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Description:
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Babesia species have a worldwide distribution , affecting a wide range of mammalian
hosts . The major route of transmission is inoculation by an infected Ixodid tick . Babesia
species of major economic concern are those that cause bovine and equine babesiosis .
Historically , bovine Babesia species , Babesia bovis and Babesia bigemina caused
significant economic losses in the United States in the 1860â  s , as thousands of cattle
died . Also , outbreaks of equine babesiosis , caused by Babesia equi or Babesia caballi ,
have occurred in the United States resulting in the death of some horses and millions of
dollars in losses . A constant risk of reinfection with bovine and equine Babesia species
exists , as stray and smuggled animals from Mexico , where bovine babesiosis is endemic ,
may carry infected ticks as they cross the border , and , thousands of horses from B . equiand
B . caballi -endemic regions are imported through Florida every year .
Vaccines have been developed for a number of Babesia species , none of which result
in sterile immunity . The live attenuated vaccine is the most commonly used vaccine
against Babesia species . However , the basis for the vaccine is to maintain a carrier state in order to prevent disease . Other vaccine designs have been developed to invoke
protection without a carrier state but have been unsuccessful .
It has been shown that the cysteine protease is important in the life cycle of a number
of parasitic organisms , making it a good target for vaccine development . The vaccine
design for this study incorporated the cysteine protease of Babesia microti . Babesia
microti naturally infects Peromyscus leucopus (white -footed mouse ) and is the major
cause of human babesiosis in the United States . Using B . microti in the vaccine design
allowed for the use of a mouse model to determine whether the cysteine protease of
other economically important Babesia species may make a good vaccine target . The
vaccine design incorporated a prime -boost strategy , priming with DNA encoding the
cysteine protease and boosting two times with either DNA encoding the cysteine
protease or cysteine protease peptide , followed by parasite challenge . Analysis of daily
percent parasitemias , packed cell volume , and seroconversion of all groups revealed that
a protective immune response against B . microti was not elicited by this vaccine strategy . |