Respiratory tract infection caused by Mycobacterium bovis in a black swan (Cygnus atratus)

A 3-year-old male black swan (Cygnus atratus), belonging to a private collection, died suddenly and was subjected to post mortem examination. At necropsy, caseous exudate was observed in the lungs and air sacs; granulomatous lesions characterized by epithelioid macrophages and abundant mycobacteria were observed microscopically. Avian tuberculosis associated with Mycobacterium bovis was confirmed by bacteriologic isolation, biochemical tests and molecular methods. The organism was identified as spoligotype SB0140, which is frequently found in cattle and people in North America. In this case, interspecies transmission could have been the source of infection because the swan cohabited with cattle.

Mycobacterium bovis (bovine tuberculosis) infection in North American wildlife: current status and opportunities for mitigation of risks of further infection in wildlife populations

Mycobacterium bovis (M. bovis), the causative agent of bovine tuberculosis, has been identified in nine geographically distinct wildlife populations in North America and Hawaii and is endemic in at least three populations, including members of the Bovidae, Cervidae, and Suidae families. The emergence of M. bovis in North American wildlife poses a serious and growing risk for livestock and human health and for the recreational hunting industry. Experience in many countries, including the USA and Canada, has shown that while M. bovis can be controlled when restricted to livestock species, it is almost impossible to eradicate once it has spread into ecosystems with free-ranging maintenance hosts. Therefore, preventing transmission of M. bovis to wildlife may be the most effective way to mitigate economic and health costs of this bacterial pathogen. Here we review the status of M. bovis infection in wildlife of North America and identify risks for its establishment in uninfected North American wildlife populations where eradication or control would be difficult and costly. We identified four common risk factors associated with establishment of M. bovis in uninfected wildlife populations in North America, (1) commingling of infected cattle with susceptible wildlife, (2) supplemental feeding of wildlife, (3) inadequate surveillance of at-risk wildlife, and (4) unrecognized emergence of alternate wildlife species as successful maintenance hosts. We then propose the use of integrated and adaptive disease management to mitigate these risk factors to prevent establishment of M. bovis in susceptible North American wildlife species.

On-farm mitigation of transmission of tuberculosis from white-tailed deer to cattle: literature review and recommendations

The Animal Industry Division of the Michigan Department of Agriculture and Rural Development (MDARD) has been challenged with assisting farmers with modifying farm practices to reduce potential for exposure to Mycobacterium bovis from wildlife to cattle. The MDARD recommendations for on-farm risk mitigation practices were developed from experiences in the US, UK and Ireland and a review of the scientific literature. The objectives of our study were to review the present state of knowledge on M. bovis excretion, transmission, and survival in the environment and the interactions of wildlife and cattle with the intention of determining if the current recommendations by MDARD on farm practices are adequate and to identify additional changes to farm practices that may help to mitigate the risk of transmission. This review will provide agencies with a comprehensive summary of the scientific literature on mitigation of disease transmission between wildlife and cattle and to identify lacunae in published research.

The role of wildlife in transboundary animal diseases

This paper identifies some of the more important diseases at the wildlife-livestock interface and the role wildlife plays in disease transmission. Domestic livestock, wildlife and humans share many similar pathogens. Pathogens of wild or domestic animal origin that can cause infections in humans are known as zoonotic organisms and the converse are termed as anthroponotic organisms. Seventy-seven percent of livestock pathogens and 91% of domestic carnivore pathogens are known to infect multiple hosts, including wildlife. Understanding this group of pathogens is critical to public health safety, because they infect a wide range of hosts and are most likely to emerge as novel causes of infection in humans and domestic animals. Diseases at the wildlife-livestock interface, particularly those that are zoonotic, must be an area of focus for public health programs and surveillance for emerging infectious diseases. Additionally, understanding wildlife and their role is a vital part of understanding the epidemiology and ecology of diseases. To do this, a multi-faceted approach combining capacity building and training, wildlife disease surveillance, wildlife-livestock interface and disease ecology studies, data and information sharing and outbreak investigation are needed.

Non-West Nile virus-associated mortality in a population of American crows (Corvus brachyrhynchos): a gross and histopathologic study

The American crow (Corvus brachyrhynchos) is a common urban and rural inhabitant of the Northeast and Midwest United States that is commonly infected with West Nile virus (WNV). The current study was initiated to determine non-WNV-associated causes of mortality in the American crow. All animals (40/40) tested negative for WNV infection via polymerase chain reaction and had no evidence of infection based on immunohistochemistry. Common gross necropsy findings included external trauma (6/40), hepatosplenomegaly (6/40), poxviral dermatitis (5/40), and pneumonia (3/40). Common histologic findings included endoparasitism (32/40), multifocal hepatic and splenic necrosis (7/40), pigment accumulation in the spleen (5/40), and disseminated bacterial infection (3/40). The most significant and debilitating diseases included fungal pneumonia and poxvirus-associated lesions. The present report increases the knowledge of diseases present in the American crow population.

Use and husbandry of captive European starlings (Sturnus vulgaris) in scientific research: a review of current practice

Summary

We reviewed the use of captive European starlings ( Sturnus vulgaris) in scientific research published between 2000 and 2004. We estimated the numbers of birds used and documented their origin and the range of husbandry regimes employed with the aim of comparing current practice with the new European guidelines for husbandry of laboratory animals. Over the five-year period, 106 primary articles report the use of an estimated total of 2490 captive starlings. The majority of birds were caught from the wild either as adults or fledglings, and only 3% were hand-reared from chicks. There was considerable variation in husbandry. In the majority of cases, standards fell below those currently recommended as best practice in the UK and cited in new European guidelines. The median volume of home cages employed was 0.42 m3 (0.13–5.1 m3, interquartile range), whereas current recommendations suggest a minimum of 1.0 m3 for a singly-housed bird. The median volume of space allowed per bird was 0.13 m3/bird (0.08–1.05 m3/bird, Q1–Q3), whereas current recommendations suggest a minimum of 0.33 m3/bird. Only 27% of the articles mentioned providing any form of environmental enrichment for birds in their home cages. We recommend that more research be conducted into the welfare of starlings to inform legislation and guidelines, and thus maximize the welfare of captive animals.

Disseminated mycobacteriosis in a bald eagle (Haliaeetus leucocephalus)

A mature bald eagle (Haliaeetus leucocephalus) was diagnosed with mycobacterial infection after being presented for an inability to fly, emaciation, and a swelling of the left tibiotarsal-tarso metatarsal joint. Results of a complete blood cell count revealed a persistent, marked leukocytosis, with heterophilia, monocytosis, and anemia. Radiographs revealed lysis of the left distal tibiotarsus and soft-tissue swelling around the left tibiotarsal-tarsometatarsal joint, multiple pulmonary opacities, and an enlarged liver. Endoscopic evaluation and biopsy of caseated material within the left caudal coelom revealed acid-fast organisms. The eagle was euthanatized, and results of necropsy and histologic evaluation revealed caseated granulomas of the intestine, lungs, air sacs, and subcutaneous regions of the hock. Results of culture, a polymerase chain reaction testing, and direct deoxyribonucleic acid (DNA) sequencing for mycobacterial 16S ribosomal ribonucleic acid DNA determined this organism most likely to be Mycobacterium avium.

Experimental Inoculation of Wild Turkeys (Meleagris gallopavo) with Mycobacterium bovis

Although avian species are known to be susceptible to infection with Mycobacterium spp. organisms, much remains unknown about the susceptibility of birds to infection with M. bovis. The objective of this current study was to determine if wild turkeys (Meleagris gallopavo) can be infected with M. bovis when inoculated by the oral or intratracheal route. Six turkeys were orally inoculated and another six were inoculated via the trachea with a high dose of M. bovis, 1 x 10(5) CFU/ml. Six turkeys were sham-inoculated controls. Two turkeys from each treatment group were sacrificed on days 30, 60, and 90 postinoculation. There were no gross or microscopic lesions consistent with mycobacteriosis in the 23 inoculated turkeys over the 90-day duration of this study. Fecal cultures were also consistently negative for M. bovis when sampled before inoculation and on days 1, 30, and 60 postinoculation. Two intratracheally inoculated turkeys were positive for M. bovis in visceral tissues at 30 days postinoculation. However, this finding was only indicative of passive persistence of mycobacteria in the tissues and not of infection, as there were no attendant lesions or clinical compromise to support infection. Thus, it can be concluded that young wild turkeys are resistant to infection with M. bovis and, therefore, pose minimal threat as reservoir or spillover hosts for this organism.

Managing the wildlife reservoir of Mycobacterium bovis: The Michigan, USA, experience

Historical, social and economic factors combined to provide a focus where bovine tuberculosis has become established in free-ranging wildlife in northeastern lower Michigan. White-tailed deer, the primary reservoir and maintenance host of tuberculosis, are highly valued by the public, and particularly hunters, for cultural and economic reasons. Since 1995, significant progress has been made in defining and reducing the reservoir of tuberculosis in deer. As yet, no other wildlife species has been shown to play an epidemiologically important role in the disease cycle. The importance of deer and deer hunting to Michigan has uniquely shaped tuberculosis control policies, and poses ongoing challenges as wildlife managers strive to maintain momentum for broad control strategies, and develop focused strategies that are publicly acceptable. Even if momentum and funding can be maintained, tuberculosis will likely continue to be present for a decade or longer. Thus, cattle producers waiting for tuberculosis to be eradicated from wildlife to eliminate risks to their herds and markets face disappointment for the foreseeable future. Such unrealistic expectations also place Michigan's federal tuberculosis accreditation status at perpetual risk. Accredited free status is unlikely to be regained without accompanying changes in cattle management. In Michigan, management of tuberculosis has clearly demonstrated that social issues and public approval are likely to be the critical limiting factors in control.

Resistance of Mallard ducks (Anas platyrhynchos) to experimental inoculation with Mycobacterium bovis

The purpose of this study was to investigate whether mallard ducks (Anas platyrhynchos) are susceptible to infection with Mycobacterium bovis by either oral or intratracheal inoculation and to assess their potential role in the spread of bovine tuberculosis. Six ducks were orally inoculated with 1.0 x 10(5) colony-forming units of M. bovis, six ducks were intratracheally inoculated with the same dose, and six ducks served as sham-inoculated controls. The study length was 90 days postinoculation, with samples of two birds from each group necropsied at 30-day intervals. Both fecal and tissue samples were collected for mycobacterial culture. None of the inoculated ducks shed M. bovis in their feces at any culture point (days 1, 30, and 60) during the study. No evidence of illness or weight loss was present during the course of the study, and only one duck had M. bovis isolated from any tissue, although there were no associated microscopic lesions. Mallard ducks were highly resistant to infection with M. bovis following high-dose inoculation and did not shed the organism in their feces. This study was conducted using high-dose inoculation; therefore, it appears that ducks are unlikely to play any significant role in the transmission of M. bovis between infected and uninfected mammalian hosts.

Experimental inoculation of pigeons (Columba livia) with Mycobacterium bovis

The purpose of this pilot study was to determine if pigeons (Columba livia) are susceptible to infection with Mycobacterium bovis by either oral or intratracheal inoculation and to assess their possible role in the lateral transmission of bovine tuberculosis. Six pigeons were orally inoculated with 1.3 x 10(5) colony-forming units of M. bovis, six pigeons were intratracheally inoculated with the same dose, and six pigeons served as noninoculated controls. The study continued for 90 days postinoculation (PI), with groups of birds necropsied at 30-day intervals, and fecal samples and tissues were collected for mycobacterial culture. Two pigeons, one intratracheally inoculated and one orally inoculated, shed M. bovis in their feces at 1 day PI, and one intratracheally inoculated bird shed M. bovis in its feces 60 days PI. Whereas no illness or weight loss was present during the course of the study, 2 of 12 inoculated birds exhibited microscopic lesions of mycobacteriosis, and the organism was isolated from tissues of three inoculated birds. Pigeons are susceptible to infection with M. bovis after high dose inoculation and can shed the organism in their feces for up to 60 days PI; intratracheally inoculated birds appear more likely to become active fecal shedders of M. bovis. Although these were high dose inoculations under experimental conditions, pigeons may potentially play a role in the lateral transmission of bovine tuberculosis between infected and uninfected mammalian hosts.