Prevalence of flukes (Fasciola hepatica and paramphistomids) in cattle in south-eastern Mexico.

The objective of this study was to determine the risk factors and prevalence of trematodes in south-eastern Mexico. The prevalence of trematodes was determined in 1010 bovines. The study was carried out from October 2018 (n=291) to December 2019 (n=719). Only in 2019 rumen and liver fluke eggs were differentiated. Faecal samples (n=311) were obtained from farms in southeast Mexico located in Tabasco, Chiapas and Campeche. In addition, the presence of flukes in liver and rumen from slaughtered cattle in abattoirs was recorded with a total of 408 samples. A logistic procedure was used to obtain the prevalence and the effect of main risk factors such as land physiography (flooded areas and hills), year, sex, animals' age and type of sample obtained (eggs in faeces and flukes). The general prevalence of flukes in cattle was 32.3 % in 2018 and 41.7 % in 2019. Prevalence of F. hepatica (liver fluke) was 18.6 % (134/719) and that of paramphistomids (rumen fluke) was 33.4 % (240/719). The infected cattle from the slaughterhouse indicated a lower prevalence of F. hepatica (1 %) and rumen fluke (26.7 %) than in farms detected by egg in faeces (41.8 % and 42.1 %, respectively). The physiographic zone was decisive in the presence of F. hepatica and rumen fluke, while sex did not represent a risk factor (P > 0.05). The environmental conditions of the Mexican southeast favour the presence of both liver and rumen fluke.

Optimum timing for assessing phenotypic resistance against gastrointestinal nematodes in Pelibuey ewes.

The objective was to identify the optimal stage of production to evaluate the resistance of Pelibuey ewes against gastrointestinal nematodes (GIN). Faecal egg count (FEC) was used to classify the ewes as resistant, sensible or intermediate against GIN. Forty-seven ewes were mating during 30 d. The gestation was verified by ultrasonography, and the breeding date was used to calculate the productive stages. Faeces were taken weekly to determine the FEC. Blood samples were taken to determine the packed cell volume (PCV), the peripheral eosinophils count (PEC), plasma protein concentration (PP), and Immunoglobulin A (IgA) against Haemonchus contortus. The body condition score (BCS) was recorded at each visit. Six moments during the study (early, mid and late gestation; early, mid and late lactation) were considered. The ewes were classified according to FEC (mean FEC ± three standard errors). The higher FEC occurred during all lactation stages than during early and mid-gestation stages (P<0.05). PCV, PP, and BCS during early gestation stage were higher than shown during the lactation stages (P<0.01). The PEC and IgA were higher during all lactation stages than early and mid-gestation stages (P<0.05). Concerning the type of birth, double births showed higher FEC than single birth (P<0.01). The highest values of accuracy (100 %) and concordance (Youden's J = 1.0) were found during early lactation. Therefore, it is concluded that the optimal stage of production to evaluate phenotypic resistance against GIN infections in Pelibuey ewes was during the early lactation.

Prevalence of Neospora caninum, Toxoplasma gondii and Brucella abortus in water buffalo (Bubalus bubalis): Climatic and environmental risk factors in eastern and southeast Mexico.

A total of 600 serum samples from five farms were collected and the geographic coordinates of each farm were georeferenced to establish two Köppen climate classes (wet tropical and tropical rainforest). Serum samples were examined by commercially available enzyme-linked immunosorbent assay (ELISA) kits to detect antibodies against N. caninum and T. gondii, while anti-B. abortus antibodies were analysed using the Rose Bengal test and ELISA kit. The overall estimated prevalence of N. caninum, T. gondii and B. abortus was 41.2%, 30.7% and 0.5%, respectively. The highest percentages of positive buffaloes with neosporosis and toxoplasmosis were found in the states of Tabasco (46.7%, wet tropical climate) and Veracruz (32.7%, tropical rainforest climate), respectively. Multivariate logistic regression showed that N. caninum seropositivity in buffalos was associated with the normalized difference vegetation index (NDVI) (OR: 1.068; 95% CI: 1.026-1.112; P = 0.001) and tropical climate regions (OR: 1.737; 95% CI: 1.112-2.712; P = 0.015). In addition, statistical analysis revealed that sex (OR: 1.737, 95% CI: 1.685-9.737; P = 0.002), NDVI (OR: 1.382; 95% CI: 1.095-1.746; P = 0.007) and rainfall (OR: 1.478; 95% CI: 1.110-1.967; P = 0.007) were significant risk factors for T. gondii infections. These results indicate that the potential impact of the risk factors was different for each disease in buffaloes, which may be useful for developing regionally adapted control strategies and preventive measures.

Identification of Somatic Proteins in Haemonchus Contortus Infective Larvae (L3) and Adults.

Haemonchus contortus is considered the most pathogenic nematode in sheep production systems based on grazing. Comparing infective larvae (L3) with adult parasites can lead to the identification of proteins that play an important role in parasite-host interactions. In this study, we report a list of H. contortus somatic proteins and made a comparative analysis of somatic proteins of L3 and adult worms. L3 and adult parasites were subjected to protein extraction and subsequently to peptide fractionation. Peptides were analysed by mass spectrometry and LC-MS/MS data analysis. Data analysis and search on SEQUEST and MASCOT against H. contortus from the WormBase ParaSite database resulted in the identification of 775 unique peptide sequences corresponding to 227 proteins at 1 % FDR. From these, 18 proteins were specific to L3 and 63 to adult parasites. The gene ontology (GO) enrichment analysis of the proteins specific to L3 and adult worms to gain insight into cellular components, molecular functions and biological processes that affect the parasite-host interaction showed some differences between the two parasite stages. The list of proteins found provides a database to identify target proteins that could be useful as biomarkers of the infection or in the generation of anthelmintic drugs that inhibit proteins essential for the establishment of the infection and the survival of adult parasites. They can also serve as new candidates for vaccine research.

Physiological, Immunological and Genetic Factors in the Resistance and Susceptibility to Gastrointestinal Nematodes of Sheep in the Peripartum Period: A Review.

Parasitic diseases of sheep involving gastrointestinal nematodes (GIN) are one of the main problems that affect fl ock productivity, especially during the peripartum period. Around lambing, the ewes are immunosuppressed and the nematode faecal egg count (FEC) increases at four weeks before lambing, reaching a peak between the fourth and sixth week postpartum and subsequently decreasing towards weaning. Prolactin has been credited with a suppressive effect on immune system, along with other hormones that intervene in metabolism, such as leptin, which has an important role in the activation of other hormones. Cortisol has also been included; this is stimulated by any stressful event and inhibits the proliferation of T-cells and alters the function of immunoglobulins. Another related hormone is pepsinogen, which is considered a marker of the integrity of the abomasum mucosa, as well as the albumin concentration that increases in the presence of a GIN infection. The humoral and cellular immune response, as well as inflammatory reactions, are the main mechanisms of action against GIN. Lymphocytes direct the effector mechanisms in a Th2 cell response, including interleukins (IL-4, IL-5, IL-9, IL-10) and transforming growth factor beta (TGF-ß) together with immunoglobulins (IgA, IgG, IgM and IgE), which prevent the invasion of pathogens. Eosinophils with a cytotoxic effect are indicators of a parasitic infection, with importance in the immune protection of infected individuals. The genetic selection of resistant individuals measured by FEC is dependent on the heritability (h2), which is moderately inheritable and highly repeatable. Effects that influence the resistance or susceptibility of sheep to GIN infections in the peripartum period are determined by the interaction of various factors, such as genotype or breed, nutrition, age, type of birth, season and production system, etc., which are studied in this review.

Mean corpuscular haemoglobin concentration as haematological marker to detect changes in red blood cells in sheep infected with Haemonchus contortus.

Haemonchus contortus is a nematode parasite that causes anaemia and affects the health of sheep. The mean corpuscular haemoglobin concentration (MCHC) is an excellent indicator to detect anaemia that could help to characterize resistant or susceptible lambs to gastrointestinal nematodes. The aim of this study was to evaluate the predictive value of MCHC in detecting changes in red blood cells and their relation to anaemia in lambs re-infected with H. contortus. An analysis of information was performed using 24 Pelibuey lambs previously infected in grazing, dewormed and experimentally re-infected with H. contortus. At the first haematological sampling (admission) the lambs were classified based on MCHC quartiles (Q). Subsequently, the lambs were housed for 56 days. Blood samples were taken every seven days to determine the haematological parameters using an impedance haematological instrument. Confidence limits were constructed with the records of the lambs that recovered their haematological parameters. Each quartile was analysed as a treatment in a repeated measures design over time. To know the optimal combination of sensitivity and specificity of MCHC to detect anaemia a curve of receiver operating characteristic (ROC) curve and the cut-off values were evaluated. In quartile 4 (Q4), lambs showed the highest faecal egg count (FEC, 764 eggs/g of faeces), mean corpuscular haemoglobin (17.0 pg) and MCHC (54.6 g/dL). This group also presented the lowest RBC values (5.8 × 106/mL), haematocrit (HCT, 18.3%), total plasma protein (5.7 g/dL), and HGB (9.7 g/dL). The optimal point of MCHC with ROC curve was 42.4 (sensitivity 88.2% and specificity 86.5%); the area under the curve was 0.91 (CI 95%, 0.86-0.96). These results are related to the haematological effects caused by H. contortus in susceptible lambs. In conclusion, the highest FEC and lower HCT in Q4 are important elements of the haematological damage caused by H. contortus and could identify susceptible lambs.

Evaluation of anthelmintic drugs against egg development of rumen flukes recovered from cattle raised in the humid tropics of Mexico.

Paramphistomosis is a parasitic disease endemic in ruminants nearly worldwide. In the present study, an in vitro screening of the main anthelmintics used in Mexico was carried out to determine the mean lethal dose for rumen fluke eggs from cattle in a humid, warm region. Rumen flukes were obtained from cattle slaughtered in the states of Tabasco and Chiapas in Mexico. Eggs were collected using a 37-µm sieve and quantified. Then, an in vitro incubation study was performed: 100 eggs were placed into the wells of polystyrene microtiter plates. Anthelmintic products were tested on the eggs at concentrations ranging from 0.0015 to 3.0 mg/ml for rafoxanide, 0.0025 to 10.20 mg/ml for nitroxinil and 0.0015 to 3 mg/ml for closantel to determine the median lethal dose (LD50) and maximum lethal dose (LD99). A control group (water) was included in each plate. Three different species of rumen flukes (Calicophoron brothriophoron, Calicophoron clavula and Paramphistomum cervi) belonging to five isolates were identified. Nitroxinil had the highest efficacy against rumen fluke eggs, with an LD50 of 0.11 to 65 µg/ml, whereas rafoxanide showed the lowest efficacy with an LD50 ranging from 500 to 1713 µg/ml. Closantel showed high variability in the LD50 among the different analysed isolates (17 to 122 µg/ml). The evaluated flukicidal drugs presented differential efficacy against the development of rumen fluke eggs. The efficacy of the drugs will vary depending on the geographical area of origin of the animals.

Artificial Haemonchus contortus infection as a strategy to induce protective immune response to natural infection in Pelibuey lambs.

The objective of this study was to evaluate the reduction in nematode faecal egg count (FEC) in Pelibuey lambs segregated as resistant (RES), susceptible (SUS) and intermediate (INT) to gastrointestinal nematodes. Twenty-nine weaned Pelibuey lambs, aged five months old, free of nematode infection, were used. Nine lambs were RES, six were SUS and 14 were INT lambs. The study consisted of two phases: in Phase 1 the lambs were infected experimentally with Haemonchus contortus. In Phase 2, the lambs were naturally infected by grazing. Faecal and blood samples were taken every week. The packed cell volume and total protein were quantified. The FEC value (FECmax) per lamb was recorded together with a natural reduction in FEC in the two phases. The data were analysed with a model of measures repeated over time. During Phase 1, the RES lambs showed the lowest FEC (1061 ± 1053) compared to the other groups (INT: 2385 ± 1794 eggs per gram of faeces (EPG); and SUS: 3958 ± 3037 EPG). However, in Phase 2 no significant differences (p > 0.05) were observed between the groups of lambs (RES: 275 ± 498 EPG; SUS: 504 ± 1036 EPG; and INT: 603 ± 1061 EPG). At the end of Phase 1, the FEC of RES lambs was naturally reduced by 75.5% in respect to FECmax (p < 0.05), and at the end of Phase 2 the reduction in FEC was 90% in respect to FECmax (p > 0.05); the same behaviour was observed in RES and SUS lambs. It is concluded that the artificial infection in the lambs induced a more rapid immune response in RES than SUS lambs, and all lambs developed high acquired resistance by continuous infection.

A multi-inverse approach for a holistic understanding of applied animal science systems.

Technological and mathematical advances have provided opportunities to investigate new approaches for the holistic quantification of complex biological systems. One objective of these approaches, including the multi-inverse deterministic approach proposed in this paper, is to deepen the understanding of biological systems through the structural development of a useful, best-fitted inverse mechanistic model. The objective of the present work was to evaluate the capacity of a deterministic approach, that is, the multi-inverse approach (MIA), to yield meaningful quantitative nutritional information. To this end, a case study addressing the effect of diet composition on sheep weight was performed using data from a previous experiment on saccharina (a sugarcane byproduct), and an inverse deterministic model (named Paracoa) was developed. The MIA successfully revealed an increase in the final weight of sheep with an increase in the percentage of corn in the diet. Although the soluble fraction also increased with increasing corn percentage, the effective nonsoluble degradation increased fourfold, indicating that the increased weight gain resulted from the nonsoluble substrate. A profile likelihood analysis showed that the potential best-fitted model had identifiable parameters, and that the parameter relationships were affected by the type of data, number of parameters and model structure. It is necessary to apply the MIA to larger and/or more complex datasets to obtain a clearer understanding of its potential.

In vitro nematocidal activity of commercial fatty acids and ß-sitosterol against Haemonchus contortus.

Haemonchus contortus is a haematophagous gastrointestinal nematode (GIN) that causes severe anaemia and even death in small ruminants, negatively impacting the economic viability of farms. Traditionally, this parasite has been controlled with chemical compounds; however, inadequate use of these types of products has favoured the emergence of anthelmintic resistance. Therefore, it is necessary to search for alternatives for GIN control. Previous studies have reported the anthelmintic activity of edible mushroom extracts against H. contortus. A recent study reported that a fraction constituted of different fatty acids and ß-sitosterol isolated from the basidiomata of the edible mushroom Pleurotus djamor ECS-123 has ovicidal and larvicidal activity against H. contortus. Thus, this study aimed to assess the anthelmintic activity of the pure molecules: pentadecanoic acid, palmitic acid, ß-sitosterol, stearic acid and linoleic acid. For this purpose, an egg-hatching inhibition test was carried out in which the compounds were evaluated individually and in combination at a final concentration of 20 mg mL-1. Furthermore, larval mortality was assessed using a combination of the five commercial compounds previously mentioned at different concentrations (1.25-20 mg mL-1). Palmitic acid and stearic acid, in some combinations, inhibited H. contortus egg hatching by 100%. On the other hand, in the larval mortality test, the combination of the five compounds showed dose-dependent behaviour, and 100% mortality was obtained 24 h post-incubation. Pure molecules and their combinations have anthelmintic-like activity against the eggs and larvae of H. contortus.

Influence of the physiological stage of Blackbelly sheep on immunological behaviour against gastrointestinal nematodes.

The influence of the physiological stage of a Blackbelly flock against natural infection by gastrointestinal parasitic nematodes (GIN) was investigated. Data on serum and saliva IgA levels and peripheral cellular immune response were recorded in 51 sheep for 6 months. The flock was divided based on their physiological stage as follows: a) pregnant ewes, b) lactating ewes, c) non-pregnant ewes, d) pre-weaning lambs, e) growing lambs and f) replacement sheep. Additionally, sheep were classified based on the parasite infection as stabled or grazing management system as follows: g) non-infected stabled sheep, h) infected and stabled sheep and i) infected grazing sheep. Faeces and blood samples were collected every fifteen days. The percentage of packed cell volume (PCV), plasma protein, (PP) and leucocyte differential counts (LDC) were recorded. Likewise, serum and saliva IgA levels were measured by the indirect ELISA technique. The number of GIN eggs excreted per g of faeces (EPG) was also determined using the McMaster technique. Data were analysed using the SAS program to identify fixed effect of physiological stages, infection time and interactions. Results showed high EPG values in stabled lactating ewes (2764) and in growing lambs (2950-4550 EPG). Pregnant ewes had higher PCV values (27%) than lactating ewes (23.5%). Infected lambs showed low PCV values (28.5%) and high PP values (5.9 g/dL) compared with non-infected lambs (31% PCV and 5.6 g/dL PP). The two most abundant GIN species identified were Haemonchus contortus (91%) and Trichostrongylus colubriformis (81%). Pregnant and non-pregnant ewes showed 29% and <20% of IgA values, respectively. High EPG, low IgA and eosinophils counts were observed until 180 days of age in infected lambs. In conclusion, the group of infected lactating ewes and lambs showed susceptibility to GIN than the other groups, including the pregnant ewes.

Immune response in Blackbelly lambs to Haemonchus contortus and Trichostrongylus colubriformis mixed infection in a hot and humid climate.

The main objective was to determine the immune response of Blackbelly lambs infected with Haemonchus contortus, Trichostrongylus colubriformis, or both species. In the first stage, an experimental challenge was performed with 200 infective larvae (L3)/kg body weight (BW) of H. contortus (Hct, n = 8). Additionally, eight animals were infected with 500 L3/kg BW of T. colubriformis (Tcl), eight lambs with the mixed infection at the same dose (HctTcl), and lambs without infection were the control group. In the second infection, the same lambs were reinfected with high doses: 400 L3/kg BW of Hct and 900 L3/kg BW of Tcl. The third stage consisted of a natural reinfection in grazing. Faecal samples were taken to determine the faecal egg count (FEC) of gastrointestinal nematodes (GINs). IgA was determined in serum and saliva by an indirect Enzyme-Linked Immuno Sorbent Assay (ELISA). The haematological parameters were recorded. With the first challenge, it was not possible to promote an immune response, whereas in the second infection, FEC were higher than 1000 eggs per gram of faeces (EPG) in infected animals. During the third stage, FECs were higher in lambs infected with Tcl. Eosinophils (EOS) did not show differences in the first and second stages, but during grazing the infected lambs had higher counts than the control group (P andlt; 0.05). IgA activity values showed the same trend, and lambs infected with HctTcl had a higher response (33% of the positive standard) than groups mono-infected (16.5% and 22.6%, respectively).

In vitro larvicidal and in vivo anthelmintic effects of Oxalis tetraphylla (Oxalidaceae) hydroalcoholic extract against Haemonchus contortus in lambs.

The in vitro larvicidal and in vivo anthelmintic effects of Oxalis tetraphylla hydroalcoholic extract (HE), against Haemonchus contortus in experimentally infected lambs, were assessed. We used a microtitration plate method, comprising the following two stages. Stage 1: 20 µl of water containing 200 sheathed H. contortus infective larvae (ShHcl) were deposited in every well of three series; then, the series 2 and 3 wells were treated with 80 µl 1% ivermectin and O. tetraphylla HE at 20 mg/ml, respectively. Stage 2: the same procedure was performed replacing the ShHcl with exsheathed larvae (ExShHcl). Evaluations were performed after 24 and 48 h. The total numbers of dead and live larvae were counted. A second experiment evaluated the reduction in nematode egg populations in the faeces of lambs treated orally with the O. tetraphylla HE. The 27 lambs used were divided into Groups 1, 2 and 3 (n = 9), which were administered water (positive control), levamisole 1 m (7.5 mg/kg body weight (BW), as a unique dose) and O. tetraphylla HE (20 mg/kg BW), respectively. The plant HE was administered daily for 8 days. The in vitro assay showed 80.9% and 86.5% larval mortality of ShHcl after 24 and 48 h, respectively, while the corresponding mortality values for ExShHcl were 97 and 99%, respectively. The in vivo assay showed variability in the eggs/gram of faeces (epg) values; however, at the end of the trial, the average reduction in the epg values of the O. tetraphylla HE group was 45.6% (P < 0.05). Oxalis tetraphylla HE contains compounds that belong to the flavonol group with anthelmintic activity.

Phenotypic expression of parasite susceptibility to Haemonchus contortus in Pelibuey sheep.

The objective of this study was to determine if the mean faecal egg count (FEC) from a first experimental Haemonchus contortus infection could be used to classify parasite-naïve Pelibuey hair sheep as parasite-resistant high responders and parasite-susceptible low responders. Twenty 6- to 7-month-old Pelibuey male sheep raised free of gastrointestinal nematodes were challenged with 7500±1412 H. contortus L3 larvae administrated orally on day 0 of the study. Faecal samples from each lamb were obtained daily from 21 to 41days post-infection (Stage I). Lambs received a second artificial infection of 8420±1545L3 larvae on day 42, with faecal samples collected from day 65 to day 78 (Stage III). The mean FEC for each lamb in Stage I was used to classify 8 lambs with means for FEC that were more than two standard errors (SE) below the overall mean (i.e., <4764 eggs per gram of feces; epg) as high responders. The remaining 12 lambs were classified as low responders. Means for FEC in Stage I were 2449±194 epg for high responders and 14,461±1044 epg for low responders (P<0.05). High responders also had lower FEC than low responders in Stage III (actual means of 650±220 vs. 5933±1990 epg; P<0.05 following log transformation to normalize the FEC distribution). Lambs were then reclassified as high and low responders based on their mean FEC in Stage III. Fourteen lambs with means for FEC that were more than one standard error (SE) below the overall mean (i.e., below 1537 epg) were classified as high responders. The remaining six lambs were classified as low responders. Use of the Stage I responder class to predict the Stage III responder class resulted in an 83.3% sensitivity but only a 50% specificity. The positive predictive value was 41.7% and the negative predictive value was 87.5%. The poor positive predictive value was caused by 5 animals with high FEC in Stage I, but low FEC in Stage III. The first infection thus identified most high-responder lambs, but a second infection may improve accuracy by separating lambs with an intermediate level of resistance from truly susceptible lambs. This protocol now requires additional validation under more practical conditions involving natural parasite infections and larger lamb numbers.

Comparing the phenotypic susceptibility of Pelibuey and Katahdin female lambs against natural gastrointestinal nematode infections under hot humid tropical conditions.

This study compared the phenotypic susceptibility of Pelibuey and Katahdin female lambs against gastrointestinal nematodes (GINs) under grazing conditions in the hot humid tropics of Mexico. The study was performed during the rainy season (August to October, 2014). It included 27 Pelibuey and 12 Katahdin female lambs from 6 months of age and live weight of 21.0 ± 3.7 and 23.3 ± 3.6 kg, respectively. Lambs were reared free of GIN infection before the study. The study lasted 91 days. Animals were weighed and sampled (blood and feces) on days 0 and 28 and every 7 days onwards. Fecal samples were obtained to determine fecal eggs of GIN per gram (EPG), and blood samples were used to determine the packed cell volume (PCV), the peripheral eosinophil counts (PECs), and optical densities (ODs) for IgA. The EPG counts were significantly lower for Pelibuey lambs compared to Katahdin throughout the study (P < 0.001). Similarly, Pelibuey lambs had higher mean PCV (P < 0.01) and PEC (P < 0.05) than Katahdin lambs during the study. The total weight gain and OD for IgA were similar between breeds (P > 0.05). Negative associations (P < 0.05) between EPG and PCV or PEC were moderate to strong for the lambs of both breeds. No association was found between EPG and IgA. In conclusion, Pelibuey lambs showed phenotypic evidence of higher resistance to natural GIN infections compared to Katahdin lambs sharing the same grazing conditions in the hot humid tropics. The most accurate phenotypic markers to identify a difference in susceptibility were EPG and PEC.

Cytokine and antioxidant gene profiles from peripheral blood mononuclear cells of Pelibuey lambs after Haemonchus contortus infection.

The expression profiles of cytokines and antioxidant genes were determined from an experimental infection with H. contortus in Pelibuey lambs. The infection was followed for 34 days (d) to determine the number of eggs per gram (epg) and the packed cell volume (PCV). Differential white cell counts and expression profile estimations of IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, IL-13, FCεR1A, GPX and SOD1 were determined at 0 hour, 4 hours, 2 days and 14 days post-infection (PI) in infected and control groups. Comparison of the fold change between 0 and 4-hours, 4-hours and 2-days and 2- and 14-days periods was performed. Significant differences (P<.05) between epg (>2000) and PCV (>30%) were determined after 21 days and were also observed with regard to monocyte and lymphocyte cells after 2 and 7 days PI. At 0 hour and 14 days PI, the GPX and IL-2 genes showed a 0.37- and 0.49-fold decrease in expression, respectively. In contrast, upregulation was observed at 4 hours of IL-8 (2.58) and FCεR1A (2.71), at 2 days for IL-4 (2.14) and IL-8 (4.02) and at 14 days for IL-2 (0.41), IL-10 (2.35) and FCεR1A (2.28). The comparison between the intervals of infection showed high expression values against H. contortus infection in Pelibuey sheep after the 2nd period of PI involving a dichotomy T cells.

Gastrointestinal nematode populations with multiple anthelmintic resistance in sheep farms from the hot humid tropics of Mexico.

This study evaluated the status of anthelmintic resistance against the three available classes of commercial drugs in seven sheep farms in the hot humid tropics of Mexico. Drug classes included benzimidazole (BZ), ivermectin (IVM) and levamisole (LV). Respective faecal egg count reduction tests (FECRT) were performed in each farm. Faecal samples were obtained from the rectum of >100 sheep in each farm. Adult sheep shedding >150 eggs per gram of faeces (EPG) were included. In each farm, animals were allotted to one of four groups with similar mean EPG: Control Group (untreated), BZ group (albendazole sulfoxide 5mg/kg LW), IVM group (ivermectin, 0.2mg/kg LW) and LEV group (levamisole 7.5mg/kg LW). Drugs were administered subcutaneously. A second faecal sampling was performed on the same animals of each farm 14days post-treatment. The GIN genera obtained from faecal cultures were identified for each group in different farms. Percentage faecal egg count reduction (%R) and 95% confidence intervals were estimated using the RESO© software. A questionnaire was applied to farm owners to describe anthelmintic management practices. All sheep farms had GIN populations with multiple resistance to the three anthelmintic classes tested. The %R ranged from 0 to 48% for BZ, 29 to 82% for IVM and 1 to 88% for LEV. Haemonchus spp. and Trichostongylus spp. were found in all treated groups of the study farms. Resistant Oesophagostomum spp. larvae (BZ or IVM) were found in respective farms. Treatment practices in study farms included frequent mass treatment every two months with extra treatments applied individually in the presence of clinical signs. Drug dosage used visual estimation of body weight rather than the exact weight of each animal. Quarantine anthelmintic treatment of incoming stock was used but efficacy was not confirmed.

Influence of gender on carcass yield of twin lambs Blackbelly x Pelibuey at 56 days of age / Influência do gênero no rendimento de carcaça em cordeiros gêmeos Blackbelly x Pelibuey aos 56 días de idade

The aim of this study was to determine the influence of gender on pre-weaning growth, yield and weight of primal cuts of the carcass of Blackbelly x Pelibuey lambs. 16 twin lambs were used. The lamb gender was the fixed factor. The variables evaluated were: body weight at birth and at weaning, average daily weight gain, weight and yield of carcass and primal cuts: neck, arm, thorax, abdomen and leg. Gender did not affect (P>0.05) body weight at birth. However, the pre-weaning average daily weight gain and body weight at weaning were affected (P<0.05) by the gender. Hot carcass yield and weight and primal cuts were not affected (P>0.05) by the gender of the lamb. Nevertheless, the area of the Longissimus dorsi muscle and cavity fat were different between males and females (P<0.05) 11.5±0.73cm2 and 198±0.05 g vs 9.3±0.73cm2 and 282±0.05g, respectively. In conclusion, in twin lambs Blackbelly x Pelibuey males had greater average daily weight gain and body weight at weaning than females. Carcass yield and weight and primal cuts were not affected by the gender of the lamb. However, males had greater area of the L. dorsi muscle than females and these in turn had a greater amount of cavity fat than males.(AU)

Objetivou-se determinar a influência do gênero no crescimento pré-desmame, no rendimento e no peso dos cortes primários de carcaça de cordeiros Blackbelly x Pelibuey. Utilizaram-se 16 cordeiros gêmeos. Os dados foram analisados em um desenho completamente ao acaso, em que o gênero dos corderos foi o fator fixo. As variáveis avaliadas foram: peso vivo ao nascimento e ao desmame, ganho diário de peso, peso e rendimento de carcaças e dos cortes primários: pescoço, braço, tórax, abdômen e perna. O gênero não afetou (P>0,05) o peso vivo ao nascimento. No entanto, o ganho diário de peso e o peso vivo ao desmame foram afetados, sendo esses valores superiores nos machos (P<0,05). O peso e o rendimento das carcaças quentes e dos cortes primários não foram afetados (P>0,05) pelo gênero do cordeiro. Entretanto, a área do músculo Longissimus dorsi e a gordura cavitária foram diferentes entre machos e fêmeas (P<0,05): 11.5±0.73cm2 e 198±0.05g vs. 9.3±0.73cm2 e 282±0.05g, respectivamente. Em conclusão, nos cordeiros gêmeos Blackbelly x Pelibuey, os machos tiveram maior ganho diário de peso e maior peso vivo ao desmame do que as fêmeas. O peso e o rendimento da carcaça bem como os cortes primários não foram afetados pelo gênero do cordeiro. Todavia, os machos tiveram maior área do músculo L. dorsi que as fêmeas e estas tiveram maior quantidade de gordura cavitária que os machos.(AU)

Susceptibility of hair sheep ewes to nematode parasitism during pregnancy and lactation in a selective anthelmintic treatment scheme under tropical conditions.

The objective was to determine the influence of year, season and age of hair sheep ewes on their susceptibility to gastrointestinal nematodes during pregnancy and lactation and to record the number of treatments within a selective anthelmintic (AH) treatment programme. A trial was performed with 46 grazing ewes kept in hot humid tropical conditions. Data included: average daily weight gain (ADG, kg), packed cell volume (PCV, %) and nematode eggs per gram of faeces (EPG) obtained during 2 years (2009 and 2011-2012). Ewes reaching 1000 EPG were treated with AH. Irrespective of year, season and age, ewes were more susceptible to GIN during lactation (higher EPG, lower PCV and net weight loss) and less susceptible during gestation (lower EPG, higher PCV and net weight gain). As a result, 24.4% of the ewes were left untreated during lactation, while 63.0% of the ewes needed no AH treatment during pregnancy. Even under the hot humid tropical conditions of the farm, the individual EPG helped to maintain a considerable proportion of animals without an AH treatments within the flock.

Desarrollo de rssistencia a nematodos gastrointstinales en ovinos de pelo desaafiados con diferentes niveles de infección / Develoment of reesistance to gastrointstinal nematode in hair sheep cchallenged with different levels of ineection

Se utilizaron 24 corderos Katahdin x Pelibuey, distribuidos al azar en cuatro grupos desafiados con los siguientes tratamientos: a) 25 larvas infectantes (L3) de nematodos gastrointestinales (NGI) por kg de peso vivo (PV); b) 50 L3 PV, c) 100 L3 PV y el grupo testigo (0 larvas). El experimento se dividió en tres etapas: 1) infección experimental y estabulación de corderos, 2) reinfección en pastoreo y 3) estabulación. En cada etapa se determinó el número de huevos de nematodos por gramo de heces (HPG), el peso vivo (PV) y el volumen celular aglomerado (VCA). El análisis se realizó con medidas repetidas en el tiempo. Los corderos infectados con 100 L3 tuvieron mayor HPG (1.642 ± 1.183) que los infectados con 50 L3 (1.140 ± 1.313 HPG) y los de 25 L3 (458 ± 371 HPG). Con 50 L3 los corderos tuvieron el menor VCA (23,7 ± 4,8%). Con 100 L3 se observó menor VCA que el grupo testigo y el de 25 L3 (26,2 ± 3,9; 28,0 ± 4,1 y 27,3 ± 4,2 %, respectivamente). Las ganancias de peso se redujeron respecto al testigo en un 22% en los de 25 larvas, 60% en los de 50 larvas y 61% en los de 100 larvas. El grupo infectado con 100 larvas obtuvo, durante la segunda etapa, el menor HPG (2.033 ± 2.553 HPG), un incremento del VCA (27,8%) y mayor ganancia de peso (3,7 kg) que los otros grupos, por lo que se concluye que con la dosis de 100 L3 se obtienen menores conteos fecales de huevos de NGI, mayor VCA y mejor ganancia de peso bajo condiciones de reinfección en pastoreo.

24 Katahdin x Pelibuey male lambs were used. The lambs were random in four groups with the following treatments: a) 25 infective larvae (L3) of gastrointestinal nematodes (GIN) per kg of body weight (BW), b) 50 L3 BW, c) 100 L3 BW and the control group (0 L3). The experiment was divided into three stages: 1) Experimental infection in stabling, 2) grazing infection and 3) housed lambs. At each stage were determined the number of nematode eggs per gram of feces (EPG), body weight and packed cell volume (PCV). The data analysis was performed using a repeated measures model in time. The lambs infected with 100 L3 had higher EPG (1642 ± 1183) in comparison with the treatment of 50 L3 (1140 ± 1313 EPG) and 25 L3 (458 ± 371 EPG). With 50 L3 the lambs had the lowest PCV (23.7 ± 4.8%). With the application of 100 L3 also had lower PCV than control group and 25 L3 (26.2 ± 3.9, 28.0 ± 4.1 and 27.3 ± 4.2%, respectively). It was observed a decrease in weight gain of all infected groups compared to the control group, by 22% in lambs with 25 larvae, 60% in the 50 larvae and 61% in animals of 100 larvae. During the second stage, the group infected with 100 larvae there was a reduction of EPG (2033 ± 2553 EPG), an increase in PCV (27.8%) and increased kg (3.7 kg) with respect to other infected for this reason was concluding that lambs receiving 100 L3 had lowest nematode faecal egg count, highest PCV and gain daily weight during the grazing reinfection.