Anaplasma marginale(Rickettsiales: Anaplasmataceae): recent advances in defining host–pathogen adaptations of a tick-borne rickettsia

Abstract

The tick-borne intracellular pathogen Anaplasma marginale (Rickettsiales: Anaplasmataceae) develops persistent infections in cattle and tick hosts. While erythrocytes appear to be the only site of infection in cattle, A. marginale undergoes a complex developmental cycle in ticks and transmission occurs via salivary glands during feeding. Many geographic isolates occur that vary in genotype, antigenic composition, morphology and infectivity for ticks. In this chapter we review recent research on the host-vector-pathogen interactions of A. marginale. Major surface proteins (MSPs) play a crucial role in the interaction of A. marginale with host cells. The MSP1a protein, which is an adhesin for bovine erythrocytes and tick cells, is differentially regulated and affects infection and transmission of A. marginale by Dermacentor spp. ticks. MSP2 undergoes antigenic variation and selection in cattle and ticks, and contributes to the maintenance of persistent infections. Phylogenetic studies of A. marginale geographic isolates using msp4 and msp1alpha provide information about the biogeography and evolution of A. marginale: msp1alpha genotypes evolve under positive selection pressure. Isolates of A. marginale are maintained by independent transmission events and a mechanism of infection exclusion in cattle and ticks allows for only the infection of one isolate per animal. Prospects for development of control strategies by use of pathogen and tick-derived antigens are discussed. The A. marginale/vector/host studies described herein could serve as a model for research on other tick-borne rickettsiae.

Detection and phylogenetic characterization of Theileria spp. and Anaplasma marginale in Rhipicephalus bursa in Portugal

“…In Portugal and Spain, R. bursa is a proven vector of A. marginale and the infection of cattle, known as bovine anaplasmosis, caused by this pathogen has been already reported (Caeiro, 1999;de la Fuente et al, 2004a;Kocan et al, 2004). Bovine anaplasmosis is now known to be endemic in tropical and subtropical regions worldwide, causing substantial economic losses to cattle industries (Kocan et al, 2003).…”

Molecular and serological prevalence of Anaplasma marginale in cattle of North Central Morocco

“…and Ixodes spp. (Uilenberg, 1995;De Waal et al, 2000;Jongejan and Uilenberg, 2004;Kocan et al, 2004). Tick transmissibility of Anaplasma is complex and ranges from very efficient transmission to non-transmission related to both Anaplasma strains as well as species of tick (Ueti et al, 2007).…”

“…Anaplasmosis has been reported in different regions of Morocco (Verhulst et al, 1983;Sahibi et al, 1998b), but it has a perceived lower incidence compared with theileriosis and babesiosis. Although, severe economic losses have been reported due to anaplasmosis outbreaks in several parts of the world (Herrero et al, 1998;Kocan et al, 2000Kocan et al, , 2004Grisi et al, 2002;Jongejan and Uilenberg, 2004), no specific disease outbreak of A. marginale in cattle has been reported in Morocco and the only epidemiological studies of anaplasmosis reported previously were conducted more than a decade ago (Sahibi et al, 1998b).…”

Tristeza parasitária bovina no Sertão da Paraíba

“…A infecção é causada pelo desenvolvimento e multiplicação de Babesia spp. e A. marginale nas células sangüíneas e tem como sinais clínicos febre, anemia, icterícia (mais intensa e comum na anaplasmose), hemoglobinúria (na babesiose), parada ou redução da ruminação, sinais nervosos (característicos da babesiose por B. bovis, o mais virulento dos três agentes), anorexia e prostração (Dreher et al 2005, Kocan et al 2004, Souza et al 2000.…”