Influence of breed and parasite challenge on the immune response to naturally acquired intestinal nematode infection in sheep.

Natural infection by intestinal nematodes was assessed in Santa Ines and Ile de France sheep breeds, over a five-month grazing period, with emphasis on the development of the immune response in lambs under two anthelmintic treatment regimens. Nineteen Santa Ines and 19 Ile de France male lambs were allocated into two treatment groups: animals under suppressive treatment with anthelmintics; and animals under targeted selective treatment (TST). The nematodes Trichostrongylus colubriformis and Strongyloides papillosus showed the highest infection intensity in the TST animals in both breeds. Parasite-specific immunoglobulin G levels were significantly higher and more rapidly induced in Santa Ines lambs. Additionally, these lambs had higher levels of parasite-specific immunoglobulin A in intestinal mucus. Animals under TST had higher means of mast cells and globule leukocytes in the intestinal mucosa due to longer and greater parasite challenge in comparison with the suppressive group. A breed effect (P < 0.05) was recorded for mast cells, with Santa Ines lambs presenting the highest counts. Although Santa Ines lambs had lower intestinal nematode counts than Ile de France lambs, they had shown a large variation in T. colubriformis burden, with most of them presenting a marked worm burden, despite showing an earlier and more intense immune response to intestinal nematode infection.

In vivo selection for Haemonchus contortus resistance to monepantel.

Gastrointestinal nematodes significantly affect the ovine industry, and Haemonchus contortus is considered the most pathogenic parasite in tropical regions. This situation is aggravated when the main strategy to control worms fails because of the genetic resistance that parasites acquire against anthelmintics. Aiming to anticipate the events involved in anthelmintic resistance, we induced monepantel resistance in H. contortus by in vivo subdosing of sheep hosts. Four successive passages of a monepantel-susceptible H. contortus isolate in Santa Ines or Ile de France sheep hosts resulted in three monepantel-resistant (efficacy varying from 0 to 58.5%) H. contortus isolates. Sheep hosts were treated from 0.075 mg/kg to the therapeutic dose of 2.5 mg/kg of monepantel in 19-26 rounds of selection for 112-133 weeks. Success in inducing H. contortus resistance to monepantel may have been affected by worm burden and by host-parasite interactions, including a possible effect of the breed of sheep hosts. We conclude that subdosing of sheep, although time-consuming, is an efficient in vivo strategy for the induction of monepantel resistance in H. contortus. The resistant parasites can be used in further studies to elucidate the genetic and biochemical events involved in the acquisition of anthelmintic resistance.

Establishment of co-infection and hybridization of Haemonchus contortus and Haemonchus placei in sheep.

This study aimed to evaluate the simultaneous infections of Haemonchus contortus and Haemonchus placei in sheep, as well as the production of hybrids. A parental group of lambs (n = 6) were mix-infected with 2000 infective larvae (L3) of H. placei and 2000 L3 of H. contortus. Faecal samples were taken from each of these six lambs to produce the first generation of L3 (F1-L3) in individual cultures. These F1-L3 were used to infect 12 lambs; six of them were euthanized at 42 days (Group F1-42) and six at 84 days (Group F1-84) post infection. Polymerase chain reaction (PCR) analysis, using species-specific primer pairs, was the gold standard method for identification of Haemonchus adult species and hybrids. The establishment rate of both species was similar in the parental group: 51.7% H. contortus and 48.3% H. placei. Of the 219 adult specimens from groups F1-42 and F1-84 analysed by PCR, eight (3.65%) were hybrids, 111 were H. contortus and 100 were H. placei. The morphological evaluation of the F1-L3 from the parental group showed a predominance of larvae with H. contortus size (51.5%) in comparison with H. placei (42.8%). In the second generation of L3 (F2-L3) produced by the F1-lambs, larvae with H. contortus morphology predominated, with 81.5% in the F1-42 group and 84.0% in the F1-84 group. In conclusion, an artificial mixed infection by H. contortus and H. placei was established in lambs and resulted in the production of a small number of hybrids among their offspring.

An Outbreak of Intestinal Obstruction by Ascaridia Galli in Broilers in Minas Gerais

Industrial broilers raised on helminthic medication-free feed were diagnosed with a severe disease caused by Ascaridia galli, characterized by intestinal hemorrhage and obstruction. A. galli was identified based on the morphological features of the nematode. Broilers were raised for a longer period (63 days) for weight recovery, grouped as stunted (n=500), had low body score and had fetid diarrhea. The duodenum-jejunum segment was the most severely affected with obstruction and had localized accumulation of gas. The intestinal mucosa was severely congested with petechial and suffusive hemorrhages. The outbreak resulted in morbidity of about 10% and mortality of up to 4% and was associated to the absence of preventive medication on feed and slack biosecurity. The reemergence of A. galli is discussed in view of the alternative poultry management and raising conditions for drug free and welfare.

An Outbreak of Intestinal Obstruction by Ascaridia Galli in Broilers in Minas Gerais

Industrial broilers raised on helminthic medication-free feed were diagnosed with a severe disease caused by Ascaridia galli, characterized by intestinal hemorrhage and obstruction. A. galli was identified based on the morphological features of the nematode. Broilers were raised for a longer period (63 days) for weight recovery, grouped as stunted (n=500), had low body score and had fetid diarrhea. The duodenum-jejunum segment was the most severely affected with obstruction and had localized accumulation of gas. The intestinal mucosa was severely congested with petechial and suffusive hemorrhages. The outbreak resulted in morbidity of about 10% and mortality of up to 4% and was associated to the absence of preventive medication on feed and slack biosecurity. The reemergence of A. galli is discussed in view of the alternative poultry management and raising conditions for drug free and welfare.(AU)

Age influence on quality of shell and penetration in bacterial laying lightweight eggs / Influência da idade na qualidade da casca e na penetração bacteriana em ovos de poedeiras leves

This study evaluated the influence of the bird's age on the quality of the shell and percentage of bacterial penetration in commercial eggs. White-shelled commercial eggs were used, laid by light laying hens in their first laying cycle at 21, 39, 51, and 62 weeks of age. Shell quality evaluations comprised: egg weight, specific gravity, percentage and thickness of shell, number and size of pores. For evaluations regarding bacterial penetration, strains of several enterobacterias and one salmonella were used, all of which resistant to Nalidixic acid (100µg/ml). The method employed for evaluation of bacterial penetration was filling the eggs with growth medium. The data were subjected to variance analysis with 5% of probability using SAS (Education Analytical Software, 2013). Eveb though increase in the laying hen's age caused reduction of the quality of eggshells, it failed to affect the percentage of penetration of the bacterial samples evaluated.(AU)

O presente estudo avaliou a influência da idade da ave sobre a qualidade da casca e na porcentagem de penetração bacteriana em ovos comerciais. Foram utilizados ovos brancos comerciais provenientes de poedeiras leves em primeiro ciclo de postura com 21, 39, 51 e 62 semanas de idade. As avaliações de qualidade da casca realizadas foram: peso do ovo, gravidade específica, porcentagem e espessura da casca, número e tamanho dos poros. Para as avaliações da penetração bacteriana, foram utilizadas cepas de diversas enterobactérias e uma salmonela, sendo todas resistentes ao ácido nalidíxico (100µg/mL). O método utilizado para a avaliação da penetração bacteriana foi por meio do preenchimento dos ovos com meio de cultura. Os dados foram submetidos à análise de variância com 5% de probabilidade utilizando-se o programa SAS - Statistical Analisys System (Education Analytical Software, 2013). O aumento da idade da poedeira promoveu a redução da qualidade da casca dos ovos, porém não foi capaz de influenciar a porcentagem de penetração das amostras bacterianas avaliadas.(AU)

Age influence on quality of shell and penetration in bacterial laying lightweight eggs / Influência da idade na qualidade da casca e na penetração bacteriana em ovos de poedeiras leves

This study evaluated the influence of the bird's age on the quality of the shell and percentage of bacterial penetration in commercial eggs. White-shelled commercial eggs were used, laid by light laying hens in their first laying cycle at 21, 39, 51, and 62 weeks of age. Shell quality evaluations comprised: egg weight, specific gravity, percentage and thickness of shell, number and size of pores. For evaluations regarding bacterial penetration, strains of several enterobacterias and one salmonella were used, all of which resistant to Nalidixic acid (100µg/ml). The method employed for evaluation of bacterial penetration was filling the eggs with growth medium. The data were subjected to variance analysis with 5% of probability using SAS (Education Analytical Software, 2013). Eveb though increase in the laying hen's age caused reduction of the quality of eggshells, it failed to affect the percentage of penetration of the bacterial samples evaluated.(AU)

O presente estudo avaliou a influência da idade da ave sobre a qualidade da casca e na porcentagem de penetração bacteriana em ovos comerciais. Foram utilizados ovos brancos comerciais provenientes de poedeiras leves em primeiro ciclo de postura com 21, 39, 51 e 62 semanas de idade. As avaliações de qualidade da casca realizadas foram: peso do ovo, gravidade específica, porcentagem e espessura da casca, número e tamanho dos poros. Para as avaliações da penetração bacteriana, foram utilizadas cepas de diversas enterobactérias e uma salmonela, sendo todas resistentes ao ácido nalidíxico (100µg/mL). O método utilizado para a avaliação da penetração bacteriana foi por meio do preenchimento dos ovos com meio de cultura. Os dados foram submetidos à análise de variância com 5% de probabilidade utilizando-se o programa SAS - Statistical Analisys System (Education Analytical Software, 2013). O aumento da idade da poedeira promoveu a redução da qualidade da casca dos ovos, porém não foi capaz de influenciar a porcentagem de penetração das amostras bacterianas avaliadas.(AU)

PCR primers for straightforward differentiation of Haemonchus contortus, Haemonchus placei and their hybrids.

Haemonchus contortus and Haemonchus placei are among the major parasites of small ruminants and cattle. Although infection with these nematodes is host-specific, with H. placei predominating in cattle and H. contortus in sheep, cross-infections are observed in areas where both parasites are sympatric, and hybrid offspring can occur. Therefore, a fast and precise method is required for differentiating the parasites. Identification based on spicule morphometry is the most common technique for differentiating Haemonchus species. However, because these measurements overlap between species, morphological analysis is insufficient for differentiating between helminth species. In this work, we present a reliable, conventional polymerase chain reaction (PCR)-based method that uses two species-specific primer pairs to differentiate between H. contortus and H. placei specimens and their hybrids. Each primer pair produces one single and distinct amplification band for each species, which enables the detection of hybrid specimens. These primer pairs were validated by testing eight different populations of H. contortus, H. placei and hybrids.

Acute Strongyloides venezuelensis infection did not prevent EAE development: implications for hygiene hypothesis.

Prevalence of allergic and autoimmune pathologies is clearly increasing in developed countries. This has been attributed to a decreased exposure to certain microorganisms and been referred as hygiene hypothesis. In this study we evaluated if a previous infection with Strongyloides venezuelensis would alter the progression of experimental autoimmune encephalomyelitis (EAE) in Lewis rats. Animals were initially infected with 4000 L3 infective larvae of S. venezuelensis by subcutaneous route. Encephalomyelitis was then induced during the acute phase of the infection by immunization with myelin basic protein emulsified with Complete Freund's Adjuvant plus Mycobacterium butyricum. Previous infection downmodulated cytokine production but did not change clinical and histopathological EAE manifestations. Cytometric analysis with antibodies specific for CD4+CD25+Foxp3+ regulatory T cells indicated that infection also did not alter the frequency of these cells in spleen and regional lymph nodes. This finding could partly explain the failure of this worm to avoid EAE progression. Altogether these results demonstrated that infection with S. venezuelensis was not able to modify EAE progression in Lewis rats. In the context of the hygiene hypothesis, these results reinforce the necessity of a comparative study among different helminth species to identify the ones with immunoregulatory competence.

Vaccination of sheep and cattle against haemonchosis.

Vaccines against gastrointestinal nematodes are one potential option for the control of parasitic gastroenteritis in ruminants. Excretory/secretory (E/S) and hidden antigens are being studied as candidates for vaccines against Haemonchus spp., which is a major parasite in cattle and small ruminants that are raised in warm climates. Protection has been observed after vaccination with some E/S proteases, particularly cysteine proteases and with some glycans that are abundant on the surfaces and in the secretory products of helminths. However, the most promising results are being obtained with glycoprotein antigens extracted from the microvillar surfaces of the Haemonchus contortus intestinal cells. These antigens are called 'hidden' because they are not exposed to the host's immune system during infection. Thus far, recombinant forms of these antigens have not been usefully protective. However, because only 5 µg of antigen is required per dose, production of a native antigen vaccine from adult parasites has been found to be practical and commercially viable. Trials indicate that a vaccine made from one particular isolate will cross-protect against geographically distant isolates.

Host-specificity and morphometrics of female Haemonchus contortus, H. placei and H. similis (Nematoda: Trichostrongylidae) in cattle and sheep from shared pastures in São Paulo State, Brazil.

To better evaluate the usefulness of female Haemonchus specimens for specific identification, we undertook a detailed analysis of the morphology of a collection of worms obtained from cattle and sheep in shared pastures. Based on the results, we also more precisely evaluated the host-specificity of Haemonchus contortus, H. placei and H. similis occurring sympatrically in a farm located in the western region of São Paulo State, Brazil. A synlophe analysis was employed to identify the three species of Haemonchus. In cattle, the predominant species was H. similis (90.9%), followed by H. placei (9.1%). With the exception of one H. placei specimen, only H. contortus was found in sheep. The longest body length was found for H. placei specimens, followed by H. contortus and then H. similis. It was possible to distinguish H. similis females from H. contortus and H. placei on the basis of vulval structure. The synlophe analysis proved to be very useful for identification of H. contortus, H. placei and H. similis in epidemiological studies involving different species of ruminants in the same pastures. The finding that H. placei and H. similis were adapted to cattle and that H. contortus was adapted to sheep also confirmed the high host-specificity of the three nematodes species.

Attempts to vaccinate ewes and their lambs against natural infection with Haemonchus contortus in a tropical environment.

A vaccine containing integral membrane glycoproteins from the intestine of Haemonchus contortus was evaluated in three groups of grazing sheep each containing 13 ewes and their 16 lambs naturally infected with gastrointestinal nematodes. Two groups were vaccinated with either 5 or 50µg of the antigen per immunisation, while the third, the control group, received adjuvant alone. The sheep were immunised six times at 3week intervals, partly because the vaccine antigens are hidden and thus no immunological boost would be delivered by subsequent infection and partly because the level of Haemonchus spp. challenge was expected to be high. The vaccinated ewes, first immunised approximately 1month before lambing, showed a circulating antibody response but no signs of reduced anaemia or Haemonchus spp. egg counts, compared with control ewes. Several ewes with severe haemonchosis in all three groups had to be given precautionary treatment with anthelmintic drugs. In contrast, vaccinating their lambs with either 5 or 50µg of the antigen per immunisation resulted in 10 fold higher antibody titres. In the case of the lower antigen dose this was associated with significantly less anaemia, 72% reduction in the overall number of Haemonchus spp. eggs produced and significantly fewer worms compared with control lambs. It is hypothesised that the heavily pregnant or lactating ewes did not have sufficient physiological reserves to mount a protective response following vaccination in the tropical weather and high challenge conditions that prevailed. Nevertheless, the vaccine could afford useful protection for lambs against H. contortus.

Androgen receptor mRNA measured by quantitative real time PCR is decreased in the urethral mucosa of patients with middle idiopathic hypospadias.

Androgen action is exerted through the androgen receptor. The normal 46,XY genital virilization depends on androgen receptor gene expression, which is tissue specific, and requires normal androgen receptor mRNA levels in androgen sensitive tissues. Hypospadias is a frequent male genital abnormality, potentially related to reduced androgen sensitivity in genital tissues. The aim of this study was to compare, by quantitative real time PCR, the amount of androgen receptor mRNA in cells obtained from the urethral mucosa of patients with middle idiopathic hypospadias with the androgen receptor mRNA levels observed in control phimosis subjects with eutopic urethral opening. Prepubertal individuals were studied, including 41 controls and 17 hypospadias patients with mean (SD) ages of 4.7 (2.1) years and 4.0 (3.0) years, respectively. We observed significantly less androgen receptor mRNA in the urethral mucosa of patients with hypospadias than in the controls (p=0.002). The correlation between the level of androgen receptor mRNA expression and the penile size was almost statistically significant only in hypospadias patients (r=0.47; p=0.053). We also established the number of CAG repeats in exon 1 of the androgen receptor gene by GeneScan analysis. No significant difference was observed in the number of CAG repeats when patients and controls were compared. A negative correlation between the CAG repeats and penile size was detected in patients with hypospadias, but not in controls. Our data suggest that a critical lower level of androgen receptor mRNA expression could be a determining factor in the development of middle hypospadias.

Alternativas para o controle de nematoides gastrintestinais de pequenos ruminantes / Alternative techniques for the control of gastrointestinal nematodes in small ruminants

Sheep and goat farming requires an efficient management program, due to losses caused by parasites in susceptible animals. Many factors may collaborate to improve infection tolerance in the herd, such as: genetics, nutrition, physiological status, and age. The problem caused by resistance to antihelmintic agents has led to the spread of alternative techniques for parasite controls. The latest strategies include selective treatment with the FAMACHA method, phytotherapy, biological control with predatory fungi, and strategies that still await scientific confirmation, such as homeopathy, the dilution of resistance with the introduction of susceptible parasites, and the combination of drugs without antihelmintic effect. The main objective of these methods is to reduce the usage of antiparasitic agents, thus slowing the development of resistance and promoting the better use of effective products and newly released products. The objective of this article is to describe techniques for controlling nematodes in small ruminants, and it is aimed at technicians interested in increasing their knowledge about the mechanisms of resistance to antihelmintic agents as well as alternatives to the use of these products.(AU)

A criação de ovinos e caprinos depende de um manejo eficiente, devido, principalmente, ao prejuízo causado por parasitos em animais susceptíveis. Vários fatores colaboram para que os animais tolerem as infecções parasitárias, como: genética, nutrição, estado fisiológico e idade. O grave problema causado pela resistência anti-helmíntica promoveu a difusão de técnicas alternativas de controle parasitário. Dentre essas novas estratégias incluem-se a adoção do tratamento parcial seletivo com o método FAMACHA, fitoterapia, controle biológico com o uso de fungos nematófagos e estratégias que ainda necessitam de mais dados como a homeopatia, a diluição da resistência com a introdução de parasitos sensíveis e a combinação de produtos químicos sem efeito antiparasitário. O objetivo central destes métodos é reduzir o uso de antiparasitários, retardando o desenvolvimento da resistência, e promover melhor utilização de produtos ainda eficazes na propriedade e de novos produtos que venham a ser lançados. Este artigo abordará as técnicas descritas acima para o controle de nematoides de pequenos ruminantes e é direcionado aos técnicos interessados em ampliar seu conhecimento sobre os mecanismos de resistência dos parasitos aos anti-helmínticos e de alternativas ao uso desses produtos.(AU)

Alternativas para o controle de nematoides gastrintestinais de pequenos ruminantes / Alternative techniques for the control of gastrointestinal nematodes in small ruminants

Sheep and goat farming requires an efficient management program, due to losses caused by parasites in susceptible animals. Many factors may collaborate to improve infection tolerance in the herd, such as: genetics, nutrition, physiological status, and age. The problem caused by resistance to antihelmintic agents has led to the spread of alternative techniques for parasite controls. The latest strategies include selective treatment with the FAMACHA method, phytotherapy, biological control with predatory fungi, and strategies that still await scientific confirmation, such as homeopathy, the dilution of resistance with the introduction of susceptible parasites, and the combination of drugs without antihelmintic effect. The main objective of these methods is to reduce the usage of antiparasitic agents, thus slowing the development of resistance and promoting the better use of effective products and newly released products. The objective of this article is to describe techniques for controlling nematodes in small ruminants, and it is aimed at technicians interested in increasing their knowledge about the mechanisms of resistance to antihelmintic agents as well as alternatives to the use of these products.

A criação de ovinos e caprinos depende de um manejo eficiente, devido, principalmente, ao prejuízo causado por parasitos em animais susceptíveis. Vários fatores colaboram para que os animais tolerem as infecções parasitárias, como: genética, nutrição, estado fisiológico e idade. O grave problema causado pela resistência anti-helmíntica promoveu a difusão de técnicas alternativas de controle parasitário. Dentre essas novas estratégias incluem-se a adoção do tratamento parcial seletivo com o método FAMACHA, fitoterapia, controle biológico com o uso de fungos nematófagos e estratégias que ainda necessitam de mais dados como a homeopatia, a diluição da resistência com a introdução de parasitos sensíveis e a combinação de produtos químicos sem efeito antiparasitário. O objetivo central destes métodos é reduzir o uso de antiparasitários, retardando o desenvolvimento da resistência, e promover melhor utilização de produtos ainda eficazes na propriedade e de novos produtos que venham a ser lançados. Este artigo abordará as técnicas descritas acima para o controle de nematoides de pequenos ruminantes e é direcionado aos técnicos interessados em ampliar seu conhecimento sobre os mecanismos de resistência dos parasitos aos anti-helmínticos e de alternativas ao uso desses produtos.

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

This study was carried out to evaluate the immune response in young Ile de France (IF) and Santa Ines (SI) sheep naturally infected by Oestrus ovis and gastrointestinal nematodes (GIN). Mast cells, eosinophils and globule leucocytes were enumerated in the upper respiratory tract (septum, middle meatus and ventral nasal conchae) and in the mucosa of abomasum and small intestine. Immunoglobulin G (IgG) levels in serum samples and immunoglobulin A (IgA) levels in mucus from the nasal, abomasum and small intestinal mucosae were determined against O. ovis, Haemonchus contortus and Trichostrongylus colubriformis antigens. Significant positive correlation coefficients were observed in both breeds between the number of O. ovis larvae×IgG against Oestrus crude extract (IF: r=0.58; SI: r=0.66; P<0.05), and between O. ovis larvae x IgG against Oestrus excretory and secretory products (IF: r=0.59; SI: r=0.63; P<0.05). Apparently, the presence of antibodies in the serum or nasal mucus, as well as inflammatory cells, was not able to efficiently protect against O. ovis infestation. With regard to GIN, the levels of immunoglobulins and the inflammatory cell numbers in the gastrointestinal mucosa presented a significant inverse relationship with H. contortus worm burden in SI animals and this may have contributed to the fact that these animals presented the lowest FEC and worm burden compared to IF. In conclusion, the immune responses against O. ovis and GIN are very similar and involve the recruitment of inflammatory cells and production of immunoglobulins against the parasites.

Evaluation of Cymbopogon schoenanthus essential oil in lambs experimentally infected with Haemonchus contortus.

Hematophagous gastrointestinal parasites cause significant economic losses in small ruminant grazing systems. The growing reports of multi-drug resistant parasites call for intensive research on alternative treatments for anthelmintics to help small ruminants cope with these parasites. Two-month-old lambs with mean body weight (BW) of 22.5 kg were experimentally infected with a multidrug-resistant Haemonchus contortus strain. Infected animals were dosed orally with Cymbopogon schoenanthus essential oil to evaluate its anthelmintic potential. Eighteen animals were allocated into three groups of six animals, and each received one of the following treatments: Group 1 - control (10 mL of water), Group 2 - C. schoenanthus essential oil (180 mg/kg BW); and Group 3 - C. schoenanthus essential oil (360 mg/kg BW). Animals received the oil once a day for 3 consecutive days. Lambs were evaluated clinically for blood biochemistry before, at 1, 5, 10, 15 and 20 days after treatment, and then were euthanized to assess the total worm burden. No statistically significant reduction in fecal egg count, packed cell volume or total worm count was observed after treatments. Also, no statistical difference among group means for blood levels of urea, creatinine, albumin, alkaline phosphatase, aspartate aminotransferase and gamma glutamyl transferase was found. Larval development assay (LDA) and egg hatch assay (EHA) were performed from feces of treated animals at 1, 5, 10 and 15 days after essential oil administration. An inhibition in LDA was observed 1 day after the 3-day treatment in larvae from feces of animals treated with 360 mg/kg essential oil. In conclusion, the essential oil at the doses of 180 mg/kg and 360 mg/kg was safe to sheep, but failed as an anthelmintic treatment when applied to young sheep artificially infected with a multidrug-resistant H. contortus strain.

Parasitism by Oestrus ovis: influence of sheep breed and nematode infections.

Previous studies showed that Santa Ines (SI) hair sheep were more resistant to gastrointestinal nematode infections (GIN) than Ile de France (IF) sheep. The present experiment aimed to evaluate if that reported resistance difference against GIN also occurred against Oestrus ovis infestation and also to evaluate the influence of O. ovis infestation on the gastrointestinal nematodes (GIN) infections. SI (n=12) and IF (n=12) young male lambs were weaned at 2 months of age and moved to a paddock (0.3 ha) with Brachiaria decumbens grass, where they also received concentrate ration. The animals were kept together during the experimental period (September to early December 2009). Fecal and blood samples were taken from all animals every 2 weeks and body weight and nasal discharge score (oestrosis clinic signs) were recorded on the same occasion. In early December 2009, all lambs were sacrificed and O. ovis larvae and GIN were recovered, counted and identified according to the larval stage. All animals were infested by different larval instars of O. ovis without any statistical difference between breeds (P>0.05). The SI lambs had an average of 24.8 larvae, and the intensity of infection ranged between 14 and 39 larvae, while the IF lambs showed an average of 23.5 larvae with the minimum and maximum from 11 to 36 larvae, respectively. SI lambs presented the lowest nematode fecal egg counts (FECs) and the lowest mean numbers of Haemonchus contortus, Trichostrongylus colubriformis and Strongyloides papillosus, however, there was no significant differences between group means (P>0.05). Inverse relationship between numbers of O. ovis larvae and gastrointestinal nematodes was observed in both breeds. SI sheep showed a significant increase in blood eosinophils and total IgE serum levels and these variables were negatively correlated with nematode FEC. A negative correlation was observed between total IgE serum level and H. contortus burden in both breeds. In conclusion, there was no breed difference regarding O. ovis infestation and in each breed, animals with more nasal bot fly larvae tended to display smaller worm burden.

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.

Influence of protein supplementation during late pregnancy and lactation on the resistance of Santa Ines and Ile de France ewes to Haemonchus contortus.

This experiment aimed to evaluate the effect of periparturient metabolizable protein (MP) nutrition on resistance to Haemonchus contortus in single rearing Ile de France and Santa Ines ewes. The restriction-fed iso-energetic diet was calculated to provide either 0.8 (low MP diet) or 1.3 (high MP diet) times MP, from three weeks before parturition until eight weeks into lactation. The ewes were experimentally infected with 1000 H. contortus infective larvae (L3) three times a week (Mondays, Wednesdays and Fridays), starting five weeks before the predicted date for parturition until a total of 15,000 L3 had been administered. While both breeds showed elevated fecal egg counts (FEC), these values were significantly lower for Santa Ines ewes than Ile de France ewes, but were independent of level of MP feeding. The latter also did not affect lamb weight gain and ewe body weight variation in each breed. Packed cell volume and total plasma protein for Santa Ines in all periods were significantly higher than those for Ile de France ewes (P<0.01) but were not affected by nutrition. In contrast, levels of serum IgG and IgA antibodies against somatic H. contortus infective larvae and adult antigens were similar between breeds but higher in animals that received high MP diets (P<0.05). The reduced body score of ewes at the beginning of the experiment probably influenced their high susceptibility to incoming larvae. Since, unexpectedly, MP scarcity was not achieved in this experiment, our data support the view that Santa Ines ewes are more resistant to H. contortus than Ile de France ewes.