Transovarial Transmission of Anaplasma marginale in Rhipicephalus (Boophilus) microplus Ticks Results in a Bottleneck for Strain Diversity

Abstract

Anaplasma marginale is an obligate intraerythrocytic bacterium of bovines, responsible for large economic losses worldwide. It is mainly transmitted by Rhipicephalus (Boophilus) microplus ticks and, despite mounting evidence suggesting transovarial transmission, the occurrence of this phenomenon remains controversial. We evaluated the vector competence of R. microplus larvae vertically infected with A. marginale to transmit the bacterium to a naïve bovine. A subgroup of engorged female ticks collected from an A. marginale-positive animal was dissected and the presence of the pathogen in its tissues was confirmed. A second subgroup of ticks was placed under controlled conditions for oviposition. After confirming the presence of A. marginale in the hatched larvae, an experimental infestation assay was conducted. Larvae were placed on an A. marginale-free splenectomized calf. The bacterium was detected in the experimentally infested bovine 22 days post-infestation. We analyzed the A. marginale diversity throughout the transmission cycle using the molecular marker MSP1a. Different genotypes were detected in the mammalian and arthropod hosts showing a reduction of strain diversity along the transmission process. Our results demonstrate the vertical transmission of A. marginale from R. microplus females to its larvae, their vector competence to transmit the pathogen, and a bottleneck in A. marginale strain diversity.

Dynamic nesting of Anaplasma marginale in the microbial communities of Rhipicephalus microplus

“…Rhipicephalus microplus, commonly known as the cattle tick or tropical cattle tick, is a significant ectoparasite that infests cattle and other livestock. This tick species holds great importance due to its capacity to transmit various pathogens, with A. marginale being one of the most notable (De La Fourniere et al, 2023;Pereira et al, 2022).…”

“…Rhipicephalus microplus , commonly known as the cattle tick or tropical cattle tick, is a significant ectoparasite that infests cattle and other livestock. This tick species holds great importance due to its capacity to transmit various pathogens, with A. marginale being one of the most notable (De La Fourniere et al., 2023 ; Pereira et al., 2022 ). Anaplasma marginale is a bacterium that causes bovine anaplasmosis, a disease characterized by anemia, fever, and other clinical symptoms in cattle (Salinas‐Estrella et al., 2022 ).…”

Rearing of Rhipicephalus annulatus ticks on rabbits for the biological transmission of Anaplasma marginale

“…Twenty tick species belonging to five genera ( Rhipicephalus , Ixodes , Dermacentor , Hyalomma , and Amblyomma ) have been identified as potential vectors of A. marginale [ 4 ]. Although A. marginale can be transplacentally transmitted, this mode of transmission is not thought to have a significant impact on its epidemiology [ 5 ]. Rhipicephalus annulatus is a one-host tick involved in the biological transmission of A. marginale [ 6 ].…”