Experimental Mycobacterium bovis infection in the brushtail possum (Trichosurus vulpecula): pathology, haematology and lymphocyte stimulation responses.
Groups of adult male brushtail possums (5 per group) were inoculated intratracheally with a high (2 x 10(5) colony forming units (cfu)), medium (2 x 10(3) cfu) or low (approximately 20 cfu) dose of Mycobacterium bovis. Two sham-inoculated groups acted as in-contact controls or controls kept in a separate room. Possums in the high and medium dose groups became clinically affected 3-5 weeks post-inoculation (PI) and all possums were euthanased between 5-9 weeks PI. Grossly visible tuberculous lesions were found in the lungs and associated lymph nodes of all possums from the high, medium and low dose groups. No lesions were observed in possums from the two control groups. Histopathologically, two characteristic types of lesions were observed; microscopic aggregates of macrophages with few acid-fast organisms, and larger lesions with limited granulomatous reaction, extensive necrosis and the presence of numerous acid-fast organisms. M. bovis was isolated from the lungs and lymph nodes of all of the possums from the high, medium and low dose groups and from the lungs of one of the in-contact controls. Changes in the haematological profile of the M. bovis-inoculated possums included lymphocytopaenia and eosinopaenia, together with raised fibrinogen levels. The onset of these changes was dependent on the size of the challenge dose. Lymphocyte stimulation responses to M. bovis tuberculin purified protein derivative were detected in 14 of 15 M. bovis-inoculated possums.
AgResearch, Wallaceville Animal Research Centre, Upper Hutt, New Zealand.
B M
BM
Buddle
F E
FE
Aldwell
A
A
Pfeffer
G W
GW
de Lisle
D000818:Animals; D002478:Cells, Cultured; D005340:Fibrinogen / Q000032:analysis; D008168:Lung / Q000382:microbiology / Q000473:pathology*; D008213:Lymphocyte Activation; D008214:Lymphocytes / Q000276:immunology*; D008297:Male; D009163:Mycobacterium bovis / Q000302:isolation & purification; D009893:Opossums; D014376:Tuberculosis / Q000097:blood / Q000276:immunology / Q000473:pathology / Q000662:veterinary*; D014397:Tuberculosis, Pulmonary / Q000097:blood / Q000276:immunology / Q000662:veterinary*
D005340:Fibrinogen