The Veterinary Record, January 8, 2005 THE fleshfly, Wohlfahrtia magnifica (Diptera: Sarco- phagidae), is an important cause of traumatic myiasis of live- stock throughout the Mediterranean basin and eastwards into China, including the steppe regions of continental Europe (Hall and Farkas 2000). Female flies are attracted to wounds or natural body orifices of their hosts, where they lay maggots. Sheep, particularly rams, are a major host, but other animals including poultry and wildlife can be affected, as well as human beings (Hall and Farkas 2000, Farkas and others 2001). After being laid, the maggots immediately start to feed on the underlying tissues, causing wounds which become attractive to gravid females of W magnifica (Hall and others 1995); more flies arrive and deposit their larvae, which enlarge the wound still further. Wohlfahrtiosis is a serious animal welfare problem, causing acute pain and suffering. The undamaged genitalia of healthy animals are a major site of infestations (Farkas and others 1997) that can lead to significant reproductive problems. In some cases the infes- tations, if left untreated, can lead to death within a few days. Several therapeutic and prophylactic schemes for treating wohlfahrtiosis have been proposed, involving topical treat- ment with insecticides, the removal of larvae, or both (Ishimbekov and Zhanuzakov 1983a, b, Kostov and others 1986, Hadani and others 1989). Most of the commonly applied insecticides, organophosphates and pyrethroids, will kill the larvae of W magnifica, but they do not provide long- term protection from infestation or reinfestation, which would facilitate wound healing. Instead, the animals must be inspected and the insecticides must be applied frequently, resulting in stress to the animals, extra costs in time and labour and a loss of grazing time. The need for frequent inspections and treatments has been identified as a major fac- tor contributing to the economic impact of wohlfahrtiosis (Farkas and Hall 1998). Some of the macrocyclic lactone endectocides, such as ivermectin and moxidectin, which ideally could provide medium-term protection against the infestation, are not generally effective against the larvae of W magnifica in naturally infested sheep either as a prophy- lactic or as a curative treatment (Ruiz-Martinez 1995, Farkas and others 1996). More recent studies indicate that doramectin could provide up to 21 days’ protection (Sotiraki and others 2003). However, it is clear that there is a need for new insecticidal compounds to control wohlfahrtiosis effec- tively. Dicyclanil belongs to the class of pyrimidinamines which have an insect growth regulatory activity (Tomlin 1997); they act on the chitin metabolism of the insect and interrupt the moulting process. Dicyclanil has a high specific activity against dipteran species, the first larval instar being significantly more susceptible to the com- pound than the second and third instars (Graf 1993). This mode of action implies that dicyclanil would be best used as a prophylactic and, so far, studies have shown that it pro- vides long-term residual protection against blowfly strike by Lucilia species in sheep (Bowen and others 1999, Schmid and others 1999, Lonsdale and others 2000, Nottingham and others 2001). Furthermore, dicyclanil prevented the development of screw-worm (Cochliomyia hominovorax) on castration wounds of calves for up to 25 days (Anziani and others 1998). The objective of this trial was to determine the efficacy of dicyclanil against natural infestation by W magnifica larvae, when it was administered to sheep topically as a spray-on for- mulation (CLIK; Novartis) under field conditions. MATERIALS AND METHODS Location of trial and flock details The trial took place in Crete, Greece, where wohlfahrtiosis became an animal health problem in 1999. Outbreaks of the disease have now spread throughout the main livestock- producing regions of the island (Sotiraki and others 2002), and there is evidence of increased fly populations, especially in the mountainous areas where their animal hosts are mainly concentrated. The trial was carried out on 160 animals from two flocks (two groups of 40 in each flock). The animals of one group in each flock were treated with dicyclanil and those of the other group were left untreated as controls. The flocks were located in Rethymnon (one of four prefectures of Crete), where the highest incidence of wohlfahrtiosis in Crete was recorded from 1999 to 2001. Flock 1 had 400 sheep at Malaki village, at an altitude of 450 m, where in 2001 95 per cent of the flocks had experienced wohlfahrtiosis and approximately 15 per cent of the animals in each flock had been infested. Flock 2 had 320 sheep at Karines village, at 650 m, where in 2001 70 per cent of the flocks had experienced wohlfahrtiosis and approximately 12 per cent of the animals in each flock had been infected. The management system in both flocks was semi-inten- sive, with a milking parlour with automatic milking facilities for 48 animals. The animals were milked in the morning and evening throughout the milking period from November to August, and stayed outside on the pasture for at least eight hours per day throughout the trial. The animals were housed overnight in the flock facilities under normal conditions, and the normal flock management routines were carried out dur- ing the trial. Papers & Articles Veterinary Record (2005) 156, 37-40 S. Sotiraki, DVM, PhD, A. Stefanakis, DVM, PhD, Veterinary Research Institute, NAGREF, Ionia 57008, Thessaloniki, Greece M. J. R. Hall, PhD, Department of Entomology, Natural History Museum, Cromwell Road, London SW7 5BD J. F. Graf, PhD, Novartis Animal Health, CH-4002 Basel, Switzerland Field trial of the efficacy of dicyclanil for the prevention of wohlfahrtiosis of sheep S. Sotiraki, A. Stefanakis, M. J. R. Hall, J. F. Graf Two groups of 40 ewes from each of two flocks were used in a field trial of the efficacy of dicyclanil to protect them against a natural infestation by Wohlfahrtia magnifica larvae, when administered topically as a spray-on formulation. The animals of one group in each flock were treated with dicyclanil and those of the other group were left untreated as controls. The trial lasted 31 weeks and the animals were inspected daily for wohlfahrtiosis. The incidences of wohlfahrtiosis ranged from 17·5 per cent to 20 per cent in the control groups and from 2·5 per cent to 5 per cent in the treated groups, and 77·8 per cent of the infestations were in the genitalia. When compared with the control groups, dicyclanil achieved a 100 per cent reduction of infestation in the treated groups of both flocks for at least 24 weeks, and an 80 per cent reduction for 31 weeks.