Marcelo Beltrão Molento

Chemical Composition of the Essential Oil of Tagetes minuta and Its Activity against Cochliomyia macellaria (Diptera: Calliphoridae)

Background: Myiasis produced by Diptera larvae is responsible for the invasion of body tissues, seriously compromising animal welfare and causing significant economic losses to livestock. Cochliomyia macellaria is an important agent responsible for secondary myiasis, exacerbating the primary myiasis that could be already installed. Tagetes minuta essential oil (TMEO) is known for its anthelmintic and insecticidal properties, and it could be a sustainable alternative for the control and treatment of myiasis. Aims: This study aimed to evaluate TMEO activity on the third instar larvae (L3) of C. macellaria under laboratory conditions. Original Research Article Chaaban et al.; EJMP, 18(1): 1-10, 2017; Article no.EJMP.32078 2 Methods: Essential oils of T. minuta fresh aerial parts were extracted by hydrodistillation, characterized by gas chromatography coupling mass spectrometry (GC-MS) and tested against C. macellaria. Groups of 20 L3 were placed on filter paper impregnated with increasing (from 1.25 to 20%) TMEO concentrations, equivalent to 0.19 to 3.18 μl/cm, solubilized in ethanol or acetone. Results: The major compounds of TMEO were dihydrotagetone (67.64%), trans-beta-ocimene (16.23%), trans-tagetone (10.14%) and verbenone (2.98%), respectively. The lethal concentrations of 50% were 0.678 and 0.580 for ethanol and 1.938 and 1.50 μl/cm for acetone, 24 and 48 h after TMEO exposure, respectively. The TMEO at 1.59 μl/cm caused 93.33% mortality to L3 after 48 h and the 0.7961 μl/cm caused an inhibition of 87.27% of L3 emergence. Conclusion: The TMEO had a time and concentration-dependent activity against L3 of C. macellaria; where optimal effects were observed using low concentrations.

Diagnosis of resistance alleles in codon 167 of the beta-tubulin (Cya-tbb-1) gene from third-stage larvae of horse cyathostomins.

Anthelmintic resistance is a serious problem for the control of equine gastrointestinal nematodes. In the present survey, 173 third stage larvae of cyathostomins were investigated from three different locations for the presence of the resistant genotype at codon 167 of the beta-tubulin gene, as this is the most prevalent mutation. The larvae from the state of Parana (n=67), Sao Paulo (n=54) and Santa Catarina (n=52), showed 61.2; 31.5 and 38.5% of the heterozygous resistant genotype - TTC/TAC, respectively. An unpublished mutation at codon 172 that results in a serine (S) to threonine (T) substitution was found in 17.9% (12/67) of samples from Parana; and 13.0% (7/54) of samples from Sao Paulo. We have compared the molecular diagnostic with the fecal egg count data (R2=-0.79) from the same farms, and consider that the use of routine molecular diagnostic in individual larva may help to determine the population genetic distribution that is associated with drug failure.

Gene silencing of Dim-1, a member of the disorganized muscle family, in Haemonchus contortus

RNA interference has been widely used in parasites. In Haemonchus contortus, reproducible silencing has been reported; however, in this species an altered phenotype has been observed for only a few genes silenced by RNA interference. The aim of this work was to evaluate the effect of silencing Dim-1, a member of the disorganized muscle family on third stage larvae (L3) of H. contortus. Effective silencing of Dim-1 in L3 led to reduced L3 migration and slowed larval development from L3 to early L4. To our knowledge, this is the first report to demonstrate Dim-1 silencing affecting phenotypic characteristics of this parasite.

Insecticide activity of Curcuma longa (leaves) essential oil and its major compound α-phellandrene against Lucilia cuprina larvae (Diptera: Calliphoridae): Histological and ultrastructural biomarkers assessment

Lucilia cuprina, known as the Australian blowfly, is of high medico-sanitary and veterinary importance due to its ability to induce myiasis. Synthetic products are the most frequent form of fly control, but their indiscriminate use has selected for resistant populations and accounted for high levels of residues in animal products. This study aimed to assess the effect of essential oil from leaves of Curcuma longa (CLLEO), and its major compound α-phellandrene against L. cuprina L3. An additional goal was to determine the morphological alterations in target organs/tissues through ultrastructural assessment (SEM) and light microscopy, as well as macroscopic damage to cuticle induced by CLLEO. Groups of 20 L3 were placed on filter paper impregnated with increasing concentrations of CLLEO (0.15 to 2.86 μL/cm2) and α-phellandrene (0.29 to 1.47 μL/cm2). Efficacy was determined by quantifying L3 mortality 6, 24 and 48 h after contact with CLLEO and by measuring the structural damage to L3. CLLEO and α-phellandrene inhibited adult emergence by 96.22 and 100%, respectively. Macroscopic cuticle damage, appeared as diffuse pigment and darkening of larval body, was caused by both extracts. The SEM revealed dryness on the cuticle surface, distortion of the sensorial structures and general degeneration in treated L3. Furthermore, alterations in target organs (digestive tract, fat body and brain) were noticed and shall be used as biomarkers in future attempts to elucidate the mechanism of action of these compounds. The vacuolar degeneration and pyknotic profiles observed in the brain tissue of treated larvae with both extracts and the decreased motility within <6 h after treatment leads us to suggest a neurotoxic activity of the products. This work demonstrates the potential use of CLLEO and α-phellandrene as bioinsecticides to be used against L. cuprina, representing an ecofriendly alternative for myiasis control in humans and animals.

Chemical composition of Piper gaudichaudianum essential oil and its bioactivity against Lucilia cuprina (Diptera: Calliphoridae)

Abstract Piper gaudichaudianum grows abundantly throughout the Brazilian Atlantic Forest. Essential oil extracted from this species has been reported to have larvicidal properties. The aim of the study was to characterize the essential oil (EO) of P. gaudichaudianum and its insecticide activity on the third instar larvae (L3) of Lucilia cuprina under laboratory conditions. Groups of 20 L3 were placed on filter paper impregnated with increasing concentrations of 2.5–30% (v/v), equivalent to 0.39–4.77 μL/cm2, solubilized in ethanol or acetone. The toxicity was determined by L3 mortality after 6, 24 and 48 h after contact. P. gaudichaudianum EO was also characterized using CG/MS. Lethal concentrations of 50% (LC50) 24 and 48 h after EO exposure were found to be 3.69 and 2.19 when solubilized in ethanol and 9.14 and 6.05 μL/cm2 when solubilized in acetone, respectively. The major compounds were germacrene B, δ-cadinene, γ-elemene, (Z)-cariophyllene, α-copaene, (E)-cariophyllene, α-calacorene, α-humulene and (E)-nerolidol. The study demonstrated the significant biological activities of P. gaudichaudianum EO (PGEO) compounds against L. cuprina.

Endoparasite and nutritional status of Suffolk lambs in seven production systems

Lambs are the most susceptible category for parasite infections; therefore, the choice of the production system can influence nutritional status and reduce parasite infections. The present study aimed to evaluate the endoparasites and nutritional status of meat lambs in seven production systems. In the feedlot, they were (S1) early weaned lambs in feedlot and (S2) unweaned lambs in feedlot with controlled suckling. On pasture, they were (S3) early weaned lambs on pasture without supplementation, (S4) early weaned lambs on pasture with concentrate supplementation post-weaning, (S5) unweaned and unsupplemented lambs on pasture, (S6) unweaned lambs on pasture with concentrate supplementation and creep-feeding and (S7) unweaned lambs on pasture with free access to creep-grazing on white clover (Trifolium repens). Suffolk lambs (n = 132) were evaluated from 45 to 101 days of age, at 14-day intervals (0, 14, 28, 42 and 56 days). Parasite faecal egg count (FEC), FAMACHA score (FMC), average daily weight-gain and body condition score (BCS) were evaluated. The animals were treated with anthelmintics when they had FMC 3, 4 or 5 and/or FEC above 700. BCS and FEC (r = –0.361) and BCS and FMC variables (r = –0.313) were negatively correlated (P ≤ 0.01). FEC was lower in feedlot and in creep-feeding animals than in the other systems after the second evaluation (28 days). The weaned feedlot-lamb and controlled-suckling systems presented the best performance. On pasture, the animals in creep-feeding and creep-grazing had the best performance. Weaned and unsupplemented lambs on pasture had the lowest daily weight-gain (63 g/day) and the highest FMC scores (43% of animals) and the lowest BCS (mean 1.5). The endoparasite and nutritional statuses of the lambs were strongly correlated and were influenced by the production system, mainly when the ewes were present and the lambs received supplementation on pasture.