Mycoplasma bovis, M. bovigenitalium and M. dispar as bovine pathogens: Brief characteristics of the pathogens

Abstract

The cattle mycoplasmas are widespread throughout the world (A.M. Parker et al., 2018; M. Abed Alhussen et al., 2020). This review presents data on the epidemiology and diagnosis of mycoplasmosis in cattle caused by M. bovis, M. bovigenitalium, and M. dispar. Mycoplasmas can cause economically important diseases in cattle, including mastitis, arthritis, keratoconjunctivitis, otitis media, pneumonia, and reproductive disorders (R.A.J. Nicholas et al., 2008; F.P. Maunsell et al., 2011). Mycoplasmas are characterized by a size of up to 150 μm, small genome (0.58-1.38 million base pairs) a low G-C composition (23-40 %) and the absence of a cell wall which determines their polymorphism and resistance to antibiotics, influencing the synthesis of the bacterial cell wall (R.A.J. Nicholas et al., 2008; P. Vos et al., 2011). Mycoplasma surface antigens are highly variable both in vitro and in vivo, which leads to significant variability of isolates (M.A. Rasheed et al., 2017). They also play an important role in overcoming the host's immune system. In addition, some of these antigens are involved in the adhesion of mycoplasmas to host cells (Y. Guo et al., 2017). After adhesion, many mycoplasmas produce a variety of products that damage host cells and enhance pathogenesis (L.A. Khan et al., 2005). They can also form biofilms that increase resistance to drying out and heat stress (L. McAuliffe et al., 2006; F. Gomes et al., 2016). Moreover, the invasion and intracellular survival of mycoplasmas in cattle cells contributes to the preservation and spread in the host organism (J. Van der Merwe et al., 2010). The incubation period for mycoplasma infection in cattle depends on many factors, i.e., the infectious dose, the presence of associated infections, the conditions of keeping the animals in the herd and the stress state of the animals (M.J. Calcutt et al., 2018). Sick animals are a source of infection, because they can shed the pathogen with nasal discharge and sperm for several months and sometimes for several years (K.A. Clothier et al., 2010; V. Punyapornwithaya et al., 2010). It should be noted that at low temperatures, mycoplasmas remain viable for a long time: in deeply frozen cattle semen, the pathogen can remain infectious for many years (A. Kumar et al., 2011). The high contagiousness of some species of Mycoplasma spp., their low sensitivity to treatment and the associated consequences of culling for the affected population make timely and accurate diagnosis important for disease control and prevention (A.M. Parker et al., 2018). The cultural methods can be applied for isolation and identification of the pathogen. However, these methods have limitations. Cultivation of mycoplasmas requires a complex medium, special equipment and technical skills (R.A.J. Nicholas et al., 2008; M.J. Calcutt et al., 2018; A.M. Andersson et al., 2019). Mycoplasmas require 7-10-day cultivation at a temperature of 37 °С and 5-10 % CO2. The colony has the “Fried-egg” appearance characteristic of most mycoplasmas (P.J. Quinn et al., 2011). By contrast, PCR provides a rapid and accurate diagnosis of the disease by detecting mycoplasmal DNA (A.M. Andersson et al., 2019). Furthermore, many other methods of diagnostics of bovine mycoplasma are used, such as MALDI-TOF MS (Matrix assisted laser desorption ionization time-of-light mass spectrometry), latex agglutination, immunochromatographic assays etc., however, each method has its advantages and disadvantages, which should be considered before application (M.J. Calcutt et al., 2018; B. Pardon et al., 2020).