Factors associated with keratopathy in captive pinnipeds.

OBJECTIVE To identify factors associated with keratopathy in captive pinnipeds and to provide guidance for preventive measures. ANIMALS 319 captive pinnipeds (229 otariids [sea lions and fur seals], 74 phocids [true seals], and 16 odobenids [walrus]) from 25 facilities. PROCEDURES Descriptive data collected from questionnaires completed by facilities and from medical records and physical examinations of pinnipeds were compiled and evaluated. Variables were assessed with χ2 tests of homogeneity to determine potential association with keratopathy, and variables with values of P ≤ 0.25 were inserted into the multivariable logistic regression model. RESULTS Results indicated that variables associated with significantly increased odds of keratopathy in captive pinnipeds included lighter or reflective pool color (OR, 2.11; 95% confidence interval [CI], 1.20 to 3.97), pool water salinity < 29 g/L (OR, 3.48; 95% CI, 1.89 to 6.56), and history of eye disease (OR, 3.30; 95% CI, 1.85 to 5.98), trauma (OR, 3.80; 95% CI, 1.72 to 8.89), and having been tested for leptospirosis (OR, 3.83; 95% CI, 1.54 to 10.26). However, odds of keratopathy decreased with UV index ≤ 6 (OR, 0.39; 95% CI, 0.2 to 0.72) and age < 20 years (OR, 0.32; 95% CI, 0.15 to 0.66). CONCLUSIONS AND CLINICAL RELEVANCE Findings indicated that odds of keratopathy in pinnipeds could be reduced by maintenance of pool water salinity ≥ 29 g/L and reduction of UV radiation exposure (eg, with adequate shade structures and use of darker, natural colors). Because UV radiation exposure is cumulative, even small attempts to reduce lifetime exposure to it could help control keratopathy in pinnipeds.

Risk of environmental exposure to small coccidia from wild canid feces in rural Ohio.

OBJECTIVE To determine the extent of environmental exposure to heteroxenous coccidia from wild canid feces in southeastern Ohio. SAMPLE 285 presumed wild canid fecal samples collected across an ecological system in southeastern Ohio. PROCEDURES Morphological classification and molecular analysis were used to determine the canid genus for collected fecal samples. Microscopic and molecular analysis were used to detect coccidian oocysts and DNA. Several variables were analyzed for associations with coccidian DNA detection or prevalence. RESULTS Coccidian DNA was detected in 51 of 285 (17.9%) fecal samples. Of those positive samples, 1% (95% confidence interval, 0.4% to 3%) had positive results for Hammondia heydorni and none had positive results for Neospora caninum, for an estimated environmental N caninum prevalence of 0% (95% confidence interval, 0% to 7%)/1-km2 hexagonal area evaluated. Morphological classification revealed that 78.9% (225/285) of fecal samples were from coyotes and 17.2% (49/285) were from foxes. No difference in proportions of coccidian DNA-positive fecal samples was identified among canid species. Environmental temperature and fecal freshness were associated with coccidian DNA detection. Land use type, relative canid density, and cattle density were not associated with the prevalence of coccidian DNA-positive samples. CONCLUSIONS AND CLINICAL RELEVANCE The low prevalence of coccidia shed in wild canid feces in this study, including the estimated 0% environmental prevalence of N caninum, suggested that the role of the oocyst environmental phase in coccidia transmission to ruminants is likely minor in rural southeastern Ohio.

Testing the Sarcocystis neurona vaccine using an equine protozoal myeloencephalitis challenge model.

Equine protozoal myeloencephalitis (EPM) is an important equine neurologic disorder, and treatments for the disease are often unrewarding. Prevention of the disease is the most important aspect for EPM, and a killed vaccine was previously developed for just that purpose. Evaluation of the vaccine had been hampered by lack of post vaccination challenge. The purpose of this study was to determine if the vaccine could prevent development of clinical signs after challenge with Sarcocystis neurona sporocysts in an equine challenge model. Seventy horses that were negative for antibodies to S. neurona and were neurologically normal were randomly assigned to vaccine or placebo groups and divided into short-term duration of immunity (study #1) and long-term duration of immunity (study #2) studies. S. neurona sporocysts used for the challenge were generated in the opossum/raccoon cycle isolate SN 37-R. Study #1 horses received an initial vaccination and a booster, and were challenged 34days post second vaccination. Study #2 horses received a vaccination and two boosters and were challenged 139days post third vaccination. All horses in study #1 developed neurologic signs (n=30) and there was no difference between the vaccinates and controls (P=0.7683). All but four horses in study #2 developed detectable neurologic deficits. The neurologic signs, although not statistically significant, were worse in the vaccinated horses (P=0.1559). In these two studies, vaccination with the S. neurona vaccine failed to prevent development of clinical neurologic deficits.

Small sarcocysts can be a feature of experimental infections with Sarcocystis neurona merozoites.

Several reports indicate the presence of small tissue cysts associated with Sarcocystis neurona infections. Several failed attempts to develop tissue cysts in potential intermediate host using in vitro derived parasites originally isolated from horses with equine protozoal myeloencephalitis suggest that the experimental methods to achieve bradyzoites with those isolates was not possible. Those prior studies reported the lack of detectable sarcocysts based on histology and in vivo feeding trials. A recent report of successful production and detection of small sarcocysts triggered us to review archived tissues from earlier experimental infection studies. The retrospective review sought to determine if small sized sarcocysts were not detected due to their relatively smaller size and infrequency as compared to larger sized sarcocysts produced with other isolates in these experimental inoculation trials. Tissues from two prior in vivo inoculation studies, involving in vitro-produced parasites inoculated into laboratory-reared cats and raccoons, were re-examined by immunohistochemistry staining to more easily detect the tissue cysts. In the experimental cat study no small tissue cysts were seen, consistent with the original publication results. However, in the experimental raccoon study, one raccoon inoculated with an EPM-derived isolate, SN-UCD1, had small sarcocysts not reported in the original publication. This retrospective study suggests that much closer scrutiny of tissues, including the use of immunohistochemistry on tissue sections is required to detect the smaller S. neurona sarcocysts associated with the experimental inoculations of the isolates originally derived from horses with EPM.

Sarcocystis neurona manipulation using culture-derived merozoites for bradyzoite and sporocyst production.

Equine protozoal myeloencephalitis (EPM) remains a significant central nervous system disease of horses in the American continents. Sarcocystis neurona is considered the primary causative agent and its intermediate life stages are carried by a wide host-range including raccoons (Procyon lotor) in North America. S. neurona sarcocysts mature in raccoon skeletal muscle and can produce central nervous system disease in raccoons, mirroring the clinical presentation in horses. The study aimed to develop laboratory tools whereby the life cycle and various life stages of S. neurona could be better studied and manipulated using in vitro and in vivo systems and compare the biology of two independent isolates. This study utilized culture-derived parasites from S. neurona strains derived from a raccoon or from a horse to initiate raccoon infections. Raccoon tissues, including fresh and cryopreserved tissues, were used to establish opossum (Didelphis virginiana) infections, which then shed sporocyts with retained biological activity to cause encephalitis in mice. These results demonstrate that sarcocysts can be generated using in vitro-derived S. neurona merozoites, including an isolate originally derived from a naturally infected horse with clinical EPM. This study indicates the life cycle can be significantly manipulated in the laboratory without affecting subsequent stage development, allowing further purification of strains and artificial maintenance of the life cycle.

Reported rabies pre-exposure immunization of students at US Colleges of Veterinary Medicine.

In 2008, the US experienced a disruption in human rabies vaccine supplies, leading public health authorities to prioritize vaccine release for post-exposure prophylaxis (PEP) and limit vaccine supplies for pre-exposure prophylaxis (PreEP) in high-risk groups. In 2008, the Association of American Veterinary Medical Colleges (AAVMC) surveyed its member institutions on rabies vaccination policies and practices. Senior administrators at Colleges of Veterinary Medicine (CVMs) and departments of veterinary science and comparative medicine were asked to identify the person most knowledgeable about their institution's student rabies vaccination program. Respondents were asked to describe their policies and procedures for administering PreEP to veterinary medical students and staff and to estimate the annual demand for student and staff PreEP vaccine. Twenty-one CVMs responded. Twenty (95%) reported requiring PreEP of veterinary medical students and 16 (80%) of those 20 required vaccination upon matriculation. An estimated 7,309 doses of vaccine were required for PreEP of an estimated 2,436 first-year US veterinary medical students. Seventy-two percent of respondents administered PreEP in August, September, and October, coinciding with the highest public demand for PEP. CVMs should consider altering the timing of rabies vaccine administration to veterinary medical students and staff to other months, thereby helping to ensure that PEP rabies vaccine will be available to people with validated rabies exposures and to ensure that supplies will be available for PreEP of students and staff. AAVMC may wish to identify and support a point of coordination to facilitate the purchase and distribution of human rabies vaccine among its US member CVMs.

In vivo effects of adjunctive tetracycline treatment on refractory corneal ulcers in dogs.

OBJECTIVE: To evaluate effect of adjunctive treatment with tetracycline analogues on time to complete corneal reepithelialization in dogs with nonhealing (ie, refractory) corneal ulcers. DESIGN: Randomized controlled clinical trial. ANIMALS: 89 dogs with refractory corneal ulcers. PROCEDURES: Corneal ulcers were treated via debridement and grid keratotomy. Dogs were assigned to receive 1 of 3 treatment regimens for up to 6 weeks: doxycycline (5 mg/kg [2.27 mg/lb], PO, q 12 h) with topically applied ophthalmic ointment containing neomycin, polymyxin B, and bacitracin (ie, triple antibiotic ointment; q 8 h); cephalexin (22 mg/kg [10 mg/lb], PO, q 12 h) with topically applied oxytetracycline ophthalmic ointment (q 8 h); or a control treatment of cephalexin (22 mg/kg, PO, q 12 h) with topically applied triple antibiotic ointment (q 8 h). Healing was monitored via measurements of the wound with calipers and evaluation of photographs obtained every 2 weeks. Treatment effectiveness was evaluated by wound healing and decreased signs of pain. RESULTS: The Boxer breed was overrepresented in all groups. At the 2-week time point, wound healing was significantly more common in small-breed dogs, compared with large-breed dogs. Dogs treated with oxytetracycline ophthalmic ointment had a significantly shorter healing time than did dogs receiving the control treatment. Corneal ulcers in dogs that received doxycycline PO healed more rapidly than did ulcers in dogs in the control treatment group; however, this difference was not significant. CONCLUSIONS AND CLINICAL RELEVANCE: Topical tetracycline ophthalmic ointment was a safe, inexpensive, and effective adjunctive treatment for refractory corneal ulcers in dogs.

Risk factors associated with cataracts and lens luxations in captive pinnipeds in the United States and the Bahamas.

OBJECTIVE: To determine risk factors for lens luxation and cataracts in captive pinnipeds in the United States and the Bahamas. DESIGN: Cross-sectional study. ANIMALS: 111 pinnipeds (99 California sea lions [Zalophus californianus], 10 harbor seals [Phoca vitulina], and 2 walruses [Odobenus rosmarus]) from 9 facilities. PROCEDURES: Eyes of each pinniped were examined by a veterinary ophthalmologist for the presence of cataracts or lens luxations and photographed. Information detailing husbandry practices, history, and facilities was collected with a questionnaire, and descriptive statistical analyses were performed for continuous and categorical variables. Odds ratios and associated 95% confidence intervals were estimated from the final model. RESULTS: Risk factors for lens luxation, cataracts, or both included age >or= 15 years, history of fighting, history of ocular disease, and insufficient access to shade. CONCLUSIONS AND CLINICAL RELEVANCE: Diseases of the lens commonly affect captive pinnipeds. Access to UV-protective shade, early identification and medical management of ocular diseases, and prevention of fighting can limit the frequency or severity of lens-related disease in this population. An extended life span may result from captivity, but this also allows development of pathological changes associated with aging, including cataracts.

The need for veterinarians in biomedical research.

The number of veterinarians in the United States is inadequate to meet societal needs in biomedical research and public health. Areas of greatest need include translational medical research, veterinary pathology, laboratory-animal medicine, emerging infectious diseases, public health, academic medicine, and production-animal medicine. Veterinarians have unique skill sets that enable them to serve as leaders or members of interdisciplinary research teams involved in basic science and biomedical research with applications to animal or human health. There are too few graduate veterinarians to serve broad national needs in private practice; academia; local, state, and federal government agencies; and private industry. There are no easy solutions to the problem of increasing the number of veterinarians in biomedical research. Progress will require creativity, modification of priorities, broad-based communication, support from faculty and professional organizations, effective mentoring, education in research and alternative careers as part of the veterinary professional curriculum, and recognition of the value of research experience among professional schools' admissions committees. New resources should be identified to improve communication and education, professional and graduate student programs in biomedical research, and support to junior faculty. These actions are necessary for the profession to sustain its viability as an integral part of biomedical research.

A new approach to teaching veterinary public health at the Ohio State University.

Public-health practitioners with expertise in the area of veterinary public health are expected to understand the prevention and control of zoonotic infectious diseases in both human and animal populations. This focus on multiple species is what makes the veterinary public health (VPH) official unique. The development of a new VPH specialization within the existing Master of Public Health (MPH) degree program at the Ohio State University represents a significant new collaboration between the College of Veterinary Medicine and the College of Public Health. The main objective of the VPH specialization is to educate and train professionals to provide them with the skills, knowledge, and resources necessary to protect and improve human health using a One Medicine approach. The program targets a population of students who will likely enter the professional veterinary medicine curriculum but have one year available to enhance their preparatory training in health sciences before beginning the program. A core series of VPH courses was initiated to complement the existing MPH course requirements. The program has been successful in attracting students from the primary target population, but it has also attracted students wanting the MPH as a terminal degree and veterinarians returning to school to expand their career options.

Strains of Sarcocystis neurona exhibit differences in their surface antigens, including the absence of the major surface antigen SnSAG1.

A gene family of surface antigens is expressed by merozoites of Sarcocystis neurona, the primary cause of equine protozoal myeloencephalitis (EPM). These surface proteins, designated SnSAGs, are immunodominant and therefore excellent candidates for development of EPM diagnostics or vaccines. Prior work had identified an EPM isolate lacking the major surface antigen SnSAG1, thus suggesting there may be some diversity in the SnSAGs expressed by different S. neurona isolates. Therefore, a bioinformatic, molecular and immunological study was conducted to assess conservation of the SnSAGs. Examination of an expressed sequence tag (EST) database revealed several notable SnSAG polymorphisms. In particular, the EST information implied that the EPM strain SN4 lacked the major surface antigen SnSAG1. The absence of this surface antigen from the SN4 strain was confirmed by both Western blot and Southern blot. To evaluate SnSAG polymorphisms in the S. neurona population, 14 strains were examined by Western blots using monospecific polyclonal antibodies against the four described SnSAGs. The results of these analyses demonstrated that SnSAG2, SnSAG3, and SnSAG4 are present in all 14 S. neurona strains tested, although some variance in SnSAG4 was observed. Importantly, SnSAG1 was not detected in seven of the strains, which included isolates from four cases of EPM and a case of fatal meningoencephalitis in a sea otter. Genetic analyses by PCR using gene-specific primers confirmed the absence of the SnSAG1 locus in six of these seven strains. Collectively, the data indicated that there is heterogeneity in the surface antigen composition of different S. neurona isolates, which is an important consideration for development of serological tests and prospective vaccines for EPM. Furthermore, the diversity reported herein likely extends to other phenotypes, such as strain virulence, and may have implications for the phylogeny of the various Sarcocystis spp. that undergo sexual stages of their life cycle in opossums.

Outbreak of neurologic disease caused by equine herpesvirus-1 at a university equestrian center.

BACKGROUND: Equine herpesvirus type 1 (EHV-1) infection causes neurologic disease in horses. However, risk factors for the disease and long-term prognosis are poorly characterized. HYPOTHESIS: There are identifiable risk factors for equine herpes-1 myeloencephalopathy. ANIMALS: The entire population of 135 horses housed within the equestrian facility. METHODS: A descriptive study investigated the clinical, serologic, virologic, and management aspects of an outbreak of EHV-1 myeloencephalopathy. RESULTS: Out of 135 horses at the facility, 117 displayed signs of EHV-1 infection. Forty-six horses developed neurologic deficits characterized by symmetrical hind limb ataxia and weakness. Twelve horses that developed neurologic deficits became recumbent and did not survive. The development of severe neurologic deficits during the outbreak was associated with the presence of residual deficits at the 6-month examination. Within 1 year of the outbreak onset, all horses that survived had returned to an exercise level comparable to that experienced before the outbreak. Factors associated with the development of neurologic disease included age of > 5 years, location in the south or arena stall areas, and highest rectal temperature on day 3 or later of the febrile period. CONCLUSIONS AND CLINICAL IMPORTANCE: Being > 5 years of age, having had a rectal temperature of > 103.5 degrees F, and highest rectal temperature occurring on or after the 3rd day of the febrile period were the factors most predictive of the development of neurologic disease and death. Data obtained during this outbreak substantiate previous findings relating to clinical aspects and diagnosis of EHV-1 myeloencephalopathy. The prophylactic and therapeutic use of acyclovir during this outbreak is described.

The role of the slug transcription factor in cell migration during corneal re-epithelialization in the dog.

Epithelial cell migration during corneal wound re-epithelialization shares features with the developmental process of epithelial-mesenchymal transition (EMT) modulated by Snail family transcription factors, including Slug. Our studies demonstrated that Slug expression was enhanced at sites of epithelial cell migration at the margins of normally healing corneal wounds in dogs, but significantly decreased at the margins of non-healing canine corneal erosions. Increased Slug expression was associated with internalization of E-cadherin and beta-catenin from the cell membrane and with enhanced expression of smooth-muscle-specific alpha-actin, tropomyosin, and matrix metalloproteinases at wound margins. Enhanced Slug expression in corneal explants due to an adenoviral expression construct or to oxytetracycline treatment resulted in significantly higher rates of corneal epithelial cell migration. Oxytetracycline appeared to act by stimulating transforming growth factor-beta activity, thus increasing Slug expression and enhancing corneal epithelial migration. These findings highlight the similarities between epithelial migration during EMT and during successful corneal wound healing, support an important role for the Snail family in the process, and indicate that modulating Slug expression may be clinically useful in treating non-healing corneal wounds.

A review of some of the health issues of captive black rhinoceroses (Diceros bicornis).

In captivity, black rhinoceroses (Diceros bicornis) are beset by many disease syndromes not described in black rhinoceroses in the wild. Hemolytic anemia, hepatopathy, and ulcerative dermatopathy that lead to increased morbidity and mortality characterize these syndromes. It is uncertain whether these are separate disease syndromes with different etiologies or the same disease with different manifestations. This article offers a brief review of some of the health issues of concern for the captive black rhinoceros population and proposes some possible avenues of research for consideration.

Risk factors associated with a skewed natal sex ratio in captive black rhinoceroses (Diceros bicornis) in the United States.

The skew toward males in the sex ratio of calves is considered to be a problem for the captive population of black rhinoceroses (Diceros bicornis) in North America. This study used a retrospective case-control design to determine whether there was a predisposition toward birth of male calves over female calves and to examine risk factors associated with the occurrence of any detected skewed natal sex ratio in captive black rhinoceroses in the United States. The study population included captive female black rhinoceroses housed in the United States that had given birth to at least one calf of known sex. This study confirmed a skewing of the natal sex ratio toward male calves in the captive black rhinoceros population. The skewed ratio was found in calves born to wild-born dams, for which an increased time in captivity, irrespective of age, was associated with an increased likelihood of a male calf. Dams between 12 and 19 yr of age had a decreased likelihood of a male calf. The data also suggested a possible trend for the southern subspecies of black rhinoceros (Diceros bicornis minor) to be more likely to produce male calves than the eastern subspecies (Diceros bicornis michaeli). No associations were found with the sex of offspring in captive-born dams: however, this lack of association could be a result of low power in the study.

Posterior capsular opacification in diabetic and nondiabetic canine patients following cataract surgery.

Posterior capsular opacification (PCO) is the most common postoperative complication of contemporary cataract surgery. Limited information is available regarding PCO formation and factors that influence PCO development in the dog. Two hundred sixty-five eyes (144 from diabetic dogs and 121 from dogs with breed-related cataracts) were prospectively evaluated for PCO formation for up to 12 months postoperatively. The mean age of all dogs in the study was 7.77 years and diabetic dogs were significantly older than dogs with breed-related cataracts. There were 73 males (61 neutered, 12 intact) and 74 females (70 neutered, 4 intact) in the study. Statistical analysis was performed based on age, breed/size, gender, stage of cataract at the time of surgery, PCO score at each time point, breed-related vs. diabetic cataract, right eyes compared to left eyes, and presence/absence of uveitis. Age and gender did not significantly influence PCO formation. Small and medium-sized breeds developed significantly more PCO in comparison to the large/giant breeds at 2 weeks and 2-4 months postoperatively, but the differences were not significant at later time points. There was an overall significant increase in PCO formation in eyes with early immature cataracts when compared to other stages of cataract up to 4 months postoperatively but not at later time points. There were no statistical differences in PCO score at 6 months or at 1 year postoperatively in eyes with breed-related and diabetic cataracts. Right eyes did not differ from left eyes in PCO score. PCO score significantly increased over time in breed-related and diabetic groups and in the overall population. No difference was found in the degree of PCO formation in eyes with inflammation prior to or after surgery compared with those without inflammation. In summary, age, gender, presence of inflammation, and cause of cataract (breed-related vs. diabetes mellitus) do not influence the development of PCO in canine cataract dogs. Small and medium-sized breeds develop significant PCO earlier than larger breeds. It is important to note that all eyes from all dogs in this study developed PCO in a time dependent manner.

Short- and long-term outcome and factors predicting survival after surgical tube cystostomy for treatment of obstructive urolithiasis in small ruminants.

OBJECTIVE: To evaluate outcome of small ruminants after tube cystostomy without urethral flushing. STUDY DESIGN: Retrospective clinical study. ANIMALS: Small ruminants (n=63; 50 goats, 13 sheep). METHODS: Medical records (January 1996-October 2003) for all small ruminants undergoing tube cystostomy were analyzed. Signalment, laboratory data, intraoperative findings, urolith type, and postoperative outcome were compared. Long-term follow-up was obtained at 6 and > or= 12 months postoperatively. RESULTS: Most animals were castrated males. Pygmy goats were overrepresented. Mean time to normal urination after tube cystostomy was 11 days, and mean hospitalization was 14 days. Seventy-six percent of animals were successfully treated with tube cystostomy (90% of those discharged from hospital). Short- and long-term survival was good for those animals with follow-up data. Reobstruction occurred in <20% of animals at 6 and 12 months. Goats, castrated males, and animals with normal serum potassium, no fluid in the abdomen, or no urethral process amputation were more likely to survive. Stone type, bladder appearance, and age at castration were not associated with outcome. CONCLUSION: Surgical tube cystostomy without urethral flushing is an effective technique for resolution of obstructive urolithiasis in small ruminants. CLINICAL RELEVANCE: Goats, small ruminants with an intact urethral process, absence of abdominal fluid, and serum potassium concentration <5.2 mEq/L at admission were all associated with survival after tube cystostomy. Castrated males may also be more likely to survive. These factors should be considered in management of small ruminants with urolithiasis.

Evaluation of a balloon constant rate infusion system for treatment of septic arthritis, septic tenosynovitis, and contaminated synovial wounds: 23 cases (2002-2005).

OBJECTIVE-To determine clinical findings and outcome in horses treated by means of a balloon constant rate infusion system. DESIGN-Retrospective case series. ANIMALS-23 horses. PROCEDURES-Medical records of horses examined at The Ohio State University veterinary teaching hospital from 2002 to 2005 that had septic arthritis, septic tenosynovitis, or penetration of a synovial structure and in which treatment involved a balloon constant rate infusion system were searched. Information pertaining to signalment, history, physical examination findings, clinicopathologic data, treatment, and duration of hospitalization was recorded. RESULTS-Mean+/- SD duration of hospitalization was 11.5+/-5.26 days. No correlation between duration of clinical signs and duration of hospitalization or duration of infusion pump use was detected, but correlations between WBC count and duration of hospitalization and WBC and duration of infusion-pump use were observed. All horses survived to discharge. Follow-up information was obtained on 17 horses, 16 of which were alive at the time of follow-up. Twelve of 13 horses for which followup information was available for at least 5 months were alive 5 months or longer after discharge. Thirteen of the 16 horses alive at follow-up were reported by owners as not lame, whereas the remaining 3 were mildly lame or intermittently moderately lame or had developed angular limb deformity in the contralateral limb. CONCLUSIONS AND CLINICAL RELEVANCE-Balloon constant rate infusion systems may be used effectively in treatment of septic arthritis, septic tenosynovitis, and contaminated synovial wounds. Clinical response and long-term outcome appeared to be comparable to results obtained with other techniques.

Enzyme-linked immunosorbent assays for detection of equine antibodies specific to Sarcocystis neurona surface antigens.

Sarcocystis neurona is the primary causative agent of equine protozoal myeloencephalitis (EPM), a common neurologic disease of horses in the Americas. We have developed a set of enzyme-linked immunosorbent assays (ELISAs) based on the four major surface antigens of S. neurona (SnSAGs) to analyze the equine antibody response to S. neurona. The SnSAG ELISAs were optimized and standardized with a sample set of 36 equine sera that had been characterized by Western blotting against total S. neurona parasite antigen, the current gold standard for S. neurona serology. The recombinant SnSAG2 (rSnSAG2) ELISA showed the highest sensitivity and specificity at 95.5% and 92.9%, respectively. In contrast, only 68.2% sensitivity and 71.4% specificity were achieved with the rSnSAG1 ELISA, indicating that this antigen may not be a reliable serological marker for analyzing antibodies against S. neurona in horses. Importantly, the ELISA antigens did not show cross-reactivity with antisera to Sarcocystis fayeri or Neospora hughesi, two other equine parasites. The accuracy and reliability exhibited by the SnSAG ELISAs suggest that these assays will be valuable tools for examining the equine immune response against S. neurona infection, which may help in understanding the pathobiology of this accidental parasite-host interaction. Moreover, with modification and further investigation, the SnSAG ELISAs have potential for use as immunodiagnostic tests to aid in the identification of horses affected by EPM.