Vet's vision with Phil Rennie Tauranga Vets

Already this summer period we’re seeing cases of fly infestations on livestock, and at times even our companion animals. The main culprit is the Australian blow fly, Chrysomya megacephala, which lays eggs that develop quickly into larvae and constitute the majority of maggots found in damaged skin and underlying tissue.

Areas commonly affected by flystrike are around the tail, on the backline, on the flanks of the belly and around the pizzle in males.

They can also be found at the pole, between the ears of rams from fighting, and between the toes following footrot.

Shearing is helpful to deter infestation for a few weeks, though shearing cuts and other wounds will attract flies.

Affected animals may nibble their wool, stamp their feet and twitch their tails prior to becoming depressed and succumbing to the infection. Dark patches may also be seen on white fleece. Maggots can be difficult to see, so wool should be parted and checked.

Prevention and treatment of flyblown stock should be done in a timely manner. In the case of sheep six weeks post-shearing is ideal for uptake of chemical.

Insect Growth Regulators such as Cyrex generally give up to 12 weeks’ protection when applied properly and are safe to use. IGRs act on maggot stages so adult flies will die out naturally in a few weeks. Cyrex also kills maggots quickly, with the dual combination of active ingredients stopping the active feeding of maggots within minutes of contact and dead maggots moving off wounds within hours. Cyrex is available in 250ml bottles, which must be diluted at a ratio of 10ml concentrate to 5L water.

Treatment of flyblown animals should also involve clipping of wool from around the affected area close to the skin and disposing of the clippings. Where clipping or shedding of wooled areas over the back occurs, the exposed skin is prone to sunburn and may become inflamed and infected. Protection of this skin should be with a zinc-based product such as the antibacterial containing cream Filta Bac.