Efeito do genótipo e do teor protéico da dieta na resistência de cordeiros à hemoncose experimental

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Diagnóstico de resistência anti-helmíntica em bovinos

Pós-graduação em Medicina Veterinária - FMVZ

Immune response to Haemonchus contortus and Haemonchus placei in sheep and its role on parasite specificity

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Fauna helmintológica de ovinos provenientes da microrregião de Jaboticabal, estado de São Paulo, Brasil

This study evaluated the prevalence and counting parasitism of different species of helminths of sheep from the micro-region of Jaboticabal of Sao Paulo state. For this, 66 animals naturally infected, four to 36 months of age, raised in pasture, were selected. The results of necropsy revealed the presence of seven genera and 12 species with the following prevalence and mean count: Haemonchus contortus: 100.0% (2947.2); Trichostrongylus colubriformis: 90.9% (3048.8); Cooperia curticei: 56.0% (256.5); Oesophagostomum columbianum: 48.4% (36.0); Cooperia punctata: 30.3% (94.5); Trichostrongylus axei: 22.7% (26.5); Strongyloides papillosus: 19.6% (83.0), Haemonchus contortus (L4): 7.5% (17.2), Cooperia pectinata: 10.6% (12.9), Trichuris ovis: 10.6 % (0.6); Cooperia spatulata 4.5% (0.3); Capillaria bovis: 4.5% (0.1). The mean parasitism of helminthswas 6524.7 per animal. Haemonchus contortus (adults and L4) and Trichostrongylus colubriformis corresponded to 45.4% and 46.7% of the average worm burden totally, respectively. Based in the results obtained in this study, can be concluded that the two most abundant species of helminths and important, the micro-region of Jaboticabal are Trichostrongylus colubriformis and Haemonchus contortus, and these two species amounted to 92.1% of the distribution percentage of helminths collected from all animals. These results demonstrate the importance of conducting a counts of eggs per gram of feces (EPG) in the herds of this region when FAMACHA is used on a particular property, since this method control does not allow to diagnostic the damage/clinical signs in animals infected by T. colubriformis, because this specie does not have hematophagism habit on animals.

Resistência de Haemonchus placei, Cooperia punctata e Oesophagostomum radiatum à ivermectina pour-on a 500mcgkg-1 em rebanhos bovinos no Brasil

The broad spectrum of endectocides and the easy use mode of their pour-on formulations are factors that have stimulated a higher frequency of use these drugs in cattle. In this study was evaluated the efficacy of ivermectin pour-on using the dose of 500mcgkg(-1), against nematodes in naturally infected cattle from different herds. Twelve calves were brought from each of the four farms selected. All the 48 calves used showed mean of eggs per gram of feces (EPG) greater than 500 considering three consecutive counts. Subsequently, animals from each herd were divided into two groups of six animals each, one treated pour-on with ivermectin 500mcgkg(-1) and other kept as untreated control. Calves were euthanized 14 days after treatment for counting the endoparasites. Ivermectin showed null effect against H. placei in all the herds evaluated. The drug was also ineffective against C. punctata in the herds from Jaboticabal, SP and Formiga, MG, and reached efficacy of 75.8% and 58.4% in herds from Sao Jose do Rio Pardo, SP and Sao Sebastiao do Para so, MG, respectively. Efficacies of 94.2% (Jaboticabal), 0.0% (Sao Jose do Rio Pardo), 94.2% (Formiga) and 39.2% (Sao Sebastiao do Para so) were detectedagainstO. radiatum. Based on these results obtained on the present study, the four populations of Haemonchus placei and Cooperia punctata evaluated were resistant to ivermectin pour-on using a dose of 500mcgkg(-1). Ivermectin-resistant strains of Oesophagostomum radiatum were found in two of the four herds evaluated.

Assessing resistance of ivermectin and moxidectin against nematodes in cattle naturally infected using three different methodologies

The objective of this study was to evaluate the accuracy of the faecal egg count reduction test (FECRT) and the faecal egg count efficacy test (FECET) to assess the resistance status of ivermectin (630 mu g/g) and moxidectin (200 mu g/kg), using the controlled efficacy test as a reference, and whether the results of the EPG are equivalent to the efficacy results from the parasitological necropsies. Two experiments were conducted. The results demonstrate that it was not possible to demonstrate that the EPG values were equivalent with the ivermectin and moxidectin efficacy obtained by parasitological necropsies, mainly if the phenomenon of parasites resistance is not advanced in a determined field population. Maybe the FECET technique would be possibly better than the FECRT. The high anthelmintic efficacy of 200 mu g/kg moxidectin, in naturally infected cattle, against field population of nematodes that are resistant to 630 mu g/kg ivermectin, was observed in this study. (C) 2013 Elsevier Ltd. All rights reserved.

Evaluation of clinical safety and anthelmintic efficacy of aurixazole administed orally at 24 mg/kg in cattle

The current study evaluated, in vivo, the clinical safety and the anthelmintic efficacy of 24% aurixazole (24 mg/kg), administered orally, in bovines. Two experiments were conducted: the first one evaluating the clinical safety of 24% aurixazole (24 mg/kg) in cattle, and a second one evaluating the anthelmintic efficacy of aurixazole (24 mg/kg) against gastrointestinal nematodes on naturally infected cattle. Based on the results of clinical safety, no alterations on clinical and haematological signs and on the biochemical values obtained in animals treated orally with aurixazole 24 mg/kg were observed. Regarding the results of reduction or efficacy, obtained by eggs per gram of faeces (EPG) counts, the formulation of aurixazole reached values superior to 99% (arithmetic means) in all post-treatment dates. In two occasions, this formulation reached maximum efficacy (100%). Comparing these results with the reduction percentages obtained by EPG counts, it is possible to verify that the values obtained by all three formulations were compatible with the efficacy results. Aurixazole reached maximum efficacy (100%) against Haemonchus placei, Cooperia spatulata and Oesophagostomum radiatum. Against Cooperia punctata, this formulation reached an efficacy index of 99.99%. Regarding aurixazole, no specific trials were conducted on the field in order to evaluate the behaviour of this molecule against helminths that are resistant to other molecules, specially isolated levamisole and disophenolat: Due to this fact, future studies will be necessary to assess the effectiveness of aurixazole against strains of nematodes that are resistant to levamisole and disophenolat, but the results of clinical safety and efficacy described in this study allow us to conclude that the aurixazole molecule, concomitantly with other measures and orally administered formulations, can be another important tool in the control of nematodes parasitizing bovines. (C) 2014 Published by Elsevier Ltd.

Nematode resistance to ivermectin (630 and 700 mu g/kg) in cattle from the Southeast and South of Brazil

Two high doses of ivermectin (630 mu g/kg and 700 mu g/kg) that are sold commercially in Brazil were evaluated in dose-and-slaughter trials with 144 naturally nematode-infected cattle from eight regions within the states of Minas Gerias, Sao Paulo and Rio Grande do Sul in Brazil. Treatment groups were based on fecal egg counts 1, 2, and 3 days before treatment; all animals studied had a minimum egg count of at least 500 eggs per gram of feces (EPG). Post-mortem analyses were conducted on day 14. The highest levels of resistance to ivermectin were found for Haemonchus placei, Cooperia punctata and Oesophagostomum radiatum; all populations of H. placei were resistant to the 630 mu g/kg dose, and 67% were resistant to 700 mu g/kg; 86% of C. punctata were resistant to the 630 mu g/kg dose, and 33% were resistant to 700 mu g/kg. A combined analysis revealed that 57% of O. radiatum were resistant to the lower dose of ivermectin. H. placei, C. punctata and O. radiatum, in order, were the nematode populations with the highest indices of resistance, whereas Trichostrongylus axei was the most susceptible to 630 and 700 mu g/kg dosages of ivermectin. The results of helminthic resistance to ivermectin for different populations of H. placei and C. punctata described in the present study support previous literature data, in which a small decrease in the average parasitic burden of C. punctata and a consequent increase of H. placei were observed in cattle from the Southeast, South and Center-West regions of Brazil. (C) 2014 Elsevier Ireland Ltd. All rights reserved.

Prevalência de nematódeos em ovinos (Ovis aries) pertencentes a diferentes microrregiões do estado de São Paulo, Brasil

Pós-graduação em Medicina Veterinária - FCAV

Estresse oxidativo em ovinos das raças Suffolk e Santa Inês experimentalmente infectados por Haemonchus contortus

Pós-graduação em Ciência Animal - FMVA

Dinâmica populacional de Rhipicephalus (Boophilus) microplus (Canestrini, 1887) em bovinos mestiços mantidos em pastagens de Brachiaria decumbens no município de Formiga, Minas Gerais

Pós-graduação em Medicina Veterinária - FCAV

Performance and parasite control of different genetic groups of lambs finished in irrigated pasture

The aim of this study was to compare the following four genetic groups of hair sheep: Santa Inês (SI), Morada Nova (MN), Brazilian Somali (BS), and the F1 1/2Dorper x 1/2Morada Nova crossbreed on traits related to growth and parasitic infection. Thirty-three male lambs of the same age and of simple birth, under the same pre-weaning management conditions were used in the experiment. After weaning the animals were housed in a completely randomized design in paddocks made of Panicum maximum cv. Tanzania. Along the course of the research, the performance of the four groups of sheep was observed to be negatively affected by gastrointestinal parasites, but there was a genotype effect to the average daily weight gain (ADWG), where the SI and F1 genotypes presented higher values. The effects of genotype, time and genotype x time interaction were significant in weight and corporal score (CS) measurements. The BS lambs had the highest CS values throughout the experiment despite not presenting greater weight gain when compared to the SI and F1 breeds. There were also significant effects of time and genotype x time interaction for packed cell volume (PCV) and FAMACHA© score (FAM) and only the time effect was significant in the total number of eggs per gram (EPG) and total plasma protein (TPP). The MN lambs showed higher PCV values and unlike the other groups, presented a FAMACHA© score below 3 and PCV above 23% even having a higher EPG tendency, especially in the initial phase, indicating a possible higher resilience to infection caused by gastrointestinal parasites.

Diagnosis of anthelmintic resistance in cattle in Brazil: a comparison of different methodologies

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Anthelmintic efficacy of ivermectin and abamectin, administered orally for seven consecutive days (100 mu g/kg/day), against nematodes in naturally infected pigs

The present study aimed to evaluate ivermectin and abamectin, both administered orally in naturally infected domestic swine, as well as analysing if the EPG (eggs per gram of faeces) values were equivalent with the ivermectin and abamectin efficacy obtained by 'parasitological necropsies. The animals were randomly selected based on the average of three consecutive EPG counts of Strongylida, Ascaris suum and Trichuris for experiment I, and of Strongylida and Trichuris for experiment II. After the random draw, eight animals were treated, orally, during seven consecutive days with 100 mu g/kg/day ivermectin (Ivermectina (R) premix, Ouro Fino Agronegocios), eight other animals were treated, orally, during seven consecutive days with 100 mu g/kg/clay abamectin (Virbamax (R) premix - Virbac do Brasil Industria e Comercio Ltda.), and eight pigs were kept as controls. EPG counts were performed for each individual animal at 14th day post-treatment (DPT). All animals (control and treatment) were necropsied at the 14th DPT. The results from both experiments demonstrate that both ivermectin and abamectin, administered orally for a continuous period of seven days, at a daily dosage of 100 mu g/kg, were highly effective (>95%) against Hyostrongylus rubidus, Strongyloides ransomi, Ascaris suum and Metastrongylus salmi. Against Oesophagostomum dentatum, abamectin presented over 95% efficacy against both evaluated strains, while ivermectin reached other strain as resistant. Regarding T. suis, both ivermectin and abamectin were effective (efficacies >90%) against one of the tested strains, while the other one was classified as resistant. Furthermore, the EPG values were equivalent with the ivermectin and abamectin efficacy obtained by parasitological necropsies. (C) 2014 Elsevier Ltd. All rights reserved.

Susceptibility of helminth species from horses against different chemical compounds in Brazil

By means of parasitological necropsies, the present study aimed to evaluate, in six experiments, the degree of susceptibility or resistance of different helminth species which naturally infect horses to ivermectin 0.2mg/kg, abamectin 0.2mg/kg, moxidectin 0.4mg/kg, trichlorfon 35mg/kg, ivermectin 0.2mg/kg+praziquantel 2.5mg/kg, abamectin 0.2mg/kg+praziquantel 2.5mg/kg and ivermectin 0.2mg/kg+6.6 mg/kg pyrantel. At experimental day zero, the horses were allocated to treatment groups based on average counts of strongylid eggs per gram of feces (EPG) obtained on days -3, -2 and -1. Oxyuris sp. infections were confirmed as positive or negative. All the animals in the six experiments were naturally infected by this helminth species. Each group (control or treated) consisted of six animals. All the assessed Habronema muscae populations analyzed were susceptible to ivermectin, abamectin and moxidectin. Of the six Trichostrongylus axei populations, four were susceptible to ivermectin, abamectin, moxidectin, trichlorfon and ivermectin+praziquantel, and two were resistant to abamectin+praziquantel and ivermectin+pyrantel. Both Strongyloides westeri populations analyzed were susceptible to ivermectin, abamectin, moxidectin and abamectin+praziquantel. For O. equi, resistance was found in four different populations treated with ivermectin, abamectin, moxidectin, trichlorfon and ivermectin+praziquantel. Only combinations of abamectin+praziquantel and ivermectin+pyrantel were effective against this parasite species. All the large strongyles diagnosed in the present study (Strongyus edentatus, Strongyus vulgaris and Triodontophorus serratus) were susceptible to all the chemicals tested, with the exception of trichlorfon. Of the Cyathostominae populations, one was diagnosed as resistant to ivermectin and another to trichlorfon. The remaining populations from this nematode group were considered to be sensitive to ivermectin, abamectin, moxidectin, ivermectin+praziquantel, abamectin+praziquantel and ivermectin+pyrantel. New studies should be performed in different regions to evaluate the efficacy of trichlorfon in others field populations of helminthes.