agent of Equine protozoal myeloencephalitis
X0004 - Ultrasensitive qualitative detection of
by real time polymerase chain reaction
included in P0017
- equine protozoal myeloencephalitis panel and in
P0014 - equine neurological panel.
protozoal myeloencephalitis (EPM), also known as "equine
protozoa myelitis" is primarily caused by the apicomplexan
parasite Sarcocystis neurona. EPM is the most commonly diagnosed
neurologic disease of the horse in the US (Dubey et al., 2001).
Based on reported surveys from individual horse owners, EPM has
been labeled as the most important infectious disease facing the
equine industry ( NAHMS, 2001). Several surveys conducted in
Ohio have revealed greater than 50% (53.6%) of horses with
circulating S. neurona antibodies (Saville et al., 1997).
Opossums (Didelphis virginiana) serve as definitive hosts for S.
neurona in the US and are responsible for shedding infective S.
neurona sporocysts (Fenger et al., 1997; Dubey and Lindsay,
1998). However, it is not clear how opossums become infected
because hosts harboring sarcocysts have not been identified.
Recently, S. neurona sarcocysts have been identified in the
muscles of cats, raccoons, armadillos, sea otters and skunks.
Recent studies from Michigan and Florida have reported S.
neurona antibodies in 5% of domestic cats. A subsequent study
has confirmed domestic cats to be natural carriers of this
parasite (Stanek et al., 2003).
an aberrant intermediate host of S. neurona. Sporocysts are
eaten, pass into the small intestine and excyst there. The
infective stage of the organism, the sporozoite, then enters the
horse's blood stream. In some horses, these undergo several
replicative cycles in endothelial cells (in blood vessels),
becoming tachyzoites, and migrate to the central nervous system.
They replicate asexually within neurons and microglial cells
without forming tissue cysts. In the central nervous system of
the horse, they slowly divide and grow, gradually destroying the
nervous tissue, causing incoordination and the other clinical
signs that result from EPM. At this stage, the organism cannot
be transmitted to other horses. Because the organism does not
encyst in horse tissues, it cannot be transmitted to opossums,
even if an opossum were to eat the tissue. Therefore, the horse
is a dead end host for the protozoan.
Help confirm the disease causing agent
Shorten the time required to confirm a clinical
diagnosis of S. neurona
Help ensure that animal populations are free of
Early prevention of spread of this protozoan
Minimize personnel exposure to this protozoan
Safety monitoring of biological products that derive
from horses and other host animals
Dubey, J.P. and Lindsay, D.S. (1998) Isolation in
immunodeficient mice of Sarcocystis neurona from opossum (Didelphis
virginiana) faeces, and its differentiation from Sarcocystis
falcatula. Int. J. Parasitol. 28:1823–1828..
Lindsay, D.S., Saville, W.J.A., Reed, S.M., Granstrom, D.E. and
Speer, C.A. (2001) A review of Sarcocystis neurona and equine
protozoal myeloencephalitis (EPM). Vet. Parasitol. 95: 89–131.
Fenger, C.K., Granstrom, D.E., Langemeier, J.L. and Stamper,
S. (1997) Epizootic of equine protozoal myeloencephalitis on a
farm. J. Am. Vet. Med. Assoc 210: 923–927.
Equine Protozoal Myeloencephalitis (EPM) in the US. APHIS:VS,
CEAH, National Animal Health Monitoring System. USDA, Fort
Saville, W.J.A., Reed, S.M., Granstrom, D.E.,
Hinchcliff, K.W., Kohn, C.W., Wittum, T.E. and Stamper, S.
(1997) Prevalence of serum antibodies to Sarcocystis neurona in
horses residing in Ohio. J. Am. Vet. Med. Assoc. 210:519–524.
Stanek, J.F., Stich, R.W., Dubey, J.P., Reed, S.M., Njoku, C.J.,
Lindsay, D.S., Schmall, L.M., Johnson, G.K., LaFave, B.M. and
Saville, W.J. (2003) Epidemiology of Sarcocystis neurona
infections in domestic cats (Felis domesticus) and its
association with equine protozoal myeloencephalitis (EPM) case
farms and feral cats from a mobile spay and neuter clinic. Vet
Specimen requirements: 0.2 ml whole blood in EDTA (purple top) or ACD (yellow top)
tube, or 0.2 ml CSF, or 0.2 ml fresh, frozen or fixed CNS
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