What To Do If Your Sheep Get Fly Strike

St. Croix hair sheep

St. Croix hair sheep

In Hawaii, we can keep tropical hair sheep such as Barbados black belly or St. Croix varieties. Hair sheep don’t make the traditional wool that needs to get sheared off each spring. Still the conditions on the windward (wet) side of the Big Island, aren’t exactly perfect for keeping hair sheep, especially when the conditions are hot and wet.

During these times, sheep are susceptible to fly strike or myiatic flies. A parasite that can kill a sheep in as little as three days and spread to other animals in the flock or cows, and goats.




I have been keeping sheep for 10 years in the tropics and have had fly strike maybe six-eight times. My sheep flock has been as big as 30 but now I have reduced it to only five. Over the years, I have gotten fly strike on sheep, goats and recently a new born calf.

When it’s raining daily, it’s hot out and the ground you are walking on becomes soggy and it is not easily drained away, the conditions are right. Now (October) is the time to be on the look out for fly strike in your herd. Most likely you will notice a clear sign when one of your sheep is off on its own, away from the flock. Perhaps it is ostracized or just goes off on its own in its misery. But sure enough, when you approach the animal, you will see large flies buzzing around it. Your day has now changed.

The flies tend to gang up on a single spot. Perhaps there is a wound on the animal or some manure on its coat. Sheep with long dirty “dreadlocks” or matted hair with feces are a prime target. The flies, seemingly work like a pack, and bury themselves into the thick hair of the sheep. There they will lay their eggs, which are capable of hatching within six to eight hours. If you are inspecting your sheep, the eggs will be slightly off-white, almost yellow. They clump together and are somewhat wet and sticky.

Once these eggs hatch, they will feed on the skin of the animal and subcutaneous tissue (beneath the skin). Circular patches of gray, writhing worms just beneath the hair and out of sight to the observer. As they grow, the hair will start to fall out or be lifted off the animal but still remain and act as a cover to the devastation underneath. The sheep may use its mouth to bite at the maggots and will often tear some of their fur off which has already become loosened by the feeding worms. The smell and red skin will attract even more flies.


Minor fly strike on these two sheep. The one in the forefront has it the worst.

Round up your flock and inspect each one for fly damage. Check their rumps and along their spine up to their necks. Remember, time is of the essence–it takes hours not days for flies to infest a sheep. First, choose the ones with discolored, patches on their rumps, especially if the hair looks like it is wet from the animal chewing there.

Newly infested sheep will stay with the herd until they are unable to keep up or the others abandon them. Separate their hair with your fingers and look inside their fur for maggots and inspect for gobs of newly laid eggs. Use a pair of scissors to cut away hair on any patches found.

You can use manual sheep shears to cut away the hair or any cheap, but sharp, hair-cutting shears. Longer, bladed kitchen-type shears are not the best choice because they are unwieldy and often you can mistakenly cut the tender skin when pulling the hair up off the sheep to clip it. Clip the hair as close to the skin as possible removing maggots and eggs in the process. Bag the removed hair and debris in a zip lock bag. Afterwards, place the bag in the sun to kill the worms.

Once you have discovered each patch of infestation and have cut the hair down, take a hose with a spray nozzle and remove the remaining worms with a consistent and systematic burst of water. I have used Dr. Bronner’s Lavender or Pepperment liquid soap to wash the animal. Use dog flea & tick soap if you have it on hand. You may have to move the sheep to several spots while washing her to keep the fallen maggots from climbing back on her and you. Rinse her off again with a consistent spray of water. If she is severely injured use your best judgement when handling her.

Sprayed with Wound Kote

Sprayed with Wound Kote

She will immediately feel better and you will see her perk up when she no longer has worms chewing and biting her. Dry her off and apply spray iodine or Wound-Kote antiseptic spray (found at farm supply stores) on her wounds. You can also spray, insecticidal products such as Bronco fly spray on her uninjured areas. You also can use various herbal fly sprays instead of Bronco found at your local supply store. Tamanu or Kamani Oil will also keep the flies off.

If her injuries are severe, best case scenario is to put her in a screened-in enclosure for a few days to keep the flies off of her. Since she is marked she will still be targeted by the flies. If her wounds are minor, the fly sprays will work at keeping the flies off but keep her and other injured sheep in a pen for observance. It is also extremely important to have shelter from the rain. She will need to stay dry until she is healed and the flies are gone.

You can inject her with 4 ml of penicillin (both the medical supplies and medicine sold at animal feed stores) if her injuries are very severe. I always include some injectable vitamin B with the penicillin to help with the stress. Do this daily until she improves. This type of shot is intramuscular (in the muscle). You can inject her at the rump (if you don’t plan on eating her eventually) or on the neck being careful not to hit bone. Always check for a vein or artery by pulling slightly back on the plunger for blood before the injection. If you see blood, pull out and redo. Check out this link, it’s for goats but it will work for sheep called Goat Injections.

In addition, use Ivermectin Sheep Drench that will kill any remaining larvae within 12 hours. Ivermectin will kill internal and external parasites. The amount given will be on the bottle according to weight but should be anywhere between 6ml and 8ml.

Give her some warm water with some molasses and crystal electrolytes added (found at animal supply stores). If she doesn’t eat for a few days, she may pass.

My big animal vet told me the acronym for sheep is SSS (Sheep Seldom Survive). You may try your hardest but you may not succeed in saving a heavily infested sheep. I have mostly succeeded in saving my fly stricken sheep, though I just recently lost one. If you are not up for the medical procedures, ask around to other people who have sheep, they may be able to help or call your big animal vet. Most likely, you will still be the one washing and clipping off the worms.

If you have given your sheep antibiotics and Ivermectin, don’t plan on eating her until she is well and all the medicine is out of her system. If she happens to die, you may want to bury her. It’s your choice if you want to cull her and butcher her instead of treat her. I personally, have never eaten an animal in such a poor condition and have no experience in doing so.

Here are some suggestions for preventing fly strike:

  • Always have a shelter for your sheep to stay out of the rain
  • Clip any tags or dread locks off your sheep
  • Wash any sheep who has a poopy butt (might try deworming them if this is happening)
  • Separate infected animals from the herd
  • Treat any injuries and watch for fly strike on injured sheep
  • Keep supplies on hand: Ivermectin Sheep Drench, penicillin, electrolytes, vitamin B, iodine, Wound-Kote, syringes & needles, alcohol, scissors, fly spray


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