Tsegaye Habtemariam

An epidemiologic systems analysis model for African trypanosomiasis

Abstract Systems analysis and simulation modelling were applied to describe the quantitative epidemiology of trypanosomiasis. With the aid of a causal loop diagram, and based on mechanistic decomposition of the components of the trypanosomiasis-tsetse complex, a Forrester flow diagram was developed. Interactions between factors in the system and variables required in the model were estimated from existing data. Appropriate differential equations were set up to describe the dynamics of the model based on mass action theory. Simulation involved integrating birth and death rates, infection and population dynamics as they relate to the carrying capacity of the land, and fluctuations in temperature and rainfall. Both deterministic and stochastic aspects were considered. The model was computerized using a continuous systems modelling program and integration time intervals of one day. Simulations were run using various initial conditions as provided by data from southwestern Ethiopia. The performance of the model was satisfactory when compared with an independent set of data. The procedure enhanced our understanding of the dynamics of the trypanosomiasis-tsetse complex; it could thus be used as a guide to evaluating different programs to control trypanosomiasis in Ethiopia and in other African countries.

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.

Application of a linear programming model to the control of African trypanosomiasis

Abstract A linear programming (LP) model was designed to evaluate trypanosomiasis control activities in south-western Ethiopia. The objectives included maximizing net benefits, utilization of unskilled labor, and resettlement of reclaimed land, and decreasing the prevalence of trypanosomiasis from 20% to less than 5% at the end of 5 years, subject to epidemiological, ecological and economic constraints. The model was a multiperiod specification with 127 equations and 81 activities for the project period of 5 years. The optimal solution required reclamation of 5221 km 2 of tsetse infested land and used treatment of cattle at maximal levels. At the end of the project period, the prevalance decreased to 2% with net benefits of E

Conspiracy Beliefs about HIV/AIDS among HIV-Positive African-American Patients in Rural Alabama

1.281 million. LP provided a potentially optimal means of resource allocation in the short run and a means of identifying those restrictive resources which could be vital to long range planning.

Evaluation of trypanosomiasis control alternatives using an epidemiologic simulation model

This is apparently the first survey examining endorsement of HIV/AIDS conspiracy beliefs and their relations to educational attainment among 205 HIV-positive African-American patients receiving care at an AIDS Outreach Organization in Alabama. 31% somewhat or strongly believed that, “AIDS is a form of genocide against African Americans,” 29% strongly agreed that “AIDS was created by the government to control the black population,” 56.1% agreed that the government is withholding a cure for AIDS, and 69.8% agreed that the government is withholding information about the disease from the public. 52% agreed that “HIV is a manmade virus,” and 43.1% that “AIDS was produced in the governments laboratory.” Respondents with high school or college education were less likely to endorse conspiracy beliefs. Being open and sensitive to questions about conspiracy beliefs plus understanding the historical roots and social context from which such questions arise in African-American communities is needed to counter such beliefs.

Novel genomic tools for specific and real-time detection of biothreat and frequently encountered foodborne pathogens.

Abstract The effect of various disease-vector control alternatives on the prevalence of trypanosomiasis in southwest Ethiopia was examined with the aid of an epidemiologic model. The alternatives considered included vegetation clearing by manual labor, game elimination, insecticidal spraying from airplanes coupled with settlement, use of sterile male Glossina , avoidance of tsetse infested areas, increasing the resistance of the cattle population, therapy, and combinations of the above methods. First, the currently estimated endemic prevalence of trypanosomiasis (27.3%) in the simulated area of Ethiopia was established and maintained over a 10 year period. Then, various control alternatives were introduced and the simulation was run for an additional 10 years to observe the effect of these control alternatives on the prevalence. The combined use of vegetation clearing, insecticides, therapy, and settlement (or resettlement) was the most effective and feasible method of trypanosomiasis control for the simulated situation.

The benefit—cost analysis of alternative strategies for the control of bovine trypanosomiasis in Ethiopia

The bacterial genera Escherichia, Salmonella, Shigella, Vibrio, Yersinia, and Francisella include important food safety and biothreat agents. By extensive mining of the whole genome and protein databases of diverse, closely and distantly related bacterial species and strains, we have identified novel genome regions, which we utilized to develop a rapid detection platform for these pathogens. The specific genomic targets we have identified to design the primers in Francisella tularensis subsp. tularensis, F. tularensis subsp. novicida, Shigella dysenteriae, Salmonella enterica serovar Typhimurium, Vibrio cholerae, Yersinia pestis, and Yersinia pseudotuberculosis contained either known genes or putative proteins. Primer sets were designed from the target regions for use in real-time PCR assays to detect specific biothreat pathogens at species or strain levels. The primer sets were first tested by in silico PCR against whole-genome sequences of different species, subspecies, or strains and then by in vitro PCR against genomic DNA preparations from 23 strains representing six biothreat agents (Escherichia coli O157:H7 strain EDL 933, Shigella dysenteriae, S. enterica serovar Typhi, F. tularensis subsp. tularensis, V. cholerae, and Y. pestis) and six foodborne pathogens (Salmonella Typhimurium, Salmonella Saintpaul, Shigella sonnei, F. tularensis subsp. novicida, Vibrio parahaemolyticus, and Y. pseudotuberculosis). Each pathogen was specifically identifiable at the genus and species levels. Sensitivity assays performed with purified DNA showed the lowest detection limit of 128 fg of DNA/μl for F. tularensis subsp. tularensis. A preliminary test to detect Shigella organisms in a milk matrix also enabled the detection of 6 to 60 CFU/ml. These new tools could ultimately be used to develop platforms to simultaneously detect these pathogens.

Epidemic and endemic characteristics of trypanosomiasis in cattle: A simulation model

Abstract A benefit—cost analysis of trypanosomiasis control programs for an area of 1500 km2 in southwest Ethiopia, for a project span of 15 years at a discount rate of 10%, was conducted to determine cost effective and benefit maximizing alternatives. The trypanosomiasis control scenarios considered were: (a) reduction of tsetse flies by use of insecticides sprayed from knapsacks, (b) game reduction, (c) no control program. Information on costs was obtained from existing data. A Leslie type model was utilized to simulate the cattle population dynamics in southwest Ethiopia for trypanosomiasis controlled versus uncontrolled situations. From these results costs and benefits of control were quantified. The benefit—cost analysis using net present values (NPV) and benefit/cost (B/C) ratio as decision criteria of project feasibility and efficiency, indicated that insecticide application was preferable to game reduction. Estimates of present value costs were E

Assessing the Key Attributes of Low Utilization of Mammography Screening and Breast-self Exam among African-American Women

630.17 per km2 per year while the present value benefits were E