions are favorable for the proliferation of the etiologic and their
mosquito vectors agents, whose main transmitter is the Anopheles darlingi.
Environmental factors and human activities are some of the main aspects that
contribute to the adaptive and evolutionary process that anopheles, which can be
reflected in chromosomal rearrangements. We carried out the physical chromosome
mapping by fluorescence in situ hybridization (FISH) of inume response genes in the
genome of A. darlingi, GNBP (Gran-negative binding protein), Toll-interacting protein
(Toll), defensin, Chymotrypsin-like serine protease (AdChyL), 28S ribosomal protein
S7- mitochondrial precursor (RpS7), gambicin anti-microbial peptide (gambicin) and
also the gene sensory response: OBP (odorant binding protein) to assist in more
precise assembly of its structural genomics. These genes have been mapped in
single chromosomal regions, with the exception of RpS7, which mapped in more than
one location. Other genes have been mapped in inversion regions: GNBP (inversion
2 Rd); AdChyL in the region 38D (inversion 3Lb) and RpS7 in 22C region (inversion
2Lb). The OBP gene mapped the X chromosome from five locations individuals,
where only A. darlingi of São Gabriel da Cachoeira/AM (SGC/AM) OBP gene marked
the region 3A compared to four locations Coari/AM, Manaus/AM, Barra do
Bugres/MT and Macapá/AP, where the probe mapped the region 4A. Two new
investments were described for A. darlingi and one on chromosome X (Xb) in the
population of SGC/AM and another in the arm 2L (2LC), population Bugres/MT.
Geographical distances and ecoregions (geographical barriers) are environmental
factors that can favor the appearance of the two new inversions described in this
work. In the phylogenetic analysis of GNBP genes Toll, defensin, RpS7 and
gambicin, we obtained three clades for GNBP and most of the analyzed sequence
was homologous to the subfamily B, including GNBP Anopheles gambiae (87%),
suggesting that GNBP A . darlingi belongs to the subfamily B. Phylogenetic trees for
RpS7 genes, gambicin, defensin and Toll showed a high degree of conservation
between these genes in A. gambiae and Anopheles arabiensis. Immune response
genes of A. darlingi and Anopheles albimanus are phylogenetically close but not
always a reliable support. This may suggest some level of evolutionary conservation
of the genes of the immune response of both species. The genes mapped in situ
were considered cytogenetic useful markers for chromosomal variability studies and
developments in A. darlingi as they are conserved genes, and assist in the
improvement of sequence analyzes not finalized the assembly and annotation of the
genome of A. darlingi. / A malária no Brasil ocorre especialmente na Amazônia (99% dos casos), onde as
condições ambientais são favoráveis para a proliferação dos agentes etiológicos e
de seus mosquitos vetores, cujo principal transmissor é o Anopheles darlingi.
Fatores ambientais e atividades antrópicas são alguns dos principais aspectos que
contribuem para o processo adaptativo e evolutivo desse anofelino, o que pode ser
refletido em rearranjos cromossômicos. Neste trabalho, realizamos o mapeamento
físico cromossômico por hibridização in situ fluorescente (FISH) dos genes de
resposta inume do genoma de A. darlingi, GNBP (Gran-negative binding protein),
Toll-interacting protein (Toll), defensina, Chymotrypsin-like serine protease (AdChyL),
28S ribosomal protein S7- mitochondrial precursor (RpS7), gambicin anti-microbial
peptide (gambicina) e ainda, o gene de resposta sensorial: OBP (odorant
binding protein), para auxiliar na montagem mais precisa do seu genoma estrutural.
Esses genes foram mapeados em regiões cromossômicas únicas, com exceção do
RpS7 que mapeou em mais de um local. Outros genes foram mapeados em regiões
de inversão: GNBP (inversão 2Rd); AdChyL, na região 38D (inversão 3Lb) e RpS7,
na região 22C (inversão 2Lb). O gene OBP mapeou o cromossomo X de indivíduos
de cinco localidades, onde apenas A. darlingi de São Gabriel da Cachoeira/AM
(SGC/AM) o gene OBP marcou na região 3A em comparação com as quatro
localidades Coari/AM, Manaus/AM, Barra do Bugres/MT e Macapá/AP, onde a
sonda mapeou a região 4A. Duas novas inversões foram descritas, para A. darlingi
sendo uma no cromossomo X (Xb) na população de SGC/AM e outra no braço 2L
(2Lc), população de Barra do Bugres/MT. Distâncias geográficas e ecoregiões
(barreiras geográficas) são fatores ambientais que podem favorecer o aparecimento
das duas novas inversões descritas nesse trabalho. Na análise filogenética dos
genes GNBP, Toll, defensina, RpS7 e gambicina, obtivemos três clados para GNBP
e a maioria das sequências analisadas foi homóloga com a da subfamília B,
incluindo GNBP de Anopheles gambiae (87%), sugerindo, que GNBP de A. darlingi
pertence à subfamília B. As árvores filogenéticas para os genes RpS7, gambicina,
defensina e Toll mostraram um alto grau de conservação entre esses genes em A.
gambiae e Anopheles arabiensis. Os genes de resposta imune de A. darlingi e
Anopheles albimanus são filogeneticamente próximos, mas nem sempre com um
suporte confiável. Isso pode sugerir algum nível de conservação evolutiva entre os
genes de resposta imune de ambas as espécies. Os genes mapeados in situ foram
considerados marcadores citogenéticos úteis aos estudos de variabilidade
cromossômica e evolução em A. darlingi já que são genes conservados, além de
auxiliar no aprimoramento das análises de sequências não finalizadas na montagem
e anotação do genoma de A. darlingi.
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Culicídeos associados às bromélias na Mata Atlântica do município de Cananéia, São Paulo, Brasil / Bromeliad associated mosquitoes from Atlantic Forest, in Cananéia, São Paulo, BrasilTatiani Cristina Marques 21 September 2010 (has links)
Introdução: A Mata Atlântica não possui fisionomia uniforme, pois seu relevo determina diferentes condições ambientais que definem a composição de sua fauna e flora. Em uma mesma região, a diversidade de espécies pode variar de acordo com a heterogeneidade dos habitats. Objetivo: Caracterizar a fauna de Culicidae em fitotelmatas de bromélias (Bromeliaceae), no município de Cananéia, São Paulo, Brasil. Métodos: Larvas e pupas de culicídeos foram obtidas, mensalmente, do conteúdo aquático de bromélias de três ambientes: planície, encosta e morro. As coletas ocorreram entre julho de 2008 e junho de 2009. Para estimar a variedade de espécies foram utilizados os índices de Margalef e de Menhinick. O índice de Jaccard e o de Sorensen indicaram a semelhança entre bromélias de dois ambientes. Para avaliar a dominância, empregou-se o índice de Simpson e de Berger-Parker. A eqüidade na distribuição das espécies foi avaliada pelo índice de Pielou e a constância em cada ambiente pelo índice c. Os testes estatísticos empregados foram: análise de variância (ANOVA) com o teste de Fisher; teste Kruskal-Wallis e valor p; teste de associação qui-quadrado e regressão linear simples por meio do coeficiente de correlação de Pearson. Resultados: O teste Kruskal-Wallis mostrou diferenças significantes para o volume hídrico das bromélias de cada ambiente (p=0,002, IC= 95 por cento) mas não para o valor do pH (p= 0,775). Foram identificados 2024 mosquitos, 786 (38,83 por cento) na planície, 606 (29,94 por cento) na encosta e 632 (31,23 por cento) no morro, dentre eles: Culex (Microculex) (62,25 por cento), Culex ocellatus (21,20 por cento), Anopheles (Kerteszia) (15,17 por cento), Wyemoyia (Phoniomyia) (1,33 por cento) e Runchomyia (Runchomyia) (0,05 por cento). O índice de riqueza de Margalef foi maior na planície (d1=2,55) e menor no morro (d1=1,86), e o de Sorensen indicou encosta e morro como os ambientes mais similares (QS=0,79) e planície e morro como os menos similares (QS=0,65). O teste 2 não mostrou associação entre os ambientes e o tipo de bromélia (p=0,060). O coeficiente de Pearson não mostrou correlação significativa entre o número de imaturos e a temperatura (p=0,111) ou precipitação acumulada (p=0,828). Conclusões: Planície apresentou os maiores índices de diversidade. A prevalência de An. homunculus foi maior do que a encontrada em estudos anteriores. Culex ocellatus, Cx. (Mcx.) retrosus, Cx. (Mcx.) neglectus, Cx.(Mcx.) imitator e An. (Ker.) homunculus foram as espécies mais dominantes quando os três ambientes foram analisados conjuntamente / Introduction: Atlantic Forest is not uniform and its relief determines different environmental conditions that define the composition of its fauna and flora. Thus, in the same region, species diversity may vary according to habitat heterogeneity. Objective: To assess mosquito (Culicidae) fauna in bromeliads phytotelmate (Bromeliaceae), in Cananéia, São Paulo, Brazil. Methods: The larvae and pupae of mosquitoes were collected monthly in the water content of bromeliads from three regions: the lowland, hillside and hilltop. Sampling occurred between July 2008 and June 2009. To estimate richness, Margalef and Menhinick indices were used. Jaccard and Sorensen indices indicated the similarity between bromeliads from two regions. To assess dominance, we employed Simpson and Berger-Parker indices. Equity in the distribution of species was assessed by Pielou index and c index evaluated species constancy in each region. Statistical analyses applied were: ANOVA with Fisher\'s exact test, Kruskal-Wallis test and p value; Chi-square association test and linear regression using Pearson correlation coefficient. Results: Kruskal-Wallis test showed significant differences in water volume for bromeliads from each region (p=0,002, CI=95 per cent) but not for the pH value (p=0,775). In all, 2024 mosquitoes were identified, 786 (38,83 per cent) in the lowland, 606 (29,94 per cent) on the hillside and 632 (31,23 per cent) on the hilltop, among them: Culex (Microculex) (62,25 per cent), Culex ocellatus (21,20 per cent), Anopheles (Kerteszia) (15,17 per cent), Wyemoyia (Phoniomyia) (1,33 per cent) and Runchomyia (Runchomyia) (0,05 per cent). Margalef richness index was higher in the lowland (d1=2,55) and lower on the hilltop (d1=1,86). According to the Sorensen similarity index, species from the hillside are more likely to be found on the hilltop (QS=0,79) than in the lowland (QS=0,73). The greatest differences occurred between the hilltop and the lowland (QS=0,65). The 2 test showed no association between the regions and the type of bromeliad (p=0.060). Pearson coefficient showed no significant correlation between the number of immatures and temperature (p=0,111) or rainfall (p=0,828). Conclusions: Lowland region had the highest diversity index. The prevalence of Anopheles homunculus was higher than that found in previous studies. Culex ocellatus, Cx. (Mcx.) retrosus, Cx. (Mcx.) neglectus, Cx. (Mcx.) imitator and An. (Ker.) homunculus were the most dominant species when the three regions were analyzed together
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Investigation of the efficacy of some insect growth requlators on anopheles (Cellia) Balabacensis. (Diptera : Culicidae) /De las Llagas, Lilian A. January 1978 (has links) (PDF)
Thesis (M.Sc. (Tropical Medicine))--Mahidol University, 1978.
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Toll signaling immune function and evolution in Anopheline mosquitoesRhodes, Victoria L. M. January 1900 (has links)
Doctor of Philosophy / Department of Biology / Kristin Michel / Malaria remains a major human vector-borne disease, greatly contributing to global human morbidity and mortality. Control of mosquito vectors that transmit malaria continues to be dependent on the widespread application of chemical insecticides through indoor residual spraying and insecticide treated bed nets. However, resistance to these insecticides is spreading within many mosquito populations, adding an ever-increasing urgency to the development of alternative vector control measures. The mosquito immune system is a potential novel target for such alternative measures, as the immune response initiated in these insects during infection with vector-borne disease agents is a key determinant of vector competence and, thus, contributes to a species’ vectorial capacity. These immune responses, additionally, interact with and respond to parasitic or symbiotic biocontrol agents employed to kill or manipulate infection outcome with vector-borne disease agents. Entomopathogenic fungi, including Beauveria bassiana, have been considered as an alternative vector control measure, functioning as biopesticides. The Toll pathway is a key antifungal immune pathway in insects that impacts an insect’s ability to survive fungal infections. A better understanding of Toll signaling immune function and evolution in anophelines, both vector and nonvector, can thus help to improve future biocontrol methods of important vector mosquitoes like Anopheles gambiae. In this dissertation, I report the use of B. bassiana strain I93-825 in An. gambiae to analyze the impact of Toll pathway modulation on mosquito survival. Mosquito survivorship was strongly affected by B. bassiana exposure dose by several measured parameters including median survival, longevity, and hazard. Modulation of Toll signaling, by way of knockdown by RNA interference, revealed a dose-dependent trade-off between immune activation state and survivorship in An. gambiae. To better determine the full Toll immune signaling repertoire in mosquitoes, I annotated and describe the evolutionary history of intracellular Toll pathway members and Toll-like receptors (TLRs) within 21 mosquito genomes. The intracellular signaling pathway is conserved with 1:1 orthology, and evolutionary rates across different intracellular pathway members vary widely as compared to the conserved protein core of these mosquito species. In contrast, TLRs evolved largely by duplication events within certain anopheline lineages, most dramatically in the An. gambiae complex, where six TOLL1/5 paralogs likely possess different ligand binding specificities. Thus, these TLRs should be prioritized for experimental analyses of TLR immune function in An. gambiae.
Taken together, the work in this dissertation identifies Toll pathway modulation as a potential resistance mechanism that could impact malaria biocontrol strategies and provides a foundation for future detailed studies of Toll pathway function in important mosquito vector species.
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