Mycobacterium tuberculosis infection in a dog from Africa

A 4-year-old male Boxer dog with a history of vomiting, diarrhea, and weight loss moved from West Africa to Lyon, France, where it was further evaluated. Radiographs revealed pleural effusion and enlargement of tracheobronchial lymph nodes and liver. Cytologic examination of the pleural effusion and a fine needle aspirate specimen of the liver showed mixed mononuclear inflammation with nonstaining rod structures within epithelioid histiocytes. At necropsy, the main gross pathologic findings were exudative pleuritis, nodular hepatitis, and infarcts and caseous nodules in the kidneys. The main histologic lesions were granulomatous hepatitis, granulomatous pneumonia, fibrinous leukocytic pleuritis, necrotic and fibro-calcified granulomatous lymphadenitis, and granulomatous nephritis. A Ziehl-Neelsen stain applied to both cytologic and histologic samples was positive for acid-fast bacilli. Bacterial culture of the pleural fluid was positive for Mycobacterium tuberculosis. Cytology is a valuable tool in the diagnosis of this important zoonotic disease.     

Localised Mycobacterium ulcerans infection in four dogs

Localised infection caused by Mycobacterium ulcerans is described in two Kelpies, a Whippet and a Koolie domiciled on the Bellarine Peninsula, Victoria, Australia. The diagnosis was confirmed using real-time polymerase chain reaction (PCR) targeting the M. ulcerans-specific insertion sequence (IS2404) in DNA extracted from swabs of ulcerated lesions in all cases. Where available, molecular typing confirmed that three of the dogs were infected with a strain of M. ulcerans that was indistinguishable from a disease-causing strain in people and other animals in Victoria. One dog was still undergoing treatment at the time of writing, but the remaining three dogs were successfully treated with a combination of surgical debridement and medical therapy in one case, and medical therapy alone in the other two. Investigation of the home environs of three of the dogs using real-time PCR revealed low amounts of M. ulcerans DNA in various environmental samples. Mycobacterium ulcerans infection should be included in the differential diagnoses of any ulcerated skin lesions in dogs that live in or visit endemic areas of Victoria and Queensland.     

The pathology of Mycobacterium tuberculosis infection

Mycobacterium tuberculosis is an old enemy of the human race, with evidence of infection observed as early as 5000 years ago. Although more host-restricted than Mycobacterium bovis, which can infect all warm-blooded vertebrates, M. tuberculosis can infect, and cause morbidity and mortality in, several veterinary species as well. As M. tuberculosis is one of the earliest described bacterial pathogens, the literature describing this organism is vast and overwhelming. This review strives to distill what is currently known about this bacterium and the disease it causes for the veterinary pathologist.     

Mycobacterium bovis infection and tuberculosis in cattle

This review considers the possible events that can occur when cattle are exposed to Mycobacterium bovis and, where appropriate, draws on principles accepted for tuberculosis infection in humans and laboratory animal models. Consideration is given to the many complex factors which influence the outcome of challenge with tubercle bacilli. These include features inherent to the mycobacterium, the host and the environment. It is apparent that clinical disease probably occurs only in a relatively small, but undetermined, proportion of cattle that are exposed to Al. bovis. The majority of animals may clear infection or control the bacilli, possibly in a condition of latency. It is concluded that a better understanding of the dynamics of the events following M. bovis exposure and subsequent infection in cattle would be of significant benefit in developing new tools appropriate for disease control and to designing optimal approaches for their application.     

PCR for detection of Mycobacterium tuberculosis in experimentally infected dogs

The susceptibility of dogs to infection with Mycobacterium tuberculosis was studied through different ways of experimental infection. The examination shows, that in most cases the disease runs subclinically with pathological changes localized mainly in the lungs, lymph nodes, small intestines, liver, kidneys and spleen. Histological findings demonstrate granulomatous inflammation with caseosation and predominance of epitheloide macrophages and single lymphocytes. Tissue samples from internal organs of experimentally infected dogs as well as non-infected but contact animals were investigated by direct PCR. Specific PCR-products were obtained in 44 of 96 studied samples. Eighty-three (86.5%) of PCR results coincided with bacteriological finds, 82 (85.4%) with the pathological and 71 (74.0%) simultaneously with bacteriological and pathological results. The observed specific DNA products in tissue samples of infected and non-infected dogs demonstrate significant sensitivity of PCR method. It could be assumed that the transmission of M. tuberculosis infection is possible by close contact between ill and healthy dogs and that the naturally infected dogs or dogs suffering from tuberculosis may serve as a permanent source of infection to humans and other animals.     

结核分枝杆菌rv0199基因在耻垢分枝杆菌中的表达及检测

为研究结核分枝杆菌（M.tb）rv0199基因在该病原致病性中可能发挥的作用,本研究克隆了rv0199基因,在耻垢分枝杆菌（Ms）中异源表达,并对其表达进行检测。将大肠杆菌-分枝杆菌穿梭表达载体pMV261进行改造,向载体中引入常用的6His和Strep Ⅱ重组蛋白标签,命名为pMV262。使用Ms/pMV262表达系统对rv0199基因进行超表达,用抗6His标签抗体和抗Strep Ⅱ标签抗体均能特异的检测到重组蛋白。本试验改造的pMV262穿梭表达载体可很方便的检测M.tb的基因在Ms中的异源表达,不用制备针对蛋白的多克隆抗体或单克隆抗体。构建的重组菌Ms/262-99为进一步研究rv0199基因的功能提供了材料,奠定了基础。     

Putative transmission of Mycobacterium tuberculosis infection from a human to a dog

A 3.5-year-old Yorkshire Terrier was evaluated for anorexia and vomiting; infection with Mycobacterium tuberculosis was diagnosed by use of histology, bacteriologic culture, and polymerase chain reaction (PCR) assay on various tissues. The dog was living with a human with an established M. tuberculosis infection. Findings were unique in that diagnosis of M. tuberculosis infection was obtained via PCR techniques, and isolates from the owner and dog were matched via restriction fragment length polymorphism fingerprinting. Dogs infected with M. tuberculosis from humans are most commonly infected via the respiratory tract. Clinical signs in dogs are variable and depend on the integrity of the immune system and the degree of dissemination. Diagnosis can often be obtained through histopathology and bacteriologic culture; additional diagnostic techniques are also available. Treatment of a dog with confirmed M. tuberculosis infection is controversial, and at least 6 months of multidrug treatment is required.     

Mycobacterium tuberculosis infection in grazing cattle in central Ethiopia

A preliminary study to characterise mycobacteria infecting tuberculous cattle from two different management systems in central Ethiopia was carried out. Approximately 27% of isolates from grazing cattle were Mycobacterium tuberculosis, while cattle in a more intensive-production system were exclusively infected with M. bovis. The practice of local farmers discharging chewed tobacco directly into the mouths of pastured cattle was identified as a potential route of human-to-cattle transmission of M. tuberculosis.     

Pulmonary Mycobacterium tuberculosis (Beijing strain) infection in a stray dog

Mycobacterium tuberculosis infection in dogs is rarely reported and has not previously been documented in South Africa. A case of a stray Maltese crossbreed dog with extensive multifocal pulmonary tuberculosis due to M. tuberculosis is described. Pulmonary granulomas in this case were poorly encapsulated and contained large numbers of acid-fast bacteria, highlighting the potential for infected companion animals to excrete the pathogen. Treatment of canine tuberculosis is generally not advised, and for this reason, euthanasia of diseased animals must be advocated in most instances. Physicians and veterinarians must be aware that companion animals with active disease caused by M. tuberculosis could act as a potential source of infection.     

Outbreak of Mycobacterium tuberculosis infection among captive Asian elephants in a Swedish zoo

Between 2001 and 2003, there was an outbreak of tuberculosis in a Swedish zoo which involved elephants, giraffes, rhinoceroses and buffaloes. Cultures of trunk lavages were used to detect infected elephants, tuberculin testing was used in the giraffes and buffaloes, and tracheal lavage and tuberculin testing were used in the rhinoceroses. The bacteria isolated were investigated by spoligotyping and restriction fragment length polymorphism. Five elephants and one giraffe were found to have been infected by four different strains of Mycobacterium tuberculosis.     

Diagnostic and public health investigation of Mycobacterium tuberculosis infection in a dog in Ontario,Canada

A 4-y-old, female mixed-breed dog was presented to the Ontario Veterinary College for further evaluation of multiple pulmonary and hepatic masses, intrathoracic lymphadenitis, and recent development of a pyogranulomatous pleural effusion. Along with other comprehensive tests, a thoracic lymph node biopsy was performed, and Mycobacterium tuberculosis complex infection was confirmed by real-time PCR. The dog’s condition declined post-operatively, and euthanasia was elected. Postmortem examination confirmed severe granulomatous pneumonia, hepatitis, intrathoracic and intraabdominal lymphadenitis, omentitis, and nephritis. Line-probe assays performed on samples collected postmortem confirmed the species as M. tuberculosis. 24-loci MIRU-VNTR genotyping, spoligotyping, and whole-genome sequencing revealed relations to known human isolates, but no epidemiologic link to these cases was investigated. Given the concern for potential human exposure during this animal’s disease course, a public health investigation was initiated; 45 individuals were tested for M. tuberculosis exposure, and no subsequent human infections related to this animal were identified. Our case highlights the need for more readily available, minimally invasive testing for the diagnosis of canine mycobacteriosis, and highlights the ability of canid species to act as potential contributors to the epidemiology of M. tuberculosis infections.     

Accidental infection of veterinary personnel with Mycobacterium tuberculosis at necropsy: a case study

Mycobacterium tuberculosis is the main cause of human tuberculosis. Infection in companion animals is mainly acquired from close contact to a diseased human patient and hence rarely diagnosed in countries with low tuberculosis incidence rates. Therefore the general awareness of the disease might be low. Here we report the potential risk of infection for veterinary personnel with M. tuberculosis during the clinical and pathological examination of a dog with unexpected disseminated tuberculosis. The dog had presented with symptoms of a central nervous system disease; rapid deterioration prevented a complete clinical workup, however. Post-mortem examination revealed systemic mycobacteriosis, and M. tuberculosis was identified by PCR amplification of DNA extracts from paraffin-embedded tissue sections and spoligotyping. Contact investigations among the owners and veterinary personnel using an IFN-γ release assay indicated that the index dog did not infect humans during its lifetime. Serological and IFN-γ release assay results of one of two cats in direct contact with the index dog, however, suggested that transmission of M. tuberculosis might have occurred. Importantly, all three pathologists performing the necropsy on the dog tested positive. Accidental infection was most likely due to inhalation of M. tuberculosis containing aerosols created by using an electric saw to open the brain cavity. As a consequence routine necropsy procedures have been adapted and a disease surveillance program, including tuberculosis, has been initiated. Our results highlight the importance of disease awareness and timely diagnosis of zoonotic infectious agents in optimizing work safety for veterinary personnel.     

Mycobacterium infection in a gray-cheeked parakeet

A gray-cheeked parakeet, approximately 3 years of age, was submitted for necropsy. Clinical signs included diarrhea, decreased feed consumption, fluffing of feathers, shivering, weight loss, and limping. Necropsy revealed enlargement and pale discoloration of the spleen and intestines. The liver contained multifocal pale foci. Granulomas, some of which had necrotic centers, were present along the subserosa of the intestinal tract. Microscopic examination revealed diffuse granulomatous splenitis, enteritis, and multifocal granulomatous hepatitis. Numerous acid-fast bacteria were demonstrated in the spleen, liver, and intestine.     

Mycobacterium avium infection in a dog

A 5-year old, spayed, mongrel was presented with intractable diarrhoea. Histopathologic examination of biopsy specimens taken during exploratory laparotomy revealed acid-fast organisms in the spleen, caecum, and colon. The dog was subsequently destroyed. At post-mortem, lesions were also observed in the liver and lymph nodes. Mycobacterium avium was cultured from splenic tissue. Infection of dogs with this organism is rare and the clinical picture described unusual.