Sensitivity of two methods to detect Mycoplasma agalactiae in goat milk

Influence of natural and climatic conditions on the distribution and forms of contagious agalactia in sheep in Bessarabia, Ukraine

Introduction

Contagious agalactia of ruminants is an endemic disease caused by Mycoplasma agalactiae in flicting significant losses on farms in deaths and forced slaughter of sick animals, abortions, births of sick young animals, and reduced milk and wool production. The aim of the study was to determine the influence of hydrometeorological conditions on the distribution and forms of contagious agalactia in sheep in Bessarabia, Ukraine.

Material and Methods

The epizootic situation regarding contagious agalactia was studied during 2011–2021 on sheep farms in the south of the Odesa region in Bessarabia. Over two million blood samples from sheep aged 1–6 years were serologically investigated and the prevalence of agalactia was correlated with Selyaninov’s hydrothermal coefficient for each sampling year.

Results

High rates of infection of sheep with contagious agalactia (from 13.1% to 14.4%) were registered in 2012, 2016 and 2021, years which according to the hydrothermal coefficient of 1.0 were sufficiently moist. The lowest incidence rates, from 6.5% to 7.4%, were registered in the very dry 2013, 2014 and 2019 with hydrothermal coefficients of 0.5‒0.6. In sufficiently moist years, contagious agalactia of sheep manifested itself in the mastitic form, while in the dry period the mastitic form was half as prevalent, and the mixed, articular and ocular forms of the disease proliferated.

Conclusion

The results indicate the circulation of Mycoplasma agalactiae among small ruminants in Bessarabia, and that the prevalence and the course of the associated disease depend on the humidity of the climate, i.e. the value of the hydrothermal coefficient.

Validation of Loop-Mediated Isothermal Amplification (LAMP) Field Tool for Rapid and Sensitive Diagnosis of Contagious Agalactia in Small Ruminants

Simple Summary

Contagious agalactia (CA) is an infectious disease of small ruminants endemic in the Mediterranean countries, causing significant socioeconomic impacts predominantly on small-scale farmers who still subsist on marginal lands. Mycoplasma agalactiae is historically considered the principal etiological agent of CA, especially in sheep. Clinical signs are characterised by mastitis, arthritis, keratoconjunctivitis and occasionally, abortion. Rapid, accurate and cost-effective field tests are urgently needed for effective control of M. agalactiae mastitis. Our study illustrated the validation of a Loop-Mediated Isothermal Amplification (LAMP) test for the detection of M. agalactiae in dairy sheep in order to confirm its application as a diagnostic tool in the field level.

Abstract

Contagious agalactia (CA), an infectious disease of small ruminants, caused by Mycoplasma agalactiae, is responsible for severe losses to dairy sheep production with substantial socioeconomic impacts on small-scale farmers. The diagnosis of CA is still problematic, time-consuming and requires well-equipped labs for confirmation of outbreaks. Therefore, rapid, accurate and cost-effective diagnostic tests are urgently needed. This work aims to validate a novel Loop-Mediated Isothermal Amplification (LAMP) test, based on the p40 target gene, for the detection of M. agalactiae in dairy sheep in order to confirm its potential practical use as a rapid and cheap field test. The LAMP system proposed in this study consists of a portable device composed of real-time fluorometer with the automatic interpretation of results displayed in a tablet. A total of 110 milk samples (90 positives and 20 negatives) were analysed to optimise the analysis procedure and to investigate the efficacy and robustness of the LAMP method. All samples were analysed using LAMP and conventional real-time PCR to compare the diagnostic sensitivity of the methods. The sensitivity of the LAMP was 10-fold higher than that of real-time PCR, with a detection limit up to 10³ CFU/ml. The LAMP assay was able to detect M. agalactiae in 81 of 90 (90%, 95%CI 0.84–0.96) positive milk samples compared to 69 (77%, 95%CI 0.59–0.95) positive samples detected by real-time PCR; no positive signal occurred for any of the negative milk samples in either test. Therefore, the LAMP assay was found to be more sensitive than real-time PCR, low-cost, easy to perform, fast and not affected by contamination, indicating its potential as an effective diagnostic tool in the field level for the diagnosis of CA.

Contagious Agalactia In Sheep And Goats: Current Perspectives

Contagious agalactia (CA) is a disease caused equally by four Mycoplasma species, in single or mixed infections. Clinical signs are multiple, including mastitis, arthritis, keratoconjunctivitis, pneumonia, and septicemia, non-specific, and expressed differently depending whether sheep or goats are affected, on causative mycoplasmas as well as type of husbandry. CA has been reported worldwide and its geographic distribution maps to that of small ruminant breeding areas. However, as current diagnostic tests are expensive and difficult to implement, it is certainly underdiagnosed and prevalence data are only available for a few countries. CA control relies on vaccines, chemotherapy and good herd management practices. It requires long-term commitment but is often unsuccessful, with frequent clinical relapses. The persistence of the etiological agents, despite their overall susceptibility to antimicrobials, comes from their genetic plasticity and capacity to escape the host immune response. The existence of asymptomatic carriers and the numerous sources of infections contribute to rapid spread of the disease and complicate the control and prevention efforts. Here we review all these aspects in order to highlight recent progress made and identify gaps in knowledge or tools needed for better disease management. Discussion also underlines the detrimental effect of contagious agalactia on small ruminant welfare.

Contagious agalactia monitoring in caprine herds through regular bulk tank milk sampling

Surveillance and control of Mycoplasma spp. responsible for contagious agalactia (CA) in caprine herds are important challenges in countries with a large small-ruminant dairy industry. In the absence of any clinical signs, being able to determine the potential circulation of mycoplasmas within a herd could help to prevent biosecurity issues during animal exchanges between farms and improve health management practices. The objective of this study was to determine whether regular sampling of bulk tank milk was suitable for such surveillance. Twenty farms were sampled once a month for 2 yr and CA-responsible mycoplasmas were detected by real-time PCR on DNA extracted from milk, using 3 different DNA extraction methods. The pattern of mycoplasma excretion in bulk tank milk was assessed over time and several herd characteristics were recorded together with any event occurring within the herds. In general, the results obtained with the different detection methods were comparable and mainly agreed with the culture results. Several patterns of excretion were observed but were not related to herd characteristics (size, breed, and so on). Recurrence of the same (sub)species and same pulsed-field gel electrophoresis subtype during the 2-yr period is indicative of the considerable persistence of mycoplasmas. This persistence was associated with intermittent excretion. In conclusion, bulk tank milk sampling could be valuable for controlling CA in caprine herds provided it is repeated several times, yet to be defined, per year and analyzed using an appropriate methodology and the right cut-off for interpretation.

Molecular biological tools applied for identification of mastitis causing pathogens

The molecular diagnostic tools became the gold standard of mastitis diagnosis in the last few years. They enable rapid, qualitative, quantitative and large scale diagnosis. In addition to their role in diagnosis, they can identify pathogens at the subspecies level which is necessary for the epidemiological studies. They are increasingly used in mastitis control programs through identification of suitable candidates for vaccine production and through the selection of mastitis resistant cattle breeds. The present molecular techniques are continuously improved and new techniques are developed in order to provide higher sensitivity and specificity and to minimize the costs. The present work aims to provide an overview of the modern molecular tools, discuss why they replaced the traditional tools and became the new gold standard in mastitis diagnosis through comparing both traditional and molecular tools, explore the prospective of the molecular diagnostic techniques in mastitis diagnosis and control and to explore new horizons of using molecular assays in near future.

Synthesis of Recombinant P48 of Mycoplasma agalactiae by Site Directed Mutagenesis and its Immunological Characterization

Contagious agalactia caused by Mycoplasma agalactiae is an economically important disease of sheep and goats and has been prevalent worldwide including India. The present study was undertaken to evaluate the membrane protein P48 of M. agalactiae for specific diagnosis of disease. For this, p48 gene of the organism was amplified by PCR and subjected to site directed mutagenesis to convert three TGA codons to TGG's and, subsequently, cloned into prokaryotic expression vector pPRO EX HTb. Purified recombinant P48 protein reacted to anti-P48 serum in western blotting, which confirmed its immunogenic nature. Furthermore, the immune-blotting of the cell lysates from various Indian isolates of M. agalactiae against anti-P48 serum resulted in a single band at ∼ 48 kDa among all isolates, indicating the conserved nature of P48 antigen in M. agalactiae. Also, the cross reactivity of P48 antigen among various Mycoplasma spp. was checked by western blotting which revealed reactivity only with M. agalactiae and M. bovis. Hence, this antigen could be exploited to differentiate M. agalactiae from other pathogenic Mycoplasma species except M. bovis. However, the inability of P48 to distinguish M. agalactiae from M. bovis does not downgrade the significance of P48 as the two species are usually host specific.

Presence of Mycoplasma agalactiae in semen of naturally infected asymptomatic rams

The purpose of the present study was to assess the presence of Mycoplasma agalactiae (Ma), the main causative agent of ovine contagious agalactia (CA), in semen of naturally infected rams. Therefore, semen samples from 167 rams residing in three different artificial insemination (AI) centers of a CA-endemic area were studied by microbiological and molecular techniques. In addition, serial ejaculates from the same rams were evaluated to determine the excretion dynamics of Ma. Of the 384 samples studied, Ma was detected in 56 (14.58%) which belonged to 44 different rams (26.35%). These findings confirm the ability of Ma to be excreted in semen of asymptomatic rams. Furthermore, these results also evidence the presence of these asymptomatic carriers of Ma in ovine AI centers, representing a serious health risk regarding the spread and maintenance of CA, especially in endemic areas. Moreover, the excretion of Ma in semen also points to the risk of venereal transmission of this disease. The current results highlight the need to implement control measures to prevent the admission of infected rams in AI centers and the necessity to continuously monitor semen samples to effectively detect infected individuals.