Browsing by Author "Mukwaya, L. G."

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    Feeding preference by the male blowfly Phormia regina for some natural foods and its relation to carbohydrate, amino acid, and alcohol content
    (Entomologia experimentalis et applicata, 1986) Mukwaya, L. G.
    The male blowfly, Phormia regina Meigen shows preference among a variety of natural and artificial foods. In a laboratory study preference was observed among sweet and fermenting juices as well as between liver and fish. The preferences between fresh and fermenting juices were based not only on component sugars, but also on other components, namely, amino acids, alcohol salts and presumably other chemical compounds. The preference between decaying liver and fish was probably based partly on the composition and concentration of amino acids in these foods. A variety of amino acids were found in foods and some of these amino acids were shown to be excitatory, some inhibitory and others neutral. Salts were also observed to be present in the juices; and in a laboratory study NaCl at lower concentrations acted synergestically with 0.1 M sucrose and at higher concentrations repulsive. It is suggested that feeding preference is based on several chemicals which behave either in an excitatory, additive, neutral, inhibitory or synergistic manner. The ratio of excitants to inhibitants is important in deciding the direction of preference. Résumé Relation entre les teneurs en glucides, acides aminés et en alcool et les préférences alimentaires de Phormia regina P. regina Meigen mâle préfère certains aliments naturels ou artificiels. Au laboratoire ses préférences parmi les jus sucrés sont les suivantes: orange > miel > pomme > sucrose 0.1 M; et parmi les aliments en décomposition: sucrose 0.1 M > foie > poisson. Les jus frais sont préférés aux jus fermentés. Les préférences ne dépendent pas seulement de la nature des sucres, mais aussi des acides aminés, de l'alcool, des sels et probablement d'autres substances chimiques. Le foie contient à la fois le plus grand nombre et la concentration la plus élevée en acides aminés, ce qui explique partiellement le goût pour le foie. Expérimentalement on peut classer les acides aminés en stimulants, inhibiteurs et neutres. Des sels ont été notés dans les jus, mais aucune analyse qualitative et quantitative n'en a été faite. Mélangé à du sucrose à 0.1 M, NaCl agit en synergie aux faibles concentrations, devient neutre à 0.175 M et à des concentrations supérieures le sucrose seul est préféré au mélange avec NaCl. Cependant, un mélange de NaCl à 0.25 M (bien qu'une telle concentration soit peu probable dans des jus végétaux) avec du sucrose à 0.1 M était préféré à l'eau. Il en est déduit que les préférences alimentaires dans la nature sont orientées par plusieurs substances chimiques qui se comportent d'une façon stimulante, additive, neutre, inhibitrice ou synergique, et que les préférences alimentaires sont relatives. Le rapport de stimulants sur inhibiteurs est important dans la détermination du sens de la préférence.
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    Genetic control of feeding preferences in the mosquitoes Aedes (Stegomyia) simpsoni and aegypti
    (Physiological Entomology, 1997) Mukwaya, L. G.
    The biting rate of a non‐anthropophilic (Bwayise) population of Aedes simpsoni was found to be approximately 0.3 mosquitoes per catcher per hour, whereas that of an anthropophilic (Bwamba) population was approximately 101 per catcher per hour. Population density indices, as determined by the number of pupae per wet plant axil, were 0.70 in Bwayise and 1.00 in Bwamba. The big difference in anthropophilic behaviour between these populations was therefore unlikely to be derived from this small population difference. Larval density was higher at Bwamba than at Bwayise, but isolation or crowding of the larvae in the laboratory did not affect the biting behaviour of adult Ae. simpsoni. Laboratory studies also failed to confirm field observations that temperature might play a part in determining anthropophily and non‐anthropophily in this species. In choice‐chamber landing tests, using a rat and a human hand, Ae. simpsoni females derived from wild larvae and reared in the laboratory showed that 83% of the Bwamba strain landed on man, whereas only 38% of the Bwayise strain did so. In Aedes aegypti, 71% of a long‐established laboratory strain (Ilobi) landed on man, whereas 47% of a relatively non‐anthropophilic wild (Kampala) strain did so. These preferences persisted in culture. Selective breeding increased the preference for the rodent significantly in the Kampala strain of Ae. aegypti, but had no significant effect on the Ilobi strain. Crossbreeding showed that the F1 and F2 hybrids between the anthropophilic and non‐anthropophilic strains were intermediate in their preference between the parental pure bred strains; the reciprocal crosses were not significantly different from each other. The behaviour of the backcross progenies, at least in Ae. aegypti, appeared to indicate that the genotype of the male parent might be the main determining factor.
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    Genetic differentiation in the yellow fever virus vector, Aedes simpsoni complex, in Africa: Sequence variation in the ribosomal DNA internal transcribed spacers of anthropophilic and non-anthropophilic populations
    (Insect Molecular Biology, 2000) Mukwaya, L. G.; Kayondo, J. K.; Crabtree, M. B.; Savage, H. M.; Biggerstaff, B. J.; Miller, B. R.
    Mosquitoes of the Aedes simpsoni complex are important vectors of yellow fever virus in Africa. We examined the ribosomal DNA sequence divergence in the internal transcribed spacer regions (ITS‐1 and ITS‐2) for populations of mosquitoes that were determined to be anthropophilic or non‐anthropophilic in their bloodmeal host preference. A neighbour‐joining tree produced two clades: one contained all of the individual mosquitoes from anthropophilic populations and the other contained all of the individual mosquitoes from non‐anthropophilic populations. There was no segregation of the taxa within each of the two clades based on geographical origin. The data suggest the exisf′tence of two distinct species of Ae. simpsoni s.l. in Uganda that correlates with their host blood‐feeding preference. The current taxonomic status of the complex is discussed in relation to these findings.
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    The role of olfaction in host preference by Aedes (Stegomyia) simpsoni and Ae.aegypti
    (Physiological Entomology, 1976) Mukwaya, L. G.
    Host preference in females of the mosquitoes Aedes simpsoni (Theo.) and Aedes aegypti (L) appears to be based largely on responses to specific odours at short range, with the site of olfaction being the antennae. In blank Y‐olfactometer tests, 48 % of an anthropophilic (llobi) strain of Ae. aegypti responded to one arm and 52% to the other. However, presented with a man's hand in one arm of the olfacto‐meter and a whole rat, Arvicanthis niloticus, in the other, 65% responded to man and 35% to the rat. With the same strain in a blank Gouck's type of olfactometer, the response was very poor, only 1 % of the mosquitoes in the olfactometer responded at all, again with no preference for either side. On the introduction of the same hosts into the Gouck's olfactometer, the total response was c. 31 %, of which 72 % responded to man and 28 % to the rat. Elimination of some visual cues affected neither the total response nor the preference. Removing one antenna, reduced the preference for man from about 70 % in the normal mosquitoes to about 58%. The total response remained approximately the same as in the normal mosquitoes. Removing both antennae, in both Ae. aegypti and Ae. simpsoni, caused a sharp depression in the total response and in host discrimination.
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    Variation in morphological characters of adults of the Aedes (Stegomyia) simpsoni complex from Uganda, Kenya, and South Africa (Diptera: Culicidae)
    (Mosquito Systematics, 1994) Lutwama, Julius J.; Mukwaya, L. G.
    Examination of adult Aedes simpsoni (Theobald) s.Z. from locations in Uganda and Kenya showed more variation than reported previously. Four patterns of white banding on the midtarsomeres were identified, and they occurred in varying frequencies in samples from different locations. The length of the tarsal bands was distributed continuously within samples from different locations and was variable among progeny of single mothers. This character therefore is not diagnostic of species in the complex. Midtarsomeres 1 and 2 have longer white bands in the majority of males and females of anthropophilic populations in Kenya and Uganda, but there is considerable overlap between the anthropophilic and nonanthropophilic biotypes. A few females in some samples did not bear a tooth on all claws of the fore- or midlegs. Twelve patterns of scutal lines occurred in varying frequencies in samples from different locations. A scutal pattern with long inner lines and short outer lines was most common, with an average occurrence of 5 1.2% in females and 32.2% in males. An H-pattern of scutal lines was more frequent in males (42.1%) than in females (12.10/o), indicating a sex association. Three tergal banding patterns were defined. We conclude that the nominotypical Ae. simpsoni in southern Africa is a distinct species different from the more widespread Ae. Zilii (Theobald) in tropical Africa. Aedes bromeliae (Theobald) cannot be distinguished from the latter based on characters presently described as diagnostic.
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    Widespread Pyrethroid and DDT Resistance in the Major Malaria Vector Anopheles funestus in East Africa Is Driven by Metabolic Resistance Mechanisms
    (PloS one, 2014) Mulamba, Charles; Riveron, Jacob M.; Ibrahim, Sulaiman S.; Irving, Helen; Barnes, Kayla G.; Mukwaya, L. G.; Birungi, Josephine; Wondji, Charles S.
    Establishing the extent, geographical distribution and mechanisms of insecticide resistance in malaria vectors is a prerequisite for resistance management. Here, we report a widespread distribution of insecticide resistance in the major malaria vector An. funestus across Uganda and western Kenya under the control of metabolic resistance mechanisms. Methodology/Principal Findings Female An. funestus collected throughout Uganda and western Kenya exhibited a Plasmodium infection rate between 4.2 to 10.4%. Widespread resistance against both type I (permethrin) and II (deltamethrin) pyrethroids and DDT was observed across Uganda and western Kenya. All populations remain highly susceptible to carbamate, organophosphate and dieldrin insecticides. Knockdown resistance plays no role in the pyrethroid and DDT resistance as no kdr mutation associated with resistance was detected despite the presence of a F1021C replacement. Additionally, no signature of selection was observed on the sodium channel gene. Synergist assays and qRT-PCR indicated that metabolic resistance plays a major role notably through elevated expression of cytochrome P450s. DDT resistance mechanisms differ from West Africa as the L119F-GSTe2 mutation only explains a small proportion of the genetic variance to DDT resistance. Conclusion The extensive distribution of pyrethroid and DDT resistance in East African An. funestus populations represents a challenge to the control of this vector. However, the observed carbamate and organophosphate susceptibility offers alternative solutions for resistance management.