Distinct Geographic Distribution of
Candidatus
Rickettsia
jingxinensis
and
Rickettsia heilongjiangensis
in
Haemaphysalis longicornis
Ticks from Northeast and East-Central China
Background:
The Asian
Haemaphysalis longicornis
is capable of transmitting a wide range of zoonotic pathogens. This study aimed to investigate the prevalence and characteristics of major pathogens in questing
H. longicornis
ticks collected from two geographically and ecologically distinct regions in China.
Methods:
A total of 1004 questing
H. longicornis
ticks were collected from Liaoning Province (Northeast China;
n
= 882) and Anhui Province (Central and Eastern China;
n
= 122) and pooled into 670 mixed samples. Tick species were identified by mitochondrial cytochrome oxidase I gene sequencing. Nucleic acid samples from all pools were first screened for
Dabie bandavirus
using RT-PCR and for bacteria using universal 16S rRNA primers. Bacteria-positive samples were further tested using polygenic seminested PCR for
Rickettsia
spp. and
Coxiella
-like endosymbionts (CLEs). Phylogenetic analyses, including polygene sequence analysis, were performed to ensure the accuracy of species identification and to explore genetic relationships.
Results:
No
Dabie bandavirus
was detected in any samples. Among the 670 tick pools, 14 were positive for spotted fever group rickettsiae (SFGR), with an overall minimum infection rate (MIR) of 1.4% (14/1004). Notably, the detected SFGR species showed clear geographic segregation:
Candidatus
Rickettsia
jingxinensis
was detected only in Liaoning Province (MIR of 1.4%), while
Rickettsia heilongjiangensis
was found exclusively in Anhui Province (MIR of 1.6%). Additionally, CLEs (overall MIR of 2.0%) were identified in 20 tick pools, with a significantly higher prevalence in Anhui Province (10.7%) than in Liaoning Province (0.8%;
p
< 0.001).
Conclusions:
This surveillance revealed a distinct geographical distribution pattern of SFGR species in
H. longicornis
populations in China and confirmed the presence of
Ca
. R.
jingxinensis
in the northeast and
R. heilongjiangensis
in the central and eastern regions. These findings, supported by polygenic evidence, provide essential epidemiological data for understanding regional tick-borne disease risks and highlight the need for continued region-specific surveillance.