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Establishment of a large semi-field system for experimental study of African malaria vector ecology and control in Tanzania.

Ferguson HM, Ng'habi KR, Walder T, Kadungula D, Moore SJ, Lyimo I, Russell TL, Urassa H, Mshinda H, Killeen GF, Knols BG - Malar. J. (2008)

Bottom Line: The development of Semi-Field Systems (SFS) has been proposed as the best mechanism for bridging this gap.The SFS at Ifakara was completed and ready for use in under two years.Preliminary observations indicate that realistic and repeatable observations of anopheline behaviour are obtainable within the SFS, and that habitat and climatic features representative of field conditions can be simulated within it.

View Article: PubMed Central - HTML - PubMed

Affiliation: Division of Infection and Immunity, University of Glasgow, G128TA Glasgow, UK. H.Ferguson@bio.gla.ac.uk

ABSTRACT

Background: Medical entomologists increasingly recognize that the ability to make inferences between laboratory experiments of vector biology and epidemiological trends observed in the field is hindered by a conceptual and methodological gap occurring between these approaches which prevents hypothesis-driven empirical research from being conducted on relatively large and environmentally realistic scales. The development of Semi-Field Systems (SFS) has been proposed as the best mechanism for bridging this gap. Semi-field systems are defined as enclosed environments, ideally situated within the natural ecosystem of a target disease vector and exposed to ambient environmental conditions, in which all features necessary for its life cycle completion are present. Although the value of SFS as a research tool for malaria vector biology is gaining recognition, only a few such facilities exist worldwide and are relatively small in size (< 100 m2).

Methods: The establishment of a 625 m2 state-of-the-art SFS for large-scale experimentation on anopheline mosquito ecology and control within a rural area of southern Tanzania, where malaria transmission intensities are amongst the highest ever recorded, is described.

Results: A greenhouse frame with walls of mosquito netting and a polyethylene roof was mounted on a raised concrete platform at the Ifakara Health Institute. The interior of the SFS was divided into four separate work areas that have been set up for a variety of research activities including mass-rearing for African malaria vectors under natural conditions, high throughput evaluation of novel mosquito control and trapping techniques, short-term assays of host-seeking behaviour and olfaction, and longer-term experimental investigation of anopheline population dynamics and gene flow within a contained environment that simulates a local village domestic setting.

Conclusion: The SFS at Ifakara was completed and ready for use in under two years. Preliminary observations indicate that realistic and repeatable observations of anopheline behaviour are obtainable within the SFS, and that habitat and climatic features representative of field conditions can be simulated within it. As work begins in the SFS in Ifakara and others around the world, the major opportunities and challenges to the successful application of this tool for malaria vector research and control are discussed.

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Related in: MedlinePlus

Habitat features within the SFS section designated for a free-living An. arabiensis population: (a) traditional mud-walled house, (b) chicken coop with clay pot refugia, (c) artificial breeding site and banana plant, (d) Cattle shed containing calf host.
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Figure 4: Habitat features within the SFS section designated for a free-living An. arabiensis population: (a) traditional mud-walled house, (b) chicken coop with clay pot refugia, (c) artificial breeding site and banana plant, (d) Cattle shed containing calf host.

Mentions: As described above, one section of the SFS was set aside for establishment of a free-living population of An. arabiensis within conditions that mimic those of the natural environment. To achieve this, a domestic compound consisting of a mud-walled, thatched-roof house (2.6 m × 3 m × 2.5 m, Figure 4a), a typical outdoor toilet (1.4 m × 1.7 m × 2 m), and traditional chicken coop (1.8 m × 1.9 m × 2 m, Figure 4b) were constructed within this section by local builders. Grasses and other plants that emerged from the soil brought in from the local environment were allowed to grow. Additional plants common to the surrounding environment such as banana (Figure 4c), potatoes, rice, and castor bean (Ricinus communis L.) were introduced. A sprinkler system was installed so that varying levels of rainfall could be simulated. Five breeding sites were created by burying plastic buckets into the soil (50 cm diameter), adding 5 cm of soil, and filling them with water to a depth of 25 cm (Figure 4c). As An. arabiensis is somewhat zoophilic [61-64], regular blood meals can be provided to free-living mosquitoes within this section by introducing a cow or calf for a few nights each week (Figure 4d).


Establishment of a large semi-field system for experimental study of African malaria vector ecology and control in Tanzania.

Ferguson HM, Ng'habi KR, Walder T, Kadungula D, Moore SJ, Lyimo I, Russell TL, Urassa H, Mshinda H, Killeen GF, Knols BG - Malar. J. (2008)

Habitat features within the SFS section designated for a free-living An. arabiensis population: (a) traditional mud-walled house, (b) chicken coop with clay pot refugia, (c) artificial breeding site and banana plant, (d) Cattle shed containing calf host.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2543042&req=5

Figure 4: Habitat features within the SFS section designated for a free-living An. arabiensis population: (a) traditional mud-walled house, (b) chicken coop with clay pot refugia, (c) artificial breeding site and banana plant, (d) Cattle shed containing calf host.
Mentions: As described above, one section of the SFS was set aside for establishment of a free-living population of An. arabiensis within conditions that mimic those of the natural environment. To achieve this, a domestic compound consisting of a mud-walled, thatched-roof house (2.6 m × 3 m × 2.5 m, Figure 4a), a typical outdoor toilet (1.4 m × 1.7 m × 2 m), and traditional chicken coop (1.8 m × 1.9 m × 2 m, Figure 4b) were constructed within this section by local builders. Grasses and other plants that emerged from the soil brought in from the local environment were allowed to grow. Additional plants common to the surrounding environment such as banana (Figure 4c), potatoes, rice, and castor bean (Ricinus communis L.) were introduced. A sprinkler system was installed so that varying levels of rainfall could be simulated. Five breeding sites were created by burying plastic buckets into the soil (50 cm diameter), adding 5 cm of soil, and filling them with water to a depth of 25 cm (Figure 4c). As An. arabiensis is somewhat zoophilic [61-64], regular blood meals can be provided to free-living mosquitoes within this section by introducing a cow or calf for a few nights each week (Figure 4d).

Bottom Line: The development of Semi-Field Systems (SFS) has been proposed as the best mechanism for bridging this gap.The SFS at Ifakara was completed and ready for use in under two years.Preliminary observations indicate that realistic and repeatable observations of anopheline behaviour are obtainable within the SFS, and that habitat and climatic features representative of field conditions can be simulated within it.

View Article: PubMed Central - HTML - PubMed

Affiliation: Division of Infection and Immunity, University of Glasgow, G128TA Glasgow, UK. H.Ferguson@bio.gla.ac.uk

ABSTRACT

Background: Medical entomologists increasingly recognize that the ability to make inferences between laboratory experiments of vector biology and epidemiological trends observed in the field is hindered by a conceptual and methodological gap occurring between these approaches which prevents hypothesis-driven empirical research from being conducted on relatively large and environmentally realistic scales. The development of Semi-Field Systems (SFS) has been proposed as the best mechanism for bridging this gap. Semi-field systems are defined as enclosed environments, ideally situated within the natural ecosystem of a target disease vector and exposed to ambient environmental conditions, in which all features necessary for its life cycle completion are present. Although the value of SFS as a research tool for malaria vector biology is gaining recognition, only a few such facilities exist worldwide and are relatively small in size (< 100 m2).

Methods: The establishment of a 625 m2 state-of-the-art SFS for large-scale experimentation on anopheline mosquito ecology and control within a rural area of southern Tanzania, where malaria transmission intensities are amongst the highest ever recorded, is described.

Results: A greenhouse frame with walls of mosquito netting and a polyethylene roof was mounted on a raised concrete platform at the Ifakara Health Institute. The interior of the SFS was divided into four separate work areas that have been set up for a variety of research activities including mass-rearing for African malaria vectors under natural conditions, high throughput evaluation of novel mosquito control and trapping techniques, short-term assays of host-seeking behaviour and olfaction, and longer-term experimental investigation of anopheline population dynamics and gene flow within a contained environment that simulates a local village domestic setting.

Conclusion: The SFS at Ifakara was completed and ready for use in under two years. Preliminary observations indicate that realistic and repeatable observations of anopheline behaviour are obtainable within the SFS, and that habitat and climatic features representative of field conditions can be simulated within it. As work begins in the SFS in Ifakara and others around the world, the major opportunities and challenges to the successful application of this tool for malaria vector research and control are discussed.

Show MeSH
Related in: MedlinePlus