Date of Award

2001

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biomedical and Veterinary Medical Sciences - Veterinary Clinical Sciences

First Advisor

Simon M. Shane

Abstract

The incidence of iguana-associated salmonellosis reported in humans during the 1990's is a public health concern. This research is the first attempt to describe the epidemiology of Salmonella in the green iguana. Seasonal prevalence of Salmonella in green iguanas and their environment were estimated at a commercial iguana farm in El Salvador. The prevalence of Salmonella was lower in adult iguanas (44%) than in yearlings (50%) (Odds ratio (OR): 0.77, 95% Confidence Intervals (CI): 0.6--0.96) and higher in male iguanas (50%) than females (41%) (OR: 1.5, 95% CI: 1.2--1.8). Salmonella recovery was lower in the fall (41%) sampling period than in the spring (49%) (OR: 0.7, 95% CI: 0.6--0.9). Recovery of Salmonella from the ovary of one (4%, n = 25) female iguana, 5 (14%, n = 35) hatchling yolk-sacs, 3 (5%, n = 66) embryonic yolk-sacs, and one (2%, n = 66) embryo suggests that this organism may be transmitted vertically. Salmonella was not isolated from feed samples, food preparers' hands, insects, or well water. Salmonella was isolated from the soil (44%, n = 340) and the water basins (37%, n = 116) within the pens housing iguanas. Bayesian estimates of the sensitivity and specificity of the polymerase chain reaction (PCR) assay, enzyme-linked immunosorbent assay (ELISA), and microbiological culture protocol used for Salmonella detection in the iguanas in this study were 0.93 and 0.95, 0.81 and 0.86, and 0.67 and 0.99 respectively. A series of intervention studies were performed to create a Salmonella clearance and infection model to evaluate a commercial Salmonella vaccine. Young iguanas treated with 10 mg/kg enrofloxacin suspension per os were less likely to be Salmonella positive than untreated iguanas ( 82 = 36.2, 1 df, p < 0.0001). Iguanas cleared with enrofloxacin and re-infected with Salmonella Typhimurium strain 524 were more likely to be Salmonella positive than uninfected iguanas ( 82 = 13.3, 1 df, p < 0.001). Latent infection was observed in six (32%) cleared, but uninfected, control iguanas. Vaccination with a commercially licensed avirulent attenuated Salmonella Typhimurium did not protect vaccinated iguanas against re-infection with Salmonella Typhimurium strain 524 ( 82 = 0.06, 1 df, p = 0.8).

ISBN

9780493272702

Pages

162

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