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Sarcocystis falcatula from passerine and psittacine birds: synonymy with Sarcocystis neurona, agent of equine protozoal myeloencephalitis.
Abstract: Equine protozoal myeloencephalitis (EPM) is a neurologic disease of horses caused by Sarcocystis neurona. The horse is a dead-end host for S. neurona and the definitive and intermediate hosts have not previously been identified. We hypothesized that S. neurona is actually Sarcocystis falcatula, a parasite that cycles in nature between Virginia opossums (Didelphis virginiana) and any of a variety of avian intermediate hosts. We extracted DNA from S. falcatula sarcocysts in the muscle of a brown-headed cowbird (Molothrus ater) and from schizonts in a fixed specimen of lung from a Moluccan cockatoo (Cacatua moluccensis). Three segments of the small subunit ribosomal RNA (SSURNA) gene, containing a total of 742 nucleotides, were amplified by the polymerase chain reaction, sequenced, and compared with the SSURNA sequence from two isolates of S. neurona. The S. falcatula sequence was identical to the sequence of the S. neurona isolate UCD-1 and differed in only 3 positions from isolate SN5. Recent evidence, also based on SSURNA sequences, implicates the opossum as the definitive host of S. neurona. Based on the SSURNA gene sequences S. falcatula and S. neurona are synonymous, thus the parasite cycles between opossums and birds maintaining a reservoir of the organism from which horses can be infected.
Publication Date: 1995-12-01 PubMed ID: 8544067 The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Comparative Study
- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The research article delves into the investigation that the parasite causing Equine protozoal myeloencephalitis (EPM) in horses, Sarcocystis neurona, is in fact synonymous with Sarcocystis falcatula, which is known to cycle between opossums and birds. Through an analysis of the small subunit ribosomal RNA (SSURNA) sequences from both parasites, the researchers confirmed the synonymy, pointing out the potential reservoirs of the organism that can infect horses.
Context and Hypothesis
- Equine protozoal myeloencephalitis (EPM) is a neurological disease that primarily affects horses. It is identified to be caused by a parasitic infection, specifically by the parasite Sarcocystis neurona. However, the definitive and intermediate hosts of this parasite have not been fully identified before this research.
- This study sprouted from the hypothesis that the Sarcocystis neurona parasite is indeed the same as Sarcocystis falcatula, which is known for cycling between Virginia opossums as definitive hosts and various avian species as intermediate hosts.
Research Methods
- DNA was extracted from sarcocysts of Sarcocystis falcatula found in the muscle of a brown-headed cowbird and from schizonts in a fixed lung specimen from a Moluccan cockatoo.
- Segments of the small subunit ribosomal RNA (SSURNA) gene were amplified using the polymerase chain reaction (PCR) and sequenced. This genetic material was compared with the SSURNA sequence from two separate isolates of the Sarcocystis neurona parasite.
Findings
- The researchers found that the SSURNA sequence from Sarcocystis falcatula was identical to one of the Sarcocystis neurona isolates and only differed in three positions from the other Sarcocystis neurona isolate.
- Based on these findings, the researchers concluded that Sarcocystis neurona and Sarcocystis falcatula are synonymous, highlighting that both parasites are essentially the same species.
- This insight provides new understanding to the life cycle of the parasite causing EPM, showing that it can cycle between opossums and birds, establishing such animals as potential reservoirs of the organism.
- The findings could have further implications in the prevention and control of the transmission of EPM to horses.
Cite This Article
APA
Dame JB, MacKay RJ, Yowell CA, Cutler TJ, Marsh A, Greiner EC.
(1995).
Sarcocystis falcatula from passerine and psittacine birds: synonymy with Sarcocystis neurona, agent of equine protozoal myeloencephalitis.
J Parasitol, 81(6), 930-935.
Publication
Researcher Affiliations
- Department of Pathobiology, College of Veterinary Medicine, University of Florida, Gainesville 32611, USA.
MeSH Terms
- Animals
- Base Sequence
- Birds / parasitology
- Encephalitis / veterinary
- Horse Diseases
- Horses
- Host-Parasite Interactions
- Molecular Sequence Data
- Psittaciformes / parasitology
- RNA, Ribosomal / genetics
- Sarcocystis / classification
- Sarcocystis / genetics
- Sarcocystis / ultrastructure
- Sarcocystosis / epidemiology
- Sarcocystosis / veterinary
- Sequence Homology, Nucleic Acid
- Species Specificity
Citations
This article has been cited 4 times.- Dubey JP, Howe DK, Furr M, Saville WJ, Marsh AE, Reed SM, Grigg ME. An update on Sarcocystis neurona infections in animals and equine protozoal myeloencephalitis (EPM). Vet Parasitol 2015 Apr 15;209(1-2):1-42.
- Elsheikha HM, Saeed MA, Fitzgerald SD, Murphy AJ, Mansfield LS. Effects of temperature and host cell type on the in vitro growth and development of Sarcocystis falcatula. Parasitol Res 2003 Sep;91(1):22-6.
- Dubey JP, Alić A, Hodžić A, Lopez-Flores J, Baneth G. Hepatozoon infections in domestic and wild Carnivora: etiology, prevalence, clinical disease, diagnosis and treatment, and redescription of Hepatozoon silvestris, H. martis, and H. ursi. Parasit Vectors 2025 Sep 24;18(1):391.
- Šukytė T, Butkauskas D, Juozaitytė-Ngugu E, Švažas S, Prakas P. Molecular Confirmation of Accipiter Birds of Prey as Definitive Hosts of Numerous Sarcocystis Species, including Sarcocystis sp., Closely Related to Pathogenic S. calchasi. Pathogens 2023 May 23;12(6).
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