Browsing by Author "Hammond-Aryee, Kenneth Nii Ofei"

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    Seroprevalence and molecular epidemiology of Toxoplasma gondii in the Western Cape of South Africa
    (Stellenbosch : Stellenbosch University, 2016-12) Hammond-Aryee, Kenneth Nii Ofei; Van Helden, Paul; Esser, Monika; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Biomedical Sciences: Molecular Biology and Human Genetics.
    ENGLISH SUMMARY: Toxoplasmosis is a disease caused by the obligate intracellular parasite Toxoplasma gondii and is one of the most widely occurring infections known to man, causing disease in almost all mammals and warm-blooded birds. Toxoplasma gondii is an opportunistic pathogen, taking advantage of weakened immune systems to cause disease. The disease toxoplasmosis is known to occur in both active and latent or chronic forms. The latent or chronic form of toxoplasmosis is known to be the most common latent infection in man. Currently, the effects of the latent or chronic form of toxoplasmosis is neither properly studied nor understood. In Africa, there is currently no systematic monitoring or reporting of toxoplasmosis incidence or T. gondii prevalence and this leaves health systems at a disadvantage. The United States Centre for disease Control and Prevention (CDC) currently classify toxoplasmosis as a neglected tropical infection. In this series of research projects, the seroprevalence of T. gondii antibodies and the risk factors to infection were investigated. Following that, the molecular epidemiology and population structure of the pathogen was also investigated. The investigations were conducted in opportunistically selected human and animal populations within the Western Cape Province of South Africa. The data obtained was analyzed from a “One World One Health” perspective and conclusions were then documented. The selected human populations were, a cohort of human immunodeficiency virus (HIV) positive and human immunodeficiency virus (HIV) negative post parturient women and their HIV exposed and uninfected (HEU) and HIV unexposed and uninfected (HUU) infants, and a cohort of HIV positive and HIV negative male and female patients presenting with a clinical diagnosis of uveitis at the Tygerberg academic hospital opthalmology clinic. The selected animal populations were a population of feral cats in the greater Cape Town metropole, a population of free ranging sheep on a single farm in Bredasdorp and a population of free ranging caracals in the Cape peninsula region. Toxoplasma gondii seroprevalence was 23.3% in the cohort of post parturient women, whilst the seroprevalence in the infant cohort was 1.02%. The seroprevalence was 24.7% in the cohort of patients presenting with ocular infections. The seroprevalence was not associated with HIV status but was associated with the consumption of unwashed fruits and vegetables. The similarity between the seroprevalence in the post parturient cohort and the ocular cohort points to the lack of regional differences in seroprevalence rates, whilst the low seroprevalence in the infant cohort implies a low rate of congenital toxoplasmosis in the study area and this comforms to what is observed in other parts of Africa, Europe and North America. Seroprevalence was extremely high in the felid populations investigated (Feral cats - 37.1% and Caracals- 69.6%). These justifies considerable attention since these felids were free ranging and therefore have access to domestic human and animal populations. The seroprevalence in the sheep flock was also higher at 8.0% than the five point six percent (5.6%) reported in earlier studies in Cape Town. Current research has established that T. gondii genotypes vary in their geographic distribution, with certain genotypes being more predominant in certain geographic areas than others. To establish the genotypes of T. gondii present in our selected geographic area, we investigated the molecular epidemiology of the pathogen. The molecular epidemiology investigations revealed a predominance of Type II genotypes in both human and animal samples. A Type III genotype was detected in human but not in animal samples. Atypical genotypes were also identified in both human and animal samples. The observed population structure is similar to that of South America and other parts of Africa but differs from that observed in Europe and North America. We have demonstrated the presence of T. gondii as well as its active transmission within selected human and animal populations in the Cape Town metropole of South Africa. The presence of atypical T. gondii genotypes was also demonstrated. The observed seroprevalence rates investigated in this study implies that more attention needs to be paid to the disease as it could have implications for female reproductive health, infant to adolescent ocular health as well as overall economic losses due to an increase in disease burden in humans (reported as disability-adjusted life years) and for agriculture.
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    Toxoplasma gondii seroprevalence studies on humans and animals in Africa
    (Medpharm Publications, 2014) Hammond-Aryee, Kenneth Nii Ofei; Esser, Monika; Van Helden, Paul D.
    Background: Toxoplasmosis is a disease caused by Toxoplasma gondii, which can infect nearly all mammalian and avian species. Approximately 25% of the global human population is thought to be infected. Interest in toxoplasmosis has surged since it was discovered that with the onset of acquired immune deficiency syndrome, acute toxoplasmosis could induce cranial calcification. The ensuing encephalitis can be fatal. The African human immunodeficiency virus (HIV) epidemic, increasing levels of other immunosuppressive infections (such as tuberculosis), poor sanitation practices and lack of monitoring of at-risk populations point to a predicament that may be underrated. Objective: The objective was to review the available body of research on the seroepidemiology of T. gondii in Africa, in order to establish existing prevalence trends and to draw attention to available information on the pathogen in Africa. Method: The National Center for Biotechnology Information, Google Scholar and ToxoDB databases were searched for peer-reviewed articles that focus specifically on seroprevalence studies of T. gondii in Africa up until the 2012 year end. Results: Seroprevalence rates on the continent are high in humans and animals. There is a geographical trend of decreasing seroprevalence from the northern to the southern, and from the western to the eastern, regions of the continent. Most seroprevalence studies on humans were reported between 1981 and 2000. Conclusion: There is a need for further and more consolidated information on the prevalence of T. gondii in Africa, in order to address morbidity and mortality from opportunistic but treatable diseases, such as toxoplasmosis in the ongoing HIV pandemic, and to improve the lives of the African population.