A novel zoonotic Anaplasma species is prevalent in small ruminants: potential public health implications

Abstract

BackgroundTick-borne diseases currently represent an important issue for global health. A number of emerging tick-transmitted microbes continue to be discovered, and some of these are already identified as the cause of human infections. Over the past two decades, Anaplasma phagocytophilum is considered to be mainly responsible for human anaplasmosis. However, a novel zoonotic pathogen provisionally named “Anaplasma capra” has recently been identified in China. In this study, we did an active surveillance of A. capra in goats and sheep in different geographical regions of China.MethodsThe presence of A. capra was determined by nested PCR in 547 blood samples collected from goats and sheep from 24 counties distributed in 12 provinces in China. The molecular characterization of A. capra isolates in sheep and goats was achieved based on four conventional genetic markers (16S rRNA, gltA, groEL and msp4 genes).Results Anaplasma capra was identified in 75 of 547 animals, with an overall prevalence of 13.7%. The infection rates in the survey sites ranged from 0 to 78.6%, and were significantly different (P < 0.01). Phylogenetic analysis revealed that the isolates obtained from goats, sheep, Ixodes persulcatus ticks and humans create a separate clade within the genus Anaplasma and distinct from other recognized Anaplasma species. These findings indicated that these A. capra isolates possess the same molecular characteristics, suggesting that this organism could be a substantial health threat to both animals and humans.Conclusions Anaplasma capra is an emerging tick-transmitted zoonotic pathogen. This novel Anaplasna species is widespread across China with an overall prevalence of 13.7% in goats and sheep with isolates indistinguishable from those found in humans. These findings warrant increased public health awareness for human anaplasmosis.

Novel variants of the newly emerged Anaplasma capra from Korean water deer (Hydropotes inermis argyropus) in South Korea

“…Epidemiological data for this pathogen in wildlife are lacking in Korea; however, our findings are similar to those obtained from wildlife (five takins, three Himalayan gorals, three Reeves's muntjacs, one forest musk deer and one wild boar) in China [24]. In addition, a low percentage of infection rate was reported cattle, sheep and goats in China, Sweden and Korea [15][16][17][18][19], indicating that A. capra has a broad host range. Occurrence of infection during the study period from 2015 to 2018 indicates the persistence of the infection in KWD, suggesting that the species may act as a reservoir for this pathogen.…”

“…Our genetic profiling results indicated that the newly generated 16S rRNA gene sequences shared a homology of > 99.5% with sequences of A. capra strains from humans, sheep, goats, cattle and ticks [12,15,16,18,20,22], suggesting that they likely are within the same species of bacteria [38,39]. Clustering of sequences named A. centrale from deer (Cervus nippon nippon) (GenBank: AB211164) and cattle (GenBank: AF283007) in Japan and from ticks (Haemaphysalis longicornis) in Korea (Gen-Bank: GU064903), as well as Anaplasma spp.…”

“…This may be attributed to persistent infection making the pathogen below detectable level in the blood of these animals. In support of this view, A. capra has been reported to infect endothelial cells [12,15], making its detection in the blood possible in case of considerable bacteremia or released endothelial cells, resembling Rickettsia species [12]. Furthermore, the sample size and species and/or the age of animals may play a role in these findings.…”

“…The provisional name Anaplasma capra was assigned after its initial characterization in goats (Capra aegagrus hircus) in China [12]. Later, it was isolated from sheep, goats and cattle in different geographical regions [15][16][17][18][19] as well as from various tick species (Haemaphysalis qinghaiensis, H. longicornis, Ixodes persulcatus) [12,[20][21][22][23]. Infection of A. capra was also reported in six wild animals in China including three takins (Budorcas taxicolor), two Reeves's muntjacs (Muntiacus reevesi) and one forest musk deer (Moschus berezovskii) [24].…”

“…Anaplasma species usually parasitize bone marrowderived elements, including neutrophils (A. phagocytophilum), erythrocytes (A. marginale, A. centrale and A. ovis), monocytes (A. bovis) and platelets (A. platys) [7,9,10,12]. However, A. capra seems to infect endothelial cells, rendering its microscopic detection in blood smears unreliable [12,15]. In humans, the disease caused by A. capra is generally characterized by undifferentiated fever, headache, malaise, dizziness, myalgia and chills, with potential progression to CNS involvement and cerebrospinal fluid pleocytosis [12].…”