Blow Fly Infestations- What a BOT it?
Tuesday, August 11th, 2009I thought being in the South that I was safe from Blow Flies (Protocalliphora sialia) but alas after talking to a few folks and doing some research I am sure I have experienced a more sinister type of Blow Fly here at my colony.
A few weeks ago I posted about a nestling that had some sort of “lump” or cyst on its abdomen. The nestling died soon thereafter. Since then I have been doing a little digging into what it actually was. When I found the dead nestling it was quite apparent that the mass had opened and since I saw no other injuries or obvious issues with the nestling, that very well may be what killed the bird.
This led me on a quest to find out what may have been the cause. At first I thought they were Bot Flies. What is a Bot fly? Well, in short it is an insect that’s larvae lives as a parasite within the tissues of a living organism. Horses commonly get them as do other mammals. I have since come to learn that there is a type of subcutaneous BlowFly (Trypocalliphora braueri) or a type of Housefly (Philornis sp) that may be to blame.
I realized it wasn’t just me when I was reading my latest issue of “Feathers and Friends” (a magazine published by “The American Bird Conservation Association”) I read about several landlords reporting birds with “bubbles” that are “caused by an insect that laid eggs there and the eggs hatch into little worms” When I read this, It sure sounded like a BotFly.
I spoke with Mr.Terry Whitworth, PhD, who is the Adjunct Professor of Entomology for Washington State University. A portion of his email to me was as follows, ” There are two possible culprits in Florida, one is Trypocalliphora braueri, a subcutaneous blow fly. The other is Philornis, a Muscidae (a type of house fly) that occurs in Florida. By the time the larva comes to the surface where the bump can be seen the damage is done. Removing it or killing it at that point will not change things much for the nestlings. Neither pest is always lethal, it depends on the number of larvae that develop and where they burrow. I once took 25 mature Trypocalliphora larvae off a nestling junco and it survived long enough to fledge.”
Whether they be Blowflies, Houseflies or Botflies, whatever you call them, these nasty bugs can kill! 
Though not the same bug they are somewhat related. Some infest by way of laying their eggs or larvae into living tissue. Others crawl up through the nests and suck blood only to drop into the nest to grow then repeat the process. Getting larger and needing more blood each time. Usually a “Northern” plight, Blow flies can be controlled via nest changes as Sevin has NO affect on the larvae. A pair of forceps or tweezers can be used to pull these nasty things off of the nestlings. Once the Blowfly larvae are done feeding and growing in larval stages they form a pupal case in which they remain, dormant, until they are ready to emerge as an adult. Something like a caterpillar forming a cocoon before it emerges as a butterfly.
The typical BlowFly, can exsanguinate a nestling when present in large enough numbers but if caught early are controllable. These other guys (Philornis, Trypocalliphora and Botflies) however spell bigger trouble.
You think I am dreaming this all up? Read this article by The University of Northern British Columbia. (Be warned, if you don’t like bug pictures…don’t click) Basically it explains how death can result several ways. The Bot larvae move around and migrate in the soft tissue and can kill the bird, the wound itself can become infected and kill the bird, the Bot larvae will feed on the tissue and weaken the bird to the point of death, the Bot can damage the wings and thus, “produce an obvious awkwardness in locomotion, which may render them more susceptible to predation.” (that is a direct quote) In short the damage is severe and serious.
And talk about BiZzArRe? There is even a species of Bot Fly that lays its eggs on mosquitoes.When the mosquito bites the eggs are transferred. What does that mean? That means look out! Humans can get it too! Still don’t believe me? Just Google it. But that is another story.
What can be done about these subcutaneous (under the skin) Flies? Unfortunately, nest changes may not be helpful as once the adult Fly lays the eggs/larvae they crawl onto the bird and burrow into the skin. Another options is pretty gruesome and may not be legal. Also, it may cause more problems than it solves. Now, I could explain how the skin is cleaned with an antiseptic such as betadine prior to making a small incision from which the Bot Larvae is removed with a pair of forceps or tweezers but I wouldn’t want anyone with paranoia cutting holes in a purple martin with a wart. And legally, I think I could get in trouble for telling people to perform surgery on a federally protected bird without some sort of Veterinary license. All of this may be a mute point as once the larvae are large enough to cause the visible lump, the damage to the birds soft tissue is done. As www.kingsnake.com puts it, “They develop under the skin of some birds.The bird has died after…maggots have consumed much of its muscle tissues. Once their host is dead, the larvae leave it to pupate…”
In humans, the true Bot Fly wound (which is open so the larvae can breathe) could be covered with petroleum jelly or some other occlusive salve so that the larvae will emerge on its own, seeking air to breathe, after a day or so. I think that on a bird this course of treatment would not be successful. How could you place a dressing on a bird? We have the issue of a pretty dirty living environment (a nest) talk about infection! So, basically the wisest course of action would be to take the bird to a wildlife rehabber.
Of course we also have the problem of not really being sure which one of these 3 flies is the true culprit. Perhaps it is a combination of the 3, maybe some other. In order to find the true source of this problem I urge all that may witness this to photograph any lumps you may see on your nestlings and monitor them. Of course you can email them to me at the “Contact Us” section.
It is important to stress that with the classic and somewhat common Blow Fly infestations, that nest changes are by far the easiest and best treatment. Elevated subfloors help and nest trays make cleaning your purple martin bird houses super easy. Pulling off any Blow Fly larvae that are latched on to the nestlings with tweezers. For those of you that have questions regarding nest changes, this short video may help you overcome any trepidations that you may have.
Sources:
If you want to learn more about Blow Flies or help with blowfly research go to www.birdblowfly.com for some interesting facts.
The American Bird Conservation Association / Feathers and Friends can be contacted via phone at (260) 768-8095 x:5 Subscription rates are $18 for 1 year. Tell them Susan from PurpleMartins-R-Us sent you!
http://www.kingsnake.com/westindian/metazoa7.html
©2009 S.Halpin / PurpleMartinArt.com
