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Haemonchus contortus is one of the major gastrointestinal nematodes responsible for significant economic and production losses of sheep. Diseases caused by this species lack effective anthelmintic products, and the search for new compounds to replace synthetic anthelmintics has been extensive. The present investigation assesses the in vitro activity of the essential oil of melaleuca (Melaleuca alternifolia), both free (TTO) and nanostructured (nanoTTO), and terpinen-4-ol (terp-4-ol) on eggs and larvae of H. contortus. Tests of egg hatching (EHT) and inhibition of larval migration (LMIT) were used to assess the in vitro efficacy of TTO, nanoTTO and terp-4-ol. Using EHT, at a concentration of 3.5 mg/ml, 100% inhibition occurred using TTO and terp-4-ol, with LC50 values of 0.43 and 0.63 mg/ml, and LC90 values of 1.75 mg/ml and 3.12 mg/ml, respectively. NanoTTO had lower activity, with 82.6% inhibition at the same concentration. Using LMIT, TTO and nanoTTO had a similar activity with 88.0% and 84.8% inhibition, respectively, at a concentration of 56 mg/ml. Terp-4-ol had a greater effect on larvae, with 85.7% inhibition at a concentration of 56 mg/ml and 82.4% at 3.5 mg/ml, demonstrating high activity at the lowest concentration tested. Therefore, the results indicate that all substances tested showed ovicidal and larvicidal activity against H. contortus. TTO, terp-4-ol and, mainly, nanoTTO may be targeted in in vivo studies, besides being a promising line of research into the control and treatment of veterinary important helminths.

The parasite Haemonchus contortus is one of the most pathogenic for small ruminants in tropical and subtropical regions worldwide, including Brazil. The objective of this study was to evaluate the structural changes induced in adult H. contortus after in vitro contact with Acacia mearnsii extract (AE), using scanning electron microscopy. Adult nematodes were collected from a naturally infected lamb. In the in vitro assay the parasites were placed in contact with AE (100 mg ml -1 ), for two hours at 37 o C. The nematodes used in the assays (exposed to AE and the negative controls) were analyzed using an electron scanning microscope (quadruplicate per treatment). In all replicates, similar morphological alterations were observed on the entire extension of the cuticle of the specimens that remained in contact with the EA in vitro assays, none significant lesion was observed in the negative control (not exposed to AE). These results indicate the direct action of EA on the cuticle of H. contortus in in vitro trials. Key words: Gastrointestinal nematodes, scanning electron microscopy, structural changes, tannins ResumoHaemonchus contortus é um dos parasitos mais patogênicos para pequenos ruminantes em regiões tropicais e subtropicais em todo o mundo, inclusive no Brasil. O objetivo do trabalho foi analisar alterações ultraestruturais na cutícula de H. contortus após contato com extrato de Acacia mearnsii. Os parasitos expostos ao extrato de Acacia mearnsii (EA) e os controles negativos foram analisados ao microscópio eletrônico de varredura. No teste in vitro, adultos de H. contortus foram coletados de um ovino naturalmente infectado, e os parasitos foram colocados em contato com o EA (100 mg mL -1 ), durante duas horas à 37 o C. Os nematódeos expostos ao EA apresentaram alterações morfológicas em toda a extensão da cutícula. As alterações morfológicas não foram observadas no controle negativo. Estes resultados indicam a ação direta do EA na cutícula de H. contortus.

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The aim of this study was to evaluate the potential uses of acacia extract (AE) on

Infestations of gastrointestinal parasitic nematodes in sheep result in significant costs to farmers. These infestations are controlled using synthetic anthelmintic treatments, which can result in the development of anthelmintic resistance in nematodes. The use of plants rich in condensed tannins (CTs) is a promising alternative for controlling infestations of harmful parasites in sheep, and could allow reduction of the chemical products used. This study investigated the in vitro effect of CTs from Acacia mearnsii extract (AE) on egg hatching and motility of third-stage larvae. Egg-hatching rate was measured after incubation with extracts for 48 h at 27 °C. The egg hatch test was performed with dilutions of 0. 09, 0.19, 0.39, 0.78, 1.56, 3.12, 6.25, 12.5, 25, 50, and 100 mg mL -1 . Distilled water was used as the negative control. The corresponding egg hatching inhibition percentages were 22.3, 32.3, 39.2, 49.1, 56.7, 59.0, 62.3, 77.3, 92.7, 98.3, and 100%. The concentration required to inhibit egg hatching in 50% of eggs (LC 50 ) was 2.85 mg mL -1 . The inhibition achieved with the negative control was 7.06%. A larval migration inhibition test was carried out after incubation with the extracts for 48 h at 27 o C, with AE and distilled water used in dilutions of 3.12, 6.25, 12.5, 25, 50, and 100 mg mL -1 . The corresponding percentages of migration inhibition were 16.5, 37.0, 56.3, 79.4, 91.8, and 97.1%. The concentration required to inhibit migration of 50% of larvae (LC 50 ) was 12.45 mg mL -1 . The inhibition achieved with the negative control was 8.53%. The in vitro ovicidal and larvicidal activity of CTs from AE indicate the anthelmintic effect of AE, suggesting the potential of CT extracts to be used as alternatives for controlling gastrointestinal nematode infestations in small ruminants. Key words: In vitro test, helminthes, tannins, phytotherapy, small ruminants ResumoO parasitismo gastrintestinal em ovinos acarreta inúmeros prejuízos aos produtores rurais. O controle é realizado basicamente através da administração de anti-helmínticos sintéticos o que estimula a seleção de parasitas resistentes. O uso de plantas ricas em taninos condensados (TC) apresenta-se como uma alternativa promissora no controle de helmintos em ovinos, reduzindo o uso de produtos químicos. Esse estudo avaliou o efeito in vitro dos TC provenientes da acácia (Acacia mearnsii) sobre a eclosão de ovos e a motilidade de larvas de terceiro estágio de nematódeos gastrintestinais de ovinos. A taxa de eclosão foi avaliada após incubação com o extrato por um período de 48 h a 27 o C. A eclodibilidade foi avaliada nas concentrações de 0,09; 0,19; 0,39; 0,78; 1,56; 3,12; 6,25; 12,5; 25; 50 e 100 mg mL -1 . No controle negativo utilizou-se água destilada. As inibições das eclosões foram 22,3; 32,3; 39,3; 49,1; 56,7; 59; 62,3; 77,3; 92,7; 98,3 . A ação ovicida e larvicida in vitro do tanino condensado do extrato de Acacia mearnsii encontrada no presente trabalho indica uma ação anti-helmíntica, apresentando potencial para sua apli...