A Dissertation submitted to the Faculty of Medicine,
University of the witvmtersrand, Johannesburg, in
fulfilment of the requirements for the Degree of Master
of Science in Medicine. / The potential of Aedes aegypti to act as a vector of
dengue (DEN) viruses was assessed in the tropical and
subtropical regions of South Africa. The prevalence in
bamboo pot ovitraps, utilization of artificial larval
habitats and antihropophflism of Ae. aegypti was measured
in fifteen populations from coastal Natal and five from
the Transvaal. Pot indices generally ranged from 40-100
per cent (x±s;c= 60,3±9,8), with a mean abundance index
of 0,43±0,15 (sx) mosquitoes/pot/day. Artificial
container indices ranged from 11-83 per cent (X±si =
56,8±5,6). Biting rates ranged from 0,2-29,0 per manhour,
in direct relationship to the level of
urbanization. The feral Nduntupopulation was least
anthropophilic, although pot and abundance indices were
high.
To investigate the presence of subspp. aegypti and
formosus, the pale scales on tergite-1 were counted in
ten or more siblings from each of 196 families,
representing eighteen populations. At least 118 of these
families were heterogeneous, each containing some
siblings with no pale scales and others with pale scales
on tergite-1, thus invalidating this character for
distinguishing between the subspp. Isozyme
electrophoresis 'did not provide diagnostic electromorphs
for distingllishing between different populations.
Allelomorph frequencies and the numberof pale scales on
tergite-l and tergite-2 differed significantly in
individual populations but not between anthropophilic and
non-anthropophilic populations. As there was no
correlation between tergal morphology, isozymes and
anthropophilism, the populations could not be resolved
into the two subspp. Based on the only morphological
character that appears to be reliable, viz. the blackness
of the background scales, all of the populations are
probably Ae. aegypti formosus.
The vector competence of five populations for DEN-1
and DEN-2 viruses was tested in the laboratory after
allowing mosquitoes to feed on an infective blood-virus
mixture. Viral antigen was detected by indirect
fluorescent antibody test. Head-squash infection rates
(HSIRs)ranged from 11-54 per cent for DEN-land from 19-
46 per cent for DEN...2. Transmission rates (TRs) were
determined by in vitro capillary method and ranged from
67-100 per cent for DEN-1 and from 11-86 pier cent for
DEN-2.Meanvector competence indices (calculated from
HSIRsand TRS) ware 0,13-0,41 for DEN-l and 0,,18-0,34 for
DEN-2.It is concluded that, should DEN be reintroduced
to South Africa via the shipping or tourist industries,
Ae. aegypti would be an efficient urban vector. The
Durban population is of particular epidemiological
importance because it was highly anthropophilic and was
the most vectorially competent of the South African
populations. / Andrew Chakane 2018
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/26142 |
| Date | January 1993 |
| Creators | Kemp, Alan |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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