How the Bot Fly Causes Warbles in Rabbits

A Guide to Bot Fly Symptoms, Removal and Treatment

Bot fly symptoms in rabbits show up after the Cuterebra fly deposits an egg on the skin of the rabbit. It is one of the rabbit facts you should know about as you begin raising rabbits on your farm or homestead. Also known as the condition warbles in rabbits, it is self-limiting, and usually not fatal. However, the symptoms of warbles in rabbits can be both alarming and rather disgusting.

How Warbles in Rabbits Occurs

Flies are a nuisance and common to any area with livestock, manure, and moisture. Bot flies are different than regular run-of-the-mill flies. The Cuterebra fly is a large insect, somewhat resembling a large bumble bee. It doesn’t take many Cuterebra to cause a problem in your rabbits. The bot fly lays a single egg, either on the rabbit or on the vegetation near where the rabbits hang out. Either the egg hatches and the bot fly larvae burrow into the skin of the rabbit, or the eggs are picked up on the fur of the rabbit as it grazes by a plant or something else. The larvae hatch and make their way under the skin of the host rabbit, grow and mature. The larvae stage feeds on secretions from the host. Pretty unpleasant, right? The rabbits don’t seem to be bothered by the growing larvae although some mild scratching at the site might be noticed. Our rabbits continued with normal eating and activity.  The first thing I noticed was a large cyst type growth on the back of one rabbit.

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Our Journey with Warbles in Rabbits

I was familiar with the bot fly and the yellow sticky eggs as they are a concern with other livestock. However, I did not think about this as the cause of the large lump growing on my older male rabbit. Mistakenly, I assumed the poor old boy had some sort of tumor and would be leaving us shortly.

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I kept a close watch to see if he was suffering, acting sick, not eating, but none of those things occurred. Quincy continued to eat normally, play with his hutch mate, Gizmo and do normal rabbit activity. I am not against taking a rabbit to the veterinarian, but Quincy was not acting sick! I thought there was a possibility that the abnormal growth was a benign cyst and not a malignant tumor. I never thought about the possibility of a bot fly larvae growing beneath the skin. Soon, I noticed that the “growth” had gotten considerably smaller. I examined the lump and found it to be oozing fluid and pus. After cleaning the area and cleaning the wound it was clear that whatever it was had burst and was draining. I had been taking photos all along to show to a veterinarian if I needed to take the rabbit to the vet’s office. I remembered a friend who had been raising rabbits for many years. I showed her the photos and she suggested that I look up warbles in rabbits. The symptoms of what I had been observing were exactly the same. We even had the distinctive round hole, where the larvae had crawled from the host rabbit. Yuck! Things continued to get even more disgusting! Warbles in rabbits are not for the faint of heart!

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This is what the area looked like after the larvae emerged. The hole is hidden by the fur.

I did a lot of research and spoke to our veterinarian. He confirmed what I suspected and agreed with my treatment plan for warbles in rabbits, which I will explain in a moment. I checked the other rabbits in the rabbit area. Gizmo had a few smaller lumps on him, actually, he had five lumps but it was too soon to be sure they were warbles. Quincy had one other smaller warble. With my vet in agreement, I was to let the infestation run its course from this point. He could have done the extractions surgically in his office but we opted to carefully monitor both rabbits and perform twice daily wound care. The holes are actually fairly easy to clean and treat if you can stand to do it yourself. I have a fairly high tolerance for grossness so I opted to do it myself. Treating the wounds is similar to treating a deep tissue wound or puncture wound. Keeping it clean and dry is key.

Why Does This Happen?

While sanitation and cleanliness are important when raising any livestock, fly issues can still occur. Even in the best of rabbit care, situations can occur that make us question our methods and care taking ability. Conditions of extreme wetness at just the right time can give the Cuterebra fly the right situation to lay her egg. Although we cleaned the hutches regularly, added dry bedding, removed spilled food and cleaned water bowls, we still had to deal with this bot fly attack.

The larvae burrow into the skin of the host rabbit and it takes a while before you notice the growth developing. By this point, many bot flies may have laid their eggs on the rabbit or other rabbits in the area. Although cleanliness is important, the fact that you end up with warbles in rabbits does not necessarily mean that you don’t do a good job of keeping the rabbit area clean.

Bot Fly Symptoms – Cuterebra Fly Attack

The bot fly deposits one egg on the skin of the rabbit. The larvae mature under the skin of the rabbit, creating a large, hard mass that looks like a tumor or cyst. When you examine the lump you may notice a hole that the larvae is breathing through or it may simply be a soft crusty area on the skin. The rabbit seems to not be bothered by the examination or by hosting the creepy crawly larvae.

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Bot Fly Removal

This part is very important to understand. Removal of the larvae causing warbles in rabbits should be performed by a veterinarian. If you squeeze and accidentally squish the larvae it releases a deadly toxin which can send the rabbit into shock and result in death. The larvae can be difficult to remove and require quite a bit of pulling, all the while trying to not squish it. It’s best to leave that to the veterinary professional. As our rabbit’s bots were about to emerge, the skin around the breathing hole would thin out, and get crusty. At this point, I was extremely careful to check twice a day, so I could immediately begin wound treatment and ward off further infection. Cleaning the area soon after the larvae exited, made all the difference in the time it took for the hole to heal up and close over.

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The site soon before the larvae crawls out. The skin thins out and reddens or appears scabbed over

Even though I was vigilant, I never actually saw the bot larvae emerge.

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Treatment of Warbles in Rabbits

The hole left behind when the larvae emerges requires twice daily care for the first week. If the wound was healing well, I then went to once daily wound care. Take care to keep the area clean and sanitary during the healing so you don’t attract more flies. House flies will be attracted to the fluids oozing from the wound and you don’t want to end up with a case of maggots or fly strike in rabbits on top of warbles in rabbits.

The products I use to treat the wound from warbles in rabbits are commonly available.

Clean the area. Trim away any fur that is in the way, or that may get stuck on the drainage.

The wound should not bleed or only bleed a little.

1. Flush the wound inside the hole with a sterile saline solution.  I flush, then mop up the fluids, then flush again.  I try to flush out as much debris as possible to aid in healing.

2. I use a product called Vetericyn, that is sold in many pet supply or farm supply stores. I spray this into the hole and around the outside of the wound.

3. Last, I squeeze a good bit of triple antibiotic cream into the hole. (CAUTION: DO NOT use a triple antibiotic cream with pain reliever included)  

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Warbles in rabbits is self-limiting, meaning it should clear up without major infection or complication. If the wounds are not healing and progressively getting worse, it is best to seek the advice and care of a veterinarian. If you feel at all uncomfortable or ill-equipped to perform the wound care it is best done by a veterinarian. Everyone’s comfort level in dealing with wounds and illness is different. You and your veterinarian are the ones to make this decision.

What Other Animals Can be Victims of Bot Fly?

Each species of livestock acquires a bot infestation in different ways. In livestock, the bot fly often lays its egg on the grazing area and is eaten or inhaled by the animal. Sheep are susceptible to nasal bots. In cattle, the large bot flies spook the cattle causing them to interrupt their grazing. The fly lays eggs on the cow’s lower legs. Larvae enter the body, migrate through, and many weeks later emerge on the back through holes they make in the skin. Bot flies in cattle are an economic problem. The meat surrounding the bot or warble is discolored and not used. The holes left in the hide make it poor quality.

Horses experience bot fly eggs deposited on the lower leg also. When you see these, a tool known as a bot comb can help remove the sticky eggs. Horses ingest the eggs, when they lick or bite the eggs off their feet and legs.  Other forms of bot flies lay the eggs on horse’s nose or throat. The eggs hatch in the horse’s mouth and burrow into the gums and tongue. The next place they migrate to is the stomach where they hang out for many months. After almost a year the bot is released from the stomach and exits in the manure. That’s almost a year of this parasite living and damaging the horse’s stomach lining.

Cats, dogs, rodents, and other wildlife often contract the bot fly larvae by brushing by the egg after it is laid. While there are cases of bot fly infecting humans the cases seem to be in underdeveloped countries.

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Clearly the bot fly is an economic issue for livestock and a health nuisance at the very least. Have you battled with bot flies infesting your rabbits or other livestock? How did you take care of the problem?

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Comments
  • Great information, but you really should have taken the bunny to the vet as soon as you saw that mass growing on it’s back. Bunny’s are prey animals that won’t show the pain that it’s in until it’s practically near death, so when you can visibly see somthing wrong with it, it’s our responsibility as pet owners to get them the help they need right away.

    Reply
  • Both of our pet rabbits suffered a bot fly warble each. We had let them outside soon after a rain in the warmer Spring months because we felt bad about them having been kept inside all winter long. This is when they were most likely infested. We only noticed the wound on the male after the larva exited the warble, so we just cleaned the wound with hydrogen peroxide and colloidal silver and it healed well. The female’s warble was on her side and very prominent. We saw the larva moving inside the warble and became very upset. When our veterinarian told us what it was, we researched bot fly strike on the internet, and learned the correct term for our rabbits’ malady was “cuterebra”. I mention that because one gets much better search results if one uses that word.

    To cause the larva to exit the warble prematurely, we held the rabbit in our lap and petted her while repeatedly applying petroleum jelly to the air hole. We would watch as the larva worked its way through the pile of jelly already applied and begin breathing again, then immediately top up the jelly to again smother the thing. Within two hours, the (very large) larva had worked its way all the way out of the warble and fell down the rabbit’s side. We snatched it up and put it into a plastic bag for the veterinarian’s reference, then cleaned the wound first with soap and water to remove the petroleum jelly, then with hydrogen peroxide and colloidal silver. The wound was healing well, but during the visit with the veterinarian, the rabbit apparently panicked, leapt, suffered a broken back and died. We think she was PTSD about having the wound cleaned.

    Lesson learned is to smother the larva out of the warble as soon as a breathing hole appears, then clean the wound gently and as thoroughly as possible, then allow the rabbit to take it from there (while protecting it from further parasites or infection).

    Reply
    • My situation is not quite so easy. I have befriended a wild rabbit. She is living outside my home for going on three years. She sleeps, eats, and spends most of her time close to us; however, we have never touched her. She even comes when called when the mood suits her and she will sleep in front of us. She has developed a warbler on her neck. I can get within one foot of her but I do not think she would allow me to clean her open wound. Is there antiseptic I could spray into the open hole once the son-of-a-gun pops out? I might be able to do that. I need advise. I love my Bunny Parker and hate to think of her suffering with an infection.

      Reply

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