Chapter 29 - RITARD Rabbit Model for Studying Vibrio cholerae and Other Enteric Infections

Abstract

The removable intestinal tie adult rabbit diarrhea (RITARD) model was first proposed by Spira et al. in an attempt to create a simple animal model for studying the toxin-mediated diarrheal disease caused by Vibrio cholerae and enterotoxigenic Escherichia coli (ETEC). This model is now widely used for studying the pathogenesis of enteric pathogens. Key factors in its wide acceptance include the ease of the procedure, the availability of the animal species, and its "whole animal" characteristics. Outbred New Zealand White adult rabbits are used in this model. The rabbits should be allowed at least 24 hours to acclimatize in the animal facility after shipment. Rabbits are fasted overnight and prepared for surgery by shaving the ventral part of the abdomen with an electric clipper after the animals are anesthetized. A cocktail of ketamine, acepromazine, and xylazine is injected subcutaneously as anesthesia. After induction of appropriate anesthesia, the animal is covered with a sterile surgical drape, with a small opening for conducting the surgery. A 4–5 cm midline incision is made by using a scalpel through the skin and linea alba. Two hours after the inoculation of bacteria, the ileal tie is released by gentle tugs on the free end. Animals are then returned to the cage and allowed food and water ad libitum and observed for 1–7 days in a biohazard facility. Animals should be monitored closely for signs of clinical disease. This could range from loose stool to signs of sepsis and intestinal necrosis, depending on the infectious agent and the dose used. Stool samples should be collected from ileum and colon, weighed, and plated for bacterial count. This provides a measure of total bacterial colonization in the intestine at the time of necropsy.