Bot Flies, Bot Eggs, Bot Larvae, You and Your Horse! – Everything you need to know to avoid infestation!

Let’s talk BOTS!  

The bee-like bot fly that winds your horse up in the summer months… 

The annoying sticky nit eggs on your horses and legs! 

The sores and symptoms that your horse has become a host for the Bot!

And what to do if you have found something odd in your horse’s poo and think it could be the larvae of the bot fly!

Bots are GROSS!  but what can you do to prevent your horse becoming a host of these nasties?

What should you do if you think bot’s have already infested your horse?

Read on because we are going to tell you all you need to know!

WHAT ARE BOTS AND WHY SHOULD YOU AS A HORSE OWNER CARE?

Bots are the larvae and maggots of Bot flies and they spend most of their lives inside your horse!  

They are a pest to the horse in most of the life stages.

As flies, they are annoying, hovering around the horse’s legs, winding your horse up even more on warm and hot days.  Making him stamp his feet damaging his hooves!  But that’s not the only thing they do to annoy you and your horse!

They lay their sticky yellow eggs on your horse’s coat! Making him look dirty and they really stick!

Then as they itch the horse and he grooms himself, the larvae migrate into the horse’s lips, gums and mouth.  

This can cause sores and lesions which could lead to infection!

They then go to the horse’s stomach where they will have a detrimental effect on our horse’s health.  

Before appearing in the droppings like nasty pink aliens FREAKING you out!  Ready to pupate, hatch and start again!!!

And whilst many Bot infestations can go unnoticed in the horse.  A severe infestation will impact how the horse digests his food. Which could lead to loss of condition and performance.  

LET’S UNDERSTAND THE LIFECYCLE OF THE BOT FLY IN A HORSE IN MORE DETAIL!

The diagram above shows the lifecycle of the Botfly!  Our aim as horse owners is to break this cycle!

1 – THE BOT FLY (‘GASTEROPHILUS’)

After hatching from the pupa, the bot flies mate, and the female bot flies to find host horses.  

The female bot fly only lives around 10 days! So she will get to work within hours of mating!

Bot flies look like small bees or wasps hovering around your horse. (As per in the picture below)


What does a horse bot fly look like? Photo Credit: Thanks to Sari Maydew

2 – BOT EGGS 

The eggs laid by the bot fly are Yellow / White tiny nits less than 1mm long!

They will be on your horse’s forelegs, shoulders, neck, mane, chin, lips and throat. (most commonly on the legs).

Each female fly could lay 500 eggs! They will usually lay eggs on more than one horse!  So always check all the horses on your yard, if one has been affected chances are the others have too!


PHOTO: Bot eggs on a horse’s leg   Photo Credit: Sophie Toole

So the eggs irritate the horse and as he scratches them, they migrate to the horse’s mouth. Here they hatch and into little maggots and bury themselves in the lips, gums and between the teeth.

At this stage lookout for sores around the horse’s mouth (see image below). If your horse has a dentist appointment you may even see the maggot larvae in the mouth like in this video (warning it’s pretty gross!)

https://youtu.be/2Fata1T8zJg

After a few weeks, the larvae are ready to leave the mouth and head for the stomach.

3 – STOMACH BOTS

After the incubation period in the mouth and gums, the bot maggots make their way to the stomach and intestinal tract.

The larvae grow by attaching themselves to the stomach wall and lining.

The larvae at this stage become even scarier looking!  They are thick  and tough skinned, almost bullet shaped.  They are grub like with rings of spines and they have mouth hooks.  

They will spend the winter growing in the stomach for about 8 – 10 months, till they are a 1/2 – 3/4 inch long!

Image – Bot Larvae – Thanks to Davies Thoroughbred Services

4 – BOTS IN HORSE’S DROPPINGS

In the spring and early summer the bot larvae will leave the stomach and pass into your horse’s droppings.

They then pupate on the ground to emerge as flies in 1-2 month and the cycle starts again!

HOW CAN YOU PREVENT & TREAT BOTS IN HORSES?

Depending on which stage you are in the lifecycle determines the treatment. At certain stages there are very few signs that your horse is suffering from a bot fly infestation. You will only know if you see visible evidence, like eggs, sores or larvae.  We cannot test for bot infestation, it will not show in your horses’ faecal egg count.

So let’s start with preventing the bot flies laying eggs on your horse!

HOW TO PREVENT BOT FLIES LAYING EGGS ON YOUR HORSE

Here are some things that will help 

Remove droppings from your field regularly.

Not only will this make your paddock look pristine. (we do love tidy paddocks!)  AND help break the lifecyle of worms! 

You will be able to see if you have any larvae in droppings.  It is possible too that the heat from the composting muck heap can kill off the pupa of the bot fly! 

Protect your horse!  

Whilst many fly sprays have limited effectiveness, we still think they do help a little. 

As with all things, you need to apply quite generously!  A fly spray can’t work well if you only have a quick spritz!  

You can also use a flysheet, fly mask and fly boots which will prevent all flies landing and biting legs. 

And making sure the tail is long and not plaited! so your horse can swish the flies away! 

Having a companion, allows them to stand nose to tail and keep flies off each other’s faces. 

And finally field shelter with cobwebs to catch flies are so helpful (thank you spiders!) So don’t go brushing down the cobwebs till the end of summer!

Turn out Times.

Bot flies do not like the dark, so turnout after dark and bring your horse in during the day to a shady stable.


HOW TO REMOVE BOT FLY EGGS ON YOUR HORSE

So your horse has tiny ‘glued on’ yellow bot egg / nits on him what can you do to get them off?

Before you start to remove the bot eggs move the horse to somewhere other than his pasture!  

As if they drop to the floor to be picked up by the horse grazing will be pointless!

There are a few tools you can use.

Remove with a Bot Knife –  A bot knife is the easiest way to remove them.  It is shaped to help you gently scrape off the eggs from the horse.  You can use the round edge or the flat end to scrape.  If you don’t have a bot knife you can get one from here: https://thenosebag.shop/lincoln-bot-knife/

(p.s. They have a serrated edge which is pretty nifty at opening bales too)

Remove with a Grooming Block –  These porous fiberglass blocks,  will remove bot eggs. Simply groom over the coat to scrape the eggs away

Tips for removing bot eggs!

  • Using warm water and washing will simulate the horse licking and will make removal of eggs easier.
  • If you don’t have bot knife, a good soapy wash or your horse will remove some of the nits. You could follow up by scraping gently with a blunt dinner knife (note: use with care and caution).
  • Don’t be too aggressive at trying to remove the eggs!  You don’t want to damage your horses coat or bruise him!  
  • As part of the EFECS worming programme Clare will advise you when to worm for bots and inhibited and encysted redworm. 
  • Protect yourself! whilst it is very unlikely that the bot eggs will cause you harm, you can’t be too careful! So in the interest of hygiene and your health please keep yourself clean, wash your hands, avoid touching your face and consider wearing gloves

See this video to help you https://youtu.be/f0frwQbWfWE

HOW TO TREAT BOT SORES ON THE HORSE’S MOUTH

So if you notice that your horse has sores around his mouth like above, round with a small hole in the centre,  it is very likely that your horse has bot larvae that have burrowed into the mouth to start the lifecycle.

(gross we know 🤢)

If you notice them, some vets may advise worming with an ivermectin based wormer now (i.e. Eraquell or Eqvalan).

However, we would suggest you wait until the larvae are more active and have migrated to the stomach and worm in late December with a Moxidectin based wormer (i.e. Equest). We feel that giving a wormer too soon may not be effective and also contribute to the resistance to wormers.

With the sores, we would advise you to keep them clean to avoid infection and apply Dermagel.

Some may suggest that you try to remove the larvae, we wouldn’t advise you try to remove them!  

This could cause your horse more distress and increase the chance of infection.  It is likely that your horse has more larvae burrowed inside the mouth so wouldn’t stop the infestation.  

The best treatment is with a dewormer.

HOW TO TREAT IF YOU NOTICE BOT LARVAE IN YOUR HORSES POO!

It is a total shock to see bot larvae in droppings! Especially if there are a few of these aliens in your beloved horse’s poop!

Firstly, don’t panic and remember that it doesn’t mean you are a bad owner!  

Make sure you remove all droppings from your paddock daily.  And get them onto a muck heap there the heat should kill the larvae as it composts

Give an ivermectin based wormer now and make sure you get onto a worm count program. 

It may also be helpful to let your faecal egg count provider know you are treating for bots.  Then they can add it to your horse’s record and support you through the process.

ARE BOTS DANGEROUS FOR HORSES?

Most bot infestations do not show any symptoms and the bot itself is not life-threatening for a horse.  

However, any parasite in the stomach will have detrimental effects on your horse’s health, condition and performance.

Symptoms and Signs of Bot Infestation in Horses:

Can include:

  • Loss of condition, including a dry coat
  • Decreased appetite
  • Restlessness
  • Stomach irritation (shown by kicking/scratching at the stomach)
  • Diarrhoea
  • Constipation
  • They can also cause skin tears as they can burrow into the skin as well as being ingested.
  • Larvae in the mouth can cause inflammation, ulcers and a discharge in the sinus tracts and infection.
  • Severe infection in the intestines can affect digestion
  • Gastritis, leading to colic, can be caused by ulcers and abscesses 
  • Ulcers can cause changes in normal behaviour and temperament 
  • Peritonitis can be caused by perforation of the stomach lining

CAN HUMANS GET BOTS?

It is extremely rare for a human to become infected by horse bot fly larvae but has been known to have happened! 

Therefore, make sure you wash your hands. Avoid touching your face when treating and you may wish to wear gloves.

There are species of bot fly that do go after humans!  Lucky for us here in the UK they are native to the America’s.

ARE BOTS PASSED TO OTHER HORSES IN THE DROPPINGS?

No, a horse cannot catch bots from the larvae in the droppings it needs to hatch into a fly and lay its eggs on the horse coat!

Horses can ingest bot eggs through mutual grooming with another horse or pony. So if you have several horses on your yard, make sure you all follow a worming program.  You should all treat for bots and encysted and inhibit redworm in the winter

CONCLUSION

So there you have it all we know about Bots, how to help your horse, recognise them, treat and prevent!

We know as horse owners there is so much to learn and know, which is why having EFECS as part of your horse’s health care team can save you the stress and worry.

If you enjoyed this blog please share it with your horse-owning friends on your social media or by email.

Do you have any further questions?  

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