Rift Valley fever (RVF) is a disease endemic to Africa, which has recently spread outside of Africa to the Arabian Peninsula. Rift Valley fever virus (RVFV) is the causative agent of RVF and manifests as severe hepatitis, encephalitis and haemorrhagic fever, resulting in mortality in approximately 1% of human cases. RVFV also affects agriculture as it causes high mortality rates in young ruminants (>90% in new-born lambs) and is associated with high levels of abortions, which results in devastating economic losses. RVFV is a single-stranded RNA virus with a genome comprising of three separate genetic elements referred to as the Large (L), Medium (M) and Small (S) segments. The negative sense L segment encodes an RNA-dependent RNA polymerase (RdRp) while the M segment encodes two glycoproteins, Gn and Gc, and two non-structural proteins, NSm1 and NSm2. The glycoproteins are important for viral entry, genome packaging and mature virion formation as well as being the main antigen for the elicitation of neutralising antibodies by humoral immunity. The NSm proteins are required for mosquito vector transmission and preventing viral-induced apoptosis in host cells. The ambisense S segment encodes in the positive orientation a non-structural (NSs) gene, and in the negative orientation the nucleocapsid (N) gene. NSs is an important virulence factor involved in subverting host defences and the loss of NSs results in a highly attenuated RVFV infection. N is required for RNA synthesis and encapsidation of viral genomes. There are currently very few treatments in the early stages of development and vaccines for RVFV are not readily available. The overall lack of therapeutic strategies for RVFV urges novel therapeutic development such as RNA interference (RNAi). Endogenous RNAi is triggered by dsRNA and is involved in gene regulation through sequence specific suppression of target mRNA. Therapeutic RNAi exploits the RNAi pathway to facilitate targeted degradation of viral genes and has been applied effectively to the inhibition of a number of viruses that cause chronic and acute infections. There are fewer studies that have used RNAi to inhibit highly pathogenic viruses. Efficacy has been demonstrated against Ebola virus, Lassa virus and Dengue fever virus, which suggests applicability to the inhibition of RVFV. In this thesis, short hairpin RNAs (shRNAs) were generated to target the NSs, N and M genes of RVFV, which are important proteins in the viral life cycle. To determine the knockdown efficacy of the shRNAs, HEK293 cells were transiently transfected with the shRNAs and a vector expressing the respective shRNA gene target fused to a luciferase reporter. The reporter levels were assessed using a dual-luciferase assay and several shRNAs were selected for further characterisation as a result of effective target knockdown. Consequently, the shRNAs reduced the levels of expressed FLAG-tagged NSs, N and M encoded proteins, which were detected using western blot analysis. ShRNAs directed against NSs were shown to disrupt this protein’s function to result in alleviation of pathogenic properties. Specifically, NSs was shown to suppress the transcription levels of a luciferase reporter as well as prevent the activation of an IFN-β promoter. When the shRNAs were transiently transfected into HEK293 cells, they were able to reverse NSs-induced suppression in the reporter assays. Furthermore, NSs is cytotoxic as determined by observing cell morphology under transmitted light microscopy, which was quantified using a MTT viability assay and cells that subsequently received anti-NSs shRNAs had improved viability. This class of anti-pathogenic shRNAs should be able to down-regulate NSs in vivo and attenuate RVFV virulence. However, NSs is not essential for viral replication and as a result of the aggressive pathology of haemorrhagic RVF, essential structural genes were targeted to investigate shRNAs with anti-replicative properties. ShRNAs directed against N were transfected 24 hrs prior to infection with RVFV. The inhibition of viral replication was determined by collecting supernatant over 3 days and measuring the levels of N antigen using an ELISA. The shRNAs demonstrated effective suppression of RVFV but N antigen was detected at 72 hrs post-infection, which suggested that the shRNAs were overwhelmed by the virus. A series of shRNAs against M were subsequently tested and the anti-M shRNAs effectively suppressed viral replication in cultured cells over an extended 96 hr experiment, demonstrating that M is a good target for RNAi-mediated inhibition of RVFV. In this thesis, the potential of RNAi-based therapeutics against RVFV was demonstrated and these data contribute to the growing knowledge that RNAi should be developed further as a potential treatment for haemorrhagic fever viruses. Finally, some DNA viruses such as HBV form cellular reservoirs from which new virus can be produced and the DNA is resistant to RNAi-mediated inhibition. RVFV is an RNA virus with an acute infection, which makes it more susceptible to RNAi and an excellent target for this particular therapeutic modality.

Background The burden of non-communicable diseases (NCDs) is rapidly increasing globally, and particularly in Africa, where the health focus, until recently, has been on infectious diseases. The response to this growing burden of NCDs in Africa has been affected owing to a poor understanding of the burden of NCDs, and the relative lack of data and low level of research on NCDs in the continent. Recent estimates on the burden of NCDs in Africa have been mostly derived from modelling based on data from other countries imputed into African countries, and not usually based on data originating from Africa itself. In instances where few data were available, estimates have been characterized by extrapolation and over-modelling of the scarce data. It is therefore believed that underestimation of NCDs burden in many parts of Africa cannot be unexpected. With a gradual increase in average life expectancy across Africa, the region now experiencing the fastest rate of urbanization globally, and an increase adoption of unhealthy lifestyles, the burden of NCDs is expected to rise. This thesis will, therefore, be focussing on understanding the prevalence, and/or where there are available data, the incidence, of four major NCDs in Africa, which have contributed highly to the burden of NCDs, not only in Africa, but also globally. Methods I conducted a systematic search of the literature on three main databases (Medline, EMBASE and Global Health) for epidemiological studies on NCDs conducted in Africa. I retained and extracted data from original population-based (cohort or cross sectional), and/or health service records (hospital or registry-based studies) on prevalence and/or incidence rates of four major NCDs in Africa. These include: cardiovascular diseases (hypertension and stroke), diabetes, major cancer types (cervical, breast, prostate, ovary, oesophagus, bladder, Kaposi, liver, stomach, colorectal, lung and non-Hodgkin lymphoma), and chronic respiratory diseases (chronic obstructive pulmonary disease (COPD) and asthma). From extracted crude prevalence and incidence rates, a random effect meta-analysis was conducted and reported for each NCD. An epidemiological model was applied on all extracted data points. The fitted curve explaining the largest proportion of variance (best fit) from the model was further applied. The equation generated from the fitted curve was used to determine the prevalence and cases of the specific NCD in Africa at midpoints of the United Nations (UN) population 5-year age-group population estimates for Africa. Results From the literature search, studies on hypertension had the highest publication output at 7680, 92 of which were selected, spreading across 31 African countries. Cancer had 9762 publications and 39 were selected across 20 countries; diabetes had 3701 publications and 48 were selected across 28 countries; stroke had 1227 publications and 19 were selected across 10 countries; asthma had 790 publications and 45 were selected across 24 countries; and COPD had the lowest output with 243 publications and 13 were selected across 8 countries. From studies reporting prevalence rates, hypertension, with a total sample size of 197734, accounted for 130.2 million cases and a prevalence of 25.9% (23.5, 34.0) in Africa in 2010. This is followed by asthma, with a sample size of 187904, accounting for 58.2 million cases and a prevalence of 6.6% (2.4, 7.9); COPD, with a sample size of 24747, accounting for 26.3 million cases and a prevalence of 13.4% (9.4, 22.1); diabetes, with a sample size of 102517, accounting for 24.5 million cases and a prevalence of 4.0% (2.7, 6.4); and stroke, with a sample size of about 6.3 million, accounting for 1.94 million cases and a prevalence of 317.3 per 100000 population (314.0, 748.2). From studies reporting incidence rates, stroke accounted for 496 thousand new cases in Africa in 2010, with a prevalence of 81.3 per 100000 person years (13.2, 94.9). For the 12 cancer types reviewed, a total of 775 thousand new cases were estimated in Africa in 2010 from registry-based data covering a total population of about 33 million. Among women, cervical cancer and breast cancer had 129 thousand and 81 thousand new cases, with incidence rates of 28.2 (22.1, 34.3) and 17.7 (13.0, 22.4) per 100000 person years, respectively. Among men, prostate cancer and Kaposi sarcoma closely follows with 75 thousand and 74 thousand new cases, with incidence rates of 14.5 (10.9, 18.0) and 14.3 (11.9, 16.7) per 100000 person years, respectively. Conclusion This study suggests the prevalence rates of the four major NCDs reviewed (cardiovascular diseases (hypertension and stroke), diabetes, major cancer types, and chronic respiratory diseases (COPD and asthma) in Africa are high relative to global estimates. Due to the lack of data on many NCDs across the continent, there are still doubts on the true prevalence of these diseases relative to the current African population. There is need for improvement in health information system and overall data management, especially at country level in Africa. Governments of African nations, international organizations, experts and other stakeholders need to invest more on NCDs research, particularly mortality, risk factors, and health determinants to have evidenced-based facts on the drivers of this epidemic in the continent, and prompt better, effective and overall public health response to NCDs in Africa.

The southern African region is beset with numerous security concerns: pervasive poverty, deepening inequality, starvation, contamination of essential natural resources, violent crime and state oppression. However, the most vital of the region’s security concerns in the 21st century is the spread of infectious disease. The region shoulders a disproportionate amount of the continent’s infectious disease burden, with diseases such as HIV/AIDS, tuberculosis and malaria claiming more lives every year than any other factor. The nature of these diseases and their propensity to spread, coupled with inadequate regional public health structures pose a significant threat to regional security and stability. The study asserts that southern Africa’s security concerns are most appropriately characterised under the paradigm of Human Security. It further asserts that if such vital threats to human security are not adequately managed they have the ability to permeate across state borders, spelling numerous negative ramifications for the region. To this end, the study details the public health crisis in Zimbabwe and its effects on regional security and stability in southern Africa. An enduring political and economic collapse in Zimbabwe led to the dramatic deterioration of its public health sector, the concomitant mass migration of Zimbabwean nationals across the region presented a unique and complex challenge to the Southern African Development Community (SADC) and its member states. As the premier regional governance institution, SADC has failed to adequately mobilise its structures and member states to respond to the challenges resulting from the public health crisis in Zimbabwe. The study explores the factors accounting for this regional inertia, and asserts that while infectious diseases are at present the most vital of the human security threats, similar threats to human security have the potential to affect the region if SADC fails to recognise and prioritise threats to human security as legitimate regional security concerns.