Opportunistic feeding behaviour and partial exophily make An. arabiensis much more difficult to control by indoor residual spraying than any other vector in the Afro-tropical region. The persistent malaria outbreaks in Zimbabwe despite decades of indoor house spraying prompted this investigation into the role of An. arabiensis in malaria transmission and assessment of the possible impact of this control measure. The study was conducted in the malaria endemic districts of Binga and Gokwe. An. gambiae complex mosquitoes were collected from artificial outdoor resting sites, and from human dwellings by i) daytime hut searches, ii) pyrethrum spray catches and iii) exit window traps. Mosquito components were processed to enable: i) the distinction of An. arabiensis from An. quadriannulatus and An. merus on the basis of the pale band at the junction of the hind leg 3/4 tarsomeres; ii) species identification and scoring of inversion polymorphism on the basis of the X chromosome and autosomes respectively; iii) the determination of blood meal sources using the Ouchterlony precipitin test; and iv) identification of An. gambiae s.l. using polymerase chain reaction (PCR) and enzyme electrophoresis techniques. Entomological assessment of residual spraying included determining: the vector resting densities indoors and outdoors, bioassay and insecticides susceptibility tests. Data were also collected on hut profiles, knowledge-attitudes-practices surveys, and household malaria prevalence . surveys. An. arabiensis and An. quadriannulatus were found in sympatry in Binga and Gokwe, and in addition, An. merus was found in Gokwe. Most species identifications were made using PCR; which was found to have 7.5% and 41.6% levels of error for An. arabiensis and An. quadriannulatus respectively, using the cytogenetic technique as benchmark. The pale band technique yielded > 80% correct identification for An. arabiensis but the extent of overlap in the pale band lengths between An. arabiensis and An. quadriannulatus renders the method unsuitable for distinguishing these two species. Inversions 2Rb and 3Ra were found floating in An. arabiensis, with 60% frequency in the former. The Wright's F statistic value of -0.0416 indicated an excess of heterozygotes, and a state of panmixis in the vector population. No significant differences were observed between 2Rb karyotypes in host choice. Human blood indices among indoor (0.82), exit trap (0.98) and outdoor resting (0.30) specimens suggested exophilic behaviour. This was corroborated by the high fed:gravid ratios of 6.8: 1 and 11.6: 1 in sprayed and non-sprayed dwellings respectively. This was worsened by a high feeder-survivor index (FSI) of 93 % among exit trap specimens. The susceptibility to deltamethrin coupled with residual efficacy nine weeks post-spray indicated the suitability of the insecticide. Rural dwellings were suitably built for spraying but had no mosquito proofing. Personal protective measures are hardly known; sleeping outdoors occurs in Siabuwa. While An. arabiensis bites humans indoors the partial exophily it exhibits is a threat to indoor residual insecticide spraying. An integrated malaria control approach is recommended. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1996.

This study investigated the effects of temperature and relative humidity (both controlled and natural) on the lifecyle and morphology of adults of members of the Anopheles gambiae complex in northern KwaZulu-Natal, South Africa. Laboratory investigations into the effects of simulated temperature and relative humidity regimes concentrated on seasonal differences in longevity, egg hatchability, reproductive potential and adult survivorship of An. arabiensis. Differences were found in the life table parameters when these mosquitoes were reared under conditions of seasonal temperature and relative humidity. During the cool season the lifespan and adult survivorship of mosquitoes were greater than those reared during the warm season. In summer, the egg hatchability and reproductive potential were greatest whereas in winter An. arabiensis underwent gonotrophic dissociation although these females were found to take blood meals readily. The influence of seasonal temperature and relative humidity on the body size of An. arabiensis was investigated, both in the laboratory and under field conditions. In both environments, these factors were found to significantly influence body size. In winter, there was a 13% increase in wing size compared to summer bred mosquitoes. A comparison of body size of An. arabiensis, An. merus and An. gambiae reared under laboratory conditions of seasonal temperature and relative humidity showed that the wing size of An. arabiensis was greater than that of An. merus and An. gambiae. The effect of temperature and relative humidity on morphological criteria used in species separation was also investigated. Seasonal differences in wing spot size were compared for An. arabiensis, An. merus and An. gambiae. From this investigation it was concluded that the pale and dark spots on the wing of Anopheles mosquitoes could not be used in species identification due to the large degree of inter-species overlap in the wing spot measurements. The measurement of the pale band at the junction of the 3rd and 4th tarsomere on the hind leg was also investigated for its use in species separation and were found to be useful within the An. gambiae complex. The implications of this study on the transmission and control of malaria are discussed with reference to the late season transmission during March to May that is characteristic of the region. / Thesis (Ph.D)-University of Natal, Pietermaritzburg, 1996.

South Africa is at the southern fringe of sub-Saharan African countries which persist in experiencing malaria transmission. The purpose of the study is to analyse the geographical and temporal patterns of malaria transmission from 2000 to 2011 using Bayesian geostatistical modelling in Limpopo Province, South Africa. Hereafter, develop malaria case data-driven spatio-temporal models to assess malaria transmission in Limpopo Province. Malaria case data was acquired from the South African Medical Research Council (MRC). Population data was acquired from AfriPopo; and Normalised Difference Vegetation Index (NDVI), Land Surface Temperature (LST) and Land Cover data were acquired from MODerate-resolution Imaging Spectro-radiometer (MODIS). Rainfall, Altitude and distance to water bodies’ data were acquired from African Data Dissemination Service (ADDS), United States Geological Survey (USGS) and Environmental Systems Research Institute (ESRI), respectively. Bayesian spatio-temporal incidence models were formulated for Gibbs variable selection and models were fitted using the best set of environmental factors. Modelbased predictions were obtained over a regular grid of 1 x 1km. spatial resolution covering the entire province and expressed as rates of per 1 000 inhabitants for the year 2010. To assess the performance of the predicted malaria incidence risk maps, the predictions and field observations were compared. The best set of environmental factors selected by variable selection was Altitude and the night temperature of two months before the case was reported. The environmental factors were then used for model fitting and all of the covariates were important on malaria risk. Predictions were done using all the environmental factors. The predictions showed that Vhembe and Mopani district municipalities have high malaria transmission as compared to other district municipalities in Limpopo Province. Assessment of predictive performance showed scatter plots with the coefficient of determination ( R² ). The values representing the statistical correlation represented by the coefficient of determination ( R² ) were 0.9798 (January), 0.8736 (February), 0.8152 (March), 0.8861 (April), 0.9949 (May), 0.3838 (June), 0.7794 (July), 0.9235 (September), 0.8966 (October), 0.9834 (November) and 0.8958 (December). August had two values reported and predicted which resulted in R² of 1. The numbers of the The produced malaria incidence maps can possibly be considered as one of the baselines for future malaria control programmes. The results highlighted the risk factors of malaria in Limpopo Province which are the most important characteristics of malaria transmission. / M.Sc. University of KwaZulu-Natal, Durban, 2013.