Resting Behaviour of Endophilic Anopheline Vectors in Three Ecological Zones of Southern Ghana and its Implications for the use of Entomopathogenic Fungi
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Date
2014-09
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University of Ghana
Abstract
The aim of this study was to determine the resting behaviour and factors that
influence the choice of resting sites by endophilic anopheline mosquitoes in southern
Ghana. The study was carried out in six villages across three ecological zones of
southern Ghana, including: the forest ecological zone (FEZ), the coastal savannah
ecological zone (CSEZ) and the forest-transition ecological zone (FTEZ). For every
mosquito collected, the indoor resting sites was characterised and microclimate at the
actual resting site recorded using a data logger. In the laboratory, full diagnostics was
carried out on a sub-sample. Resting devices constructed from different materials
were tested in a screen house and in village rooms. The dominant anopheline vectors
include Anopheles gambiae s.s., An. coluzzii and An. funestus. An gambiae s.s. was
the most dominant species in the villages from the FEZ and FTEZ, whereas An.
coluzzii was most dominant in the CSEZ. An. funestus was present in the FEZ and
CSEZ but almost absent from the FTEZ. The two kdr mutations (L1014F and
L1014S) were present in all the ecological zones and in both An. gambiae s.s. and An.
coluzzii. This is the first report of the L1014S mutation from Ghana. The populations
were highly anthropophagic and Plasmodium falciparum was present in populations
from all the villages studied. Woody materials appeared to be the most preferred
resting materials for An. gambiae, accounting for 47 % of all the resting sites for that
species. They were also found on fabrics (26 %), wall materials (12 %), and roof
materials (10 %). Similarly, An. funestus preferred to rest on woody materials (58 %),
followed by wall materials (21 %), fabrics (11 %) and roofing materials (7 %). For
An. coluzzii, fabrics were the most preferred resting materials (38 %) followed by roof
materials (21 %), wooden materials (19 %) and wall materials (9 %). All the three
vector species preferred to rest higher up the room and closer to the walls, with large proportions of An. gambiae s.s. (75.94 %), An. funestus (73.60 %) and An. coluzzii
(58.19 %) found resting at heights above 200 cm from the floor. With reference to the
nearest wall, high proportions of An. gambiae s.s. (68.38 %), An. coluzzii (80.98 %)
and An. funestus (68.29 %) were collected within 50 cm from the closest wall.
Although microclimatic conditions varied widely in the indoor environment and even
at the specific resting sites, higher proportions of the endophilic anophelines were
collected within narrow ranges of temperature (27-30 oC), relative humidity (65-75
%) and light intensity (0-20 Lux). Black felt and black cotton cloth were the most
preferred resting devices for blood-fed females in both screen house trials and field. In
general, the presence of the three most efficient vectors of malaria from indoor
collections in southern Ghana and the fact that they were highly anthropophagic and
effectively transmitting malaria is a high call for intensifying vector control efforts.
Knowledge of the indoor resting behaviour of the major endophilic Anopheles vectors
of southern Ghana paves the way for developing fungal spore deployment strategies
for field implementation. This study has established that all the three endophilic
Anopheles species in southern Ghana rest higher up in village rooms, prefer to rest on
darker coloured materials in cool humid areas. It has further demonstrated that black
felt and black cotton cloth are attractive to blood-fed females seeking resting sites to
digest blood meal and develop their eggs. Guided by this knowledge, future research
should focus on designing these preferred materials into resting devices that create
suitable microhabitats to which endophilic anopheline mosquitoes can be attracted
and contaminated with fungal spores. Further research is also needed to determine the
efficacy and persistence of fungal spores on these preferred resting materials so as to
determine application rates and frequency.
Description
Thesis(PhD)-University of Ghana, 2014
Keywords
Resting Behaviour, Endophilic Anopheline Vectors, Ecological Zones, Southern Ghana