Granuloma development in cattle after intratonsilar inoculation with Mycobacterium bovis

Mitchell V. Palmer From the Zoonotic Disease Research Unit, National Animal Disease Center, Agricultural Research Service (Palmer, Whipple, Bolin), and the Pathobiology Laboratory, National Veterinary Services Laboratories, Animal and Plant Health Inspection Service, Veterinary Services (Saari), USDA, Ames, IA 50010; and the National Wildlife Research Center, Animal and Plant Health Inspection Service, Veterinary Services, USDA, Fort Collins, CO 80524 (Rhyan).

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Diana L. Whipple From the Zoonotic Disease Research Unit, National Animal Disease Center, Agricultural Research Service (Palmer, Whipple, Bolin), and the Pathobiology Laboratory, National Veterinary Services Laboratories, Animal and Plant Health Inspection Service, Veterinary Services (Saari), USDA, Ames, IA 50010; and the National Wildlife Research Center, Animal and Plant Health Inspection Service, Veterinary Services, USDA, Fort Collins, CO 80524 (Rhyan).

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Jack C. Rhyan From the Zoonotic Disease Research Unit, National Animal Disease Center, Agricultural Research Service (Palmer, Whipple, Bolin), and the Pathobiology Laboratory, National Veterinary Services Laboratories, Animal and Plant Health Inspection Service, Veterinary Services (Saari), USDA, Ames, IA 50010; and the National Wildlife Research Center, Animal and Plant Health Inspection Service, Veterinary Services, USDA, Fort Collins, CO 80524 (Rhyan).

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Carole A. Bolin From the Zoonotic Disease Research Unit, National Animal Disease Center, Agricultural Research Service (Palmer, Whipple, Bolin), and the Pathobiology Laboratory, National Veterinary Services Laboratories, Animal and Plant Health Inspection Service, Veterinary Services (Saari), USDA, Ames, IA 50010; and the National Wildlife Research Center, Animal and Plant Health Inspection Service, Veterinary Services, USDA, Fort Collins, CO 80524 (Rhyan).

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Dennis A. Saari From the Zoonotic Disease Research Unit, National Animal Disease Center, Agricultural Research Service (Palmer, Whipple, Bolin), and the Pathobiology Laboratory, National Veterinary Services Laboratories, Animal and Plant Health Inspection Service, Veterinary Services (Saari), USDA, Ames, IA 50010; and the National Wildlife Research Center, Animal and Plant Health Inspection Service, Veterinary Services, USDA, Fort Collins, CO 80524 (Rhyan).

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Abstract

Objective

To examine the temporal development of tuberculous lesions in cattle inoculated with Mycobacterium bovis.

Animals

15 mature crossbred cows obtained from a herd with no history of M bovis infection.

Procedure

Inoculation of cattle was done by intratonsilar instillation of 1.48 × 105 to 5.4 × 107 colony-forming units of M bovis strain 2045T. At 3 to 4 hours, 4 weeks, 6 weeks, and 8 weeks after inoculation, tissues were examined for gross and microscopic lesions and processed for isolation of M bovis.

Results

Retropharyngeal lymph nodes from cattle examined 4 weeks after inoculation contained microgranulomas consisting of aggregates of macrophages with few neutrophils. Retropharyngeal lymph nodes from all cattle examined 6 and 8 weeks after inoculation contained multiple, large, coalescing granulomas consisting of central areas of necrosis with mild fibrosis, numerous macrophages, lymphocytes, plasma cells, multinucleated giant cells, and neutrophils. Three of 8 cattle examined 6 or 8 weeks after inoculation had lesions in nonretropharyngeal sites with morphologic characteristics similar to that seen in retropharyngeal lymph node granulomas from cattle examined 4 weeks after inoculation.

Conclusion

Granulomas can develop in draining lymph nodes of cattle in as little as 4 weeks after inoculation via intratonsilar instillation of M bovis. Intralesional morphologic changes between 4 and 6 weeks after inoculation indicate an increase in cellular chemotaxis and differentiation. Dissemination of bacteria to distant sites most likely was by lymphatic and hematogenous routes after establishment of the primary infection in retropharyngeal lymph nodes. (Am J Vet Res 1999;60:310–315)

Abstract

Objective

To examine the temporal development of tuberculous lesions in cattle inoculated with Mycobacterium bovis.

Animals

15 mature crossbred cows obtained from a herd with no history of M bovis infection.

Procedure

Inoculation of cattle was done by intratonsilar instillation of 1.48 × 105 to 5.4 × 107 colony-forming units of M bovis strain 2045T. At 3 to 4 hours, 4 weeks, 6 weeks, and 8 weeks after inoculation, tissues were examined for gross and microscopic lesions and processed for isolation of M bovis.

Results

Retropharyngeal lymph nodes from cattle examined 4 weeks after inoculation contained microgranulomas consisting of aggregates of macrophages with few neutrophils. Retropharyngeal lymph nodes from all cattle examined 6 and 8 weeks after inoculation contained multiple, large, coalescing granulomas consisting of central areas of necrosis with mild fibrosis, numerous macrophages, lymphocytes, plasma cells, multinucleated giant cells, and neutrophils. Three of 8 cattle examined 6 or 8 weeks after inoculation had lesions in nonretropharyngeal sites with morphologic characteristics similar to that seen in retropharyngeal lymph node granulomas from cattle examined 4 weeks after inoculation.

Conclusion

Granulomas can develop in draining lymph nodes of cattle in as little as 4 weeks after inoculation via intratonsilar instillation of M bovis. Intralesional morphologic changes between 4 and 6 weeks after inoculation indicate an increase in cellular chemotaxis and differentiation. Dissemination of bacteria to distant sites most likely was by lymphatic and hematogenous routes after establishment of the primary infection in retropharyngeal lymph nodes. (Am J Vet Res 1999;60:310–315)

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