The genus Anaplasma: new challenges after reclassification

Abstract

The genus Anaplasma is one of four distinct genera in the family Anaplasmataceae, which are obligate intracellular pathogens vectored by ticks and found exclusively within parasitophorous vacuoles in the host cell cytoplasm. The 2001 reclassification of the order Rickettsiales expanded the genus Anaplasma, which previously contained pathogens that were host specific for ruminants (A. marginale, A. centrale and A. ovis), by adding A. phagocytophilum, a unification of three organisms previously classified as Ehrlichia (E. equi, E. phagocytophila and the unnamed agent of human granulocytic ehrlichiosis). Also included in the genus Anaplasma were A. bovis (formerly E. bovis), A. platys (formerly E. platys) and Aegyptianella pullorum. Despite the genomic relatedness of the regrouped organisms, many aspects of their biology are diverse, including their host specificity, host cell preferences, major surface proteins (MSPs) and tick vectors. This review focuses on the two most important pathogens: A. marginale, which causes bovine anaplasmosis, and A. phagocytophilum, the aetiologic agent of tick-borne fever in sheep and human granulocytic anaplasmosis, an emerging tick-borne disease of humans. For both pathogens, strain diversity is much greater than previously recognised. While MSPs were found to be useful in phylogenetic studies and strain identification, highly conserved MSPs were found to affect the specificity of serologic tests. Comparison of these two important pathogens highlights the challenges and insight derived from reclassification and molecular analysis, both of which have implications for the development and evaluation of diagnosis and control strategies.

Molecular survey and characterization of a novel Anaplasma species closely related to Anaplasma capra in ticks, northwestern China

“…The members of the genus Anaplasma are now recognized to be important human and animal pathogens [21]. To date, two Anaplasma species have been identified as pathogens of human anaplasmosis [5, 12].…”

Molecular Detection and Characterization of Zoonotic and Veterinary Pathogens in Ticks from Northeastern China

“…Anaplasma bovis has a wide host range, whose susceptible species include cattle, goats, dogs, cats, and deer (Kocan et al, 2015). In recent years, molecular detection of A. bovis infection showed an overall prevalence of 10–16% in goats, and 9.7% in sheep in China (Liu et al, 2012; Zhang et al, unpublished).…”

“…Pritt et al (2011) identified a third species of Ehrlichia muris in patients who had fever, malaise, headache, and lymphopenia in Wisconsin and Minnesota, the United States, and it has also been found in Europe and Asia (Rar et al, 2010; Tateno et al, 2015). Other species that infect animals include A. marginale , Anaplasma centrale , A. ovis , E. canis , and Ehrlichia minasensis (Wen et al, 2003; Kocan et al, 2015; Cabezas-Cruz et al, 2016). Several species have been described in China, such as A. ovis , Anaplasma bovis , and A. platys in Gansu province (Li et al, 2016), A. centrale and E. canis in Fujian province (Ge et al, 2016; Yu et al, 2016), and E. chaffeensis in Guangxi province (Yang et al, 2015b).…”

Bovine anaplasmosis and tick-borne pathogens in cattle of the Galapagos Islands

“…The genus Anaplasma is one of four distinct genera in the family Anaplasmataceae , which are obligate intracellular pathogens vectored by ticks (Kocan, de la Fuente, & Cabezas‐Cruz, ). The 2001 reclassification of the order Rickettsiales expanded the genus Anaplasma , which previously contained pathogens that were host specific for ruminants ( A. marginale, A. centrale and A. ovis ), by adding A. phagocytophilum, a unification of three organisms previously classified as Ehrlichia ( E. phagocytophila, E. equi , and the unnamed agent of human granulocytic ehrlichiosis) (Kocan et al., ). Also included in the genus Anaplasma are A. bovis (formerly E. bovis ), A. platys (formerly E. platys ) and Aegyptianella pullorum (Kocan et al., ).…”