First Description Of The Pathogenicity Of Babesia Vogeli In Experimentally Infected Dogs

Babesiosis is a tick-borne disease that occurs worldwide and is caused by protozoal hemoparasites belonging to the genus Babesia.There are a number of Babesia species that infect dogs,the most recognized being Babesia canis,B.vogeli,B.rossi and B.gibsoni.While B.vogeli is reported in dogs worldwide,clinical and laboratory data on infections is based on reports of naturally infected dogs.To provide reliable data on the clinical and laboratory abnormalities associated with acute and chronic infections in healthy dogs free of other tick-borne diseases,we experimentally infected dogs with a Chinese strain of B.vogeli collected from a Border Collie of Taizhou.All of the six infected Beagles,three of which were splenectomized,became infected with B.vogeli detected in blood smears taken the day following infection and the organism detected by FRET-qPCRs in most blood samples collected about every 4 days until the end of the experiment on day 114.To imitate natural infection,we also infected these infected Beagles with Ehrlichia canis cultivated in vitro on day 93.All splenectomized infected dogs were detected positive with B.vogeli by FRET-qPCR during the study,while after day 102,all non-splenectomized infected dogs were detected negative.All infected dogs were positive with E.canis by FRET-qPCR until the end of the study.After initial infection,all the infected dogs showed fever,partial anorexia and malaise that was more severe in the splenectomized dogs that did not gain weight for three weeks in the period after initial infection.Regenerative anemia,thrombocytopenia and decreased white blood cell counts were seen in all dogs but were more severe in the splenectomized dogs,of which two died during the period after initial infection.Following second infection on day 66,none of the dogs showed clinical signs and copy numbers did not change significantly.Laboratory values in the non-splenectomized dogs were relatively unchanged while in the splenectomized dog there was a temporary small increase in the platelet and white blood cell counts and a temporary slight worsening of the anemia.After super infection with E.canis on day 93,all infected dogs shown acute fever,anorexia and malaise.Apparent weight loss was detected in all infected dogs during the period.Anemia,thrombocytopenia and decreased white blood cell counts were seen again in all infected dogs.At the,end of the study,euthanasia was operated upon all the dogs.Cytokines,including GM-CSF,IFN?,KC-like,IP-10,IL-2,IL-6,IL-7,IL-8,IL-10,IL-15,IL-18,MCP-1,and TNF-?,were detected by commercial test kits and concentration of KC-like was detected increased in lung of infected dogs compared with that of control dogs.Histopathology was taken for tissues,including heart,liver,spleen,lung,kidney,lymph node,brain,muscle,stomach,duodenum,small intestine and bladder,in all dogs.Abnormalities were observed in lung,liver and brain in infected dogs,while no abnormalities were observed in other tissues in infected dogs and all tissues in.control dogs.In summary,our study shows dogs experimentally infected with B.vogeli show only mild clinical signs and laboratory abnormalities although they become chronically infected.In splenectomized dogs,however,severe life threatening signs may develop in a high percentage of dogs.