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Home / Equine Research Bank / Clin Diagn Lab Immunol / Infection of immunodeficient horses with Sarcocystis neurona...
Clinical and diagnostic laboratory immunology2004; 11(6); 1134-1139; doi: 10.1128/CDLI.11.6.1134-1139.2004

Infection of immunodeficient horses with Sarcocystis neurona does not result in neurologic disease.

Abstract: Equine protozoal myeloencephalitis is a progressive neurologic disease of horses most commonly caused by infection with the apicomplexan parasite Sarcocystis neurona. Factors affecting neuroinvasion and neurovirulence have not been determined. We investigated the pathogenesis of infection with S. neurona in horses with severe combined immune deficiency (SCID). Two immunocompetent (IC) Arabian horses and two Arabian horses with SCID were infected orally with 5 x 10(5) sporocysts of S. neurona. Four IC horses and one SCID horse were infected intravenously (i.v.) with 5 x 10(8) merozoites of the WSU-1 isolate of S. neurona. Despite prolonged parasitemia and persistent infection of visceral tissues (skeletal muscle, cardiac muscle, lung, liver, and spleen) as demonstrated by PCR and culture, SCID horses did not develop neurologic signs after oral or i.v. infection. S. neurona was undetectable in the neuronal tissues of SCID horses by either PCR, immunohistochemistry, or culture. In contrast, although parasitemia was undetectable in orally infected IC horses and of only short duration in i.v. infected IC horses, four of six IC horses developed neurologic signs. S. neurona was detectable by PCR and/or culture of neural tissue but not visceral tissue of IC horses with neurologic disease. Infected SCID horses are unable to clear S. neurona from visceral tissues, but the infection does not result in neurologic signs; in contrast, IC horses rapidly control parasitemia and infection of visceral tissues but frequently experience neuroinvasion and exhibit clinical signs of neurologic disease.
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Publication Date: 2004-11-13 PubMed ID: 15539518PubMed Central: PMC524751DOI: 10.1128/CDLI.11.6.1134-1139.2004Google Scholar: Lookup
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  • Journal Article
  • Research Support
  • Non-U.S. Gov't

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

This study is focused on understanding why horses infected with the parasite Sarcocystis neurona don’t suffer from nerve disease even when their immune system is severely compromised.

Objectives of the Study

  • The objective of the study was to understand the pathogenesis of an infection with Sarcocystis neurona, a parasite which commonly causes Equine protozoal myeloencephalitis (EPM), a progressive neurologic disease in horses.
  • The researchers aimed to determine the factors leading to neuroinvasion (penetration of the nervous system by an infectious agent) and neurovirulence (the degree to which an organism can cause disease in the nervous system).
  • They focused their investigation on horses with severe combined immune deficiency (SCID) to see how their lack of proper immune response might impact the progression of the infection and the development of the disease.

Methods of the Study

  • Two immunocompetent (IC) Arabian horses (those having a normal immune system) and two Arabian horses with SCID were orally infected with a certain amount of sporocysts of S. neurona, the infective form of the parasite.
  • Similarly, four IC horses and one SCID horse were infected intravenously with merozoites (another life stage of the parasite) of the same S. neurona species.

Observations and Results

  • Despite prolonged parasitemia (presence of parasites in the blood) and persistent infection of visceral tissues (like skeletal muscle, cardiac muscle, lung, liver, and spleen), the SCID horses did not develop neurologic signs after either oral or intravenous infection.
  • The presence of S. neurona in the neuronal tissues of SCID horses could not be detected by PCR, immunohistochemistry, or culture methods; suggesting the parasite does not invade the nervous system in these immune-compromised animals.
  • In contrast, IC horses, which quickly controlled parasitemia and the infection of their visceral tissues, often did show neuroinvasion by the parasite and developed neurologic signs of disease. S. neurona was detectable in the neural tissues but not the visceral tissues of these horses.

Conclusions

  • The key conclusion of the study is that while SCID horses, with their impaired immune system, can’t clear S. neurona from their visceral tissues, they do not suffer from nerve disease, because the parasite does not invade their nervous system.
  • In contrast, IC horses, even with their ability to control the parasitemia and visceral infection, often experience neuroinvasion, leading to nervous system disease. The reasons for this different disease progression in IC horses need further investigation.

Cite This Article

APA
Sellon DC, Knowles DP, Greiner EC, Long MT, Hines MT, Hochstatter T, Tibary A, Dame JB. (2004). Infection of immunodeficient horses with Sarcocystis neurona does not result in neurologic disease. Clin Diagn Lab Immunol, 11(6), 1134-1139. https://doi.org/10.1128/CDLI.11.6.1134-1139.2004

Publication

Clinical and diagnostic laboratory immunology
ISSN: 1071-412X
NlmUniqueID: 9421292
Country: United States
Language: English
Volume: 11
Issue: 6
Pages: 1134-1139

Researcher Affiliations

Sellon, Debra C
  • Department of Veterinary Clinical Sciences, Washington State University, Pullman, WA 99163, USA. dsellon@vetmed.wsu.edu
Knowles, Donald P
    Greiner, Ellis C
      Long, Maureen T
        Hines, Melissa T
          Hochstatter, Tressa
            Tibary, Ahmed
              Dame, John B

                MeSH Terms

                • Animals
                • Central Nervous System Protozoal Infections / parasitology
                • Central Nervous System Protozoal Infections / pathology
                • Central Nervous System Protozoal Infections / veterinary
                • Encephalomyelitis / parasitology
                • Encephalomyelitis / pathology
                • Encephalomyelitis / veterinary
                • Horse Diseases / parasitology
                • Horse Diseases / pathology
                • Horses
                • Parasitemia / pathology
                • Parasitemia / veterinary
                • Sarcocystis
                • Sarcocystosis / pathology
                • Sarcocystosis / veterinary
                • Severe Combined Immunodeficiency / parasitology
                • Severe Combined Immunodeficiency / pathology
                • Severe Combined Immunodeficiency / veterinary

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                Citations

                This article has been cited 2 times.
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