Cryptosporidiosis in Animals and Man: 2. Diagnosis

Abstract

Different diagnostic methods including clinical examination, detection of endogenous developmental stages by histopathology and electron microscopy, detection of oocysts by concentration and purification of Cryptosporidium oocysts and staining techniques, immunological assays and molecular identification techniques are described. Clinical examination revealed that diarrhoea begins in infected neonates at 3-5 days post-infection and last for 4-17 days. High mortality due to cryptosporidiosis has been reported, even in the absence of other enteropathogens. Cryptosporidium infections can be diagnosed by histological examination of autopsy or biopsy material from the intestinal mucosa. Endogenous developmental stages can be recognized associated with villous atrophy, villous fusion and changes in the surface epithelium. Scanning and transmission electron microscopy have confirmed the intracellular but extra cytoplasmic location within parasitophorus vacuoles formed by a continuous covering of microvillous membranes. Many specialized staining procedures have been described to stain the wall and/or contents of mature oocysts. The stain of choice for many diagnostic laboratories has been acid-fast staining and safranine-methylene blue. Oocysts stained bright red whereas yeast, bacteria and other fecal debris only take up the counter stain (green or blue). More recently, several immunolabelling techniques using polyclonal or monoclonal antibodies have been developed to detect oocysts.