Enzootic enteropathogenic Escherichia coli infection in laboratory rabbits.

Enteropathogenic Escherichia coli (EPEC) is the most important cause of persistent diarrhea in children, particularly in developing countries. Animals serve as pathogenic E. coli reservoirs, and compelling evidence for cross-species EPEC transmission exists. In this report, enzootic EPEC infection associated with up to 10.5% diarrhea-associated morbidity in a large laboratory Dutch Belted rabbit colony was investigated. These rabbits were obtained from a commercial vendor and had acute diarrhea following shipment. Fecal culture of 20 rabbits yielded 48 E. coli isolates, 83% of which were eae positive. Repetitive sequence-based PCR (REP-PCR) and serologic analysis identified a single disease-associated EPEC O145:H2 strain. In sampled rabbits, EPEC-positive culture and the presence of diarrhea were significantly associated. This strain displayed a localized adherence-like HEp-2 cell adherence pattern, as seen in diarrheic human infant EPEC isolates. Treatment was instituted with the fluoroquinolone antibiotic enrofloxacin, to which all isolates were susceptible. Preshipment parenteral enrofloxacin administration reduced diarrhea-associated morbidity 22-fold and mortality 12-fold in subsequent deliveries. This report emphasizes the zoonotic potential of animal EPEC strains and the need for virulence determinant-based screening of E. coli isolates from diarrheic animals.

High mortality due to Tetrahymena sp. infection in laboratory-maintained zebrafish (Brachydanio rerio).

A large colony of laboratory zebrafish (Brachydanio rerio) used in the study of early vertebrate embryogenesis began experiencing acute, unexplained mortality that approached 100% among approximately 30-day-old resident fry. The initial differential diagnosis included ammonia, nitrite, or chlorine toxicosis, as well as iatrogenically induced toxicosis associated with improper sanitation procedures of laboratory equipment. Necropsy of dead and moribund fry prior to fixation revealed swarms of ovoid-shaped, motile, ciliated protozoa with a "spiraling football" motion. Wet mount preparations of various water samples also contained high numbers of similar protozoa. Histologic examination of affected fry revealed numerous, periodic acid-Schiff-positive forms within the body coelom, and epithelial and muscle tissues. The protozoa were consistent morphologically with members of the genus Tetrahymena, which is usually a free-living, nonpathogenic ciliated protozoa in fresh and saltwater environments. Relevant disease associated with Tetrahymena spp. in viviparous fish has been reported as a result of concurrent disease, immunosuppression, or poor water quality conditions. To the authors' knowledge, this is the first report of an epizootic involving laboratory maintained zebrafish, and the diagnostic course and therapeutic interventions undertaken to alleviate Tetrahymena species-associated clinical disease.

Diagnostic techniques for clinical investigation of laboratory zebrafish.

Unexpected morbidity and mortality of aquatic animal models represent a significant problem for researchers. The authors outline the basic procedures used to diagnose disease outbreaks in laboratory zebrafish colonies, and provide a basic framework for initiating clinical investigations.

Biomethod for Obtaining Gastric Juice and Serum From the Unanesthetized Guinea Pig (Cavia porcellus).

Blood sample collection and gastric intubation of guinea pigs have been considered difficult techniques that require anesthesia. We developed methods to sample blood and gastric juice from manually restrained, unanesthetized guinea pigs. To collect gastric juice, the guinea pig is restrained in vertical position by an assistant, who keeps the guinea pig's head in extreme dorsoflexion by use of a strip of gauze looped around the top incisors. The operator uses a second strip of gauze to control the lower jaw, and inserts a 5- or 6-F infant feeding tube down the throat, being careful not to deviate to either side of the buccal cavity. The tube slides directly down the esophagus of a correctly positioned guinea pig, and up to 5 ml of gastric juice can be withdrawn, using a syringe attached to the feeding tube. Blood sample collection was done by jugular venipuncture of manually restrained mesmerized guinea pigs; up to 2.5 ml of blood can be collected via this route. We have used these techniques on more than 50 guinea pigs ranging from 2 weeks to 18 months of age, and obtained weekly blood and gastric juice samples with no resultant morbidity or mortality and minimal distress. Repeated gastric juice and blood collections can be made safely from manually restrained, unanesthetized guinea pigs.