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Topic:Protozoa
Protozoa are single-celled eukaryotic organisms that can interact with horses in various ways, including as parasites. In equine health, protozoal infections can lead to significant diseases, such as equine protozoal myeloencephalitis (EPM), which is caused by the protozoan Sarcocystis neurona. These organisms can affect the central nervous system and other bodily systems, leading to a range of clinical symptoms in horses. Understanding the life cycle, transmission, and impact of protozoa is important for managing and preventing infections. This page compiles peer-reviewed research studies and scholarly articles that explore the biology, pathogenesis, and diagnostic approaches related to protozoal interactions in horses.
Experimental induction of equine protozoan myeloencephalitis (EPM) in the horse: effect of Sarcocystis neurona sporocyst inoculation dose on the development of clinical neurologic disease. The effect of inoculation dose of Sarcocystis neurona sporocysts on the development of clinical neurologic disease in horses was investigated. Twenty-four seronegative weanling horses were subjected to the natural stress of transport and then randomly assigned to 6 treatment groups of 4 horses each. Horses were then immediately inoculated with either 10(2), 10(3), 10(4), 10(5), or 10(6) S. neurona sporocysts or placebo using nasogastric tube and housed indoors. Weekly neurologic examinations were performed by a blinded observer. Blood was collected weekly for antibody determination by Western ...
Qualitative evaluation of selective tests for detection of Neospora hughesi antibodies in serum and cerebrospinal fluid of experimentally infected horses. Neospora hughesi is a newly recognized protozoan pathogen in horses that causes a myeloencephalitis similar to Sarcocystis neurona. There are no validated serologic tests using the gold standard sera that are currently available to detect specific N. hughesi antibodies and, thus, no tests available to detect antemortem exposure or estimate seroprevalence in the horse. The objectives of the present study were to establish a bank of gold standard equine sera through experimental infections with N. hughesi and to assess several serologic tests for the detection of related protozoan antibodies. Se...
Reactivity against Sarcocystis neurona and Neospora by serum antibodies in healthy French horses from two farms with previous equine protozoal myeloencephalitis-like cases. Sarcocystis neurona is considered a leading cause of equine protozoal myeloencephalitis (EPM), a common infectious neurological disease in horses in the Americas. EPM-like cases associated with S. neurona peptide reactive antibodies in Western blots were recently described in Normandy, France. In this report, antibodies reacting with S. neurona merozoites were detected using an agglutination assay at titers ranging from 50 to 500 in sera from 18/50 healthy horses from two farms with a previous EPM-like case. Higher values were found in older animals. Four out of six horses which traveled or st...
Cutaneous leishmaniosis in a horse in southern Germany caused by Leishmania infantum. This report describes a case of cutaneous leishmaniosis in a horse in southern Germany. Diagnosis is based on histopathology, immunohistochemistry and electron microscopy. The protozoan was identified as Leishmania infantum via PCR and restriction fragment length polymorphism. The horse did not show specific Leishmania antibodies. The lesions healed completely within 6 months without any specific treatment. Since neither the infected horse nor its dam had ever left their rural area, autochthonous infection in Germany cannot be excluded. Factors possibly influencing the epidemiological situatio...
Clinical diagnosis of equine protozoal myeloencephalitis (EPM). The research article is about the study and in-depth understanding of diagnosing equine protozoal myeloencephalitis (EPM), a disease that impacts horses’ neurological functions. Introduction The main focus of the research […]
Reduced levels of nitric oxide metabolites in cerebrospinal fluid are associated with equine protozoal myeloencephalitis. Equine protozoal myeloencephalitis (EPM) is a disease of horses that is primarily associated with infection with the apicomplexan Sarcocystis neurona. Infection with this parasite alone is not sufficient to induce the disease, and the mechanism of neuropathogenesis associated with EPM has not been reported. Nitric oxide (NO) functions as a neurotransmitter, a vasodilator, and an immune effector and is produced in response to several parasitic protozoa. The purpose of this work was to determine if the concentration of NO metabolites (NO(x)(-)) in the cerebrospinal fluid (CSF) is correlated with...
Characterization of monoclonal antibodies developed against Sarcocystis neurona. Equine protozoal myeloencephalitis (EPM), caused by a protozoal parasite infection of the central nervous system, is the most commonly diagnosed neurologic disease of horses in North America. In specific regions of the United States approximately 50% of the horse population is seropositive to Sarcocystis neurona. However, not all seropositive horses develop clinical signs. Detailed clinical examination, along with cerebrospinal fluid antibody evaluation are often used to diagnose EPM. Postmortem evaluation of the brain stem and spinal cord for histopathologic lesions compatible with nonsuppura...
Transforming growth factor beta concentrations and interferon gamma responses in cerebrospinal fluid of horses with equine protozoal myeloencephalitis. The following experiment was performed to test the hypothesis that transforming growth factor beta (TGF-beta) concentration varies in the cerebrospinal fluid and serum of horses with EPM and to determine if cerebrospinal fluid (CSF) alters the interferon-gamma (IFN-gamma) rersponse of equine peripheral blood mononuclear cells (PBMCs). The concentration of transforming growth factor-beta (TGF-beta2) was investigated in the serum and cerebrospinal fluid (CSF) of 18 horses (9 normal, 9 affected with equine protozoal myeloencephalitis [EPM]). The TGF-beta2 assay was validated in a group of 6 norma...
Risk factors associated with the presence of Sarcocystis neurona sporocysts in opossums (Didelphis virginiana). Sarcocystis neurona is the most important cause of equine protozoal myeloencephalitis (EPM) in horse in the Americas. The only known definitive host for this parasite in the United States is the opossum (Didelphis virginiana); however, despite the importance of the disease, the epidemiology of the parasite in the definitive host is poorly understood. To begin addressing these data gaps, potential risk factors were evaluated for their association with the presence of sporocysts of S. neurona in opossums live-trapped in March 1999 and November 1999 to May 2000. Sporocysts of S. neurona were foun...
Mice lacking the gene for inducible or endothelial nitric oxide are resistant to sporocyst induced Sarcocystis neurona infections. Equine protozoal myeloencephalitis (EPM) is a neurologic syndrome in horses from the Americas and is usually caused by infection with the apicomplexan parasite, Sarcocystis neurona. Little is known about the role of immunobiological mediators to this parasite. Nitric oxide (NO) is important in resistance to many intracellular parasites. We, therefore, investigated the role of inducible and endothelial NO in resistance to clinical disease caused by S. neurona in mice. Groups of interferon-gamma gene knockout (IFN-gamma-KO) mice, inducible nitric oxide synthase gene knockout (iNOS-KO) mice, endo...
The role of international transport of equine semen on disease transmission. Despite the numerous benefits of having the capability to transport semen internationally, there are serious potential ramifications if that semen is contaminated with a communicable disease. Bacteria: Many commensal bacteria colonize the exterior of the stallion penis and are not regarded as pathogenic. They may be cultured from an ejaculate. Alterations of the normal bacterial flora on the exterior genitalia may cause the growth of opportunistic bacteria such as Klebsiella pneumonia, Pseudomonas aeruginosa, Streptococcus zooepidemicus, which, if inseminated, may cause infertility in suscepti...
Suspected protozoal myeloencephalitis in a two-month-old colt. A two-month-old Appaloosa colt developed neurological signs shortly after birth involving deficits affecting cranial nerves IV, VII, VIII, IX, X and XII, and possibly nerve VI. The most likely differential diagnoses were congenital anomalies, meningoencephalitides, trauma or nutritional causes. The foal was investigated by the analysis of cerebrospinal fluid (CSF), electromyelography (EMG), brain auditory evoked responses, magnetic resonance imaging (MRI), peripheral nerve biopsy, and Western blot analysis for the presence of intrathecal antibodies to Sarcocystis neurona, the causative agent o...
The effects of pyrantel tartrate on Sarcocystis neurona merozoite viability. Sarcocystis neurona is the etiologic agent of equine protozoal myeloencephalitis, a neurologic disease of horses. The present study was designed to test the hypothesis that pyrantel tartrate can kill S. neurona merozoites growing in equine dermal cell culture. Sarcocystis neurona merozoites were exposed to a range of concentrations of pyrantel tartrate or sodium tartrate ranging from 0.001 to 0.01 M. Merozoites were then placed onto equine dermal cell cultures and incubated for 2 weeks to check for viability. At 1 and 2 weeks after inoculation, plaque counts were compared between treatments an...
Efficacy of ponazuril 15% oral paste as a treatment for equine protozoal myeloencephalitis. Equine protozoal myeloencephalitis (EPM) is a neurologic disease of horses most commonly caused by the protozoan parasite Sarcocystis neurona. Until recently the only treatment option was the combination of a sulfonamide with pyrimethamine. The present study was performed to assess the efficacy of ponazuril, an anticoccidial triazine-based compound, as a treatment for naturally occurring EPM. One hundred one horses with EPM were randomly allocated to treatment with ponazuril 15% oral paste at either 5 or 10 mg/kg body weight for 28 consecutive days. Horses were evaluated clinically and by anal...
Detection of Babesia caballi and Babesia equi in Dermacentor nuttalli adult ticks. Ticks play an important role in human and veterinary medicine particularly due to their ability to transmit protozoan pathogens. In this study we have demonstrated that polymerase chain reaction (PCR) and nested PCR methods enabled detection of Babesia caballi and Babesia equi in field isolates of Dermacentor nuttalli adult ticks from Mongolia. Primers specific for 218 bp fragment merozoite antigen 1 (EMA-1) gene of B. equi successfully amplified products from all samples of D. nuttalli adult ticks while primers for the 430 bp fragment product from BC48 gene of B. caballi amplified products fr...
Rapid identification of tissue micro-organisms in skin biopsy specimens from domestic animals using polyclonal BCG antibody. Immunostaining with polyclonal anti-Mycobacterium bovis (BCG) was evaluated as a single screening method for the histological identification of micro-organisms in skin biopsy specimens from various veterinary species. Confirmed archival cases infected with Mycobacteria, Nocardia, Actinobacillus, Actinomyces, Streptococcus/Staphylococcus, Dermatophilus, spirochetes, Blastomyces, Coccidioides, Cryptococcus, Histoplasma, dermatophytes, Malassezia, Sporothrix, Leishmania, Pythium, phaeohyphomycetes and Prototheca organisms were selected. A total of 70 skin biopsy specimens from the dog, cat, horse...
A review of Sarcocystis neurona and equine protozoal myeloencephalitis (EPM). Equine protozoal myeloencephalitis (EPM) is a serious neurological disease of horses in the Americas. The protozoan most commonly associated with EPM is Sarcocystis neurona. The complete life cycle of S. neurona is unknown, including its natural intermediate host that harbors its sarcocyst. Opossums (Didelphis virginiana, Didelphis albiventris) are its definitive hosts. Horses are considered its aberrant hosts because only schizonts and merozoites (no sarcocysts) are found in horses. EPM-like disease occurs in a variety of mammals including cats, mink, raccoons, skunks, Pacific harbor seals, p...
Direct agglutination test for the detection of antibodies to Sarcocystis neurona in experimentally infected animals. Equine protozoal myeloencephalitis (EPM) is a serious neurological disease of horses in the Americas. The apicomplexan protozoan most commonly associated with EPM is Sarcocystis neurona. A direct agglutination test (SAT) was developed to detect antibodies to S. neurona in experimentally infected animals. Merozoites of the SN6 strain of S. neurona collected from cell culture were used as antigen and 2-mercaptoethanol was added to the antigen suspension to destroy IgM antibodies when mixed with test sera. Mice fed sporocysts of S. speeri or S. falcatula-like sporocysts from opossums did not sero...
Comparison of Sarcocystis neurona isolates derived from horse neural tissue. Sarcocystis neurona is a protozoan parasite that can cause neurological deficits in infected horses. The route of transmission is by fecal-oral transfer of sporocysts from opossums. However, the species identity and the lifecycle are not completely known. In this study, Sarcocystis merozoites from eight isolates obtained from Michigan horses were compared to S. neurona from a California horse (UCD1), Sarcocystis from a grackle (Cornell), and five Sarcocystis isolates from feral opossums from Michigan. Comparisons were made using several techniques. SDS-PAGE analysis with silver staining showed...
Initiation of a Sarcocystis neurona expressed sequence tag (EST) sequencing project: a preliminary report. To accelerate genetic and molecular characterization of Sarcocystis neurona, the primary causative agent of equine protozoal myeloencephalitis (EPM), a sequencing project has been initiated that will generate approximately 7000-8000 expressed sequence tags (ESTs) from this apicomplexan parasite. Poly(A)(+) RNA was isolated from culture-derived S. neurona merozoites, and a cDNA library was constructed in a unidirectional lambda phage cloning vector. Sixty phage clones were randomly picked from the library, and the cDNA inserts were amplified from these clones using the T3 and T7 primers that fl...
In vitro quantitative analysis of (3)H-uracil incorporation by Sarcocytis neurona to determine efficacy of anti-protozoal agents. Parasite-specific incorporation of (3)H-uracil was used to assess the replication of Sarcocystis neurona, a protozoal parasite associated with equine protozoal myeloencephalitis (EPM). Anti-protozoal drugs, pyrimethamine (0.01, 0.1 and 1.0microg/ml PYR), sulfadiazine (5microg/ml; SDZ), sulfamethoxazole (5microg/ml; SMZ), diclazuril (100ng/ml; DCZ), atovaquone (0.04ng/ml; ATQ), tetracycline (5microg/ml; TET) and the herbicide glyphosate (1.5 and 4.5mM; GLY) were studied with varying S. neurona parasite densities (2x10(1)-1.2x10(6)merozoites/well). A microtiter plate format was used to test thes...
Sporocyst size of isolates of Sarcocystis shed by the Virginia opossum (Didelphis virginiana). The Virginia opossum (Didelphis virginiana) is a definitive host for multiple Sarcocystis species including Sarcocystis neurona, one of the causative agents of equine protozoal myeloencephalitis (EPM), a severe, neuromuscular disease of horses. Size and morphologic characteristics of isolates of Sarcocystis shed by the opossum were examined to determine if differences were useful in discriminating between the isolates and/or species. Collections of sporocysts from 17 opossums were molecularly characterized and measured using an ocular micrometer. The mean sporocyst size of isolates of S. neuro...
A random amplified polymorphic DNA polymerase chain reaction technique that differentiates between Neospora species. Neospora caninum is a recently described coccidial parasite that was first isolated from a dog in 1988 and has subsequently been shown to infect a wide range of mammals. Neospora hughesi, a new species of this genus, has recently been isolated from the spinal cord of horses showing clinical signs of equine protozoal myeloencephalitis. The random amplified polymorphic DNA polymerase chain reaction technique is capable of differentiating between N. caninum and N. hughesi.
Completion of the life cycle of Sarcocystis neurona. Sarcocystis neurona is the most important cause of a neurologic disease in horses, equine protozoal myeloencephalitis (EPM). The complete life cycle of S. neurona, including the description of sarcocysts and intermediate hosts, has not been completed until now. Opossums (Didelphis spp.) are definitive hosts, and horses and other mammals are aberrant hosts. In the present study, laboratory-raised domestic cats (Felis domesticus) were fed sporocysts from the intestine of a naturally infected opossum (Didelphis virginiana). Microscopic sarcocysts, with a maximum size of 700 x 50 microm, developed...
Evaluation of risk factors associated with clinical improvement and survival of horses with equine protozoal myeloencephalitis. To investigate risk factors for use in predicting clinical improvement and survival of horses with equine protozoal myeloencephalitis (EPM). Methods: Longitudinal epidemiologic study. Methods: 251 horses with EPM. Methods: Between 1992 and 1995, 251 horses with EPM were admitted to our facility. A diagnosis of EPM was made on the basis of neurologic abnormalities and detection of antibody to Sarcocystis neurona or S neurona DNA in CSF. Data were obtained from hospital records and through telephone follow-up interviews. Factors associated with clinical improvement and survival were analyzed, us...
Determination of the activity of ponazuril against Sarcocystis neurona in cell cultures. The present study examined the efficacy of ponazuril in inhibiting merozoite production of Sarcocystis neurona in cell cultures. Ponazuril inhibited merozoite production by more that 90% in cultures of S. neurona treated with 1.0 microg/ml ponazuril and greater than 95% inhibition of merozoite production was observed when infected cultures were treated with 5.0 microg/ml ponazuril. Ponazuril may have promise as a therapeutic agent in the treatment of S. neurona induced equine protozoal myeloencephalitis (EPM) in horses.
Inoculation of Sarcocystis neurona merozoites into the central nervous system of horses. Equine protozoal myeloencephalitis (EPM) is a neurologic syndrome in horses from the Americas and is usually caused by infection with the apicomplexan parasite, Sarcocystis neurona. A horse model of EPM is needed to test the efficacy of chemotherapeutic agents and potential vaccines. Five horses that were negative for antibodies to S. neurona in their serum and cerebrospinal fluid (CSF) were injected in the subarachnoid space with living merozoites of the SN2 isolate of S. neurona. None of the horses developed clinical disease or died over a 132-day observation period. All five horses develope...
