A new typing technique for the Rickettsiales Ehrlichia ruminantium: Multiple-locus variable number tandem repeat analysis

Economic Game Theory to Model the Attenuation of Virulence of an Obligate Intracellular Bacterium

“…In the laboratory it has been shown that the Gardel strain is attenuated after 237 passages, while the Senegal strain is already attenuated after just 64 passages and the Welgevonden strain needs only 43 passages to attenuate (Zweygarth et al, 2005; Pilet et al, 2012; Marcelino et al, 2015). These differences can be explained by slightly modifying the game: Instead of assuming $r>\frac{L-c}{L}$, consider r a random variable such that at every period $r=r^{+}>\frac{L-c\left(0\right)}{L}$ with probability q and $r=r^{-}<\frac{L-c\left(0\right)}{L}$ with probability 1-q .…”

“…The proposed game allows us to understand the evolutionary process that leads to the observed virulence/fitness levels of attenuated or virulent obligate intracellular bacteria, such as E. ruminantium , in in vivo and in vitro conditions (Pilet et al, 2012; Marcelino et al, 2015). Our game shows that the aggressiveness of an obligate intracellular pathogenic bacterium is host-triggered and that modifying the host's defense system can lead to an attenuated strain due to an evolutionary process.…”

“…It has been shown that in vitro passaging of the obligate intracellular bacteria E. ruminantium can lead to an attenuated strain (Jongejan, 1991; Zweygarth et al, 2005; Pilet et al, 2012; Marcelino et al, 2015). In vitro and in vivo infection essays have shown that the virulent strain is highly pathogenic to goats and toxic to host cells in vitro just after infection, while the attenuated strain is not lethal in goats and has a shorter life cycle (Pilet et al, 2012; Marcelino et al, 2015).…”

“…In vitro and in vivo infection essays have shown that the virulent strain is highly pathogenic to goats and toxic to host cells in vitro just after infection, while the attenuated strain is not lethal in goats and has a shorter life cycle (Pilet et al, 2012; Marcelino et al, 2015). Although, this mechanism has been essential for the development of inactivated vaccines against obligate intracellular bacterial infections, such as Heartwater (Zweygarth et al, 2005, 2008; Vachiéry et al, 2006), there is little understanding of the attenuation process and no formal theory has been proposed.…”

A user-friendly and scalable process to prepare a ready-to-use inactivated vaccine: The example of heartwater in ruminants under tropical conditions

“…This disease has a strong economic impact (up to 46 million dollars per year for the Southern African Development Community) due to the combined cost of acaricide applications, antibiotic treatments, loss of production and loss of animals [1,2]. http Several experimental vaccines (recombinant, attenuated or inactivated) are under development [1] but none is fully effective due to the high antigenic diversity of ER strains [3][4][5][6][7]. The inactivated vaccine (based on chemically inactivated ER elementary bodies) is a good candidate (despite inducing animal morbidity) as it can protect against homologous and some heterologous challenge [8][9][10] and it can include a cocktail of strains according to the geographical regions to improve vaccine efficacy [11].…”