Most flies we see are House Flies and deer flies, which bite but normally don't pass on disease, at least not that I have seen. They may lay their eggs in an open wound, but actually benefit the animal as the maggots will eat the flesh, keeping the wound fairly clean and free of infection. Treatment involves removing the larvae/maggots, cleaning the wounds and antibiotics to ward off any secondary infection.
Fly strike is a problem mainly seen on dogs who spend alot of time outdoors, where the flys target the tips of the animals ears. Prevention is the solution in these cases.
Then there are Cuterebra. These are flys that look like House flies on steroids. Big house flies. They don't bite. Their normal MO is to frequent rabbit and rodent runs, where they lay their eggs which get picked up on the fur of the critter, or land on an unsuspecting critter, and lay there eggs there.
Then, the eggs, being warmed by the heat coming from the animal's body, hatch into larvae.
The larvae then crawl up the hair shaft to the skin, where they enter a wound or chew their way into the animal's skin, where they stay for a while, to feed and grow. They keep a hole open to the outside, because they breathe air, and if one watches, one can see the head pop out intermittently. Again, the wound will stay free of infection, as the growing larvae munches happily on surrounding tissue.
At some point, the larvae drop off to continue their life cycle in the dirt, and the injury will most likely heal up.
The major point of concern is that should the larvae be damaged while under the animal's skin, either by the animal scratching or during attempted removal, it will result in acute anaphylactic shock and death.
My story:
My Yorkie and Shepherd used to lay behind a shed, in the shade. One day I walked past, and noticed my Yorkie was literally covered by flies! Big, black flies. He lay there asleep, not bothered by them at all! That's weird. I woke him up and brought him in the house.
I looked him over, but all I could see was a ton of really tiny oblong white specs, all over him. I thought it was danduff, or something from his skin, so I began brushing and combing him, and gave him a bath.
Weeks later, we were all in bed, my precious Yorkie on my chest as I was falling asleep. I reached up to scratch him behind his ear and felt something wet? In the dark, I tried to look at my hand and saw something dark, and thought OMG! Blood! Well, you all know how fast Yorky Mamas can fly out of bed, deep sleep or no, to check on our little ones, I am no different.
Into the kitchen, baby in my arms, flipping all the lights on, blinking frantically trying to get my eyes to focus... I put him on the kitchen table to investigate. Tooth abcess, skin abcess... found the source of bleeding, bright red blood... not making sense... sniff the area: it doesn't stink, hardly smells at all! (Abcesses smell badly). Oh no! A wound! My baby was bitten by something! Or snagged on something sharp! Okay, okay. Calm down. Look again, not spurting blood, more draining. So I go grab stuff to clean him up... I see what looks like a large (dime sized) pimple with a hole in the center. So I squeeze it ever so gently to see if anything comes out.. nothing. Dog does not seem to feel any pain. Hmmm.
So I'm looking to see if it's going to start draining again, and I see the lump moving? Blinking eyes again.. wake up! Look some more, something light colored in the center and disappears! OMG! A maggot! Ew!
And, in hindsight, I never should have done this, but I did remove this larvae from my dog's neck, in one piece, and went back to bed.
In the morning, I called the vet, and off we went, my baby and this nasty worm thing in hand. She said what is was, told me to look it up online: Cuterebra. He was fine, no antibiotics (huh?), and back home. The wound healed up in 2-3 days. Gone! No trace what so ever!
And the next Spring he had another one! But this one we caught early, so it didn't get quite so messy. And we went right to the vets.
I never ignore my dog's scratching anymore. I always investigate. Put rabbit guard fencing up around the yard. Those were two years that it seemed we had a ton of rabbits in the neighborhood. Pretty much outside the city, but not country either. Not as many rabbits this year, Thank God. And I'm always on the look out for those flies... and white specks on my dog...
http://www.petplace.com/dogs/cutereb...ogs/page1.aspx