Skin scrapes, biopsies and cultures ( PCR ) involve a vet, usually in the field but sometimes in a clinic, taking samples to be analysed in a laboratory for diagnosis of diseases. These include skin diseases: skin scrapes look for skin parasites and sometimes fungi, skin biopsies for skin disease such as lumps, bumps and rashes. Biopsies can also be taken from deeper tissues, e.g. endometrial biopsy from he lining of the womb in breeding, or liver biopsy through a keyhole in the standing horse’s flank under ultrasound guidance. Cultures are samples taken from lesions or discharge which are sent to a lab to grow bacteria, viruses or fungi and to identify them. Sensitivity tests, to check for antibiotic suitability and resistance, can be applied to bacterial cultures. Polmerase Chain Reaction tests have been developed to look for specific pathogen DNA sequences (e.g. Strangles bacteria Streptococcus equi equi and some viruses) detection and are much quicker than cultures.
Biopsies are small pieces of tissue that are taken by a vet for analysis under a microscope. This is called histopathology (Histo – tissue, Pathology – disease). The tissue is preserved in a medium (e.g. formaldehyde solution), sent to a lab, stained and examined by an expert pathologist under a microscope. Skin biopsies are commonly taken by a vet to identify a skin disease that may be quite severe or may not b responding to treatment.
Cultures (and PCR ) are when samples are taken on suspicion of infection by bacteria, viruses or fungi. These samples are commonly taken by rubbing a “cotton bud” swab stick into a lesion or discharge which is then put in a preserving transport medium (e.g. charcoal) and sent to a laboratory (lab) where the sample is transferred to a growth medium, such as a broth or a horse blood agar plate. After incubating (usually 37 degrees Celcius) for 24 and/or 48 hours, the medium is checked for growth, e.g. for colonies of bacteria, and these are identified by colony shape and by looking at the bacteria, using stains, under a high-powered microscope. Viruses