How to Take Samples from Animals
When an animal is suspected og being ill; samples need to be taken and examined in a laboratory to determine any problems; and if a problem exists, identify what it is. This may be carried out by a veterinary professional; or in some cases, someone else who works in the care of the animals.
Samples that may be taken from the live animal include: blood, faeces, skin, genital tract and semen, eye swab, nasal discharge, saliva, tears, milk.
Blood Samples
- Blood samples may be taken for haematology, culture, or examination for bacteria, viruses or protozoa. In this case it is usual to use anticoagulants (i.e. heparin). Thorough mixing (using gentle agitation only) is necessary as soon as the sample is taken.
- Blood taken for serology requires a clotted sample, so don’t use anticoagulants. The blood should be left to sit at room temperature (but protect it from excessive hot or cold) for one to two hours so that the clot can form. In some cases it may be necessary to take two samples from an animal 7-14 days apart, in order to determine if there are changes in antibody levels (titres).
- Another method used for collecting and transporting blood for serology, is to place a drop of blood on filter paper. The blood is dried at room temperature and the sample can be transported to the laboratory without refrigeration, the examiner would need to check with the laboratory first to make sure they can handle this method of collection.
- Blood plasma is also used for some tests.
- It may also be necessary to take a fresh blood smear on a microscope slide. Prepare both thick and thin smears.
- Blood samples are taken by venipuncture. In large animals blood is usually collected from the jugular vein or a caudal vein (tail). The mammary and brachial veins are sometimes used. See table below for collection sites for some species:
Procedure for making a blood smear
1. Thoroughly clean 2 or 3 microscope slides. Use Methylated Spirits if necessary and be sure no dust or greasy marks remain on the glass.
2. Clean the ear of the animal with a damp cloth then nick the edge with scissors or a sharp blade. The nick must be deep enough for blood to flow; not just to drip and quickly clot. It is impossible to make smears with half clotted blood.
3. Pick up a drop of blood about the size if a millet seed (no larger), near one end of the slide. Hold a second slide at an angle (30-50 degrees) to the first and push it lightly along its length to draw the blood behind it in a smooth film.
Don't allow the smear to dry in the sun. Keep it in the shade. When it is thoroughly dry (but not before), wrap it in clean paper upon which the following particulars should be written:
- Owners name
- Address
- Date of sample taken
- By whom forwarded
- Nature of preparation
- Symptoms
- Breed, age and sex of animal
- Disease suspected
Avoid the following Mistakes:
- Do not use a dirty or greasy slide
- Don't allow dirt or dust to settle on the slide
- Don't use too big a drop of blood
- Don't wrap a wet smear
- Don't wrap a smear in dirty paper
- Don't press two wet slides together
- Don't forget to send particulars with the slide.
Taking Smears of Pus and Discharges
The procedure is very similar to collecting a blood smear. A tiny amount of the required material is gathered onto the end of one slide, and spread thinly over it by pulling another slide, and spread thinly over it by pulling another slide along the first slide. Like blood smears, pus and discharge can be taken when the animal is alive or dead.
Faecal Samples
- A freshly voided sample is preferred
- Use screw top jars or sterile plastic bags
- For parasitology, fill the sample jar and ensure that it arrives at the laboratory within 24 hours. If the examiner thinks it will take longer than this, he or she should refrigerate the sample to prevent eggs from hatching or send packed on ice.
Skin Samples
- Hair or wool samples are useful for detecting surface feeding mites, lice and fungal infections
- Deep skin scrapings are helpful for detecting burrowing mites. For these use the edge of a scalpel blade to collect the sample.
- Where vesicular lesions are evident, you may collect vesicular fluid by aspirating it with a syringe. Put the fluid into a separate sterile tube or container.
- Take a sample of the affected epithelial tissue if possible. Ideally, this should be placed in a suitable medium for transport.
Eye Discharges
- Gently swab the conjunctiva and place the swab in a suitable medium for transport
- Scrapings can be taken and placed on a microscope slide
Semen and Genital Tract
- Samples can be taken by vaginal or preputial washing (e.g. washing the preputial cavity with sterile peptone water), using plastic pipettes to aspirate material, scraping the preputial and penile mucosa, or by swabbing.
- The cervix or urethra may be swabbed.
- Semen samples can be collected using an artificial vagina or by extrusion of the penis and artificial stimulation.
- Special transport media and conditions are usually required.
Milk
- Clean the teat area but avoid using antiseptic solutions
- Strip the teat once (i.e. discard the first stream of milk). Take your sample from the second stream.
- Some tests require samples from the bulk milk vat.
- Do not freeze heat or agitate milk that is taken for serological testing.
- Milk for bacterial testing can be frozen if the examiner anticipates a delay in sending the sample.
Saliva, tears, nasal discharge
- Use cotton or gauze swabs.
- Keep the swab in contact with the secretions for about one minute to ensure an adequate sample s taken.
- Use a suitable transport medium and submit to the laboratory without delay. Keep at 4oC
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