Babesiosis is a tick-borne disease caused by intraerythrocytic protozoa. Despite the increasing acknowledgement that babesiosis represents a threat to animal and human health, to date there have been few studies focusing on the disease in the Republic of Korea (ROK). In the present study, we report a Babesia capreoli infection in an Ixodes nipponensis tick obtained from a Korean water deer (Hydropotes inermis argyropus). The tick was identified with polymerase chain reaction analysis as I. nipponensis (Japanese hard tick). A phylogenetic analysis based on the 18S rRNA gene sequences revealed that the isolate found in I. nipponensis belonged to the B. capreoli lineage and was distinct from the Asian, European, and North American lineages of Babesia divergens. Although our isolate belonged to the B. capreoli lineage it did not form a cluster with others isolates in the same lineage; this may be due to differences in the tick species that transmit B. capreoli or in the host species. We were unable to identify the reservoir host for our case of B. capreoli transmission, though regional ticks may be the primary vector. This study confirms the presence of B. capreoli in the ROK, and its presence suggests that further study is warranted to determine its prevalence and pathogenicity in wild and domesticated animals.

Tick salivary secretion during blood-feeding is crucial for successful tick feeding. Control of salivary secretion involves dopamine, which is the most potent inducer of tick salivation. Dopamine activates salivation by orchestrating two different physiological responses through two distinct dopamine receptors. In addition, the study demonstrated that two different types of cells in the salivary gland acini are responsible for each of the diverging physiological pathways: epithelial cells for inward fluid transport and myoepithelial cells for expelling fluid out through the acinar ducts. We were further interested in the downstream physiology of the dopamine receptors. A candidate gene (Na/K-ATPase), which is highly expressed in the salivary glands, was investigated. Immunoreactivity revealed that Na/K-ATPase is expressed in epithelial cells of acini. Ouabain, a Na/K-ATPase blocker, significantly suppressed both dopamine induced inward fluid transport and dopamine induced salivation in a dose-dependent manner. We measured the salivary contents to determine Na, K, and Cl ion, and protein concentrations. Treatment of ouabain at the low dose produced hyperosmolar saliva, but with same amount of protein as the control saliva. The results suggest that ouabain-sensitive Na/K-ATPase is the main downstream pathway for dopamine response in the epithelial cells of salivary gland for water transport, but not for protein secretion.