Waimarino has worst year for fly strike in five years

Ruapehu Bulletin, Volume 13, Issue 622, 6 February 1996, Page 4

Waimarino has worst year for fly strike in five years

Waimarino sheep farm ers are having to deal with the worst year of fly strike in five years. At worst a fly-struck sheep will die and veterinary surgeon David Seifert says he knows of several cases where farmers have lost over 100 lambs this year. Dipping and shearing prevent fly strike and in a normal season sheep will only have to be dipped once. However this year many

sheep are being dipped, twice, and because of the threat of fly strike farmers inay elect to second-shear their sheep if the weather in autumn is warm. Dr Seifert said the fly is so bad this summer because the early heat in spring sped up the life cycle of the fly which means they were able to breed more quickly, resulting in a larger than normal population of flies. Fly strike occurs when the eggs of blow flies which hatch into maggots, or maggots themselves, are found on the skin or wool of a sheep. The maggots digest the skin and flesh of the sheep and the resulting wound, which is typically large and weepy, attracts other blow flies. The presence of dags, faeces on the wool or a wound attracts the blow fly, although the Australian green fly will strike without prevarication. The timing of shearing and correctly dipping sheep are crucial factors in preventing fly strike, says Dr Seifert. Farmers will be choosing to shear when wool quality is at its highest. However, shearing just prior to the start of a significant fly strike will minimise the chances of a strike. This time will vary from one property to another depending on micro-climates.

Fly eggs thrive in humidity and as shearing dries out the skin of a sheep any eggs that are present are desiccated. Shearing usually gives a sheep six week's protection against fly strike, but this year sheep are being struck within six weeks of being shorn. Dr Seifert said that at this point farmers are dipping their sheep again but the lack of wool for the dip residue to cling to means the protection time offered by the dip is reduced. Technical Dr Seifert says the mos( technical operation a farmer carries out in animal health is dipping, and he says "there are lots of things that can go wrong." For example it is very important that the sump in a shower dip is emptied once the farmer has dipped one sheep for every two litres of sump volume. This is to ensure that the solution is clean. "If the farmer puts on a dip that is contaminated with urine or faeces then the farmer is making the sheep more attractive to flies." Dr Seifert estimates that the combined effects of loss of production and the increased cost of animal health will result in many farms facing a 5 per cent drop in gross income from sheep, with some facing a drop as much as 1 0 per cent.