Evaluation of the Johne's disease risk assessment and management plan on dairy farms in Ontario, Canada

Seroprevalence of Mycobacterium avium subsp. paratuberculosis in Swiss dairy herds and risk factors for a positive herd status and within-herd prevalence

Introduction

Bovine paratuberculosis (PTB) is a chronic enteric disease caused by Mycobacterium avium subsp. paratuberculosis (MAP). Control of PTB is important given its negative economic consequences and the potential zoonotic role of MAP in Crohn's disease in humans.

Methods

To determine the seroprevalence of MAP in Swiss dairy herds and to identify risk factors associated with seropositive herd status and high within-herd seroprevalence, 10,063 serum samples collected from cattle over 12 months of age in 171 Swiss dairy farms were analyzed using a commercial ELISA test. Eight herds were excluded due to non-interpretable ELISA results. Risk factors associated with seropositive herd status and high within-herd seroprevalence were investigated with regression models using results from a questionnaire on management practices possibly associated with the introduction or spread of MAP in the remaining 163 herds. Univariable logistic regression was performed, carrying forward for multivariable regression analysis when p < 0.2.

Results

The calculated between-herd true seroprevalence was 3.6% (95% CI, 0.96-8.4%). Due to the low within-herd seroprevalence, it was not possible to calculate the true seroprevalence at animal level; the apparent within-herd seroprevalence ranged from 2.3 to 5.5% with a median of 3.6% in nine positive farms. Herd size (p = 0.037) and the common grazing of lactating cows with cows from other herds (p = 0.014) were associated with seropositive herd status, while heifers sharing alpine pasture with dairy cattle from other herds were associated with a decreased probability of the herd to test seropositive (p = 0.042). Reliable identification of significant risk factors associated with MAP spread and high seroprevalence of PTB within seropositive herds was not possible due to low observed seroprevalence within herds and low sensitivity of the ELISA test.

Discussion

These results highlight the limitation of serology for MAP diagnosis in small herds with low infection prevalence.

Investigating Ontario dairy farmers motivations and barriers to the adoption of biosecurity and Johne's control practices

For the control of Johne's disease (JD), management practices to minimize disease transmission must be implemented and maintained. Once infected, animals will enter a latent phase and will typically only manifest clinical symptoms years later. As young calves are the main susceptible group on farm, the observed effects of management practices geared toward minimizing their exposure to infective material may not be realized until years later. This delayed feedback limits the sustained implementation of JD control practices. Although quantitative research methods have demonstrated changes to management practices as well as their association with changes to JD prevalence, dairy farmers can offer insights into the current challenges relating to JD implementation and control. Thus, this study aims to use qualitative methods and in-depth interviews (n = 20) with Ontario dairy farmers who had previously been engaged in a Johne's control program to explore their motivations and barriers to the implementation of JD control practices and general herd biosecurity. A thematic analysis using inductive coding was completed generated the following 4 overarching themes: (1) the hows and whys of Johne's control, (2) barriers to general herd biosecurity, (3) barriers to Johne's control, and (4) overcoming barriers. Farmers no longer believed JD was an issue on their farm. Johne's was low on their list of concerns due to little public discourse, absence of animals displaying clinical signs, and no financial support for diagnostic testing. Producers who were still actively engaged in JD control cited animal and human health as their primary motivations. Financial support, targeted education, and promoting engagement through discourse may help encourage producers to reconsider their participation in JD control. Government and industry collaboration with producers may help to develop more effective biosecurity and disease control programs.

Estimating the sensitivity and specificity of serum ELISA and pooled and individual fecal PCR for detecting Mycobacterium avium subspecies paratuberculosis in Canadian cow-calf herds using Bayesian latent class models

While Johne's disease (JD) is less common in beef than in dairy herds, consolidation is increasing transmission risk. Estimates of Mycobacterium avium spp. paratuberculosis (MAP) prevalence and test performance in cow-calf herds are needed to inform control programs. Objectives of this study included describing the prevalence of MAP in Canadian cow-calf herds and comparing the relative performance of a serum ELISA, pooled fecal PCR and individual fecal PCR using Bayesian latent class models, and to investigate factors associated with positive MAP tests. Blood and fecal samples (n = 3,171) were collected from 159 Canadian cow-calf herds. All samples were analyzed using serum ELISA and fecal PCR (pools of five samples) and a subset of 913 fecal samples were also tested with individual PCR. Based on latent class analysis, MAP prevalence was higher in eastern compared to western Canada for both animals {East, 3% [95% Credible Interval (CrI) 1-7%]; West, 1% [95% CrI 0.2-2%]} and herds [East, 15% (95% CrI 2-35%); West, 10% (95% CrI 1-26%), based on one or more positive results]. Sensitivity (Se) and specificity (Sp) for animal level individual PCR were 96% (95% CrI 80-100%) and 98% (95% CrI 96-100%), respectively followed by pooled PCR [Se = 54% (95% CrI 36-72%), Sp > 99.9% (95% CrI 99.8-100%)] and ELISA [Se = 36% (95% CrI 22-52%), Sp = 98% (95% CrI 96-99%)]. Based on 20 samples per herd, the herd level Se of ELISA was 79% (95% CrI 47-100%) (at least one positive sample) compared to 43% (95% CrI 14-94%) for pooled PCR. Herd-level Sp was 99% (95% CrI 96-100%) for pooled PCR and 90% (95% CrI 83-100%) for ELISA. Cows from herds with dairy cattle on farm and cows with symptoms of JD in the past 3 years were more likely to be MAP positive. Herds that had animals with JD symptoms in the previous 3 years and those with more breeding females were most likely to test positive for MAP. While serum ELISA can be effective for herd screening, PCR performed better for animal testing. Pooled PCR testing could be a less costly option; however, determining the most cost-effective approach will require further economic analysis.

Association of genetic variability in CD209 gene with bovine paratuberculosis disease: a case-control study in the Indian cattle population

This study aimed to explore the association of single nucleotide polymorphisms (SNPs) in CD209 gene with the occurrence of bovine paratuberculosis (PTB) disease caused by Mycobacterium avium subspecies paratuberculosis (MAP) in Indian cattle. A total of 213 animals were preliminarily selected on the basis of physical body condition score, which was then screened by a panel of diagnostic tests viz. Johnin, ELISA, fecal microscopy, and fecal culture, for the establishment of a case-control resource population. A total of four SNPs viz. rs208222804, rs211654540, rs208814257, and rs210748127 in CD209 gene were genotyped by PCR-RFLP. All SNPs, except rs210748127, were polymorphic in our population. Genotypic-phenotypic associations were assessed by the PROCLOGISTIC procedure of SAS 9.3. The SNP rs208814257 yielded three genotypes viz. CC, CG, and GG, which were significantly (p < 0.05) different in case as compared to the control population. The odds of CC and CG in comparison to GG genotype were 1.21 and 0.40, respectively. The CG genotype was significantly higher in control population, indicating that this genotype may provide resistance against PTB in our resource population. Upon validation in an independent, larger test population and following biological characterization, SNP rs208814257 can be incorporated in marker panel for selection of animals with greater resistance to MAP infection.

Johne's disease in Irish dairy herds: considerations for an effective national control programme

The Irish dairy industry has established a reputation for the production of safe and healthy dairy products and is seeking to further expand its export market for high value dairy products. To support its reputation, stakeholders aim to control Johne’s disease. To assist decision-makers determine the most appropriate design for an Irish programme, a narrative review of the scientific literature on the epidemiology of Johne’s disease, and selected control programmes throughout the world was undertaken. Two modelling studies specifically commissioned by Animal Health Ireland to assess testing methods used to demonstrate confidence of freedom in herds and to evaluate a range of possible surveillance strategies provided additional information. The majority of control programmes tend to be voluntary, because of the unique epidemiology of Johne’s disease and limited support for traditional regulatory approaches. While acknowledging that test performance and sub-clinical sero-negative shedders contributes to the spread of infection, a range of socio-political issues also exist that influence programme activities. The paper provides a rationale for the inclusion of a Veterinary Risk Assessment and Management Plan (VRAMP), including voluntary whole herd testing to identify infected herds and to support assurance-based trading through repeated rounds of negative testing, national surveillance for herd-level case-detection, and improved understanding of biosecurity management practices. Identification and promotion of drivers for industry and producer engagement in Ireland is likely to guide the future evolution of the Irish Johne’s Control Programme (IJCP) and further enhance its success. The provision of training, education and extension activities may encourage farmers to adopt relevant farm management practices and help them recognize that they are ultimately responsible for their herd’s health and biosecurity.

Paratuberculosis in dairy goat flocks from southern Spain: risk factors associated with seroprevalence

BACKGROUND

Paratuberculosis (PTB) is a chronic, enteric wasting disease of ruminants caused by Mycobacterium avium subspecies paratuberculosis (MAP), with a worldwide distribution. Andalusia, located in southern Spain, is one of the European regions with the highest goat census and the highest milk production; however, current data on the prevalence of MAP in this species are not available.

METHODS

A cross-sectional study was performed to determine the seroprevalence and risk factors associated with PTB in dairy goat flocks from southern Spain. A total of 3312 serum samples were collected from 48 flocks located in three different geographical areas. Health and productive parameters were surveyed during the visit to the herds.

RESULTS

A total of 511 goats were seropositive, with overall true seroprevalence of 22.54 per cent (95 per cent confidence interval (CI₉₅) 21.12-23.97). Of the goat herds, 87.50 per cent (CI₉₅78.14-96.98) were seropositive. The intraherd seroprevalence was 25.43±31.71, distributed as follows: 22 flocks with a seroprevalence under 10 per cent; 18 flocks between 10 per cent and 50 per cent; and eight flocks with a frequency over 50 per cent. Multivariate logistic regression showed significant association between PTB seropositivity and the following variables: intensive production system, lack of management by batches, inappropriate ventilation and seropositivity to c aprine a rthritis e ncephalitis v irus ( CAEV ).

CONCLUSIONS

The results indicate a widespread PTB infection in goat herds in southern Spain. Thus, control programmes must include management and sanitary measures to reduce the prevalence. Further experimental studies are necessary to determine the influence of CAEV-PTB coinfection on immune status.

Genetic association of polymorphisms in bovine TLR2 and TLR4 genes with Mycobacterium avium subspecies paratuberculosis infection in Indian cattle population

Toll like receptors (TLRs) are pattern recognition molecules involved in cellular recognition of Mycobacterium avium subspecies paratuberculosis (MAP), the infectious agent causing Paratuberculosis (PTB), a notified disease of domestic and wild ruminants. The present study was undertaken to investigate the presence of single nucleotide polymorphisms (SNPs) in TLR2 and TLR4 gene and to evaluate association of these SNPs with occurrence of PTB in Indian cattle. A total of 213 cattle, were subjected to multiple diagnostic tests viz. Johnin PPD, ELISA test (Indigenous and Parachek kit method), fecal microscopy and fecal culture for detection of MAP infection. Based on screening results 51 animals each were assigned to case and control population. Two SNPs viz. rs55617172, rs41830058 in TLR2 gene and two SNPs viz. rs8193046, rs8193060 in TLR4 gene and were genotyped by PCR-RFLP method. All SNPs were found to be polymorphic except rs41830058 in the case-control population. Both SNPs in TLR4 gene but none in TLR2 genes were significantly associated with the occurrence of PTB in our population. The genotypes in SNP rs8193046 and SNP rs8193060 were significantly (P < 0.01) different in case-control population. These findings suggest that SNPs rs8193046 and rs8193060 are likely a potential marker against MAP infection and a selection programme eliminating AG genotype for rs8193046 and CT genotype for rs8193060 might be beneficial in conferring resistance to MAP infection in Indian cattle population.

Incidence of fecal excretion of Mycobacterium avium subsp. paratuberculosis in dairy cows before and after the enrolment in the Québec voluntary program

Paratuberculosis is a chronic and contagious enteric disease of ruminants caused by Mycobacterium avium subsp. paratuberculosis (MAP). This disease of worldwide distribution is responsible for significant economic losses and the bacteria itself has been linked to human Crohn's disease. Paratuberculosis control programs focus on reducing MAP transmission by implementing better management practices that target infection routes. In Québec, a Voluntary Paratuberculosis Prevention and Control Program (QVPPCP) was launched in 2007. The objectives of this prospective cohort study were threefold. The first was to describe the changes in the incidence of fecal excretion of MAP in cows born before and after farm enrolment in the QVPPCP. The second was to estimate the impact of the risk of within-herd transmission of MAP (measured by the risk assessment score (RAS)) on the incidence of fecal excretion of MAP. And the third was to evaluate the impact of calf rearing practices on the incidence of fecal excretion of MAP. Eighteen MAP-positive herds were visited annually from 2011 to 2015. At each visit, individual fecal samples from all adult cows were collected. MAP was cultured using liquid media and an automated system. A risk assessment questionnaire was completed upon enrolment in the QVPPCP and at each visit. The RAS of the farm was attributed to each cow according to its birthdate. Cox proportional hazards models were used to estimate the hazard ratios (HR) for the exposure variables. Herd clustering was taken into account using robust standard errors. A total of 2158 cows were included (cohort born before n=919; cohort born after n=1239). The incidence and hazard of fecal excretion were significantly lower for the cohort-after than the cohort-before (incidence rate ratio=0.38; 95% CI: 0.18-0.78 and HR=0.48; 95% CI: 0.23-0.98). The HR of fecal excretion for cows exposed to a high RAS was 2.20 times (95% CI: 1.21-3.99) that of cows exposed to a low RAS. Poor calving cow hygiene (HR=3.41; 95% CI: 1.40-8.31) and contact between pre-weaned heifers and adult cows or their feces were significantly associated with an increased hazard of fecal excretion of MAP (HR=2.66; 95% CI: 1.08-6.56). Our results suggest that enrolment in the QVPPCP reduces the risk of MAP fecal excretion. They support the hypothesis that contact between calves and adult cows or their feces increases MAP transmission. The incidence results also suggest that MAP prevalence could be reduced to low levels regardless of initial MAP prevalence.

Viable Mycobacterium avium ssp. paratuberculosis isolated from calf milk replacer

When advising farmers on how to control Johne's disease in an infected herd, one of the main recommendations is to avoid feeding waste milk to calves and instead feed calf milk replacer (CMR). This advice is based on the assumption that CMR is free of viable Mycobacterium avium ssp. paratuberculosis (MAP) cells, an assumption that has not previously been challenged. We tested commercial CMR products (n = 83) obtained from dairy farms around the United States by the peptide-mediated magnetic separation (PMS)-phage assay, PMS followed by liquid culture (PMS-culture), and direct IS900 quantitative PCR (qPCR). Conventional microbiological analyses for total mesophilic bacterial counts, coliforms, Salmonella, coagulase-negative staphylococci, streptococci, nonhemolytic Corynebacterium spp., and Bacillus spp. were also performed to assess the overall microbiological quality of the CMR. Twenty-six (31.3%) of the 83 CMR samples showed evidence of the presence of MAP. Seventeen (20.5%) tested positive for viable MAP by the PMS-phage assay, with plaque counts ranging from 6 to 1,212 pfu/50 mL of reconstituted CMR (average 248.5 pfu/50 mL). Twelve (14.5%) CMR samples tested positive for viable MAP by PMS-culture; isolates from all 12 of these samples were subsequently confirmed by whole-genome sequencing to be different cattle strains of MAP. Seven (8.4%) CMR samples tested positive for MAP DNA by IS900 qPCR. Four CMR samples tested positive by both PMS-based tests and 5 CMR samples tested positive by IS900 qPCR plus one or other of the PMS-based tests, but only one CMR sample tested positive by all 3 MAP detection tests applied. All conventional microbiology results were within current standards for whole milk powders. A significant association existed between higher total bacterial counts and presence of viable MAP indicated by either of the PMS-based assays. This represents the first published report of the isolation of viable MAP from CMR. Our findings raise concerns about the potential ability of MAP to survive manufacture of dried milk-based products.

Comparing ELISA test-positive prevalence, risk factors and management recommendations for Johne's disease prevention between organic and conventional dairy farms in Ontario, Canada

Johne's disease (JD) is a chronic, infectious disease in cattle. Between 2010 and 2013, a voluntary JD control program was successfully launched in Ontario, Canada, including a Risk Assessment and Management Plan (RAMP) and JD ELISA testing of the entire milking herd. Over the last decade, the organic dairy sector has been growing. However, organic farming regulations and philosophies may influence the risk for JD transmission on Ontario organic dairy farms. The aim of this cross-sectional study was to investigate differences in JD ELISA test positive prevalence, risk factors for JD and recommendations for JD prevention between organic and conventional dairy herds in Ontario. RAMP results (i.e. RAMP scores and recommendations) and ELISA results were available for 2103 dairy herds, including 42 organic herds. If available, additional data on milk production, milk quality, and herd characteristics were gathered. Organic and conventional herds had a similar herd-level JD ELISA test-positive prevalence (26.2% and 27.2%, respectively). Organic herds (4.2%) had a higher within-herd JD ELISA test-positive prevalence compared to conventional herds (2.3%) if they had at least one JD test-positive animal on the farm. Organic farms had lower risk scores for biosecurity (9 points lower), and higher scores in the calving (7 points higher) and the calf-rearing management areas (4 points higher). After accounting for RAMP score, organic farms received fewer recommendations for the calving management area (Odds Ratio=0.41) and more recommendations in the adult cow management area (Odds Ratio=2.70). A zero-inflated negative binomial model was built with purchase of animals and the herd size included in the logistic portion of the model. Herd type (organic or conventional), colostrum and milk feeding practices, average bulk tank somatic cell count, and presence of non-Holstein breeds were included in the negative binomial portion of the model. Organic farms had a higher number of test positive animals (Count Ratio=2.02). Further research is necessary to investigate the apparent disconnect between risk factors and recommendations on organic dairy farms.