Thesis (M.Sc.(Med.))--University of the Witwatersrand, Faculty of Health Sciences, 2013.

A research report submitted to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science in Biology and Control of African Disease Vectors. Johannesburg, February 2012 / In Tanzania both Anopheles funestus and An. gambiae s.l. play a role as major vectors of malaria. Different species exist in the An. funestus group and the An. gambiae complex and play different roles in disease transmission. For malaria vector control programmes knowledge of vector species and their behaviour is key. A recent report on increased exophagy of An. funestus in southern rural Tanzania as a response to increased use of insecticide treated bed nets raised the question of whether there was misidentification of species and/or behavioural insecticide resistance playing a part. The present study used molecular tools to identify the species and determine human biting rates indoors and outdoors along with development and field evaluation of a new tool for sampling malaria vectors which is more effective than human landing catches. The results showed that the majority (96.2%) of the An. funestus group that were collected were An. funestus s.s. by PCR assay. Also, the exophagic proportion (45.9%) of An. funestus was lower than the endophagic proportion (54.1%), similar to other places in Africa, although in this study the difference was insignificant when untreated bed nets and treated bed nets were used. In addition, there was significant outdoor biting activity early in the evening that could lead to the malaria transmission cycle being unaffected by ITNs. The new trap, “Sticky Bucket Trap”, caught considerably fewer mosquitoes (14.2%) than that caught by human landing catches (85.8%), with statistical significance of P>0.05. These results imply that the sticky bucket trap is not a suitable substitute for human landing catches and some modifications are needed to make it more effective. Whereas indoor and outdoor proportions insignificant difference in feeding preference imply that both indoor and outdoor interventions should be used to control this vector.

Biotène® products have been developed with the intention of preventing tooth decay, plaque accumulation and oral infections in individuals with xerostomia (dry mouth). Not much is known about the effect of Biotène® chewing gums. Biotène® chewing gum contains host proteins. Due to these contents the manufacturer claims that Biotène® chewing gum is an “enzyme gum” that “boosts and strengthens the mouths natural defences”. The aim of this study was to investigate the effect of Biotène® chewing gum on saliva flow rates, saliva buffering capacity, plaque index, as well as salivary Streptococcus mutans and Lactobacilli counts, in healthy subjects with hyposalivation. One hundred and nine subjects with an age range of 18 to 23 years were screened for hyposalivation. Hyposalivation is a reduced salivary flow rate in a subject based on examination of the subject. Thirteen healthy subjects, who initially presented with hyposalivation, were included in the study. A baseline laboratory analysis of saliva was performed. Saliva was collected at rest and with masticatory stimulation, and measured. Resting saliva is saliva produced without any stimulation and can be obtained by allowing the subject to passively drool into a sputum jar. Stimulated saliva is produced as a result of stimulation of the salivary glands and may be obtained by allowing subject to chew inert rubber tubing while expectorating into a sputum jar. Buffering capacity was performed on both the saliva samples. Plaque index and DMFT was measured. Bacterial counts such as S. mutans and Lactobacilli counts were performed on the stimulated saliva. Subjects were given rubber tubing, xylitol chewing gum or Biotène® chewing gum to use for 2 weeks. A rubber tubing phase was introduced into the study to eliminate the effect of masticatory stimulation, which any chewing gum can provide. A xylitol-containing chewing gum (xylitol) phase was also introduced into the study in order to eliminate the effect of xylitol, as Biotène® chewing gum contains xylitol. A second laboratory analysis of saliva was performed. After a two weeks wash out period the second test product was given and the same procedure was repeated with the third product. The results showed that two weeks use of Biotène® chewing gum had no significant effect on the resting and stimulated saliva flows. It did not increase the buffering capacity of either the resting or stimulated saliva samples. Although it did not reduce the plaque index and S. mutans counts, it significantly reduced the Lactobacilli counts. Xylitol chewing gum, which was used as a control to eliminate the xylitol effect from the Biotène® chewing gum, significantly increased the stimulated saliva, reduced the plaque index and the salivary Lactobacilli count. Biotène® chewing gum which contains host proteins has no beneficial effects regarding saliva flow rate or against dental plaque and therefore against dental caries.

Hepatitis B virus (HBV) is hyperendemic to southern Africa and parts of Asia where it is a major cause of serious liver disease. Licensed antivirals for chronically infected individuals are only partially effective and approximately one million deaths occur annually as a result ofpersistent infection with the virus. Although RNA interference (RNAi) based gene silencingof HBV has been successfully demonstrated, difficulties with delivery of anti-HBV RNAieffectors remains an obstacle to their clinical use. Recombinant adenoviruses (Ads), amongst the most efficient hepatotropic gene vectors following systemic administration, have been successfully used to deliver expressed anti-HBV RNAi sequences. However, a drawback of Ad vectors is diminished efficacy and toxicity that results from stimulation of innate andadaptive immunity.To attenuate these effects we used polyethylene glycol (PEG) to modify first generation recombinant Ad (FG Ad) vectors that express an anti-HBV short hairpin (shRNA) sequence. Efficient hepatocyte transduction occurred and expressed shRNAs were processed to generate intended HBV-targeting guides. Inhibition of HBV replication was achieved after intravenous administration of PEGylated or native recombinant first generation Ads (FG Ads) to HBV transgenic mice. Circulating HBV viral particle equivalents (VPEs) remained low for 3 weeks and began to increase after 5 weeks. A second dose of PEGylated anti-HBV Ad caused a less sustained decrease in circulating VPEs, but no silencing after a second dose was observed in animals treated with unmodified vector. Release of inflammatory cytokines was elevated in animals receiving unmodified vectors and only a modest increase in monocyte chemotactic protein-1 (MCP-1) was observed in mice that received a second dose of PEG Abstract Ads. Also, polymer-conjugated vectors induced a weaker adaptive immune response and were less hepatotoxic than their unmodified counterparts. To address concerns about the transient nature of transgene expression by FG Ads resulting from immunostimulation, third generation helper-dependent (HD Ad) were utilised to delivered anti-HBV RNAi effectors. Seven days after intravenous administration of infectious HD Ads to HBV transgenic mice, 80-90% of hepatocytes were transduced and markers of HBV replication were decreased by approximately 95% which was sustained for 8 weeks. HD Ad-induced release of proinflammatory cytokines was minimal in preparations that were enriched with infectious particles. PEGylated HD Ad vectors caused similar anti- HBV effects and may be useful to evade interaction with vector-sequestrating receptors and further attenuate immunostimulation. Collectively these observations indicate that PEG modification of Ads and the use of HD Ads may have utility for delivery of therapeutic HBVsilencing sequences. Future work will focus on improving strategies to avoid immune detection and utilisation of HD Ad vectors for other HBV targeting sequences.

Thesis (M.Med.(Orthopaedic Surgery))--University of the Witwatersrand, Faculty of Health Sciences, 2013.

In order to employ the Sterile Insect Technique (SIT), biologically fit mosquitoes able to compete with their wild counterparts, suitable field sites for mass release of sterilized male mosquitoes, and appropriate methods of rearing genetic sex-separation (GSS) mosquito strains are required. The life history traits and biological fitness of four laboratory-reared, southern African Anopheles arabiensis strains were investigated. Despite being colonized at different times, the four strains demonstrated comparable levels of biological fitness. Three sites in the Kruger National Park were assessed as possible SIT field sites. Mosquito collections were conducted at each site during three summer months. Anopheles arabiensis was predominant at Malahlapanga during each collection period, establishing Malahlapanga as the most appropriate site for SIT field trials. A standard larval diet was shown to be appropriate for rearing An. arabiensis GSS. This work formed the laboratory basis for the evaluation of a SIT strategy for South Africa.

Diss. (sammanfattning) Uppsala : Univ., 2001. / Härtill 5 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 5 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 5 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 5 uppsatser.