A case control study of fowl pox in southeastern Ontario.

An outbreak of fowl pox, which occurred in south-eastern Ontario between July 1988 and April 1989, was investigated in the spring of 1989 to determine factors associated with the spread of the disease. Clinical fowl pox was confirmed on five farms (cases). Twenty-seven farms, out of 35 egg producers with quota from Durham region to Northumberland county, provided information as controls. Bivariate analyses were performed on mail survey data using Fisher's exact test and odds ratios. Although the tests of hypotheses lacked statistical power because of the small number of case farms, and barns, a number of significant associations were found. At the farm level, fowl pox infection was associated with pullets purchased from a particular pullet grower. At the barn level, fowl pox infection was associated with pullets from a particular grower, mixing different groups of pullets, and a trend towards having birds early in the laying period, and higher numbers of birds placed. Fowl pox-infected barns had higher mortality and lower egg production postoutbreak. The results may indicate that the virus enters the laying barn at, or near, the time new birds are placed. Better communication among producers, catch-and-fill crews, and others associated with the egg industry, as well as more complete records of dates, sources, and persons involved with pullet placements, are recommended.