A polymorphic CD4 epitope related to increased susceptibility to Babesia bovis in Canchim calves.

Different allelic forms of bovine CD4 were previously described in cattle and were also observed in Canchim calves examined in the present experiment. However, the functional relevance of these different CD4 phenotypes has not yet been investigated. CD4 + T helper cells are known to play a central role in immune control against Babesia bovis infection. Thus, our study aimed to compare the profiles of immune cells, specific antibody titers and blood infection levels measured by qPCR (quantitative polymerase chain reaction) in calves naturally infected with B. bovis, phenotyped as CD4- (absence of anti-CD4 staining), CD4 + (intermediate staining) or CD4 ++ (high staining). The CD4 mRNA precursor was also measured in these animals. Calves with the CD4- phenotype showed higher amounts of B. bovis DNA in blood samples, compared to the other CD4 phenotypes. It was also observed that these calves with higher levels of infection had lower amounts of natural killer cells and higher expression of the CD4 gene, which can be interpreted as a compensation for the failure of the altered CD4 receptor to recognize relevant B. bovis epitopes.

Peripartum Phenomenon in Crioula Lanada Sheep Susceptible and Resistant to Gastrointestinal Nematodes.

This study aimed at evaluating parasitological and blood variables in native breed Crioula Lanada sheep belonging to the same herd, to identify and compare susceptible or resistant individuals to gastrointestinal nematodes during gestation and lactation phases. For this purpose, 18 Crioula sheep were used within 2 years of evaluation, in which blood and feces samples and weight of the animals were taken from their 4th month of gestation until the weaning of their lambs, in the 4th month postpartum. Feces samples were used for counting eggs per gram of feces (EPG) and, thus, to identify 12 resistant ewes (EPG < 1,000) and 6 susceptible (EPG > 1,000) to gastrointestinal nematodes. The identification of infective larvae was also performed. Blood was used for analysis of packed cell volume (PCV), eosinophil count, total plasma protein, and immunoglobulin G level against Haemonchus contortus infective larvae. The Kruskal-Wallis non-parametric comparison test was used to evaluate the differences between days of parturition and linear mixed-effects model using package lme4 in R to evaluate the groups. The main parasite species observed in the feces samples were Haemonchus, Trichostrongylus, Oesophagostomum, Ostertagia, and Cooperia in similar proportions in both groups. Susceptible ewes presented peaks of EPG at the beginning of lactation and lower PCV values throughout the study. No difference between groups was observed concerning other blood variables or body weight, but some changes were observed along with the gestation and lactation phases within each group. The physiological response of sheep to nematode infection is a useful tool to identify the most susceptible individuals within the same breed and herd and to select the most genetically resistant individuals.

Local and systemic immune mediators of Morada Nova lambs with divergent Haemonchus contortus resistance phenotypes.

AIMS: Local and systemic immune mediators of Morada Nova lambs with divergent Haemonchus contortus resistance phenotypes were evaluated. METHODS AND RESULTS: Lambs were ranked through faecal egg counts (FEC) after two parasitic challenges with 4,000 H.contortus L3 . After the second challenge, the lambs underwent a third artificial infection and were euthanized 7 days later. Immune-related genes were quantified locally in abomasal mucosa and lymph nodes (CD4, IFNγ, IL4, IL5, IL13, IL2RA and MS4A2) and systemically in the whole blood (IL4 and IL13). Anti-H. contortus IgG and IgA antibodies and eosinophils and mast cells counts were also investigated. Resistant animals presented higher systemic IgG and IgA titres, both negatively correlated with FEC. Susceptible animals had higher blood levels of IL4 transcripts. At the local level, resistant lambs had higher eosinophils counts and superior MS4A2 levels in abomasal fundic mucosa, besides higher IgA levels in abomasal mucus, while susceptible lamb had superior IL4 expression in abomasal lymph nodes. CONCLUSION: These data indicate that resistant lambs had an immune response mediated by antibody-mediated cytotoxicity. Also, the systemic humoral profile, particularly IgA isotype, seems to be a good resistance marker for Morada Nova sheep, as we found differences between groups even when FEC did not differ.

Use of molecular markers can help to understand the genetic diversity of Babesia bovis.

Cattle babesiosis is a tick-borne disease responsible for significant losses for the livestock industries in tropical areas of the world. These piroplasms are under constant control of the host immune system, which lead to a strong selective pressure for arising more virulent or attenuated phenotypes. Aiming to better understand the most critical genetic modifications in Babesia bovis genome, related to virulence, an in silico analysis was performed using DNA sequences from GenBank. Fourteen genes (sbp-2, sbp-4, trap, msa-1, msa-2b, msa-2c, Bv80 (or Bb-1), 18S rRNA, acs-1, ama-1, ß-tub, cp-2, p0, rap-1a) related to parasite infection and immunogenicity and ITS region were selected for alignment and comparison of several isolates of Babesia bovis from different geographic regions around the world. Among the 15 genes selected for the study of diversity, only 7 genes (sbp-2, sbp-4, trap, msa-1, msa-2b, msa-2c, Bv80) and the ITS region presented sufficient genetic variation for the studies of phylogeny. Despite this genetic diversity observed into groups, there was not sufficient information available to associate molecular markers with virulence of isolates. However, some genetic groups no were correlated with geographic region what could indicate some typical evolutionary characteristics in the relation between parasite-host. Further studies using these genes in herds presenting diverse clinical conditions are required. The better understanding of evolutionary mechanisms of the parasite may contribute to improve prophylactic and therapeutic measures. In this way, we suggest that genes used in our study are potential markers of virulence and attenuation and have to be analyzed with the use of sequences from animals that present clinical signs of babesiosis and asymptomatic carriers.

Differences in immune responses to Haemonchus contortus infection in the susceptible Ile de France and the resistant Santa Ines sheep under different anthelmintic treatments regimens.

Understanding the immunological basis of resistance to gastrointestinal nematode infections in livestock is important in order to develop novel methods of parasite control such as vaccination or genetic selection for parasite resistance. The present study aimed to investigate differences in immune response between parasite resistant Santa Ines and susceptible Ile de France sheep breeds to natural Haemonchus contortus infection. Parasitological parameters, humoral immunity, local and circulating cellular immune responses were evaluated in 19 Santa Ines and 19 Ile de France lambs undergoing different anthelmintic treatments regimens: suppressive treatments (SUP) or targeted selective treatments (TST) over a 5-month grazing period. Santa Ines lambs had significantly lower Haemonchus faecal egg count and worm burden compared to Ile de France regardless of treatment regime. In addition, circulating blood eosinophils count and parasite-specific IgG levels were significantly higher and more rapidly induced in Santa Ines lambs. Abomasal immune responses were generally greater in the resistant breed, which had significantly higher levels of parasite-specific IgA in mucus, and elevated number of globule leukocytes and CD3+ T cells within the abomasal mucosal. Furthermore, numbers of POU2F3+ epithelial cells, a tuft-cell specific transcription factor, were also elevated in the Santa Ines breed, suggesting that this breed is better able to initiate T-helper type 2 immune responses within the abomasum. In conclusion, the differential immunological responses detailed here are relevant to understanding resistance to gastrointestinal nematodes in other host breeds, as well as to resistance breeding as a sustainable control approach for parasitic infections.

Elimination of erroneous results related to bovine mononuclear cell immunophenotyping by antibodies binding to Fc receptors.

Blocking immunoglobulin G (IgG) binding receptors on leukocytes is an established and highly recommended preventive procedure for immunological assays. Failing to prevent such nonspecific binding can lead to erroneous results. Several studies testing different blocking reagents have been performed in murine or human cells, however, there are no specific studies on bovine cells. Our study aimed to investigate the efficiency of blocking reagents to inhibit the nonspecific binding of mouse monoclonal antibodies (mAbs) to bovine peripheral blood cells. We observed nonspecific interactions of IgG2a and IgG2b negative isotypes with bovine leukocytes, but not IgG1. We found that these nonspecific bindings could be eliminated by blocking with purified mouse IgG, whereas little or no blocking effect was observed when bovine serum or Mouse Seroblock FcR were applied. Moreover, in the absence of an efficient blocking reagent, the percentage of CD335 positive cells was significantly higher than in the group previously blocked with mouse IgG. Based on these results, and due to the lack of specific commercial blocking reagents for bovine cells, our recommendation is to use purified mouse IgG as a blocking reagent for immune assays targeting bovine leukocytes in order to enhance the accuracy of the results.

Strategic vaccination of hair sheep against Haemonchus contortus.

In this study, we evaluated in two trials a protocol designed to protect hair sheep using Barbervax®, a vaccine containing Haemonchus contortus gut membrane glycoprotein antigens. Results indicated that naturally infected vaccinated sheep had significant egg count reductions (90.2 ± 4.03%) compared with controls, although blood parameters remained relatively unchanged probably because the level of challenge was low. Vaccination prevented the periparturient rise in egg shedding of ewes, as well as egg shedding in lambs (37.1%). In the second trial, sheep which were experimentally exposed to higher artificial challenge also showed an efficient response to the vaccine as confirmed by high antibody levels and reduced egg counts and worm burdens (87 ± 5.4% and 79%) respectively. Thus, we believe that the vaccine should be integrated with other management practices for meat hair sheep as it has the advantages of adequate efficacy, reducing anthelmintic utilization and avoiding milk and environmental contamination with chemical residues.

Development of a loop-mediated isothermal amplification (LAMP) assay for the detection of Anaplasma marginale.

Parasitemia generated by Anaplasma marginale causes significant losses in the cattle industry. A major constraint to the effective control and management of anaplasmosis in livestock is the lack of a rapid and reliable diagnostic test to identify the parasite and allow for immediate therapy. In the present study, we developed a novel DNA-based assay for the detection of A. marginale in bovine blood samples, using loop-mediated isothermal amplification (LAMP). DNA from six cattle and hemoparasite samples (Babesia bovis, Babesia bigemina, Anaplasma centrale and A. marginale) were tested for specificity, sensitivity and cross-reactions. The developed LAMP procedures were also confirmed and compared with the qPCR method. The same gene sequence (major surface protein 1b, msp1b) of A. marginale was used to design a set of primers for the LAMP and qPCR assays. The results showed that LAMP is specific, as no positive signal was observed for the other tested hemoparasites. However, the sensitivity of the qPCR assay was ten times higher than LAMP. Our findings indicate that this LAMP method has a good sensitivity and high specificity for the detection of A. marginale and may have a potential application in the detection and differentiation of bovine anaplasmosis.

Immune humoral response of young lambs naturally infested by Oestrus ovis (Diptera: Oestridae) / Resposta imune humoral de cordeiros jovens naturalmente infestados por Oestrus ovis (Diptera: Oestridae)

Abstract Twenty-six newborn lambs were evaluated for 21 weeks, from birth to slaughter, to assess their plasma anti-Oestrus ovis immunoglobulin (IgG) using the ELISA technique. On the last day of sampling, all the lambs were slaughtered and O. ovis larvae were recovered, quantified and identified according to the larval stage. High levels of IgG were observed over the first three weeks of life, thus indicating that antibodies are transferred via colostrum from ewes to lambs. Afterwards, the antibody levels declined progressively until the lambs were 11 weeks of age and subsequently started to increase again when they were around 13 weeks of age, reaching the apex on the last week of sampling. All the lambs were parasitized with different larval stages of O. ovis, with an average of 39 larvae per lamb, and the intensity of the infestation ranged from 10 to 97 larvae. However, there was non-significant correlation coefficients between IgG levels and O. ovis larval burden (P > 0.05). In conclusion, although the lambs became infested with O. ovis at an early age, the larval burden was not associated with specific IgG levels.

Resumo Vinte e seis cordeiros recém-nascidos foram avaliados por 21 semanas, desde o nascimento até o abate, para avaliar os níveis plasmáticos de imunoglobulina (IgG) anti-Oestrus ovis utilizando-se a técnica de ELISA. No último dia de coleta, todos os cordeiros foram abatidos e as larvas de O. ovis foram recuperadas, quantificadas e identificadas de acordo com o estádio larval. Foram observados altos níveis de IgG nas primeiras três semanas de vida, indicando que os anticorpos são transferidos por meio do colostro das ovelhas para os cordeiros. Posteriormente, os níveis de anticorpos diminuíram progressivamente, até os cordeiros completarem 11 semanas de vida. Os níveis de IgG começaram a aumentar novamente a partir de 13 semanas de idade, atingindo o ápice na última semana de coleta. Todos os cordeiros estavam parasitados com diferentes estádios larvais de O. ovis com uma média de 39 larvas por cordeiro, e a intensidade da infestação variou de 10 a 97 larvas. Porém, não houve correlação significativa entre os níveis de IgG e a carga larval de O. ovis (P > 0,05). Em conclusão, embora os cordeiros tenham sido infestados com O. ovis ainda jovens, a carga larval não foi associada a níveis específicos de IgG.

Helminth infections and hybridization between Haemonchus contortus and Haemonchus placei in sheep from Santana do Livramento, Brazil / Infecções helmínticas e hibridização entre Haemonchus contortus e Haemonchus placei em ovinos criados em Santana do Livramento, Brasil

Abstract The occurrence and intensity of helminth infections were evaluated in sheep from pastures shared with cattle. In 2015 and 2016, young male sheep acquired in Santana do Livramento, Rio Grande do Sul, Brazil, were finished in integrated crop-livestock system. We selected the 12 sheep that showed the highest number of nematode eggs per gram of faeces to search for worms in the gastrointestinal tract. Haemonchus contortus and Trichostrongylus colubriformis were the major parasites. H. contortus presented mean intensities of 1,159 and 257 worms in 2015 and 2016, respectively. T. colubriformis displayed mean intensities of 4,149 and 2,427 worms in 2015 and 2016, respectively. Of the 127 male specimens of Haemonchus spp. analysed by Polymerase Chain Reaction (PCR), 125 were H. contortus, one Haemonchus placei and one hybrid. Other species detected were Cooperia punctata , Cooperia pectinata, Cooperia spatulata, Cooperia curticei, Ostertagia ostertagi, Teladorsagia circumcincta , Trichostrongylus axei, Nematodirus spathiger , and Trichuris ovis. Twenty lambs presented cysts of Taenia hydatigena in the liver and mesentery. One lamb presented Coenurus cerebralis, the larval stage of Taenia multiceps, in the brain. In conclusion, sheep from pasture shared with cattle presented a high diversity of nematode species. H. contortus and H. placei co-infection occur with consequent hybridization.

Resumo A ocorrência de infecções helmínticas foi avaliada em ovinos que compartilhavam pastagem com bovinos. Em 2015 e em 2016, cordeiros machos foram adquiridos em Santana do Livramento, Rio Grande do Sul, para serem terminados em sistema de lavoura - pecuária (ILP). Em cada ano, 12 cordeiros que tinham maior contagem de ovos nas fezes foram abatidos para recuperação dos vermes. Haemonchus contortus e Trichostrongylus colubriformis foram as principais espécies registradas. H. contortus apresentou intensidade média de 1159 e 257 vermes em 2015 e 2016, respectivamente. T. colubriformis apresentou intensidade média de 4149 e 2427 parasitas em 2015 e 2016, respectivamente. De 127 machos de Haemonchus spp. analisados por "Polymerase Chain Reaction" (PCR), 125 foram identificados como H. contortus, um como Haemonchus placei e um como híbrido. Cooperia punctata, Cooperia pectinata, Cooperia spatulata, Cooperia curticei, Ostertagia ostertagi, Teladorsagia circumcincta , Trichostrongylus axei, Nematodirus spathiger e Trichuris ovis foram as outras espécies de nematódeos registradas. Vinte cordeiros apresentaram cistos de Taenia hydatigena no mesentério e no fígado. Um cordeiro apresentou no cérebro Coenurus cerebralis, o estágio larval de Taenia multiceps . Em conclusão, ovinos criados com bovinos apresentam grande diversidade de nematódeos. A co-infecção de H. contortus e H. placei favorece a produção de híbridos.

Helminth infections and hybridization between Haemonchus contortus and Haemonchus placei in sheep from Santana do Livramento, Brazil.

The occurrence and intensity of helminth infections were evaluated in sheep from pastures shared with cattle. In 2015 and 2016, young male sheep acquired in Santana do Livramento, Rio Grande do Sul, Brazil, were finished in integrated crop-livestock system. We selected the 12 sheep that showed the highest number of nematode eggs per gram of faeces to search for worms in the gastrointestinal tract. Haemonchus contortus and Trichostrongylus colubriformis were the major parasites. H. contortus presented mean intensities of 1,159 and 257 worms in 2015 and 2016, respectively. T. colubriformis displayed mean intensities of 4,149 and 2,427 worms in 2015 and 2016, respectively. Of the 127 male specimens of Haemonchus spp. analysed by Polymerase Chain Reaction (PCR), 125 were H. contortus, one Haemonchus placei and one hybrid. Other species detected were Cooperia punctata , Cooperia pectinata, Cooperia spatulata, Cooperia curticei, Ostertagia ostertagi, Teladorsagia circumcincta , Trichostrongylus axei, Nematodirus spathiger , and Trichuris ovis. Twenty lambs presented cysts of Taenia hydatigena in the liver and mesentery. One lamb presented Coenurus cerebralis, the larval stage of Taenia multiceps, in the brain. In conclusion, sheep from pasture shared with cattle presented a high diversity of nematode species. H. contortus and H. placei co-infection occur with consequent hybridization.

Immune humoral response of young lambs naturally infested by Oestrus ovis (Diptera: Oestridae).

Twenty-six newborn lambs were evaluated for 21 weeks, from birth to slaughter, to assess their plasma anti-Oestrus ovis immunoglobulin (IgG) using the ELISA technique. On the last day of sampling, all the lambs were slaughtered and O. ovis larvae were recovered, quantified and identified according to the larval stage. High levels of IgG were observed over the first three weeks of life, thus indicating that antibodies are transferred via colostrum from ewes to lambs. Afterwards, the antibody levels declined progressively until the lambs were 11 weeks of age and subsequently started to increase again when they were around 13 weeks of age, reaching the apex on the last week of sampling. All the lambs were parasitized with different larval stages of O. ovis, with an average of 39 larvae per lamb, and the intensity of the infestation ranged from 10 to 97 larvae. However, there was non-significant correlation coefficients between IgG levels and O. ovis larval burden (P > 0.05). In conclusion, although the lambs became infested with O. ovis at an early age, the larval burden was not associated with specific IgG levels.

Development of Haemonchus contortus resistance in sheep under suppressive or targeted selective treatment with monepantel.

This study examined the development of resistance to anthelmintics in Haemonchus contortus in lambs under suppressive or selective treatment regimens that included monepantel. Twenty Ile de France and 20 Santa Ines lambs were allocated to two anthelmintic treatment regimens, based on body weight and nematode faecal egg counts (FEC): targeted selective treatment (TST) or suppressive treatment, both with monepantel. Lambs of the TST group were treated individually when they presented with a packed cell volume (PCV) ≤20%. On 7 October 2016, the lambs were allocated to clean pastures, where they grazed in separated paddocks by group until late February 2017. The experimental area was contaminated with nematodes that were introduced with the experimental Ile de France and Santa Ines lambs, naturally infected with gastrointestinal nematodes. To maintain the grazing lambs in the suppressive treatment group and their pasture as free of worms as possible, these lambs were treated with anthelmintics before being allocated to their paddock and then were periodically treated with monepantel. However, the use of a suppressive treatment regimen that included monepantel over a period of 3 months resulted in the emergence of a population of resistant H. contortus. In the TST group, there was a rapid and progressive reduction in the efficacy of monepantel, which at the end of the experiment was only 76%. The Ile de France lambs were all treated one or more times during the experiment, whereas only two Santa Ines lambs in the TST required treatment. In conclusion, a population of H. contortus resistant to monepantel emerged quickly during the rainy season, even when sheep were submitted to selective treatment.

Gastrointestinal nematode infections in sheep raised in Botucatu, state of São Paulo, Brazil.

Gastrointestinal nematode infections were evaluated in sheep raised in Botucatu, state of São Paulo, Brazil between April 2008 and March 2011. Every month, two tracer lambs grazing with a flock of sheep were exposed to natural infection with gastrointestinal nematodes for 28 consecutive days. At the end of this period, the lambs were sacrificed for worm counts. Haemonchus contortus presented 100% of prevalence. The seasons exerted no significant influence on the mean intensity of H. contortus, which ranged from 315 worms in November 2010 to 2,5205 worms in January 2011. The prevalence of Trichostrongylus colubriformis was also 100%, with the lowest mean intensity (15 worms) recorded in February 2011 and the highest (9,760 worms) in October 2009. In the case of T. colubriformis, a significant correlation coefficient was found between worm counts vs. rainfall (r = -0.32; P <0.05). Three other nematodes species were found in tracer lambs, albeit in small numbers. Their prevalence and mean intensity (in parenthesis) were as follows: Oesophagostomum columbianum 28% (25.2), Cooperia curticei 7% (4.5) and Trichuris spp. 2% (1). In conclusion, the environmental conditions of the area proved to be highly favorable for the year-round transmission of H. contortus and T. colubriformis.

Gastrointestinal nematode infections in sheep raised in Botucatu, state of São Paulo, Brazil / Infecções por nematódeos gastrintestinais em ovinos criados em Botucatu, estado de São Paulo, Brasil

Gastrointestinal nematode infections were evaluated in sheep raised in Botucatu, state of São Paulo, Brazil between April 2008 and March 2011. Every month, two tracer lambs grazing with a flock of sheep were exposed to natural infection with gastrointestinal nematodes for 28 consecutive days. At the end of this period, the lambs were sacrificed for worm counts. Haemonchus contortus presented 100% of prevalence. The seasons exerted no significant influence on the mean intensity of H. contortus, which ranged from 315 worms in November 2010 to 2,5205 worms in January 2011. The prevalence of Trichostrongylus colubriformis was also 100%, with the lowest mean intensity (15 worms) recorded in February 2011 and the highest (9,760 worms) in October 2009. In the case of T. colubriformis, a significant correlation coefficient was found between worm counts vs. rainfall (r = −0.32; P <0.05). Three other nematodes species were found in tracer lambs, albeit in small numbers. Their prevalence and mean intensity (in parenthesis) were as follows: Oesophagostomum columbianum 28% (25.2), Cooperia curticei 7% (4.5) and Trichuris spp. 2% (1). In conclusion, the environmental conditions of the area proved to be highly favorable for the year-round transmission of H. contortus and T. colubriformis.

A ocorrência de infecções por nematódeos gastrintestinais foi avaliada de abril de 2008 até março de 2011em ovinos criados em Botucatu, estado de São Paulo. Todos os meses, dois cordeiros traçadores foram expostos à infecção natural por nematódeos gastrintestinais, durante 28 dias consecutivos, ao pastejar junto com um rebanho de ovelhas. Ao final desse período, os animais foram sacrificados para a identificação e quantificação dos helmintos. Haemonchus contortus apresentou prevalência de 100%. Não houve influência significativa das estações do ano na intensidade média de H. contortus, que variou de 315 vermes em novembro/2010 a 25.205 vermes em janeiro/2011. Trichostrongylus colubriformis também apresentou prevalência de 100% com a menor intensidade média (15 vermes) em fevereiro/2011 e a maior (9.760 vermes) em outubro/2009. No caso de T. colubriformis, houve correlação significativa entre as contagens de vermes x precipitação (r = −0,32; P <0,05). Outras três espécies de nematódeos foram encontradas nos cordeiros traçadores, no entanto em pequenas quantidades, com as seguintes prevalências e intensidades médias (entre parênteses): Oesophagostomum columbianum 28% (25,2), Cooperia curticei 7% (4,5) e Trichuris spp. 2 % (1). Em conclusão, as condições ambientais da área foram muito favoráveis durante todo o ano para a transmissão de H. contortus e T. colubriformis.

Epidemiology of Oestrus ovis (Diptera: Oestridae) in sheep in Botucatu, State of São Paulo / Epidemiologia de Oestrus ovis (Diptera: Oestridae) em ovinos em Botucatu, São Paulo

The seasonal factors that influence Oestrus ovis infestation in sheep were determined in Botucatu, State of São Paulo, Southwestern Brazil, from April 2008 to March 2011. Two tracer lambs were monthly exposed to natural infestation by O. ovis larvae for 28 consecutive days, by grazing with a sheep flock. Tracer animals were then euthanized and the larvae of O. ovis recovered from nasal and sinus cavities. Of the 72 tracer lambs, 50% were infested with O. ovis larvae and the mean intensity of infestation per head infested was 16.8 larvae, with an average of 7.8 L1, 5.3 L2 and 3.7 L3. O. ovis larvae were present during the four seasons of the year, but the mean larval burden was significantly higher during the spring and summer months, compared to winter (P < 0.05). The highest rate of larvae recovery coincided with mean temperatures between 20 °C and 25 °C and air relative humidity around 70%. Results suggest that evolution and development of O. ovis practically occurs throughout the entire year, with larval infestation especially frequent during the spring and summer months.(AU)

Os fatores sazonais que influenciam a infestação por larvas de Oestrus ovis, foram determinados no período de abril de 2008 a março de 2011, em ovinos criados em Botucatu, São Paulo, região Sudeste do Brasil. Mensalmente, dois cordeiros traçadores permaneceram em pastejo com um rebanho ovino durante 28 dias consecutivos, expostos à infestação natural por larvas de O. ovis. Em seguida, os cordeiros foram sacrificados, e as larvas de O. ovis recuperadas da cavidade nasal e seios frontais. Dos 72 cordeiros traçadores, 50% estavam infestados por larvas de O. ovis, com intensidade média de infestação de 16,8 larvas/cabeça infestada, com média de 7,8 L1, 5,3 L2 e 3,7 L3. As larvas de O. ovis foram recuperadas durante as quatro estações do ano, mas o número médio de larvas foi significativamente superior durante os meses de primavera e verão comparado aos meses de inverno (P < 0,05). A maior taxa de recuperação larval coincidiu com temperaturas médias entre 20 °C e 25 °C e umidade relativa do ar por volta de 70%. Os resultados sugerem que a evolução e desenvolvimento de O. ovis ocorre praticamente durante o ano inteiro, mas a infestação é mais frequente nos meses de primavera e verão.(AU)

Epidemiology of Oestrus ovis (Diptera: Oestridae) in sheep in Botucatu, State of São Paulo.

The seasonal factors that influence Oestrus ovis infestation in sheep were determined in Botucatu, State of São Paulo, Southwestern Brazil, from April 2008 to March 2011. Two tracer lambs were monthly exposed to natural infestation by O. ovis larvae for 28 consecutive days, by grazing with a sheep flock. Tracer animals were then euthanized and the larvae of O. ovis recovered from nasal and sinus cavities. Of the 72 tracer lambs, 50% were infested with O. ovis larvae and the mean intensity of infestation per head infested was 16.8 larvae, with an average of 7.8 L1, 5.3 L2 and 3.7 L3. O. ovis larvae were present during the four seasons of the year, but the mean larval burden was significantly higher during the spring and summer months, compared to winter (P < 0.05). The highest rate of larvae recovery coincided with mean temperatures between 20 °C and 25 °C and air relative humidity around 70%. Results suggest that evolution and development of O. ovis practically occurs throughout the entire year, with larval infestation especially frequent during the spring and summer months.

[Pasture contamination with infective larvae of gastrointestinal nematodes after grazing by sheep resistant or susceptible to parasitic infection]. / Contaminacao da pastagem com larvas infectantes de nematoides gastrintestinais apos o pastejo de ovelhas resistentes ou susceptiveis a verminose.

The degree of contamination of herbage with third stage larvae of gastrointestinal nematodes was evaluated in paddocks grazed by resistant or susceptible ewes. The trial occurred from November 23, 2007 to July 22, 2008. Initially, fecal egg counts (FEC) were performed with individual samples of 130 adult ewes of the Bergamacia breed. Of those animals, nine ewes with the highest FEC (susceptible group) and 10 with the lowest counts (resistant group) were selected and moved to separate paddocks. The resistant ewes presented lower FEC, higher values of packed cell volume, total plasma protein and blood eosinophils than the susceptible ewes. The weight was also higher in the resistant group. Haemonchus spp., Trichostrongylus spp. and Oesophagostomum spp. third stage larvae were recovered from pasture. In average, the amount of Haemonchus spp. and Trichostrongylus spp. third stage larvae in the pasture were 2.19 and 2.31 times, respectively, higher in the paddocks grazed by susceptible group in comparison with those grazed by the resistant animals. Therefore, the susceptible animals should be eliminated from the flock in order to reduce pasture contamination and optimize the prophylaxis of gastrointestinal nematode infections.

Contaminação da pastagem com larvas infectantes de nematoides gastrintestinais após o pastejo de ovelhas resistentes ou susceptíveis à verminose / Pasture contamination with infective larvae of gastrointestinal nematodes after grazing by sheep resistant or susceptible to parasitic infection

O grau de contaminação da pastagem por larvas de terceiro estágio (L3) de nematoides gastrintestinais foi avaliado em piquetes pastejados por ovelhas resistentes ou susceptíveis à verminose. O experimento foi realizado de 23 de novembro de 2007 a 22 de julho de 2008. Inicialmente, realizou-se a contagem de ovos por grama de fezes (OPG) de amostras individuais de 130 ovelhas adultas da raça Bergamácia. Dessas, foram selecionadas as nove ovelhas com contagens mais elevadas de OPG (susceptíveis) e as 10 com as menores contagens (resistentes). As ovelhas resistentes apresentaram menor contagem de OPG, maiores valores de volume globular, de proteína plasmática total e de eosinófilos sanguíneos, do que as ovelhas susceptíveis. O peso também foi maior no grupo resistente. Na pastagem, foram identificadas larvas de Haemonchus spp., Trichostrongylus spp. e Oesophagostomum spp. Em média, as quantidades de L3 de Haemonchus spp. e de Trichostrongylus spp., na pastagem, foram 2,19 e 2,31 vezes, respectivamente, maiores nos piquetes pastejados pelo grupo susceptível do que nos do grupo resistente. Portanto, os animais susceptíveis devem ser eliminados do rebanho a fim de reduzir a contaminação da pastagem e otimizar a profilaxia das infecções por nematoides gastrintestinais.

The degree of contamination of herbage with third stage larvae of gastrointestinal nematodes was evaluated in paddocks grazed by resistant or susceptible ewes. The trial occurred from November 23, 2007 to July 22, 2008. Initially, fecal egg counts (FEC) were performed with individual samples of 130 adult ewes of the Bergamacia breed. Of those animals, nine ewes with the highest FEC (susceptible group) and 10 with the lowest counts (resistant group) were selected and moved to separate paddocks. The resistant ewes presented lower FEC, higher values of packed cell volume, total plasma protein and blood eosinophils than the susceptible ewes. The weight was also higher in the resistant group. Haemonchus spp., Trichostrongylus spp. and Oesophagostomum spp. third stage larvae were recovered from pasture. In average, the amount of Haemonchus spp. and Trichostrongylus spp. third stage larvae in the pasture were 2.19 and 2.31 times, respectively, higher in the paddocks grazed by susceptible group in comparison with those grazed by the resistant animals. Therefore, the susceptible animals should be eliminated from the flock in order to reduce pasture contamination and optimize the prophylaxis of gastrointestinal nematode infections.