Evaluation of risk factors associated with clinical improvement and survival of horses with equine protozoal myeloencephalitis

OBJECTIVE: To investigate risk factors for use in predicting clinical improvement and survival of horses with equine protozoal myeloencephalitis (EPM). DESIGN: Longitudinal epidemiologic study. ANIMALS: 251 horses with EPM. PROCEDURE: 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, using multivariable logistic regression. RESULTS: The likelihood of clinical improvement after diagnosis of EPM was lower in horses used for breeding and pleasure activities. Treatment for EPM increased the probability that a horse would have clinical improvement. The likelihood of survival among horses with EPM was lower among horses with more severe clinical signs and higher among horses that improved after EPM was diagnosed. CONCLUSIONS AND CLINICAL RELEVANCE: Treatment of horses with EPM is indicated in most situations; however, severity of clinical signs should be taken into consideration when making treatment decisions. Response to treatment is an important indicator of survival.     

Risk factors for owner-reported occurrence of equine protozoal myeloencephalitis in the US equine population

BACKGROUND: Equine protozoal myeloencephalitis (EPM) is a serious and often fatal neurologic disease of horses, but few studies have investigated risk factors. OBJECTIVES: To evaluate operation- and individual-level factors associated with likelihood of the occurrence of EPM. ANIMALS: Data were collected as part of a study of the US equine industry from 1,178 operations representing 83.9% of horses and 51.6% of operations with > or =3 horses in 28 states. METHODS: Probability-based sampling was used to enroll representative operations in a cross-sectional study. Interviews were conducted to collect information regarding health and management of horses. A nested case-control study was used to investigate risk factors among individual horses. Interview data were combined with climate data, human population density, and opossum regional ecology categories. Data were analyzed using logistic regression to identify risk factors for the occurrence of EPM. RESULTS: Owners reported that 95% of EPM cases included in this study were diagnosed by veterinarians. Variables associated with EPM occurrence on premises included opossum regional ecology, reported exposure to small wildlife, climate, terrain, housing, choice of bedding material, method of storing feeds, equine stocking density, and primary use of horses. Among individual horses, age was most strongly associated with disease risk. Associations also were identified with sex, breed, primary use, and participation in competitions. CONCLUSIONS AND CLINICAL IMPORTANCE: Because the risk of EPM occurrence on operations is closely tied to factors that impact exposure to opossums, their feces, and their environment, controlling these exposures may be important in preventing the occurrence of EPM.     

Analysis of risk factors for the development of equine protozoal myeloencephalitis in horses

OBJECTIVE: To investigate risk factors for development of equine protozoal myeloencephalitis (EPM) in horses. DESIGN: Case-control study. ANIMALS: 251 horses admitted to The Ohio State University Veterinary Teaching Hospital from 1992 to 1995. PROCEDURE: On the basis of clinical signs of neurologic disease and detection of antibody to Sarcocystis neurona or S neurona DNA in cerebrospinal fluid, a diagnosis of EPM was made for 251 horses. Two contemporaneous series of control horses were selected from horses admitted to the hospital. One control series (n = 225) consisted of horses with diseases of the neurologic system other than EPM (neurologic control horses), and the other consisted of 251 horses admitted for reasons other than nervous system diseases (nonneurologic control horses). Data were obtained from hospital records and telephone conversations. Risk factors associated with disease status were analyzed, using multivariable logistic regression. RESULTS: Horses ranged from 1 day to 30 years old (mean +/- SD, 5.7 +/- 5.2 years). Risk factors associated with an increased risk of developing EPM included age, season of admission, prior diagnosis of EPM on the premises, opossums on premises, health events prior to admission, and racing or showing as a primary use. Factors associated with a reduced risk of developing EPM included protection of feed from wildlife and proximity of a creek or river to the premises where the horse resided. CONCLUSIONS AND CLINICAL RELEVANCE: Development of EPM was associated with a number of management-related factors that can be altered to decrease the risk for the disease.     

A multicenter case-control study of risk factors for equine protozoal myeloencephalitis

OBJECTIVE: To identify risk factors for equine protozoal myeloencephalitis (EPM) among horses examined at 11 equine referral hospitals. DESIGN: Case-control study. ANIMALS: 183 horses with EPM, 297 horses with neurologic disease other than EPM (neurologic controls), and 168 horses with non-neurologic diseases (non-neurologic controls) examined at 11 equine referral hospitals in the United States. PROCEDURES: A study data form was completed for all horses. Data were compared between the case group and each of the control groups by means of bivariate and multivariate polytomous logistic regression. RESULTS: Relative to neurologic control horses, case horses were more likely to be > or = 2 years old and to have a history of cats residing on the premises. Relative to non-neurologic control horses, case horses were more likely to be used for racing or Western performance. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that cats may play a role in the natural epidemiology of EPM, that the disease is less common among horses < 2 years of age relative to other neurologic diseases, and that horses used for particular types of competition may have an increased risk of developing EPM.     

Effect of intermittent oral administration of ponazuril on experimental Sarcocystis neurona infection of horses

OBJECTIVE: To evaluate the effect of intermittent oral administration of ponazuril on immunoconversion against Sarcocystis neurona in horses inoculated intragastrically with S neurona sporocysts. ANIMALS: 20 healthy horses that were seronegative for S neurona-specific IgG. PROCEDURES: 5 control horses were neither inoculated with sporocysts nor treated. Other horses (5 horses/group) each received 612,500 S neurona sporocysts via nasogastric tube (day 0) and were not treated or were administered ponazuril (20 mg/kg, PO) every 7 days (beginning on day 5) or every 14 days (beginning on day 12) for 12 weeks. Blood and CSF samples were collected on day - 1 and then every 14 days after challenge for western blot assessment of immunoconversion. Clinical signs of equine protozoal myeloencephalitis (EPM) were monitored, and tissues were examined histologically after euthanasia. Results: Sera from all challenged horses yielded positive western blot results within 56 days. Immunoconversion in CSF was detected in only 2 of 5 horses that were treated weekly; all other challenged horses immunoconverted within 84 days. Weekly administration of ponazuril significantly reduced the antibody response against the S neurona 17-kd antigen in CSF. Neurologic signs consistent with EPM did not develop in any group; likewise, histologic examination of CNS tissue did not reveal protozoa or consistent degenerative or inflammatory changes. CONCLUSIONS AND CLINICAL RELEVANCE: Administration of ponazuril every 7 days, but not every 14 days, significantly decreased intrathecal anti-S neurona antibody responses in horses inoculated with S neurona sporocysts. Protocols involving intermittent administration of ponazuril may have application in prevention of EPM.     

An Intensive Approach in the Treatment of Clinical Equine Protozoal Myeloencephalitis

Equine protozoal myeloencephalitis (EPM) is a serious parasitic disease of horses producing neurologic clinical signs. Sarcocystis neurona is an incriminated pathogen. If approximately 50% of US horses are seropositive but only 0.5 to 1% become clinically affected, there is a suspected immunologic influence whether a horse is S. neurona-exposed or has clinical EPM syndrome. This report presents a treatment of 28 performance horses that were serum immunoblot positive for exposure to S. neurona. This patient population was in full athletic competition, travel, or training with associated stress. We attempted to (1) improve the immunologic status of the horse, (2) protect it against inflammatory reactions, and (3) provide medication to kill the protozoa. The cell-mediated immunity was stimulated by transfer factor in the feed for 37 days. The inflammatory reactions of treatment crises from antiprotozoal activity were prevented by MicroLactin (a neutrophil-activation inhibitor) in feed for 28 days concurrently. The antiprotozoal drug ponazuril was given concurrently for 28 days. Gait abnormalities, stumbling, and behavior change were the most frequent and combined clinical signs before treatment. There were 82% (23/28) treatable horses that were back at work, including five horses that were in physical rehabilitation under saddle. Five severely affected horses were not helped by therapy.     

Sensitivity and specificity of western blot testing of cerebrospinal fluid and serum for diagnosis of equine protozoal myeloencephalitis in horses with and without neurologic abnormalities

OBJECTIVE: To determine sensitivity and specificity of western blot testing (WBT) of CSF and serum for diagnosis of equine protozoal myeloencephalitis (EPM) in horses with and without neurologic abnormalities. DESIGN: Prospective investigation. ANIMALS: 65 horses with and 169 horses without neurologic abnormalities. PROCEDURE: CSF and serum from horses submitted for necropsy were tested for Sarcocystis neurona-specific antibody with a WBT. Results of postmortem examination were used as the gold standard against which results of the WBT were compared. RESULTS: Sensitivity of WBT of CSF was 87% for horses with and 88% for horses without neurologic abnormalities. Specificity of WBT of CSF was 44% for horses with and 60% for horses without neurologic abnormalities. Regardless of whether horses did or did not have neurologic abnormalities, sensitivity and specificity of WBT of serum were not significantly different from values for WBT of CSF. Ninety-four horses without EPM had histologic evidence of slight CNS inflammation. CONCLUSIONS AND CLINICAL RELEVANCE: The low specificity of WBT of CSF indicated that it is inappropriate to diagnose EPM on the basis of a positive test result alone because of the possibility of false-positive test results. The high sensitivity, however, means that a negative result is useful in ruling out EPM. There was no advantage in testing CSF versus serum in horses without neurologic abnormalities. Slight CNS inflammation was common in horses with and without S neurona-specific antibodies in the CSF and should not be considered an indication of CNS infection with S neurona.     

Equine protozoal myeloencephalitis.

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.     

Immune response to Sarcocystis neurona infection in naturally infected horses with equine protozoal myeloencephalitis

Equine protozoal myeloencephalitis (EPM) is one of the most common neurologic diseases of horses in the United States. The primary etiologic agent is Sarcocystis neurona. Currently, there is limited knowledge regarding the protective or pathophysiologic immune response to S. neurona infection or the subsequent development of EPM. The objectives of this study were to determine whether S. neurona infected horses with clinical signs of EPM had altered or suppressed immune responses compared to neurologically normal horses and if blood sample storage would influence these findings. Twenty clinically normal horses and 22 horses with EPM, diagnosed by the presence of S. neurona specific antibodies in the serum and/or cerebrospinal (CSF) and clinical signs, were evaluated for differences in the immune cell subsets and function. Our results demonstrated that naturally infected horses had significantly (P<0.05) higher percentages of CD4 T-lymphocytes and neutrophils (PMN) in separated peripheral blood leukocytes than clinically normal horses. Leukocytes from naturally infected EPM horses had significantly lower proliferation responses, as measured by thymidine incorporation, to a non-antigen specific mitogen than did clinically normal horses (P<0.05). Currently, studies are in progress to determine the role of CD4 T cells in disease and protection against S. neurona in horses, as well as to determine the mechanism associated with suppressed in vitro proliferation responses. Finally, overnight storage of blood samples appears to alter T lymphocyte phenotypes and viability among leukocytes.     

Evidence that antibodies against recombinant SnSAG1 of Sarcocystis neurona merozoites are involved in infection and immunity in equine protozoal myeloencephalitis

Sarcocystis neurona is the principal etiologic agent of equine protozoal myeloencephalitis (EPM). An immunodominant protein of S. neurona, SnSAG-1, is expressed by the majority of S. neurona merozoites isolated from spinal tissues of horses diagnosed with EPM and may be a candidate for diagnostic tests and prophylaxis for EPM. Five horses were vaccinated with adjuvanted recombinant SnSAG1 (rSnSAG1) and 5 control (sham vaccinated) horses were vaccinated with adjuvant only. Serum was evaluated pre- and post-vaccination, prior to challenge, for antibodies against rSnSAG1 and inhibitory effects on the infectivity of S. neurona by an in vitro serum neutralization assay. The effect of vaccination with rSnSAG1 on in vivo infection by S. neurona was evaluated by challenging all the horses with S. neurona merozoites. Blinded daily examinations and 4 blinded neurological examinations were used to evaluate the presence of clinical signs of EPM. The 5 vaccinated horses developed serum and cerebrospinal fluid (CSF) titers of SnSAG1, detected by enzyme-linked immunosorbent assay (ELISA), post-vaccination. Post-vaccination serum from vaccinated horses was found to have an inhibitory effect on merozoites, demonstrated by in vitro bioassay. Following the challenge, the 5 control horses displayed clinical signs of EPM, including ataxia. While 4 of the 5 vaccinated horses did not become ataxic. One rSnSAG-1 vaccinated horse showed paresis in 1 limb with muscle atrophy. All horses showed mild, transient, cranial nerve deficits; however, disease did not progress to ataxia in rSnSAG-1 vaccinated horses. The study showed that vaccination with rSnSAG-1 produced antibodies in horses that neutralized merozoites when tested by in vitro culture and significantly reduced clinical signs demonstrated by in vivo challenge.     

Equine Protozoal Myeloencephalitis

Gathering information about Equine Protozoal Myeloencephalitis (EPM) was identified by the equine industry as one of the highest priorities for the NAHMS Equine '98 study. Overall, 59.8 percent of owners/operators interviewed had never heard of EPM, and only 9.5 percent considered themselves knowledgeable about this disease. EPM was reported to have occurred on 1.0 percent of operations in the year prior to the study and on 3.3 percent of operations at any point in the operation's history. The incidence of EPM was estimated in the year prior to the study to be 14 new cases per 10,000 horses per year. The majority of operations where EPM was reported had only identified a single case at any time during their history. While this study was based on owner/operator reports of disease, 95.0 percent of cases recognized during the year prior to this study were diagnosed by a veterinarian. Onset of disease was reported most commonly to occur during the summer or fall. The most common signs reported in cases occurring during the previous year were ataxia, limb weakness, lameness, and muscle atrophy. The most common methods used to diagnose EPM in these horses were recognition of clinical signs, serology, and CSF analysis. Among the last cases recognized on operations for which duration of illness was at least 3 months, 39.7 percent were reported to recover completely, 37.4 percent improved but did not completely recover, 14.4 percent were sold or given away because they had EPM, and 7.1 percent died or were euthanatized because of EPM. For those EPM cases that completely recovered, relapsed following improvement and showed no improvement after at least 3 months' duration, the average number of days of lost use was 244 days. For those EPM cases that died because of EPM, an estimated 9.2 years of use were lost. Excluding cases that were less than 3 months in duration, the geometric mean cost to operations for diagnostic testing, veterinary care, and medications provided for the last diagnosed case of EPM was $790. EPM was reported to occur rarely in this study population, despite the use of owner reports to measure disease occurrence. Veterinarians were almost always employed in the diagnosis of this disease for cases occurring in the previous year. Despite its rare occurrence, this disease is a very serious health problem in affected horses and only about 40 percent of affected horses were reported to have recovered completely. Equine protozoal myeloencephalitis (EPM) is a serious and often fatal neurologic disease of equids.^1-6 Ammals affected by EPM can demonstrate a variety of clinical abnormalities, and signs can vary tremendously in severity. Classically, horses with EPM develop a variety of asymmetric neurologic deficits including gait abnormalities, ataxia, weakness, and focal muscle wasting.^4-6 However, symmetric neurologic abnormalities are also seen frequently. The disease may be focal or multifocal in nature and may be manifested less frequently as a head tilt, facial paralysis, seizures, or even apparent behavioral changes.^4-6 Horses of all ages can be affected, but horses are usually at least 6 months old when first diagnosed with EPM.     

Caecal disease in equids

Objective To review the breed, age, gender, clinical and laboratory findings, treatment and outcome of horses with caecal disease presented to a referral centre. Design Retrospective study of 96 cases. Procedure The breed, age, and gender of the study population were compared with the corresponding hospital population for the same period. The means (± SD) for clinical and laboratory findings were recorded for each caecal disorder. Treatment was categorised as medical or surgical, and outcome was recorded. Results Caecal diseases included impaction (40% of total cases), rupture associated with concurrent unrelated disease (13%), rupture with parturition (9%), rupture with no associated disease (5%), infarction (11%), torsion (9%), abscess or adhesion (7%), tumour (3%), and miscellaneous conditions (3%). The breed or gender of affected horses did not differ from the hospital population, although horses > 15 years were more frequently represented (P < 0.05). This age group was specifically more predisposed to caecal impaction (P < 0.05), as were Arabian, Morgan, and Appaloosa breeds (P < 0.05). In horses with caecal impaction transrectal examination was the most useful diagnostic procedure; 90% of affected horses treated medically were discharged while horses treated by typhlotomy alone, or typhlotomy and blind end ileocolostomy, had survival rates to discharge of 71% and 86%, respectively. Horses with caecal rupture associated with concurrent un-related disease showed no signs of impending rupture; all were receiving phenylbutazone, all were euthanased, and 50% had caecal ulceration at necropsy. Of horses with caecal rupture with parturition 56% had prior dystocia; in two-thirds the site of rupture was the ileocaecal junction and all were euthanased. Horses with caecal rupture with no associated disease died or were euthanased; rupture was idiopathic. Horses with caecal infarction usually had signs of abdominal pain and abdominal fluid changes consistent with peritonitis; transrectal examination was nonspecific, and typhlectomy was successful in seven of eight horses. Horses with caecal torsion had signs of severe, acute abdominal pain and typhlectomy was successful in three of five horses. Diagnosis of caecal adhesion or abscess was assisted by transrectal palpation in two of seven horses and surgical treatment was successful in two of five horses. A caecal tumour was diagnosed in three horses aged 20 years or older that presented with chronic weight loss. Other caecal diseases were uncommon. Conclusion Caecal disease is uncommon in equids but some specific features of the history and physical findings can alert the veterinarian to the possibility of caecal involvement in horses with gastrointestinal dysfunction. Medical or surgical therapy can be effective in horses where caecal rupture has not occurred.     

Diagnosis of Equine Protozoal Myeloencephalitis Using Indirect Fluorescent Antibody Testing and Enzyme-Linked Immunosorbent Assay Titer Ratios for Sarcocystis neurona and Neospora hughesi

The aim of this study was to compare two serologic tests used to support a diagnosis of equine protozoal myeloencephalitis (EPM). Serum and cerebrospinal fluid (CSF) samples were analyzed for antibodies to Sarcocystis neurona and Neospora hughesi by indirect fluorescent antibody testing (IFAT) and surface antigens of S. neurona and N. hughesi by enzyme-linked immunosorbent assay (ELISA). The samples originated from neurologic horses with confirmed and suspected EPM (nine S. neurona, three N. hughesi), from neurologic horses with confirmed neurologic diseases other than EPM (16 horses) and from healthy horses (10). The IFAT on CSF and ELISA titer ratios showed equal sensitivity in diagnosing EPM caused by S. neurona. The ELISA titer ratios showed slightly greater specificity in diagnosing EPM than the IFAT on CSF. Overall agreement between the IFAT on CSF and ELISA titer ratio was 90.9%. The IFAT on CSF and ELISA serum/CSF ratio are indicated to help support a laboratory diagnosis of EPM.     

Development and evaluation of a Sarcocystis neurona-specific IgM capture enzyme-linked immunosorbent assay

Equine protozoal myeloencephalitis (EPM) is a serious neurologic disease of horses caused primarily by the protozoal parasite Sarcocystis neurona. Currently available antemortem diagnostic testing has low specificity. The hypothesis of this study was that serum and cerebrospinal fluid (CSF) of horses experimentally challenged with S neurona would have an increased S neurona-specific IgM (Sn-IgM) concentration after infection, as determined by an IgM capture enzyme linked immunoassay (ELISA). The ELISA was based on the S neurona low molecular weight protein SNUCD-1 antigen and the monoclonal antibody 2G5 labeled with horseradish peroxidase. The test was evaluated using serum and CSF from 12 horses experimentally infected with 1.5 million S neurona sporocysts and 16 horses experimentally infected with varying doses (100 to 100,000) of S neurona sporocysts, for which results of histopathologic examination of the central nervous system were available. For horses challenged with 1.5 million sporocysts, there was a significant increase in serum Sn-IgM concentrations compared with values before infection at weeks 2-6 after inoculation (P < .0001). For horses inoculated with lower doses of S neurona, there were significant increases in serum Sn-IgM concentration at various points in time after inoculation, depending on the challenge dose (P < .01). In addition, there was a significant increase between the CSF Sn-IgM concentrations before and after inoculation (P < .0001). These results support further evaluation of the assay as a diagnostic test during the acute phase of EPM.     

Indirect fluorescent antibody testing of cerebrospinal fluid for diagnosis of equine protozoal myeloencephalitis

OBJECTIVE: To assess the use of CSF testing with an indirect fluorescent antibody test (IFAT) for diagnosis of equine protozoal myeloencephalitis (EPM) caused by Sarcocystis neurona. SAMPLE POPULATION: Test results of 428 serum and 355 CSF samples from 182 naturally exposed, experimentally infected, or vaccinated horses. PROCEDURE: EPM was diagnosed on the basis of histologic examination of the CNS. Probability distributions were fitted to serum IFAT results in the EPM+ and EPM-horses, and correlation between serum and CSF results was modeled. Pairs of serum-CSF titers were generated by simulation, and titer-specific likelihood ratios and post-test probabilities of EPM at various pretest probability values were estimated. Post-test probabilities were compared for use of a serum-CSF test combination, a serum test only, and a CSF test only. RESULTS: Post-test probabilities of EPM increased as IFAT serum and CSF titers increased. Post-test probability differences for use of a serum-CSF combination and a serum test only were < or = 19% in 95% of simulations. The largest increases occurred when serum titers were from 40 to 160 and pre-test probabilities were from 5% to 60%. In all simulations, the difference between pre- and post-test probabilities was greater for a CSF test only, compared with a serum test only. CONCLUSIONS AND CLINICAL RELEVANCE: CSF testing after a serum test has limited usefulness in the diagnosis of EPM. A CSF test alone might be used when CSF is required for other procedures. Ruling out other causes of neurologic disease reduces the necessity of additional EPM testing.     

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 normal horses. Intra-assay variability was 4.7%, and interassay variability was 10.7%. The slope of the curve of the unknown samples of various volumes demonstrated parallelism with a curve developed using equal volumes of assay kit standard. Assay of normal and EPM-affected horses found that TGF-beta2 was present in both the serum and CSF of all animals. However, the concentration of TGF-beta2 in the CSF was less (P = 0.03) in EPM-affected horses (144 pg/ml) than in normal horses (256 pg/ml). In addition, the effect of CSF from normal and EPM-affected horses on the production of interferon-gamma (IFN-gamma) by PHA-P stimulated PBMCs from normal horses was investigated using a bioassay. It was found that CSF from normal and EPM-affected horses enhanced IFN-gamma activity from PHA-P stimulated peripheral blood mononuclear cells (P < or = 0.05); however, the response to CSF from EPM-affected horses was no different than the response to CSF from normal horses. Treatment of cells with anti-TGF-beta2 monoclonal antibodies slightly increased the response when co-incubated with CSF from normal horses, and slightly decreased it when co-incubated with CSF from EPM-affected horses. These differences, however, did not achieve statistical significance (P > 0.05). Results of this study indicated that production of TGF-beta2 is altered in horses with EPM, and that CSF appears to contain substances which alter the inflammatory reaction to plant lectins. These findings confirm the immunomodulatory properties of CSF and suggest new techniques for future research regarding the pathophysiology of EPM.     

Acute small intestinal obstruction associated with Parascaris equorum infection in young horses: 25 cases (1985–2004)

AIMS: To retrospectively evaluate the medical and surgical records of horses with acute small intestinal obstructions associated with Parascaris equorum infection; to describe the gastrointestinal lesions; and to determine the outcome of cases with such lesions.

METHODS: Records of 25 horses with acute small intestinal obstruction associated with P. equorum between 1985 and 2004 were reviewed to determine signalment, history, physical examination, surgical or post-mortem findings, and outcome.

RESULTS: All horses except one were less than 12 months old. Standardbreds were over-represented in the population studied. Sixteen horses (72%) had been administered anthelmintics, including pyrantel (n=8), ivermectin (n=7), and trichlorphon (n=1), within 24 h prior to the onset of colic. Of the 25 cases reviewed, 16 had simple obstructive ascarid impactions (SOAIs), and nine had complicated obstructive ascarid impaction (COAI) including volvulus (n=6) or intussusception (n=3), both concurrent with ascarid impaction of the small intestine. Short-term survival (discharge from hospital) occurred in 79% of horses treated for SOAI, and was 64% for all horses. Long-term survival (>1 year) occurred in 33% of horses with SOAI, and the overall long-term survival was 27% for all horses. Formation of adhesions was the most frequent finding associated with death for horses that did not survive long-term.

CONCLUSIONS AND CLINICAL RELEVANCE: The incidence of anthelmintic treatment within 24 h of the onset of colic in this study population (72%) was higher than that previously reported. Resistance of P. equorum to ivermectin recently reported in Ontario may be associated with increased ascarid burdens, predisposing horses to ascarid impaction. The long-term survival of these horses was better than that reported previously.     

Equine Protozoal Myeloencephalitis: An Updated Consensus Statement with a Focus on Parasite Biology,Diagnosis, Treatment,and Prevention

Equine protozoal myeloencephalitis (EPM) remains an important neurologic disease of horses. There are no pathognomonic clinical signs for the disease. Affected horses can have focal or multifocal central nervous system (CNS) disease. EPM can be difficult to diagnose antemortem. It is caused by either of 2 parasites, Sarcocystis neurona and Neospora hughesi, with much less known about N. hughesi. Although risk factors such as transport stress and breed and age correlations have been identified, biologic factors such as genetic predispositions of individual animals, and parasite‐specific factors such as strain differences in virulence, remain largely undetermined. This consensus statement update presents current published knowledge of the parasite biology, host immune response, disease pathogenesis, epidemiology, and risk factors. Importantly, the statement provides recommendations for EPM diagnosis, treatment, and prevention.     

Periorbital skull fractures in five horses

Periorbital skull fractures were diagnosed in 5 horses, and were associated with ophthalmic complications including corneal ulceration, uveitis, and entrapment of the eye by retrobulbar bone fragments. Physical examination was of greater diagnostic use than radiography. Surgical repair was performed on all horses and was associated with a more favorable postoperative appearance in horses treated acutely; however, the cosmetic results were considered acceptable in all horses. Major postoperative complications were not observed.