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What is it?
- Flystrike is a horrible disease.
- In flystrike, blowflies lay eggs on the skin.
- Maggots hatch from the eggs and eat into the skin causing sores. This is a horrible sight for even the most experienced farmer.
- Of all domestic animals, sheep are most often affected, because wool particularly dirty wool attracts blowflies.
- One type of blowfly can strike even relatively clean areas on sheep.
- Blowflies can strike wet dirty areas on animals such as dogs, pet rabbits and even cats, especially if they are weak or have dirty matted hair. This is unusual.
Where does it occur?
- There are several species of blowfly that cause flystrike and they occur throughout New Zealand.
- The relatively recent aggressive Australian green blowfly has spread south through the country affecting all areas except perhaps the far south.
- Blowflies favour warm humid conditions.
Signs - what to look for
- You’ll need to be very observant to spot the early signs of eggs on the wool or skin or small sores containing maggots.
- The sores are usually under dirty wool at the sheep’s back end, in shearing cuts or on feet with footrot.
- The Australian green blowfly can strike relatively clean skin along the back or around the poll and ears.
- Sometimes the behaviour of the sheep is the first sign that it has been struck. It might seem restless, seek shade, twitch its tail, swing round to try to nibble affected areas and stamp its feet.
- When there are sores on the skin, the maggots should be removed with meths (a horrible job).
- The sore should be treated with flystrike powder containing diazinon, available from your veterinarian or rural supplier.
- In an emergency, small flystrike wounds can be treated with flyspray.
- It’s important to treat the sores when they are still small.
- Extensive and deep sores are very difficult or impossible to treat.
- In severe cases, euthanasia may be the only humane option.
- The sheep should be examined daily to make sure they don’t become struck again.
- Insect repellant on the surrounding wool will help to keep the blowflies away.
- Dirty, wet or injured skin attracts blowflies, so it’s important to remove the attraction by keeping sheep clean.
- Removing dags is important, and if the wool is long, shear the sheep to prevent wool at the back end getting wet and dirty.
- Sheep should never be carrying more than a year’s growth of wool and they must be shorn if they are.
- Cuts and sores should be treated and injured sheep kept under close observation until wounds have healed.
- Good worm control helps prevent the diarrhoea that soils the wool at the back end and helps attract blowflies.
- Blowflies favour sheltered areas so move sheep to open more exposed paddocks during high risk periods.
- Blowflies breed in dead carcases as well as on live flesh, so it is very important that all dead animals on the farm are buried or incinerated. This includes wild animal and bird carcases too.
- Flytraps can help attract blowflies away from stock. If enough flytraps are used early in the season, they help prevent flystrike.
- Flytraps can also be used to monitor the risk by indicating how many blowflies are around.
- These can either be purchased or made at home, and many veterinarians and agricultural advisors can advise on how to make home-made traps.
- Other control methods that can be effective in strike prevention include applying long-acting insecticide to the skin by dipping or using saturation sprays.
- For the lifestyle farmer it is often more practical to use long-acting pour-on or spray-on treatments.
- Read the label carefully and follow manufacturer’s instructions to the letter. Each treatment has different specifications.
- Following treatment there is a withholding time before wool can be sold.
- There are many control treatments on the market and it is important to select one suitable for your situation.
- Consult your veterinarian or other animal health professional for sound advice.
Get professional advice
- If you farm sheep and if you have any doubts about how to prevent flystrike or about how to treat it, consult your veterinarian for professional advice.