Anopheline Mosquito Vectors and Malaria Transmission Dynamics Along an Altitudinal Gradient on the Highlands of Mambilla Plateau, Nigeria
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Date
2019Author
Liatu, Columbus, G
Type
ThesisLanguage
enMetadata
Show full item recordAbstract
The presence of a suitable and efficient vector is a major determinant of local malaria
transmission intensity.In the last few years, the Mambilla Plateau has witnessed an
influx of people from different parts of the country who engage in various
anthropogenic activities that could have profound consequence on vectors and malaria
transmission in the region.Until now, no data exist for vector anopheline species and
malaria transmission intensity for the Mambilla Plateau, a highland region prone to
malaria epidemics. The study aimed to provide the baseline data on the anopheline
vectors of malaria and malaria transmission on the highlands of Mambilla Plateau,
Nigeria.The study was conducted in five locations along an altitudinal gradient
namely; Nguroje (1,885m), Yelwa (1,674m), Gembu (1,584m), Kakara (1,496m) and
Mayo Selbe (484m), above sea level. Collections were conducted once every month
from November 2015 to October 2017. Adult mosquitoes were captured by the use of
Centre for Disease Control (CDC) modified light traps and Pyrethrum Spray Catches
(PSC). Larvae were sampled using the standard dipping methodand reared to
adulthood. Larval habitats were identified and characterized according to the features
observed in the field. The physicochemical parameters were also measured. The
mosquitoes were identified morphologically by microscopy using taxonomic
keys.Anopheles gambiae sensu lato (sl)where further identified genetically to sub
species and molecular levels (M and S) forms by Polymerase Chain Reaction
(PCR).Enzyme Linked Immunosorbent Assay (ELISA) was used to test for
Plasmodium falciparum infectivity as well as source of bloodmeal.A total of 878
anophelines comprising of five species namely; Anopheles gambiae sl,An. coustani,
An. funestus, An. pharoensis, and An. rufipes,were collected. An. gambiaeslwas the
highest number collected in all the locations and seasons (757). An. gambiaesensu
stricto was the only member of theAn. gambiae complex identified by PCR, the S
molecular form of the vector dominated over the M form (520 and 192)
respectively.There was a very strong positive correlation between the S and M forms,
r2 = 0.94204.Mayo-selbe had the highest species abundance of 572 but lowest species
diversity(H’= 0.24). Yelwa had the least species abundance (24) but very high
diversity (H’=0.81). December recorded highest abundance of anophelines (235) but
very low diversity (H’ = 0.28). A total of 60 larval habitats were sampled and
characterized. Swamps were the highest number of habitats encountered (15) and tree
trunk was the least (1). There was relatively low occurrence of positive breeding
habitats along the altitudinal locations. Only six were positive. This could be due to
the temporary nature of the habitats. Larvae were associated with still, clear and
sunlit temporary habitats with a wide range of physicochemical parameters.There
were two peak malaria transmission seasons in the Mambilla Plateau, in December
and June. All malaria transmission indices namely; sporozoites rates (SR), man biting
rates (MBR) and entomological inoculation rates (EIR) decreased with increasing
altitude. These were in the range of SR (0.17-3.55%), MBR (0.002-2.56) and EIR
(0.003-9.09 ib/p/n). Only 22.67% of the mosquitoes had fed on human blood, other
sources of blood meal were unknown.The human blood index ranged from (0.00 to
0.22). Nguroje and Kakararecorded the lowest while Mayo-selbe recorded the
highest.In the current study malaria transmission is occurring in the Mambilla Plateau
and An. gambiae s. s is the major species of An. gambiaecomplex involved. However,
other species that were collected have been reported to play secondary roles in
transmission in other parts of Africa. Malaria control in the study area should
therefore focus on An. gambiae s. s. There should also be close monitoring and
surveillance of the other anophelines species that were encountered in the study area
as these may become potential vectors in the future.This study has provided the
baseline information about the anophelines malaria vectors and malaria transmission
in the highlands of Mambilla Plateau, which would be helpful for the sustainable
management of vector mosquitoes and also inform policy measures to prevent or
counter malaria epidemics in the future.
Publisher
University of Nairobi
Rights
Attribution-NonCommercial-NoDerivs 3.0 United StatesUsage Rights
http://creativecommons.org/licenses/by-nc-nd/3.0/us/Collections
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