Friday 3 June 2022

When flies strike

As we approach summer and with it warmer, more humid, weather, the risk of flystrike, or blowfly strike, increases. This is a nasty  condition and if gone unnoticed can be catastrophic for affected sheep. Most sheep keepers will apply a preventative spray-on medication at this time of the year which might have to be repeated later in the summer. It works well but is not a guaranteed defence.

One thing I look out for in terms of timing is the sighting of green bottle and blue bottle flies which appear when the temperatures are consistently above 15 degrees centigrade. These are the culprits which lay their eggs in the fleece of sheep (goats and even chickens can also succumb) and when they hatch the maggots start eating into the flesh of the animal. The process is very quick with maggots appearing within three days of eggs being laid. Vigilance is needed and because flystrike develops so quickly I investigate any suspicions straightaway.  

Sheep are very adept at hiding illness which is probably an evolved defence against predation. But subtle changes in behaviour can be considered suspect: not coming for feed; being  detached from the flock; a head down posture. There could be many reasons for these signs but nevertheless it is always worth taking a closer look. If caught soon enough flystrike can be treated successfully. Badly affected sheep have a urine-like smell  and their fleece feels damp. At this stage their survival chances are much diminished.

Our flock of twenty or so ewes and lambs are having their annual summer sojourn at a nearby farmer's field, taking advantage of some fresh grazing. I call by twice a day and give some supplementary feed. They don't really need it but it is an effective way of seeing them all close up and checking for flystrike.

Our two rams stay at home. A week or so ago the older ram was slow to come for some feed and then started to keep his distance. This was the trigger to get a closer look. He is not easy to round up but I managed with a shepherds crook hooked around his horns. On close inspection there was indeed some flystrike around the base of his horns and tiny maggots, by the look of them recently hatched, were beginning to feast and on once side the skin had been broken.  I rubbed off all the maggots I could see and a generous application of Crovect (one of the recommended medications) was sprayed round the base of the horns. If there are maggots still in the flesh Crovect will cause them to rise to the surface. More rubbing off of maggots. Salt water was used to flush over the affected area and an anti-bacterial spray applied to where the skin looked raw.  

Our breed of sheep, Wiltshire Horns, are generally less vulnerable to flystrike because of their short fleece but they are not immune. The horn area, especially in mature rams, provides a very close atmosphere around the base and close to their cheeks which is the likely reason why our ram was affected. Luckily it was caught quickly and it was possible to treat him successfully.

Abraham our older ram. Note how close
his horns are to his cheeks, creating the
potential conditions for flystrike.

Barnabas, our younger ram. His horns are
much more widely spaced allowing air to
flow more freely around the face.

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