David Nganwa

The correlation between alcohol consumption and risky sexual behaviours among people living with HIV/AIDS

The objectives of this study were to determine if significant correlation exists between drinking any alcoholic beverage and risky sex among 326 AIDS patients. Participants completed anonymous surveys. The result of the regression and Pearson correlation analyses revealed a significant positive correlation between drinking alcohol before sex and frequency of condom use (p<0.0001). The number of sex partners respondents reported was also correlated with the frequency of alcohol use (p = 0.003). The result shows that the quantity of alcohol consumption was correlated with two indicators of risky sex: having multiple sexual partners (p<0.0001) and having sexual intercourse without a condom (p<0.001). Interventions are that integrate HIV risk reduction with alcohol risk reduction is very useful to minimize the risk of new HIV infections and/or manage existing infections.

A risk-assessment model for foot and mouth disease (FMD) virus introduction through deboned beef importation.

We present a risk-assessment model to assess the risk of introduction of foot and mouth disease (FMD) virus associated with deboned beef importation. The model was developed in accordance with the risk-reduction procedures proposed by the European Community for meat importation. The risk reduction procedures include farm-level inspection, ante-mortem inspection, post-mortem inspection, chilling and deboning. The risk assessment was based on the prevalence of FMD-infected cattle in herds as well as the prevalence of infected herds in the exporting country. Computer simulations were carried out to evaluate the probability of FMD virus introduction by importing 100 tons of deboned beef in relation to FMD prevalence, number of cattle selected from each herd, and sample sizes in ante-mortem and post-mortem inspections. The effects of the risk-reduction procedures on the probability of FMD virus introduction were examined.

Public health considerations in human consumption of wild game.

Abstract: The role of a few microorganisms, like Brucella and Mycobacterium and certain parasites of food animals, in causing human disease has been recognized for a hundred years. By the 1990s, other microorganisms derived from food animals were recognized as contributing to human illness. Handling and/or consumption of wild game may result in human exposure to novel microorganisms; these unrecognized or unknown agents or diseases in wild species may cross into humans and cause “new” diseases with which we are not familiar.

Integration of temporal and spatial models for examining the epidemiology of African trypansomiasis

Abstract A stochastic model was first developed to study the spatial dispersal of tsetse fly population, and subsequently integrated with a time oriented epidemiologic model. Such an integrated model was needed to understand better the epidemiology of cattle trypanosomiasis. Pre-existing data were used to determine the distributions of the random variables involved in the model. We used the model to assess several alternatives of preventing the spatial progression of trypanosomiasis. We address the following question: what size of protective barrier is required to prevent the spatial progression of trypanosomiasis? The vector control alternatives considered in this study included insecticide applications, vegetation clearing, wild animal depopulation, use of tsetse traps, and combinations of the above methods within a protective barrier. Simulation results indicated that a protective barrier, about 1000 m wide, was effective in stopping the spatial spread of cattle trypanosomiasis.

The risk of introduction of equine infectious anemia virus into USA via cloned horse embryos imported from Canada

Deriving horse oocytes in the USA is hampered by the lack of abattoirs processing horse carcasses which could provide abundant quantities of ovaries from slaughtered mares. Therefore, several cloning industries in the USA are attempting to import cloned horse embryos from Canada. Like any agricultural commodity, cloned embryos pose a risk of introduction of exotic animal diseases into the importing country. Under such circumstances, risk assessment could provide an objective, transparent, and internationally accepted means for evaluating the risk. This quantitative risk assessment (QRA) was initiated to determine the risk of introduction of Equine infectious anemia virus (EIAV) into the USA via cloned horse embryos imported from Canada. In assessing the risk, a structured knowledge base regarding cloning in relation to Equine infectious anemia (EIA) was first developed. Based on the knowledge base, a scenario tree was developed to determine conditions (with mathematical probabilities) that could lead to the introduction and maintenance of EIAV along the cloning pathway. Parameters for the occurrence of the event at each node were estimated using published literature. Using @Risk software and setting Monte Carlo simulation at 50,000 iterations, the probability of importing an EIAV-infected cloned horse embryo was 1.8 × 10(-9) (R = 1.5 × 10(-12) to 2.9 × 10(-8)). Taking into account the current protocol for equine cloning and assuming the yield of 5 to 30 clones per year, the possible number of EIAV-infected cloned horse embryos ranged from 2.0 × 10(-10) to 9.1 × 10(-5) (Mean = 1.4×10(-6)) per year. Consequently, it would take up to 1.5 × 10(7) (R = 1.6 × 10(4) to 5.1 × 10(10)) years for EIAV to be introduced into the USA. Based on the knowledge base and our critical pathway analysis, the biological plausibility of introducing EIAV into USA via cloned horse embryos imported from Canada is extremely low.

A comparative study of substance use before and after establishing HIV infection status among people living with HIV/AIDS

Objective: To determine if significant differences exist in substance use among people living with HIV/AIDS (PLWHA) before and after establishing their HIV infection status. Method: The study participants are HIV positive clients of a community based HIV/AIDS outreach facility located in Montgomery, Alabama. The questionnaire includes demographics, substance use and risky sexual behaviors pertaining to HIV transmission. Each participant completed an anonymous questionnaire. A total of 341 questionnaires were distributed and 326 were fully completed and returned, representing a response rate of 96%. Results: Findings revealed a statistically significant difference in alcohol consumption before sex among PLWHA before and after establishing their HIV infection status (p = .001). No significant differences were observed among participants who reported as having used drugs intravenously (p = .89), and among those sharing the same syringe/needle with another person (p = .87) before and after establishing their HIV infection status. Conclusion: There is continued substance use and alcohol consumption before sex among PLWHA after establishing their HIV status despite clear evidence of such risky behaviors that could lead to an increase in exposure to HIV.

Epidemiologic modelling of HIV and CD4 cellular/molecular population dynamics

Computational models can facilitate the understanding of complex biomedical systems such as in HIV/AIDS. Untangling the dynamics between HIV and CD4+ cellular populations and molecular interactions can be used to investigate the effective points of interventions in the HIV life cycle. With that in mind, we have developed a state transition systems dynamics and stochastic model that can be used to examine various alternatives for the control and treatment of HIV/AIDS. The specific objectives of our study were to use a cellular/molecular model to study optimal chemotherapies for reducing the HIV viral load and to use the model to study the pattern of mutant viral populations and resistance to drug therapies. The model considers major state variables (uninfected CD4+ lymphocytes, infected CD4+ cells, replicated virions) along with their respective state transition rates (viz. CD4+ replacement rate, infection rate, replication rate, depletion rate). The state transitions are represented by ordinary differential equations. The systems dynamics model was used for a variety of computational experimentations to evaluate HIV mutations, and to evaluate effective strategies in HIV drug therapy interventions.

Application of systems analysis in modelling the risk of bovine spongiform encephalopathy (BSE)

Bovine spongiform encephalopathy (BSE), widely known as “mad cow disease”, has virtually crippled the British livestock industry. Even though, no cases of BSE have been reported in the United States (US), a similar epidemic in the US would be catastrophic. The added concern for the risk of introduction of the human disease called variant Creutzfeldt‐Jacob disease that has been linked to eating meat of BSE infected cattle compounds the risk of BSE. Systems dynamics models based on the underlying transmission pathways of BSE can help to anticipate the spread of this disease in different cattle populations and assist in the evaluation of potential risk mitigations for preventing its introduction or controlling its spread if it was introduced. With this in mind, an age and health status structured systems dynamics model was developed. By making assumptions and setting up feasible scenarios, the model can be used to examine potential prevalence and incidences rates of BSE; the effect of mitigations including changes in feeding habits or rendering processes and/or other policies and regulations designed to prevent the introduction of BSE. The systems dynamics simulation model enabled us to create virtual experiments whose real‐world analogues would otherwise be expensive, dangerous, or even impossible to carryout.

A quantitative risk assessment of multiple factors influencing HIV/AIDS transmission through unprotected sex among HIV-seropositive men.

Abstract The objective of this study is to conduct a quantitative risk assessment of multiple factors influencing HIV/AIDS transmission through unprotected sexual practices among HIV-seropositive men. A knowledgebase was developed by reviewing different published sources. The data were collected from different sources including Centers for Disease Control and Prevention, selected journals, and reports. The risk pathway scenario tree was developed based on a comprehensive review of published literature. The variables are organized into nine major parameter categories. Monte Carlo simulations for the quantitative risk assessment of HIV/AIDS transmission was executed with the software @Risk 4.0 (Palisade Corporation). Results show that the value for the likelihood of unprotected sex due to having less knowledge about HIV/AIDS and negative attitude toward condom use and safer sex ranged from 1.24×10−5 to 8.47×10−4 with the mean and standard deviation of 1.83×10−4 and 8.63×10−5, respectively. The likelihood of unprotected sex due to having greater anger-hostility, anxiety, less satisfied with aspects of life, and greater depressive symptoms ranged from 2.76×10−9 to 5.34×10−7 with the mean and standard deviation of 5.23×10−8 and 3.58×10−8, respectively. The findings suggest that HIV/AIDS research and intervention programs must be focused on behavior, and the broader setting within which individual risky behaviors occur.

Psychosocial responses associated with perceived risk of cancer in an African-American community.

This epidemiologic health survey study examined the association between health risk perceptions and psychosocial factors in 145 African Americans in East Montgomery, Alabama. The survey gathered information on demographics, population dynamics, health risk perceptions, and coping behaviors. Psychosocial variables measured were worries, concern, stress, and trauma associated with perceived risk of cancer. Results indicated that women were more concerned about the environmental health risks in their community than men. Compared to men, women were highly concerned about the economic effect of perceived environmental health risk. The findings indicate that an individuals health status and educational level were significant predictors of psychosocial responses.