Reduction In Lesion Scores Research Articles

Positive assessment of an autogenous vaccine against pathogenic Escherichia coli in broiler breeders and their progeny in Morocco

Excessive use of antibiotics to control colibacillosis on poultry farms in Morocco contributes to the development of multiresistant avian pathogenic Escherichia coli. Autogenous vaccines are an alternative to antibiotic usage. The main goal of this study was to assess the efficacy of this approach to control recurrent outbreaks of colibacillosis in a large broiler production flow. A tetravalent autogenous vaccine (serotypes O78, O88, O91, and O185) was produced from multiresistant E. coli strains isolated from clinical lesions in breeding hens and used on two farms (65,000 breeding hens in total). On each farm, contemporaneous groups were included: groups vaccinated twice (12 and 18 weeks of age) and unvaccinated control groups. The performances of these flocks, as well as the performances of broilers hatched from these breeders (12 farms, over 600,000 broilers in total), were recorded. A significant reduction in lesion scores, mortality rate and a significant increase in the number of sellable day-old chicks were observed among vaccinated hens. In broilers, body weight at slaughter, lesion scores, feed conversion ratio, mortality, and condemnation rates were significantly improved. This is the first field observation of a lasting effect of breeder hen’s immunization with an autogenous vaccine against E. coli on their offspring.

Ocimum basilicum and Lagenaria siceraria Loaded Lignin Nanoparticles as Versatile Antioxidant, Immune Modulatory, Anti-Efflux, and Antimicrobial Agents for Combating Multidrug-Resistant Bacteria and Fungi.

Lignin nanoparticles emerged as a promising alternative for drug delivery systems owing to their biodegradability and bioactive properties. This study investigated the antimicrobial activity of the ethanolic extract of Ocimum basilicum-loaded lignin nanoparticles (OB-LNPs) and Lagenaria siceraria seed oil-loaded lignin nanoparticles (LS-LNPs) to find a solution for antimicrobial resistance. OB-LNPs and LS-LNPs were tested for their antimicrobial potential against Escherichia coli, Enterococcus faecalis, Klebsiella pneumoniae, Staphylococcus aureus, Salmonella enterica, Trichophyton mentagrophytes, Trichophyton rubrum, and Microsporum canis. OB-LNPs and LS-LNPs were further tested for their anti-efflux activity against ciprofloxacin-resistant Salmonella enterica strains and for treating Salmonella infection in a rat model. We also investigated the antifungal efficacy of OB-LNPs and LS-LNPs for treating T. rubrum infection in a guinea pig model. Both OB-LNPs and LS-LNPs showed strong antimicrobial potential against S. Typhimurium and T. rubrum infections. LS-LNPs showed antibacterial activity against Salmonella enterica species with a MIC range of 0.5-4 µg/mL and antifungal activity against T. rubrum with a MIC range of 0.125-1 µg/mL. OB-LNPs showed antibacterial activity against Salmonella enterica species with a MIC range of 0.5-2 µg/mL and antifungal activity against T. rubrum with a MIC range of 0.25-2 µg/mL. OB-LNPs and LS-LNPs downregulated the expression of ramA and acrB efflux pump genes (fold change values ranged from 0.2989 to 0.5434; 0.4601 to 0.4730 for ramA and 0.3842-0.6199; 0.5035-0.8351 for acrB). Oral administration of OB-LNPs and LS-LNPs in combination with ciprofloxacin had a significant effect on all blood parameters, as well as on liver and kidney function parameters. Oxidative stress mediators, total antioxidant capacity, and malondialdehyde were abolished by oral administration of OB-LNPs and LS-LNPs (0.5 mL/rat once daily for 5 days). Interferon-γ and tumor necrosis factor-α were also reduced in comparison with the positive control group and the ciprofloxacin-treated group. Histopathological examination of the liver and intestine of OB-LNPs and LS-LNPs-treated rats revealed an elevation in Salmonella clearance. Treatment of T. rubrum-infected guinea pigs with OB-LNPs and LS-LNPs topically in combination with itraconazole resulted in a reduction in lesion scores, microscopy, and culture results. In conclusion, OB-LNPs and LS-LNPs possess immunomodulatory and antioxidant potential and can be used as naturally derived nanoparticles for drug delivery and treatment of Salmonellosis and dermatophytosis infections.

Subconjunctival autologous muscle‐derived mesenchymal stem cell therapy: A novel, minimally invasive approach for treating equine immune‐mediated keratitis

AbstractObjectiveTo establish the safety of subconjunctival injections of autologous muscle‐derived mesenchymal stem cells (mdMSCs) in healthy horses and to evaluate their effect in four horses (six eyes) with severe chronic equine immune‐mediated keratitis (IMMK) that was unresponsive to medical treatments.MethodsMdMSCs were cultured from minimally invasive muscle biopsies. In the safety group, four healthy horses received two subconjunctival injections of 2.5 and 5 million cells, respectively, at 1‐month interval, to the same eye. Ocular side effects were monitored for 1 month following each injection. In the treatment group, six eyes received four to seven subconjunctival mdMSCs injections (2.5 or 5 million cells per injection) every 4 weeks, approximatively. Medical treatment was discontinued 1 week before and throughout the entire treatment period. A scoring system was used to assess the evolution of the ocular lesions.ResultsIn the safety group, all horses exhibited mild to moderate chemosis and conjunctival hyperemia at the injection site, lasting 24–48 h. In the treatment group, all eyes initially responded positively to therapy, with a reduction in lesion scores observed after the first injection. Four eyes achieved control of the lesions with repeated injections during the 9.2 months of follow‐up.ConclusionThe first subconjunctival injection of mdMSCs resulted in improvement of the ocular lesions. Repeated injections were found to be safe, minimally invasive and showed promise in managing refractory cases of equine IMMK. Further studies are warranted to demonstrate the long‐term benefits of these injections and to optimize the therapeutic protocol.

Distinct non-synonymous mutations in cytochrome b highly correlate with decoquinate resistance in apicomplexan parasite Eimeria tenella

BackgroundProtozoan parasites of the genus Eimeria are the causative agents of chicken coccidiosis. Parasite resistance to most anticoccidial drugs is one of the major challenges to controlling this disease. There is an urgent need for a molecular marker to monitor the emergence of resistance against anticoccidial drugs, such as decoquinate.MethodsWe developed decoquinate-resistant strains by successively exposing the Houghton (H) and Xinjiang (XJ) strains of E. tenella to incremental concentrations of this drug in chickens. Additionally, we isolated a decoquinate-resistant strain from the field. The resistance of these three strains was tested using the criteria of weight gain, relative oocyst production and reduction of lesion scores. Whole-genome sequencing was used to identify the non-synonymous mutations in coding genes that were highly associated with the decoquinate-resistant phenotype in the two laboratory-induced strains. Subsequently, we scrutinized the missense mutation in a field-resistant strain for verification. We also employed the AlphaFold and PyMOL systems to model the alterations in the binding affinity of the mutants toward the drug molecule.ResultsWe obtained two decoquinate-resistant (DecR) strains, DecR_H and XJ, originating from the original H and XJ strains, respectively, as well as a decoquinate-resistant E. tenella strain from the field (DecR_SC). These three strains displayed resistance to 120 mg/kg decoquinate administered through feed. Through whole-genome sequencing analysis, we identified the cytochrome b gene (cyt b; ETH2_MIT00100) as the sole mutated gene shared between the DecR_H and XJ strains and also detected this gene in the DecR_SC strain. Distinct non-synonymous mutations, namely Gln131Lys in DecR_H, Phe263Leu in DecR_XJ, and Phe283Leu in DecR_SC were observed in the three resistant strains. Notably, these mutations were located in the extracellular segments of cyt b, in close proximity to the ubiquinol oxidation site Qo. Drug molecular docking studies revealed that cyt b harboring these mutants exhibited varying degrees of reduced binding ability to decoquinate.ConclusionsOur findings emphasize the critical role of cyt b mutations in the development of decoquinate resistance in E. tenella. The strong correlation observed between cyt b mutant alleles and resistance indicates their potential as valuable molecular markers for the rapid detection of decoquinate resistance.Graphical abstract

Pathogenicity and drug resistance of the Eimeria tenella isolate from Yiwu, Zhejiang province, eastern China

Chicken coccidiosis can cause severe enteritis with high mortality, which causes serious economic losses to the global breeding industry each year. The most virulent species is Eimeria tenella (E. tenella), but the infectivity of different E. tenella varies among geographic strains. At present, there are no reports related to the pathogenicity and drug resistance of E. tenella in Yiwu, Zhejiang province, China. A total of 600 fecal samples were collected from 10 farms in Zhejiang province, the overall oocyst prevalence was 54.2% (325/600). The prevalence was significantly higher (P < 0.01) in chickens under 40 d (97.5%) than that in chickens between 60 and 85-days-old (40.5%) and chickens over 90-days-old (24.5%). E. tenella stain was isolated from fecal samples of chickens in Yiwu and the pathogenicity of this isolate was determined, and then we recorded the survival rate, bloody stool score, lesion score, average weight gain. The results showed that all of the chickens infected with 5×105 sporulated oocysts of E. tenella died after the seventh day of infection, the bloody stool score and average lesion score of chickens from group 1 (5×105), group 2 (5×104), group 3 (5×103) and group 4 (5×102) decreased successively; the average weight gain (g) and relative weight gain (%) increased successively; the weight gain of the low-dose E. tenella infection groups (5×103 and 5×102) were higher than the other 2 groups (5×105 and 5×104) (P < 0.05). Finally, The E. tenella isolate was tested for sensitivity to 6 anticoccidial drugs (sulfachloropyrazine sodium, amproline, toltrazuril, clopidol, salinomycin, and nicarbazine) using 4 indexes including anticoccidial index(ACI), percent of optimum anticoccidial activity (POAA), reduction of lesion scores (RLS), and relative oocyst production (ROP). The results showed that this isolate has developed severe resistance to drugs of salinomycin and nicarbazine, moderate resistance to amproline and clopidol, slight resistance to toltrazuril, while the E. tenella isolate performed more sensitive to sulfachloropyrazine sodium.

Trimetazidine, a metabolic modulator, attenuates silica-induced pulmonary fibrosis and decreases lactate levels and LDH activity in rats.

Pulmonary fibrosis has been recently linked to metabolic dysregulation. Silica-induced pulmonary fibrosis in rats was employed by the current study to explore the effects of trimetazidine (a metabolic modulator-antianginal drug; TMZ) on silica-induced pulmonary fibrosis. Pulmonary fibrosis was induced by intranasal instillation of silica (50 mg/100 µl/rat) in TMZ versus vehicle-treated rats. Body weights of rats, weights of lungs, and wet-to-dry lung weights were determined. Various parameters were also measured in serum, bronchoalveolar lavage fluid (BALF) in addition to lung tissue homogenates. Moreover, histopathological examination of sectioned lungs for lesion score and distribution and histochemical detection of myeloperoxidase (MPO) in lung tissues were also performed. No significant differences were observed in body weight gains, lung coefficients, lung weights, and wet-to-dry lung weight in silica versus control rats. Elevated lactate levels in serum and lung homogenates were significantly attenuated by TMZ. In addition, lactate dehydrogenase activity, transforming growth factor-β, and total proteins in BALF were significantly normalized with TMZ. Moreover, TMZ significantly increased reduced glutathione and adenosine triphosphate levels and decreased nitrate/nitrite and hydroxyproline content in lungs of silica-treated rats. Histopathological examination of lungs revealed more than 56% reduction in lesion score and distribution by TMZ. MPO expression in lungs of silica-treated rats was also significantly attenuated by TMZ. TMZ attenuates silica-induced pulmonary fibrosis, an effect that could be mediated by suppressing anaerobic glycolysis-induced excessive lactate production. Regulation of oxidative stress could also play a role in TMZ-promoted protective effects.

The effects of feed supplementing Akkemansia muciniphila on incidence, severity, and gut microbiota of necrotic enteritis in chickens

Akkermansia muciniphila (AM) is a mucin-degrading anaerobe, exerting beneficial effects on gut integrity improvement, inflammatory alleviation, and metabolic regulations in humans. Excess amounts of mucin and mucogenesis in the gut facilitate the development of necrotic enteritis (NE) in chickens. The study aimed to evaluate the effects of oral inoculation of AM on NE prevention and gut modulation in a NE-reproduced model coinfecting with Clostridium perfringens (CP) and Eimeria parasites. A total of 105 commercial 1-day-old broilers were randomly allocated into 5 groups, respectively challenged with Eimeria (Eimeria group), Eimeria and CP (Eimeria+CP group), Eimeria and CP with AM (Eimeria+CP+AM group), Eimeria and AM (Eimeria+AM group), and a placebo (Noninfected group). The treatment of AM exhibited a low degree of amelioration on NE severity. The application neither protected broilers from NE by decreasing NE-positive numbers nor reached a significant reduction in lesion scores in the small intestines. The development of NE reduced species diversity in jejunal microbiota; the pretreatments of AM exacerbated the consequence by losing species richness and promoted the similarity of the jejunal microbial community presented in the Eimeria+CP group. The participation of AM enhanced the increments of genera Clostridium sensu stricto 1 and Escherichia_Shigella and decreased the number of Lactobacillus. The significant variations of genera Clostridium sensu stricto 1 and Lactobacillus in jejunal microbiota were associated with NE development and promotion. In conclusion, oral inoculation of AM promoted the development of NE and modulated the jejunal microbiota favorable for CP overgrowth in broilers. The application of AM as a probiotic in broilers should be cautious on account of the effects to predispose NE.

Anticoccidial activity of &lt;i&gt;Khaya senegalensis&lt;/i&gt;, &lt;i&gt;Senna siamea&lt;/i&gt; and &lt;i&gt;Chamaecrista rotundifolia&lt;/i&gt; in chicken (&lt;i&gt;Gallus gallus&lt;/i&gt;)

Anticoccidial drug residues in poultry products, prejudicial to consumer health and resistance problem of some Eimeria strain to conventional drugs have led to the search of alternative ways of controlling coccidiosis. The aim of this study was to evaluate the anticoccidial activity of the extract of Khaya senegalensis, Chamaecrista rotundifolia, and Senna siamea in a completely randomized design. The study was carried out on 23 day-old male chicks (Gallus gallus) experimentally infected with 15 000 oocysts of Eimeria tenella and treated with the extract of these plants. There were five (5) experimental groups. Three (3) infected groups treated with leaf extract of Senna siamea, Chamaecrista rotundifolia and tree balk extract of Khaya senegalensis. The tow (2) remaining groups were the infected treated with amprolium a conventional anticoccidial drug and the infected untreated control. Body weight gain, feed efficiency, lesion score, proportion of bloody droppings, and excretion of coccidia oocysts were assessed during 14 days post infection. The results showed the effectiveness of the extract of Senna siamea leaves (cassia) and Khaya senegalensis bark, through the improvement of body weight gain and feed conversion ratio and the reduction of lesion scores and oocysts excretion. The oocysts excretion reduction rate was 80% for Senna siamea and Khaya senegalensis compared to the infected untreated control group. Senna siamea and Khaya senegalensis extract demonstrated an obvious anticoccidial effect in the current study. However, further investigations are needed to determine the appropriate doses, the best mode of the herbs utilization, preventive or curative, the best extraction method of active ingredient and the parts of the plants with better anticoccidial effect.© 2019 International Formulae Group. All rights reserved.Keywords: Khaya senegalensis, Chamaecrista rotundifolia, Senna siamea, coccidiosis, Eimeria tenailla, chicken

Impact of a Bacillus Direct-Fed Microbial on Growth Performance, Intestinal Barrier Integrity, Necrotic Enteritis Lesions, and Ileal Microbiota in Broiler Chickens Using a Laboratory Challenge Model.

Decreases in the use of antibiotics and anticoccidials in the poultry industry have risen the appearance of necrotic enteritis (NE). The purpose of this study was to evaluate the effect of a Bacillus direct-fed microbial (DFM) on growth performance, intestinal integrity, NE lesions and ileal microbiota using a previously established NE-challenged model. At day-of-hatch, chicks were randomly assigned to three different groups: Negative control (NC), Positive control (PC) challenged with Salmonella Typhimurium (day 1), Eimeria maxima (EM, day 13) and Clostridium perfringens (CP, day 18–19), and Bacillus-DFM group (DFM) challenged as the PC. Body weight (BW) and body weight gain (BWG) were measured weekly. Total feed intake (FI) and feed conversion ratio (FCR) were evaluated at day 21. Liver samples were collected to assess bacterial translocation and blood samples were used to measure superoxide dismutase (SOD) and fluorescein isothiocyanate-dextran (FITC-d). Intestinal contents were obtained for determination of total IgA and microbiota analysis. NE lesion scores (LS) were performed at day 21. Chickens consuming the DFM significantly improved BW and had a numerically more efficient FCR compared to PC at day 21. Additionally, there were no significant differences in FCR between the DFM group and NC. Furthermore, the DFM group showed significant reductions in LS, IgA and FITC-d levels compared to the PC. However, there were no significant differences in SOD between the groups. The microbiota analysis indicated that the phylum Proteobacteria was significantly reduced in the DFM group in comparison to PC. At the genus level, Clostridium, Turicibacter, Enterococcus, and Streptococcus were reduced, whereas, Lactobacillus and Bacillus were increased in the DFM group as compared to PC (p < 0.05). Likewise, the DFM significantly reduced CP as compared to PC. In contrary, no significant differences were observed in bacterial composition between NC vs. DFM. In addition, beta diversity showed significant differences in the microbial community structure between NC vs. PC, and PC vs. DFM. These results suggest that the dietary inclusion of a selected DFM could mitigate the complex negative impacts caused by NE possibly through mechanism(s) that might involve modulation of the gut microbiota.

Anticoccidial activity of novel triazine compounds in broiler chickens

The objective of present studies was to evaluate and compare the anticoccidial activity of triazine compounds in broiler chickens infected with E. tenella, E. necatrix, E. acervulina, E. maxima, and two field mixed Eimeria species. The anticoccidial efficacy was evaluated using the anticoccidial index (ACI). The results showed that Aminomizuril (AZL) and Ethanamizuril (EZL) were active metabolites of nitromezuril, which demonstrated excellent effectiveness against E. tenella, E. necatrix, E. acervulina, E. maxima, and the field Eimeria isolates in broiler chickens at a dosage of 10 mg/kg in feed. The anticoccidial activities of AZL and EZL at dose 10 mg/kg were roughly equivalent to the parent nitromezuril at a dosage of 3 mg/kg in feed. The decrease in metabolite anticoccidial activity is probably due to an increasing polarity of compounds in the metabolic processes. The sensitivity of two field Eimeria isolates to triazines EZL, diclazuril and toltrazuril was tested using 4 indices including anticoccidial index (ACI), percent of optimum anticoccidial activity (POAA), reduction of lesion scores (RLS) and relative oocysts production (ROP). Results showed that the sensitivity of EZL treatment against the two field Eimeria isolates were relatively superior to that of diclazuril and toltrazuril treatment. The field Eimeria isolates from Gansu Province was determined to be slightly, moderately and highly resistant to EZL, diclazuril and toltrazuril respectively. The field Eimeria isolates from Zhejiang Province was slightly, highly and slightly resistant to EZL, diclazuril and toltrazuril respectively. The results above indicated that the anticoccidial activity of metabolites was lower than that of the parent nitromezuril and there was partial cross-resistance among triazines EZL, diclazuril and toltrazuril. However the field Eimeria isolates had higher sensitive to EZL than the triazines diclazuril and toltrazuril. It was suggested that the site of C4 substituents of phenol of triazine anticoccidials may have important biological functions and the metabolite EZL would be a potential novel anticoccidial agent worthy of more attention.

Prevalence and drug resistance of avian Eimeria species in broiler chicken farms of Zhejiang province, China

In this study, coccidia were isolated and identified from 5 main poultry farms located in Zhejiang province, eastern China. The overall prevalence of Eimeria spp. was 30.7% (95 of 310). Five common species were observed: E. tenella, E. acervulina, E. maxima, E. necatrix, and E. mitis. Two isolates (HZ and QZ) were tested for sensitivity to 8 anticoccidial drugs using 4 indexes including anticoccidial index (ACI), percent of optimum anticoccidial activity (POAA), reduction of lesion scores (RLS), and relative oocyst production (ROP): sulfachloropyrazine, toltrazuril, diclazuril, sulfamonomethoxine/trimethoprim, and amprolium; sulfaquinoxaline/sulfadimethoxine, nicarbazin, and halofuginone. The results showed that the 2 isolates have developed various degrees of resistance to most of the tested drugs. The multi-resistance coccidia are a potential threat to local poultry farming. Rotation of anticoccidial drugs and shuttle programs are recommended to prevent further economic losses caused by coccidiosis.

Integrative pharmacokinetic–pharmacodynamic modeling and simulation of amenamevir (ASP2151) for treatment of recurrent genital herpes

Amenamevir is a novel drug that targets the viral helicase–primase complex. While dose-dependent efficacy had been observed in non-clinical studies, no clear dose dependence has been observed in humans. We therefore developed a pharmacokinetic/pharmacodynamic (PK/PD) model to explain this inconsistency between species and to clarify the immune-related healing of amenamevir in humans. The model consisted of a non-linear kinetic model for a virtual number of virus plaques as a built-in biomarker. Lesion score was defined as an endpoint of antiviral efficacy, and logit model analysis was applied to the ordered-categorical lesion score. The modeling results suggested the time course profiles of lesion score could be explained with the efficacy terms in the logit model, using change in number of virus plaques as an indicator of the effects of amenamevir and time elapsed as an indicator of the healing of the immune response. In humans, the PD effect was almost dose-independent, and immune-related healing may have been the driving force behind the reduction in lesion scores. Drug efficacy is occasionally masked in diseases healed by the immune response, such as genital herpes. The PK/PD model proposed in the present study must be useful for explanation the PK/PD relationship of such drugs.

Identification and characterization of a cathepsin-L-like peptidase in Eimeria tenella.

Avian coccidiosis, caused by Eimeria spp., is one of the major parasitic diseases in birds. Cysteine protease is a major virulence factor in parasitic protozoa, and it may be a suitable chemotherapeutic target and vaccine candidate molecule. A 100 amino acid (aa.) partial sequence of cathepsin L, which is a cysteine protease, was reported by Katrib et al. (Ac. No. CDJ41293) (2012). A 219 aa. sequence was reported by Reid et al. (Ac. No. AFV92863) (2013). However, the open reading frame (ORF) was not reported. In this study, a full sequence of a cathepsin-L-like peptidase in Eimeria tenella (EtcatL) was obtained and its biochemical characterizations and expression profiles were analyzed across different stages of the parasite's life cycle. Results showed that the EtcatL gene encodes a protein 470 aa. in length, with 47 and 49% identity to Toxoplasma gondii and Eimeria acervulina. Considering the close phylogenetic relationship, TgcatL (PDB. ID 3F75) was selected for use as a template for homology modeling with quality factors of 90.9. Gelatin SDS-PAGE showed it to exert protease activity at ≈38 and ≈26 kDa. Further analysis showed the kinetic parameters of the recombinant peptidase to be K m = 8.9 μM and V max = 5.7 RFU/s μM at pH 5.5 containing 10 mM dithiothreitol (DTT) in the reaction matrix, and the IC50 value of E64 was 65.32 ± 3.02 nM. The recombinant protein was active from 25 to 50 °C, with optimal activity at 42 °C. The RT-PCR and Western blot results showed it to be expressed mainly at the endogenous stages and the initial phase of the sporulation. The protective experiment showed that chickens immunized with 100 and 200 μg rEtcatL had reduction of weight loss values 48.7 and 57.9% those of infected controls, respectively. Their reduction of lesion scores (RLS) were 25.0 and 47.2% that of control chickens, and relative oocyst production (ROP) was 39.6 and 15.5% that of control chickens. These results indicate that the EtcatL can be used as an effective immunogen, and further studies are needed to enhance its potential as a vaccine candidate molecule.

Revaccination of cattle with bacille Calmette-Guérin two years after first vaccination when immunity has waned, boosted protection against challenge with Mycobacterium bovis.

In both humans and animals, controversy exists concerning the duration of protection induced by BCG vaccine against tuberculosis (TB) and whether revaccination enhances protection. A long-term study was undertaken to determine whether BCG-vaccinated calves would be protected against challenge with Mycobacterium bovis 2½ years after vaccination and to determine the effect of revaccination after 2 years. Seventy–nine calves were divided into five groups (n = 15–17 calves/group) with four of the groups vaccinated subcutaneously with 105 CFU of BCG Danish at 2–4 weeks of age and the fifth group serving as non-vaccinated controls. Three of the four BCG-vaccinated groups were revaccinated 2 years after the initial vaccination. One BCG-vaccinated group was revaccinated with BCG. A second group was vaccinated subcutaneously with a TB protein vaccine consisting of biopolyester particles (Biobeads) displaying two mycobacterial proteins, ESAT-6 and Antigen 85A, mixed with an adjuvant. A third group was vaccinated with TB proteins from M. bovis culture filtrate, mixed with an adjuvant. Twenty-three weeks after the BCG revaccination, all animals were challenged endotracheally with virulent M. bovis and a further 13 weeks later, animals were killed and necropsied to determine protection against TB. The BCG-vaccinated animals produced positive tuberculin caudal fold intradermal (15 of 62 animals) and IFN-γ TB test responses (six of 62 animals) at 6 months after vaccination, but not at subsequent time-points compared to the non-vaccinated animals. Calves receiving a single vaccination with BCG vaccine 2½ years prior to challenge were not protected against TB, while those revaccinated with BCG 2 years after the initial vaccination displayed significant reductions in lung and pulmonary lymph node lesion scores compared to the non-vaccinated animals. In contrast, no reduction in lesion scores was observed in the animals revaccinated with the TB protein vaccines with their immune responses biased towards induction of antibody.

Anticoccidial effects of a novel triazine nitromezuril in broiler chickens

The anticoccidial efficacy of 2-(3-methyl-4-(4-nitrophenoxy)phenyl)-1,2,4-triazine-3,5(2H,4H)-dione (nitromezuril, NZL), a novel triazine compound, was evaluated in three different studies under experimental conditions. The anticoccidial efficacy was chiefly evaluated using the anticoccidial index (ACI). The resistance level was determined by calculating ACI, percentage optimum anticoccidial activity (POAA), reduction in lesion scores (RLS) and relative oocyst production (ROP). In the dose determination study (study A), NZL was added to the diet at doses of 1, 2, 3, 4, 5 and 6mg/kg to test its efficacy against coccidiosis caused by Eimeria tenella. Groups treated with NZL 1mg/kg feed could observe the faecal dropping scores and caecal lesions. ACIs of NZL-treated groups reached 179–199. In the study on the anticoccidial efficacy of 3mg/kg NZL in the diet (study B), only a few faecal oocysts and slight lesions were observed. NZL significantly promoted weight gain (WG) and reduced lesion scores (LS) compared to controls receiving diclazuril (DZL) (P<0.05). ACIs of NZL-treated groups were 193, 192, 191 and 163 for E. tenella, Eimeria necatrix, Eimeria acervulina and Eimeria maxima, respectively, whereas those of DZL-treated groups were 185, 176, 176 and 148. In the cross-drug resistance study (study C), ACIs of NZL and toltrazuril (TZL)-treated groups ranged from 188 to 204, which were significantly higher than those of DZL-treated groups (P<0.05). NZL- and TZL-treated groups were sensitive to experimentally induced DZL-resistant E. tenella, whereas DZL-treated groups showed complete resistance. No cross-resistance was observed between DZL and NZL or TZL. Based on the abovementioned studies, it was concluded that diets containing 3mg/kg NZL had an excellent efficacy in preventing coccidiosis in broiler chickens. The activity of 3mg/kg NZL in the diet was equal or superior to that of 1mg/kg DZL. These results are of great significance for the future applications of NZL; however, its actual mechanism of action remains unknown. NZL is a potential novel anticoccidial agent suitable for further development.

A field evaluation of a footbathing solution for the control of digital dermatitis in cattle

Footbathing is one of the most commonly used methods for controlling digital dermatitis (DD). A farm-based trial was undertaken using six dairy herds involving over 600 cubicle-housed Holstein-Friesian cattle. Split footbaths (length 2.2m) were used to compare the efficacy of two dips, namely, a positive control (5% copper sulphate) and a non-heavy metal-based proprietary dip. The dips were used from early January 2009 for a minimum of 103 days, bathing twice a day for 3 consecutive days every week, using one footbath (three herds) or two in line (three herds). The lesions of DD on the hind feet of cattle were scored by borescope while the animals were being milked, on three occasions (at approximately days 0, 55 and 110) and then compared both directly and by calculating the change in severity from the previous examination (when possible). Data from the 408 cows that had their feet examined for lesions on all three occasions were analysed separately. A reduction in lesion score was seen for both footbath products, but feet bathed in 5% copper sulphate improved more (OR=1.6, CI: 1.14-2.32; P<0.01), and, irrespective of solution, there was a significantly greater improvement in those herds where two footbaths were used (OR=3.39, CI: 2.07-5.19; P<0.001). Lesion improvement over time also increased with lactation number (OR=1.13, CI: 1.02-1.25; P<0.05).

Low oral BCG doses fail to protect cattle against an experimental challenge with Mycobacterium bovis

Studies were undertaken to determine whether a dose of oral Mycobacterium bovis bacillus Calmette-Guérin (BCG) which did not induce skin test reactivity could protect cattle against bovine tuberculosis (TB). Groups of calves (n=9) were vaccinated by administering 10(8), 10(7) or 10(6) colony forming units (CFU) of BCG orally or 10(6)CFU subcutaneous (s.c.) BCG. A control group (n=10) was not vaccinated. All animals were challenged with M.bovis 18 weeks after vaccination and euthanized and necropsied at 16 weeks following challenge. Positive responses in the single cervical tuberculin skin test (severe interpretation) at 15 weeks post-vaccination were only observed in the s.c. BCG and 10(8)CFU oral BCG groups (four of nine animals/group). Following experimental challenge with M.bovis, both these BCG-vaccinated groups had significant reductions in lesion scores and bacterial counts whereas there was no protection in calves vaccinated with oral doses of 10(6) or 10(7)CFU of BCG. In conclusion, low oral doses of BCG did not induce skin test responses, IFN-γ responses or protection against TB, however, in the BCG vaccine groups where protection was observed, there was no correlation between protection and skin test responses or IFN-γ responses.

Mucosal immunization against ovine lentivirus using PEI–DNA complexes and modified vaccinia Ankara encoding the gag and/or env genes

Sheep were immunized against Visna/Maedi virus (VMV) gag and/or env genes via the nasopharynx-associated lymphoid tissue (NALT) and lung using polyethylenimine (PEI)–DNA complexes and modified vaccinia Ankara, and challenged with live virus via the lung. env immunization enhanced humoral responses prior to but not after VMV challenge. Systemic T cell proliferative and cytotoxic responses were generally low, with the responses following single gag gene immunization being significantly depressed after challenge. A transient reduction in provirus load in the blood early after challenge was observed following env immunization, whilst the gag gene either alone or in combination with env resulted in significantly elevated provirus loads in lung. However, despite this, a significant reduction in lesion score was observed in animals immunized with the single gag gene at post-mortem. Inclusion of IFN-γ in the immunization mixture in general had no significant effects. The results thus showed that protective effects against VMV-induced lesions can be induced following respiratory immunization with the single gag gene, though this was accompanied by an increased pulmonary provirus load.

Heritability of post-mixing aggressiveness in grower-stage pigs and its relationship with production traits

AbstractMixing of commercial pigs frequently leads to intense aggression. Considerable phenotypic variation exists between individuals and selection against aggressiveness may offer a long-term reduction in aggression without incurring additional costs to the primary producer. The genetic contribution to aggressiveness was quantified in this study using the number of skin lesions as an indicator of involvement in aggression. A sample of 1132 pigs were mixed at an average weight of 27·9 (s.d. 4·6) kg into 96 pens on a commercial sire line nucleus unit. Post-mixing aggressiveness of pigs was assessed using the lesion score (LS) approach. Growth rate, between 27·9 and 91·9 kg, and backfat depth at 91·9 kg were recorded for a subsample of 658 pigs. With a pedigree file of 1947 animals, a heritability of 0·22 was estimated for the LS trait. No significant genetic or phenotypic correlations were found between LS and growth rate or backfat depth, but standard errors of estimates were large. The response to selection, when all selection pressure was placed on the LS trait, was a 25% reduction in LS per generation. It is therefore technically possible to select for a reduced LS without substantially inhibiting genetic progress in growth rate or backfat depth through antagonistic genetic relationships.

Experimentally induced monensin-resistant Eimeria tenella and membrane fluidity of sporozoites

Two resistant lines of Eimeria tenella (H) to monensin were developed after 35 passages in chickens medicated with 100–125 ppm or 125–200 ppm monensin in the diet. Drug sensitivity of the induced lines to different level drugs were estimated with mean lesion scores (LS), mean oocyst productions (OP), percentage optimum anticoccidial activity (POAA), reduction of lesion scores (RLS), relative oocyst production (ROP), anticoccidial index (ACI) and global index (GI), respectively. Membrane fluidity of sporozoites of the sensitive line (i.e. the parent line, coded as MON-S (S)) and two resistant lines (coded as MON-R (S)-1 and MON-R (S)-2) with and without in vitro exposure to monensin were determined. Membrane fluidity of MON-R (S)-1 and MON-R (S)-2 were significantly lower than that of MON-S (S). In vitro exposure to monensin significantly increased membrane fluidity of MON-S (S), but had a much less effect on those of MON-R (S)-1 and MON-R (S)-2. Sporozoits of the MON-S (S)and MON-R (S)-2 with or without in vitro exposure to monensin were examined by SEM, and the sensitive sporozoites (MON-S (S)) appeared swollen and bulgy after treatment with monensin, while there was no obvious morphological deformation in the resistant sporozoites (MON-R (S)-2). The results suggest that the altered membrane fluidity in the membranes of E. tenella may be related to the decreased sensitivity to monensin.