This particular disease is shared in any number of ways - with dusty birds like Cockatiels and Cockatoos, most humans inhale the particles from feather dust. The symptoms in humans are similar to that of the flu. It can be treated for both parrots and humans with a trip to the doctor or avian vet, but prevention is the best policy. Have all new stock tested and quarantined (we recommend at least 45 days) before adding to the aviary. Keep cages clean, keep an appropriate ratio of bird to cage space, feed a healthy diet, and see your avian veterinarian regularly, especially for breeding birds. The incubation period in birds for Chlamydiosis can be years, so simply quarantining a bird is not an adequate step by itself.
Another zoonotic disease parrots have is Salmonella. It's much more common to obtain Salmonella from eating an infected bird than from your personal pet bird, but there is still a risk, so it's worth mentioning. And it's not an unusual disease in pet parrots like you might think. Salmonella is treated with antibiotics, and can be difficult to diagnose in parrots, because you won't find it in every dropping. That just reiterates the idea that you need to regularly see the avian veterinarian, to establish baseline readings and to keep checking for diseases that may not show up the first time. Birds can and do die from Salmonella, and symptoms are similar to a human's, with diarrhea (bloody or not), vomiting, lethargy - pretty much like food poisoning.
One zoonosis I've had experience with is Colibacillosis, or E. coli. People tend to get themselves worked up about E. coli, but E. coli is found in the intestinal tract of animals. Including humans. It's completely natural. The problems begin when you have an overabundance or an infection of E. coli. Symptoms in birds and people generally start with diarrhea. Of the diseases I've listed, this one is probably the most common, and frequently overlooked as so many bird breeders don't properly check their stock.
Other zoonotic parrot disease of note include:
- Avian Tuberculosis
- Newcastle Disease