Abstract

Over the course of 7 mo (August 1997 to February 1998), 10 of 26 silvery marmosets (Callithrix argentata) in the WCS collection died. Of these, 7/10 died peracutely with severe typhlitis or typhlocolitis with ulceration and transmural abscess with variable involvement of the cecal lymph nodes, serosal cavities, and other organs. Both males and females were affected. The ages ranged from 3 mo to 9 yr. Klebsiella pneumoniae was the predominant isolate from a variety of sites (Table 1). Cultures were negative for bacteria commonly associated with intestinal disease in primates (Campylobacter sp., Salmonella sp., Yersinia sp., and Shigella sp.). In most cases, the marmosets died with no antemortem clinical signs. Two cases presented semi-comatose and subsequently died. One animal had a palpable mass in the caudal abdominal cavity, which corresponded to an abscessed cecal lymph node. Blood work was available on two animals. One animal had a regenerative leukocytosis with 29% band cells and both animals had pre-renal azotemia, hypergammaglobulinemia and anemia. Group treatments of surviving animals were attempted based on sensitivities from cultures taken at necropsy, however sporadic deaths continued during the 7-mo period.

This presentation was unusual in that the most common manifestation of Klebsiella pneumoniae in humans and other primates is pneumonia with subsequent bacteremia and localization in distant sites. There is only one similar report of Klebsiella pneumoniae related enteric disease in a group of primates at a research facility in Iquitos, Peru. In the Peruvian outbreak, Saguinus, Aotus, and one Saimiri were affected. In the Saguinus, the primary lesion was purulent peritonitis with no intestinal involvement. In the Aotus, the most common lesion was typhlitis with lymph node abscess and peritonitis.¹ During the outbreak at WCS, the infection started in the cecum with local spread (colon, cecal lymph node and peritoneum) and subsequent bacteremia (intravascular bacteria) with spread to distant sites (pleural cavity, pericardium, and meninges). Bacteria were readily identified in smears and histopathology sections. In those cases where Klebsiella pneumoniae was isolated, bacteria identified in the lesions were gram-negative rods surrounded by a thick clear capsule, which supports the belief that Klebsiella pneumoniae was the cause of the disease. In all cases, even in cases with multiple aerobic and anaerobic bacterial isolates from the abdominal cavity, Klebsiella pneumoniae was isolated in pure culture from at least one site.

After the first few deaths, an intensive survey of the building and historic necropsy records was undertaken in an effort to determine the prevalence, extent, and source of the Klebsiella pneumoniae outbreak. Klebsiella pneumoniae was isolated from some of the cultures done of group feces, exhibit substrates, food, insects, and food-handling areas. Evaluation of the fatty acid composition of the bacterial capsule was done to try to determine the relationship between the different isolates of Klebsiella pneumoniae. The fatty acid composition of the majority of the isolates from the monkeys was the same as that of the isolates from primate feces and the cockroaches but differed from the isolates of the cage branches and bark substrate.

Klebsiella pneumoniae occurs in the environment and as an intestinal commensal. Klebsiella pneumoniae is associated with timber products and wood shavings have been associated with outbreaks of mastitis in cattle. It is also a significant cause of nosocomial infections in hospitals.² The unusual disease presentation in this outbreak, may be due to a highly pathogenic strain of Klebsiella pneumoniae that spontaneously arose in the silvery marmosets or may be due to an undetermined stressor allowing a commensal strain to cause pathology.

Literature Cited

1.  Gozalo, A., and E. Montoya. 1991. Klebsiella pneumoniae infection in a New World nonhuman primate center. Lab. Primate Newsl. 30(2), 13–15.

2.  Timoney, J., J. Gillespie, F. Scott, and J. Barlough. 1988. The Enterobacteriaceae-The Lactose Fermenters In: Hagen and Brunner’s Microbiology and Infectious Disease of Domestic Animals. Comstock Publishing Associates, a division of Cornell University Press, Ithaca, New York, 71–73.