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Biomedical subjects

G Wobeser

Publications and source records attributed to G Wobeser.

At least 37 records · Page 2Linked to original sources
PubMed1995

Vitamin A status of wild mallards (Anas platyrhynchos) wintering in Saskatchewan.

Vitamin A status of wild male mallards (Anas platyrhynchos) overwintering in Saskatchewan, Canada was determined. Vitamin A levels < 0.2 micrograms hepatic retinyl palmitate/g liver, occurred in 6% and 25% of male mallards sampled in 1991 to 1992 and 1992 to 1993, respectively. There was no temporal trend in vitamin A levels over either winter. Squamous metaplastic lesions, commonly associated with vitamin A deficiency in domestic animals, were not observed in any bird; hence, they were not a good indicator of vitamin A status in wild mallards. Serum retinol was not a good indicator of vitamin A status in wild mallards. Many mallards in good body condition had low vitamin A levels; thus, we propose that good body condition and ample fat stores are not indicative of overall health of the bird.

Animal Nutritional Physiological Phenomena↗
PubMed1993

Observations on waterfowl carcasses during a botulism epizootic.

Several features related to waterfowl carcasses were studied at Eyebrow Lake, Saskatchewan, Canada, during a botulism epizootic in the summer of 1989. Dummy carcasses, constructed by stretching duck skins over wooden forms, were used to assess the reaction of waterbirds to carcasses. There was no significant difference in the number of American coots, ducks, grebes, or total birds present when dummy carcasses were or were not present. Only one of 42 freshly-dead bird carcasses marked and observed twice each day was removed by a scavenger prior to the development of large maggots. Maggots developed in all carcasses and were visible externally a mean of 3.9 days after placement of the carcasses. The effectiveness of carcass collection and disposal operations was tested by marking carcasses on the day prior to two scheduled clean-ups. Only 32% of marked carcasses were recovered. Large carcasses and carcasses on or near islands were recovered at a higher frequency than were small carcasses and carcasses not near islands, respectively.

Animals↗
PubMed1993

Counting dead birds: examination of methods.

We studied three methods (line transect, circular quadrat, complete count) for estimating density of dead birds, using models of sparrows and meadowlarks placed at a density of 50 birds of each type/ha. Line transects with a 500-m search line were used in cultivated pasture and native prairie habitats. The number of birds found by individual searchers in line transects varied markedly, particularly, in pasture habitat. More birds were found, and birds were detected at a greater distance, in prairie than in pasture. More meadowlarks than sparrows were found in both habitats but the mean estimated density of meadowlarks was greater than that of sparrows only in prairie. The number of birds found during most searches was less than that suggested for estimating density accurately and longer search lines were required. Density estimates obtained using circular plots to sample 10% of the prairie area ranged from 20 to 80 birds/ha for meadowlarks and from 10 to 60 birds/ha for sparrows in prairie habitat. A complete search by 25 volunteers spaced at 4 m intervals detected 90% of meadowlarks but only 62% of sparrows in pasture habitat. Mean (SD) time for a single search, including searchers and recorders, was 3.0 (0.8), 1.5 (0.3), and 7.5 person-hours, for line transect, circular plot and complete search, respectively.

Animals↗
PubMed1992

Starvation, staphylococcosis, and vitamin A deficiency among mallards overwintering in Saskatchewan.

During January to March 1991, 38 mallards (Anas platyrhynchos) found dead from a group of approximately 600 overwintering on the South Saskatchewan River were examined. Thirty birds died from starvation, four had disseminated Staphylococcus aureus infection, and the cause of death of four birds was not determined. All six birds from which the esophagus was examined microscopically, including the four birds with staphylococcosis, had squamous metaplasia of the submucosal glands, a lesion pathognomonic for vitamin A deficiency. Vitamin A deficiency may occur in mallards and other waterfowl that overwinter north of traditional wintering areas and rely on grains deficient in carotenoids.

Animals↗
PubMed1992

Traumatic, degenerative, and developmental lesions in wolves and coyotes from Saskatchewan.

A retrospective review was done of traumatic and osseous lesions in 241 wolves (Canis lupus) and 316 coyotes (Canis latrans) necropsied at the University of Saskatchewan between 1971 and 1990. Most lesions were the result of interspecific conflict. The most frequently occurring lesion in wolves was fracture of one or more bones, primarily ribs. Lesions were healed in most cases and appeared to be compatible with injuries caused by prey animals. One wolf, found dead, died as a result of thoracic trauma. Limb and skull fractures were less common. Fractures were uncommon in coyotes. The most frequent injuries in coyotes were related to gunshot wounds. Four coyotes had been killed but not eaten by wolves. One wolf had been killed and another attacked by wolves. Porcupine (Erethizon dorsatum) quills contributed to the death of a wolf and two coyotes. Degenerative joint disease, involving the spinal column and limb joints, was found in a few individuals of both species. A coyote had severe anomalies of the spinal column and a wolf had anomalous external genitalia.

Abnormalities, Multiple↗
PubMed1992

Carcass disappearance and estimation of mortality in a simulated die-off of small birds.

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 > or = 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.

Animals↗
PubMed1991

Multicentric intramuscular lipomatosis/fibromatosis in free-flying white-fronted and Canada geese.

Over a period of 9 yr, seven white-fronted geese (Anser albifrons) and one Canada goose (Branta canadensis) with multiple intramuscular mesenchymal tumors were encountered in Saskatchewan (Canada) and one similarly affected Canada goose was seen on Prince Edward Island (Canada). The tumors in these birds consisted either of adipose tissue, fibroblastic tissue, or a mixture of both types of tissues. The high prevalence of this condition in white-fronted geese suggested a genetic influence.

Animals↗
PubMed1989

Concentration of creatine kinase and aspartate aminotransferase in the blood of wild mallards following capture by three methods for banding.

The concentration of the enzymes creatine kinase (CK) and aspartate aminotransferase (AST), that are released from damaged muscle, was measured in the blood of wild adult male mallards (Anas platyrhynchos) captured for banding in decoy and bait traps and by rocket net. The concentration of CK and to a lesser extent AST was elevated markedly in ducks captured by all methods, indicating muscle injury. The level of CK was significantly greater in ducks captured in decoy traps and rocket net than in those captured in bait traps. This elevation appeared to be related to the length of time the birds were restrained and to the method of restraint.

Animals↗
PubMed1988

Effects of sodium and magnesium sulfate in drinking water on mallard ducklings.

One-day-old mallard (Anas platyrhynchos) ducklings were given drinking water for up to 28 days that contained concentrations of sodium and/or magnesium similar to those found in saline wetlands. Growth, tissue development, and biochemical characteristics of these ducklings were compared to those reared on fresh water. Much of the ingested salt was excreted by passage of voluminous fluid excreta. This effect occurred in birds given water with as little as 500 ppm Mg or 1,000 ppm Na. The supraorbital salt gland was active within 4 days in ducklings drinking water containing greater than or equal to 1,500 ppm of Na. Feather growth was decreased in ducklings drinking water with greater than or equal to 1,500 ppm of either Na or Mg. Ducklings drinking water with 3,000 ppm of either ion, or 1,500 ppm of each, grew more slowly than control birds. Ducklings drinking water with 3,000 ppm of either Na or Mg had reduced thymus size and bone breaking strength. Those drinking water with 3,000 ppm of Mg, or 3,100 ppm Na and 1,300 ppm Mg also had less trabecular bone and enlarged adrenals. Birds drinking the latter water had an elevated concentration of Na and calcium, and a decreased concentration of phosphorus and chloride in their serum, and elevated plasma protein levels. Ducklings reared on fresh or slightly saline water adapted very poorly to an abrupt change to more saline water (specific conductivity = 15,250 microns hos/cm) at 14 days of age. These birds stopped eating, became inactive and some died within 3 days; survivors had many tissue and biochemical abnormalities at 20 days of age. The level of salinity in these trials was similar to that in "brackish" or "moderately saline" wetlands and lower than that previously found to have effects on growth and feathering of ducklings. Many of the sublethal effects were subtle and non-specific manifestations of stress, and would be difficult to detect in wild ducklings on saline wetlands.

Analysis of Variance↗
PubMed1988

Toxic effects of natural saline waters on mallard ducklings.

Water from 10 saline wetlands in Saskatchewan was provided as drinking water for 1-day-old mallards (Anas platyrhynchos). Ducklings given water with conductivity from 3,750 to 7,490 microns hos/cm grew as well as birds on fresh water during a 14-day trial, but birds given water with conductivity of 4,000 microns hos/cm grew poorly during the last 2 wk of a 28-day trial. Ducklings given water with conductivity of 7,720 micron hos/cm grew poorly during a 14-day trial. Six of 10 ducklings given water with conductivity of 20,000 microns hos/cm died, and only two of nine ducklings given water with conductivity of 21,500 microns hos/cm survived 14 days. Survivors were much smaller than controls and had many abnormalities. All ducklings given water with conductivity of 35,000 and 67,000 microns hos/cm died within 60 and 30 hr, respectively. The results indicate that ducklings hatched on many saline wetlands will suffer toxic effects unless they are able to find a source of fresh water shortly after hatching.

Animals↗
PubMed1988

Effects of botulism on ducks drinking saline water.

Mallard (Anas platyrhynchos) ducklings (2 wk old) were given water from natural saline wetlands or fresh water as drinking water for 1 or 2 wk prior to, and after, receiving material containing Clostridium botulinum type C toxin. Water with conductivity ranging from 3,460 to 6,690 mu mhos/cm had no detectable effect on the occurrence or severity of clinical signs of botulism. Ducks drinking water with conductivity of 7,130 mu mhos/cm for 1 wk prior to receiving toxin had more severe clinical signs and greater mortality than did birds drinking fresh water. Ducks given the same water for 2 wk prior to receiving toxin did not differ from the controls in response to toxin. Fewer ducks in groups drinking the most saline water tested (conductivity = 13,500 mu mhos/cm) had clinical signs of botulism than in groups drinking fresh water.

Animals↗
PubMed1987

Mortality of waterfowl on a hypersaline wetland as a result of salt encrustation.

Approximately 300 geese, primarily lesser Canada geese (Branta canadensis parvipes) were found unable to fly or dead on a small hypersaline lake (conductivity 77,000-90,000 mumhos/cm) in western Saskatchewan in September 1985. The birds were heavily encrusted with sodium sulfate crystals. Dead birds that were necropsied had aspirated lake water and had evidence of acute muscle degeneration. The live geese (155) were captured and moved to nearby freshwater wetlands where most apparently survived. Some birds died of severe myopathy after translocation. Five northern shovelers (Anas clypeata) were found encrusted with salt and unable to fly on the lake approximately 10 days later. Salt encrustation apparently occurred when rapid cooling of the lake resulted in supersaturation and crystallization of the dissolved salt. A local resident recalled similar events occurring on the lake in autumn on at least two other occasions during the past 50 yr.

Animals↗
PubMed1987

Occurrence of toxigenic Clostridium botulinum type C in the soil of wetlands in Saskatchewan.

Mouse-lethal toxin identified as that of Clostridium botulinum type C by antitoxin neutralization was present in cultures of 38.0% of 326 soil samples collected from 28 wetlands in Saskatchewan. There was no difference in prevalence of toxicity between samples collected in spring and summer, and no relationship was evident between the occurrence of toxicity and water salinity, marsh type or water depth. There was a strong association between the prior occurrence of avian botulism in a marsh and the presence of toxin in cultures from soil; 59.2% of soil samples from marshes with a known history of botulism produced toxin, whereas only 6.2% of soil samples from marshes with no history of the disease produced toxin. Eight of the 10 soil samples collected from a marsh that had been dry for several years, and from another marsh that had not had a recognized outbreak of botulism for 11 yr produced toxin, indicating a long residual effect after a botulism outbreak. The results suggest that any wetland with a history of botulism is likely to suffer repeated occurrences because of heavy contamination of the soil with spores, and should be managed to control the disease.

Botulinum Toxins↗
PubMed1987

Strychnine poisoning of aquatic birds.

Strychnine poisoning was diagnosed in free-flying mallards (Anas platyrhynchos) and a ring-billed gull (Larus delawarensis) found dead on a pond in a zoo. The probable source of toxin was improperly applied strychnine-treated grain used for control of rodents on adjacent farm land. Ingesta of the birds contained 19.7-85.1 mg/kg of strychnine.

Animals↗
PubMed1987

Experimental duck plague in blue-winged teal and Canada geese.

Ten adult blue-winged teal (Anas discors) and six Canada goose (Branta canadensis) goslings were inoculated with liver tissue from a natural case of duck plague in a wild mallard (Anas platyrhynchos). Four additional teal were placed in contact with the inoculated ducks. Inoculated teal died 63.5-68 hr after inoculation; two of the contact teal died 161-162 hr after exposure. Three of the goslings died 119-133 hr after inoculation, the others were killed when moribund 90-133 hr postinfection. The clinical course of disease was extremely rapid in both species. Signs were limited to sudden onset of profound weakness, ataxia, tremors and terminal convulsions. The only consistent gross lesion in the teal was a small dark spleen; half the teal also had inconspicuous foci of epithelial necrosis in the distal esophagus and in the cloaca. Goslings had more severe lesions, with focal hepatic necrosis visible in all, and mucosal necrosis over the intestinal lymphoid tissue, and intestinal hemorrhage in three birds each. Microscopic lesions in both species were similar to those reported in mallards. Duck plague might be overlooked at necropsy of blue-winged teal, because of the paucity of gross lesions.

Animals↗
PubMed1987

Epizootic necrotic enteritis in wild geese.

Outbreaks of a disease characterized by severe necrotic enteritis occurred among Canada geese (Branta canadensis), lesser snow geese (Anser caerulescens), Ross' geese (A. rossi), and white-fronted geese (A. albifrons) on lakes in Saskatchewan and Manitoba during the autumn of 1983, 1984 and 1985. Ducks using the lakes were apparently not affected. Lesions in the geese closely resembled those described in enteritides in other species associated with the proliferation of Clostridium perfringens in the small intestine. Clostridium perfringens was present in large numbers in the affected areas of the intestine of the geese; other pathogens were not identified. It is hypothesized that an abrupt change in diet as geese begin to feed on grain disrupts the intestinal microflora, allowing C. perfringens to proliferate in the upper small intestine. Toxins produced by the bacteria then cause mucosal necrosis. Protease-inhibitory substances in some grains might also have a role in the disease.

Animals↗