Potomac horse fever
formerly known as
also know as equine monocytic ehrlichiosis)
B0028 - Ultrasensitive qualitative detection of
by real time polymerase chain reaction.
included in P0015 - equine
GI/diarrhea PCR panel
is a disease caused by obligatory intracellular bacteria of the
that affects a variety of animals including humans. Several
species are assigned to this genus; those for which the vectors
are known are transmitted by ixodid ticks. Most
predominantly white blood cells of their vertebrate hosts; the
one exception is Ehrlichia
platys which infects blood platelets of dogs. The
organisms appear in clusters known as morulae in the cytoplasm
of infected cells.
Traditionally, these organisms were classified as agranulocytic
or granulocytic based on the cells they infect. With the advent
of molecular detection methods and RNA sequencing techniques,
these organisms have been reclassified with different names. For
example, Ehrlichia risticii
is now classified as
Neorickettsia risticii and
Ehrlichia platys is
now Anaplasma platys.
and human granulocytic Ehrlichial agent have now been confirmed
to be the same species and have been reclassified as
causes Potomac horse fever, also known as equine monocytic
ehrlichiosis. Natural infections have also been reported in
dogs, with symptoms resembling
E. canis infection.
N. risticii is
very closely related to
horse fever is prevalent in the Midwestern and Northeastern
United States and has also been reported in Europe and India.
Mode of transmission is unknown, but recent reports suggest oral
transmission. Transplacental transmission of this agent has also
been reported. Infections are more prevalent during summer
months and have a 5 to 30% mortality rate. Clinical signs of
infection are pyrexia, anorexia, enteritis, watery diarrhea,
colic and laminitis. Hematological findings include
thrombocytopenia and leucopenia.
detection of E. risticii
is not only insensitive but also not very specific because of
cross-reactivity with other
Ehrlichia organisms. Detection by culture is slow
and also lacks sensitivity. Detection of the pathogen by PCR is
sensitive and highly specific (Mott et al., 1997).
Help confirm the disease causing agent
Shorten the time required to confirm a clinical
diagnosis of N. risticii
Help ensure that horse populations are free of
Early prevention of spread of this bacterium
Minimize personnel exposure to this bacterium
Safety monitoring of biological products that derive
Mott, J., Rikihisa, Y., Zhang, Y., Reed, S.M. and Yu, C.Y.
(1997) Comparison of PCR and culture to the indirect
fluorescent-antibody test for diagnosis of Potomac horse fever.
J Clin Microbiol. 35:2215-9.
Specimen requirements: 0.2 ml whole blood in EDTA (purple top) or ACD (yellow top)
tube, or fecal swab or 0.2 ml feces.
types other than those listed here, please call to confirm
specimen acceptability and shipping instructions.
specimen types, if there will be a delay in shipping, or during
very warm weather, refrigerate specimens until shipped and ship
with a cold pack unless more stringent shipping requirements are
specified. Frozen specimens should be shipped so as to remain
frozen in transit. See shipping
instructions for more information.
2 business days
real time PCR