Rabies as a threat to wildlife.

The impact of infectious disease may become progressively more harmful to a species' survival as a wild population approaches an 'extinction vortex'. This risk is especially relevant for pathogens that spread rapidly and result in high mortality rates. Rabies, a virus that infects many mammalian species, can be efficiently transmitted through infected saliva, and is fatal without prior vaccination or rapid post-exposure prophylaxis (in humans). The authors conducted an extensive literature review to identify all wild mammal species reported to have been infected with rabies virus. They found reports of infection in 190 mammalian species, including 16 with elevated risk of extinction and two for which rabies is a direct conservation threat: the Ethiopian wolf (Canis simensis) and the African wild dog (Lycaon pictus). This paper discusses selected examples in which rabies has contributed to the population decline of a species of conservation concern. In addition, the authors note the importance of the transmission of rabies virus (RABV) from domestic dogs to wildlife, and the many challenges associated with the vaccination of wild animals. With this in mind, they present potential solutions to reduce the burden of rabies on wildlife. Once stable control of RABV is achieved in domestic dogs, remaining rabies threats to wildlife conservation can be addressed more effectively.

L'impact des maladies infectieuses peut constituer une menace croissante pour la survie d'espèces animales sauvages dès lors que leurs populations sont entraînées dans la « spirale de l'extinction ¼. Ce risque se pose plus particulièrement lorsqu'il s'agit d'agents pathogènes qui se propagent rapidement et induisent un taux de mortalité élevé. Le virus de la rage affecte un grand nombre d'espèces de mammifères et se transmet facilement par contact avec de la salive infectée ; l'infection virale entraîne la mort en l'absence d'une vaccination préalable ou, chez l'être humain, d'une prophylaxie post-exposition administrée rapidement. Les auteurs ont procédé à un examen exhaustif de la littérature afin d'inventorier les espèces de mammifères sauvages chez qui l'infection rabique a été rapportée. Des cas ont été notifiés chez 190 espèces de mammifères, dont 16 présentant un risque élevé d'extinction et deux directement menacées d'extinction en raison de la rage : le loup d'Abyssinie (Canis simensis) et le lycaon (Lycaon pictus). Les auteurs apportent des précisions sur un nombre choisi d'espèces vulnérables ou en danger dont le déclin des populations est en partie imputé à la rage. En outre, ils soulignent l'importance de la transmission du virus de la rage des chiens domestiques aux animaux sauvages et décrivent les nombreuses difficultés liées à la vaccination de la faune sauvage. Ces éléments établis, ils présentent quelques solutions envisageables pour réduire le fardeau de la rage dans la faune sauvage. Une fois le virus de la rage contrôlé de manière pérenne chez le chien domestique il sera possible de lutter plus efficacement contre les autres menaces que la rage fait peser sur la conservation de la faune.

Una enfermedad infecciosa puede tener efectos cada vez más dañinos en la supervivencia de una especie a medida que una población silvestre se va aproximando a un «vórtice de extinción¼. Este riesgo tiene especial importancia en el caso de patógenos que se propagan con rapidez y causan elevadas tasas de mortalidad. La rabia, enfermedad provocada por un virus que infecta a muchas especies de mamíferos y puede transmitirse eficazmente a través de saliva infectada, resulta letal en ausencia de vacunación previa o de rápidas medidas de profilaxis tras la exposición (en el ser humano). Los autores realizaron un amplio estudio bibliográfico para determinar todas aquellas especies de mamíferos silvestres en que se hubiera descrito una infección por el virus de la rabia. Encontraron infecciones descritas en 190 especies de mamíferos, de las que 16 presentan un elevado riesgo de extinción y dos cuya conservación se ve directamente amenazada por la rabia: el lobo etíope (Canis simensis) y el licaón, o perro salvaje africano (Lycaon pictus). Los autores exponen una serie de ejemplos en los que la rabia ha contribuido al declive demográfico de una especie cuya pervivencia está en mayor o menor peligro. Los autores señalan además la importancia que reviste la transmisión del virus de la rabia de los perros domésticos a la fauna silvestre y los numerosos problemas que presenta la vacunación de los animales silvestres. Teniendo presente esta dificultad, exponen posibles soluciones para reducir la carga de rabia en la fauna silvestre. Una vez se logre estabilizar el control del virus rábico en el perro doméstico, será posible combatir más eficazmente la amenaza que representa para la conservación de las especies silvestres.

Respiratory Pathology and Pathogens in Wild Urban Rats (Rattus norvegicus and Rattus rattus).

Norway (Rattus norvegicus) and black rats (Rattus rattus) are common peridomestic species, yet little is known about wild rat ecology, including their natural diseases. We describe gross and histological lesions in the respiratory tract of a sample of 711 wild urban rats. A subset was examined for 19 distinct categories of histological lesions in the respiratory tract. Testing for known respiratory pathogens included serology and polymerase chain reaction (PCR) of lung samples. Grossly evident lesions were rare (8/711; 1%). Upper respiratory tract inflammation was present in 93 of 107 (87%) rats and included rhinitis, submucosal and periglandular lymphoplasmacytic tracheitis, and/or tracheal intraluminal necrotic debris and was significantly associated (P < .05) with the presence of cilia-associated respiratory bacillus (CARB), Mycoplasma pulmonis, and increased body mass (odds ratio [OR] = 1.09; 95% confidence interval [CI] = 1.05-1.14 per 10 g). Within the lungs, peribronchiolar and/or perivascular lymphoplasmacytic cuffs were present in 152 of 199 rats (76%) and were also significantly associated (P ≤ .02) with CARB, M. pulmonis, and increased body mass (OR = 1.20; 95% CI = 1.14-1.27 per 10 g). Rats were frequently coinfected with M. pulmonis and CARB, and lesions associated with these pathogens were histologically indistinguishable. Pneumocystis sp was detected in 48 of 102 (47%) rats using PCR but was not significantly associated with lesions. This description of pathology in the respiratory system of wild rats demonstrates that respiratory disease is common. Although the impact of these lesions on individual and population health remains to be investigated, respiratory disease may be an important contributor to wild rat morbidity and mortality.

Survey of cardiovascular pathology in wild urban Rattus norvegicus and Rattus rattus.

Norway (Rattus norvegicus) and black rats (Rattus rattus) are common commensal pests, yet little is known about the ecology of wild rats, including their natural diseases. We describe microscopic cardiovascular pathology in a subset of a sample of 725 wild urban rats. Changes observed in the pulmonary blood vessels (n = 199) included arteriolar medial hypertrophy (20.1%, n = 40) and blood vessel mineralization (19.1%, n = 38). Microscopic changes in the heart (n = 200) included myocarditis (33.5%, n = 67), fibrosis (6.0%, n = 12), mineralization (9.5%, n = 19), myocardial degeneration (22.0%, n = 44), and right ventricular hypertrophy (4.5%, n = 9). Rats with myocarditis, fibrosis, or myocardial degeneration were grouped into a composite variable: cardiomyopathy. Statistical analysis showed that the odds of being affected by cardiomyopathy were greater in male rats (odds ratio [OR] = 2.49; 95% confidence interval [CI] = 1.12-5.55) and heavier rats (OR = 1.14; 95% CI = 1.09-1.20). The odds of pulmonary arteriolar medial hypertrophy was greater in sexually mature rats (OR = 2.35; 95% CI = 0.75-7.36), while the odds of pulmonary vessel mineralization were greater in heavier rats (OR = 1.07; 95% CI = 1.03-1.11) and in black rats (OR = 5.35; 95% CI = 1.62-17.69) compared to Norway rats. To our knowledge, this is the first detailed description of pathology in the cardiovascular system of wild rats and demonstrates that cardiovascular disease is common. The impact of these lesions on individual and population health remains to be investigated.

A history of One Health.

One Health is not a new concept. It can be demonstrated that its origins and development literally run the gamut from A to Z, that is to say, from Aristotle to Zoobiquity. Indeed, the consequences of the interaction that occurs between ecosystems, animals and people have shaped, and continue to shape, the course of human events and history. A reasoned and evidence-based assessment of the history of One Health must first be founded on an agreed definition of the term, but, given the many disciplines and sciences involved, finding such a definition is no easy task. Furthermore, there is an extensive and growing list of visionary individuals who have, over the centuries, attempted to promote awareness and advance the conceptto improve the management of the risks and consequences that arise at the interface between animal, human and ecosystem health. The One Health ideas of the 21st Century constitute a re-conceptualisation of health management in response to the accelerating environmental changes of the past 100 years, changes that are associated with the parallel exponential growth and concentration of the global human population. Consequently, the concept of One Health must recognise the constantly evolving relationship between animals and humans and the planet they share.

A feasibility study for the establishment of a national wildlife health centre in Sri Lanka.

Sri Lanka is a tropical nation within a zoogeographic zone that is at high risk for infectious disease emergence. In 2010, a study was conducted on the feasibility of enhancing capacity in Sri Lanka to manage wildlife diseases through the establishment of a national wildlife health centre. The Canadian Cooperative Wildlife Health Centre was assessed as a potential model for adaptation in Sri Lanka. Interviews and group meetings were conducted with potential key participants from the Sri Lankan Departments of Wildlife Conservation and Animal Production and Health, and the Faculty of Veterinary Medicine and Animal Science of the University of Peradeniya. In addition, site visits were made to potentially participating facilities and the literature on best practices in building scientific capacity was consulted. With strategic enhancements in education and training, additional personnel, improvements in transportation and diagnostic facilities, and central coordination, Sri Lanka appears very well positioned to establish a sustainable wildlife health centre and programme.

Evidence of exposure to Brucella sp. in harbor porpoises (Phocoena phocoena) from the Bay of Fundy, Canada.

Novel strains of Brucella recently have been discovered in marine mammals. To investigate Brucella exposure and infection in a general population of cetaceans, blood and tissue samples were collected and analyzed from wild harbor porpoises (Phocoena phocoena) incidentally caught in fishing gear in the Bay of Fundy, Canada. Two of 170 (1.2%) animals had detectable antibodies against Brucella, but no organisms were isolated from genital swabs or tissues from 22 and 8 porpoises, respectively. Genetic analysis of inflamed testes from 20 animals yielded no amplification of Brucella DNA. This is the first evidence of exposure to Brucella in porpoises from the western North Atlantic, and the prevalence is much lower than documented for conspecifics from the eastern North Atlantic.

Massive mortality of common carp (Cyprinus carpio carpio) in the St. Lawrence River in 2001: diagnostic investigation and experimental induction of lymphocytic encephalitis.

A massive fish kill affecting exclusively common carp (Cyprinus carpio carpio) in the St. Lawrence River, Québec, Canada, during the summer of 2001 was investigated by use of laboratory diagnostic methods and by an attempt to experimentally induce the disease. The ultimate causes of mortality were opportunistic bacterial infections with Aeromonas hydrophila and Flavobacterium sp. secondary to immunosuppression induced by physiologic (i.e., spawning) and environmental (i.e., high temperatures and low water levels) stressors, and possibly enhanced by an infection causing lymphocytic encephalitis observed in 9 of 18 (50%) fish examined. Experimental induction of disease was attempted in captured wild carp by administration of crude and filtered (particulate <0.22 microm) inocula prepared from a homogenate of tissues from carp affected by the natural outbreak. Although significant clinical disease or mortality was not induced by experimental challenge, lymphocytic encephalitis similar to the one observed in naturally affected carp was induced in four of seven (57%) fish administered crude inoculum and four of seven (57%) fish administered filtered inoculum. None of the control fish inoculated with sterile phosphate-buffered saline (n = 6) were affected by encephalitis. The cause of the encephalitis observed in carp from the natural outbreak and in experimentally inoculated fish could not be determined by use of virus isolation and transmission electron microscopy.

[Wildlife and emerging diseases]. / La faune sauvage et les maladies émergentes.

This article reviews the conditions that allow an infectious or parasitic pathogen to migrate from a wild reservoir to domestic animals and/or humans, and examines the possibility of a new disease emerging as a result. The review presents epidemiological mechanisms grouped into three principal models, illustrating them with examples: the intentional or accidental release of the reservoir host or pathogen; the exceeding of a numerical, ecological or behavioural threshold in the host populations and/or increased exposure of humans and domestic animals due to changes in behaviour; and lastly, an "adaptive" leap that ensures that a new host species finally succumbs to the pathogen and that it spreads among the conquered population. The authors examine the lessons to be drawn from such occurrences in terms of surveillance, prophylaxis and prevention.

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.

Secondary poisoning of eagles following intentional poisoning of coyotes with anticholinesterase pesticides in western Canada.

Records of eagles, coyotes (Canis latrans), and red foxes (Vulpes vulpes) necropsied at the Western College of Veterinary Medicine, Saskatoon, Saskatchewan, Canada, between 1967 and 2002 were reviewed for cases suggestive of anticholinesterase poisoning. From 1993 to 2002, 54 putative poisoning incidents involving 70 bald eagles (Haliaeetus leucocephalus) and 10 golden eagles (Aquila chrysaetus) were identified. Of these, 50 incidents occurred in Saskatchewan, two were in Manitoba, and one occurred in each of Alberta and the Northwest Territories. The diagnosis was confirmed in eight instances by demonstration of pesticide in ingesta from eagles or known use of pesticide at the site together with brain cholinesterase (AChE) reduction of >50% in at least one animal. A presnmptive diagnosis of poisoning was made in 33 incidents based on brain AChE reduction of >50% in at least one animal; 13 incidents were considered suspicious because of circumstantial evidence of the death of eagles in association with other species and limited AChE reduction. Other wild species were found dead in 85% of the incidents involving eagles. Coyotes, foxes, black-billed magpies (Pica pica), and striped skunks (Mephitis mephitis) were associated with 34, six, six, and three incidents, respectively. There were eight additional incidents that did not involve eagles in which poisoning was diagnosed in coyotes. Carbofuran was identified in nine incidents. Carbamate poisoning was indicated on the basis of reactivation of brain AChE activity in two additional incidents. Brain AChE activity was not reduced from normal in eagles in four of seven incidents in which carbofuran was identified. The organophosplorous insecticide terbufos was found together with carbofuran in one incident. Brain AChE activity was measured in wild canids and in eagles in 15 incidents; in all of these incidents, brain AChE was redulced by >50% in at least one mammal, whereas this level of reduction occrred in eagles in only four incidents. Use of anticholinesterase pesticides to poison coyotes is illegal, but the practice continues and secondary poisoning of eagles is a problem of unknown proportions in western North America.

Antibodies to selected pathogens in free-ranging terrestrial carnivores and marine mammals in Canada.

Antibody titres to selected pathogens (canine adenovirus [CAV-2], feline herpesvirus [FHV], phocine herpesvirus [PHV-1], canine distemper virus, dolphin morbillivirus [DMV], phocine distemper virus [PDV], parainfluenza virus type 3 [PI3], rabies virus, dolphin rhabdovirus [DRV], canine coronavirus, feline coronavirus, feline leukaemia virus, Borrelia burgdorferi and Toxoplasma gondii) were determined in whole blood or serum samples from selected free-ranging terrestrial carnivores and marine mammals, including cougars (Fellis concolor), lynxes (Fellis lynx), American badgers (Taxidea taxus), fishers (Martes pennanti), wolverines (Gulo gulo), wolves (Canis lupus), black bears (Ursus americanus), grizzly bears (Ursus arctos), polar bears (Ursus maritimus), walruses (Odobenus rosmarus) and belugas (Delphinapterus leucas), which had been collected at several locations in Canada between 1984 and 2001. Antibodies to a number of viruses were detected in species in which these infections have not been reported before, for example, antibodies to CAV-2 in walruses, to PDV in black bears, grizzly bears, polar bears, lynxes and wolves, to DMV in grizzly bears, polar bears, walruses and wolves, to PI3 in black bears and fishers, and to DRV in belugas and walruses.

The role of wildlife in emerging and re-emerging zoonoses.

There are huge numbers of wild animals distributed throughout the world and the diversity of wildlife species is immense. Each landscape and habitat has a kaleidoscope of niches supporting an enormous variety of vertebrate and invertebrate species, and each species or taxon supports an even more impressive array of macro- and micro-parasites. Infectious pathogens that originate in wild animals have become increasingly important throughout the world in recent decades, as they have had substantial impacts on human health, agricultural production, wildlife-based economies and wildlife conservation. The emergence of these pathogens as significant health issues is associated with a range of causal factors, most of them linked to the sharp and exponential rise of global human activity. Among these causal factors are the burgeoning human population, the increased frequency and speed of local and international travel, the increase in human-assisted movement of animals and animal products, changing agricultural practices that favour the transfer of pathogens between wild and domestic animals, and a range of environmental changes that alter the distribution of wild hosts and vectors and thus facilitate the transmission of infectious agents. Two different patterns of transmission of pathogens from wild animals to humans are evident among these emerging zoonotic diseases. In one pattern, actual transmission of the pathogen to humans is a rare event but, once it has occurred, human-to-human transmission maintains the infection for some period of time or permanently. Some examples of pathogens with this pattern of transmission are human immunodeficiency virus/acquired immune deficiency syndrome, influenza A, Ebola virus and severe acute respiratory syndrome. In the second pattern, direct or vector-mediated animal-to-human transmission is the usual source of human infection. Wild animal populations are the principal reservoirs of the pathogen and human-to-human disease transmission is rare. Examples of pathogens with this pattern of transmission include rabies and other lyssaviruses, Nipah virus, West Nile virus, Hantavirus, and the agents of Lyme borreliosis, plague, tularemia, leptospirosis and ehrlichiosis. These zoonotic diseases from wild animal sources all have trends that are rising sharply upwards. In this paper, the authors discuss the causal factors associated with the emergence or re-emergence of these zoonoses, and highlight a selection to provide a composite view of their range, variety and origins. However, most of these diseases are covered in more detail in dedicated papers elsewhere in this Review.

Health risk assessment of the translocation of wild animals.

Potential health risks are always associated with the translocation of wild animals. A formal assessment of these health risks should be conducted in advance of each translocation, and the results of the risk assessment should be incorporated into decisions as to whether or not the translocation should occur or whether changes in the translocation protocol could substantially reduce health risks inherent in the translocation. Credible health risk assessments can be performed by individuals without extensive previous experience, given the necessary background in animal health and wildlife biology and access to sufficient valid information. Assessment of health risks should not be performed or influenced by those who will use the results to make decisions or those with vested interests in a particular outcome. The assessment process itself must be transparent, and the final risk assessment report must clearly present each step taken, all available information and all reasoning. Health risk assessment is a rigorous application of common sense to evaluate whether or not important health-related risks are associated with a proposed activity. The level of health risk inherent in a planned translocation is determined by identifying the full range of possible health hazards that might be associated with that translocation, identifying from among these a subset of potential hazards that require complete assessment, and for each hazard thus selected, evaluating the probability that the hazardous event will occur and the magnitude of negative consequences if it does occur. The combination of probability of occurrence and magnitude of consequences constitutes the risk posed by a potential health hazard, and the combined risk for each assessed health hazard constitutes the overall health risk estimate for the translocation. A valid numerical (quantitative) health risk assessment for wild animals is rarely possible because the available information on which the assessment must be based is too approximate and imprecise. Qualitative health risk assessments for wild animal translocations are usually of equal or greater value than numerical assessments and can be of enormous importance to wildlife conservation, domestic animal health and public health.

Assessment of biological effects of chlorinated hydrocarbons in osprey chicks.

Osprey (Pandion haliaetus) eggs were collected during 1995 and 1996 at seven sites along the Fraser and Columbia River systems of British Columbia, Canada, and Washington and Oregon, USA. Fifty-four eggs were placed into a laboratory incubator. Thirty-eight of the hatched chicks were sacrificed within 24 h. Hatching success did not differ among sites and therefore between treatment and reference areas. Residual yolk sacs of eggs collected downstream of the large bleached-kraft pulp mill at Castlegar contained greater mean concentrations of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, 2,930 ng/kg lipid) compared with reference sites such as the Nechako River, an upper tributary of the Fraser system (33.7 ng/kg). Total polychlorinated biphenyls (PCBs) in yolk sacs were also higher at Castlegar and in samples from the Columbia River downstream of Portland, Oregon, compared with those from the Nechako River. Concentrations of measured chemicals, including TCDD toxic equivalents (TEQs), total PCBs, p,p'-dichlorodiphenylethylene (p,p'-DDE), and other organochlorines were not different in eggs that failed to hatch compared with calculated whole-egg values for hatched eggs. There were significant biochemical responses; a hepatic cytochrome P4501A (CYP1A) cross-reactive protein was detected in all samples tested and correlated positively with ethoxyresorufin o-deethylase (EROD) activity and yolk sac concentrations of TEQs and total PCBs. Tissue concentrations of vitamin A compounds varied among sites and correlated positively with yolk sac concentrations of TEQs and PCBs. Morphological, histological, and other physiological parameters, including chick growth, edema, deformities, and hepatic and renal porphyrin concentrations, neither varied among sites nor showed concentration-related effects.

A serological survey of rural dogs and cats on the southwestern Canadian prairie for zoonotic pathogens.

A survey for antibodies against agents of plague, tularemia, and Rocky Mountain spotted fever (RMSF), and against Sin Nombre hantavirus (SNV), Bartonella henselae and B. clarridgeiae was conducted in the summer of 1995 using serum from rural dogs and cats living in the vicinity of four public parks in southeastern Alberta and southwestern Saskatchewan. Antibodies to all pathogens were detected in all survey areas. Overall prevalence rates were 0.075 for Yersinia pestis, 0.089 for Francisella tularensis, 0.025 for Rickettsia rickettsii (dogs only), and 0.029, 0.178 and 0.186 for SNV, B. henselae and B. clarridgeiae, respectively (cats only). This serological survey of rural dogs and cats was more sensitive and efficient than previous surveys based on collection and culture of rodents and ectoparasites. All six pathogens appear endemic to the region. Surveillance for plague, tularemia, RMSF and SNV, and management of associated public risks should be done in endemic regions.

Histology and ultrastructure of the chorioallantoic membrane of the mallard duck (Anas platyrhynchos).

The histology and fine structure of the chorioallantoic membrane of the mallard duck (Anas platyrhynchos), and the density of vessels per millimeter of membrane were assessed between days 12 and 24 of incubation. Light and transmission electron microscopy of the chorioallantoic membrane of the mallard duck after various days of incubation was carried out. Blood vessels within the mesoderm were counted per millimeter of membrane by light microscopy (40x). The chorioallantoic membrane had three distinct layers from day 12 to 24 of incubation, the chorionic epithelium, the mesoderm, and the allantoic epithelium. After day 12, chorionic epithelium consisted of two layers of flattened, elongated epithelial cells interfaced by numerous desmosomes, and separated from the underlying mesoderm by a basement membrane. At this stage, the allantoic epithelium consisted of a single layer of flattened, overlapping cells. Blood capillaries were observed in the mesoderm close to the chorionic epithelium on days 12 and 13; by day 14, these capillaries were located within the chorionic epithelium, forming a capillary sinus. Between days 14 and 16, the chorion underwent cellular and cytological differentiation into three cell types: capillary covering cells, villus cavity cells, and less differentiated basal cells. The mesoderm was composed of a loose matrix of mesenchymal cells and collagen fibrils through which coursed blood and lymphatic vessels. The vascular density in the mesoderm increased rapidly from 4.2+/-0.6 vessels per mm (n = 12) on day 12 to a maximum of 9.4+/-0.3 vessels per mm (n = 15) by day 16. From day 16, the allantoic epithelium had two to three layers of elongated and overlapping cells. The luminal layer of allantoic epithelial cells had microvillus projections and varying numbers of membrane-bound dense vesicles at all stages from day 12 onward. The histologic and ultrastructural features of mallard duck chorioallantoic membrane from day 12 to 24 of incubation were very similar to those described in the chorioallantoic membrane of the chicken (Gallus gallus) from day 8 to 20 of incubation. Much of the information available concerning the CAM of the chicken also may apply to the CAM of the mallard, with timing adjusted to match the developmental time-frame recorded here.

Causes of morbidity and mortality and their effect on reproductive success in double-crested cormorants from Saskatchewan.

The objectives of this study were to describe causes of morbidity and mortality in a breeding colony of double-crested cormorants (Phalacrocorax auritus) on Doré Lake (Saskatchewan, Canada), and to determine cause-specific mortality rates of juvenile birds. Morbidity and mortality were monitored every third day during the breeding season from 1994 to 1996 from inside a tunnel-and-blind system. Affected eggs and birds were collected for examination and diagnosis. The cause of mortality was determined for 105 eggs, 178 nestlings (< or = 4-wk-old), 1393 post-nestling chicks (> 4-wk-old), and 10 adults. The main causes of mortality were infertility or embryonal death, avian predation, displacement of eggs and chicks from the nest, starvation from sibling competition, Newcastle disease, coyote predation, human-induced suffocation, and entrapment. In 49% of the cases, avian predation and displacement from the nest of eggs or nestlings was associated with human disturbance. Thirty-six nestlings, 40 post-nestling chicks, and three adults were examined for the presence of parasites. Contracaecum spiculigerum was found in the proventriculus; Amphimerus elongatus in the liver. Piagetiella incomposita in the gular pouch; Eidmanniella pellucida, Pectinopygus farallonii, and Ceratophyllus lari in the plumage; and Theromyzon sp. in the nasal and oral cavity. Contracaecum spiculigerum was associated with ulcerative gastritis, A. elongatus with multifocal hepatitis and bile duct hyperplasia, and P. incomposita with ulcerative stomatitis, but these lesions were not considered fatal. Other diseases included beak deformity, abnormal rotation of the carpal joint, hypopigmentation, and eye loss. Overall mortality of cormorant chicks between hatching and the end of the breeding season varied from 25 to 48%. The most important causes of mortality were Newcastle disease, which killed 21% of hatched chicks in 1995, sibling competition (maximum 12% in 1994), and coyote predation (2% in 1994).

Pathology of Newcastle disease in double-crested cormorants from Saskatchewan, with comparison of diagnostic methods.

Newcastle disease (ND) in juvenile double-crested cormorants (Phalacrocorax auritus) occurred several times since 1975, but there are relatively few studies on its pathology and diagnosis. In order to describe the distribution of Newcastle disease virus (NDV) and associated lesions in cormorants with ND and to compare diagnostic methods, 25 cormorants with nervous signs from a ND epizootic in Saskatchewan in 1995 (NDE cormorants) were compared with 18 negative control cormorants. Tissues of these birds were examined by necropsy, histology, virus isolation, immunohistochemistry, serology, and reverse transcriptase-polymerase chain reaction (RT-PCR) methods. The NDE cormorants had a characteristic non-suppurative encephalomyelitis, with a significantly higher prevalence of neuronal necrosis, gliosis, perivascular infiltration with mononuclear cells, and endothelial hypertrophy than control cormorants. These lesions were found more frequently in the cerebellum and brain stem than in other parts of the central nervous system. Immunohistochemically, NDV antigen was limited to neurons, glial and endothelial cells in the central nervous system, and to tubular epithelial cells in the kidney. Newcastle disease virus was isolated with the highest prevalence (4/5) and the highest concentration (10(4.8) ELD50/g) from the kidney. The virus isolates often did not agglutinate erythrocytes in the standard hemagglutination test; the presence of NDV was confirmed by use of an indirect immunoperoxidase assay. By RT-PCR, NDV was detected in kidney and jejunum of a NDE cormorant. There was no significant difference between sensitivity of histology, virus isolation, and serology for detecting ND in NDE cormorants.