HELMINTHOLOGIA ,40,1:-xx, 2003 The effect of Stalosan F on selected poultry parasites T. W. SCHOU, A. PERMIN Section for Parasitology, Department of Veterinary Microbiology, The Royal Veterinary and Agricultural University Stigbøjlen 4, DK-1870 Frederiksberg C, E-mail: ape@kvl.dk Summary Production losses are significantly higher in free-range table egg production systems compared to conventional intensive indoor production systems. No methodical analysis of the cause of the higher morbidity and mortality is available at present. However, investigations have shown that infe-tions with intestinal roundworms such as Ascaridia galli , Heterakis gallinarum and Capillaria obsignata are more prevalent in free-range production systems. These infections might cause production losses in the range of 10-20% due to impaired feed conversion, reduced growth and egg production, and increased mortality. The potentially high level of disease in the organic production of broilers and eggs for consumption, together with anthelmintic regulations in force, show a marked need for alternative methods of parasite control in organic poultry production. The aim of this study was to examine whether Stalosan F could be an alternative or supplement in the control of selected endoparasites in poultry. Three experiments were conducted to examine the effect of Stalosan F on A. galli, H. gallinarum and C. obsignata eggs under in vitro and in vivo conditions. In short, the results suggest that Stalosan F does have a sublethal effect on these parasite eggs. Under laboratory conditions eggs treated with Stalosan F showed less ability to develop into infective stages and establish in subsequently experimentally infected chickens. Under field conditions, an area heavily contaminated with A. galli, H. gallinarum and C. obsignata eggs, was divided into two pens. One pen was treated with Stalosan F after which tracer animals were inserted into both pens. Tracer animals from the Stalosan F treated pen, were found to harbour significantly fewer adult worms than the chickens from the untreated pen. However, no differences were found between the two groups in the total number of worms (larvae and adults) recovered. It therefore seems that the development from larvae to adult worm was arrested by the use of Stalosan F. This could be of importance to the epidemiology of the worms, since it would decrease the reproduction rate of the worms hereby reducing the number of parasite eggs in the pen. Based on these results it seems that regular use of Stalosan F in free-range poultry production systems may reduce the infectivity of A. galli, H. gallinarum and C. obsignata eggs. Key words: Stalosan F; Ascaridia galli; Heterakis gallinarum; Capillaria obsignata; in vivo; in vitro ; infectivity
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