Cytochrome oxidase variants of the bacterial fish pathogen, Aeromonas salmonicida, were characterized for genetic and molecular homology with cytochrome oxidase-positive isolates that typically induce furunculosis in salmonids. Protein and lipopolysaccharide moieties of the cytochrome oxidase-negative variants were similar to their typical counterparts, based on sodium-dodecyl-sulfate polyacrylamide gel electrophoresis. Pathogenicity of aberrant isolates to brook trout (Salvelinus fontinalis) was similar to typical cytochrome oxidase-positive isolates. Colorimetric deoxyribonucleic acid (DNA) hybridization in 96-well microplates yielded homology values greater than 82.5% for typical aberrant A. salmonicida isolates when photobiotinylated DNA for reference A. salmonicida 3.101 was used as a probe. The only variation of these isolates from typical A. salmonicida was a negative cytochrome oxidase reaction.

Wild-caught, immature black-bellied whistling ducks (Dendrocygna autumnalis) were inoculated with eastern equine encephalitis (EEE), St. Louis encephalitis (SLE), or western equine encephalitis (WEE) virus. Susceptibility, duration and titer of viremia, and antibody response to these arboviruses were determined. Birds from all inoculated groups became viremic. Higher virus titers occurred in the EEE group but overall mean titers were not significantly different among experimental groups. All birds inoculated with EEE and SLE viruses developed antibodies, and six of seven ducks receiving WEE virus were seropositive. All seropositive ducks had antibodies for at least 59 days, when the study was terminated. The EEE group had significantly more seropositive ducks during more days than the WEE and SLE groups. Geometric mean antibody titers were significantly smaller in the WEE group when compared to the EEE and SLE groups. Control ducks did not develop viremia or antibodies. Gross and histopathologic lesions compatible with viral encephalitis were absent in all of nine ducks necropsied. Black-bellied whistling ducks can develop low and short-term levels of viremia sufficient to infect mosquitoes, but probably cannot contribute significantly to the transmission of EEE and SLE. They may serve as good indicators of virus activity.

Cloacal swabs collected from 264 ring-billed gulls (Larus delawarensis) at four sites near Montréal, Canada were cultured for the presence of Salmonella spp., Campylobacter spp. and Listeria spp. All birds were apparently healthy when captured or killed. Of all birds examined, 8.7%, 15.9% and 9.5%, respectively, were infected with Salmonella spp., Campylobacter spp. and Listeria monocytogenes. Overall, 29.9% of gulls sampled harbored one or more of these bacteria. Gulls probably play only a minor role in the epizootiology of these bacteria.

Epizootics of saprolegniasis occurred in 20 to 60 g freshwater-cultured coho salmon (Oncorhynchus kisutch) in Miyagi Prefecture, Japan. Cotton-like mycelia occurred on the body surface of infected fish, especially around the head, the adipose fin and the caudal fin, and aseptate hyphae occurred in the lesions. The hyphae also penetrated into the muscle and blood vessels. The isolated fungus was identified by asexual morphological characteristics as Saprolegnia parasitica (syn. S. diclina Type 1), a known salmonid fish pathogen.

Histopathological effects of the chigger, Eutrombicula lipovskyana, on the mite pockets of neonatal, juvenile and adult Yarrow's spiny lizard, Sceloporus jarrovii, were investigated. Focal ulcerative dermatitis was noted in all age classes. This reaction was more diffuse in older animals in which penetration as deep as the panniculus occurred. Based on the occurrence of inflammatory reactions in neonatal lizards, S. jarrovii appears capable of recognizing foreign antigens shortly after birth. There was an increased inflammatory response in older lizards that may have been an augmented host sensitivity following repeated exposure to chiggers. Granulomas, which were interpreted as an attempt to isolate the effects of chigger bites, were noted in juveniles and adults. We propose that S. jarrovii does not develop resistance after repeated exposures to E. lipovskyana.

Sera (n = 806) from 50 populations of bighorn sheep (Ovis canadensis) in California (USA) were evaluated for antibodies to Psoroptes sp. mites using a kinetic enzyme-linked immunosorbent assay (ELISA). Test values for each sample were determined to be either positive or negative at each of two ELISA cutoff values that provided either 100% sensitivity (low cutoff) or 100% specificity (high cutoff), respectively. One hundred sixty-eight (20.8%) sera were seropositive at the low cutoff value, and 87 (10.8%) of these sera also were seropositive at the high cutoff value. Eleven populations were designated as scabies-suspect and 25 populations were designated as scabies-positive because they had at least one seropositive animal at the low and the high cutoff values, respectively. Based on these results, exposure to Psoroptes sp. mites appeared to be widely distributed among bighorn sheep populations from 1980 to 1990 and infested animals may have been present prior to 1980.

Carcasses of day-old chicks were placed randomly in grazed, mixed-grass pasture at a density of 50/ha each day for 5 days. Randomly chosen circular plots with a combined area equal to 10% of the total were searched each day for 10 days. The search method detected 95.2% of carcasses placed the day of the search but remains were found of only 20.8% of chicks placed 24 hr prior to searches. Seventy-six percent of carcasses that were observed daily disappeared completely within 24 hr. Although 250 carcasses were placed over a 5-day period, only two intact carcasses that had been in place for ≥24 hr were found during searches. Estimates derived by extrapolation from the sampled area underestimated cumulative “mortality” on the entire area and did not reflect the course of the simulated outbreak well. There was a low degree of precision among repeated samples from the same area.

American black ducks (Anas rubripes) wintering in Tennessee during 1986 to 1988 were tested for exposure to lead. Twelve percent of the birds had blood lead concentrations exceeding 0.2 ppm. Significant differences in the prevalence of lead exposure were found for adults (14.4%) and juveniles (8.2%). Exposed birds had higher blood lead concentrations at one study site, corresponding with a lower survival index.

Two rabies control tactics, trap-vaccinate-release (T-V-R) and oral vaccination were used for the control of rabies in skunks (Mephitis mephitis), raccoons (Procyon lotor), and foxes (Vulpes vulpes) in metropolitan Toronto, Canada. Using T-V-R, a mean of 45% to 72% (95% confidence limits of 40% to 81%) of the skunks and a mean of 17% to 68% (95% confidence limits of 14% to 76%) of the raccoons in a 60 km² area of Toronto were vaccinated against rabies between 1987 and 1991. The area has been free of skunk rabies from May 1989 to April 1992. Forty-five rabies cases were diagnosed during 1980 to 1986. In contrast, only three skunk cases have been reported since the vaccination program began in July 1987. The T-V-R area also remained rabies free during an epizootic of skunk rabies in metropolitan Toronto during 1991.

Following distribution of rabies vaccine-baits throughout the ravines of metropolitan Toronto, June 1989 to December 1991, 46% to 80% of the Toronto fox population was immunized during 1989, 1990 and 1991. Only one case of fox rabies was reported in metropolitan Toronto since vaccination began, compared to 80 cases reported between 1982 and 1988. The area has been free of reported fox rabies from October 1990 to April 1992.

Serologic testing, radio-telemetry and post-mortem diagnostic evaluations were used to investigate survival and causes of mortality among 17 coyotes (Canis latrans) in south-central Georgia (USA). Prevalence of canine heartworm (Dirofilaria immitis) microfilariae was lower (P = 0.057) among fall-captured (22%) than among winter-captured (75%) coyotes. Prevalence of heartworm was higher among adults than juveniles in the fall, but no significant difference was detected between animals captured in winter. Antibodies were found against canine parvovirus (65%), canine parainfluenza virus (59%), infectious canine hepatitis virus (41%), and Toxoplasma gondii (18%). Antibodies were not found to Brucella canis, canine coronavirus, five serovars of Leptospira interrogans, or canine distemper virus. Seroprevalence of canine parvovirus was lower (P = 0.009) among fall-captured animals (33%) than winter-captured animals (100%). The Kaplan-Meier estimate of annual survival was 0.500 for all animals. Juvenile survival did not differ (P = 0.79) from adult survival, but male survival (Ŝ = 0.217) was lower (P = 0.11) than female survival (Ŝ = 0.804). Two of nine (22%) mortalities were human-caused, one was