Babesia Genome Sequencing Projects
The microscope used by
Smith and Kilbourne
is a tick-transmitted protozoan
parasite of cattle that infects and results in the destruction of erythrocytes,
causing severe anemia. Smith and Kilbourne’s classic work in the late 1800’s to
elucidate the cause and mechanism of transmission of the Texas Fever agent was
the first definitive demonstration of a vector-borne protozoan disease.
B. bovis and B.
are important causative agents of bovine babesiosis
in tropical and subtropical regions of the world,
while Babesia divergens is more common in
temperate climates. Babesiosis was a significant
problem in the southern US till the 1940’s when it
was controlled by eradication of the tick vectors by
intensive acaricide dipping of cattle. However, the
tick vectors are present in a buffer zone along the
Rio Grande, in Mexico, and in US territories, and
pose the threat of continual reemergence into the US
as evidenced by occasional outbreaks of babesiosis
in the border region. Emerging acaracide resistance
of vector ticks in Mexico is a significant concern,
since re-introduction of babesiosis into the US
likely will occur via infected ticks. It is
estimated that the first year cost of controlling
vector ticks alone should they be introduced into
the US is over $1.3 billion. There is currently no
babesial vaccine licensed for use in the US, and
development of a vaccine is a high priority.
These apicomplexan parasites are related to
Plasmodium spp (the causative agents of
malaria) and Theilera parva (which causes
theileriosis). Aside from being an agriculturally
important pathogen, B. bovis resides within
an important evolutionary branch within the
phylogenic tree. Organisms from this branch of the
tree have added substantially to our understanding
of biology by the discovery of telomeres, catalytic
RNA, the calvin cycle, GPI anchoring, and
trans-splicing among others.
The tree of life showing the position of Babesia within the three
|Babesia bovis infected erythrocyte stained with monoclonal
antibodies against MSA1 (green) and RAP1 (red). DNA is stained with DAPI
(blue). Image courtesy of Juan Mosqueda.
The T2Bo Genome sequence
The Texas T2Bo strain was selected for
genomic sequencing because the history of this isolate is well documented: it is
known to be virulent, and it is tick transmissible. A combined clone by clone
and whole genome shotgun approach was used to obtain the complete genome
sequence for this organism. The resulting sequence contains 9 contigs which may
be downloaded by following the links below.
Downloads (all files
The T2Bo genome sequence papers
Brayton, K. A., A. O.T. Lau, D. R. Herndon, L.
Hannick, L. S. Kappmeyer, S. J. Berens, S. L. Bidwell, W. C. Brown, J. Crabtree,
D. Fadrosh, T. Feldblum, H. A. Forberger, B. J. Haas, J. M. Howell, H. Khouri,
H. Koo, D. J. Mann, J. Norimine, I. T. Paulsen, D. Radune, Q. Ren, R. K. Smith
Jr., C. E. Suarez, O. White, J. R. Wortman, D. P. Knowles Jr, T. F. McElwain,
and V. M. Nene. Genome sequence of Babesia bovis
analysis of apicomplexan hemoprotozoa. PLOS Pathogens. 3: 1401-1413. 2007.
E. H. Roalson, T. F. McElwain, K. A. Brayton, D. P.
Knowles, and A. O. T. Lau. Babesia bovis:
a comprehensive phylogenetic
analysis of plastid-encoded genes supports green algal origin of apicoplasts.
. 123: 236-243. 2009.
Other B. bovis strains
The completed T2Bo sequence can now be used to
scaffold genome assemblies of other Babesia bovis isolates that are generated
with next generation sequencing technologies. We are generating paired
sequences for virulent B. bovis strains and their attenuated counterparts,
generated by rapid, successive inoculation in cattle.
BLAST Babesia contigs
BLAST on local server
has been named Piroplasma
(1901), Nuttallia equi
(1986), a classification that has not been formally
adopted. B. equi causes equine piroplasmosis, a disease that results in
restricted movement of horses worldwide. The disease occurs throughout the
tropical and subtropical areas of the world, with endemic areas in many parts of
Europe, Asia, Arabia, South and Central America and Africa. B. equi
transmitted by species of ixodid ticks of the genera Dermacentor,
. The Florida isolate, also known as the USDA
strain, was sequenced in collaboration with the J. Craig Venter Institute (JCVI)
using a whole genome shotgun approach. The resulting sequence contains 10
contigs as pictured below. Please note the order of the internal contigs of
chromosome 4 are not known.
These projects are funded by the USDA Agricultural
Research Service - Animal Disease Research Unit (ARS-ADRU),
USDA Formula Funds, The Wellcome Trust and the CVM
Animal Health Research Center.