Salmonella surveillance in a herd of asymptomatic captive black rhinoceros (Diceros bicornis) using fecal culture and PCR.

Feces were collected from captive black rhinoceros (Diceros bicornis minor) housed at Disney's Animal Kingdom to examine the frequency of Salmonella spp. shedding in asymptomatic animals using enrichment culture and broth culture- polymerase-chain-reaction (PCR) for detection. Three samples per animal were collected during the first week of each month between February 2001 and December 2003. During the study period, six different individual animals from one herd participated in the study, including two growing calves. A total of 550 cultures, using duplicate samples at two different laboratories, and 464 PCR tests were performed. When culture and PCR results were compared by the same laboratory, similar herd prevalence was found (2.4% positive cultures compared with 2.6% positive PCR tests). However, even though tests were performed on replicate samples, not every sample that was positive by culture was positive by PCR and vice versa. These results suggest that using multiple diagnostic methods and increasing the number of samples submitted may increase the likelihood of finding an asymptomatic Salmonella shedder. Although all of the rhinos shared the same environment throughout the study period, only four out of the six animals tested shed Salmonella spp. even though a minimum of 37 fecal samples were taken from each of the negative animals. Although this study followed a small number of rhinoceros, it suggests that asymptomatic shedding probably occurs more frequently in captive black rhinoceros than was previously believed. The prevalence appears to be similar to that reported for domestic ungulates.