Risk assessment for Escherichia coli O157:H7 in marketed unpasteurized milk in selected East African countries.

We carried out a study to assess the risk associated with the presence of Shiga toxigenic Escherichia coli (STEC) in informally marketed unpasteurized milk in urban East Africa. Data for the risk models were obtained from on-going and recently completed studies in Kenya and Uganda. Inputs for the model were complemented with data from published literature in similar populations. A fault-tree scenario pathway and modular process risk model approach were used for exposure assessment. Hazard characterization was based on a socioeconomic study with dose-responses derived from the literature. We used a probabilistic approach with Monte Carlo simulation and inputs from farm and household surveys. The qualitative analysis suggested a low to moderate risk of infection from consuming milk and that the widespread consumer practice of boiling milk before consumption was an important risk mitigator. Quantitative analysis revealed that two to three symptomatic STEC infections could be expected for every 10,000 unpasteurized milk portions consumed, with a possible range of 0 to 22 symptomatic cases. Sensitivity analyses to assess the uncertainty and variability associated with the model revealed that the factor with the greatest influence on disease incidence was the prevalence of STEC in dairy cattle. Risk assessment is a potentially useful method for managing food safety in informal markets.

Analysis of environmental chemical residues in products of emerging aquaculture industry in Uganda as case study for Sub-Saharan Africa.

A study was conducted to analyse market-regulated heavy metals (lead, mercury and cadmium), organochlorine pesticides and total polychlorinated biphenyls (PCBs) in samples of 38 farmed fish comprising Nile tilapia (Oreochromis niloticus) (20 samples) and African catfish (Clarias gariepinus) (18 samples) from ten selected fish farms in Uganda. The goal of this case study was to understand the safety of aquaculture products from Sub-Saharan Africa. Lead was detected in all the 38 samples (maximum = 1.08 mg kg(-1) (dry weight)), mercury in 31 out of 38 samples (maximum = 0.35 mg kg(-1) (dry weight)), and cadmium in two samples (maximum = 0.03 mg kg(-1) (dry weight)). Total levels of PCBs were below the limit of detection of 0.02 mg kg(-1) (wet weight) in all the samples. Traces of 4,4'-dichloro-diphenyldichloroethylene (DDE) were detected in ten out of 38 samples (maximum = 0.01 mg kg(-1) (wet weight)) making it the most prevalent organochlorine pesticide. Other pesticides detected were: 4,4'-dichloro-diphenyl-trichloroethane (DDT) and endosulfan sulphate, which were found in one fish sample (both 0.002 mg kg(-1) (wet weight)). There was no statistically significant difference between the levels of lead and mercury in catfish and tilapia (t-test at p = 0.05). More catfish samples (eight) contained DDE as compared with tilapia (two). Cadmium, DDT and endosufan sulphate were only detected in catfish implying that catfish is more prone to contamination than tilapia. The levels of contaminants were below the US Food and Drug Administration (USFDA) action levels and European Union maximum residue limits (MRLs), indicating that such fish have the potential for export to these markets.

The prevalence of serum antibodies to tick-borne infections in Mbale District, Uganda: the effect of agro-ecological zone, grazing management and age of cattle.

Between August and October 2000, a cross-sectional study was conducted in smallholder dairy farms in Mbale District, Uganda to assess the prevalence of ticks and tick-borne diseases under different grazing systems and agro-ecological zones and understand the circumstances under which farmers operated. A questionnaire was administered to obtain information on dairy farm circumstances and practices. A total of 102 farms were visited and sera and ticks were collected from 478 animals. Sero-prevalence of tick-borne diseases was determined using an enzyme-linked immunoassay. Acaricides were used indiscriminately but the intensity of their use varied with the grazing system and zone. Cattle from different farms mixed for various reasons. During the dry seasons farmers have to get additional fodder from outside their farms that can result in importation of ticks. The prevalence of ticks and serum antibodies to tick-borne infections differed across the grazing systems and zones. The highest serum antibody prevalence (>60%) was recorded in the lowland zone under the free range and tethering grazing systems. The lowest tick challenge and serum antibody levels (<50%) were recorded in the midland and upland zones under a zero-grazing system. These findings suggest that endemic stability to East Coast Fever, babesiosis and anaplasmosis is most likely to have existed in the lowland zone, particularly, under the tethering and free-range grazing systems. Also, endemic stability for babesiosis existed in the upland zones. Endemic instability for East Coast Fever existed in the midland and upland zones. These structured observational studies are instrumental in planning of control strategies for ticks and tick borne diseases since production systems and the cattle population at high risk of the diseases in the district have been identified.

Risk factors for acute diarrhoea among inhabitants of Kampala District, Uganda.

OBJECTIVE: To identify modifiable individual and household risk factors for diarrhoea among people of all ages in Kampala district, Uganda. DESIGN: A cross-sectional, analytical study. SETTING: Multi-stage sampling. Four purposively selected parishes, two each from low and high socio-economic residential areas in Kampala district. Two randomly selected zones per parish with 60 households randomly selected from each zone. STUDY GROUP: All members present in each household at time of study. Individual and household information collected by means of personal interview using a questionnaire. MAIN OUTCOME MEASURES: Odds of diarrhoea among individuals or households exposed to a study factor compared with the odds of diarrhoea among those not exposed to the factor. RESULTS: Drinking raw chicken eggs was significantly (P < 0.01) and strongly (odds ratio (OR) = 99) associated with diarrhoea among residents of Kampala district. The odds of diarrhoea in households that 'cooked just enough food per meal' was significantly less (OR = 0.42) than in those that did not. People who used municipal water supplies and those who boiled their drinking water were significantly less likely (OR = 0.27, OR = 0.33, respectively) than those who used other water sources and/or who did not boil drinking water to report an episode of diarrhoea in the 2 weeks preceding the survey. The odds of diarrhoea were 2.6 times greater for individuals who reported a pest problem than for those who did not, while keeping pets was found to be protective (OR = 0.43). The number of income earners was also significantly (P < 0.5) and negatively (OR = 0.59) associated with the occurrence of diarrhoea in a member of the household. CONCLUSIONS: The findings of this study underscore the importance of proper food handling, preparation and eating habits as well as safe water, sanitation practices and socio-economic factors in the epidemiology of diarrhoea in developing countries.

IgG response in guinea pigs to Trichinella spiralis infection.

An enzyme-linked immunosorbent assay (ELISA) using excretory-secretory antigens was developed to study the dynamics of the IgG antibody response to varying levels of Trichinella spiralis infection in the guinea pig. Four groups of four Hartley guinea pigs each were infected with 1250, 250, 50 or 10 T. spiralis infective muscle larvae. They were bled every 15 days for 6 months and the IgG antibody response determined by ELISA. The time of seroconversion was dose dependent as the larger the dose, the earlier the response occurred. Significant differences in antibody response between the dose groups were evident at 30 days post-infection (P less than 0.05). Beyond 60 days post-infection, the response was similar in the four groups. The antibody response in the groups infected with 250 and 50 infective larvae was similar, but was significantly different from that of the high (1250) and low (10) dose groups from 30 days post-infection (P less than 0.01). Once seroconversion occurred, the antibody titer rose to the same level, irrespective of the initial dose. To compare the antibody response according to muscle larvae recovered, the guinea pigs were grouped into four categories: less than 10 larvae; 10-25 larvae, 50-80 larvae, greater than 100 larvae. A significant positive correlation (P less than 0.05) was observed at 60 days post-infection when these groups were compared.