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An indigenous malaria transmission in the outskirts of Addis Ababa, Akaki Town and its environs
Abstract
Background: In recent years malaria is becoming endemic in highland areas beyond its previously known upper limit of transmission. Assessment of the situation of the disease in such areas is necessary in order to institute appropriate control activities.
Objectives: The objectives of the study were to determine the prevalence of malaria, the parasite species involved and Anopheles species responsible in local malaria transmission.
Methods: A systematic sampling technique was used to select survey households. Blood films were collected monthly between October and December 1999 from all household members by a trained and experienced laboratory technician. Larval and adult mosquitoes were monthly collected using different methods from September 1999 to October 2000.
Results: Among 2136 examined blood films, 78(3.7%) of them were malaria positive of which 54(69%) were due to Plasmodium vivax and 24 (31%) due to P. falciparum. Anopheles gambiae s. l. (presumably An. arabiensis) and An. christyi were the dominant man-biting species, with the former being the major vector in the area. Both these species were found to be more of exophagic and active in the early evening, unlike An. pharoensis, which showed an endophagic tendency.
Conclusion: This study indicated that indigenous transmission of malaria occurs in the study area. Transmission is reckoned to be maintained by low density of vector species for short period of time under favorable conditions. Therefore, the acquisition of communal immunity is interrupted by long duration of non-malaria season leading to the occurrence of recurrent malaria epidemics.
[Ethiop.J.Health Dev. 2004;18(1):2-7]
Objectives: The objectives of the study were to determine the prevalence of malaria, the parasite species involved and Anopheles species responsible in local malaria transmission.
Methods: A systematic sampling technique was used to select survey households. Blood films were collected monthly between October and December 1999 from all household members by a trained and experienced laboratory technician. Larval and adult mosquitoes were monthly collected using different methods from September 1999 to October 2000.
Results: Among 2136 examined blood films, 78(3.7%) of them were malaria positive of which 54(69%) were due to Plasmodium vivax and 24 (31%) due to P. falciparum. Anopheles gambiae s. l. (presumably An. arabiensis) and An. christyi were the dominant man-biting species, with the former being the major vector in the area. Both these species were found to be more of exophagic and active in the early evening, unlike An. pharoensis, which showed an endophagic tendency.
Conclusion: This study indicated that indigenous transmission of malaria occurs in the study area. Transmission is reckoned to be maintained by low density of vector species for short period of time under favorable conditions. Therefore, the acquisition of communal immunity is interrupted by long duration of non-malaria season leading to the occurrence of recurrent malaria epidemics.
[Ethiop.J.Health Dev. 2004;18(1):2-7]
