Preliminary Data from Six Years of Selective Anthelmintic Treatment on Five Horse Farms in France and Switzerland.

Anthelmintic resistance (AR) of small strongyle populations (cyathostomins) against products of the benzimidazole and tetrahydropyrimidine classes occurs now worldwide and there is an increasing number of reports also regarding macrocyclic lactones. Consequently, and in order to maintain an appropriate horse parasite control, alternative control schemes must be evaluated under field conditions. Here we present a six-year field study on the administration of the so-called selective or targeted selective anthelmintic treatment (SAT) concept. In this study on five horse farms in France and Switzerland, 757 fecal samples from 93 equids (90 horses, 3 ponies) have been taken twice a year (between early and late spring and between early and late autumn) from autumn 2014 to spring 2020 and processed by a McMaster technique. From a total of 757 samples, only 263 (34.7%) had a fecal egg count ≥200 EpG and needed an anthelmintic treatment. This small number of fecal samples ≥200 EpG demonstrates the considerable potential for a long-term reduction of the number of anthelmintic treatments and the anthelmintic pressure by using the SAT-programme.

Protein expression profile of Gasterophilus intestinalis larvae causing horse gastric myiasis and characterization of horse immune reaction.

BACKGROUND: Little information is available on the immunological aspect of parasitic Gasterophilus intestinalis (Diptera, Oestridae) larvae causing horse gastric myiasis. The objectives of this research were to analyze the protein content of larval crude extracts of the migrating second and third larvae (L2 and L3) of G. intestinalis in order to characterize the immune response of horses. RESULTS: The proteomic profile of L2 and L3, investigated by using one and two dimensional approaches, revealed a migration pattern specific to each larval stage. Furthermore, Western blots were performed with horse sera and with sera of Balb/c mice immunised with the larval crude extracts of L2 or L3, revealing a different immune reaction in naturally infected horses vs. artificially induced immune reaction in mice. The comparisons of the immunoblot profiles demonstrate that the stage L2 is more immunogenic than the stage L3 most likely as an effect of the highest enzymatic production of L2 while migrating through the host tissues. Fifteen proteins were identified by mass spectrometry. CONCLUSION: This work provides further information into the understanding of the interaction between G. intestinalis and their host and by contributing a novel scheme of the proteomic profile of the main larval stages.

A study on the seasonal epidemiology of Anoplocephala spp.-infection in horses and the appropriate treatment using a praziquantel gel (Droncit 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 Anoplocephala 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 Anoplocephala 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 9%, oral gel, 1 mg/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 analysis. Thereby, no Anoplocephala spp. eggs were found in the faeces of 32 horses (97%). The single horse remaining positive for Anoplocephala spp. eggs did not completely swallow the anthelmintic gel and consequently, did not receive the appropriate dose of the drug.

Odour-mediated long-range avoidance of interspecific competition by a solitary endoparasitoid: a time-saving foraging strategy.

1. In studies on optimal foraging strategies, long-range decisions in the pursuit of resource are rarely considered. This is also the case for sympatric parasitoids, which may be confronted with the decision to accept or reject host larvae that are already parasitized by a competing species. They can be expected to reject already parasitized hosts if it is likely that they will lose the resulting intrinsic competition. However, examples of such interspecific host discrimination are rare. 2. We propose that parasitoids that are not egg-limited should reject inferior hosts only if it saves them time, and that this will be achieved mainly when the parasitoids are able to detect competitors from a distance. We tested this hypothesis using the sympatric parasitoids Cotesia marginiventris (Cresson) and Campoletis sonorensis (Cameron). 3. C. sonorensis was found to be the superior intrinsic competitor but, upon contact with a host larva, both wasps readily accepted hosts that had already been parasitized by the other species. However, in an olfactometer experiment, C. marginiventris females were found to strongly avoid the odour of their superior competitor. 4. These results are in accordance with a time optimization scenario, whereby the inferior competitor accepts competition if it costs only an egg, but avoids competition if it may save time that can be allocated to the search for more profitable hosts. 5. Models on host discrimination strategies in parasitoids had not yet considered discrimination from a distance. Long-range foraging decisions can also be expected for other organisms that have to choose between resources of varying suitability and profitability.