Multiplex PCR for detection of Anaplasma marginale, A. bovis and A. platys in cattle

Genetic diversity and prevalence of emerging Rickettsiales in Yunnan Province: a large-scale study

BACKGROUND

Rickettsia and related diseases have been identified as significant global public health threats. This study involved comprehensive field and systematic investigations of various rickettsial organisms in Yunnan Province.

METHODS

Between May 18, 2011 and November 23, 2020, field investigations were conducted across 42 counties in Yunnan Province, China, encompassing small mammals, livestock, and ticks. Preliminary screenings for Rickettsiales involved amplifying the 16S rRNA genes, along with additional genus- or species-specific genes, which were subsequently confirmed through sequencing results. Sequence comparisons were carried out using the Basic Local Alignment Search Tool (BLAST). Phylogenetic relationships were analyzed using the default parameters in the Molecular Evolutionary Genetics Analysis (MEGA) program. The chi-squared test was used to assess the diversities and component ratios of rickettsial agents across various parameters.

RESULTS

A total of 7964 samples were collected from small mammals, livestock, and ticks through Yunnan Province and submitted for screening for rickettsial organisms. Sixteen rickettsial species from the genera Rickettsia, Anaplasma, Ehrlichia, Neoehrlichia, and Wolbachia were detected, with an overall prevalence of 14.72%. Among these, 11 species were identified as pathogens or potential pathogens to humans and livestock. Specifically, 10 rickettsial organisms were widely found in 42.11% (24 out of 57) of small mammal species. High prevalence was observed in Dremomys samples at 5.60%, in samples from regions with latitudes above 4000 m or alpine meadows, and in those obtained from Yuanmou County. Anaplasma phagocytophilum and Candidatus Neoehrlichia mikurensis were broadly infecting multiple genera of animal hosts. In contrast, the small mammal genera Neodon, Dremomys, Ochotona, Anourosorex, and Mus were carrying individually specific rickettsial agents, indicating host tropism. There were 13 rickettsial species detected in 57.14% (8 out of 14) of tick species, with the highest prevalence (37.07%) observed in the genus Rhipicephalus. Eight rickettsial species were identified in 2375 livestock samples. Notably, six new Rickettsiales variants/strains were discovered, and Candidatus Rickettsia longicornii was unambiguously identified.

CONCLUSIONS

This large-scale survey provided further insight into the high genetic diversity and overall prevalence of emerging Rickettsiales within endemic hotspots in Yunnan Province. The potential threats posed by these emerging tick-borne Rickettsiales to public health warrant attention, underscoring the need for effective strategies to guide the prevention and control of emerging zoonotic diseases in China.

First report on the molecular detection and genetic diversity of Anaplasma marginale in healthy dairy cattle in Khon Kaen province, Thailand

Background and Aim

Bovine anaplasmosis (BA) is one of the most important diseases of ruminants worldwide, causing significant economic losses in the livestock industry due to the high morbidity and mortality in susceptible cattle herds. Anaplasma marginale is the main causative agent of BA occurring worldwide in tropical and subtropical regions. This study aimed to investigate the first molecular detection and genetic diversity of A. marginale in dairy cattle in Khon Kaen Province, Thailand.

Materials and Methods

Blood samples were collected from 385 lactating cows from 40 dairy farms in five districts of Khon Kaen, regardless of age and health status. To detect A. marginale, all DNA preparations were used for molecular diagnosis using a single polymerase chain reaction with the msp4 gene target. A phylogenetic tree was constructed from the msp4 gene sequences using molecular genetic characterization. Genetic diversity was calculated as haplotype diversity, haplotype number, number of nucleotide differences, nucleotide diversity, and average number of nucleotide differences.

Results

The overall prevalence of A. marginale was 12.72% (49/385). The highest prevalence (17.19%) was found in Ubolratana district, followed by Muang, Kranuan, Khao Suan Kwang, and Nam Phong districts (14.94%, 14.74%, 13.79%, and 3.70%, respectively). Phylogenetic analysis showed that A. marginale was closely related to isolates from Australia (98.96%), China (99.68%), Spain (99.74%), and the USA (99.63%).

Conclusion

The molecular prevalence of BA in dairy cattle is the first to be observed in this area, and the genetic variability with separated clusters shown in the msp4 gene of A. marginale revealed species variation in dairy cattle. This significant genetic diversity contributes to the understanding of the diversity of A. marginale and will be important for the control and prevention of A. marginale in dairy cattle.