Cuterebra Chronicles: Inside the Parasitic World of Bot Flies
Welcome to an informative journey with Dr. Sugerman as he unravels the fascinating world of cuterebra flies, also known as bot flies. Get acquainted with their intricate life cycle, understanding how they inadvertently infest our beloved pets. Explore the clinical signs that may indicate an infestation and discover essential treatment options. Dr. Sugerman emphasizes the importance of not attempting removal at home due to potential complications and highlights the significance of prevention. Dive into this comprehensive guide to gain a better understanding of how to protect your furry companions from opportunistic parasites.
What You’ll Learn:
The life cycle of cuterebra flies, also known as bot flies.
How cuterebra flies inadvertently infest pets, including the specific host animals they target.
Recognize the clinical signs of cuterebra infestations in pets, both on the skin and when they affect the central nervous system (CNS).
Explore treatment options for cuterebra infestations, with a focus on safe removal techniques.
The potential risks and complications associated with attempting at-home removal of cuterebra larvae.
Insights into the importance of prevention during peak cuterebra season, especially for outdoor pets.
Information on specific medications and prevention strategies to keep pets safe from cuterebra infestations.
A deeper understanding of the unique behaviors and effects of cuterebra flies on various animal species.
Ideas Worth Sharing:
“Don't panic at the sight of some weird bug sticking its head out of your pet's body. We veterinarians are here to help.” - Dr. Tyler Sugerman
"But it is crucial not to try to remove these creatures yourself, as rupturing the larva can actually cause some severe complications." - Dr. Tyler Sugerman
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Read The Transcript:
Dr. Sugerman: [00:00:00] Hi, and welcome to Vetsplanation. I'm your veterinary host, Dr. Sugerman, and I'm going to teach you about veterinary medicine. In this podcast, we can dive deeper into the understanding of what our pets are going through and break down medical terms into easier to understand chunks of information. Just a quick disclaimer, this podcast is for informational purposes only.
This is not meant to be a diagnosis for your pet. If you have questions about diagnostics or treatment options, please talk to your veterinarian about those things. Remember, we are all practicing veterinary medicine and medicine is not an exact science. Your veterinarian may have different treatment options and different opinions.
The information I provide here is to help pet parents have a better understanding about their pets. If you like our podcast, please consider sharing this podcast with at least one friend or just somebody else who has pets as well. Now, let's jump into this week's episode.
Hey everybody, welcome to Vetsplanation, your weekly veterinary podcast where we simplify the [00:01:00] intricate world of pet health. I'm your host, Dr. Sugerman. So this week we're going to be discussing a parasite that invades our furry friends in the most curious of ways.
It's called the cuterebra fly. So grab your coffee, buckle in, and let's get right into it. I am going to warn you really quickly that if you are a squeamish person, that this may disturb you a bit, so you might not want to listen to this one. Have a friend listen to it and then tell you the details.
Otherwise, if you're a person who likes like Dr. Pimple Popper and stuff, then you should actually watch the YouTube version of this that I do, because we'll have some pictures and stuff on there for you. All right, so let's jump into this. Now, I imagine that some listeners are recoiling at the mention of this word, parasite, right?
This is a fly larva in pets. I have actually seen this quite a lot this year. Cuterebra is the fly that we're going to be talking about. It's also known as the bot fly. It's found usually across Northern America, and has been found in some other places as well, but mostly in North [00:02:00] America.
And it strikes usually in the summer to fall months. So an innocent outdoor frolic can actually like wind up being a not so pleasant experience for our dogs and cats when they encounter these things called opportunistic parasites. And we're going to talk about more of that later.
So it is important to know what you're dealing with. First we're going to dive into the life cycle of what a cuterebra fly is so we can get to know them a little bit better. So A cuterebra is actually a specific type of fly that infests usually rabbits and rodents. These flies are actually very host specific, meaning they like a very specific type of animal to lay their eggs into for very specific reasons. Usually if they lay it into an animal that is not that host animal or that specific animal, they don't actually become what they want to become. So the fly lays the egg. That egg then becomes what's called a larva, and then that larva will then become a fly. But if they don't lay it in the right [00:03:00] animal, a lot of times that larva will not become that fly. Ideally that fly wants to lay it in that target species. The actual adult cuterebra fly, they only live for a very short period of time, just a few weeks.
The cuterebra fly Isn't interested, like I said, in directly infesting your pet, that poor pet is merely just like an accidental middleman that just happens to get infested with this. After the fly goes and lays its eggs, it actually wants to lay it near an animal's burrow or its nest. So one of those rabbits or rodents for our specific when we're talking about today and the heat of that rabbit sitting on its nest will stimulate those eggs to like hatch into a larva. That bot fly may even lay eggs down like a path that a rabbit would normally go down to or on stones or vegetation around where they would normally eat.
So that way as the animal just like crosses through that path. Those eggs feel the heat from that animal. And that's what stimulates the [00:04:00] eggs to hatch open. Now that the egg like hatches, it turns into something called a larva. The larva then enters the body.
So it does it in many ways. Mostly through the nose, the mouth or open wounds, but it can also enter through the anus or the vulva as well. Those larvae then move through the skin or into the skin. This is called migrating. And when it reaches the skin, it makes like a little hole. That's called its breathing pore.
That's the area where it actually opens up so that way it can like breathe air. After about 30 days of hanging out in the skin, the larva will wiggle out of the skin and is looking to landing in the soil so that then they can pupate or basically become a fly. So with the bot flies, if it goes to a rabbit or a rodent, then it will be able to become a fly.
But if it doesn't, if it gets into a dog or a cat or ferrets are also ones that are also known to get these, but dogs or cats it [00:05:00] will actually not turn into a fly most of the time. So , the fly does not want the dog or the cat to pick up the larva.
It really wants a rabbit or a rodent. It just happens to be that the dog got it instead of the cat got it instead. How will you know if your pet has been invaded by 1 of these cuterebra?
You might actually notice a small hole. With like pus around it or on the pet skin. That's usually where the larva are nestled into. The hole will usually have hair matted around it too. So that's a lot of grooming and stuff that the pet has been doing. Cats will often like, groom this area excessively.
We assume it's due to some pain because, there's a hole now in their skin, but also there's some dead tissue that's in there as well. So that's what the larvae like to feed on. So we assume that it's from pain. In dogs and cats, they're normally found mostly around like the head, the neck and on their body.
Not so much so like on their legs and stuff, but I have seen them [00:06:00] occasionally there and I have seen them near the vulva as well. It can also go to other places though. So it can go to the brain. To the nasal passages into the throat or even into the spinal cord and the eyelids. These are actually commonly diagnosed when it's under the skin as like an abscess or a foreign body.
Especially if the hair isn't shaved to look at the wound. These most commonly happen around the end of summer or early fall, hence that's why I'm talking to you now. It's fall for us. Usually like between July to September in most areas.
In areas that are always warmer though these can be year round. In Florida and Southern California, for example. So hello to my Florida and California friends and family. Sorry about your cuterebra. They're all year long. But it is crucial not to try to remove these creatures yourself, as rupturing the larva can actually cause some severe complications.
We're going [00:07:00] to talk about that more in a second, but I just really want to put that out right now, so that way nobody tries to self diagnose, and then stop this podcast, and then we have a much bigger problem. Alright, so now, more on to what clinical signs we're going to see. So we talked about our ones in the skin.
You'll usually see a little hole. A lot of times they'll be like a little thing popping in and out, like a little bug it looks like popping in and out. And that's what the cuterebra butt or the cuterebra larva are. But in other animals, let's say we have this a lot in outdoor cats or not a lot, but we have this in outdoor cats.
This can be a problem where they actually have these CNS signs. CNS stands for central nervous system or basically things that are involving your brain. So I talked about how it can go to the brain and the spinal cord, and this is what happens with them. So it usually starts that the cat will be like violently sneezing for a few weeks, usually about two to three weeks, or it might seem like they have an upper [00:08:00] respiratory tract infection, and then it progresses to these CNS signs or neurological signs.
They'll be depressed, lethargic, meaning that they really don't want to do anything, they don't want to move, and they may even have an abnormally high or low body temperature. They might seem like they're blind, or they have a head tilt, and they can even have really bad seizures.
These type of seizures are called status epilepticus, where they can't get out of the seizure, no matter what medication I use to try to get them out of the seizure. But it'll just be seizure after seizure. Oddly, Yorkies also have a high rate of infestation over other dogs. Yorkies can have a huge systemic inflammatory response to it, meaning their body starts to almost shut down because of all the inflammation that's being created.
They can even go into something called DIC. I'm not going to go into DIC because it's extremely complicated and very difficult to explain. So that'll be another episode way down the line. But [00:09:00] to give you an idea of how bad it is, we say that the, so the acronym actually stands for disseminated intravascular coagulopathy.
But we actually say that the acronym should stand for death is coming. It's not very good . So for us to diagnose cuterebra, if it's under the skin, it's usually just means shaving the hair and then finding that little opening. When you find that little opening, we'll see that little cuterebra popping in and out there, that little pupae popping in and out, and that's pretty much the easiest way to diagnose them.
Sometimes there isn't quite an opening yet though, like it is still migrating through there, so it can be much harder to diagnose in those situations. We might think that it's like an abscess and probably just start antibiotics or try to open it with a scalpel. So we can open it to see if there's like pus and stuff in there.
But most of the time it can be pretty easy to diagnose when that little hole is right there. If it's in the brain, then a CT scan would be what we would need to use to be able to find what's in there. [00:10:00] MRIs can be helpful as well because it can actually like track the area that I migrated through and also if it's something like they're sneezing over and over again, a CT scan will be great for that because you can hopefully see that there's something in there.
All right, let's talk about our treatment for this. It's really about the removal process of these cuterebra. It isn't complicated, but it does require like a really steady hand and also the pet to be sitting still. What we'll do is we'll usually have the pet under sedation so that way they aren't moving and it's not so painful.
And they will like carefully enlarge the hole and draw out that little larva with some forceps. So that way we do it very carefully as to not crush it or pull it apart. And after we get that larva out, then we'll clean that area really well.
Cause like I said, it likes to feed off dead tissue. So there is dead tissue at the bottom there, and we want to clean that all out. And then if you're [00:11:00] wondering like how, if you like try to figure out like how this is in the body, cause I'm like, Hey, the feeds at the bottom of the hole and it's air is at the top of the hole.
Your mouth and nose are not at two different places, right? So the mouth is at the bottom actually feeding and the butt area is at the top, and that's what it's breathing through. If we can pull that out really easily without it coming apart or anything, that's great. That's really all we need to do to be able to cure this.
We just need that little cuterebra larvae out. Now remember though how I said that you should not try this at home? The reason why is because if you squeeze the skin where that lesion is or you rupture the larva by trying to pull it out, it can actually cause anaphylaxis, which is very bad if you're not in the vet clinic.
Because we can treat it immediately if that does happen. Because, unfortunately, that does happen sometimes, even with us under anesthesia. If you squeeze just a little too hard, and these are like really soft little things, then it can definitely be difficult to be able to get [00:12:00] them out. And if you squeeze too hard, rupture it, it'll cause this anaphylaxis.
Otherwise, if the pet does not get anaphylaxis, there are also abscesses that can form if you don't get all of it out in one piece. So you'll see like that abscess form and then we put them on antibiotics and it goes away, but that piece is still left in there. So it forms another abscess over and over again until that piece has been taken out.
Now that's the skin one. So how do we treat cats and dogs who have CNS signs or those neurological signs we were talking about? This is definitely a hard one, so it means usually what we first do is after we've diagnosed that's what it is, we give them a dose of Benadryl, so that's called Diphenhydramine is the other name for it.
We give them a dose of Benadryl and then an hour or two later we give them Ivermectin and we give them a steroid. It's called Dexamethasone usually. Now. Why don't we do this with, like, all cats who have seizures? Ivermectin is not [00:13:00] actually approved for cats, so I would have to talk to that pet parent about the risks of doing this, because if, and it's really just based on the owner and what they see at home.
If they did see that the pet was having really severe sneezing for a while beforehand, a couple of weeks beforehand, or we were having discharge from one side of the nose. And then now we're starting to have seizures. And I think that there's a pretty big risk for cuterebra if that's the case. Especially here if it's in fall or late summertime. Then, ideally, the best option is we do a CT. We find out that's truly what it is. We give the medication because we know that it will hopefully work for this pet. But I understand that not all pet parents can afford a CT.
So if our only other option is to put the cat to sleep or the dog to sleep, then I think it's worth trying it. But like I said, they could still have an anaphylaxis because of this. Giving the Benadryl and the steroids are what's going to help prevent the anaphylaxis. And Ivermectin is a drug to help rid [00:14:00] that parasite, gets rid of certain parasites, not all parasites, but certain parasites. So our goal would be to see if it helps, but if it doesn't help, then the pet parent understands that we might have to put them to sleep if it doesn't help. Ideally we want to try to do things the safest way possible, but sometimes we just have to do alternatives just to try to help the pet.
All right, I'm gonna talk about some like the most commonly asked questions real quick because especially this really pertains to treatment of it. The most commonly asked question I get from our receptionist is whether an owner can remove it at home.
So yes and no. It would be best for the pet parent to bring their pet in for us to do it. As I said, it can cause anaphylaxis, or that severe allergic reaction. It can also cause, abscesses by not getting all of it out, but also your pet has to sit really still to be able to do this.
So for those that cannot do that, though, if they are just cannot afford to bring them in, there is something you [00:15:00] can try at home. It doesn't work all the time, but it is something and it will require a lot of patience on your part. So first you can put like neosporin or triple antibiotic ointment over the hole and then have something that you can put over it. So think like a small like tube that only has a hole on the top. Basically, think about a glass, how it has glass on all sides and then just has a hole on the top. So something like that, even smaller than a shot glass, though, like this needs to be pretty small, like a thimble size would be best.
You can put that over the hole of your pet skin and hold that on there. The goal is that we're trying to make that larva run out of oxygen. So if you have a big glass and you put it over there, it's going to take hours for that to run out of oxygen. You need something really small so we have less oxygen in there.
But basically you put it on there and you hold it on there and it's going to take somewhere between 15 minutes to even an hour, depending on [00:16:00] how big of an object you put on there. So if you put like a big glass, it's gonna take hours. If you put a shot glass, it'll probably take at least an hour, maybe still a couple hours.
So something really small just to hold it over there. And then you cannot let any air in, so you have to be able to hold it on there very steadily. If you move a little bit, or the dog or cat moves a little bit, and air goes in there, your time has essentially started over again. You want to hold it on there, and then you just wait until it pops out.
And once it pops out, take it off, and then you can clean that area. To clean it dilute iodine or betadine kind of works the best. It needs to be really dilute. Dilute tea is what you're looking for. But don't use like peroxide or alcohol. Alcohol stings a lot, first of all. But peroxide and alcohol will kill off good cells, not just bad cells. So ideally use iodine or betadine.
The second most common question I get is this contagious? No, once the larva is in the animal, it [00:17:00] cannot be transmitted to another animal or to you. It can only happen if that animal or you or somebody comes by and goes through a newly hatched larva and gets that on their skin or their mouth or their nose and then that moves to other places.
It's not going to be contagious to your other animals. All right, let's talk about the biggest thing prevention. So prevention is better than the cure. In this case of the cuterebra infestations, regularly checking your pets after they've been outdoors can potentially be a lifesaver for them.
It's hard though, because if it's in their mouth or their nose you're not going to know that, right? And of course, keeping your pets indoors during cuterebra season, primetime, late summer and fall can significantly reduce that risk of infestation. But unfortunately, there's no medications like flea medications that are labeled to specifically control cuterebra.
It has been shown that some flea meds containing Fipronil, like Frontline. Imidacloprid, [00:18:00] like canine advantix and the macrocyclic lactones like ivermectin can protect and possibly kill the larva as they're migrating. Now, there are lots of medications that contain these, but that is not my specialty.
ER I do some. I can take out the cuterebra but prevention for medications is definitely not my specialty. I do want to have somebody on though, who is going to be able to talk more about that. So we're going to have Dr Z on in a couple of weeks. Who was like my go to for all parasitic prevention.
We just heard her in our other 2 episodes. Talking about health certificates and diabetes. So she's going to give us an insight on some parasite prevention in a couple of weeks here. I also want to warn to please check the package of the medications. Some people will get over the counter medications or even get medications from the veterinarian, but you have to make sure that if it says [00:19:00] for dogs only.
That you do not give that medication. If it's one that's over the counter again still like it'll have a cat with a cross on it or it'll say for dogs only or it'll say do not put on your cat. Like usually they'll say something that tells you it should not be put on a cat. I've previously talked about flea med toxicity in cats and episode 33 Permethrin poisoning in cats.
So if you want to know more about that, we want to make sure that we keep our cats safe All right, so our main takeaway for today, don't panic at the sight of, some weird bug sticking its head out of your pet's body. We veterinarians are here to help. Armed with the knowledge of how cuterebra operates, you can now keep your furry friends safe and sound, right?
So for our fun animal fact of the day, I actually stuck with cuterebra. I feel like because it's really interesting. I know it's not an animal that we normally think of. It's an insect, right? But I just thought that it was very interesting because there's so many different [00:20:00] types of these little cuterebra type bugs that are out there, flies.
There are other types of botflies, like horse botflies, they're ones that they attach the egg onto the hoof or the around the leg of the horse.
So the horse will come and like chew on that bot fly and then swallow it and then it'll go to other places like it goes to the skin, but it also goes and infests their intestines and stuff like that. The other interesting one that I found was, I did not know about this one, but there's one that affects tree squirrels.
It's called the cuterebra emasculator. Just in case you wanted to know what the cuterebra was of the other one, the one that affects like rabbits. That's the Cuterebra cuniculi and then this one is the Cuterebra emasculator. So this one attacks the scrotum of the squirrels. So it essentially can emasculate them.
So it castrates them. Crazy. The other one that I thought that was just interesting was the human botfly. [00:21:00] I didn't know that there was a human botfly one. That's the Dermatobia hominis. It attacks things like livestock and deer and humans.
So the female actually doesn't even attach the eggs to anything in particular. Like not to like the nests and stuff. Like we think about with the cuterebra that attacks the rodents and rabbits, it actually attaches the flies to other animals. So it'll attach the eggs to the mosquitos or stable flies or other insects that then carry the eggs to the actual host that it wants to attack and then the body warmth causes those eggs to hatch into the tiny little larva and then those penetrate into the skin.
So weird little flies. All right, guys, that is, I'm not going to go too much into all the other bot flies. I just thought those were the interesting ones.
Alright, this wraps up our discussion today on Vetsplenation. Thanks for joining me, and as always, I'm Dr. [00:22:00] Sugerman your guide through the intricate world of pet health. So catch you on the next episode, where we'll be untangling yet another intriguing facet of our pets lives. And just to let you know for what's coming up in the next couple of weeks, we're going to have things like...
Talking about Addison's and Cushing's disease with Dr. Z again. We're going to be talking to a pathologist who does necropsies. So I'll warn you when that episode comes up. And then otherwise until then, keep your pets happy, healthy, and safe. Thank you guys.
Thank you guys for listening this week. If you have any questions, comments, suggestions, or you just want to say hi, you can email me at Suggs, S U G G S @ VetsplanationPodcast.com or visit the website at VetsplanationPodcast.com or find us on Facebook, Instagram, or TikTok at Vetsplanation. Thank you all for listening and I'll see you back here next week.