Location: Infectious Bacterial Diseases ResearchTitle: Pulmonary disease due to Mycobacterium tuberculosis in a horse: zoonotic concerns and limitations of antemortem testing) Author
Submitted to: Veterinary Medicine International
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/3/2012
Publication Date: 4/10/2012
Citation: Lyashchenko, K.P., Greenwald, R., Esfandiari, J., Lecu, A., Waters, W.R., Posthaus, H., Bodmer, T., Janssens, J., Aloisio, F., Graubner, C., Grosclaude, E., Piersigilli, A., Schiller, I. 2012. Pulmonary disease due to Mycobacterium tuberculosis in a horse: zoonotic concerns and limitations of antemortem testing. Veterinary Medicine International [serial online]. 2012:Article 642145. Available: http://www.hindawi.com/journals/vmi/2012/642145/. Interpretive Summary: Bovine tuberculosis primarily affects cattle and several wildlife reservoirs of the disease. Horses are rarely diagnosed with tuberculosis. Prior to highly successful control efforts within the US and continental Europe, the primary cause of tuberculosis in horses was Mycobacterium bovis, the causative agent of bovine tuberculosis. In the present study, we describe a case of tuberculosis in a horse caused by Mycobacterium tuberculosis, the primary cause of tuberculosis in humans. Epidemiological investigation of this case identified multiple species of farm animals and pets exposed to the horse as well as many humans. Also, the use of serology for diagnosis of tuberculosis in this horse is described. These findings highlight the risk to humans of tuberculosis in horses and difficulties in diagnosing this disease.
Technical Abstract: A case of pulmonary tuberculosis caused by Mycobacterium tuberculosis was diagnosed in a horse. Clinical evaluation performed prior to euthanasia did not suggest tuberculosis, but postmortem examination provided pathological and bacteriological evidence of disease. In the lungs, multiple tuberculoid granulomas communicating with the bronchiolar lumen, pleural effusion, and a granulomatous lymphadenitis involving mediastinal and tracheobronchial lymph nodes were found. Serologic response to M. tuberculosis antigens was detected in the infected horse, but not in the group of 42 potentially exposed animals (18 horses, 14 alpacas, 6 donkeys, and 4 dogs) which showed no signs of disease. Diagnosis of tuberculosis in live horses remains extremely difficult. Four of 20 animal handlers at the farm were positive for tuberculous infection upon follow-up testing by interferon-gamma release assay, indicating a possibility of interspecies transmission of M. tuberculosis.