Vet Lab Manual

Parasitology

Faecal egg counts and egg type (by larval differentiation) are a guide to the size and type of worm burden. Faecal egg counts are influenced by faecal consistency and bulk, host resistance, stage of pregnancy and effects of lactation.

Starvation will increase egg counts and inappetence may cause the count to increase by up to 30 to 40 times. Diarrhoea will reduce egg counts.

Faecal egg counts will vary according to the parasite species involved and whether the worm burden consists of sexually mature parasites.

The history should provide details of recent anthelmintic treatments including drench resistance status, stocking rate, pasture availability, swampy areas, grazing rotation.

Standard Containers and Equipment

Jars

Plastic (5 ml, 20 ml, 70 ml) screw top containers for insects, parasites, aliquots of gut washings, skin scrapings.

Parasite faecal collection kits

Collection kits are available from your Regional Veterinary Laboratory.

WormTest kits contain 10 containers for monitoring a single mob or grazing group in a herd.
DrenchTest kits include 50 containers for one control and four test drench groups. Use additional WormTest kits for extra drench groups.
Horse WormTest kits are suitable for 5 horses.
DrenchRite® kits for bulk faecal collection allow farmers to test for resistance with a single muster.

Vacuum blood tubes (with anticoagulant)

For heartworm antigen and microfilaria tests in dogs (generally for export purposes).

Vacuum blood tubes (plain)

For serology of liver fluke infection in cattle.

Collection of Specimens for Parasitology

Faecal samples

For individual animals at least 30 g of fresh faeces should be collected (preferably from the rectum) and placed directly into a jar. The jar should be filled and the lid closed tightly in order to minimise exposure of worm eggs to air which would allow egg development.

Wormtest Kit samples should be collected from 10 animals, including apparently healthy and affected animals in each mob. Complete instructions for collection of samples are provided with each WormTest kit.

Gastrointestinal tract

The total gastrointestinal tract should be submitted direct to the laboratory when it can be delivered by the submitter, double bagged in strong clear plastic bags. Only submit unpreserved chilled guts if delivery to the laboratory is assured within 36- 48 hours. The tract should not be opened and each part should be tied off at the appropriate junction, i.e. between the stomach (abomasum) and small intestines and between the small and large intestines.

Alternatively the organs can be washed by the field veterinarian and aliquots (from washings of known volume) submitted to the laboratory. Contact the laboratory for instructions on the procedure.

Insects and snails for identification

These should be submitted in 70% alcohol in a small leak proof container.

Mites

Acute skin lesions should be scraped with a scalpel until blood is produced. Moisten the scalpel with liquid paraffin. Scrape particularly at the edge of any visible lesion. Before scraping, hair or wool must be clipped as close to the skin as possible. Scrapings should be sealed in a small, wide mouthed bottle and submitted unpreserved.

Parasites for identification

Flukes, tapeworms and roundworms should be washed in water and preserved in 5 per cent formalin. Always include the head of the tapeworm.

When identification of parasitic cysts is required, tissues should be submitted chilled in a jar.

Blood

Collect a full tube of blood. For tubes with anticoagulant ensure blood is gently mixed with anticoagulant. Plain blood tubes should be allowed to clot at room temperature.

Storage and Despatch of Specimens

Faecal samples should be kept cool, but not frozen. Even prolonged chilling at 5&degC kills the eggs of most species and makes samples unsuitable for larval culture for strongyle egg identification.

Faecal samples should be submitted as soon after collection as possible, chilled in an insulated container, with icebricks wrapped in newspaper to prevent freezing. Gastrointestinal tract washings should be preserved in 5% formalin.

Related Sections

Also see specific parasitic diseases