Dermoid cysts in caribou.

Subcutaneous dermoid cysts were identified in eight wild caribou (Rangifer tarandus) from widely dispersed locations in northern Canada and in one wild caribou from Alaska. The dermoid cysts from Canadian caribou were found among 557 diagnostic specimens that had been detected by hunters and submitted by resource officers and biologists between 1 January 1966 and 15 May 2007. All of the cysts were located in the cervical region, and five of nine cysts were found in the throat area. All of the animals for which the age was known were adult; males and females were equally represented. Dermoid cysts were not diagnosed in any of 1,108 white-tailed deer (Odocoileus virginianus), 293 mule deer (Odocoileus hemionus), 174 elk (Cervus elaphus), or 529 moose (Alces alces) examined during the same period at the Canadian laboratory.

Tularemia in deer mice (peromyscus maniculatus) during a population irruption in Saskatchewan, Canada.

Type B tularemia caused by Francisella tularensis subsp. holarctica was diagnosed in deer mice (Peromyscus maniculatus) found dead at four sites in west-central Saskatchewan during April and May 2005. The occurrence of tularemia coincided with a decline in the number of deer mice in part of a large area (>22000 km(2) ) in which deer mice had been extremely abundant during the autumn of 2004 and spring of 2005, and in which mice caused damage to crops in the autumn of 2004. This is apparently the first report of tularemia as a cause of death of wild deer mice. The bacterium isolated from deer mice was atypical in that cysteine was not required in the media used for isolation. Three isolates tested were genotypes not previously identified in Canada. There were no reports of human disease in the area.

Demographic features of Bartonella infections in Richardson's ground squirrels (Spermophilus richardsonii).

The epidemiology of Bartonella infections in Richardson's ground squirrels (Spermophilus richardsonii) was studied at multiple sites in Saskatchewan, Canada, from 2002 to 2004. The overall prevalence of Bartonella infection was 48%. Juvenile squirrels were significantly more likely to be infected with Bartonella than were adults (58% and 37%, respectively), and juvenile animals also were significantly more likely to have high levels of bacteremia compared to adult animals. Prevalence of Bartonella infection appeared to decrease with age; only 24% of animals known to be > or = 2 yr old were infected with Bartonella. Prevalence of infection was lowest in May (27%) and highest in late summer and early autumn (71%). The prevalence of fleas also varied seasonally, and animals were more likely to have fleas in the late summer and early autumn than in early summer. We found no relationship between Bartonella prevalence and host density or flea prevalence.

Effect of experimental ectoparasite control on bartonella infections in wild Richardson's ground squirrels.

The purpose of this study was to investigate the role of ectoparasites in transmitting Bartonella infections in wild Richardson's ground squirrels (Spermophilus richardsonii). Richardson's ground squirrels were trapped, examined for fleas, and tested for Bartonella bacteremia once monthly, at six sites, from April to September 2004. After the initial trapping session in April, burrows at three sites were treated with deltamethrin insecticide. Richardson's ground squirrels trapped on treated sites were less likely to have fleas and had fewer fleas than squirrels on control sites in all months following treatment. We found no difference in the prevalence of Bartonella infections on control and treated sites in May, immediately following treatment; however, significantly fewer squirrels were infected with Bartonella on treated sites in June and July. We conclude that ectoparasites are a main route of transmission for Bartonella infections in Richardson's ground squirrels.

Mortality of geese as a result of collision with the ground.

Two incidents are reported in which groups of migrating wild geese were found dead in agricultural fields in southern Manitoba during spring. In each case, the birds died overnight and poisoning was suspected; however, the birds had lesions of severe traumatic injury. The first incident, in 1985, involved about 150 lesser snow geese (Anser caerulescens caerulescens); the second, in 2003, involved 62 Canada geese (Branta canadensis). Both incidents occurred on dark, moonless nights. One possible explanation is that the birds became disoriented in a manner analogous to spatial disorientation described in aircraft pilots and flew as a flock directly into the earth. In the first incident, geese might have been frightened by sonic booms from aircraft; in the second, there was a thunderstorm with strong gusty winds in the area.

Pathology of experimental avian cholera in mallard ducks.

Mallard ducks (Anus platyrynchos) challenged with two isolates of Pasteurella multocida developed either acute or chronic lesions, depending on the isolate of P. multocida and the inoculation dose. Ducks that died acutely of avian cholera had lesions of a hemorrhagic septicemia with widespread vascular damage and focal necrosis in liver, spleen and other organs. Ducks that survived challenge developed chronic lesions in a variety of organs, including brain, lung, air sacs, joints, and eyes. Some surviving ducks sequestered bacteria within these loalized lesions and may be potential "carrier" birds. The possible pathogenesis of P. multocida infection in ducks is discussed.

A simple vascular perfusion technique for use in waterfowl.

A simple vascular perfusion technique is described for fixation of avian tissues for study at the light-microscope level. The technique relies on gravity feed of perfusate and gives reliable fixation of the nervous system, liver, kidney, and cardiac and skeletal musculature.

Viral tracheitis in goslings in Saskatchewan.

Up to 12% mortality occurred in goslings between 4 and 11 days of age in two sequential hatches from a single breeder flock. Respiratory signs were noted before the birds died. The most consistent necropsy finding was a white opaque plug of fibrin and cellular debris in the trachea. The tracheal epithelium was hyperplastic and metaplastic with intranuclear inclusion bodies present in superficial cells. An adenovirus was isolated in both chicken and goose embryo liver cells.

Disease management strategies for wildlife.

Three basic forms of management strategies exist for wildlife disease, as follows: prevention of introduction of disease, control of existing disease or eradication. Management may be directed at the disease agent, host population, habitat or be focused on human activities. Disease agents may be dealt with in the environment through disinfection or in the host through treatment. Disinfection and pesticides used to destroy agents or vectors are limited to local situations, may have serious environmental effects and may result in acquired resistance. Difficulty in delivering treatment limits chemotherapy to local situations. Host populations may be managed by immunisation, by altering their distribution or density, or by extirpation. Immunisation is best suited for microparasitic exogenous infections with a low reproductive rate and in populations which have a low turnover. Mass immunisation with oral baits has been effective, but this strategy is limited to a few serious diseases. It is difficult to move wild animals and techniques to discourage animals from entering an area become ineffective rapidly. The setting up of fences is feasible only in local situations. Selective culling is limited to situations in which affected individuals are readily identifiable. General population reduction has had little success in disease control but reducing populations surrounding a focus or creating a barrier to disease movement have been successful. Population reduction is a temporary measure. Eradication of a wildlife population has not been attempted for disease management. Habitat modification may be used to reduce exposure to disease agents, or to alter host distribution or density. Management of diseases of wild animals usually requires a change in human activities. The most important method is by restricting translocation of wild animals to prevent movement of disease.

Pathogenesis of neurological signs associated with bovine enteric coccidiosis: a prospective study and review.

Various hypotheses have been proposed for the pathogenesis of the neurological signs associated with bovine enteric coccidiosis. We undertook a prospective study of cases of bovine enteric coccidiosis with and without nervous signs to test the validity of these hypotheses and explore other possible pathophysiological mechanisms. Clinical, pathological and toxicological data from 12 calves with, and 15 calves without, neurological signs were compared. Calves with neurological signs had a lower liver Cu concentration (p less than 0.01) and a higher plasma glucose concentration (p less than 0.05) than did calves without neurological signs. Hyperglycemia and Cu deficiency may increase the susceptibility to central nervous system damage, but are not likely to account for the onset of neurological signs in calves with enteric coccidiosis. The results of the study suggest that the following are not involved in the pathogenesis of "nervous coccidiosis": disturbance of serum Na, K, Ca, P, or Mg concentration, vitamin A deficiency, thiamine deficiency, anemia, lead intoxication, uremia, Haemophilus somnus meningoencephalitis, severity of coccidial infection, gross alterations in intestinal bacterial flora and hepatopathy.

Characteristics of the labile neurotoxin associated with nervous coccidiosis.

Reported are the results of preliminary attempts to characterize the molecular weight, heat sensitivity and other features of a labile neurotoxin identified in the serum of calves exhibiting neurological signs in association with coccidial enteritis. The labile neurotoxin activity is heat labile (60 degrees C for 30 min) and is lost upon exposure to acidic pH (5.5) and cysteine (1.75 g/100 mL serum). Activity can be recovered from the precipitate of a 30% wt/vol solution of (NH4)2SO4 in serum. Ultrafiltration trials suggest that labile neurotoxin activity may be linked to a molecule of over 300,000 MW.

Labile neurotoxin in serum of calves with "nervous" coccidiosis.

Mouse inoculation was used to test for the presence of a toxin in the serum, cerebrospinal fluid, and intestinal contents collected from cases of bovine enteric coccidiosis, with and without neurological signs, and from control calves. Intravenous inoculation of mice with 10 mL/kg of serum from calves showing nervous signs caused effects significantly different from those caused by the inoculation of serum from calves not showing nervous signs and from control calves. The effect was particularly evident in female mice. At this dosage severe neurological signs such as loss of righting reflex, seizures and death occurred only with serum from calves with "nervous coccidiosis". The results suggest that serum from the calves with neurological signs contains a neurotoxin. This toxin appears to be highly labile. It was not present in the cerebrospinal fluid at levels comparable to those in the serum. The significance of this labile neurotoxin with respect to the pathogenesis of the neurological signs associated with bovine enteric coccidiosis is unknown.

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.

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.

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.

Forensic (medico-legal) necropsy of wildlife.

Post-mortem examination of wild animals for legal purposes has become increasingly common. Special procedures are necessary during such necropsies to ensure that the information collected is suitable for use in a court of law. Forensic necropsies should be performed by pathologists with formal training and experience, because these credentials will be examined if a case reaches court. There must be strict attention to maintaining a chain of custody when specimens are received from the field and in all subsequent procedures, so that the identity of specimens and information resulting from the necropsy is beyond question. A complete record must be kept of all procedures and observations. The necropsy report must be detailed, clear and, as far as possible, written in non-technical language. Photography should be used to preserve visual evidence. Special precautions are required for collecting specimens, such as bullets, suspected toxins, and material for DNA analysis, and for sending these specimens to other laboratories.

Besnoitiosis in a woodland caribou.

Besnoitiosis was diagnosed in an adult male woodland caribou found dead in northern Saskatchewan. The lesions present were comparable to those of chronic besnoitiosis in cattle, and were much more severe than those previously described in domestic reindeer and barren-ground caribou.

Avian botulism--another perspective.

Waterfowl botulism is unique among intoxications because toxin produced within its victims leads to secondary poisoning of other birds. Because of this phenomenon, the epizootiology of the carcass-maggot cycle of botulism resembles that of an infectious disease and the reproductive rate (R) of the disease could be defined as the average number of secondary intoxications attributable to a single carcass introduced into a marsh. I propose that toxin production and botulism occur commonly at a low level in many marshes and that factors which influence R determine when the disease expands into a large epizootic. A model that incorporates the number of carcasses occurring in a marsh, the probability of a carcass containing spores, the probability of a carcass persisting until toxin-bearing maggots emerge, and the contact rate between live birds and toxin, may be useful for predicting the extent of secondary poisoning, for identifying questions for research, and as a theoretical basis for management.

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.

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.