By Jean Pattison
This is probably one of the most misunderstood necessities of owning birds. When one is quarantining a bird or birds it is to protect the old flock as well as the new. Each group of birds live in their own unique environment, and have built up immunities to the germs (good and bad) that they are exposed to daily. Regardless of where a new bird is purchased from, or how impeccable the husbandry or the reputation of the seller, quarantine should be regarded as a very necessary practice.
The new bird is crated and taken from its eco-system and placed in a totally new environment with a multitude of germs (good and bad) that it has never been exposed to. During this move to the new location some stress will be experienced. This stress can be very minor or it can be a major upset, depending on the nature of the bird, the difference in environment and how the bird reacts to it. During this time of stress, the birds immune system may become suppressed, and the bird may not be in as good a physical shape as when it left it's home. If the bird is not quarantined, it will be bombarded by millions of new germs and the immune system will need to kick in and respond to all these new germs (good and bad). With a compromised immune system the bird will not be able to surmount a good response and may indeed fall victim to a germ that normally would not be pathogenic (disease causing) in this bird in a different situation.
The new bird now becomes ill and starts shedding vast amounts of this now (new to him) pathogenic germ, and also starts shedding germs in vast amounts that the bird brought with him from his old environment. We now have millions of pathogens in the environment that the resident birds are being exposed to. Some are new germs, and some are old that they had immunities to, but the shear volume is more than they can handle. Now we have old and new birds getting sick, and of course one believes this disease came with the newest arrival.
Obviously, if any of the birds involved had an existing pathogenic disease, the consequences would be much worse.
Had this arrival been quarantined properly, his stress level would not have been so great and his immune response would have been able to build up to the smaller amounts of germs it was exposed to. After a gradual time of small exposures, the immune system can build immunities at a much more normal pace, and not become compromised. This gradual transition into a new environment proves beneficial, and necessary to all the birds involved. Germs don't read one way signs.