Press Release: Flies have “struck” and we already have cases of flystrike in sheep in the Waikato!
This is a productivity and a welfare concern. The good news is that flies like conditions that make the grass grow! So the fact that it is warm and wet means there is plenty of food for our animals along with the flies!
Who can get flystrike? In our agricultural livestock sheep are the most commonly affected animal and the flies (blowflies) lay eggs on moist wool or open wounds. The eggs hatch out and the resulting maggots “strike” the animal by eating into their skin (ugh!). However, flystrike can be seen in any animal that has an open wound or skin lesion and we see it in pets (long-haired dogs and rabbits) and also in dairy cows with skin cancer lesions.
We have 3 main types of blowfly that cause strike in sheep: Lucilia sericata (common green blowfly), Lucilia cuprina (australian green blowfly) and Calliphora stygia (brown blowfly). They have pretty names for such horrible flies! Humans can also get myaisis and it is commonly seen in the tropics: Human Botfly and the Tumbu fly are well-known offenders. People who have suffered from this disease describe the pain and irritation that results from the maggots digesting their flesh. This is exactly how the sheep behaves and affected animals can be spotted stamping their feet, getting up and lying down, turning to look at the struck area and running away from themselves.
The maggots release digestive enzymes into the skin, so the flesh breaks down and healing is difficult to achieve. Affected animals suffer constantly and lose weight, they will die due to weight loss and secondary bacterial infection.
What can we do about it? We can keep our animals clean (free from dags) and short wooled (shearing) which helps. We can also treat them with insecticides. These may be systemic (chemical is in the animal) like organophosphates, or topical (chemical is in the wool/skin). There are various different chemicals which may kill flies and maggots. Resistance is a problem, so judicious use is important. Beef and lamb has a great resource on flystrike if you would like to read more:
https://bit.ly/BeefandLamb-Flystrike and ask your veterinarian for advice about prevention, they will be happy to help.