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What is PDD and why is it such a scary disease for birds? Is Joy the blue and gold macaw sick? Jessi explains how the disease affects birds and how it's impacting life at Animal Wonders.

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Around ten years ago, I heard about a very scary disease for parrots.  It's been in the back of my mind since then, but it's now very prevalent in my life.


When I opened my rescue organization in 2008, I was very aware of this disease.   It was super contagious and there was no cure available, but there were also no tests available to pre-screen an incoming rescue.  At the time, the only way to know if a bird was infected was to do a necropsy, which is postmortem, basically after the bird has died, they could test the tissues, so of course this disease was very concerning when rescuing birds with unknown histories.

So what is this super scary disease?  It's called proventricular dilation disease, or PDD for sure.  It all starts with a virus called Avian bornavirus, which is distantly related to rabies and herpes.  The virus goes into the digestive system and/or the neurological system.  The bird's immune system goes into overdrive, causing inflammation, which results in loss of motor control and an inability to absorb nutrients from food.  Once these symptoms present themselves, the bird never survives.  

The reason PDD was so scary for a rescue organization like Animal Wonders is because we often rescue animals that have a completely unknown history.  Oftentimes, they look really unhealthy when they come in.  We don't know where they came from or how many other birds they've been exposed to, and we don't know if they've been around infected birds.  So while we do quarantine new rescues for at least 30 days and run them through a physical exam and send bloodwork to a lab, for the first few years we were rescuing birds, we had no way to screen for the Avian bornavirus or PDD.  

Birds with PDD symptoms usually have dirty feathers from constant regurgitation.  They might be shaking or wobbly and they look depressed or lethargic.  Some of the birds we've rescued have looked so sick when they've come to us that you might think they had PDD, but after a month in quarantine with plenty of nutritious food, a couple showers, and a clean environment, they perk right up and look healthy and happy, so our policy was to do everything we could to screen incoming rescues while still offering homes to those in need.

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Over the years, we've had a few of our birds pass away despite being overseen by an avian vet and diligent care from us.  When an animal in our care dies, I like to have our vet perform a necropsy to see what was the definitive cause of death.  The two passings that stand out to me are our two sun conures, Louie and Oliver.  

We had them at separate times, but both passed away from symptoms that were very similar to those of PDD, so we sent their bodies to a lab to have them tested for the virus.  Both came back to us as not positive for PDD, which was a relief, but it didn't help us understand why they had died.  It was frustrating not knowing if we had done something wrong with their care or if it had just been a random illness that took them.  

Birds are different from other pets because they're so sensitive to things that more common pets like dogs and cats aren't, like scented candles and incense, foods like avocado, and even some kinds of metal that we use in our cookware, and if they do get sick, it's hard to help them, because they'll hide symptoms until it's so far along, it can be too late for treatment.  Also, avian vets are not as common, so experts are difficult to find.  

I haven't thought about PDD for a couple years.  None of our birds have died and we haven't taken in any new rescues, so I haven't been keeping up with the newest research, but when of our birds started acting unusual, we decided to take some tests to see if anything was out of the ordinary.

Joy, our blue and gold macaw, has had ups and downs with overgrooming the feathers on her chest, but in the last year, it's gotten worse, despite increasing her enrichment, time outside, interaction with her favorite human, a nutritious diet, and a clean environment.  Joy's bloodwork came back looking great.  Nothing out of normal levels, so she's healthy, but she tested positive for Avian bornavirus.  This was a total surprise, so I had a good talk with our vet and did some searching to see what the newest news was on PDD.

First, the biggest news is that it's now possible to test for ABV while the bird is still alive.  

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A simple blood test or swab can see if they have the virus.  Second, when a bird tests positive for ABV, that doesn't mean they're going to immediately get the symptoms and die from it.  Parrots can carry ABV and show no symptoms for many years, but even if they have no symptoms, they can still spread the virus to other birds.  The third thing I learned was some birds can carry the virus for their entire lives and never get the devastating symptoms that lead to their death.

It turns out that the majority of parrot type birds being cared for in captivity in the United States are infected with Avian bornovirus, which is what causes PDD.  60-70% are carriers of the virus, but only 5% will develop the deadly symptoms of PDD, so as far as scientists know right now in their research, it comes down to the individual bird on how their immune systme reacts to the virus.  Some will form antibodies and nothing more comes from it.  Others' immune systems will over-react, causing severe inflammation of their digestive tract and nervous system, which is what leads to their death.  Others yet will seem fine for years before suddenly presenting the devastating symptoms.

So what does this mean for Joy and what does this mean for all the other birds at Animal Wonders?  Well, I'm scared about what Joy's future looks like.  Is the increased plucking the first signs that she's going to develop the fatal symptoms of PDD?  Do the rest of our birds have the virus, too?  It's pretty likely they do, since they all live together.  We have no idea which bird brought the virus in, so we don't know how long it's been around.  

So should we test everyone, and if we do, what would we do with the information?  If we found out that all the birds carried the virus, there are still no treatment options.  We're still in the process of figuring out what the future looks like for the birds at Animal Wonders, and I wanted to let you know what's going on, because I think it's so helpful to see how other people and animal facilities handle challenges they encounter.

I wish I had a clear course of action ahead, but like with many things in life, it's complicated and we have lots of things to take into account.  One thing is absolute though: We will continue giving Joy and all of our birds the best nutrition, engaging toys, adventures outside, companionship from their flock and best friends, and regular check-ups from their avian vet.  

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In other words, the happiest life we can provide, and that's my promise to all the animals in my care.  Even though there's a chance that all of our birds might carry the virus, that doesn't mean they can't live good, happy, and healthy lives, and that's what I'm going to focus on.

Please send Joy and all of her feathered friends some love in the comments section.  I'll be sure to share it with them.  Thanks for letting me share what's going on.  Even when things are challenging, I'm glad I get to go through them with you.  If you'd like to continue going on adventures with me and the animals, be sure to subscribe and if you'd like to support our channel, you can go to and join our amazing community there.

Thank you and we'll see you next time.