Titus K. Mukiama

Seasonal population changes and malaria transmission potential of Anopheles pharoensis and the minor anophelines in Mwea Irrigation Scheme, Kenya.

A study in 1984 and 1985 showed that Anopheles gambiae s.l. and An. pharoensis were the major anophelines in Mwea Irrigation Scheme, Kenya, constituting 83.86% and 15.69% of the catch respectively. Four minor species made up the remaining 0.45%. The irrigation phase of the rice cultivation cycle in August, which linked the flooding effects of the two rainy seasons, resulted in major population increases of An. pharoensis and enabled continuous breeding for up to 9 months per year. The average of mean monthly proportions of unfed, bloodfed, and gravid females was 26.6, 58.8, and 14.6% respectively. The Plasmodium falciparum sporozoite rates for An. pharoensis were 1.3% by ELISA and 0.68% by dissection, while those for An. funestus were 1.7% by ELISA and 1.25% by dissection. An. pharoensis can contribute to the epidemiology of Malaria in the Mwea area.

Field studies of larval Anopheles arabiensis Patton of Mwea Irrigation Scheme, Kenya

Between May 1984 and December 1985, the population of immature stages of Anopheles arabiensis was sampled by the dip method at sites close to two villages in Mwea Irrigation Scheme, Kenya. Larval presence corresponded to rainy seasons and the flooding phase of the rice cycle. No larvae were found during the postharvest dry season. The instar composition, age distribution and survivorship curves for the different stages were determined. Pupal productivity for Mwea rice fields was estimated to be 1% of the total immature population.RésuméEntre mal 1984 et décembre 1985, la population des larves de Anophèles arabiensis etaient etudiés par la méthode d’immersion près des deux villages de la région irriguée de Mwea au Kenya. La présence des larves correspondaient avec les saisons pluvieux et l’inondation des champs de riz. Ils n’avaient pas les larves trouvaient près de la moisson, pendant la saison sèche. La composition des larves, la distribution de l’âge, et les courbes de survie étaient résolus. La productivité des mostiques An. arabiensis de Mwea étaient estimés être 1% de la population total pas mûr.

Irrigation scheme or mosquito hazard : a case study in Mwea irrigation scheme

A survey of the mosquito fauna in the Mwea-Tebere Irrigation Scheme in Kenya was conducted between 1984 and 1985. Two genera, Anopheles and Culex were found indoors in large numbers. The major species were Anopheles gambiae s.l., Anopheles pharoensis, and Culex quinquefasciatus, comprising 66% and 21% of the total catch, respectively. The large numbers of mosquitoes found resting indoors showed seasonal population fluctuations. The seasonal population increases observed were due to the availability of larval breeding conditions over a long period of time and to man-made environmental changes. These changes included irrigation canals and rice paddies. The irrigation canals and rice paddies were flooded from August till December, thus linking the flooding effects of the two rainy seasons. This enabled mosquitoes to breed continuously for up to 9 months per year.

Population and cytogenetic observations on Anopheles arabiensis Patton of Mwea irrigation scheme, Kenya.

A study of the mosquito fauna of the Mwea Rice Irrigation Scheme, Kenya, carried out during 1984 and 1985 identified 13 species, with Anopheles gambiae s. l. comprising 65.71% of the total collection. X-chromosome identification of 652 semi-gravid females resulted in 649 (99.5 %) positive identifications of An. arabiensis, implicating it as the noxious member of the An. gambiae complex present. Inversion polymorphism of chromosomes 2Rb and 3Ra karyotypes was studied in one village population. Seasonal population changes were found to be heavily dependent on rice field surface water. Artificial irrigation for rice farming greatly extended the breeding period per year by linking up the two wet seasons. Adult females fed more frequently on bovids than humans. The mean percentage gonotrophic condition of all females caught in the villagesof Karima, Thiba, Mucii-wa-Urata and Rurumi by pyrethrum spray-sheet collections, miniature light-traps and exit window traps was 69 % bloodfed, 18 % unfed and 13 % gravid. These proportions were statistically shown to be within predictable limits over time and space. The sporozoite infection rate in adult females was 0.55% by manual dissections and 1.2% by the ELISA technique.RésuméUne etude de la faune des moustiques de la région irriguées de Mwea au Kenya, effectuée en 1984 et 1985 a identiné 13 espèces avec Anopheles gambiae s. l. composant 65.71 % de la collection totale. Les identification de chromosome X sur 652 demi-gravide femelles donne 649 (99.5%) identifications positives de An. gambie, l’implicant comme membre nocive de An. gambiae complexe presente. Nous avons etudié dans une population villageoise la polymorphisme inversive des karyotypes des chromosomes 2Rb et 3Ra. Les changements saisonieres dans la populations dependant enormement de la surface d’eau du terrain. L’irrigation artificielle de la culture de riz prolonge considerablement la period de croissance annuelle en rapprochant les deux saisons pluvieuses. Les femelles des adultes se nourrissent plus frequenment sur les bovides que sur les humains. La pourcentage moyenne de la condition gonotrophique de toutes les femelles capturées dans les villages de Karima, Thiba, Mucii-wa-Urata et Rurumi en utilisant 3 methodes de capture, c’est a dire, par le pyrethe, par le piège lumière et par le piège de le fenðre d’exit est de 69 % nourri de sang, 18% non-nourri, et 13% de gravide. Ces proportions statistiquement restent dans les limites de prediction sur l’espèce et le temps. Le taux d’infection de sporozoite chez le femellesdes adultes est de 0.55% par dissection manuelle et de 1.2% par le technique ELISA.

Genetic variation in wild Anopheles arabiensis Patton of Mwea Irrigation Scheme, Kenya

Electrophoretic variation was determined at eight enzyme loci in Anopheles arabiensis from four villages in Mwea Irrigation Scheme, Kenya. Seven loci had polymorphic alleles of which at least two were common. Pooled allele frequencies at the Pgm, ß-Had and Odh loci were in Hardy-Weinberg equilibrium, while those at the Ao, Idh, Adh, Est-1 and 6-Pgd loci showed significant deviations. The frequency of heterozygotes at the Adh, Est-1 and 6-Pgd loci was less than expected, while at the Ao locus, there was an excess. A 2 x 4 contingency χ2-test for each of the loci not in Hardy-Weinberg equilibrium indicated an association between the respective gene frequencies and the villages. The suggested explanation for these observations is that each village constitutes a distinct population, and that the pooled data introduced the Wahlund effect. Allele frequencies at individual loci per village population are most likely at Hardy-Weinberg equilibrium. Larger samples per village need to be examined to facilitate a goodness of fit χ2-test between observed and expected frequencies.RésuméLa variation électrophorétique était déterminée pour huit bandes enzymatiques dans Anophèles arabiensis provenant de quatre villages de la région irriguée de Mwea au Kenya. Sept bandes avaient des allèles polymorphiques dont au moins deux étaient communs. Les fréquences ressemblées des allèles pour les bandes Pgm, ß-Had et Odh étaient en équilibre de Hardy-Weinberg, alors que celles de Ao, Idh, Adh, Est-1 et 6-Pgd montraient des déviations significatives. La fréquence des hétérozygotes pour les bandes de Adh, Est-1 et 6-Pgd était la moins attendue alors que pour la bande Ao, il y avait un excès. Une contingeance 2 x 4 du test χ2 pour chaque bande non en équilibre de Hardy-Weinberg indiquait une association entre les fréquences respectives de genes et les villages. L’explication suggérée pour ces observations est que chaque village constitue une population distincte et que les données rassemblées introduisaient l’effet Wahlund. Les fréquences des allèles á une bande individuelle par population de village étaient plus vraisemblablement en équilibre de Hardy-Weinberg. Un plus grand nombre d’échantillons par village est nécessaire pour étre en accord avec le test χ2 entre les fréquences observées et celles attendues.

Ceratitid fruitflies infesting fruit crops in Kenya

Between 1984 and 1988, a survey of fruit-infesting ceratititl fruitflies was conducted in 11 agricultural districts in Kenya. Samples of up to 18 different fruit crops were examined for infestation. The four species of fruitfly found were Ceratitis capitata, C. rosa (Pterandrus rosa), C. nigra (Trirhithrum coffeae) and C. cosyra (Pardalaspis cosyra). The first three were sympatric infestants of coffee, while the latter was exclusively found in mangoes. In addition, C. rosa also infested loquat, guava and custard apple. C. capitata infested commercial orange cultivars. This species was predominant in the main arabica coffee growing areas in the central highlands. C. rosa and C. nigra were more widespread, occurring in high proportions in most parts of the country. Generally, the proportions of the three species per coffee sample, and the mean number of each species per kg of coffee, tended to vary considerably over time and space.RésuméDans il régions agricoles au Kenya une prospection sur les mouches fruitiéres a été effectuée entre 1984 et 1988. Jusquà 18 espéces d’arbres fruitiérs ont été examinés pour infestation. Quatre espéces des mouches fruitiéres ont été déterminées. Ceratitis capitata, C. rosa (Pterandrus rosa) et C. nigra (Trirhithrum coffeae) infestant le caféier tandis que C. cosyra (Pardalaspis cosyra a été trouvé exclusivement sur la manguier. En plus, C. rosa infestait le bibacier, le goyave et l’Annona. C. capitata infestait les orangers. Cette espéce est prédominant dans les “Central Highlands” où on cultive le caféier arabica. Par contre, C. rosa et C. nigra étaient omniprésents. Une variation considérable a été observé dans l’espace et dans le temps, dans la distribution proportionelle des trois espéces sur les échantillons sur caféier.

Comparative dehydrogenase activity during the ontogenesis of the yellow fever mosquito Aedes (Stegomyia) aegypti L. (diptera:culicidae)

Abstract 1. 1. α-GPDH in most active in adults, LDH in third instar larvae, and MDH in third instar larvac. 2. 2. During pre-pupal growth, LDH is the most active enzyme, followed by MDH and α-GPDH; while during post-pupal growth, MDH is most active followed by α-GPDH and LDH. 3. 3. Increased enzyme activity is in response to changing physiological and physical environments, and is due to temporal activation of new gene loci indicated by the production of new α-GPDH and MDH isozymes. LDH activity is probably controlled by the temporal action of regulatory gene(s). 4. 4. Dehydrogenase activity profiles during ontogenesis are probably species-specific.

Y-autosome genetic sexing strain of Anopheles albimanus (Diptera: Culicidae)

Stripe (st+) is a dominant trait on chromosome 3R in region 33B on the cytological chromosome map of Anopheles albimanus. It is expressed as a white longitudinal stripe in fourth stage larvae and pupae, and marks a Y-autosome translocation stock T(Y; 3R)3. Pseudolinkage analysis of the available markers to the translocation breakpoint showed complete absence of recombinant progeny between T(Y;3R)3 and st+. The two loci most likely either overlap or are very closely linked. This translocation strain can be genetically sexed by selection of the stripe marker.RésuméStripe (st+) est un caractère dominant localise sur le chromosome 3R de la region 33B de la carte chromosomique de Anopheles albimanus. Ce caractère s’exprime comme une bande blanche longitudinale dans les larves et pupae du/quatrième étage et correspond a une souche T(Y;3R)3 caractérisée par une translocation Y-autosomique. Une analyse pseudoliaison entre les marqueurs disponibles et le point de rupture de la translocation a montre une absence complete de descendance recombinante entre T(Y; 3R)3et st+. Les deux loci sont probablement superposes ou lier très étroitement. Le sexe de la souche transloquée/peut être determine génétiquement par selection du marqueur stripe.

Electrophoretic variation in wild Anopheles pharoensis Theobald in Mwea Irrigation Scheme, Kenya

Abstract—The electrophoretic variation of four enzymes of wild Anopheles pharoensis in Mwea Irrigation Scheme, Kenya, was studied between 1987 and 1988. The enzyme loci examined were aldehyde oxidase, α-glycerophosphate dehydrogenase, β-hydroxyacid dehydrogenase and lactate dehydrogenase. All the loci examined were dimorphic. A mean heterozygosity (H) of 0.341 was obtained, which is comparable to values for other mosquito species. The allelic frequencies were in genetic disequilibrium compared to Hardy-Weinberg predictions. It is proposed that there may be more than one species in the taxon Anopheles pharoensis.Résumé—Une étude de variation electrophorétique de 4 enzymes chez des populations sauvages de Anopheles pharoensis a été menée dans le projet d’irrigation de Mwea, Kenya, entre 1987 et 1988. Les loci d’enzymes éxaminés ont ete aldéhyde oxidase, α-glycerophosphate déhydrogénase, β-hydroxyacid déhydrogénase et lactate déhydrogénase. Cette étude démontre un bas niveau de variation des alleles et tous les loci sont dimorphiques. La moyenne calculée pour l’hétérozygosité est de 0,341 et cette valeur est comparable aux valeurs d’autres espèces de moustique. Les fréquences des allèles dans les populations étudiées sont en déséquilibre génétique selon les prévisions de Hardy-Weinberg. Ces résultats confirment la proposition d’autres chercheurs disant qu’il y a peut-etre plus d’une espèce dans le taxon de Anopheles pharoensis.

INDIGENOUS FLORA CONSERVATION IN KENYA

Summary - Kenyan vegetation has been as varied as its natural habitats, although considerable environment degradation has taken its toll in recent years. The major loss of the indigenous vegetation began with the introduction of plantation farming by European settlers early this century. Virgin forests on appropriated land were cleared away, the local people were concentrated into tribal reserves, and a conflict that spanned decades was thus started. The reserves were soon overcrowded, overstocked and in excess of their carrying capacity. A net illegal movement of the African population into restricted areas ensued, and is continuing even today. Forests were a favorite target area as they provided farmland, building materials and fuel wood. In recent years, forest hardwood species have become threatened as the demand for timber continues to rise. Rangeland species, too, have become threatened as new settlements continue to infiltrate these marginal areas. The Kenya government has, however, responded to these problems sufficiently by taking both legislative and administrative measures aimed at achieving a sustained status of natural resources conservation. Consequently, environmental awareness and participation is gradually permeating into, not only institutional and community, but also family levels of society. While fully employing in situ means, ex situ methods are likely to play a major role in the future, particularly as the country utilizes the new technologies emerging from tissue culture, cell culture and genetic engineering.