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Larvicidal effect of imidacloprid/moxidectin spot-on solution in dogs experimentally inoculated with Angiostrongylus vasorum Schnyder, M; Fahrion, A; Ossent, P; Kohler, L; Webster, P; Heine, J; Deplazes, P Schnyder, M; Fahrion, A; Ossent, P; Kohler, L; Webster, P; Heine, J; Deplazes, P (2009). Larvicidal effect of imidacloprid/moxidectin spot-on solution in dogs experimentally inoculated with Angiostrongylus vasorum. Veterinary Parasitology, Larvicidal effect of imidacloprid/moxidectin spot-on solution in dogs experimentally inoculated with Angiostrongylus vasorum Abstract A controlled, randomized, blinded dose confirmation study was conducted to evaluate the larvicidal efficacy and safety of imidacloprid 10 mg/kg/moxidectin 2.5 mg/kg body weight spot-on solution in dogs experimentally inoculated with 200 infective third stage larvae (L3) of Angiostrongylus vasorum. Twenty-four adult dogs were randomly allocated to three study groups of 8 dogs each. Animals in group 1 were treated 4 days post-inoculation (dpi), those in group 2 at 32 dpi, and the dogs in group 3 were left untreated. All dogs were euthanized and necropsied 56-59 dpi. In order to determine the worm burdens in the arterial lung vessels a method of reverse lung perfusion with phosphate buffered solution after inhibition of coagulation with heparin was applied. In the control group, excretion of first stage larvae (L1) of A. vasorum started 47-55 dpi and all dogs excreted L1 at least on one sample day before euthanasia (0.1-32.5 larvae per gram of faeces). A mean of 99 (SD 42.8) adult parasites were recovered in the post-mortem examinations in these eight control dogs. In contrast, no L1 at all were found in the faeces of dogs of groups 1 and 2, nor were any adult parasites detected at necropsy. Respiratory symptoms were observed in dogs of groups 2 and 3. Pathological findings in the lungs correlated with the treatment groups: in the animals of group 1, no or minimal lesions were found, while in all those of group 2 dispersed patterns of pale pink, slightly raised and consolidated foci were present in all lung lobes. In contrast, the lungs of the dogs from group 3 were severely affected: large confluent areas were hardened, raised and discoloured, with frequent haemorrhagic patches. Pneumonia, thrombi and parasites were histologically confirmed. The lung lymph nodes were regularly enlarged. Hence, imidacloprid/moxidectin spot-on effectively eliminated fourth stage larvae (L4) and immature adult A. vasorum in experimentally infected dogs and prevented patent infections. The earlier an infected dog was treated, the less severe were the pathological lesions observed in the lungs. Twenty-four adult dogs were randomly allocated to three study groups of 8 dogs each. Animals in group 1 were treated 4 days post inoculation (dpi), those in group 2 at 32 dpi, and the dogs in group 3 were left untreated. All dogs were euthanized and necropsied 56-59 dpi. In order to determine the worm burdens in the arterial lung vessels a method of reverse lung perfusion with...

Dixenous helminths that depend on rodent intermediate hosts are supposed to be negatively affected by urbanization due to lower supply of rodents in urbanized environments. Prevalence rates of dixenous, non-strictly monoxenous, and monoxenous helminths in 228 red foxes (Vulpes vulpes) along a gradient of increasing urbanization were assessed by morphological parasite identification in the city of Geneva, Switzerland. Multivariate analyses for the five most prevalent helminth species or genera revealed a significant decrease of prevalence rates for the dixenous helminths Echinococcus multilocularis and Taenia spp. from the rural (52.1 and 54.3%, respectively) to the urban area (30.0 and 20.0%, respectively), but not for the monoxenous nematode Uncinaria stenocephala (overall prevalence of 78.2%) and the non-strictly monoxenous nematode Toxocara canis (overall prevalence of 44.3%). The lower prevalence of Toxascaris leonina in the urban area (8.0%) compared to the rural area (59.6%) raises the question of whether rodent paratenic hosts play a major role for the population dynamics of this species.

A suspected case of multiple anthelmintic resistance on a farm in the canton of Zurich, Switzerland, into which South African Boer goats had previously been imported, was confirmed in a controlled test. Twenty sheep were allocated into one control group and three treatment groups to determine the efficacy of mebendazole, ivermectin and moxidectin applying the faecal egg count reduction test (FECRT). The sheep were slaughtered 1 week later and post-mortem worm counts were performed. Benzimidazole and ivermectin resistance were found in Haemonchus contortus with an efficacy of 55 and 61%, respectively. Moxidectin appeared to be effective when the data was analysed according to the recommended analytical techniques with an efficacy of 96%. This is the first description of resistance of gastrointestinal nematodes to one of the macrocyclic lactones in small ruminants in Switzerland. The results are discussed in relation to the importance of controlling livestock before importation.

The aim of the study was to investigate the longitudinal changes of exsheathment of ovine and bovine 3rd-stage strongylid larvae in an artificial rumen (RUSITEC) and to compare the results with in vivo data obtained from rumen-fistulated sheep. Infective larvae were incubated in nylon mesh bags in the sheep rumen or the RUSITEC apparatus for periods of 1, 6 and 12 h, respectively. The 12 h exsheathment rates in the rumen and the RUSITEC apparatus (in parentheses) were as follows: Haemonchus contortus: 100% (100%), Ostertagia circumcincta: 100% (76%), O. leptospicularis: 100%. (100%), O. ostertagi: 53% (59%), Trichostrongylus axei: 100% (100%), T. colubriformis: 37% (36%), Cooperia curticei: 94% (76%), C. oncophora: 95% (89%), Nematodirusfilicollis: 0% (N.D.), N. spathiger: 11% (15%), N. battus: 7% (5%), Oesophagostomum venulosum: 17% (9%), Chabertia ovina: 7% (2%), Dictyocaulusfilaria: 1% (N.D.). Larvae of Nematodirus spp. and T. colubriformis showed a quick rise of the exsheathment rate 2 h after transfer into the abomasum. These results confirm that exsheathment generally occurs in the part of the gastrointestinal tract immediately anterior to the habitat of the adult parasite. The overall similar course of exsheathment in both systems indicates that the essential stimuli for exsheathment were generated and maintained under in vitro conditions of the artificial rumen. In both systems, the bicarbonate concentration and the pH reflected a similar status of the H2CO3/HC-3 buffer system, which is known to provide the essential stimuli for larval exsheathment of the abomasal species. These results give evidence that the RUSITEC system represents a valid system for studying the kinetics of exsheathment of strongylid nematodes under in vitro conditions. For 7 of the species investigated the obtained results represent the first data on larval exsheathment in vivo and in vitro.