Ovine cutaneous myiasis: Effects on production and control
Introduction
At least eighty species of the dipteran families Calliphoridae (blowflies) and Sarcophagidae (fleshflies), belonging largely to the genera Lucilia, Calliphora, Chrysomya, Phormia and Sarcophaga, have been recorded as agents of myiasis (Hall and Wall, 1995). However, two species of facultative blowflies are of particular economic importance in sheep rearing areas of the world: Lucilia sericata and L. cuprina (Foster et al., 1975, Tenquist and Wright, 1976, French et al., 1992, McLeod, 1995, Snoep et al., 2002). This review will provide an overview of their effects on production, potential risk factors and control of the problems primarily caused by these two species, although brief mention will also be made of the obligate sarcophagid, Wohlfahrtia magnifica.
Section snippets
Biology of Lucilia blowflies and sheep myiasis
The species of Lucilia that facultatively parasitise sheep, deposit batches of about 200 eggs in the wool of their ovine host. After hatching from the egg, first stage larvae migrate down the wool fibres to the skin. Feeding is assisted by proteolytic enzymes, which initiate external digestion of the host's tissue and mouth hooks, which abrade the skin surface (Evans, 1936). The mature third stage larvae cease feeding and enter a dispersal phase, in which they migrate away from the lesion, drop
Wohlfahrtia magnifica
Although the focus of this review is primarily on myiasis caused by Lucilia blowflies, some mention must be made of the sarcophagid, W. magnifica, since this species may be of considerable importance in some sheep-rearing areas. It is found throughout the para-Mediterranean basin and in Eastern Europe, extending eastwards into China, including the steppe regions of continental Europe. In these high temperatures and low humidity areas, W. magnifica is usually a more abundant and more clinically
Risk factors
The incidence of ovine cutaneous myiasis by Lucilia blowflies is determined by two groups of factors: those that influence sheep susceptibility and those that affect fly abundance. However, it is often difficult to disentangle the various individual factors that act together to influence the overall pattern risk and of myiasis incidence, particularly because different risk factors affect the localisation of the myiasis on the body or the time of year when it occurs. Furthermore, the importance
Control
Since the incidence of ovine cutaneous myiasis is determined largely by two factors: the number of susceptible sheep and the number of flies available to oviposit, for control two strategies can be considered. These are reducing sheep susceptibility and reducing fly abundance to a level that significantly reduces challenge. These strategies are not necessarily mutually exclusive.
Climate change
Sheep susceptibility, fly abundance and fly activity are, as described above, all strongly influenced by weather conditions. Hence, myiasis incidence would be expected to be highly sensitive to even relatively small changes in climate. In temperate environments, the range of elevated temperatures predicted by current climate change scenarios are likely to result in longer fly activity seasons with earlier spring emergence and a higher cumulative incidence of myiasis leading ultimately, as is
Concluding remarks
Sheep farmers adopt a range of approaches to the type and timing of management used for the control of myiasis, the rational basis for which is often not well evaluated. Selection of the most appropriate management strategy, particularly in relation to insecticide application, is important, because it will help to minimise disease incidence relative to cost, while also helping to reduce the potential for insecticide resistance development. In seasonal environments, where fly abundance increases
Conflict of interest statement
The author has no conflicts of interest that may have unduly affected the views expressed in this review.
References (102)
- et al.
Control of sheep blowfly strike using fly-traps
Vet. Parasitol.
(2006) - et al.
Faecal soiling and gastrointestinal helminth infection in lambs. I
J. Parasitol.
(2007) - et al.
Field trials to confirm the efficacy of ivermectin jetting fluid for control of blow fly strike in sheep
Vet. Parasitol.
(1993) - et al.
Acquired resistance of sheep to larvae of Lucilia cuprina, assessed in vivo and in vitro
Int. J. Parasitol.
(1990) - et al.
Wound myiasis of sheep in Hungary
Vet. Parasitol.
(1997) The role of insect growth regulators in arthropod control
Parasitol. Today
(1993)- et al.
Myiasis of humans and domestic-animals
Adv. Parasitol.
(1995) Resistance and the control of sheep ectoparasites
Int. J. Parasitol.
(1995)- et al.
Retarded growth of Lucilia cuprina larvae on sheep and their sera following production of an immune response
Int. J. Parasitol.
(1992) - et al.
Cross-resistance to dicyclanil in cyromazine-resistant mutants of Drosophila melanogaster and Lucilia cuprina
Pestic. Biochem. Physiol.
(2005)