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Population and Cytogenetic Observations on Anopheles Arabiensis Patton of Mwea Irrigation Scheme, Kenya

  • Titus K. Mukiama
  • Richard W. Mwangi
Research Article

Abstract

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.

Key Words

Anopheles arabiensis Anopheles gambiae inversion polymorphism karyotypes ELISA technique Mwea Irrigation Scheme Kenya mosquitoes seasonal population dynamics gonotrophic condition sporozoite rates 

Résumé

Une 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.

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Copyright information

© ICIPE-ICIPE Science Press 1990

Authors and Affiliations

  • Titus K. Mukiama
    • 1
  • Richard W. Mwangi
    • 2
  1. 1.Department of BotanyUniversity of NairobiNairobiKenya
  2. 2.Department of ZoologyUniversity of NairobiNairobiKenya

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