Prevent Flystrike in Sheep: How Farmers Can Strike First

Reader Contribution by John Klar
Published on April 27, 2021
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by Adobestock/Paul

Of the various adversities confronted in animal husbandry, insects and parasites can be some of the most mysterious, and destructive. Among those are a cadre of particular offenders belonging to the fly family. Technically, we are concerned here not with the “housefly” family of flies (muscidae) but with the “scourge of livestock” variety (family calliphoridae), which are a whole different kettle of fish.

Flystrike” refers to an outbreak of blowflies: those green, blue, or bronze buzzers that proliferate in summertime. Blowflies are a particular plague to commercial shepherds in Australia, but they are quite plentiful in North America, where they can cause horrible distress, including death, to livestock.

Sheep are particularly susceptible to flystrike, because of their thick wool, where not only moisture but organic matter (soil or feces) can become enmeshed, luring females from this particularly noisome family of flies to lay eggs in the matted wool. Maggots (incongruously called “gentles“) are scavengers of carrion and dung, so open wounds are also an invitation. Blowflies are famous in forensic medicine as the first arrivals when death descends — the time of death of human corpses is sometimes estimated by measuring the larval development of blowflies.

How to Identify Flystrike

Goats, horses, and other livestock can be stricken, but sheep owners must exercise special vigilance. Be alert for signs of agitation, reduced appetite, anxiety, or distress. During heavy fly seasons these behaviors are not uncommon, but in flystrike they may signal an infestation that can spread both within the animal and throughout the flock. Though used medicinally to debride dead tissue, blowfly gentles will eat living tissue, and not very gently. They often infest the tail or hind area where both moisture and fecal matter attract females to lay their eggs.

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