FATAL SUPPURATIVE INFLAMMATION in DAURIAN PIKAS (OCHOTONA DAUURICA) NATURALLY INFECTED with CASTELLANIELLA GINSENGISOLI-LIKE BACTERIA

Fifteen Daurian pika (Ochotona dauurica) were introduced to a zoological collection in December 2011 as founders for a planned breeding colony. Despite breeding success, the colony shrunk over 37 mo to 11 animals. Mortality in 11 of 46 deceased animals, including wild-caught "founders" and captive-born offspring, was associated with a suppurative inflammation and abscess formation of the spleen, skin, peripheral and internal lymph nodes, liver, lungs, kidney, or a combination of organs. Gram-negative, non-fermenting, rod-shaped bacteria were isolated from the abscesses in all cases. Steiner Chapman silver stain identified rod-shaped bacteria in the abscesses of seven animals. The bacteria were not detected with Gram stain, acid-fast stain, or Grocott silver methenamine stain and was not detectable by periodic acid-Schiff reaction. In two cases, including the index case, the bacteria were presumptively identified as Ralstonia pickettii on the basis of conventional biochemical characterization. The bacteria in the other cases were not further classifiable with conventional methods. Matrix-assisted laser desorption/ionization time of flight mass spectrometry and 16s rDNA gene sequencing resulted in identification to the genus level as Castellaniella in 10 of 12 cases. Comparative 16S rDNA gene sequence analysis showed that these isolates and Castellaniella ginsengisoli Strain DCY36^T were 99% similar. Castellaniella ginsengisoli, a gram-negative bacterium isolated from soil of a ginseng field in South Korea, has not previously been associated with disease in animals or humans. It is uncertain how the bacterium was introduced to the Daurian pika colony or how it spread.