Disease/Infection ID on a Great Tit

[Bobbobthebob]

Bit of a long shot, but does anyone know what would cause such extreme growths on a great tit? I was wondering if this is caused by a well-known disease/parasite or it may just be a tumour.

If you are upset by photos of sick birds, I wouldn't advise clicking on the photos below.



Thanks in advance.

[RKB]

It's actually quite rare - rare enough that nobody is sure what it is yet. This was first reported on juv Great Tits in Cambs in 2007. Neither BTO nor IoZ have any experience of it. It has reappeared in each year, on very few birds, but always juvs Great Tits. They tend to die by the New Year, as the lesions are progressive and invasive (the birds can lose eyes). No clinical sample has been gathered yet (it's unpredictable whether you'll catch one), but the best theory so far is that it's caused by a bacterial infection of a mosquito or tick bite.

It's a very unpleasant infection, and usually affects the head (esp around the eyes), but can also appear on the wings, scapulars and legs. It starts off as a small pimple, then grows into these large invasive growths, which are fleshy but have a yellowish cheesy core. What is perplexing is that it has never been seen on any of the other tits living alongside the Greats.

After Birdwatching magazine published a letter, there have been a couple of reports on Great Tits in Kent and Surrey, and possibly a Dunnock. Can you tell me where your bird was?

[Bobbobthebob]

Wow, that's quite a quick and detailed response. Thank you!

I took that photo on the 9th of January at the Sevenoaks Wildlife Reserve, Kent. I'd seen it there on a visit about three weeks previously as well although the growths weren't so massive at the time. On both occasions it was hanging around by the feeders near the hide by the information centre.

[RKB]

Ah, Sevenoaks is where it's been reported from already. You didn't happen to report this on another website, did you, and were directed to email somebody? if so, you might recognise the initials!

[Cheryl]

I've not heard of this disease before - if we see it should it be reported, and if so to whom?

[Bobbobthebob]

No, that must have been someone else. It's quite a conspicuous bird and was hanging around the first hide you come to on arriving at the reserve so it's not surprising that someone else has brought it up.

[Dogghound]

It Looks like avian pox to me, this is often seen in tits.

[RKB]

Originally Posted by Dogghound

It Looks like avian pox to me, this is often seen in tits.

It definitely isn't avian pox.

[Dogghound]

Originally Posted by RKB

It definitely isn't avian pox.

Why?

[RKB]

Originally Posted by Dogghound

Why?

Because avian pox looks very different to this, creating clusters of hard greyish knobbly warts. These are fleshy lobular growths with a cheesy core, usually with an apparent 'entry wound' on the top, and do not affect the toes (as pox does). Pox is viral, the gunk inside these growths strongly suggests a bacterial cause, and the entry wound suggests an insect vector.

I've examined about 30 of these birds so far, and it's definitely not pox (which I am familiar with).