Factors associated with ELISA scores for paratuberculosis in an Angus-Brahman multibreed herd of beef cattle

Cow and calf genetic and environmental factors were evaluated for their association with ELISA scores for paratuberculosis in a multibreed population of beef cattle. The ELISA scores are a measure of the presence or absence of antibodies against Mycobacterium avium subsp. paratuberculosis in bovine serum. The linear mixed-model analysis used 352 ELISA scores from 238 cows: 51 Angus (A); 34 Brahman (B); 41 (3/4 A 1/4 B); 45 (1/2 A 1/2 B); 34 (1/4 A 3/4 B); and 33 Brangus (5/8 A 3/8 B). Cows were assumed to be unrelated. Year affected (P < 0.001) ELISA scores, but age of cow did not, which was expected to be significant because of the chronic progressive nature of this disease. Important regressions on fixed effects associated with cows were 1) a positive estimate of cow B breed effect (0.59 +/- 0.24; P < 0.017), indicating an upward trend of ELISA scores toward 100% B cows; 2) a negative estimate for weight change from before calving (late November) to the date of the blood sample in May (-0.0062 +/- 0.0019 score/kg; P < 0.002), indicating that poorer maintenance of cow weights was associated with higher ELISA scores; and 3) a positive estimate for days in lactation of cow on the date of the blood sample (0.0086 +/- 0.0034 score/d; P < 0.021), indicating the production of larger amounts of antibodies against Mycobacterium avium subsp. paratuberculosis as lactation progressed. Relevant regressions on fixed effects associated with calves were 1) calf birth weight (-0.022 +/- 0.010 score/kg; P < 0.035), and 2) calf gain from birth to the date of the cow blood sample (-0.0092 +/- 0.0027 score/kg; P < 0.001). These estimates indicate that cows that produced lighter calves at birth and/or calves with slower preweaning growth tended to have greater ELISA scores. Although the sensitivity (percentage of infected animals detected) of ELISA was only 50%, these results suggest that subclinical paratuberculosis may be negatively affecting cows and their offspring. Factors identified as associated with ELISA scores could help producers with culling decisions related to paratuberculosis control and eradication in beef cattle.     

Preliminary investigation of a humoral and cell-mediated immunity ratio for diagnosis of paratuberculosis in beef cattle

One thousand three hundred and twenty-four adult beef cattle were tested for paratuberculosis using 2 antibody enzyme-linked immunosorbent assays (ELISA), an interferon-gamma (INF-γ) ELISA, and radiometric bacterial culture of feces from 5 populations. Two populations of cattle (n = 226) had data available to calculate a ratio of humoral to cell-mediated immunity based on results from one antibody test and the INF-γ ELISA. Latent class analysis was used to estimate accuracy of the 4 paratuberculosis assays within a Bayesian framework. Determination of test accuracy and paratuberculosis prevalence in the latent class analysis allowed for estimation of predictive value positive (PVP) functions. The estimated PVP functions were used to iteratively assign paratuberculosis status to sampled cattle. Accuracy of the immunity ratio, an antibody ELISA, and the INF-γ ELISA were determined for multiple cutoffs based on probabilistically assigned paratuberculosis status. Area under the receiver-operating characteristic (ROC) curves (95% probability interval) were estimated as 0.78 (0.66, 0.89), 0.81 (0.68, 0.92), and 0.59 (0.47, 0.71) for the immunity ratio, antibody ELISA, and INF-γ ELISA, respectively. The Youden index (sensitivity + specificity − 1) peaked at immunity ratios of 0.5 (J = 0.48) and 1.0 (J = 0.46). Sensitivity and specificity (95% probability interval) at an immunity ratio cutoff of 0.5 were 0.65 (0.44, 0.85) and 0.83 (0.78, 0.88), respectively. Sensitivity and specificity (95% probability interval) at the 1.0 cutoff were 0.55 (0.33, 0.77) and 0.91 (0.87, 0.95), respectively. An immunity ratio could be used to diagnosis paratuberculosis in beef cattle but requires further investigation.     

Bayesian mixture models for within-herd prevalence estimates of bovine paratuberculosis based on a continuous ELISA response

Diagnostic inference by use of assays such as ELISA is usually done by dichotomizing the optical density (OD)-values based on a predetermined cut-off. For paratuberculosis, a slowly developing infection in cattle and other ruminants, it is known that laboratory factors as well as animal specific covariates influence the OD-value, but while laboratory factors are adjusted for, the animal specific covariates are seldom utilized when establishing cut-offs. Furthermore, when dichotomizing an OD-value, information is lost. Considering the poor diagnostic performance of ELISAs for diagnosis of paratuberculosis, a framework for utilizing the continuous OD-values as well as known coavariates could be useful in addition to the traditional approaches, e.g. for estimating within-herd prevalences.

The objective of this study was to develop a Bayesian mixture model with two components describing the continuous OD response of infected and non-infected cows, while adjusting for known covariates. Based on this model, four different within-herd prevalence indicators were considered: the mean prevalence in the herd; the age adjusted prevalence of the herd for better between-herd comparisons; the rank of the age adjusted prevalence to better compare across time; and a threshold-based prevalence to describe differences between herds. For comparison, the within-herd prevalence and associated rank using a traditional dichotomization approach based on a single cut-off for an OD corrected for laboratory variation was estimated in a Bayesian model with priors for sensitivity and specificity.

The models were applied to the OD-values of a milk ELISA using samples from all lactating cows in 100 Danish dairy herds in three sampling rounds 13 months apart. The results of the comparison showed that including covariates in the mixture model reduced the uncertainty of the prevalence estimates compared to the cut-off based estimates. This allowed a more informative ranking of the herds where low ranking and high ranking herds were easier to identify.     

Association between IGF-I, IGF-IR and GHRH gene polymorphisms and growth and carcass traits in beef cattle

Molecular biology techniques are of help in genetic improvement since they permit the identification, mapping and analysis of polymorphisms of genes encoding proteins that act on metabolic pathways involved in economically interesting traits. The somatotrophic axis, which essentially consists of growth hormone releasing hormone (GHRH), growth hormone (GH), insulin-like growth factors I and II (IGF-I and IGF-II), and their associated binding proteins and receptors (GHRHR, GHR, IGF-IR and IGF-IIR), plays a key role in the metabolism and physiology of mammalian growth. The objectives of the present study were to estimate the allele and genotype frequencies of the IGF-I/SnaBI, IGF-IR/TaqI and GHRH/HaeIII gene polymorphisms in different genetic groups of beef cattle and to determine associations between these polymorphisms and growth and carcass traits. For this purpose, genotyping was performed on 79 Nellore animals, 30 Canchim (5/8 Charolais+3/8 Zebu) animals and 275 crossbred cattle originating from the crosses of Simmental (n=30) and Angus (n=245) sires with Nellore females. In the association studies, traits of interest were analyzed using the GLM procedure of SAS and least square means of the genotypes were compared by the Tukey test. Associations of IGF-I/SnaBI genotypes with body weight and subcutaneous backfat were significant (p<0.05), and nearly significant for longissimus dorsi area (p=0.06), with the BB genotype being favorable compared to the AB genotype. No significant associations were observed between this polymorphism and weight gain or carcass yield (P>0.05). The IGF-IR/TaqI and GHRH/HaeIII polymorphisms showed no association with production traits.     

Antimicrobial activity of gallium nitrate against Mycobacterium avium subsp. paratuberculosis in neonatal calves

Background: Mycobacterium avium subsp. paratuberculosis (MAP), the agent of Johne's disease in cattle, is a facultative intracellular bacterium that is dependent on ferric iron for its survival and replication. Gallium (Ga), a trivalent semimetal that shares many similarities with ferric iron and functions as an iron mimic has been shown to have in vitro antimicrobial activity against several microorganisms, including MAP. Objectives: (1) To investigate the antimicrobial activity of Ga in calves experimentally infected with MAP; and (2) to monitor for potential adverse effects of Ga on calf health. Animals: Twelve Holstein calves. Methods: Randomized blind controlled experiment. Beginning at 10 days of age (study day 1), the experimental calves (n = 6) were treated with 20 mg/kg gallium nitrate daily for 45 days. On study days 4 and 5, all calves were challenged with a PO dose of a live field strain MAP. Treated calves were monitored daily for adverse effects. Calves were euthanized on study day 100, and 29 tissue samples and 1 fecal sample were collected from each calf. Samples were cultured for MAP by MGIT liquid culture system, Herrold's Egg Yolk Medium culture, or both. Results: No adverse effects were observed in the treated calves. Treatment was associated with a significant reduction in MAP tissue burden when compared with control calves (P = .017). Conclusions and Clinical Relevance: Chemoprophylactic treatment of calves with Ga before and during the period of high susceptibility decreased MAP tissue colonization in experimentally infected neonatal calves.     

肉牛生长性状和肉质性状全基因组关联分析的研究进展

全基因组关联分析(genome-wide association studies,GWAS)是研究家畜复杂经济性状和疾病遗传变异的有效方法,GWAS的核心是挖掘遗传变异与目标表型性状间的关系.随着牛全基因组测序工作完成,海量单核苷酸多态性(single nucleotide polymorphism,SNP)位点被标记...     

Evaluation of Ziehl–Neelsen stained faecal smear and ELISA as tools for surveillance of clinical paratuberculosis in cattle in the Netherlands

Testing cattle suspected of clinical paratuberculosis is an important element of surveillance of paratuberculosis. The aim of this study was to evaluate the diagnostic-test characteristics of microscopic examination of Ziehl–Neelsen stained faecal smears for acid-fast Mycobacteria (ZN-test) and serum-ELISA in cattle suspected of clinical paratuberculosis in the Netherlands.Results of all samples submitted for ZN-test and serum-ELISA between April 2003 and April 2006 to our laboratory were retrieved. Results from cattle for which both tests were performed were analysed using two Bayesian latent-class models for evaluation of diagnostic tests in two populations without a gold standard, assuming (a) conditional independence of tests, or (b) conditional dependence of tests in both infected and non-infected cattle. Sampled cattle were divided into two populations in different ways using four known risk factors for clinical paratuberculosis: region, soil type, clinical signs, and age.For 892 cattle suspected of clinical paratuberculosis, both ZN-test and serum-ELISA results were retrieved: 250 ZN-positive and ELISA-positive, 12 ZN-positive and ELISA-negative, 260 ZN-negative and ELISA-positive, and 370 ZN-negative and ELISA-negative cattle.With priors based on the available literature, the posterior estimates of sensitivity, specificity, and positive and negative predictive values of the ELISA were always higher than those of the ZN-test. Furthermore, lower limits of the 95% credibility intervals of the posterior positive predictive values of the ELISA were ≥99.7%, and of the negative predictive values of the ELISA ≥56.4%.We conclude that the ELISA is preferred to the ZN-test to confirm the presumptive diagnosis of clinical paratuberculosis in the Netherlands. Little diagnostic information can be gained by performing the ZN-test in addition to the ELISA.     

Tissue predilection sites and effect of dose on Mycobacterium avium subs. paratuberculosis organism recovery in a short-term bovine experimental oral infection model

The objective of this study was to develop a short-term experimental infection model for Mycobacterium avium subsp. paratuberculosis (MAP) in cattle, using small oral doses of organisms. Specifically, the effect of dose size was evaluated, as well as specific tissue predilection sites for recovery of MAP. Oral doses as low as 1.5 x 10(6) CFU reliably produced infection that could be detected 3 weeks following infection. Detection of infection required culture of multiple intestinal samples (jejunum and ileum) for MAP. Histological examination did not permit detection at this early stage. Results from this study suggest intestinal mucosa, rather than tonsil, as the primary portal of entry for MAP. The experimental infection model described here is useful for studying the early effects of preventive and therapeutic interventions for paratuberculosis in cattle.     

Detection of Mycobacterium avium subsp. paratuberculosis in faeces using different procedures of pre-treatment for real-time PCR in comparison to culture

One of the most relevant aspects in the diagnosis of paratuberculosis (Johne’s disease) in cattle is the availability of a method for the rapid and sensitive detection of Mycobacterium avium subsp. paratuberculosis (MAP) in order to facilitate the prompt removal of pathogen-shedding animals from a herd. To meet this requirement, methods for pre-treatment of bovine faecal samples and subsequent extraction of DNA for detection of MAP by real-time PCR were compared with MAP culture results. A total of 116 bovine faecal samples that showed weak (64.7%), moderate (18.1%) or strong (17.2%) growth of MAP on solid HEY medium were investigated.For PCR, supernatants, sediments or bacterial pellets were obtained from faecal samples by pre-treatment before extraction of MAP DNA based on silica membranes or magnetic particles. Samples then were tested by MAP IS900 and ISMav2 real-time PCR with an analytical sensitivity of 6 and 28 genome equivalents (GE) per mL, respectively.The best results were obtained by including a microfiltration step in the sample pre-treatment in combination with silica membrane-based mini-columns or magnetic particles for DNA extraction. This approach enhanced the detection rate of MAP in IS900 real-time PCR from 58.6% to 84.5% using silica membrane mini-columns and from 61.2% to 64.7% using magnetic particles.     

Estimation of additive, maternal and non-additive genetic effects of preweaning growth traits in a multibreed beef cattle project

Data from purebred and crossbred calves, consisting of Afrikaner (AF), Charolais (CH), Simmental (ST) and Hereford and Aberdeen Angus combined (HA), were analyzed to estimate breed additive effects, breed maternal effects, average individual heterosis and average maternal heterosis. The traits studied were birthweight (BW), weaning weight (WW) and preweaning average daily gain (ADG) (kg). A multiple regression procedure was used for the estimation of these genetic effects and for predictions for breed crosses that were not included in the data set. Crosses containing higher proportions of CH or ST were heavier at birth and weaning than the other crosses and purebreds. The direct effects of BW were negative and significant (P < 0.05), except that of the CH, which was the highest. The regression coefficients were ?24.87, ?18.16, ?22.80 and ?27.02 for AF, CH, ST and HA, respectively. The maternal effects were not significant. Both average individual and average maternal heterosis regression coefficients were also not significant for BW. Regression coefficients of both direct and maternal effects for WW were not significant and were characterized by large standard errors. Average individual heterosis and average maternal heterosis regression coefficients were, however, significant (P < 0.01) and the values were 5.34 and 2.19, respectively. A similar pattern was observed for ADG, except for the regression coefficients of the maternal effects, which were significant, with larger estimates for AF and ST reflecting their superior mothering ability. The values were 0.01, 0.13, 0.13, 0.03; ?0.82, ?0.85, ?0.85, ?0.81; 0.03 and 0.01 for direct effects and maternal effects of AF, CH, ST and HA; and average individual heterosis and average maternal heterosis, respectively. Means and standard errors of purebreds and their F₁ crosses not included in the dataset were predicted.     

Evaluation of estimated genetic merit for carcass weight in beef cattle: Live weights, feed intake, body measurements, skeletal and muscular scores, and carcass characteristics

Genetic merit for growth rate, expressed as expected progeny difference for carcass weight (EPD_CWT), is available for dairy and beef sires used in Ireland. The once predominantly Friesian (FR) dairy herd has experienced significant introgression of Holstein (HO) genes over the past two decades, and cross-breeding of dairy cows, not required to produce herd replacements, with beef bulls is common. The objective of this study was to compare growth rate, feed intake, live animal measurements and slaughter traits of progeny of Holstein–Friesian dairy cows and bulls of two contrasting maturity beef breeds namely Aberdeen Angus (AA) and Belgian Blue (BB), each selected for either high (H) or low (L) estimated genetic merit for carcass weight. Two dairy strains (FR and HO) were also included giving six genetic groups in total. A total of 170 male progeny from spring-calving cows were artificially reared indoors and subsequently managed together at pasture until the end of their second grazing season when they were assigned to one of two mean slaughter weights (i) 560 kg (Light) or (ii) 620 kg (Heavy). Daily feed intake was recorded during the first winter and during finishing. Body measurements were recorded four times during the animals' life, and linear scoring was carried out at 9 months of age and again at slaughter. Carcasses were graded for conformation and fatness (15 point scale). Slaughter and carcass weights per day of age for AAH, AAL, BBH, BBL, FR and HO were 782, 719, 795, 793, 804 and 783 (SE 12.9) g, and 415, 372, 438, 436, 413 and 401 (SE 5.8) g, respectively. Corresponding values for carcass weight, kill-out proportion, carcass conformation class (15 point scale) and carcass fat class (15 point scale) were 314, 283, 334, 333, 317 and 305 (SE 4.7) kg, 526, 518, 553, 550, 519 and 511 (SE 2.9) g/kg, 6.2, 5.4, 8.0, 7.9, 5.3 and 3.7 (SE 0.26), and 9.8, 9.3, 7.4, 7.2, 9.3 and 8.2 (SE 0.26). There were significant interactions between estimated genetic merit for carcass weight and beef breed with the differences between H and L mainly expressed for AA only. Feed intake differences between H and L animals were negligible and largely attributable to the differences in live weight. Following scaling for live weight, beef breeds of high estimated genetic merit for carcass weight had lower skeletal measurements, indicating greater compactness, with the effect more pronounced in AA. It is concluded that using beef sires of estimated high genetic merit for carcass weight on dairy cows increases growth rate and carcass weight of the progeny but the effect may not be similar for all breeds.     

Transmission parameters of Mycobacterium avium subspecies paratuberculosis infections in a dairy herd going through a control program

A Johne's disease control program, including stringent management practices and a test-and-cull program (whole-herd fecal-samples taken twice a year), was implemented on a medium-sized Pennsylvania dairy farm that was suffering losses from clinical Johne's disease. The data that emerged from the control program, combined with birthdates, culling dates, lactation information and pedigrees, yielded an extensive longitudinal dataset. The dataset was processed through SAS 9.1 for statistical analysis; herd-level disease dynamics and dam-to-daughter transmission parameters were calculated. After the implementation of the program in 1984, prevalence dropped dramatically from 60% to less than 20% in 1989. After an apparent prevalence peak (25%) in 1991 due to improved test sensitivity, prevalence maintained a plateau of 10% from 1996 to 2000. After the implementation of the program, 9.5% of the offspring from test-negative dams and 26.8% of the offspring from known-infected dams became infected with Mycobacterium avium subspecies paratuberculosis (Map) (χ² = 14.7; p = 0.0001). Calves born shortly following the calving of an infected dam and calves growing up with a future high shedder were more likely to be infected compared to calves without this risk profile. It was concluded that, after the implementation of the control program, the most important causes of infections of susceptible calves were their own dams or infected animals which had calved recently.     

Estimates of covariances between reproduction and growth in Australian beef cattle

Estimates of covariance components between scrotal circumference, serving capacity, days to calving, and yearling and final weight were obtained for Hereford, Angus, and Zebu cross cattle in temperate and tropical Australia. Analyses were carried out by REML employing a derivative-free algorithm and fitting bivariate animal models. Aspects of modeling and computational requirements related to the use of this method are discussed. Estimates of heritabilities agreed closely with those from univariate analyses, being low for female reproductive performance and moderate to high for male reproduction and growth. Estimates of genetic correlation between male and female fertility traits were low but favorable, being -.25, -.28, and -.41 between scrotal circumference and days to calving for Herefords, Angus, and Zebu crosses, respectively. Genetic correlations between male reproductive traits and weights ranged from .24 to .52 for the temperate breeds and were higher (.65 to .69) for Zebu crosses. Phenotypic correlations between scrotal circumference and weights were similar for all breeds, ranging from .32 to .47, whereas serving capacity and weights were phenotypically unrelated. Estimates of correlations between days to calving and weights were less consistent. Phenotypically, there was little association between the two traits. Genetic correlations for Zebu crosses were negative and low to moderate (-.36 to -.66) and estimates for Angus were close to zero.     

Evaluation of an absorbed ELISA and an agar-gel immuno-diffusion test for ovine paratuberculosis in sheep in Australia

The sensitivities and specificities of an absorbed enzyme-linked immunosorbent assay (ELISA) and an agar-gel immuno-diffusion (AGID) test for the detection of Johne’s disease in sheep were estimated using data from six known infected and 12 assumed uninfected sheep flocks. Sensitivities were estimated for all histologically positive sheep, as well as by histological lesion score, lesion type (paucibacillary or multibacillary) and sheep body-condition score, with ELISA sensitivities estimated at 95 and 99% specificity. Logistic-regression analysis was used to test for significant effects of lesion score and condition score, with flock included in the model as a random effect.

Estimated specificities were 95% (95% CI: 93.4, 95.6%) and 99% (98.4, 99.4%) for ELISA cut-point ratios of 2.4 and 3.6, respectively, and 100% (99.7, 100.0%) for the AGID. Estimated sensitivities for all infected sheep were 41.5% (35.0, 48.3%), 21.9% (16.6, 27.9%) and 24.6% (19.1, 30.7%) for ELISA cut-point ratios of 2.4 and 3.6 and for AGID, respectively. Sensitivities of all tests and cut-points varied significantly between flocks and between categories of lesion score and condition score. Sensitivity ranged from 25 to 73, 10 to 47 and 9.2 to 63% between flocks, for the ELISA with cut-points of 2.4 and 3.6, and for the AGID, respectively. Sensitivity was highest in thin sheep and in sheep with multibacillary lesions. The effects of lesion type and condition score on test sensitivity were significant in the logistic regressions for the AGID and ELISA at both cut-points and the flock effect was significant for the AGID but not for the ELISA at either cut-point.     

Effects of GHR gene polymorphisms on growth and carcass traits in Zebu and crossbred beef cattle

The growth hormone receptor (GHR) is the cell surface receptor for growth hormone (GH) and is required for GH to carry out its effects on target tissues. The objectives of the present study were to estimate the allele and genotype frequencies of the GHR/Alu I gene polymorphism located in the regulatory region in beef cattle belonging to different genetic groups and to determine associations between this polymorphism and growth and carcass traits. Genotyping was performed on 384 animals, including 79 Nellore (Zebu), 30 Canchim (5/8 Charolais + 3/8 Zebu), 30 Simmental × Nellore crossbred and 245 Angus × Nellore crossbred cattle. Alleles Alu I(+), Alu I(−) and Alu I(N)–null allele–were evidenced for the GHR/Alu I polymorphism and the frequency of the Alu I(N) allele was significantly higher than the frequency of the Alu I(+) and Alu I(−) alleles in all genetic groups. Genotype Alu I(N/N) of the GHR/Alu I predominated in Nellore animals, while the Alu I(N/+) and Alu I(N/−) predominated in the other genetic groups. In the association studies, traits of interest were analyzed using the General Linear Model (GLM) procedure of the SAS program and least squares means of the genotypes were compared by the Tukey test. Significant associations (P < 0.05) were observed between the Alu I(N/N) genotype of the GHR/Alu I polymorphism and lower weight gain and body weight at slaughter, although a confounding between genotypes and genetic groups may have occurred.     

Cumulative discounted expressions of dairy and beef traits in cattle production systems

Gene-flow methodology was used to calculate the cumulative discounted expressions (CDE) for annual/lactation, replacement heifer, cull cow, birth, yearling, and slaughter traits in alternative cattle production systems. Generic equations were presented and parameters representing dairy-beef production systems in Ireland and Brazil were inputted. Cumulative discounted expressions using input parameters from a hypothetical purebred dairy production system with poor cow longevity were also calculated. Cumulative discounted expressions were calculated assuming either an initial purebred or crossbred mating within each production system. Absolute and relative differences in CDE existed among trait categories across the three alternative production systems investigated. For example, the CDE of beef-related traits accruing from an initial purebred mating ranged from 0.42 to 0.75 CDE of an annual/lactation trait across the three contrasting systems investigated which differed in various input parameters. Such variation may alter the relative emphasis of traits on overall profitability thereby contributing to genotype by environment interactions. The results of this study highlight the necessity to consider auxiliary traits in sire selection over and above those representing the principal intended use of the sire. This was particularly so for integrated dairy-beef cattle production systems.     

Strategy for the detection and differentiation of Mycobacterium avium species in isolates and heavily infected tissues

The members of Mycobacterium avium species, comprising M. avium subsp. paratuberculosis, M. a. hominissuis, M. a. avium, M. a. silvaticum, are currently the most prevalent opportunistic pathogenic mycobacteria causing mycobacterial infection in animals and humans. The ability to distinguish between these subspecies is of relevance for proper diagnosis and control programmes of the diseases. The aim of this study was to design a fast and specific PCR strategy for the detection and differentiation of M. avium subspecies from the solid plate cultures for use in routine veterinary diagnosis. We have developed a multiplex PCR based on IS900, IS901, IS1245 and the dnaJ gene. This method allows the detection of M. a. paratuberculosis, M. a. hominissuis and M. a. avium/M. a. silvaticum in one PCR reaction and theoretically enables mixed infections of M. a. paratuberculosis and M. a. avium or M. a. paratuberculosis and M. a. hominissuis to be revealed. The sensitivity of this multiplex PCR is 10(3)CFU for each bacterial strain in one PCR reaction, which also enabled the use of this test directly for DNA isolated from the tissue of the heavily infected sheep.     

The grazing response of cattle to pasture contaminated with rabbit faeces and the implications for the transmission of paratuberculosis

Transmission of Mycobacterium avium subspecies paratuberculosis, the organism responsible for paratuberculosis (or Johne's disease) in ruminants, occurs through the faecal-oral route. As M. a. paratuberculosis has been isolated from rabbit faeces, cattle grazing rabbit faecal contaminated pasture may thus be at risk.A herd of 57 beef cattle was monitored on a farm in Perthshire, throughout the 1999 'grazing year', to investigate whether the cattle avoided rabbit faecal contaminated pasture and thus the potential for disease transmission. Grazing was measured every two days over eight rotations by sward heights on 40 marked treatment plots (0.5 m x 0.5 m) to which 0, 10, 50 and 250 rabbit faecal pellets were added. Cattle were also monitored by an active transponder system which enabled individual animals contacting two plots per field rotation (one control and one contaminated) to be recorded. During the monitored grazing year, grazing pressure was low with a net mean sward offtake of 18% of sward height per rotation. There were no significant differences between rabbit faecal treatments (0, 10, 50 and 250 pellets) with respect to the height or proportion of sward removed, or between the numbers of contacts made by cattle on contaminated and uncontaminated plots. Over 90% of all the cattle contacted contaminated plots, indicating that the potential for disease transmission was widespread among the herd.To our knowledge, this is the first reported instance of a lack of avoidance by grazing cattle towards swards contaminated with faeces, and implies that the potential for transmission of paratuberculosis from rabbit contaminated pasture is high.     

Prevalence of Mycobacterium avium subspecies paratuberculosis (MAP) infection in suspected diarrhoeic buffaloes and cattle reporting at Veterinary University in India

Murrah buffaloes, best breed for milk production are native of Haryana state. They contributes significantly to the farmer’s income, livelihood and food (milk and meat) security, in the semi-tropical regions of North India. Johne’s disease though endemic in the domestic livestock of the country, but reports are not available in the buffaloes suffering from morbidity due to progressive weakness and diarrhoea. We estimated the status of JD in diarrhoeic buffaloes and cattle reporting at Veterinary Clinical Complex of Lala Lajpat Rai University of Veterinary and Animal Sciences, Hisar, Haryana, India, using conventional, serological and PCR assays.141 buffaloes suffering from chronic diarrhoea were screened to estimate sero-prevalence of MAP and 50.0 % young and 53.52 % adult animals were positive. Of 14 cattle screened, none of the young and 66.6 % adult cows were positive. In buffaloes, 66.1 and 6.77 %, fecal samples were positive in microscopy and IS900 PCR, respectively. Sero-prevalence of JD was very high in diarrhoeic buffaloes and cattle from Haryana state of India.Buffaloes positive for Mycobacterium avium subspecies paratuberculosis (MAP) infection had reduced total leukocyte count and lymphocytes.     

Association between cattle herd Mycobacterium avium subsp. paratuberculosis (MAP) infection and infection of a hare population

Paratuberculosis has long been considered a disease of domestic and wild ruminants only. The known host range of Mycobacterium avium subsp. paratuberculosis (MAP) was recently extended to include non-ruminant wildlife species believed to be exposed to spillover of MAP from infected domestic cattle herds. The aim of the present study was to assess the association between cattle herd MAP infection pressure level and the infection level of a hare population in two dairy farms of southern Chile. Fifty hares from a herd A and 42 hares from herd B were captured and sampled for MAP culture. The results showed a statistically significant association between the cattle herds’ infection prevalence and the hare infection prevalence.