here - Australian College of Veterinary Scientists

twitch and sedation previously. Caution should be given that not all horses tolerate a
nose twitch well and common sense should prevail!
2. Site Preparation
The preferred site for skin testing is the lateral cervical neck above the jugular furrow,
between the jaw and the shoulder. For a standard 80-injection skin test kit, an area
around the size of an A4 sheet of paper is clipped with number 40 blades against the
direction of hair growth.
Where the skin is excessively dirty, gently cleaning with swabs moistened in plain
water should provide a clean working surface.
The author uses a template made of stiff plastic to ensure even spacing of the
injection site ‘dots’. For 80 injections: 4 rows of 10 holes (about 2cm apart) were
created in the template, and a waterproof white ‘paint-pen’ is used to mark the
injection sites. Given that almost all horses have dark skin (even with a pale coat
colour), a dark felt-tipped pen can be completely invisible, particularly when the skin
test site is examined 24 hours after injection.
3. Injection process
Injections are administered intradermally above and below the injection markers. Using
a 30-gauge needle and a 1ml syringe, approximately 0.05 to 0.1ml of solution is
injected. The quantity injected appears to be based on personal preference of the
clinician; provided the quantity is consistent for every injection in the test, there will
be a relative correlation in the size of positive reactions.
The first two and last two injections of every test should be the negative and positive
controls of saline (or preferably allergen diluent) and histamine (1:100 000)
respectively. The allergens are numbered at the base of the syringe plunger and
injected in sequential numerical order.
Some question remains as to whether needles need to be changed if the kit is to be
used again for a different animal. This was discussed with equine veterinarians in
Sydney who concluded it would be prudent to change needles between horses (and
certainly between species of animals). Blood borne diseases that may be relevant in
horses include: Equine morbillivirus (the zoonotic potential of this disease should
also be observed), Equine infectious anaemia and viral arteritis. Even if the risk of
these diseases is relatively low, the practitioners were keenly aware that veterinarians
must be seen to be doing the ‘right thing’ in the eyes of their clients.
4. Reading the injection sites
It has been recommended that reactions be evaluated at 15 to 30 minutes after
injection, and if possible at 45mins, 4 to 6 hours and at 24 to 48 hours (16). This may
or may not be practical or relevant.
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ACVSC Proceedings Dermatology Chapter Science Week 2005