Passive immunity

You may recall that last week we spoke of active immunity which was produced by inoculating an animal with dead or weakened germs.
The animal then produces antibodies to those specific bacteria or viruses. These antibodies are to be found in the serum component of the blood (blood is made up of cells and serum). Well, if we take the antibodies (special proteins produced as a reaction of an animal’s body to the exposure to the germs = active immunity) from the exposed animal and inject them to another animal, then the latter can obtain quickly and directly (passively) protection. In other words, passive immunity is obtained by transferring pre-formed antibodies from a resistant animal to a susceptible animal, usually, but not necessarily, from the same species.

The blood-serum with those pre-formed antibodies gives the defence mechanisms of the threatened animal time to consolidate its forces and thus makes the animal less liable to be affected or to succumb to the disease.

There are several examples which we can mention, where passive immunity is conferred on an animal. ‘Lock jaw’ in horses, distemper in dogs, panleukopenia in cats, spring to mind. Once a satisfactory serum antibody level is reached, the blood is taken and the special proteins (globulins = antibodies) are precipitated and purified. The end product can then be introduced to the threatened animal. So, now you have, I hope, got a grasp of this whole, very complex and complicated issue of immunity. But there still are a few general considerations of which you must be aware.

Firstly, we had said that antibodies are extremely specific, ie they only destroy/neutralise those germs that stimulated their production in the first place. However, there are certain drugs that suppress/prohibit antibody production. Cortisones (used often as anti-inflammatory agents) create such situations. One should only use cortisones as a weapon against infection in animals, under veterinary prescription and supervision. Too often, we use these cortisones willy-nilly and without enough knowledge, and with incorrect dosages and dosage rates.

Secondly, any animal that is emaciated/malnourished or in any way debilitated, as well as very young animals, may not be in a position to efficiently produce antibodies. So, even if we vaccinate these animals (active immunisation) they may not be able to create a good enough, reliably protective immunity. Try to improve the condition of the animal, then vaccinate again.

Finally, if a young animal has received an immunity (passive antibodies) via its mother’s milk (colostrum – see Pet Corner July 27, 2008), then this immunity can render inactive (‘tie up’) any vaccine administered to stimulate active immunity. Consequently, it is usually recommended that puppies and kittens be at least six weeks of age before we begin the vaccination schedule.
Enough of this ‘immunity’ stuff. But now that you have grasped the ‘basics’ of this important biological defence mechanism, we can, with more confidence, turn our attention to the specific diseases – starting next week.

Please implement disease preventative measures (vaccinations, routine dewormings, monthly anti-heartworm medication, etc) and adopt-a-pet from the GSPCA’s Animal Clinic and Shelter at Robb Street and Orange Walk, if you have the wherewithal to care well for the animals. Do not stray your unwanted pets, take them to the GSPCA’s Clinic and Shelter instead. If you see anyone being cruel to an animal, or if you need any technical information, please get in touch with the Clinic and Shelter by calling 226-4237.

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