D. Bruce Hunter

MORTALITY IN FLEDGLING GREAT HORNED OWLS FROM BLACK FLY HEMATOPHAGA AND LEUCOCYTOZOONOSIS

Black fly feeding alone and in concert with Leucocytozoon spp. infection caused mortality in fledgling great horned owls (Bubo virginianus) in the Yukon, Canada 1990 to 1991. These mortalities occurred during a year of food shortage corresponding with a decline in the population of snowshoe hare (Lepus americanus), the main prey for great horned owls. We hypothesize an interaction between food availability and the consequences of host-parasite interactions.

AN OUTBREAK OF SCHISTOSOMIASIS IN ATLANTIC BRANT GEESE, BRANTA BERNICLA HROTA

A heavy infection with schistosomes of the genera Trichobilharzia and Dendritobilharzia was considered the cause of 90% mortality in a group of 40 wild-caught Atlantic brant geese (Branta bernicla hrota) that were maintained in captivity on a fresh-water pond in Aurora, Ontario. Numerous adult worms and eggs were disseminated in many organs throughout the body of all birds examined. The main pathological findings, attributed to both eggs and adults, included emaciation, thrombosis of the caudal mesenteric vein and its branches, fibrinohemorrhagic colitis, and in some birds, heptomegaly. Translocation of brant geese from their natural marine environment to a fresh-water pond may have caused them to be exposed to parasites which they would not normally encounter.

Molecular identification of Eimeria species infecting market-age meat chickens in commercial flocks in Ontario

A previously described multiplex PCR was evaluated for the identification and prevalence of Eimeria species in market-age commercial chicken flocks in Ontario. The multiplex PCR based on species-specific RAPD-SCAR markers was able to distinguish six available laboratory strains of Eimeria species (E. tenella, E. maxima, E. necatrix, E. mitis, E. acervulina, and E. brunetti) and E. tenella, E. maxima and E. acervulina in unknown field samples, including multiple infections in single reactions. No backyard (0/77) and 20/360 market-age commercial chickens were oocyst-positive using standard fecal flotation methods. PCR identified E. tenella alone (9/360, 2.5%), E. maxima alone (5/360, 1.38%), E. maxima plus E. tenella (5/360, 1.38%) and E. acervulina alone (1/360, 0.27%) in market-age commercial broilers. This is probably the first time the multiplex PCR has been evaluated in poultry establishments in Canada and illustrates the value of the tool in coccidiosis epidemiology on commercial farms.

Nursing disease in mink: ranch-level epidemiology

Abstract A cross-sectional study on the epidemiology of nursing disease in mink was undertaken in 1990 on 64 ranches in southern Ontario, Canada. All lactating females dying on these ranches between parturition and 1 July were selected for study, and the cause of death was determined by gross necropsy. An on-site questionnaire, including questions on ranch design, management and production, was completed for each ranch. On four ranches, data were also collected on the location of nursing disease morbidities within the ranch. The purpose of the study was to provide a basic epidemiological description of the disease at the ranch level, and to test the associations between a variety of ranch-level factors and the incidence of nursing disease. The 64 ranches in the study represented 65% of all mink ranches in Ontario with more than 100 breeding females, and 84% of all females on an individual basis. Nursing disease was the most frequent cause of death (57% of all submissions). The incidence of nursing disease range from zero (five ranches) to 11.6% (median, 1.2%). Losses were almost twice as high on the west sides of barns as on the east, but there was no clustering of nursing disease morbidities within cage rows. The majority of the variation among ranches was not accounted for by the ranch-level variables examined, but associations between the incidence of nursing disease and the type of water source, size of the ranch and source of feed were present.

Nursing disease in mink: individual-level epidemiology

Abstract A cross-sectional study on the epidemiology and pathology of nursing disease in mink was undertaken in 1990 on 64 ranches in southern Ontario, Canada. A subset of 14 of these ranches also was involved in a prospective case-control study, exploring the effects of several individual-level factors on the probability of nursing disease occurrence. The outcome of interest was generally mortality due to nursing disease, as determined by gross post-mortem examination; on six ranches, however, morbidity data also were collected. The factors examined were: dam age, color phase, date of parturition, number of kits raised, and date of death. The risk of nuring disease increased with increasing litter size, though the effect tapered off somewhat in females with litters of more than seven kits. Color phase was highly significant on many individual ranches; however, the color with the greatest incidence was different from one ranch to the next. The mean time between parturition and onset of disease was 42 days (SD=3.9). This was remarkably consistent among ranches, even though their median calendar dates of parturition and disease onset varied. Age and date of parturition were not associated with nursing disease.