By Dr Steve Surujbally
I had said last week that one cannot really understand the prevention and treatment of infectious diseases if the concept of immunity is not grasped.
The word ‘immunity’ stems from the Latin word for ‘exempt.’ Loosely, it would mean the power to exempt the body from infection, ie to resist infection. This fight against infection is undertaken by special chemical substances called antibodies which attack and destroy germs as they enter the animal’s body and before they can cause illness. Let us look at the different forms of immunity that the body can exhibit.
Natural or inherited immunity
Some species of animals just cannot be infected by germs or poisons that would create an ailment or even cause death in other species. The mongoose in India seems to be immune from the venom of the King Cobra; pigeons can accommodate high doses of morphine without ill effect; poultry are resistant to tetanus (lockjaw) and anthrax; horses don’t succumb to foot-and-mouth disease; rats don’t get tuberculosis; humans don’t get canine distemper and parvovirus; and animals (except monkeys) don’t contract syphilis.
In other words, Mother Nature has ensured that many (not all) diseases are species specific, which means there can be no cross infection between species in most cases.
Nature also allows animals to acquire an immunity to a specific disease after birth. For example, if the mother had an encounter with a disease and survived, or if she had been vaccinated, she would have developed antibodies against that disease. These antibodies enter the milk of the mother and are then passed over to the offspring within the first few days of the newborn’s life.
The milk which is produced during the few days by a newly lactating mother is called colostrum.
These antibodies which are now in the puppies or kittens (having arrived via the colostrum) can protect them against the specific disease, but only for a relatively short while. That is why we still need to vaccinate the young animals later on (as early as six weeks of age).
Let me say something more about these antibodies, so important are they. They are produced by a special system which incorporates certain organs in the body. Lymph nodes, the spleen, the liver and the lungs are some of these organs. Also, white blood cells and special cells in the bone marrow are part of this total defence system. These antibodies are very specific.
They will only attack those germs that cause their formation in the first place. Antibodies formed to defend the animal against a tetanus germ invasion cannot protect the animal when the distemper virus, say, enters and attacks the young animal.
I’d better stop here. Too much heavy science is being shared (hopefully in an understandable way). And there is a bit more to come.
Next week we will deal with the issue of an artificially acquired immunity (active and passive immunity) as distinct from the natural immunity.
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.
