Veli Yilgor Cirak

Standardization of the egg hatch test for the detection of benzimidazole resistance in parasitic nematodes.

The ability to reliably detect anthelmintic resistance is a crucial part of resistance management. If data between countries are to be compared, the same test should give the same results in each laboratory. As the egg hatch test for benzimidazole resistance is used for both research and surveys, the ability of different laboratories to obtain similar results was studied through testing of known isolates of cyathostomins, Haemonchus contortus, Ostertagia ostertagi, and Cooperia oncophora in programs supported by the EU (Cost B16 and FP6-PARASOL). Initial results showed difficulties in obtaining reproducible and similar data within and between laboratories. A series of ring tests, i.e., simultaneous and coordinated rounds of testing of nematode isolates in different laboratories was subsequently performed. By adopting identical protocols, especially the use of deionized water and making dilutions of thiabendazole in dimethyl sulfoxide in the final ring test, laboratories correctly identified both susceptible and resistant isolates. The protocols for the test and preparation of solutions of thiabendazole are described.

Helminth parasites found in hedgehogs (Erinaceus concolor) from Turkey

Hedgehog diseases are becoming important issues for veterinary surgeons due to growing interest in this animal species among pet owners and an increase in cases of rescued hedgehogs requiring veterinary care. A parasitological study was carried out on hedgehogs (Erinaceus concolor) in the Bursa province of Turkey, found dead mainly due to road casualties, to determine their helminth parasite burden. The detected helminths and their prevalences were as follows: Physaloptera clausa (72.2%), Crenosoma striatum (55.5%), Aonchotheca erinacei (55.5%), Hymenolepis erinacei (55.5%), Nephridiorhynchus major (50%) and Eucoleus aerophilus (22.2%). The number of parasites in infected animals varied from 1 to 203. The highest mean intensity of infection was observed with C. striatum, and the lowest was observed with N. major. The mean abundance of different species varied from 0.7 to 41.8, where E. aerophilus and C. striatum had the lowest and highest abundance, respectively. This study represents the first time N. major and E. aerophilus have been reported in hedgehogs in Turkey. The presence of E. aerophilus and its potential role as a zoonotic agent are discussed.

Helminth infections of wild boars (Sus scrofa) in the Bursa province of Turkey

The present study aimed to investigate the status of helminth infections in wild boars in the Bursa province of Turkey. For this purpose, during 2007-2008, 27 wild boars were necropsied and examined for helminths. Individual samples of tongue and diaphragm from 27 necropsied wild boars and an additional 22 tongue and diaphragm samples provided by hunters were examined by trichinoscopy and artificial digestion for Trichinella spp. larvae. Twenty animals (74%) were identified as being infected with at least one helminth species. Twelve species of helminths were detected, with the following prevalence rates: Metastrongylus apri (59%), Metastrongylus salmi (52%), Metastrongylus pudendotectus (52%), Dicrocoelium dendriticum (33%), Globocephalus urosubulatus (22%), Macracanthorhynchus hirudinaceus (19%), Gongylonema pulchrum (11%), Physocephalus sexalatus (7%), Trichuris suis (7%), Ascarops strongylina (4%), Hyostrongylus rubidus (4%) and Taenia hydatigena larvae (4%). Generally, lungworms were the predominant helminths. The highest mean abundance was observed for M. pudendotectus, and the lowest was determined for T. hydatigena larvae. Significant differences in the prevalence and intensity were found for D. dendriticum with respect to host age and sex, respectively. The mean intensity of M. pudendotectus was significantly influenced by the sex and age of the wild boars. This study is the first report describing the presence of M. salmi, M. pudendotectus, D. dendriticum, G. urosubulatus, M. hirudinaceus, P. sexalatus, A. strongylina and H. rubidus in wild boars in Turkey. All analysed muscle samples were negative for Trichinella spp. larvae.

Comparative plasma disposition, bioavailability and efficacy of ivermectin following oral and pour-on administrations in horses.

Pour-on formulations of endectocides decrease the risk of injury for both user and animal, and are particularly convenient for animal owners who can apply the product. This study was designed to investigate the plasma disposition and efficacy of ivermectin (IVM) following pour-on, per os and intravenous administrations. Eighteen female horses weighing 510-610 kg were used in this study. The animals were allocated into three groups (per os, pour-on and intravenous groups). The equine paste, bovine pour-on and bovine injectable formulations of IVM were administered orally, topically and intravenously at the dose rates of 0.2, 0.5 and 0.2mg/kg bodyweight, respectively. Heparinized blood samples and hair samples were collected at various times between 1h and 40 days. The samples were analysed by high performance liquid chromatography with fluorescence detector. Faecal strongyle egg counts (EPG) were performed by a modified McMasters technique before and at weekly intervals during 10 weeks after treatment. The results indicated that the plasma concentration and systemic availability of IVM was lower but the plasma persistence was prolonged after pour-on administration compared with per os route. IVM (paste) reduced the EPG by >95% for 10 weeks, whereas the reduction in pour-on group varied from 82 to 97%. EPG reduction in pour-on group was lower than that of per os group. Degradation on the application site, cutaneous biotransformation, binding of IVM to the haircoat and/or sebum are probably responsible for the relatively lower bioavailability of IVM in horses after pour-on administration. In conclusion, the poor plasma availability observed after pour-on administration could result in subtherapeutic plasma concentrations, which may promote the development of drug resistance in parasites.

Investigations on the seasonal patterns of strongyle infections in grazing lambs, and the occurrence of anthelmintic resistance on sheep and goat farms in western Anatolia, Turkey

The seasonal patterns of strongyle infections in untreated, weaned lambs were determined on four governmental farms during a grazing season. In three farms, the infection level (predominantly Teladorsagia spp. and Trichostrongylus spp.) measured by egg counts or worm burdens remained low throughout the study; higher egg counts mainly caused by Haemonchus contortus were transiently recorded on the fourth farm. Significant body weight gains were observed in all groups, but they varied between farms irrespective of the level of strongyle infections, suggesting that the economic effectiveness of anthelmintic treatments of weaned lambs is doubtful under the extensive grazing conditions and the hot, dry climate in the region. In the second part of the study, faecal egg count reduction tests were performed for albendazole, thiabendazole, tetramisole and ivermectin on 12 sheep and goat farms to provide first information on anthelmintic resistance in trichostrongyles of small ruminants in Turkey. There was no hint of benzimidazole resistance, and unequivocal evidence of ivermectin resistance was missing. In contrast, tetramisole resistance was detected on one sheep farm.

Pharmacological assessment of netobimin as a potential anthelmintic for use in horses: Plasma disposition, faecal excretion and efficacy

This study aimed to determine the plasma disposition and faecal excretion of netobimin (NTB) and its respective metabolites as well as the efficacy against strongyles in horses following oral administration. Netobimin (10mg/kg) was administered orally to 8 horses. Blood and faecal samples were collected from 1 to 120h post-treatment and analysed by high performance liquid chromatography (HPLC). Using a chiral phase-based HPLC, plasma disposition of ABZSO enantiomers produced was also determined. Faecal strongyle egg counts (EPG) were performed by a modified McMasters technique before and after the treatment. Neither NTB nor ABZ were present and only albendazole sulphoxide (ABZSO) and sulphone metabolites (ABZSO(2)) were detected in the plasma samples. Maximum plasma concentration of ABZSO (0.53+/-0.14microg/ml) and ABZSO(2) (0.36+/-0.09microg/ml) were observed at (t(max)) 10.50 and 19.50h, respectively following administration of NTB. The area under the curve (AUC) of the two metabolites was similar to each other. Netobimin was not detected, and ABZ was predominant in faecal samples. The maximum plasma concentration (C(max)) of (-)ABZSO was significantly higher than (+)ABZSO, but the area under the curves (AUCs) of the enantiomer were not significantly different each other in plasma samples. The enantiomers of ABZSO were close to racemate in the faecal samples analyzed. Netobimin reduced the EPG by 100%, 100%, 77%, 80% and 75% 2, 4, 6, 8 and 10 weeks post-treatment, respectively. The specific behaviour of the two enantiomers probably reflects different enantioselectivity of the enzymatic systems of the liver which are responsible for sulphoxidation and sulphonation of ABZ. Considering the pharmacokinetic and efficacy parameters NTB could be used as an anthelmintic in horses.

The effects of different ages and dosages on the plasma disposition and hair concentration profile of ivermectin following pour-on administration in goats.

The effects of different ages and dosages on the plasma disposition and hair concentration profile of ivermectin following pour-on administration in goats. J. vet. Pharmacol. Therap.34, 70-75. The effects of different ages and dosages on the plasma disposition and hair degradation of ivermectin (IVM) were investigated following pour-on administration in goats. Twenty-eight female Saanen goats allocated into two groups of 14 animals according to their ages as young (5-6 months old) and old (12-24 months old) groups. Each age group was divided into two further of seven goats and administered pour-on formulation of IVM topically at the in recommended dosage rate of 0.5 mg/kg bodyweight The recommended cattle dosages rate of 0.5 mg/kg or at the higher dosage of 1.0 mg/kg. Blood samples were collected at various times between 1 h and 40 days. In addition, hair samples (>0.01 g) were collected using tweezers from the application sites and far from application sites of the all animals throughout the blood sampling period. The plasma and hair samples were analyzed by high performance liquid chromatography (HPLC) using fluorescence detection following solid and liquid phase extractions, respectively. Dose- and age-dependent plasma disposition of IVM were observed in goats after pour-on administration. In addition, relatively high concentration and slow degradation of IVM in hair samples collected from the application site and far from the application site were observed in the present study. The differences between young and old goats are probably related to differences in body condition and/or lengths of haircoat. The systemic availability of IVM following pour-on administration is relatively much lower than after oral and subcutaneous administrations but the plasma persistence was prolonged. Although, the longer persistence of IVM on hairs on the application site may prolong of efficacy against ectoparasites, the poor plasma availability could result in subtherapeutic plasma concentrations, which may confer the risk of resistance development in for internal parasites after pour-on administration in goats.

Plasma dispositions and concentrations of ivermectin in eggs following treatment of laying hens

AIMS: To determine the plasma disposition and concentrations of ivermectin (IVM) in eggs produced by laying hens following S/C, oral and I/V administration. METHODS: Twenty-four laying hens, aged 37 weeks and weighing 1.73 (SD 0.12) kg were allocated to three groups of eight birds. The injectable formulation of IVM was administered either orally, S/C, or I/V, at a dose of 0.2 mg/kg liveweight, following dilution (1:5, v/v) with propylene glycol. Heparinised blood samples were collected at various times between 0.25 hours and 20 days after drug administration. Eggs produced by hens were also collected daily throughout the study period. Samples of plasma and homogenised egg were analysed using HPLC. RESULTS: Maximum concentrations of IVM in plasma and mean residence time of IVM were lower after oral (10.2 (SD 7.2) ng/mL and 0.38 (SD 0.14) days, respectively) than after S/C (82.9 (SD 12.4) ng/mL and 1.05 (SD 0.24) days, respectively) administration (p<0.01). The time to maximum concentration and elimination half-life were shorter following oral (0.14 (SD 0.04) and 0.23 (SD 0.11) days, respectively) than S/C (0.25 (SD 0.00) and 1.45 (SD 0.45) days, respectively) administration (p<0.01). IVM was first detected in eggs 2 days after treatment in all groups and was detected until 8 days after oral and I/V administration, and until 15 days after S/C administration. Peak concentrations of IVM were 15.7, 23.3 and 1.9 µg/kg, observed 2, 5 and 4 days after I/V, S/C and oral administration, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: The low plasma bioavailability of IVM observed after oral administration in laying hens could result in lower efficacy or subtherapeutic plasma concentrations, which may promote the development of parasitic drug resistance. Due to high IVM residues in eggs compared to the maximum residue limits for other food-producing animal species, a withdrawal period should be necessary for eggs after IVM treatment in laying hens.