The growth and sustainability of shrimp farming worldwide relies on the detection of infectious diseases. With continued growth of the industry, disease outbreaks become more common and new diseases continue to emerge. To fight the spread of disease, farmers rely on regular health assessments. Histopathology and PCR-based diagnostics are the main means of conducting these health assessments within a laboratory setting but rely on adequate fixation.
Davidson’s Alcohol Formalin Acetic acid fixative (DAFA) has been the gold standard for the preservation of shrimp tissues for histopathological analysis for half a century. However, in many regions around the world, chemical-grade glacial acetic acid (GAA) is very difficult to acquire, expensive, and is identified as a hazardous substance that also impacts sample shipping. In an effort to make shrimp sample preparation and shipping more accessible and environmentally friendly, we evaluated 30% industrial-strength vinegar (ISV) as an alternative to GAA in DAFA. While chemically similar to GAA, ISV is inexpensive, and is readily available worldwide due to its use as a household cleaner.
For initial testing, healthy Penaeus vannamei shrimp were fixed with either DAFA or a modified fixative with ISV in place of GAA. The shrimp were then processed according to conventional techniques for paraffin embedding and sectioning. Sections were stained with Mayer-Bennett’s hematoxylin/eosin- phloxine (H&E) and examined via light microscopy. Preliminary analysis revealed that the modified fixative provides the same quality of tissue preservation as traditional DAFA, indicating that it may be a viable replacement that would give greater accessibility to this crucial technique. Results indicate that fixative solution formulated with ISV in place of GAA yields equivalent ability to prevent autolysis, preserve tissue morphology, decalcify the cuticle of shrimp, and functionally identical staining properties as DAFA formulated with GAA.