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Search Results: 1 - 10 of 325141 matches for " S. Mushayabasa "
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Impact of Vaccines on Controlling Typhoid Fever in Kassena-Nankana District of Upper East Region of Ghana: Insights from a Mathematical Model
S. Mushayabasa
Journal of Modern Mathematics and Statistics , 2012, DOI: 10.3923/jmmstat.2011.54.59
Abstract: Vaccination is an important prevention and control measure for the spread of typhoid fever. In this study, we develop a simple mathematical model to explore the impact of vaccination on the transmission dynamics of typhoid fever in Kassena-Nankana district of Upper East region of Ghana. Analytical results of the model show that the quantities Rv and R0 which represent the vaccine-induced reproduction number and the no vaccine induced reproduction number, respectively provide threshold conditions that determine the prevalence of typhoid fever in a community. These threshold conditions can be used to gain important insights into the impact of vaccination on controlling typhoid fever. Numerical results have been provided to illustrate the analytical findings.
Modelling the Transmission Dynamics of Pox-like Infections
Bhunu CP,Mushayabasa S
IAENG International Journal of Applied Mathematics , 2011,
Abstract:
Modeling Schistosomiasis and HIV/AIDS Codynamics
S. Mushayabasa,C. P. Bhunu
Computational and Mathematical Methods in Medicine , 2011, DOI: 10.1155/2011/846174
Abstract: We formulate a mathematical model for the cointeraction of schistosomiasis and HIV/AIDS in order to assess their synergistic relationship in the presence of therapeutic measures. Comprehensive mathematical techniques are used to analyze the model steady states. The disease-free equilibrium is shown to be locally asymptotically stable when the associated disease threshold parameter known as the basic reproduction number for the model is less than unity. Centre manifold theory is used to show that the schistosomiasis-only and HIV/AIDS-only endemic equilibria are locally asymptotically stable when the associated reproduction numbers are greater than unity. The impact of schistosomiasis and its treatment on the dynamics of HIV/AIDS is also investigated. To illustrate the analytical results, numerical simulations using a set of reasonable parameter values are provided, and the results suggest that schistosomiasis treatment will always have a positive impact on the control of HIV/AIDS. 1. Introduction Schistosomiasis, also known as bilharzia after Theodor Bilharz who first identified the parasite in Egypt in 1851, is a disease caused by blood flukes [1]. It affects millions of people worldwide, especially in South America, the Middle East, and Southeast Asia where it remains a public health problem and poses a threat to 600 million people in more than 76 countries [1]. The disease is often associated with water resource development projects, such as dams and irrigation schemes, where the snail intermediate hosts of the parasite breed [2]. Human schistosomiasis (which has a relatively low mortality rate, but a high morbidity rate) is a family of diseases primarily caused by three species of the genus Schistosoma or flat worms. The adult worms inhabit the blood vessels lining either the intestine or bladder, depending on the species of the worm [3]. The highest number of human schistosomiasis infections is caused by S. haematobium, which has a predilection for the blood vessels around the bladder and causes urinary disease [4]. Schistosomiasis is the second most prevalent neglected tropical diseases after hookworm (192 million cases), accounting for 93% of the world's number of cases and possibly associated with increased horizontal transmission of HIV/AIDS [5]. On the other hand, the number of people living with HIV worldwide continued to grow in 2008, reaching an estimated 33.4 million, which is more than 20% higher than the number in 2000, and the prevalence was roughly threefold higher than in 1990 [6]. The HIV virus, by holding the immune system hostage,
Modeling HIV Transmission Dynamics among Male prisoners in Sub-Saharan Africa
S. Mushayabasa,C. P. Bhunu
IAENG International Journal of Applied Mathematics , 2011,
Abstract:
Impact of Intravenous Drug Use on HIV/AIDS among Women Prisoners: A Mathematical Modelling Approach
C. P. Bhunu,S. Mushayabasa
ISRN Computational Biology , 2013, DOI: 10.1155/2013/718039
Abstract: Intravenous drug use and tattooing remain one of the major routes of HIV/AIDS transmission among prisoners. We formulate and analyze a deterministic model for the role of intravenous drug use in HIV/AIDS transmission among women prisoners. With the aid of the Centre Manifold theory, the endemic equilibrium is shown to be locally asymptotically stable when the corresponding reproduction number is greater than unity. Analysis of the reproduction number and numerical simulations suggest that an increase in intravenous drug use among women prisoners as they fail to cope with prison settings fuels the HIV/AIDS epidemic in women prisoners. Failure to control HIV/AIDS among female prisoners may be a time bomb to their communities upon their release. Thus, it may be best to consider free needle/syringe exchange and drug substitution treatment programmes in women prisons as well as considering open prison systems for less serious crimes. 1. Introduction The imprisonment of large numbers of drug addicts has the potential to create environments within which social networks that enhance the transmission of infectious diseases form [1–6]. Prisons are high-risk settings for HIV transmission. However, HIV prevention and treatment are not adequately developed and implemented to respond to HIV in prisons [7]. There is evidence to show that health programmes for the particular needs of imprisoned drug users are not enough in USA and Canada [8, 9]. In Russia, a study of intravenous drug users demonstrated the critical role of prisons in the transmission of HIV through high levels of needle (syringes) sharing among the imprisoned [10]. In many jurisdictions, a larger proportion of women than men are in prison for drug related offences [11]. Drug use and HIV infection are more prevalent among women in prison than among imprisoned men [12]. Women in prisons are more susceptible to self-harm through unsafe tattooing and injecting drug use [13]. In the absence of sterile injecting equipment, women, like men, will inject with used needles or home-made syringes, Doll [14] Like men, women get tattooed in prison [14]. In the absence of proper precautions and access to safe equipment tattooing can be a high-risk activity for the transmission of HIV [15, 16]. Women constitute a very small proportion of the total prison population, globally accounting 5% of the total prison population [15]. Women prisoners present specific challenges for correctional authorities as most of the existing prison facilities for women inmates have all being developed for men, who have historically
Transmission Dynamics of Lymphatic Filariasis: A Mathematical Approach
C. P. Bhunu,S. Mushayabasa
ISRN Biomathematics , 2012, DOI: 10.5402/2012/930130
Abstract: An epidemiological model for the spread of lymphatic filariasis, a mosquito-borne infection, is developed and analysed. The epidemic thresholds known as the reproduction number and equilibria for the model are determined and stabilities analysed. Results from the analysis of the reproduction number suggest that treatment will somehow contribute to a reduction in lymphatic filariasis cases, but what it does not show is the magnitude of the reduction, a part answered by the numerical simulations. Numerical simulations show that even when all lymphatic filariasis cases displaying elephantiasis symptoms are put on treatment it will not be able to eradicate the disease. This result suggests that effective control of lymphatic filariasis may lie in treatment for those displaying symptoms as well as chemoprophylaxis for the exposed. 1. Introduction Lymphatic filariasis, a debilitating disease, is one of the most prevalent and yet one of the most neglected tropical diseases with serious economic and social consequences [1, 2]. Lymphatic filariasis affects women, men and children of all ages. It is a mosquito-borne disease caused by tissue-dwelling nematodes of Brugia malayi, Brugia timori, and Wuchereria bancrofti species [1, 3] and is estimated to affect about 120 million people worldwide [4–6]. Wuchereria bancrofti is responsible for 90% of the cases and is found throughout the tropical and subtropical areas of the world; Brugia malayi is confined to southeast and eastern Asia; Brugia timori is found only in Timor and its adjacent islands [7]. Infection leads to lymphedema, a buildup of fluid due to impaired function of the lymph vessels, in only a small proportion people, even in areas of intense transmission [8], as most people with long-term infections are clinically asymptomatic. Recurrent bacterial infections in some lymphedema patients lead to elephantiasis [9]. Filarial parasites are a major cause of morbidity and therefore hinder socioeconomic growth in parts of Asia, Africa, and the Western Pacific [1, 10]. Despite improved knowledge of pathology of lymphatic filariasis and existence of the drugs diethylcarbamazine and albendazole necessary to treat lymphatic filariasis, it continues to be a major public health problem in tropical and subtropical countries. Lymphatic filariasis is more common in regions that have a higher incidence of poverty [11] making it a disease of the poor and serves as an indicator of underdevelopment [1]. Surveys in Ghana have indicated that bancroftian filariasis is present in most parts of the country with considerable
Assessing the Impact of Drug Resistance on the Transmission Dynamics of Typhoid Fever
S. Mushayabasa,C. P. Bhunu,E. T. Ngarakana-Gwasira
Computational Biology Journal , 2013, DOI: 10.1155/2013/303645
Abstract: Typhoid fever continues to be a major public health problem in the developing world. Antibiotic therapy has been the main stay of treating typhoid fever for decades. The emergence of drug-resistant typhoid strain in the last two decades has been a major problem in tackling this scourge. A mathematical model for investigating the impact of drug resistance on the transmission dynamics of typhoid fever is developed. The reproductive number for the model has been computed. Numerical results in this study suggest that when a typhoid outbreak occurs with more drug-sensitive cases than drug-resistant cases, then it may take 10–15 months for symptomatic drug-resistant cases to outnumber all typhoid cases, and it may take an average of 15–20 months for nonsymptomatic drug-resistant cases to outnumber all drug-sensitive cases. 1. Introduction Typhoid fever is caused by Salmonella enterica serovar Typhi (S. Typhi), a gram-negative bacterium [1–3]. It continues to be a global public health problem with over 21.6 million cases and at least 250,000 deaths occurring annually [4–6]. Almost 80% of the cases and deaths are in Asia; the rest occur mainly in Africa and Latin America [3, 7]. In developing countries such as India, the disease occurs with an incidence ranging from 102 to 2,219 per 100,000 of the population [3, 8]. Several studies in areas of endemicity and outbreaks have shown that about one-quarter to one-third of pediatric typhoid fever cases are under five years of age, and that between 6% and 21% are under two years of age [9]. Varied presentations of typhoid fever are known in the pediatric age group, such as septicemia in neonates, as diarrhoea in infants, and as lower respiratory tract infections in older children [10–12]. Typical presentation in older children includes splenic abscess, liver abscess, cerebellar ataxia, meningitis, cholecystitis, chorea, palatal palsy, osteomyelitis, peritonitis, aphasia, and even psychosis [13–16]. Due to these varied and typical presentations, it is common for typhoid fever in children to be diagnosed late or even remain unrecognised. Also, no vaccine against typhoid fever is available commercially for children under two years of age [14]. To complicate matters further, in the last two decades, multidrug-resistant (MDR) S. Typhi strains have emerged and spread worldwide, resulting in high rates of morbidity and mortality [14, 15, 17]. Typhoid drug resistance emerged first in the UK within 2 years of the successful use of chloramphenicol on typhoid treatment [18, 19]. Subsequently, isolates carrying transferable
Assessing the Impact of Vaccination on Controlling the Spread of Human Scabies
C. P. Bhunu,S. Mushayabasa,T. G. Monera
ISRN Computational Biology , 2013, DOI: 10.1155/2013/362973
Abstract: Scabies is among the infestations almost forgotten due to its association with poor communities. We formulate a deterministic model to assess the possible impact vaccination will have on scabies control. The Descartes’s rule of signs is used to show the nature of the endemic equilibria. Analysis of the reproduction number and numerical simulations suggest that vaccination in addition to treatment will help greatly in reducing the spread of scabies infestation. This suggests there is a strong need for researchers to come up with a possible vaccine in that order to effectively control scabies especially among the disadvantaged communities. 1. Introduction Scabies is a highly contagious skin infestation caused by skin infestation with the mite Sarcoptes scabiei and is spread by direct contact. Its common name is the “itch mite” derived from the severe pruritis it causes [1]. The female mite burrows the skin and lays its eggs which hatch into larvae within 2-3 days [2]. The larvae then burrow to reach the skin surface, then dig burrows where they pass through two further developmental stages (protonymphs and tritonymphs) before moulting into either male or female mites. As a result a result, S-shaped trails accompanied by small insect bites cover infested areas. It is only less than 1% of the eggs laid by female mites that develop into adult mites [3]. Following infection, the mite population increases rapidly up to 25 adult mites after 50 days and upto 500 mites by 100 days [3], and thereafter rapid decrease may be due to scratching as well as host immune's response. However, 10–12 mites are enough to cause a burden in a host [1]. It is estimated that, despite the availability of effective treatment, over 300 million people in the world are scabies infested [6]. Scabies is well described in the historical record with descriptions evident in ancient texts from China, India and the Middle East [7]. Scabies was also a scourge in London during the First World War upto 1920 [8]. Scabies can be treated with any of the following medications: permethrin (one of the most effective and most expensive), ivermectin (an oral medicine shown in clinical studies to be effective against scabies but not recommended for children), lindane (effective though there are concerns that it can cause neurotoxicity), benzyl benzoate, crotamiton, malathion, and sulphur preparations. Due to low cost, benzyl-benzoate and sulphur ointments are commonly used in developing countries. In general the prevalence of scabies is not well documented especially in Africa [2]. Scabies infestations
A Mathematical Model for Assessing the Impact of Intravenous Drug Misuse on the Dynamics of HIV and HCV within Correctional Institutions
S. Mushayabasa,Claver P. Bhunu,Alexander G. R. Stewart
ISRN Biomathematics , 2012, DOI: 10.5402/2012/919502
Abstract: Unsafe injecting practices, blood exchange, the use of nonsterile needles, and other cutting instruments for tattooing are common in correctional institutions, resulting in a number of blood transmitted infections. A mathematical model for assessing the dynamics of HCV and HIV coinfection within correctional institutions is proposed and comprehensively analyzed. The HCV-only and HIV-only submodels are first considered. Analytical expressions for the threshold parameter in each submodel and the cointeraction are derived. Global dynamics of this coinfection shows that whenever the threshold parameter for the respective submodels and the coinfection model is less than unity, then the epidemics die out, the reverse condition implies disease persistence within correctional institutions. Numerical simulations using a set of plausible parameter values are provided to support analytical findings. 1. Introduction Prior studies suggests that prevalence of both human immunodeficiency virus (HIV) and hepatitis C virus (HCV) infections is known to be higher among incarcerated populations than the general population, since a high proportion of incarcerated individuals originate from high-risk environments and have high-risk behaviors, especially drug use [1–6]. HCV and HIV coinfections represent a public health problem of growing importance; because of similar modes of spread, many people are coinfected with HCV and HIV or HCV and HBV and in some cases with all three viruses at the same time [5]. In particular, HCV/HIV coinfections are common and are known as “twin epidemics” [6, 7]. Both HIV and HIV are blood born RNA (ribonucleic acid) viruses that replicate rapidly. Unsafe injecting practices, blood exchange and the use of non-sterile needles are the most efficient means of transmitting both viruses [6, 8]. Correctional institutions host a disproportionately high prevalence of HCV infection and coinfections. The prevalence of HCV among prisoners approaches 57.5% and far exceeds that of HIV in prison [9, 10]. Transmission of these infections is believed to be a rare consequence of blood or body fluid exposures in the prison. However, if transmission does occur, the consequences are permanent and potentially fatal [5–7]. Coinfection with the two viruses (HCV/HIV) is associated with an accelerated course of hepatitis C disease [5–7]. Prison populations constitute a very high-risk group; they have high levels of HCV infection and HIV or HBV coinfection [11, 12]. HCV positive inmates are at exceptional risk for coinfection with HIV because of the association of
On the Role of Optimal Counseling and Antiviral Therapy on Controlling HCV among Intravenous Drug Misusers
Steady Mushayabasa
Journal of Computational Medicine , 2014, DOI: 10.1155/2014/347827
Abstract: Hepatitis C virus (HCV) remains a major health challenge despite the availability of highly effective antiviral drugs. Prior studies suggest that many physicians are reluctant to treat intravenous drug misusers due to low levels of treatment adherence associated with intravenous drug misusers. HCV treatment guidelines and recommendations stipulate that HCV patients in treatment should abstain from intravenous drug misuse activities in order to reduce the likelihood of treatment failure, drug resistance, reinfection, superinfection, or mixed infection. In this paper, a mathematical model for exploring the transmission dynamics of HCV among intravenous drug misusers is proposed. The model incorporates essential characteristics of intravenous drug misusers such as relapse and nonadherence to treatment guidelines. With the aid of optimal control theory we assess the effects of time dependent HCV screening and treatment. Results from this study provide a framework for designing the appropriate strategies on controlling the long-term dynamics of HCV among intravenous drug users. 1. Introduction Intravenous drug misuse continues to claim a large proportion of new hepatitis C virus (HCV) infections worldwide [1]. Despite advancements in the management of HCV and suggestions that treatment of recently acquired HCV can lead to virological response rate of up to 98%, low rates of treatment among HCV patients continue to be observed [2]. Apart from low treatment rates, nonadherence to HCV treatment guidelines and recommendations has been observed as one of the major challenges on effective HCV control among intravenous drug misusers [2, 3]. Adherence in the context of HCV treatment includes the patient’s adherence to both the medication regimen and the overall medical plan [3]. Nonadherence to HCV treatment may be associated with a number of reasons among the following: higher pill burden and lengthy treatment, limited provider experience, lack of social support, and presence of cirrhosis [4]. This study aims to evaluate the effects of time dependent HCV screening and treatment. The application of optimal control theory on gaining insights into the long-term dynamics of HCV has been an interesting topic for a couple of researchers (e.g., see [5–8] and the references therein). In 2011, Martin et al. [5] developed a mathematical model to assess the impact of time dependent control on HCV antiviral treatment. Their work revealed, among others, that, with a fixed annual budget, greater impact on HCV control (measured by infections averted or prevalence reductions) and
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