Division I.2.2 Histology

Sections of tissue that include gills, digestive gland, mantle, and gonad shall be fixed for at least 24 hours in Davidson's fixative followed by normal processing for paraffin histology and staining, for example with haematoxylin and eosin. Observations shall be made at increasing magnifications up to × 1 000.

A positive result shall be the observation of cells ranging in size from 4 up to 40 μm. Early stages consist of multinucleate, spheric to elongated cells. These are mainly found in the epithelium of oesophagus and stomach and sometimes of labial palps. Sporulation involves divisions of cells within cells and takes place in the digestive gland tubules and ducts. Refringent granules appear in the course of sporulation, but are not observed in early stages. In late phases of infection, sporangia are observed free in the lumen of the digestive tract. The cytoplasm stains basophilic, whereas the nucleus stains eosinophilic. The granules can range from deep orange to deep red.

The technique is not parasite species specific.