Abstract
The present study reports the genetic diversity of Anaplasma marginale during anaplasmosis outbreaks in rural properties of the states of Goiás and São Paulo, Brazil. Mortality rates of 3.5% (37/1,050) in calves, 4.7% (45/954) in heifers and 1.1% (25/2,200) in lactating cows were observed in a cattle herd of the municipality of Mambaí, state of Goiás, central-western Brazil. In a cattle herd from the municipality of Lins, state of São Paulo, in southeastern Brazil, none of the animals died, despite presenting clinical signs suggestive of bovine anaplasmosis and exhibiting a drastic decrease in milk production. Thus, blood samples were collected from 100 animals with clinical signs suggestive of bovine anaplasmosis in the municipalities of Mambaí and Lins. Based on the microsatellite structure of the MSP1a of A. marginale, the genotypes E and H were observed in Lins, and the C, D and E genotypes were found in Mambaí. The analysis of the tandem repeat structures of the MSP1a showed nine different strains (τ-10 -15, α-β2, α-β3-13, α-β2 192, τ-β-100, α-β2-Γ, 193-β-100, 191-13-Γ and 191-13-18) in Lins and two (α-β3-Γ and E-F-φ2-F2) in Mambaí. Three new tandem repeats of MSP1a (191, 192 and 193) were described. The τ-10-15 and α-β3-Γ strains were predominantly associated with the occurrence of clinical anaplasmosis and mortality in calves, heifers and lactating cows.
Highlights
Anaplasma marginale is a pathogen transmitted by ticks that belongs to the Anaplasmataceae family, order Rickettsiales (DUMLER et al, 2001)
The τ-10-15 and α-β3-Γ strains were predominantly associated with the occurrence of clinical anaplasmosis and mortality in calves, heifers and lactating cows
Two explanations exist for the occurrence of a bovine anaplasmosis outbreak on the property located in Mambaí: (1) mechanical transmission of A. marginale by the high number of Stomoxys calcitrans flies originated from larvae that developed in faeces, accumulated in the environment and/or (2) the biological transmission of A. marginale by Rhipicephalus (Boophilus) microplus after the animals were placed in an area infested with cattle tick
Summary
Anaplasma marginale is a pathogen transmitted by ticks that belongs to the Anaplasmataceae family, order Rickettsiales (DUMLER et al, 2001). This rickettsia is a gram negative, obligate intracellular bacterium that can be biologically transmitted by ticks, can be mechanically transmitted by bloodsucking flies and fomites contaminated with infected blood, and, less commonly, can be transmitted via the placenta (KOCAN et al, 2010; AUBRY & GEALE, 2011). The genetic diversity of A. marginale strains is high in cattle in endemic regions worldwide (PALMER et al, 2001; FUENTE et al, 2007; CABEZAS‐CRUZ et al, 2013; SILVA et al, 2015a). Despite the genetic diversity of MSP1a, this gene is considered a stable genetic marker, which is conserved in infections in cattle and ticks (PALMER et al, 2001; BOWIE et al, 2002; FUENTE et al, 2003b)
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