RESUMO
Gastrointestinal nematodes resistant to anthelmintics have been reported in several regions of Brazil, and they may be associated with economic losses for the cattle industry. This study aimed to evaluate the resistance status of gastrointestinal nematodes from naturally infected beef cattle to several commercially available anthelmintics, as well as to test the efficacy of combinations of anthelmintics against multi-resistant gastrointestinal nematodes. Ten farms located in Rio Grande do Sul state were selected by: farmers' consent; extensive raising system; availability of calves aged from 7 to 9 months naturally infected by gastrointestinal nematodes; absence of anthelmintic treatment for 60 days before the study; and presence of 70-100 calves or more of both genders with ≥ 200 eggs per gram of feces (EPG) (sensitivity of 50 EPG). These calves were distributed into 10 groups (of 7-10 animals) per farm and treated with ivermectin, doramectin, eprinomectin, fenbendazole, closantel, nitroxynil, disophenol, levamisole, albendazole, or moxidectin. Feces were collected 2 days before treatment and 14 days after treatment. Additional groups of 7-10 calves were used to test six different two-drug combinations at four of the studied farms. In general terms, fenbendazole was the most effective drug, followed by levamisole, disophenol, and moxidectin. However, parasite resistance to multiple drugs was found in all herds, especially in the genera Cooperia spp., Trichostrongylus spp., and Haemonchus spp.. Some of the two-drug combinations were effective against nematode populations identified as resistant to the same compounds when used as single drugs. The most effective combinations were moxidectin + levamisole, doramectin + fenbendazole, and levamisole + closantel. In this study, parasites resistant to the main commercially available anthelmintics were found in all herds, and some combinations of two active components belonging to different chemical groups were effective against multi-drug resistant gastrointestinal nematodes.
Assuntos
Antinematódeos/uso terapêutico , Doenças dos Bovinos/parasitologia , Enteropatias Parasitárias/veterinária , Intestinos/parasitologia , Nematoides/efeitos dos fármacos , Infecções por Nematoides/veterinária , Carne Vermelha/parasitologia , Albendazol/uso terapêutico , Animais , Animais Domésticos , Brasil , Bovinos , Doenças dos Bovinos/tratamento farmacológico , Resistência a Múltiplos Medicamentos , Quimioterapia Combinada , Fezes/parasitologia , Fenbendazol/uso terapêutico , Haemonchus/efeitos dos fármacos , Enteropatias Parasitárias/tratamento farmacológico , Enteropatias Parasitárias/parasitologia , Ivermectina/análogos & derivados , Ivermectina/uso terapêutico , Levamisol/uso terapêutico , Macrolídeos/uso terapêutico , Nematoides/classificação , Nematoides/isolamento & purificação , Infecções por Nematoides/tratamento farmacológico , Infecções por Nematoides/parasitologia , Contagem de Ovos de Parasitas , Salicilanilidas/uso terapêuticoRESUMO
An anthelmintic efficacy trial was conducted in sheep harbouring anthelmintic-resistant worms in Argentina. Seventy lambs were selected from a flock that had been grazed on pastures infected with trichostrongyles previously shown to be resistant to the main anthelmintic groups. Lambs were allocated to comparable groups of ten animals each and treated with trichlorphon (50 mg/kg body weight (b.w.) orally); naphthalophos (50 mg/kg b.w. orally); ivermectin (0.2 mg/kg b.w. subcutaneously); fenbendazole (5 mg/kg b.w. orally); levamisole (8 mg/kg b.w. subcutaneously) and closantel (10 mg/kg b.w. orally). There was also an untreated group. The dose selection was based on manufacturer's recommendations.Faecal samples were collected 0 and 10 days post treatment to estimate efficacy (faecal egg count reduction). Six animals from each group were necropsied at day 10 for enumeration/identification of worms from the abomasum, small and large intestines to determine the absolute efficacy of each agent (controlled efficacy test). Trichlorphon and naphthalophos were effective (> 99 %) against Haemonchus contortus (p < 0.05).Naphthalophos also showed efficacy against Trichostrongylus axei (99.3 %), Teladorsagia circumcincta (97.8 %), Trichostrongylus colubriformis (99.2 %), Cooperia punctata/curticei/pectinata (90.4 %), Nematodirus spathiger (89.2 %) and Oesophagostomum venulosum/columbianum (93.7 %). Fenbendazole and levamisole showed efficacy (> 95 %) against all nematodes except T. colubriformis. The efficacy of ivermectin was low against H. contortus (23 %) and Cooperia spp. (46.3 %). Closantel showed low efficacy against T. axei (64.4 %), H. contortus (80.6 %) and T. colubriformis (59.5 %).When anthelmintic resistance is widespread, trichlorphon treatment is appropriate if H. contortus is present; however, naphthalophos represents an effective therapeutic alternative for incorporation into worm control programmes.
Assuntos
Antinematódeos/uso terapêutico , Nematoides/efeitos dos fármacos , Infecções por Nematoides/veterinária , Compostos Organofosforados/uso terapêutico , Doenças dos Ovinos/tratamento farmacológico , Ovinos/parasitologia , Triclorfon/uso terapêutico , Animais , Argentina , Avaliação de Medicamentos , Resistência a Múltiplos Medicamentos , Fezes/parasitologia , Fenbendazol/uso terapêutico , Ivermectina/uso terapêutico , Levamisol/uso terapêutico , Masculino , Nematoides/patogenicidade , Infecções por Nematoides/tratamento farmacológico , Contagem de Ovos de Parasitas/veterinária , Salicilanilidas/uso terapêutico , Doenças dos Ovinos/parasitologiaRESUMO
In the winter of 2008, cattle on a farm in the province of Neuquen, Argentina died from subacute and chronic liver fluke disease despite four previous treatments with Triclabendazole (TCBZ). In the spring of 2009, a preliminary efficacy test revealed good performance using nitroxynil, whereas TCBZ efficacy was only 18% by egg counts of Fasciola eggs in the faeces. Resistance to Fasciola hepatica to TCBZ has never been reported in South America, so in January of 2010 a controlled trial was conducted to confirm and to define the degree of resistance in this herd. In a clinical trial, the fluke egg output was monitored on Days 14 and 21 and serum enzymes gamma-glutamyl transpeptidase (GGT) and glutamic-oxaloacetic transaminase (GOT) on Days 0 and 21 in 36 calves treated with TCBZ or with closantel. The results showed a reduction of 100% in fluke egg output at Days 14 and 21 for closantel. The mean epg in the TCBZ-treated groups did not decrease. Because of the fact that in this study TCBZ treatment in cattle had no effect, even at double the recommended dose, it is highly indicative that resistance of F. hepatica against TCBZ is present on this farm. The GGT and GOT levels decreased in the closantel-treated group as a result of the treatment at 21 days after dosing. To evaluate the importance of TCBZ resistance in F. hepatica in Argentina, a study on more farms from endemic areas is needed.
Assuntos
Anti-Helmínticos/farmacologia , Benzimidazóis/farmacologia , Doenças dos Bovinos/parasitologia , Fasciola hepatica/crescimento & desenvolvimento , Fasciolíase/veterinária , Hepatopatias/veterinária , Salicilanilidas/farmacologia , Animais , Anti-Helmínticos/uso terapêutico , Argentina , Aspartato Aminotransferases/sangue , Benzimidazóis/uso terapêutico , Bovinos , Doenças dos Bovinos/tratamento farmacológico , Doenças dos Bovinos/enzimologia , Resistência a Medicamentos , Fasciolíase/tratamento farmacológico , Fasciolíase/enzimologia , Fasciolíase/parasitologia , Fezes/parasitologia , Hepatopatias/tratamento farmacológico , Hepatopatias/enzimologia , Hepatopatias/parasitologia , Contagem de Ovos de Parasitas/veterinária , Salicilanilidas/uso terapêutico , Triclabendazol , gama-Glutamiltransferase/sangueRESUMO
The objective of this study was to determine the level of resistance of Haemonchus contortus and Trichostrongylus colubriformis in sheep to levamisole, albendazole, ivermectin, moxidectin, closantel and trichlorfon. The parasites were isolated from sheep naturally infected by gastrointestinal nematodes and were then kept in monospecifically-infected lambs for production of infective larvae (L3) of both species. Forty-two lambs, at three months of age, were simultaneously artificially infected with 4000 L3 of H. contortus and 4000 L3 of T. colubriformis. The animals were allocated into seven groups with six animals each that received one of the following treatments: Group 1--control, no treatment; Group 2--moxidectin (0.2mg/kg body weight (BW)); Group 3--closantel (10mg/kg BW); Group 4--trichlorfon (100mg/kg BW); Group 5--levamisole phosphate (4.7 mg/kg BW); Group 6--albendazole (5.0mg/kg BW); and Group 7--ivermectin (0.2mg/kg BW). Nematode fecal egg counts (FEC) were carried out on the day of treatment and again at 3, 7, 10 and 14 days post-treatment. On the same occasions, composite fecal cultures were prepared for each group for production of L3, which were identified into genus. The animals were sacrificed for worm counts at 14 days after treatment. The efficacy of each treatment was calculated from the arithmetic mean of the FEC or worm burden of the treated group, compared with the values of the control group. Only trichlorfon and moxidectin treatments resulted in a significant reduction of H. contortus recorded at necropsy (73% and 45% respectively). Moxidectin reduced T. colubriformis worm burdens by 82% and albendazole by 19%. All other anthelmintics resulted in no significant reduction in the numbers of worms found at necropsy. In conclusion, the isolates of H. contortus and T. colubriformis showed multiple resistance to all groups of anthelmintics tested. This is the first report, based on the controlled efficacy test, to show resistance of T. colubriformis to macrocyclic lactones in Brazil.
Assuntos
Anti-Helmínticos/farmacologia , Resistência a Múltiplos Medicamentos , Haemonchus/efeitos dos fármacos , Doenças dos Ovinos/tratamento farmacológico , Trichostrongylus/efeitos dos fármacos , Animais , Anti-Helmínticos/uso terapêutico , Brasil , Fezes/parasitologia , Hemoncose/tratamento farmacológico , Hemoncose/parasitologia , Hemoncose/veterinária , Ivermectina/farmacologia , Ivermectina/uso terapêutico , Levamisol/farmacologia , Levamisol/uso terapêutico , Contagem de Ovos de Parasitas , Salicilanilidas/farmacologia , Salicilanilidas/uso terapêutico , Ovinos , Doenças dos Ovinos/parasitologia , Carneiro Doméstico , Resultado do Tratamento , Tricostrongilose/tratamento farmacológico , Tricostrongilose/parasitologia , Tricostrongilose/veterináriaRESUMO
The efficacy of 5-chloro-2-methylthio-6-(1-napthyloxy)-1H-benzimidazole was evaluated with three commercial fasciolicides in terms of the percentage of egg reduction in cattle. Fifty Swiss cows were selected for inclusion in the trial based on finding eggs of Fasciola hepatica in their feces. On day 0, they were blocked in five groups (G) of ten animals each according to fecal egg counts. G1 received compound alpha at 12 mg/kg p.o.; G2 triclabendazole at 12 mg/kg p.o.; G3.closantel at 3.5 mg/kg s.c.; G4 clorsulon at 2.0 mg/kg s.c. G5 animals served as untreated controls. Fecal analysis was performed on days 0, 7, 14, 21, 28, 60 and 90. Efficacy was measured on days 14 and 21. In addition, the extension and intensity effects were determined on day 60. The percentage efficacy for groups 1-4 was 98.1, 98.7, 98.2 and 97.9 on day 14 and 98.5, 97.9, 97.7 and 97.9 on day 21, respectively. No statistical differences were observed between treated groups.