Chat Transcript: Dr. John Poe on Fly Control

If you missed EquiSearch's chat with Dr. John Poe, chief veterinarian at the Kentucky Horse Park, here's your chance to read the latest advice on fly control on your horse or in your barn.

EquiSearchStaffGreetings , we are chatting with Dr. Poe on insect issues with horses.

Dr. John Poe – There is the epidemiological triad of disease. At the top of this triangle-type host, which is the horse in this instance, at the lower left hand point, the agent is eastern or western encephalitis, and the third point of the triangle is the environment, your barn, your pasture, etc. In the center is the vector. This is real important–this triangle explains how important the vectors are in the transmission of diseases. Vector control is important–you will control a lot of diseases–a lot more than they think they will.

The vector picks up any agents, like West Nile, and he transmits it to the horse, which is the host. The vector is the most important thing to control because we can’t control the environment completely, we can’t control the viruses in this country, but you can control the vector, i.e. mosquitoes. There are different vectors. Let’s talk about mosquitoes being vectors. They spread Equine Infectious Anemia (EIA) or swamp fever. That’s the reason we do Coggins, to test for EIA, which is a viral disease spread by mosquitoes. Once a horse is infected with EIA, he does not get over it. He is chronically infected.

Dr John Poe – Here are some other examples of viral diseases spread by mosquitoes. These are called arboviral encephalitis (Eastern Equine Encephalitis, Western Equine Encephalitis, West Nile Virus–which is encephalitis–and then finally there is one called Venezuelan Equine Encephalitis, which is not in this country. If horses go to South or Central America they are vaccinated.

Dr John Poe – DEET, insects know that you are warmer, they detect, and DEET interferes with the insect’s ability to detect temperature. The reason they are coming to you instead of your door, they are attracted by heat. They sense heat and move towards it.

Dr John Poe – Back to vectors: Arthropods, which are six-legged insects like ticks–with Potomac Horse Fever, it is believed that ticks or some other arthropod transmits it. The next group is flies.

Dr John Poe – With bot flies, gastrophilius intestinalis is caused. The bot flies lay eggs on the horse’s legs and then they migrate up and hatch in the horse’s stomach. That’s the reason we worm for bots–that’s the larval form of those flies. When we worm them, we eliminate that larval stage in their stomach. When you worm in the fall you will see those pass out.

RedRedWineHorse Flies!!! Does anything help with them. My guys are suffering with these jumbo guys!

Dr John Poe – With horse flies, we’re talking about control measures.

RedRedWineYes..control..or better yet, elimination of the species totally

Dr John Poe – 1. Premise control–we’ll talk about this later. The second part of the control measure is the actual vector control of the horse.


Dr John Poe – The first thing I like are fly masks. Horse flies tend to stay away from the face and head toward the rear. They are kind of clever! There are two products I like: The first is called Permectrin II and that is made by Boehringer Ingelheim.

Dr John Poe – It is an emulsifiable animal and premise spray. You can mix it up and spray the animal and you can spray your barn and horse trailer.

Dr John Poe – This product has up to 30-day residual effect. The second product I like is Freedom Spot On.

Dr John Poe – This is an individual horse treatment that you put on the middle of the back much like the Frontline that is used on dogs and cats.


Dr John Poe – You treat your horses–the label says kills and repels hornflies, face flies, stable flies and house flies for up to two weeks–but in reality you get about 7 to 9 days.

Sallydo you think this is effective? the Frontline-like product?

EquiSearchStaffThat’s good to know

Dr John Poe – All these products are over-the-counter. The neat thing about all this, there are a lot of great products, but you have to know what to pick. That’s where your vet can help you.

Dr John Poe – Yes, Sally, it is effective for a long week.

RedRedWineIs the Freedom Spot also good for ticks?

RuffianDo you think wipe-on products last longer than sprays?

Dr John Poe – It’s actually 65 percent permephrin. Permephrins are your long-acting insecticides–days, weeks. That gives you your long duration effect. Your pyrethrins are quick knock-down, but extremely short duration. They will last a few minutes.

SallyAre these types of pest-repellents healthy — that is, are the flies in any way dangerous (i mean horseflies and deerflies) or are they just pesky?

SallyI have heard that some trainers do not spray their horses at all and let them get used to the flies so their skin isn’t so sensitive – is this a bad idea?

RedRedWinehorse flies cause my gelding to go berserk, which is dangerous to both of us!

Sally good point!

Dr John Poe – Sally, horse flies are for the most part just pesky–more of an aggravation. Flies are not as disease-causing as the mosquito. That’s why we talk about vectors, because flies are pesky but mosquitoes are disease-producing, and consequently, more important.

Dr John Poe – Freedom Spot, RedRedWine, will help repel ticks. It may not keep every tick off, but it will reduce the incidence. It will keep the numbers down.

Dr John Poe – Ruffian, there is one spray product that is pretty good. It is called Buzz Off, made by Boehringer Ingelheim again. It is pretty good–it has both a pyrethrin as well as a longer-acting insecticide. That is a good wipe-on.

RedRedWineWhere is freedom spot placed? I see ticks mostly on my horse’s tail.

EquiSearchStaffWelcome Little Ox. Dr. Poe is explaining various insects as vectors for diseases in horses and the latest products.

Dr John Poe – RedRedWine, Freedom Spot is put on the dorsal midline, along the back.

Little OxThank you. Sorry to be late.

RedRedWineMy sister in California says every time she finds a tick on herself she sends it somewhere to be checked. Should we do this periodically with ticks on the animals?

Dr John Poe – With ticks on the animals, I would say no. The main thing about ticks on us is to get them off quick. If one has bitten you and drawn blood, you might check with your health care provider, Lyme Disease being the important one there. You can get started quickly on preventative antibiotics if your health care provider thinks it wise to do.

Little OxI’m curious about automatic sprayers in barns. Are they effective?

RedRedWineThey seem to help at our barn, but them make me nervous. I hate being in the stall when they go off.

Dr John Poe – Little Ox, I’ve seen automatic sprayers for 10 years, and the people that install them say they are not effective.

Dr John Poe – Maintenance on the automatic sprayers is difficult–keeping the plumbing working correctly is always a challenge.

RedRedWine I might have missed the beginning about West Nile. What is our best strategy?

Dr John Poe – Back to flies, around here in Central Kentucky we get eosinophilic keratitis.

EquiSearchStaffWelcome Deadeye. Dr. Poe is explaining various insects as vectors for diseases in horses. Feel free to ask questions.

Dr John Poe – It is caused by face flies, which are flies laying eggs underneath the horse’s third eyelid. Consequently in Central Kentucky, we like the fly mask on everybody.

SallyI’m not familiar with that term – would you mind defining that for simpletons?

RedRedWineooh, that sounds bad. What is it?

Sallyeosinophilic keratitis -that is.

Dr John Poe – We put fly masks on in early June and leave them on until the end of September.

Dr John Poe – Fly masks really eliminate the eye problems caused by the flies, in my opinion. That is a great, great management thing.

RedRedWineGood tip!

Dr John Poe – On West Nile strategy: Getting back to control measures, number one, premise control, and number two, mosquito control on the horse. On premise control–Control standing water–no tires, pools, or puddles of water.

RedRedWineGood luck on the water control this spring…it has yet to stop raining!

Dr John Poe – Standing water is a breeding ground for mosquitoes. 2. Compost muck far away from the barn. 3. Chain-drag your fields and paddocks to break up your manure piles to cause desiccation of the manure piles. The sun dries it out. The mosquito has to have moisture to hatch.

RedRedWineAnother good tip!

RuffianStanding water being a no-no, what can you do if you have stock ponds for cattle nearby?

Dr John Poe – Back to eosinphilic keratitis: It is treated topically with steroids and antibiotics. It is quite manageable.

Dr John Poe – Ruffian, that’s a tough one.

RedRedWine Is EK a midsouth thing or is it spreading?

Dr John Poe – There are some gamubusia fish–they are called mosquito fish–they will put them in decorative pools of water around homes–they will actually eat the mosquito. Some states, Texas has some rules against it, check your state regulations before you do this.

Dr John Poe – EK is seen a lot where you have a lot of flies. In Kentucky, we have more flies than mosquitoes. We will see a little more EK than some other part of the country. We don’t spray for mosquitoes around here for the most part.

EquiSearchStaffIsn’t there some sort of disk you can put in ponds to discourage larvae?

Dr John Poe – There may be such as disk–I’m not familiar with it. You could check with an entomologist.

Little OxThat sounds great! Where would I find gamubusia fish? Any downside?

EquiSearchStaffIt’s some sort of insecticide built for water disbursement.

Dr John Poe – There’s a concentrated effort to improve livestock watering systems and eliminate farm ponds because animals will do better with potable water–water treated at municipal stations–and you eliminate breeding grounds for mosquitoes by eliminating the farm ponds.

RedRedWineDr. Poe, are you aware of any farms using the little wasps with good results?

Dr John Poe – On gambusia fish–I’m not an expert. You could check with a fish supply company, your state fish and wildlife department, or go online and do a search.

Little OxEliminating those mucky ponds certainly makes sense.

RedRedWineExcept for the ones that are also frog and bird habitats….

Little OxYep. agree with you there, RedRedWine.

Dr John Poe – Wasps do eat fly larvae–they are natural predators. I don’t know anybody using them in that way. They tend to be a little hazardous to humans!

RedRedWineReally? Little bitty fly predator wasps? I didn’t know they were hazardous to humans.

Sally am I wasting my money on the spray stuff such as Repellex? And Flysect and such? Are the ones that you suggested vastly different?

Dr John Poe – Sally, a lot of the things you buy are weak. I would stick with the things I recommended–Buzz Off, Permectrin II, and the Freedom Spot On. These are stronger products and I personally think you ought to use stronger products to be forceful in your approach to vector control.

RuffianIf automatic sprayers aren’t good, what’s the best way to have a fly-free barn?

Dr John Poe – Ruffian, that’s going back to premise control. When you attack vectors, you need a multi-pronged approach. This is a good point: Control standing water, compost muck far away from barn, chain-drag your fields or paddocks, feed pelleted feed (sweet feed with molasses attracts flies) and stall fans help in decreasing mosquitoes. You should also spray the barn with Permectrin or Buzz Off.

RuffianThat sounds like a good plan. Thank you.

cowboyHow do you control flies and insects at the Kyhorsepark

Dr John Poe – Cowboy, we use two approaches at the Horse Park–premise control and vector control on the horse. On the horse control–1. fly masks, 2. some of the horses get Freedom Spot On–that are real sensitive to insects, 3. the show horses are wiped or sprayed daily with Permectrin II.

Dr John Poe – Another thing that factors in is a proper worming schedule. Some time about November, I recommend Quest, because Quest gets microfilaria that some of the other wormers do not get.

Dr John Poe – Microfilaria are larval stages of different insects.

Dr John Poe – When we first started using Eqvalan horses started swelling five to seven days after we wormed with Eqvalan because it killed microfilaria, which had never been done before.

Dr John Poe – You’ve got premise control and horse control. It’s a two-pronged attack

RedRedWineI remember that with the first ivermectin shots.

Dr John Poe – Basically you have to attack it this way. You can’t forget the barn and just use fly sprays because that will not solve the problem.

RuffianThank you, Dr. Poe. Good advice.

Dr John Poe – That’s right, RedRedWine. Most horse swelled up in their chest and abdomen and it’s because it was killing the microfilaria that we had never killed before.

Dr John Poe – Vector control is very important in horses to control diseases. Vaccination is your second step you want to do to protect them against the arboviral diseases, which are Eastern and Western encephalitis and West Nile.

SallyThank you, Dr, Poe. I feel as though I will be able to apply all this knowledge!

RedRedWineAre you seeing that the West Nile vaccination is having an impact?

Dr John Poe – Sally, thanks for writing in. We appreciate your input.

Dr John Poe – RedRedWine, it’s one of the approaches we are taking to prevent the disease–first being vector control, second being immunization.

EquiSearchStaffDr. Poe, are you aware of how far west West Nile has gone so far?

Little OxThanks, Dr. Poe. Good chat.

EquiSearchStaffYes, looks like the hour has flown by. Thanks everyone for this very informative chat!

Dr John Poe – It is in 30-plus states. It is not to the Rocky Mountains yet. I heard someone on the news say that it might make it to the Rocky Mountains this summer.

EquiSearchStaffWow..that has sure traveled fast!

EquiSearchStaffThank you, Dr. Poe. And give Cigar a pat for me!

Dr John Poe – I appreciate everybody’s input. Anyone who would like to ask another question may email me at [email protected]. Good night!

RedRedWineThank you so much!


RedRedWine Good night

Dr John Poe – A quick update on John Henry, who is 27 and had colic surgery this spring: He’s gaining weight and spicy as ever!

EquiSearchStaffWonderful! What a guy!!!




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