Infection with Burkholderia pseudomallei causes the disease
melioidosis, which often presents as a serious suppurative
infection that is typically fatal without intensive treatment and is a significant
emerging infectious disease in Southeast Asia. Despite intensive research there is still much that remains unknown about
melioidosis pathogenesis. New animal models of
melioidosis are needed to examine novel aspects of pathogenesis as well as for the evaluation of novel
therapeutics. The objective of the work presented here was to develop a subacute to chronic caprine model of
melioidosis and to characterize the progression of disease with respect to clinical presentation, hematology, clinical microbiology, thoracic radiography, and gross and microscopic pathology. Disease was produced in all animals following an intratracheal
aerosol of 10(4) CFU delivered, with variable clinical manifestations indicative of subacute and
chronic disease. Bronchointerstitial
pneumonia was apparent microscopically by day 2 and radiographically and grossly apparent by day 7 post
infection (PI). Early lesions of
bronchopneumonia soon progressed to more severe bronchointerstitial
pneumonia with pyogranuloma formation. Extrapulmonary dissemination appeared to be a function of pyogranuloma invasion of pulmonary vasculature, which peaked around day 7 PI. Histopathology indicated that
leukocytoclastic vasculitis was the central step in dissemination of B. pseudomallei from the lungs as well as in the establishment of new lesions. While higher doses of organism in goats can produce acute fatal disease, the dose investigated and resulting disease had many similarities to human
melioidosis and may warrant further development to provide a model for the study of both natural and bioterrorism associated disease.