Development of a Model of Natural Infection With Mycobacterium Bovis in White-Tailed Deer

Abstract

The objective of this study was to develop a suitable experimental model of natural Mycobacterium bovis infection in white-tailed deer (Odocoileus virginianus), describe the distribution and character of tuberculous lesions, and to examine possible routes of disease transmission. In October 1997, 10 mature female white-tailed deer were inoculated by intratonsilar instillation of 2 x 10(3) (low dose) or 2 x 10(5) (high dose) colony forming units (CFU) of M. bovis. In January 1998, deer were euthanatized, examined, and tissues were collected 84 to 87 days post inoculation. Possible routes of disease transmission were evaluated by culture of nasal, oral, tonsilar, and rectal swabs at various times during the study. Gross and microscopic lesions consistent with tuberculosis were most commonly seen in medial retropharyngeal lymph nodes and lung in both dosage groups. Other tissues containing tuberculous lesions included tonsil, trachea, liver, and kidney as well as lateral retropharyngeal, mandibular, parotid, tracheobronchial, mediastinal, hepatic, mesenteric, superficial cervical, and iliac lymph nodes. Mycobacterium bovis was isolated from tonsilar swabs from 8 of 9 deer from both dosage groups at least once 14 to 87 days after inoculation. Mycobacterium bovis was isolated from oral swabs 63 and 80 days after inoculation from one of three deer in the low dose group and none of four deer in the high dose group. Similarly, M. bovis was isolated from nasal swabs 80 and 85 days after inoculation in one of three deer from the low dose group and 63 and 80 days after inoculation from two of four deer in the high dose group. Intratonsilar inoculation with M. bovis results in lesions similar to those seen in naturally infected white-tailed deer; therefore, it represents a suitable model of natural infection. These results also indicate that M. bovis persists in tonsilar crypts for prolonged periods and can be shed in saliva and nasal secretions. These infected fluids represent a likely route of disease transmission to other animals or humans.

Diagnostic Implications of Antigen-Induced Gamma Interferon Production by Blood Leukocytes from Mycobacterium bovis -Infected Reindeer ( Rangifer tarandus )

“…Specimens for bacteriologic culture were placed individually in sterile bags and stored at Ϫ80°C until processing. Specimens were processed as previously described (19). Mycobacterial isolates were identified using standard growth and biochemical characteristics.…”

“…Castrated male reindeer (Rangifer tarandus; n ϭ 17) were obtained from a tuberculosis-free herd in southern Michigan and were housed at the National Animal Disease Center [NADC], USDA, ARS, Ames, Iowa, according to institutional guidelines and approved animal care and use protocols. For M. bovis infection, the challenge inoculum (10 5 CFU in 0.2 ml of phosphate-buffered saline, 0.15 M, pH 7.2 [PBS]) was instilled directly into the tonsillar crypts of anesthetized reindeer (n ϭ 13) as described previously for inoculation of white-tailed deer (19). The strain of M. bovis used for the challenge inoculum (95-1315; USDA APHIS designation) was originally isolated from a white-tailed deer in Michigan (24).…”

Experimentally Induced Infection of Reindeer (Rangifer Tarandus) with Mycobacterium Bovis

“…Grossly and microscopically, lesions resembled those seen in reindeer and those previously reported in naturally and experimentally infected whitetailed deer. 12,13 …”

“…Thirteen reindeer were experimentally inoculated by intratonsilar instillation of 10 5 colony-forming units (CFU) of M. bovis strain 1315 as described. 12 Strain 1315 was originally isolated from a white-tailed deer in Michigan in 1995. Reindeer were housed 2-3/pen; each pen was approximately 16 m 2 and was located inside a biosafety level-3 (BL-3) building with directional airflow to prevent room-to-room transfer of air.…”

“…Processing of specimens was done as described. 12 Mycobacterial isolates were identified using standard growth and biochemical characteristics. Isolates were confirmed to belong to the M. tuberculosis complex by results of gene probe analysis.…”