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In addressing pandemics, science has never seemed more needed and useful, while at the same time limited and powerless. The existing contract between science and society is falling apart. A new covenant is urgently needed to navigate the days ahead.

Background: Sleeping sickness is a parasitic, vector-borne disease, carried by the tsetse fly and prevalent in sub-Saharan Africa. The disease continues to pose a public health burden in Uganda, which experienced a widespread outbreak in 1900-1920, and a more recent outbreak in 1976-1989. The disease continues to spread to uninfected districts. Objectives: This paper compares the spatial distributions of sleeping in Uganda for the 1900-1920 outbreak period with current disease foci, and discusses information gaps and implications arising for future research, prevention and control. Methods: Population census records for 1911 and sleeping sickness records from Medical and Sanitary Reports of the Ugandan Protectorate for 1905-1936 were extracted from the Uganda Archives. Current sleeping sickness distribution data were provided by the Ministry of Health, Uganda. These were used to develop sleeping sickness distribution maps for comparison between the early 1900s and the early 2000s. Results: The distribution of sleeping sickness from 1905-1920 shows notable differences compared to the current distribution of disease. In particular, archival cases were recorded in south-west and central Uganda, areas currently free of disease. The disease focus has moved from lakeshore Buganda (1905-1920) to the Busoga and south-east districts. Conclusions: Archival sleeping sickness distributions indicate the potential for a much wider area of disease risk than indicated by current disease foci. This is compounded by an absence of tsetse distribution data, continued political instability in north-central Uganda, continued spread of disease into new districts, and evidence of the role of livestock movements in spreading the parasite. These results support concerns as to the potential mergence of the two disease foci in the south-east and north-west of the country. > African Health Sciences Vol. 6 (4) 2006: pp. 223-231

The objectives of this study were to describe the serological prevalence of maedi-visna in a sample of Ontario sheep flocks, and to identify management and demographic variables that were associated with seroprevalence for maedi-visna. A sample of 103 sheep flocks in Ontario was randomly selected from those flocks participating in the Red Meat Plan. The owners of these flocks were surveyed regarding management procedures on their farms, and blood samples were taken from a random sample of ewes in each flock. At least one ewe tested serologically positive, based on the agar gel immuno-diffusion test, in 69.9% of the farms. Positive serological reactions occurred in 20.9% of the 3880 sheep tested. Flock demographics and farm management variables were considered in a multiple regression model, and several factors were positively associated with higher maedi-visna seroprevalence rates. These included the average age of the flock, the number of years the owner had been sheep farming, the practice of using foster ewes, the practice of allowing lambs to have contact with other ewes that are lambing, and the average pasture acreage per ewe.

Associations between heifer calf management and mortality were studied on 104 randomly selected Holstein dairy farms in southwestern Ontario between October 1980 and July 1983. At the farm level, data were stratified by season, with two six-month seasons (winter and summer) per year. The odds of farms with particular management strategies having above-median morbidity were calculated. At the individual calf level, the odds of a calf being treated, controlling for farm of origin and month of birth, were calculated for different management practices. Larger farms had significantly greater odds of experiencing mortality than smaller farms in both winter and summer. Farms which had policies of attending calvings and ensuring that calves received their first colostrum had significantly lower odds of experiencing winter mortality than farms which did not have these policies. Farms which housed calves in hutches had significantly lower odds, and those which housed calves in group pens had significantly higher odds, of experiencing summer mortality, than farms which used individual indoor calf-pens. A policy of teat removal between four weeks of age and weaning was associated with increased odds of summer mortality. At the individual calf level, calving ease, sire, navel treatment, assistance at first colostrum feeding, administration of vitamins A, D and E and anti-scour vaccines to the pregnant dam, and place of calving, were all associated with significantly altered odds of dying. However, several interactions entered the statistical models, and the effects of those management practices were not all straightforward.

Hair samples from newborn heifer calves on Holstein dairy farms in southwestern Ontario were analyzed for selenium content by means of instrumental neutron activation analysis. The mean selenium level in the hair of calves which subsequently died at less than six weeks of age did not differ from selenium levels in the hair of calves matched by farm and birthday (overall mean 0.28 ppm). The mean selenium level in the hair of calves which were not treated for disease during the first four weeks of life was 0.42 ppm, while that from appropriately matched treated calves was 0.36 ppm; the difference between the means was significant at p = 0.054. Based on the above associations, it is suggested that higher selenium levels in newborn calves may have some protective effect against morbidity.

Risk assessment from 2 x 2 tables can be very useful for both clinicians and researchers. The measures described go beyond demonstrating a statistical association between some factor and disease or death, and attempt to assess, in real world terms, just how important a particular factor may be. Five measures of risk are explained by means of a veterinary example. The odds ratio compares the odds of animals succumbing to disease or death if they are exposed to a factor, compared to the odds of succumbing if they are not exposed. Attributable rate and attributable proportion (risk) measure the amount of disease or death in the exposed group which can actually be attributed to the factor under study. Population attributable rate and population attributable proportion (risk) extend these measures to the real world: how much of the disease or death on the farm might we be able to prevent? Calculation of measures of risk from a data set requires that a number assumptions be met, and that the data used be of the highest quality.

Fecal samples from calves on 78 randomly selected Holstein dairy farms in southwestern Ontario were screened for Salmonella, Campylobacter jejuni/coli, enteropathogenic Escherichia coli, rotavirus and coronavirus. Based on the observed prevalence, 22% of farms had calves infected with Salmonella, 13% with Campylobacter jejuni/coli, 41% with enteropathogenic E. coli, 19% with rotavirus and 5% with coronavirus. These estimates can be modified, using a method developed by Mullen and Prost (1983) for the World Health Organization, to account for the nature of the laboratory test used. If the test is assumed to have no false positives (that is, if an organism is detected it must be there), then the observed prevalence estimates seen on this study may greatly underestimate the true prevalence of infected premises. The use of nipple feeders for calves was associated with an increased probability of farms having calves shedding detectable fecal levels of Salmonella, E. coli, or one of the two viruses. The use of group pens was associated with an increased odds of finding C. jejuni. Calves with diarrhea on these farms tended to have increased odds of shedding rotavirus, and E. coli with the K99 antigen. However, at the farm level, none of the organisms was associated with above median levels of morbidity. Farms positive for one or other of the viruses had increased odds of experiencing calf mortality relative to virus-negative farms, and farms positive for C. jejuni/coli had decreased odds of mortality.(ABSTRACT TRUNCATED AT 250 WORDS)