Fly Bots (Warbles or Cuterebra)
Dear Dr. Moffat: Help! Ewwwh. This is weird. I’m looking in what looks like a little hole in my cat’s skin and I see something moving. Gross! What on earth is it? Should I take my Chloe to the emergency room? Please answer quickly. Thanks. Emil in Oregon.
Dear Emil. This sounds like a Cuterebra bot emerging from its breathing pore (also called a warble). Yes, very gross. Even grosser is to put a bit of local anesthetic in the hole, enlarge the hole a bit then reach down with a pair of forceps and pull the chubby little thing out and instill some antibiotic ointment of some kind to prevent secondary bacterial infection. Although not considered an “emergency” this is a process not for the squeamish, let me tell you! You should schedule for an office call as soon as possible before the larvae emerges and drops out on the floor somewhere. . .On second thought I can see how this could be considered an emergency for some people. Ick. Here’s what I know about bots:
There are about 26 different species of flies that produce bots within the United States, Canada, Mexico and neotropical regions.
Out in the field (that is large animal medicine) the birds often do this for us. Have you ever seen a bird sitting on top of a horse or cow out in the pasture? Sometimes they do this to get a free meal. (Kind of gives a new meaning to the Warbler bird name, doesn’t it? And Michael wondered if Bothell, Washington was named from someone’s bot experience. Just having some fun here. I can’t help it.)
Symptoms associated with bot infestation: Flies and their associated larvae can cause lots of economical damage for the farmer and physical damage to the livestock with the associated inflammation, edema, damage to the hide, pneumonia, bloody nasal discharge, secondary bacterial infections and sometimes even death due to neurological damage (which is often misdiagnosed by panic stricken public and labeled as Mad Cow Disease.) Sometimes the livestock get so nervous and exasperated by being chased by flies trying to fly up their nose they stampede. It’s just a bad situation.
Bots or warbles are the larval stage of the botfly, which characteristically infect rodents and rabbits. They are found under the skin, usually around the legs and neck. They have also been reported from deer, cattle, cats, dogs, goats, squirrels, hogs, mules, mink, foxes and man. They look like grub like maggots and are one to one and a quarter inches in length. They can be seen almost any time of the year.
Their life cycle involves certain North American flies including muscoid fly, bot fly or nasal bot fly that places an egg or larvae onto a mammal host. The larvae migrate through the body feeding on mucosal tissue, flesh or secretions of the body and emerge out of the nose or skin as a pupae (depending on which animal species is infected) as a pupae. This stage then falls onto the ground, develops a bit further into a young adult fly—if it isn’t eaten by a bird first. This process can take anywhere from 10 weeks to a year depending on the temperature and time of year the animal is infected.
Cats and dogs get infected with them by eating rodents, rabbits, chipmunks and squirrels. Usually these critters are kind of slowed down because the larvae have migrated into their nervous system and they can’t get away as quickly so are easier to be caught. The problem is that when our pets eat these infected animals they can become infested by both the larvae of the fly AND they can also get weird bacterial infections from the rotting flesh that they’ve eaten. (The antibiotic Baytril is great for these kind of infections by the way. Herbal medicine just takes so long to kick in that this is one situation where I do recommend antibiotics.)
Humans can become infected by the Muscoid fly. It goes for tear secretions and the larvae can penetrate the eye tissue.
Treatment: Natural treatments don’t seem to work for bot infestations. Ivermectin is the treatment of choice for those animals with persistent, debilitating symptoms. I’ve also read that mid-summer dose of garlic in the feed can cut down the incidence of bots. I don’t know the dose for this however. Explore this link for more info on that: https://www.skylinesfarm.com/parasitenasalbots.htm
Here is a photo of different bots:
Picture of a deer nose bot (Cephenemyia)
We were taught in vet school that if these were present to just cut out that portion of the meat and that the rest of the animal carcass was safe to eat. Gee, that kind of makes one want to become a vegetarian, doesn’t it?
Picture Reference for these nasal bots:
Cuterebra in a rat emerging bots: https://www.k-state.edu/parasitology/625tutorials/Arthropods24.html
Other Helpful Links and References:
*Sheep and Goat bots: https://www.oznet.ksu.edu/dp_entm/medical
*Bots in wildlife: https://www.unbc.ca/nlui/wildlife_diseases_bc/flies.htm
*Bird Bots: Blowfly and birds from Cornell Laboratory of Ornithology