Genetic variation in two populations of the brown ear tick, Rhipicephalus Appendicula tus, in Kenya
Abstract
Several studies have shown that Rhipicephalus appendiculatus from
geographically isolated areas differ in their susceptibilities to Theileria paIva, the
haemoprotozoan causative agent of East Coast Fever. In Kenya, R. appendiculatus from
Muguga have been reported to be less susceptible to T parva infection than those from
Rusinga Islands. As the same tick species from different areas shows variation in vector
competence, it was considered to be of epidemiological interest to determine whether these
tick populations are genetically different. Most population genetic studies have been done
by comparing protein electrophoretic patterns, and more recently by DNA analysis.
However, all available techniques have limitations. It is therefore not advisable to rely on
only one technique.
In this study, two-dimensional protein electrophoresis and random amplified
polymorphic DNA Polymerase, chain reaction were used to compare two R.
appendiculatus populations from Muguga and Rusinga, in Kenya. Most proteins were
common to both populations. However, some proteins were population-specific. Two
proteins (M, ~14.4-19,OOO), one protein (M, ~26,OOO) and two proteins (M, ~47-50,OOO),
were specific to the Muguga population. On the other ~~d, three proteins (M, ~14,OOO),
one protein (M, ~22,OOO), one protein (M ~29,OOO.), one protein (M, ~41,OOO), and three
proteins (M, ~45-48,OOO), were specific to the Rusinga population. Homologous proteins
are probably species-specific.
In the RAPD technique; both' pooled and individual tick DNA samples were
analysed. Five different primers wete used. In the pooled DNA, each primer gave some
population-specific bands. However, individualDNA samples showed considerable band variation among individuals within each population. The genetic distance between the two
populations averaged 0.047. This implies that these populations are closely related, sharing
about 95% of their genes.
The presence of population-specific proteins and DNA fragments, together with a
genetic distance greater than zero suggests that genetic differences exist between the two
populations. The observed differences may not be directly linked to a particular phenotype.
Nevertheless, it is possible that the differences in the vectorial capacities of these
populations may be accounted for by genetic factors. However, further studies will be
required to confirm this.
Citation
MScPublisher
School of Biological Sciences, University of Nairobi
Description
Degree of Master of Science (Biochemistry)