Diagnostic Necropsy and Selected Tissue and Sample Collection in Rats and Mice

Abstract

There are multiple sample types that may be collected from a euthanized animal in order to help diagnose or discover infectious agents in an animal colony. Proper collection of tissues for further histological processing can impact the quality of testing results. This article describes the conduct of a basic gross examination including identification of heart, liver, lungs, kidneys, and spleen, as well as how to collect those organs. Additionally four of the more difficult tissue/sample collection techniques are demonstrated. Lung collection and perfusion can be particularly challenging as the tissue needs to be properly inflated with a fixative in order for inside of the tissue to fix properly and to enable thorough histologic evaluation. This article demonstrates the step by step technique to remove the lung and inflate it with fixative in order to achieve optimal fixation of the tissue within 24 hours. Brain collection can be similarly challenging as the tissue is soft and easily damaged. This article demonstrates the step by step technique to expose and remove the brain from the skull with minimal damage to the tissue. The mesenteric lymph node is a good sample type in which to detect many common infectious agents as enteric viruses persist longer in the lymph node than they are shed in feces. This article demonstrates the step by step procedure for locating and aseptically removing the mesenteric lymph node. Finally, identification of infectious agents of the respiratory tract may be performed by bacterial culture or PCR testing of nasal and/or bronchial fluid aspirates taken at necropsy. This procedure describes obtaining and preparing the respiratory aspirate sample for bacterial culture and PCR testing.

Three species ofAeromonas(A. dhakensis, A. hydrophila and A. jandaei) isolated from freshwater crocodiles (Crocodylus siamensis) with pneumonia and septicemia

“…The splanchnocoele was dissected along the ventral midline using strict aseptic technique with protective apparel, according to standard procedures (Parkinson et al . ). Heart blood was collected by cardiac puncture.…”

Medical Management and Diagnostic Approaches

“…The suggested background reading and references by the following should aid those that have an interest in the conduct of the rat necropsy (Greene, 1963;Cook, 1965;Olds and Olds, 1979;Wingerd and Stein, 1988;Popesko et al, 1992;Bono, 1994;Feinstein, 1994;Sharp and LaRegina, 1998;Bono et al, 2000;Parkinson et al, 2011;Fiette and Slaoui, 2011). The suggested background reading and references by the following should aid those that have an interest in the conduct of the rat necropsy (Greene, 1963;Cook, 1965;Olds and Olds, 1979;Wingerd and Stein, 1988;Popesko et al, 1992;Bono, 1994;Feinstein, 1994;Sharp and LaRegina, 1998;Bono et al, 2000;Parkinson et al, 2011;Fiette and Slaoui, 2011).…”

The Vital Role of Pathology in Improving Reproducibility and Translational Relevance of Aging Studies in Rodents

“…Research staff should have basic training in performing a necropsy and have appropriate fixative available to store carcasses prior to histopathological assessment. 37,57,66,73 …”