No description available.

The biology of malaria parasites, Plasmodium spp., may be influenced by the presence of genetically distinct conspecific clones within a single infection, resulting in competition for host resources and transmission, and increased virulence for the vertebrate host. The extent of within host diversity, however, may be limited because overall clonal diversity could be reduced by the transmission biology of Plasmodium and variation in local prevalence. I examined clonal diversity of a natural malaria parasitehost association, P. mexicanum in its hosts, the western fence lizard, Sceloporus occidentalis, and sandflies, Lutzomyia vexator and L. stewarti, at a site in California ("Hopland"). Using microsatellite markers I characterized for the parasite, I examined (i) diversity within and among infections over time and space, (ii) transmission success of clones into both vector and lizard, (iii) the effects of clonal diversity on the parasite's infection dynamics and virulence for the lizard. From 1996 to 2006, clonal diversity varied both temporally and spatially, with slightly more multiclonal infections detected during years of high vs. low parasite prevalence (88% vs. 78% for sites with the highest prevalence at Hopland). Spatially, low prevalence sites (< 1% of lizards infected) had fewer multiclone infections (50%). Thus, even when prevalence drops over time, or at sites with chronically low prevalence, clonal diversity of the parasite remains high. Using natural and induced infections in the lizard, I found that multiclonal infections are no more infectious to vectors than single-clone infections, and almost all clones transfer successfully when the insect takes a blood meal. A competition experiment demonstrated that infections block new genotypes from entering a lizard host. Thus, multiclone infections are likely to be established when vectors feed on a complex infection and transmit those parasite clones to an uninfected lizard. The transmission biology of Plasmodium thus allows for the maintenance of genetic diversity in the parasite population. Finally, I examined the effects of multiclonality on the parasite's infection dynamics and virulence to the lizard host. Induced infections harboring a single or multiple clones had similar overall growth rates and maximal parasitemia, but multiclonal infections had significantly higher investment in gametocytes, suggesting competition for transmission. In addition, variation in parasite growth and density was greater for multiclonal infections, with approximately 1/3 displaying high replication rates and final parasitemia. Virulence measures indicated that weight change and proportion of immature erythrocytes was consistent for infections with 1, 2, 3 or > 3 clones, but the highly diverse infections had greater blood hemoglobin and glucose and more rapid clotting rates. Compared with the noninfected control lizards, highly diverse infections (3+) had higher blood glucose levels but similar hemoglobin levels. I have found that genetic diversity of the malaria parasite Plasmodium mexicanum varies both temporally and spatially, although overall diversity remains high. The transmission dynamics of the parasite maintains high genetic diversity within infections. Additionally, diversity within hosts plays a significant role in variation of infection dynamics and virulence.

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 fulfillment of the requirements for the award of a degree of Master of Science (med) in population based field Epidemiology. Johannesburg, South Africa, 2006.

eBioPhy is a diagnostic platform that uses biochemical and biophysical principles together with informatic and communication tools to probe the presence of pathogens in biological samples. The platform aims to bring real-time diagnostics to remote locations where health services are rare and it is based in two main principles: 1) The recognition of pathogens using fluorescently and chemically modified molecules, smart molecules. 2) Data collection and analysis using smartphone capabilities. / Proyecto financiado por el FINCyT y el Gobierno de Canadá (Grand Challenges Canada, Bold Idea with Bog impact). Se inicia inica en Octubre 2014 y finaliza en Abril 2016. La instituciones particpantes son Universidad Peruana de Ciencias Aplicadas - UPC y el Instituto de Investigación Nutricional - IIN. Lima, Perú

A research report submitted to the School of Public Health , University of Witwatersrand Johannesburg in partial fulfillment of the requirements for the degree of Masters of Science in Epidemiology and Biostatistics, November 2013 / Malaria in HIV-infected (HIV+) persons is associated with reduced immunity due to a decrease in CD4+ cells count and an increase in viral load, and immunity becomes more compromised in HIV-infected ART-naïve patients. However, the relationship between treatment of HIV infection with antiretroviral therapy (ART) and malaria among HIV coinfected individuals has not been widely reported in Africa, in particular amongst Rwandan women. In this study, the investigator examined malaria incidence and its associated potential risk factors in a cohort of HIV-uninfected, HIV-infected on ART and HIV-infected naïve Rwandan women. Method The data used in this research consists of 936 women enrolled in the Rwandan Women's Inter-association Study and Assessment (RWISA) study. Follow-up visits were carried out every 6 months for a period of 5 years. Incidence of malaria was considered as self-reported if it occurred during the 6 months prior to the study visit. Incidence rates (IRs) and Hazard ratios (HRs) with 95% CI were determined in HIV-uninfected, HIV-infected ART-naïve and HIV-infected on ART groups. Predictors of malaria incidence in these groups were estimated by Hazard ratios (HR, 95% CI) using Cox regression adjusted for potential confounders. Results Of the 936 women enrolled in the study (226 HIV-uninfected and 710 HIV-infected), almost 90% of the women reported malaria during the follow-up period. At the baseline visit, the median age of the participants was lower among HIV-infected women at 34 years ([IQR] 30- 39), compared to that of HIV-uninfected women at 43 years ([IQR] 34-49), P<0.01. In both groups of HIV-infected and HIV-uninfected women, a large number were widowed i.e. 49% vs. 42%, P<0.01 The HIV-infected women had lower educational status (67% vs. 57%, P<0.01) and lower employment opportunities (68% vs 72%, P=0.002) than HIV-uninfected women. Of the HIVuninfected women, 174 (77%) and of HIV-infected women 596 (84%) reported that they did not have enough food to eat. Malaria incidence was higher in HIV-infected ART-naïve women [adjusted HR= 1.2, 95% CI (1.01-1.36), P=0.03], when compared to HIV-infected women on ART. However, when malaria incidence was compared according to HIV status, HIV-infected women showed a significantly lower incidence when compared to their HIV-uninfected counterparts [adjusted HR= 0.8, 95% CI (0.69- 0.97), P=0.02]. The independent predictors of malaria incidence in the cohort were unemployment, lower level of education, age and season. Conclusion HIV-infected antiretroviral-naïve women in malaria-endemic areas are at higher risk of malaria than HIV-infected women on antiretroviral therapy. In countries where both diseases overlap, the indirect effect of HIV treatment with combination antiretroviral therapy could reduce malaria burden. These findings suggest that additional malaria prevention efforts should be aimed at the untreated HIV-infected population.

A thesis submitted to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science Johannesburg, 2014 / Southern African pyrethroid resistant and insecticide susceptible laboratory colonies of the malaria vector Anopheles funestus were investigated to further understand the phenotypic expression of pyrethroid resistance and to establish at which life stage resistance was selected. Pyrethroid resistance levels of larvae and adults were assessed at the larval and adult life stages using WHO larval and CDC bottle bioassays. Subsequent resistance levels were then assessed following targeted selections at each life stage. Tests for an association between cuticle thickness and pyrethroid resistance were based on cuticle thickness measurements using scanning electron microscope imaging of prepared tissue sections. It is concluded that pyrethroid resistance in southern African An. funestus is only expressed in the adult life stage, and that selection for this phenotype can only be achieved by exposing adults. It also concluded that pyrethroid tolerant or resistant females are likely to have thicker cuticles than less tolerant or susceptible females.

Anopheles funestus Giles is a major vector of malaria in Africa and pyrethroid resistance observed in this species has disrupted malaria control in southern Africa. Metabolic detoxification, based on the overproduction of cytochrome P450s, specifically CYP6P9 and CYP6P13, was identified as the principal resistance mechanism in both field and laboratory populations. This project aimed to characterize this resistance mechanism further, both on a molecular as well as a biochemical level. Biochemical analysis on total P450 activity levels revealed a 25.5-fold increase in the resistant strain compared to a pyrethroid susceptible strain. Analysis of the effect of pyrethroids on mRNA expression of three P450 genes showed that two of them (CYP6P9 and CYP6P13) as well as Cytochrome oxidase I (COI) was induced. HPLC analysis using a heterologously (recombinant) expressed CYP6P9 enzyme, showed that CYP6P9 was able to metabolize the pyrethroid permethrin and that it was catalytically efficient. Immunoblotting revealed no significant variation in CYP6P9 protein abundance between the different An. funestus colonies. Although an approximate molecular weight (≈Mr) of 58kDa was predicted for CYP6P9, two fragments were detected at ≈Mr 52,000 and ≈45,000. The smaller fragment was very likely a result of proteolytic degradation. Statistical analysis revealed there was no significant difference in CYP6P9 protein expression between strains or sexes. Although CYP6P9 mRNA is over-expressed it is important to assess the abundance of protein as well when elucidating whether a gene and its protein are important candidates in resistance. Differences in pyrethroid resistant or susceptible profiles of An. funestus colonies could be related to enzyme affinity for substrate and stability of CYP6P9 protein however; it is recommended that further studies need to be done before any conclusions can be drawn. CYP6P9 in An. funestus is a major candidate in conferring pyrethroid resistance and the pyrethroid resistant strain is able to metabolize the pyrethroid permethrin.

Malaria remains one of the most devastating vector-borne parasitic diseases in tropical and subtropical regions. Approximately 40% of the world’s population lives in malaria endemic areas mostly in developing countries. The estimated global incidence is about 225 million cases and 80% of these cases occur in sub-Saharan Africa. The approximated global deaths due to malaria every year is about 700,000 people and 90% occur in Africa. In South Africa, parts of Mpumalanga, Limpopo and KwaZulu-Natal have endemic malaria. The incidence of malaria in South Africa by province is 56, 2 cases per 100,000 population at risk; 31,1 cases per 100,000 population at risk and 3,3 cases per 100,000 population at risk for Mpumalanga; Limpopo and KwaZulu-Natal, respectively. Approximately 80% of the cases are imported from malaria endemic countries and diagnosed in the South African health facilities. It is therefore important that these cases are disentangled from local cases using environmental or climatic conditions as proxy measures especially in light of South Africa eradication goal. Methodology Secondary data used in this study were obtained from Mpumalanga Department of Health, South African Weather Services, Statistics South Africa and Global Climatic Research Units. These data were analysed from 2001 to 2010 to determine the correlation between surrounding climatic or environmental conditions and malaria incidence in Mpumalanga Province. The Pearson correlation was used to assess for significant correlations between malaria incidence and environmental or climatic conditions. A negative binomial regression model was used to identify and quantify factors significantly association with malaria risk. The Kulldorff spatial and space-time scan statistic was used to detect significant clustering of malaria cases in space and space-time. Results The incidence of malaria has decreased significantly since 2001 to 2010 in Mpumalanga Province. The decline has been observed from 1,304 cases per 100,000 population at risk in 2001 to less than 200 cases per 100,000 population at risk in 2010. About 96% of malaria cases were reported from Ehlanzeni District and less than 4% were reported from Gert Sibande and Nkangala Districts. The temperature, rainfall and humidity were statistically significant in all months from all years (p<0.05). The temperature, rainfall and humidity had a significant positive correlation with malaria cases. An excess of 1,752 and 104 malaria cases were detected in May and June over time when using weather stations data. When using remote sensed data, an excess of 1,131; 3,036; 4,009; 994 and 235 cases were observed from March, April, May, June and July, respectively. Discussion and conclusion The significant positive correlations between malaria cases and temperature, rainfall and humidity suggested that for an increase in each unit factor, malaria cases also increases. The excess number of cases observed especially during the winter season, suggested the likelihood of the importation of those cases. These results were in accordance with results from previous studies.

A Thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg for the Degree of Doctor of Philosophy / This thesis describes the characterisation of southern African isolates of Plasmodium falciparum according to isoenzyme type, antigen variants and drug sensitivity. Nineteen southern African isolates and a Gambian reference isolate were cultured in vitro in gassed tissue culture flasks. Polyacrylamide gel electrophoresis with use of 5 enzymes revealed little variation amongst the isolates and the frequencies of enzyme forms were similar to those of isolates from other parts of the world. Antigenic diversity was demonstrated using a panel of 9 monoclonal antibodies in the indirect fluorescent antibody test. The antigenic composition of 70% of isolates was markedly different to any obtained in other geographical areas. Both characterisation techniques revealed a mixture of parasite types in some isolates. However I the characteristics of most of these heterogeneous isolates were not stable with time in culture. Most isolates proved to be resistant to chloroquine in a 48-hour growth inhibition test. A wide range in Pyrimethamine susceptibilities was detected although most isolates exhibited a low level of resistance to this drug. In the radioisotope uptake assay, the halofantrine IC50 values obtained were comparable with those of West African isolates but were higher than the TC50s of south-East Asian isolates. All of the isolates resistant to chloroquine in the 48-hour test were resistant in the radioisotope assay. However, 1 isolate shown to be sensitive to chloroquine in the first test was found to be resistant in the 3Hhypoxanthine incorporation method. This was assumed to be the result of selection of resistant clones. Southern African isolates were shown to be fully susceptible to mefloquine, but had reduced susceptibility to quinine and sulphadoxine/ pyrimethaInine. Most isolates were sensitive to amodiaquine. A field study of 31 KwaZulu isolates of P. falciparum obtained in 1987 and 1988 showed 29 to be resistant to chloroquine in the 24-hour microtechnique, with the majority being highly resistant. Chloroquine resistance was confirmed in this area in a field study carried out in 1989 but in 1990 all 4 isolates tested were sensitive to the drug. In 1989, 12 out of 13 KwaZulu isolates were resistant to amodiaquine and most isolates showed reduced susceptibility to quinine and sulphadoxine/ pyrimethamine. / Andrew Chakane 2018