Genetic Diversity and Coexistence of Babesia in Ticks (Acari: Ixodidae) from Northeastern China

Identification of Babesia capreoli from Korean Water Deer in the Republic of Korea

Babesiosis is a tick-borne disease caused by intraerythrocytic protozoa belonging to the genus Babesia that is primarily transmitted through Ixodid ticks and is highly pathogenic to ruminants, horses, pigs, dogs, cats, and in some cases, even humans. Babesia is considered an increasing threat to animal and human health. In this study we report Babesia capreoli infection in Korean water deer (Hydropotes inermis argyropus). Blood samples of 77 wild animals (62 Korean water deer and 15 Korean raccoon dogs [Nyctereutes procyonoides koreensis]) were analyzed to detect Babesia infection. First, PCR was performed to investigate Babesia infection using the partial 18S rRNA gene. Among the 77 wild animals examined, 11 Korean water deer were positive for infection as per the results of sequence analysis. Next, these 11 samples were reanalyzed by PCR using newly designed primers to differentiate between B. capreoli and Babesia divergens. Finally, only one Korean water deer sample was found to be positive for B. capreoli. The nucleotide sequence of this protozoan showed 99.6 - 99.7% identity to those of B. capreoli reported previously. Phylogenetic analysis revealed that the sequence belonged to the B. capreoli clade and diverged from the B. divergens clade. Three nucleotides at positions 631, 663, and 1637 were analyzed to differentiate between B. capreoli and B. divergens. The nucleotides at positions 631 and 1637 were identical to those of B. capreoli, whereas that at position 663 was different. The sequence detected in Korean water deer also exhibited differences at other four positions (669, 704, 711, and 1661) compared with other B. capreoli sequences. This study indicates that Korean water deer serve as a reservoir for B. capreoli. In addition, the primers designed in this study can be used to detect B. capreoli. Future studies should explore the tick vectors that transmit B. capreoli and its pathogenicity. This study was approved by the Institutional Committee of Graduate Studies and Research at Jeonbuk National University, ROK (IACUC decision no.: CBU 2014-00026).

Infection rates, species diversity, and distribution of zoonotic Babesia parasites in ticks: a global systematic review and meta-analysis

Zoonotic Babesia species are emerging public health threats globally, and are the cause of a mild to severe malaria-like disease which may be life threatening in immunocompromised individuals. In this study, we determine the global infection rate, distribution, and the diversity of zoonotic Babesia species in tick vectors using a systematic review and meta-analysis. We used the random-effects model to pool data and determined quality of individual studies using the Joanna Briggs Institute critical appraisal instrument for prevalence studies, heterogeneity using Cochran's Q test, and across study bias using Egger's regression test. Herein, we reported a 2.16% (3915/175345, 95% CI: 1.76-2.66) global infection rate of zoonotic Babesia species (B. divergens, B. microti, and B. venatorum) in tick vectors across 36 countries and 4 continents. Sub-group infection rates ranged between 0.65% (95% CI: 0.09-4.49) and 3.70% (95% CI: 2.61-5.21). B. microti was the most prevalent (1.79%, 95% CI: 1.38-2.31) species reported in ticks, while Ixodes scapularis recorded the highest infection rate (3.92%, 95% CI: 2.55-5.99). Larvae 4.18% (95% CI: 2.15-7.97) and females 4.08% (95% CI: 2.56-6.43) were the tick stage and sex with the highest infection rates. The presence of B. divergens, B. microti, and B. venatorum in tick vectors as revealed by the present study suggests possible risk of transmission of these pathogens to humans, especially occupationally exposed population. The control of tick vectors through chemical and biological methods as well as the use of repellants and appropriate clothing by occupationally exposed population are suggested to curtail the epidemiologic, economic, and public health threats associated with this emerging public health crisis.

The Global Emergence of Human Babesiosis

Babesiosis is an emerging tick-borne disease caused by intraerythrocytic protozoa that are primarily transmitted by hard-bodied (ixodid) ticks and rarely through blood transfusion, perinatally, and organ transplantation. More than 100 Babesia species infect a wide spectrum of wild and domestic animals worldwide and six have been identified as human pathogens. Babesia microti is the predominant species that infects humans, is found throughout the world, and causes endemic disease in the United States and China. Babesia venatorum and Babesia crassa-like agent also cause endemic disease in China. Babesia divergens is the predominant species in Europe where fulminant cases have been reported sporadically. The number of B. microti infections has been increasing globally in recent decades. In the United States, more than 2000 cases are reported each year, although the actual number is thought to be much higher. In this review of the epidemiology of human babesiosis, we discuss epidemiologic tools used to monitor disease location and frequency; demographics and modes of transmission; the location of human babesiosis; the causative Babesia species in the Americas, Europe, Asia, Africa, and Australia; the primary clinical characteristics associated with each of these infections; and the increasing global health burden of this disease.