Chemoprophylaxis (Imidocarb) against Babesia bigemina and Babesia argentina infections.

incoordination, and prostration. Signs of toxicosis were The cht:irprophylactic effects of imidocarb (3,3'milder with intramuscular or subcutaneous injections bis-'2-imidazolin-2-yl)-carbanilide dihydrochloride) of imidocarb. aga.nst bovine babesiasis were evaluated in 29 calves. T.',e compound had prophylactic and therapeutic prop­ '-jties in calves artificially and naturally infected with Babesia bigemina and Babesia argentinaof Colombian (South Americar) origin. Administered intramuscularly at the dose level of 2 mg./kg., imid3carb suppresced the The possibilities of chemoprophylaxis against bovine development of acute babesiasis in calves treated 46 babesiasis caused by Babesia divergc.nq were investigated clays previously and later exposed to a lethal (lose of by Ryley,' 0 B. argentina,by Newton and O'Sullivan," Babesia spp.-infected blood. Imidocarh lailed to protect and B. bigemina and B. argentina, by Callow and against A.'eplasma marginale infection. Calves treated McGregor. 5 These investigators found Ihat quinuroniuni derivatives had some prophylactic effect against Babesia intravenous0 with imidocarb at dose level of 2 mg./kg. spp., but not enough to prevent infection with these " and challenge inoculated 20 days later with a lethal (lose organisms in prophylactically treated cattle. Pipano' of Babesia spp.-infected blood were protected. For 90 reported that diamidine derivatives given at the (lose of days after challenge, none of the calves had Babesia 5 mg./kg. during the incubation peeiod of infection with spp. parasiternia, as determined by examination of Babesia berbera had the effect of decreasing the severity stained blood films and by subinoculation of blood into of disease; however, the administration of the drug 4 susceptihle splenectomized calves. Calves intravenously days before infection did not confer any protection. treated 21 (lays previously with 3 mg. of imidocarb per Further search for the development of a new drug kilogram resisted tick-borne chalietgc of Boophilus miwith longer prophylactic effect was obvioasly needed. croplus. This resistance was evidenced for 1.5 weeks of Beveridge2 reported that the compound now known as imidocarb (3,3'-bis(2-imidazolin-2-yl) -carhanilile dihy­ field exposure by negative results of examinations of drochloride)" had a greater babesiacidal effect and a stained blood films and death of nontreated calves from better chemoprophylactic index than did quinuronium, acute babesiasis. All calves treated with imidocarb and diamidine, and amicarbalide derivatives against Babesia subsequently exposed to blood or tick-borne Babesia rodhaini in mice and rats. Imidocarb was selected from spp. responded with an increase of complement-fixing a series of carbanilides on the basis of screening tests antibodies. against B. rodhainiby Schmidt et al.Imidocarb readily controlled very severe acute inFollowing these laboratory observations, imidocarh fectikns with B. bigemina and B. arge.,tina when the was found to have a high level of activity against B. compound was given at dose rates of 1 mg./kg. by both bigemina and B. argentina in Australian cattle. Callow rsubcutaneous routes. Signs of acute and McGregor' found that imidocarb cured (sterilized) intramuscular or sB. argentina at the (lose level of 2 mg./kg., but not toxicosis were observed in c-lves given intravenuas in at 1 mg./kg. It was found that B. bigemina was more jections of 3 mg./kg. Three calves ded, having signs ci susceptible to this compound. Imidocarb at the dose embarrassed respiration, oral respiration, excessive sallevel of 0.6 or more mg./kg. sterilized B. bigemina infec­ ivation, muscular fasciculations, urination, defecation, tions in splenectomized steers. The observations made by these authors that imidocarb had a prophylactic