The objective of this study was to determine the prevalence, serotypes, antimicrobial resistance phenotypes, and pulsed-field gel electrophoresis (PFGE) patterns of Salmonella recovered in feces and mesenteric and prefemoral lymph nodes (LNs) from cohorts of calves with and without a confirmed outbreak of salmonellosis. In a prospective cohort study, 160 calves from four farms without a reported outbreak (nonoutbreak farms) were sampled at farm and harvest. In addition, harvest samples from 80 calves of two farms with a confirmed outbreak (outbreak farms) were collected. A culture protocol for Salmonella isolation was applied for all samples and recovered isolates were further characterized by serotyping, antimicrobial susceptibility testing, and PFGE. Among nonoutbreak farms, Salmonella was recovered from 0% (0/160) farm fecal samples, 3.7% (6/160) harvest fecal swabs, 21.9% (35/160) mesenteric LNs, and 0.6% (1/160) prefemoral LNs. Serotypes identified in nonoutbreak herds included Salmonella Typhimurium, Cerro, Hartford, and Newport. Most isolates (64.3%, 27/42) exhibited a unique multidrug-resistant (MDR) phenotype, including resistance to extended-spectrum cephalosporins. Salmonella prevalence in harvest fecal samples and prefemoral LNs among calves from outbreak farms was numerically higher, but not significantly different than those without an outbreak. Serotypes recovered from outbreak farms included Salmonella Heidelberg and Typhimurium, and the monophasic Salmonella Typhimurium strains 4,5,12:i:- and 4,12:i:-, which have been also reported as highly pathogenic in humans. All isolates (33/33) exhibited an MDR phenotype. Salmonella strains recovered from ill calves in two outbreaks had indistinguishable PFGE patterns, suggesting between-farm transmission. In addition, the genotype of Salmonella Heidelberg causing an outbreak among calves was recovered from three prefemoral LNs of surviving members of the cohort at harvest. Implementation of preharvest biosecurity measures (limited personnel and visitor traffic, vehicle, footwear, and utensils disinfection) should be highly recommended to decrease the prevalence of Salmonella on farms and safeguard the food safety.

Although Salmonella spp. infection has been identified in captive and free-ranging rhinoceros, clinical cases in black rhinoceros ( Diceros bicornis ) calves have not been described. This case series describes clinical salmonellosis in four black rhinoceros calves. Two calves developed self-limiting diarrhea, recovering after treatment. The other two cases were fatal. One of the fatal cases had a short clinical course, whereas the other case was protracted, with signs reflecting multiple organ system involvement. In all cases, diagnosis was by fecal culture and/or quantitative polymerase chain reaction. A variable clinical presentation, which is typical for salmonellosis in domestic hoofstock, was a feature of these rhinoceros cases. Similarly, postmortem pathology in black rhinoceros calves was consistent with domestic neonatal ungulates with salmonellosis. Potential predisposing factors for infection were considered to be primiparity of the dam and failure of passive transfer in the calf. The case investigation included attempts to identify the source of infection, which was aided by organism serotyping. In one case, the patient\'s dam and another conspecific in the facility were shown to be asymptomatic shedders of the organism strain responsible for disease in the calf. Further surveillance of captive rhinoceros Salmonella spp. carrier status is needed to inform screening recommendations for this taxa.