ABSTRACT
Human and animal African trypanosomiasis remains a major
health problem in Cameroon. These diseases are transmitted by a vector called
the tsetse fly or Glossina. Glossina pallicera pallicera is one of the
most widespread species and is responsible for animal African trypanosomosis
(AAT) in the focus of Campo. However, very little information about its biology
and population structure is available. In order to better understand the
genetic structure of tsetse fly populations of the Southern Cameroon forest, we
carried out a study on the molecular characterization of Glossina pallicera
pallicera in the human African trypanosomiasis (HAT) focus of Campo.
For this purpose, we carried out entomological studies in
three villages (Akak, Campo Beach and Rio Campo) of the HAT focus of Campo.
Flies were captured using pyramidal traps. The CTAB (Cetyl Trimethyl Ammonium
Bromide) method was used to extract DNA from tsetse thy legs and thereafter,
nine microsatellite markers were used to genetically characterize G. p.
pallicera.
In this study, 72 tsetse flies belonging to 5 different
species were used: 45 Glossina pallicera pallicera, 17 Glossina
palpalis palpalis, 4 Glossina submorsitans, 3 Glossina
caligenea, 2 Glossina nigrofusca and one Glossina
fuscipes. Amongst the nine microsatellite markers used, four of them were
not considered for the population genetics studies because less than 50% of
samples were amplified by these markers. For the five markers considered for
the genetic analyses, the amplification rate varied from one marker to another:
91.11 % for 55.3; 97.77 % for PGP13; 97.77 % for GPCAG; 95.55 % for C102 and
84.44 % for PGP24. The five microsatellite markers showed several
genotypes of G. p. pallicera circulating in villages of the Campo
sleeping sickness focus. These results indicate the genetic polymorphisms
within G. p .pallicera populations of the same village and of
different villages. Our results revealed no significant heterozygote deficiency
(FIS (index of fixing of the individuals in the subpopulations) =
0.04; P = 0.31) between G. p. pallicera populations. However, a
significant heterozygote deficiency (FIS = 0.145; P = 0.0001) was
observed for G p. palpalis populations. This heterozygote deficiency
could be due to strong variations between FIS values at different
loci. Between G. p. pallicera subpopulations, no significant
difference was observed for the FST (index of fixing between
subpopulations of the total population) values; indicating no structuration
within subpopulations of different villages. Nevertheless, significant
differences were observed between G. p. pallicera and other tsetse
flies species.
These first investigations on the population genetics of G
p. pallicera have revealed an absence of sub-structuration between these
vector populations and different genotypes circulating in villages of the Campo
sleeping sickness focus.
Key words: Microsatellite markers, Glossina
pallicera pallicera, PCR, population genetics
XII
Caractérisation génétique de Glossina
pallicera pallicera circulant dans le foyer de la maladie du sommeil de
Campo du Sud forestier Camerounais rédigé par GOMSEU DJOUMSIE
Emmanuel Boris
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