Biosecurity is the most practical way to keep your birds healthy. Biosecurity is the practice of keeping your birds isolated in their own safe, healthy environment that you have created for them.
It's sort of a "quarantine" but in an "open" environment.
What you want to do is protect your birds from other environments, or "biological" areas to avoid contamination of your birds' environment. It means protecting your flock from infectious agents, whether viral, bacterial, fungal, or parasitic.
It works like this...
Never bring in other birds from other environments. When adding birds to your flock, buy peeps from a reputable source, or hatch them yourself. Avoid bringing in that bird "my friend wants to give away" no matter how beautiful. Birds can carry all sorts of problems with them that can spread like wildfire through your flock. NEVER buy other birds and just throw them in with yours. It's a situation that welcomes disaster. Yes, I've done it, and It cost me a lot of time and money to undo the damage I caused.
Clean your clothes and shoes if you visit someone else's farm. You can very easily carry a disease from one place to another in the form of dirt, or droppings on your shoes or clothes. Bleach will destroy most organisms that may be on your clothes or shoes, use it!!!
Keep others a safe distance from your birds' environment. Friends and visitors can bring along problems just as well as you can. This is not to say "don't show anyone your birds". Just be aware of the consequences, and be careful. Don't invite them into the coops, and don't let your birds forage where visitors have been.
Be on the lookout for wild birds. A flock of birds, or sparrows eating your birds' feed can easily bring every disease from miles around. Avoid open feeders, and food scattered about. It's an invitation to all wild birds. See to it that they can't get in and out of your coops, stealing food and leaving droppings.
Control other animals such as rats, mice, wild birds, and predators. Cats that patrol your coops and yard could be regarded as disease carriers, but evidence has not been found o prove it. The benefits of having good old barn cats around definately outweigh the risks to your flock. A good hunting cat will do more toward helping your birds than all the mouse traps and poisons you can find!!!
Keep your compost pile at least 100 feet away from the birds if your can. Pathogens can easily be carried from the pile to your coops. Personally, I use my birds to "work" my compost. They scratch, turn it, and break it up. The heat of the pile being constantly worked controls fungus, etc., but it is a constant chore, and requires commitment and vigilance. If you don't work the pile daily, don't let the birds on it, the fungus will get them!!!
Vaccination is a matter of preference. I don't vaccinate, although I probably should. If a lot of people in your area keep birds, I'd suggest it. No one close to me keeps birds, so I'd rather not expose my birds to vaccines. Calculate your risk, and act accordingly. If my neighbors were raising birds, all my birds would be vaccinated!!!
One of my birds died, what do I do??? Have a necropsy done, and follow the recommendations.
Most colleges (Penn State is one) will do free necropsies for poultry keepers who have less than 500 birds. If you suspect a disease, make the call and take the drive. It may save you a lot of trouble, and if not, the results may ease your mind. Most diseases that your birds may get are not fatal, but lingering sicknesses that systematically drain your birds' vigor. This will make them more susceptible to other diseases. If they are already weak, they'll catch everthing that blows through!!!
Make room for your birds. Follow guidelines on how many birds to keep in your area. The fewer the birds on the larger the area, the better off you will be. Avoid the temptation to own one of every bird right now. Take your time learning the breeds you've chosen, then try some more next year. What happens is that new enthusiasts ALWAYS end up with too many birds in too little a space.
Sun and drying, rain and dilution help to keep the bad organisms in check. If your area has too heavy a load,the sun and rain can't do enough. It stays wet and stinky in coops that are too crowded. This brings flies and mold and bacteria, as well as sickness to your birds. A small population in your coop also makes it much easier to clean, and to care for.
Use Common Sense to protect your birds. A little "careful" will go a long way. If you can imagine a situation that could happen, it most likely will. You'll truly enjoy happy, healthy birds!!!