Selection of an ivermectin-resistant strain of Rhipicephalus microplus (Acari: Ixodidae) in Brazil

Resistance to ivermectin (IVM) in field Populations of Rhipicephalus microplus of Brazil has been observed since 2001 In this work, four selection methods (infestations with: (I) IVM-treated larvae, (2) larvae from IVM-treated adult female ticks, (3) larvae from IVM-treated adult female ticks on an IVM-treated host, and (4) larvae obtained from W-treated females that produced eggs with a high eclosion rate) were used oil a field population with an initial ivermectin (IVM) resistance ratio at LC50 (RR50) of 1 37 with the objective to obtain experimentally a highly-resistant strain After ten generations, using these methods combined, the final RR50 was 8 06 This work shows for the first time that it was possible to increase IVM resistance in R. microplus in laboratory conditions. The establishment of a drug resistant R microplus strain is a fundamental first step for further research into the mechanisms of ivermectin-resistance in R. microplus and potentially methods to control this resistance (C) 2009 Elsevier B V All rights reserved

Infecções naturais em cervídeos (Mammalia: Cervidae) procedentes dos Estados do Mato Grosso do Sul e São Paulo, por nematódeos Trichostrongyloidea Cram, 1927

No período compreendido entre 1985 e 1996 foram necropsiados, para pesquisa de helmintos, 42 cervídeos, sendo sete Mazama americana, 16 M. gouazoubira, 13 Ozotoceros bezoarticus e seis Blastocerus dichotomus. Desses animais, foram colhidos 14.426 nematódeos Trichostrongyloidea, sendo 13.281 (92,06%) parasitos de abomaso e 1.145 (7,94%), de intestino delgado. Nesses órgãos, foram identificadas seis espécies de nematódeos: Haemonchus contortus, H. similis, Trichostrongylus axei, T. colubriformis, Cooperia punctata e C. pectinata. Todos os animais apresentaram infecções helmínticas por uma ou mais espécies, ocorrendo grande variação na intensidade de infecção (1 a 4.345 nematódeos). Ainda com relação à intensidade de infecção, os dados expressavam valores menores que 100 parasitos em 25 (59,52%) animais. Os valores mais altos de intensidade média das infecções foram observados em M. gouazoubira (596,37 helmintos) e em O. bezoarticus (331), e os menores, em M. americana (17,57) e B. dichotomus (75,5). Os dados mais expressivos de intensidade de infecção, abundância e prevalência foram observados para Haemonchus (larvas de 4º estágio), H. contortus, H. similis e T. axei. O gênero Haemonchus foi constatado em 35 animais, com prevalência de 83,33%; apresentou carga parasitária de 11.616 exemplares, representando 80,52% dos nematódeos verificados, sendo a maioria (8.903) constituída por formas imaturas. Por outro lado, H. similis foi a espécie predominante nas infecções e, portanto, a que apresentou maiores valores de abundância. Verificou-se o gênero Trichostrongylus em 24 (57,14%) animais, com carga parasitária de 2.444 exemplares, sendo 1.665 espécimes de T. axei, que representou 11,54% da carga parasitária obtida. As seis espécies de vermes identificadas nos cervídeos são comuns aos ruminantes domésticos nos Estados de São Paulo e Mato Grosso do Sul e dessa maneira não se observou nenhuma espécie de Trichostrongyloidea exclusiva dos cervídeos.

Eficácia anti-helmíntica comparativa da associação albendazole, levamisole e ivermectina à moxidectina em ovinos

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Marcadores fenotípicos para caracterização de caprinos com diferentes níveis de resistência às endoparasitoses gastrintestinais

The aim of this study was to evaluate and characterize phenotypically goats with different levels of resistance to gastrointestinal nematodes. For a period of 93 days, 60 F2 goats originated from ½ Saanen and ½ Anglo- nubian animals were kept in the same area of pasture. Every seven days, feces and blood were collected for eggs per gram counts of feces (EPG) and cultures of feces and to determinate the number of eosinophils, packed cell volume and total plasma protein, respectively. On the same day, the animals were weighed and submitted to body score condition and FAMACHA method to worm control. Based on the average of EPG, the twelve animals with the highest average (susceptible group) and the twelve animals with the lowest average of EPG (resistant group) were selected, slaughtered and necropsied to recovery, counting andparasites identification. The resistant animals present lower EPG mean (P <0.0001) and 4.7 folder less parasites than susceptible animals. The resistant group presented higher mean packed cell volume (26.48%) and total plasma protein (6.24 g / dl) than susceptible one (24,04% e 5,82g/dl, respectively). The average number of eosinophils was similar in both groups The Haemonchus sp. was the most prevalent in the culture of feces, followed by Trischostrongylus sp. and Oesophagostomum sp.. The counting of nematodes in the abomasum of susceptible group was higher than in resistant one. The species identified were H. contortus in abomasums and T. colubriformis in small intestine. It can be concluded that EPG, packed cell volume and total plasma protein were useful phenotypic markers to identify animals as resistant and susceptible to gastrointestinal nematodes infections

Host specificity of sheep and cattle nematodes in São Paulo state, Brazil

The trial was carried out to investigate parasite host specificity and to analyse the dynamics of infection with nematodes parasitizing sheep and catt:le raised together or separately in São Paulo state, Brazil, and, also to clarify doubts about the systematics of species of the genus Haemonchus on the basis of cytological and morphological studies. Ten steers and 32 ewes were randomly assigned to three paddocks (P), as follows: P1, 5 steers; P2, 5 steers and 16 ewes; and P3, 16 ewes. The animals remained on these paddocks in continuous grazing throughout the trial (1-yr period). Faecal exams and larvae counting on pasture were performed fortnightly. Once a month two tracer lambs were placed in each paddock, while two tracer calves were also placed, but only in the eighth month of the trial. All these animals were slaughtered for worm identification and counting. At the end of the trial, one steer and one ewe from P2, which showed high faecal egg counts, were also slaughtered for the same purpose. Nematodes identified cytogenetically as H. placei presented spicule hooks longer than those identified as H. contortus. The following distribution of parasites in cattle and sheep was observed: Bunostomum phlebotomum, H. similis, Mammomonogamus laryngeus strongly adapted to cattle, H. placei and Cooperia punctata more adapted to cattle than to sheep, Trichostrongylus axel and C. spatulata apparently more adapted to cattle, T. colubriformis strongly adapted to sheep, H. contortus more adapted to sheep than to cattle and C. curticei apparently more adapted to sheep. Cross-infection was shown to occur involving some species, however, with time the animals apparently eliminate the species that are not well adapted to them. Therefore, grazing management systems using cattle and sheep appear to be promising for worm control in southeastern Brazil. (C) 1997 Elsevier B.V. B.V.

Comparison of the susceptibility of Santa Ines and Ile de France ewes to nematode parasitism around parturition and during lactation

Breeds of sheep with resistance to nematode infection often display a reduced periparturient rise (PPR) in faecal egg counts (FEC) when compared with susceptible sheep. This trial was carried out to compare the resistance of Santa Ines, an indigenous Brazilian breed of sheep, and Ile de France ewes to natural infections by gastrointestinal nematodes, especially in the periparturient period. Twelve Santa lnes and 10 Ile de France ewes were estrus synchronized and then mated (December 2001). Lambing occurred from 30 April to 19 June 2002 and the lambs were weaned at 60 days of age. Faecal egg counts, packed cell volume (PCV), total plasma protein levels and peripheral eosinophils counts were determined from November 2001 to September 2002. To prevent deaths, individual treatment with anthelmintics was provided to ewes with FEC higher than 4000 eggs per gram (EPG) or with PCV lower than 21%. The percentage of Santa Ines ewes treated with anthelmintics was lower than that of Ile de France sheep. Eight of the 10 Ile de France ewes were treated, with one of them requiring four treatments, one requiring three treatments, and two requiring two treatments. The remaining four received a single treatment. In contrast, only 5 of the 12 Santa lnes ewes required treatment and for each this was done only once. The mean values of PCV were in the normal range in the Santa Ines ewes. In contrast, mean PCVs of Ile de France ewes reached a low of 24.5% in the second month after lambing and were significantly lower than Santa Ines 1 month before lambing (P < 0.05) and 2 months after lambing (P < 0.07). The mean plasma protein level was significantly lower in the Ile de France ewes in the second month after lambing (P < 0.01) coinciding with a reduction in PCV. The ewes of both breeds had high mean numbers of eosinophils in blood, which increased even further post-weaning when a marked reduction in FEC occurred. Haemonchus larvae were the most numerous genus in faecal cultures for both breeds followed by Trichostrongylus, Oesophagostomum and Cooperia. A periparturient rise in FEC was observed in both breeds. However, Santa Ines ewes showed a higher capacity to support the infection in an environment contaminated with large number of infective larvae of gastrointestinal nematodes. (C) 2004 Elsevier B.V. All rights reserved.

Nematode burdens and cellular responses in the abomasal mucosa and blood of Florida Native, Rambouillet and crossbreed lambs

This experiment was carried out to compare the worm burden and cellular responses in the abomasal mucosa and blood of Florida Native and Rambouillet lambs and also in animals produced by crosses of these two breeds (generations F1 and F2). Animals were exposed to infection by gastrointestinal nematodes on three different occasions. The first infection was natural, occurring while they were suckling lambs. After weaning, they were kept indoors for 53 days and then were allowed to graze a contaminated pasture for 50 days for a second natural infection. The third infection was an artificial challenge with 6000 Haemonchus contortus infective larvae. The highest mean fecal egg counts (FEC) values were found in Rambouillet lambs followed in decreasing order by F1, F2 and Florida Native lambs. Throughout the trial, most of the high mean packed cell volumes and plasma protein levels were recorded in the F2 lambs; in contrast, most of the low values were found in the Rambouillet lambs. During the natural infection period, the highest percentages of larvae in the fecal cultures of the lambs were Haemonchus. However, high percentages of Trichostrongylus larvae were found particularly in Florida Native lambs. The mean number of blood eosinophils increased after the artificial challenge, reached a peak 21 days after infection and then declined. The highest and lowest blood eosinophil means were recorded in F2 and Florida Native lambs, respectively. The H. contortus burden was significantly higher in Rambouillet and in F1 lambs than in Florida Native and F2 lambs (p < 0.05), while no significant differences were recorded among eosinophil, mast cell and globule leucocyte counts in the abomasal mucosa (p > 0.05). The highest correlation coefficient recorded at the end of this study was between FEC and worm burden (r = 0.7). These two parameters showed a moderate negative correlation with PCV, plasma protein and mast cell counts in the abomasal mucosa. The results obtained in this study indicate that crossbreeding Florida Native and Rambouillet sheep can be a rapid way to combine and improve the characteristics of these two breeds. The parasitological results were promising. however, more studies will be necessary to verify the impact of crossbreeding in other traits. (C) 1999 Elsevier B.V. B.V. All rights reserved.

Resistance of Santa Ines, Suffolk and Ile de France sheep to naturally acquired gastrointestinal nematode infections

A study was conducted to assess the breed resistance against nematode infections in Santa Ines, Ile de France and Suffolk male lambs over a 9-month period in São Paulo state, Brazil. Lambs were born during the winter (year 2000) and were weaned at 2 months of age. The animals were then housed and treated with anthelmintics to eliminate natural infections by gastrointestinal nematodes. In late October 2000, lambs were placed in a paddock, where they stayed until August of the following year. Fecal and blood samples were taken from each animal every 2 weeks. on the same day, a pasture sample was collected to determine the number of infective larvae on the herbage. To prevent deaths, individual treatment with anthelmintics was provided to lambs with fecal egg counts (FEC) higher than 4000 eggs per gram (EPG) or with a packed cell volume (PCV) lower than 21%. In August 2001, all animals were slaughtered and the worms present in samples of the gastrointestinal contents were identified and counted. Most of the Suffolk and Ile de France sheep received three to six anthelmintic treatments over a period of 7 months, while most of the Santa Ines were not treated. Reductions in PCV and plasma protein values associated with high FEC and worm burdens were recorded, particularly, in Suffolk and Ile de France lambs. Haemonchus contortus and Oesophagostomum columbianum burdens and number of nodular lesions caused in the large intestine by O. columbianum larvae were significantly lower in Santa Ines sheep. All three breeds showed similar Trichostrongylus colubriformis worm burdens. The relative resistance of Santa Ines young male sheep was superior to that of Suffolk and Ile de France sheep. (C) 2004 Elsevier B.V. All rights reserved.

Why is it important to correctly identify Haemonchus species?

Infecções por Haemonchus spp. são uma das principais causas de perda econômica nas criações de ruminantes devido à redução no ganho de peso e mortalidade de bovinos e pequenos ruminantes, especialmente em regiões com clima tropical e subtropical. A identificação precisa das diferentes espécies, bem como o conhecimento sobre a epidemiologia das gastroenterites parasitárias, são fundamentais para a elaboração de estratégias sustentáveis de profilaxia das parasitoses. Essa revisão tem por objetivo central, abordar os principais métodos parasitológicos utilizados na identificação morfológica das espécies, os quais se caracterizam pela facilidade e baixo custo. Na maioria dos estudos realizados no Brasil, a distinção entre as espécies Haemonchus contortus e Haemonchus placei não tem sido considerada. Vários relatos de H. contortus, particularmente em bovinos, podem se tratar na verdade da infecção dos animais por H. placei. A identificação correta das espécies é, portanto, fundamental. Além das medidas dos espículos dos exemplares machos, outros detalhes morfológicos, tais como a sínlofe, devem ser avaliados com o objetivo de auxiliar na diferenciação das espécies. Mensurações das larvas infectantes, obtidas em coproculturas, podem também indicar a espécie de Haemonchus presente. Esse procedimento pode ser útil especialmente em estudos que não envolvem a necropsia de animais, como é o caso de testes destinados a avaliar a resistência anti-helmíntica em rebanhos.

Parasitism by Oestrus ovis: Influence of sheep breed and nematode infections

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

Resistance of Santa Ines and crossbred ewes to naturally acquired gastrointestinal nematode infections

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

Immune responses in sheep naturally infected with Oestrus ovis (Diptera: Oestridae) and gastrointestinal nematodes

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

Efficacy of Duddingtonia flagrans and Arthrobotrys robusta in controlling sheep parasitic gastroenteritis

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Caenorhabditis elegans as a model to screen plant extracts and compounds as natural anthelmintics for veterinary use

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Anthelmintic activity of Cymbopogon martinii, Cymbopogon schoenanthus and Mentha piperita essential oils evaluated in four different in vitro tests

Anthelmintic resistance is a worldwide concern in small ruminant industry and new plant-derived compounds are being studied for their potential use against gastrointestinal nematodes. Mentha piperita, Cymbopogon martinii and Cymbopogon schoenanthus essential oils were evaluated against developmental stages of trichostrongylids from sheep naturally infected (95% Haemonchus contortus and 5% Trichostrogylus spp.) through the egg hatch assay (EHA), larval development assay (LDA), larval feeding inhibition assay (LFIA), and the larval exsheathment assay (LEA). The major constituent of the essential oils, quantified by gas chromatography for M. piperita oil was menthol (42.5%), while for C. martinii and C. schoenanthus the main component was geraniol (81.4% and 62.5%, respectively). In all in vitro tests C. schoenanthus essential oil had the best activity against ovine trichostrongylids followed by C. martini, while M. piperita presented the least activity. Cymbopogon schoenanthus essential oil had LC(50) value of 0.045 mg/ml in EHA, 0.063 mg/ml in LDA, 0.009 mg/ml in LFIA, and 24.66 mg/ml in LEA. The anthelmintic activity of essential oils followed the same pattern in all in vitro tests, suggesting C. schoenanthus essential oil could be an interesting candidate for nematode control, although in vivo studies are necessary to validate the anthelmintic properties of this oil. (C) 2011 Elsevier B.V. All rights reserved.