Equine protozoal myeloencephalitis.
Abstract: Recent advances in the understanding of the parasite life cycle, epidemiology, clinical signs, diagnosis, treatment, and prevention of EPM are reviewed. The NAHMS Equine '98 study and a controlled retrospective study from The Ohio State University College of Veterinary Medicine identified a number of risk factors associated with development of the disease. The national annual incidence of EPM was 1% or less depending on the primary use of the animals. Increased disease risk was associated with age (1-5 and > 13 years of age), season (lowest in winter months and increasing with ambient temperature), previous stressful events, the presence of opossums, the use of nonsurface water drinking systems, and failure to restrict wildlife access to feed. Horses that received treatment were 10 times more likely to improve, and those that improved were 50 times more likely to survive. A number of recent studies confirmed that horses can be experimentally infected with S. neurona; however, large numbers of sporocysts are apparently necessary to achieve infection, and clinical signs and abnormal CNS histology are only seen inconsistently. Results suggest that CNS infection and positive CSF immunoblot findings may be transient phenomena among naturally infected horses. Although immunosuppression may be involved in the development of EPM, some element of the immune response seems to be necessary for the development of clinical signs. Use of the standard immunoblot test for the detection of anti-S. neurona antibodies in CSF continues to provide the most useful adjunct to a detailed neurologic examination for the diagnosis of EPM. Test sensitivity and specificity were 89% in 295 horses euthanatized because of neurologic disease, of which 123 were confirmed cases of EPM. The PPV was 85%, and the NVP was 92%. A number of promising new EPM treatments are under investigation. In addition to standard SDZ/PYR therapy, toltrazuril, ponazuril, diclazuril, and NTZ have shown promise as possible alternatives.
Publication Date: 2001-02-24 PubMed ID: 11219340DOI: 10.1016/s0749-0739(17)30086-xGoogle Scholar: Lookup
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- Journal Article
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Summary
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The research article is an exploration of the recent understandings related to Equine protozoal myeloencephalitis (EPM), a disease that affects horses, including its life cycle, symptoms, diagnosis, and prevention methods. The paper discusses factors associated with the development of the disease, and its treatment options.
Understanding Equine Protozoal Myeloencephalitis (EPM)
The study delves into the following matters:
- The life cycle of the parasite causing EPM, Sarcocystis neurona, is examined to provide further insight into how the disease is transmitted and progresses.
- The epidemiology of EPM, including risks factors such as the horse’s age (notably 1-5 and over 13 years), seasonal variations with lower risk in winter, stressful events, the presence of opossums, the type of water drinking systems, and wildlife access to feed. Understanding these risk factors can help in the prevention and management of EPM.
- Symptoms of the disease and how it is diagnosed are discussed, with an in-depth exploration of the value of the immunoblot test in detecting anti-S. neurona antibodies in Cerebrospinal Fluid (CSF) for diagnosis purposes.
- The prevention of EPM is considered, with a focus on restricting wildlife access to horse feed and using surface water drinking systems.
Treatment and Prognosis of EPM
- The study found that horses who received treatment are ten times more likely to show signs of improvement, with those who improve being 50 times more likely to survive, highlighting the critical importance of timely and effective treatment.
- Further, it was found that although large numbers of sporocysts are required to infect horses, clinical signs and abnormal Central Nervous System (CNS) histology are inconsistently observed. Therefore, it was suggested that positive CSF immunoblot findings and CNS infection might be temporary occurrences in naturally infected horses.
- Immunosuppression was proposed to play a role in the development of EPM, but some immune response appears required for the manifestation of clinical signs, indicating that the horse’s immune system’s modulation might have implications for disease development and progression.
- Several EPM treatments are being explored, including the standard SDZ/PYR therapy, toltrazuril, ponazuril, diclazuril, and NTZ, offering new hope for more effective treatments in the future.
Cite This Article
APA
MacKay RJ, Granstrom DE, Saville WJ, Reed SM.
(2001).
Equine protozoal myeloencephalitis.
Vet Clin North Am Equine Pract, 16(3), 405-425.
https://doi.org/10.1016/s0749-0739(17)30086-x Publication
Researcher Affiliations
- Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, Florida, USA.
MeSH Terms
- Animals
- Antibodies, Protozoan / analysis
- Antiprotozoal Agents / therapeutic use
- Coccidiosis / diagnosis
- Coccidiosis / drug therapy
- Coccidiosis / epidemiology
- Coccidiosis / veterinary
- Disease Outbreaks / veterinary
- Encephalomyelitis / diagnosis
- Encephalomyelitis / drug therapy
- Encephalomyelitis / epidemiology
- Encephalomyelitis / veterinary
- Horse Diseases / diagnosis
- Horse Diseases / drug therapy
- Horse Diseases / epidemiology
- Horses
- Neospora / immunology
- Sarcocystis / immunology
- Sarcocystosis / diagnosis
- Sarcocystosis / drug therapy
- Sarcocystosis / epidemiology
- Sarcocystosis / veterinary
- Seasons
Citations
This article has been cited 9 times.- Boos GS, Failing K, Colodel EM, Driemeier D, de Castro MB, Bassuino DM, Diomedes Barbosa J, Herden C. Glial Fibrillary Acidic Protein and Ionized Calcium-Binding Adapter Molecule 1 Immunostaining Score for the Central Nervous System of Horses With Non-suppurative Encephalitis and Encephalopathies. Front Vet Sci 2021;8:660022.
- Bowden GD, Land KM, O'Connor RM, Fritz HM. High-throughput screen of drug repurposing library identifies inhibitors of Sarcocystis neurona growth. Int J Parasitol Drugs Drug Resist 2018 Apr;8(1):137-144.
- Lewis SR, Ellison SP, Dascanio JJ, Lindsay DS, Gogal RM Jr, Werre SR, Surendran N, Breen ME, Heid BM, Andrews FM, Buechner-Maxwell VA, Witonsky SG. Effects of Experimental Sarcocystis neurona-Induced Infection on Immunity in an Equine Model. J Vet Med 2014;2014:239495.
- Foster SF, Martin P. Lower respiratory tract infections in cats: reaching beyond empirical therapy. J Feline Med Surg 2011 May;13(5):313-32.
- Hoane JS, Morrow JK, Saville WJ, Dubey JP, Granstrom DE, Howe DK. Enzyme-linked immunosorbent assays for detection of equine antibodies specific to Sarcocystis neurona surface antigens. Clin Diagn Lab Immunol 2005 Sep;12(9):1050-6.
- Howe DK, Gaji RY, Mroz-Barrett M, Gubbels MJ, Striepen B, Stamper S. Sarcocystis neurona merozoites express a family of immunogenic surface antigens that are orthologues of the Toxoplasma gondii surface antigens (SAGs) and SAG-related sequences. Infect Immun 2005 Feb;73(2):1023-33.
- Elsheikha HM, Mansfield LS. Sarcocystis neurona major surface antigen gene 1 (SAG1) shows evidence of having evolved under positive selection pressure. Parasitol Res 2004 Dec;94(6):452-9.
- Njoku CJ, Saville WJ, Reed SM, Oglesbee MJ, Rajala-Schultz PJ, Stich RW. Reduced levels of nitric oxide metabolites in cerebrospinal fluid are associated with equine protozoal myeloencephalitis. Clin Diagn Lab Immunol 2002 May;9(3):605-10.
- Liang FT, Granstrom DE, Zhao XM, Timoney JF. Evidence that surface proteins Sn14 and Sn16 of Sarcocystis neurona merozoites are involved in infection and immunity. Infect Immun 1998 May;66(5):1834-8.
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