Longitudinal study of Mycobacterium avium ssp. paratuberculosis fecal shedding patterns and concurrent serological patterns in naturally infected dairy cattle

Long-term outcomes of the Italian Mycobacterium avium subspecies paratuberculosis control programme for dairy cattle

BACKGROUND

The considerable epidemiological and economic implications of paratuberculosis, caused by Mycobacterium avium subspecies paratuberculosis (MAP), have placed importance on control efforts aimed at preventing MAP transmission. In this context, Italy issued national guidelines for the control and status certification of MAP in dairy cattle in 2013.

METHODS

We assessed the long-term outcomes of the Italian MAP control programme for 14 dairy farms located in northern Italy by retrospectively reviewing the results of yearly serological tests, presence of clinical cases, MAP faecal shedding in serologically positive animals, farm management and health ranking as indicators of herd health between 2014 and 2021.

RESULTS

A significantly higher number of serologically positive animals were observed between 2014 and 2016 than between 2017 and 2021, as well as an improving trend in the paratuberculosis health ranking for nine of the 14 farms. No clinical cases were reported. MAP shedding was detected in 9.4% of serologically positive animals. Discarding colostrum and prioritised culling of seropositive animals assisted by adoption of standardised serological testing were presumed to have a key role in MAP control, despite the reluctance of some farmers to address hygienic issues and improve the separation of calves from adult animals.

LIMITATIONS

The small number of farms included in this study and the fact that these were not randomly selected may limit the generalisability of the findings.

CONCLUSIONS

The Italian paratuberculosis control plan has provided measures to limit the uncontrolled spread of MAP infection within and between herds by promoting animal trading between farms certified as negative or low risk.

Effects of Silirum®-Based Vaccination Programs on Map Fecal Shedding and Serological Response in Seven French Dairy Herds

(1) Background: paratuberculosis is an important disease in ruminants, causing worldwide economic losses to the livestock industry. Although vaccination is known not to prevent transmission of the causative agent Mycobacterium avium subsp. paratuberculosis (Map), it is considered an effective tool for paratuberculosis in infected herds. The objectives of this controlled field study were to evaluate the effects of the whole-cell heat-killed Silirum^® vaccine on Map fecal shedding and serological status in dairy herds infected with paratuberculosis. (2) Methods: The serological status (ELISA) and fecal shedding (qPCR) of 358 vaccinated cows were assessed over 3 years in 7 infected dairy herds in the Meuse department, France. Within each herd, cows from the last non-vaccinated birth cohort (n = 265) were used as controls. The probability and level of Map fecal shedding and the serological status were modeled using multivariable mixed general linear regression models. (3) Results: Overall, 34.7% of cows tested positive at least once on fecal qPCR, with significant differences between herds, but high shedding levels were observed in only 5.5% of cows. Compared to non-vaccinated seronegative cows, a statistically significant reduction in the probability of Map shedding was found only in cows vaccinated before 4 to 5 months of age that tested negative for Map antibodies throughout the study period (odds ratio = 0.5, 95% confidence interval: 0.3-0.9, p = 0.008), but no significant effect of vaccination on the amount of Map shedding could be evidenced. Finally, the younger the cows were when vaccinated, the less they tested positive on the serum ELISA. (4) Conclusions: a beneficial effect of vaccination on Map fecal shedding may exist in cows vaccinated before 4 to 5 months of age. The variability of the serum ELISA response in vaccinated cows remains to be investigated.

Genetic Features of Mycobacterium avium subsp. paratuberculosis Strains Circulating in the West of France Deciphered by Whole-Genome Sequencing

Paratuberculosis is a chronic infection of the intestine, mainly the ileum, caused by Mycobacterium avium subsp. paratuberculosis in cattle and other ruminants. This enzootic disease is present worldwide and has a negative impact on the dairy cattle industry. For this subspecies, the current genotyping tools do not provide the needed resolution to investigate the genetic diversity of closely related strains. These limitations can be overcome by the application of whole-genome sequencing (WGS), particularly for clonal populations such as M. avium subsp. paratuberculosis. The purpose of the present study was to undertake a WGS analysis with a panel of 200 animal field M. avium subsp. paratuberculosis strains selected based on a previous large-scale longitudinal study of Prim'Holstein and Normande dairy breeds naturally infected with M. avium subsp. paratuberculosis in the West of France. The pangenome analysis revealed that M. avium subsp. paratuberculosis has a closed pangenome. The phylogeny, based on alignment of 2,786 nonhomoplasic single nucleotide polymorphisms (SNPs), showed that the strain population is structured into three clades independently of the cattle breed or geographic distribution. The increased resolution of phylogeny obtained by WGS confirmed the homoplasic nature of the markers variable-number tandem repeat (VNTR) and short sequence repeat (SSR) used for M. avium subsp. paratuberculosis genotyping. These phylogenetic data also revealed independent introductions of the different genotypes in two main waves since at least 2003. WGS applied to this sampling demonstrated the presence of mixed infections in herds and at the individual animal level. Collectively, the phylogeny results inferred with French isolates compared to M. avium subsp. paratuberculosis isolates from around the world suggest introductions of M. avium subsp. paratuberculosis genotypes through the animal trade. Relationships between genetic traits and epidemiological data can now be investigated to better understand transmission dynamics of the disease. IMPORTANCE Mycobacterium avium subsp. paratuberculosis causes Johne's disease in ruminants, which is present worldwide and has significant negative impacts on the dairy cattle industry and animal welfare. Prevention and control of M. avium subsp. paratuberculosis infection are hampered by knowledge gaps in strain virulence, genotype distribution, and transmission dynamics. This work has revealed new insights into M. avium subsp. paratuberculosis strains currently circulating in western France and how they are related to strains circulating globally. We applied whole-genome sequencing (WGS) to obtain comprehensive information on genome evolution and discrimination of closely related strains. This approach revealed the history of M. avium subsp. paratuberculosis infection in France, refined the pangenomic characteristics of M. avium subsp. paratuberculosis, and demonstrated the existence of mixed infection in animals. Finally, this study identified predominant genotypes, which allow a better understanding of disease transmission dynamics. This information will facilitate tracking of this pathogen on farms and across agricultural regions, thus informing transmission pathways and disease control points.

Effective control of Johne’s disease in large Czech dairy herds

Introduction

Johne’s disease, caused by infection with Mycobacterium avium subsp. paratuberculosis (MAP), causes economic losses in dairy herds due to reduced milk production and premature culling. A test-and-cull strategy coupled with changes in calf rearing management preventing new infections has been introduced into infected herds to control MAP prevalence. This study appraised the effectiveness of these practice changes.

Material and Methods

In 19 large dairy herds (of a median 470 milk-producing cows), implementing MAP control measures for 3–7 years, a serum ELISA was used to detect infected cows in their dry-off period. The number of ELISA-positive animals per year (EPAY) was calculated and statistical analysis was used to test whether the EPAY total decreased during the control period and to analyse the EPAY in relationship to the duration of the control programme.

Results

Statistical support was found for a decrease of EPAY over time (P < 0.01, odds ratio 0.756) and in 14 herds a significant fall in the percentages of EPAY during the test period (P ≤ 0.05) was noted.

Conclusion

Our results demonstrated the effectiveness of the control measures in place to reduce MAP infection in herds with initial EPAY ≥3.36%. The missing decreasing trend in the remaining five herds with low average initial EPAY suggested the need for additional measures to reduce the number of infected animals in these herds.

Draft Genome Sequences of 142 Mycobacterium avium subsp. paratuberculosis Strains Isolated from Naturally Infected Dairy Cattle

Mycobacterium avium subsp. paratuberculosis is the etiological agent of Johne's disease in ruminants. Here, we report the annotated draft genome sequences of 142 M. avium subsp. paratuberculosis strains that were isolated from dairy cattle in France between 2014 and 2018. The genomes of these strains were sequenced using Illumina technology.

New and rapid strategies for the diagnosis of bovine paratuberculosis "in situ" using latex particles

The chemical coupling of a protoplasmatic antigen from Mycobacterium avium subsp. paratubeculosis onto core-shell carboxylated particles was investigated with the aim of producing latex-protein complexes to be used in immunoagglutination assays capable of detecting bovine paratuberculosis disease. For this purpose, sensitizations were carried out using both colored and not colored carboxylated latexes as well as the protoplasmatic antigen at pH close to its isoelectric point to favor the antigenic protein to approach the particle surface. In all cases, higher fractions of proteins were chemically-bound to carboxyl groups on the surface of the particles. The assessment of the performance of the visual immunoagglutination assays consisted of evaluating 111 sera from healthy and infected bovines with Mycobacterium avium subsp. paratuberculosis. Complexes obtained from the colored latex allowed an acceptable visual discrimination between the studied positive and negative sera. Most of the positive samples showed strong to very strong agglutination and only a few samples reacted weakly, i.e. a sensitivity of 70%. The specificity of the assay, on the other hand, was 86%. Therefore, this rapid detection technique allows an easy and inexpensive identification of animals possibly infected with paratuberculosis "in situ" in the herds.

Detection of Mycobacterium avium Subspecies paratuberculosis (MAP) Microorganisms Using Antigenic MAP Cell Envelope Proteins

Cell envelope proteins from Mycobacterium avium subspecies paratuberculosis (MAP) that are antigenically distinct from closely related mycobacterial species are potentially useful for Johne's Disease (JD) diagnosis. We evaluated the potential of ELISAs, based on six antigenically distinct recombinant MAP cell envelope proteins (SdhA, FadE25_2, FadE3_2, Mkl, DesA2, and hypothetical protein MAP1233) as well as an extract of MAP total cell envelope proteins, to detect antibodies against MAP in the sera of infected cattle. The sensitivity (Se) and specificity (Sp) of an ELISA based on MAP total cell envelope proteins, when analyzing 153 bovine serum samples, was 75 and 96%, respectively. Analysis of the same samples, using a commercial serum ELISA resulted in a Se of 56% and Sp of 99%. Results of ELISA analysis using plates coated with recombinant cell envelope proteins ranged from a highest Se of 94% and a lowest Sp of 79% for Sdh A to a lowest Se of 67% and a highest Sp of 95% for hypothetical protein MAP1233. Using polyclonal antibodies to MAP total cell envelope proteins, immunohistochemical analysis of intestinal and lymph node tissues from JD-positive cattle detected MAP organisms whereas antibodies to recombinant proteins did not. Finally, polyclonal antibodies to MAP total cell envelope protein and to recombinant SdhA, FadE25_2, and DesA2 proteins immunomagnetically separated MAP microorganisms spiked in PBS. These results suggest that antigenically distinct MAP cell envelope proteins and antibodies to these proteins may have potential to detect MAP infection in dairy cattle.

The enhancement of Th1 immune response by anti-PD-L1 antibody in cattle infected with Mycobacterium avium subsp. paratuberculosis

Johne's disease, caused by Mycobacterium avium subsp. paratuberculosis (MAP), is a chronic enteritis of ruminants. Previous studies have shown that programmed death-ligand 1 (PD-L1) is associated with the disease progression, and PD-L1 blockade activates MAP-specific Th1 responses in vitro. Here, we performed anti-PD-L1 antibody administration using 2 MAP-infected cattle at the late subclinical stage of infection. After administration, bacterial shedding was reduced or maintained at a low level. Additionally, MAP-specific Th1 cytokine production was upregulated, and CD69 expression was increased in T cells. Collectively, the treatment has a potential as a novel control method against Johne's disease.

Identification of the ABCC4, IER3, and CBFA2T2 candidate genes for resistance to paratuberculosis from sequence-based GWAS in Holstein and Normande dairy cattle

Background

Bovine paratuberculosis is a contagious disease, caused by Mycobacterium avium subsp. paratuberculosis (MAP), with adverse effects on animal welfare and serious economic consequences. Published results on host genetic resistance to MAP are inconsistent, mainly because of difficulties in characterizing the infection status of cows. The objectives of this study were to identify quantitative trait loci (QTL) for resistance to MAP in Holstein and Normande cows with an accurately defined status for MAP.

Results

From MAP-infected herds, cows without clinical signs of disease were subjected to at least four repeated serum ELISA and fecal PCR tests over time to determine both infected and non-infected statuses. Clinical cases were confirmed using PCR. Only cows that had concordant results for all tests were included in further analyses. Positive and control cows were matched within herd according to their birth date to ensure a same level of exposure to MAP. Cows with accurate phenotypes, i.e. unaffected (control) or affected (clinical or non-clinical cases), were genotyped with the Illumina BovineSNP50 BeadChip. Genotypes were imputed to whole-genome sequences using the 1000 Bull Genomes reference population (run6). A genome-wide association study (GWAS) of MAP status of 1644 Holstein and 649 Normande cows, using either two (controls versus cases) or three classes of phenotype (controls, non-clinical and clinical cases), revealed three regions, on Bos taurus (BTA) chromosomes 12, 13, and 23, presenting significant effects in Holstein cows, while only one of those was identified in Normande cows (BTA23). The most significant effect was found on BTA13, in a short 8.5-kb region. Conditional analyses revealed that only one causal variant may be responsible for the effects observed on each chromosome with the ABCC4 (BTA12), CBFA2T2 (BTA13), and IER3 (BTA23) genes as good functional candidates.

Conclusions

A sequence-based GWAS on cows for which resistance to MAP was accurately defined, was able to identify candidate variants located in genes that were functionally related to resistance to MAP; these explained up to 28% of the genetic variance of the trait. These results are very encouraging for efforts towards implementation of a breeding strategy aimed at improving resistance to paratuberculosis in Holstein cows.