Fly strike in sheep

This article is about the flystrike in sheep.

Parasitic relationship between sheep and flies

Flies are an external parasite that, when combined with warm and humid conditions, infect sheep. Sheep Flies form a parasitic relationship with sheep, by which the fly maggots use the sheep's flesh as a habitat as well as a source of nutrients; the fly benefits from the relationship while the sheep does not. In some cases flies can be fatal to sheep. The three most common species of fly which infect sheep in Australia are Lucilia sericata, Lucilia caesar, and Calliphora vomitoria. Sheep display symptoms such as agitation, odour and matted fur, all which further encourage the attraction of flies. In order to infect the sheep, flies lay eggs on the sheep’s wool, hatching after approximately eight hours, depending on the conditions. The maggots, once hatched, bury themselves in the sheep’s wool and eventually under the sheep’s skin, feeding off their flesh. Once the larvae develop, flies continue to deposit eggs on to new or already infected sheep, starting the infection process over again. Flies are a pest in Australian agriculture, not only causing loss or degradation of stock but also requiring both money and time for effective management. A completely effective prevention strategy has not yet been produced however it is likely that this may occur in the foreseeable future.

Identification of infected sheep

In warmer periods, specifically summer, it is recommended that sheep mobs be checked every two days (Fahy et al., 2011). Flystruck sheep can be identified in the mob through characteristic green patches in the sheep's fleece, usually around the bottom area or at the site of an open wound, where wool might create a damper area which is more attractive to flies. In male sheep the penile region is also common area for flystrike to occur. When the mob settled, infected sheep will display signs of irritaion such as stamping their feet or turning to nibble their body. Area of flystrike will have a strong odour and in severe cases, sheep's wool might begin to shed.

Treatment

If a struck sheep is identified, the animal must then be removed from the mob. All wool in and around roughly a 1 cm or larger radius of the discoloured area will need to be clipped. The area is then dressed with registered chemicals, which kill the maggots. Sometimes more than one application is necessary depending on the chemical type and infection severity. The clippings must be collected after removal in a maggot-proof bag and left closed in the sun to ensure that no other animal is infected. A list of registered chemicals for treatment of flystrike can be found on state government websites and purchased at your local farm centre. (Besier et all, 2013)

Prevention

There are several preventative measures which can be taken to reduce the occurrence of flystrike in sheep mobs, these include:

None of these measures however will completely stop the occurrence of fly in sheep, and regular treatment will still be necessary. (Novartis Animal Health, 2013)

Works Cited

Besier, B., Evans, D., Feuvre, A., James, P., & Levot, G. (2013). Dressing Flystike Wounds. Retrieved 10 2013, from Sheep CRC:

Fahy, L., Lauber, M., & Suter, R. (2011). Flystrike. Retrieved 10 2013, from Department of Environment and Primary Industries:

Novartis Animal Health. (2013). Blowfly- the problem. Retrieved 10 2013, from Novartis:

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