The Blowfly Strike Problem of Sheep in New South Wales

Abstract

A field survey was undertaken between 1972-76 to reappraise the nature of the blowfly problem in New South Wales. For 2 years, 1972-1974, some 80,000 sheep were kept under observation and 12,481 strikes were reported, most due to Lucilia cuprina. Breech strike was still the basic problem but tail strike associated with scouring had become an important component where pastures have been improved. Breech strike was controlled at minimal cost by managerial practices such as docking tails the correct length--second joint-space palpable ventrally (midway down the vulval orifice in ewes) for radically mulesed lambs and the third joint-space (tip of vulva in ewes) for all other lambs-mulesing at lamb marking, mid-season crutching, determining the cause of scouring and applying the appropriate preventative or remedial measures. Thus the use of insecticides could be reserved for the control of body strike in young sheep in the odd wet years and poll strike in horned rams. Major outbreaks of body strike occurred in 1973/74. Body strike worried graziers most because of its unpredictability, sudden onset and scale. and only failing insecticides were available for control.

Sex Determination Mechanisms in the Calliphoridae (Blow Flies)

“…Here, we review sex-determining mechanisms in calliphorids (blow flies), with a focus on the Australian sheep blow fly (Lucilia cuprina) , the New World screwworm (Cochliomyia hominivorax) and C. rufifacies . L. cuprina and C. hominivorax are major pests of livestock [Watts et al, 1979;Alexander, 2006], and C. rufifacies is of importance in the field of forensic entomology [Roy and Siddons, 1939;Wilton, 1954;Baumgartner, 1993] and is a secondary agricultural pest [Baumgartner, 1993; melanogaster and the blow flies L. cuprina and C. rufifacies . In female D. melanogaster , high doses of X signal elements (XSE) activate Sxl , which both autoregulates its expression and switches tra RNA splicing into the female mode.…”

The mode of action of intra-dermal sodium lauryl sulfate (SLS) as a chemical alternative to mulesing in sheep

“…14 The breech region of sheep is predominantly affected by flystrike; however body strike is considered the main life-threatening form of myiasis caused by Lucilia blowflies. 15,16 Breech strike consists of two types: 1) crutch strike which extends from the tail base to the border of the udder or scrotum or 2) tail strike which involves the sides and stump of the tail. 17 Body strikes generally incorporates the back, flank and withers (or shoulders).…”

“…have shown a reduction in the incidence of breech strike by 81% to 100 %. 15,57 Mulesing results in a net benefit of AUD $100 -130 million per annum from reduction in production losses and sheep mortality. 65 Apart from the prevention of breech flystrike, mulesing confers additional benefits of minimising the requirement for stressful handling procedures such as removal of stained wool or dags (breech wool that is contaminated with faeces), dipping and crutching, and enables simpler shearing.…”

“…30,31 Breech strikes however can occur during dry periods of low fly abundance irrespective of weather conditions and are associated with diarrhoea caused by high worm burden as a result of grazing improved pastures and high stocking rates. 10,15,36 Strike incidence can also increase independently of weather following sheep husbandry procedures which create wounds such as crutching, mulesing or tail docking. 27 In major sheep areas of south-eastern Australia, there is a long winter period of low fly abundance as L. cuprina larvae enter a state of arrested development in the soil ('over-wintering') and are subjected to high mortality rates of over 90%.…”

“…41 Ironically, tails which were docked too short can predispose sheep to tail strike and to a lesser extent breech strike 40 due to the loss of ability for directing faeces outward and thus increasing the probability of soiling attractive to blowflies. 15 The incidence of blowfly strike is highly dependent on the weather and is likely to occur during periods of warmth and high humidity after rainfall 42 in combination with increases in the rate of pasture growth and in the density and activity of gravid L. cuprina. 27 In addition, wet weather increases the incidence of body strike associated with moist fleece and the development of fleece rot and/or bacterial dermatitis.…”