The Transmission Attributes Of Peri-Urban Malaria In Lusaka, Zambia

Abstract

Malaria is a disease of great public health importance in Zambia. It is a major cause of morbidity and mortality and is endemic in all nine provinces. The malaria transmission paradigms may be higher in urban populations than in peri-urban and rural population and peri-urban areas tend to become less malarias as they become better established. Anopheles gambiae s.s, Anopheles arabiensis and Anopheles funestus are the most important malaria vectors in Zambia but the knowledge of their actual distribution and the resultant malaria cases in peri-urban Lusaka is fragmented. This study assessed malaria transmission factors and attributes in peri-urban Lusaka by determining Anopheles species prevalence and bionomics, parasite rates, residents KAP levels and provide the evidence of local transmission as well as recommending appropriate vector control strategies. This study was conducted in four locations of peri-urban Lusaka, namely Kabanana, Chazanga, Chipata and Kalikiliki from May to October. Data was collected through entomological and parasitological surveys, Questionnaire and PCR methods. Written consent was sought from participating subjects for inclusion in the study. The study was empirical in nature with appropriate scientific methods and ideal sample sizes and data was analyzed by Epi-Info 3.2.2. This study identified three kinds of Anopheline mosquito breeding habitats in peri-urban Lusaka, namely Transient, Semi-permanent and Permanent. The semi-permanent were the most prevalent and most preferred breeding sites for Anopheles species. Anopheles gambiae s.l constituted 10% of the indoor pyrethrum collected mosquitoes. Molecular speciation showed that Eighteen (95%) Anopheles specimens amplified for Anopheles gambiae s.s at 390 bp and only one (5%) specimen amplified for Anopheles arabiensis 315 bp.

Parasite rates in peri-urban Lusaka were at 25.6% and were completely due to Plasmodium falciparum mono infections with 98.7% trophozoites and 1.3% gametocytaemia rates. The 0-4 years group had the highest infection rate (31.8%) with the 5-15 years and above 15 year age groups supporting the highest and lowest parasitaemia densities respectively. There were appreciably high levels of knowledge on malaria as regards the disease among peri-urban Lusaka residents but low knowledge of control and prevention, which explains the high infection rates. It was also established that migration does not contribute significantly towards transmission. The congestion in households has probably contributed to the high transmission in peri-urban Lusaka. Local transmission of malaria in peri-urban Lusaka was evident in that 31.8% of febrile children under the age of five had malaria confirmed by microscopy. Furthermore, the presence of children under five years (78%) who lived in peri-urban Lusaka, with no history of travel, the presence of gametocyte bearers and the vector in the community perpetuate the transmission cycle. Local transmission is also strongly supported by the proximity of ideal breeding habitats and the presence of efficient Anopheles gambiae complex species (Anopheles gambiae and Anopheles arabiensis) in the houses. The study concluded that there is local transmission of malaria in peri-urban Lusaka. The presence of both Anopheles gambiae s.s and Anopheles arabiensis merits the implementation of an Integrated Vector Management criterion in peri-urban Lusaka based on this transmission paradigm.