Résultat de la recherche
Light and electron microscopy studies of the midgut and salivary glands of second and third instars of the horse stomach bot, Gasterophilus intestinalis
A morphological study of the midgut and salivary glands of second and third instars of Gasterophilus intestinalis (De Geer) (Diptera: Oestridae) was conducted by light, scanning and transmission electron microscopy. The midgut is anteriorly delimited by a proventriculus, without caeca, and is composed of posterior foregut and anterior midgut tissue from which a double-layered peritrophic matrix is produced. The midgut can be divided into anterior, median and posterior regions on the basis of the structural and physiological variations of the columnar cells which occur along its length. Two other types of cell were identified: regenerative cells scattered throughout the columnar cells, and, more rarely, endocrine cells of two structural types (closed and open). Different secretion mechanisms (merocrine, apocrine and microapocrine) occur along the midgut epithelium. Abundant microorganisms are observed in the endoperitrophic space of the anterior midgut. The origin and nature of these microorganisms remain unknown. No structural differences are observed between the second and third instar midguts. The salivary glands of G. intestinalis second and third instars consist of a pair of elongated tubular structures connected to efferent ducts which unite to form a single deferent duct linked dorsally to the pharynx. Several intermediate cells, without cuticle, make the junction with the salivary gland epithelium layer. Cytological characteristics of the gland epithelial cells demonstrate high cellular activity and some structural variations are noticed between the two larval stages.
A study on the seasonal epidemiology of Anoplocephala spp.-infection in horses and the appropriate treatment using a praziquantel gel (Droncit (R) 9% oral gel)
In a study on the seasonal dynamics of the gastro-intestinal nematode egg production in horses, one breeding farm also revealed a particularly high prevalence of Anoplocephola spp. infection. Consequently, this farm was chosen for analysing the seasonal pattern of the tapeworm egg excretion over a one year period in order to establish the most favourable periods for an appropriate and successful cestocidal treatment. The seasonal analysis showed a significantly higher (p < 0,05) Anoplocephala spp. egg excretion between July and October, i.e. during the second part of the grazing period. This result clearly underlines the importance of a cestocidal treatment during that period of the year Subsequently, horses of this farm and of a second farm with a high prevalence of Anoplocephola spp. were used to evaluate the efficacy of praziquantel in a specific oral gel formulation for horses under field conditions. The efficacy of praziquantel was tested in a total of 33 horses from the two farms harbouring a coproscopically detected Anoplocephala spp. infection prior to treatment. Praziquantel (Droncit (R) 9%, oral gel, 1mg/kg bodyweight) was administered to the horses according to their body weight. The efficacy of the drug was evaluated ten days after treatment by a double faecal ana lysis. Thereby, no Anoplocepholo spp. eggs were found. in the faeces of 32 horses (97%). The single horse remaining positive for Anoplocephola spp. eggs did not completely swallow the anthelmintic gel and consequently, did not receive the appropriate dose of the drug.