Survival of formalin intoxication in a 13-year-old Thoroughbred gelding.

BACKGROUND: Formalin intoxication via the gastrointestinal route has not been previously reported in the horse. Whereas ingestion of formalin in humans, although rare, is well documented. Majority of human cases are either accidental, suicidal or homicidal and often lead to fatality, with a reported lethal formaldehyde dose equating to 0.12 - 0.16 g/kg bwt. OBJECTIVES: To describe a single case report of the clinical management of an adult horse referred to a veterinary teaching hospital following accidental administration of 10% formalin via nasogastric tube. METHODS: A 13-year-old Thoroughbred gelding originally presented to the referring veterinarian for colic where 1.8 L of 10% formalin was accidentally administered instead of mineral oil via nasogastric intubation, a potentially lethal dose of formaldehyde (0.12 g/kg bwt). Approximately 20-hours following 10% formalin administration the horse was admitted to the referral hospital with moderate tachycardia, occasional ectopic beats, tacky and hyperaemic mucous membranes, delayed capillary refill time, reduced borborygmi, and pronounced digital pulses. Diagnostic investigations included laboratory blood analysis, urinalysis, electrocardiogram, abdominal ultrasound, palpation per rectum and gastroscopy. RESULTS: Patient assessment found evidence of toxicity to the gastrointestinal tract, hypovolaemia and risk for laminitis. Intensive care included fluid and electrolyte therapy, anti-inflammatories and analgesia, continuous digital cryotherapy, gastro-protectants and other methods of gastrointestinal support. The horse was discharged from hospital on day 14 with no long-term complications and the client-veterinarian relationship was preserved. DISCUSSION: In human cases of ingestion, gastrointestinal injury is typically accompanied by severe metabolic acidosis and multiple organ dysfunction syndrome due to toxicity of other body systems that can contribute to non-survival. Formaldehyde toxicity in the present case predominantly affected the gastrointestinal tract, most likely a direct result of the route of administration. Aside from gastrointestinal injury, primary toxicity of other body systems was not confirmed. To prevent this medical error recurring, the referring veterinary clinic revised their labelling and storage of 10% formalin. CONCLUSION: This is the first report of systemic formalin intoxication in the horse. Following a high dose of 10% formalin (0.12 g/kg bwt formaldehyde) enterally, the horse survived having received intensive supportive care based on human guidelines for ingested formalin.

Diagnosis and management of thyroid disorders and thyroid hormone supplementation in adult horses and foals.

Equine thyroid disorders pose a diagnostic challenge in clinical practice because of the effects of nonthyroidal factors on the hypothalamic-pituitary-thyroid axis, and the horse's ability to tolerate wide fluctuations in thyroid hormone concentrations and survive without a thyroid gland. While benign thyroid tumours are common in older horses, other disorders like primary hypothyroidism or hyperthyroidism in adult horses and congenital hypothyroidism in foals are rare. There is a common misunderstanding regarding hypothyroidism in adult horses, especially when associated with the clinical profile of obesity, lethargy, and poor performance observed in dogs and humans. Low blood thyroid hormone concentrations are often detected in horses as a secondary response to metabolic and disease states, including with the nonthyroidal illness syndrome; however, it is important to note that low thyroid hormone concentrations in these cases do not necessarily indicate hypothyroidism. Assessing equine thyroid function involves measuring thyroid hormone concentrations, including total and free fractions of thyroxine (T4) and triiodothyronine (T3); however, interpreting these results can be challenging due to the pulsatile secretion of thyroid hormones and the many factors that can affect their concentrations. Dynamic testing, such as the thyrotropin-releasing hormone stimulation test, can help assess the thyroid gland response to stimulation. Although true hypothyroidism is extremely rare, thyroid hormone supplementation is commonly used in equine practice to help manage obesity and poor performance. This review focuses on thyroid gland pathophysiology in adult horses and foals, interpretation of blood thyroid hormone concentrations, and evaluation of horses with thyroid disorders. It also discusses the use of T4 supplementation in equine practice.

Efficacy of treatment of equine anhidrosis with acupuncture and Chinese herbs is low but higher in treated horses compared with placebo.

OBJECTIVE: To assess the therapeutic efficacy of acupuncture in combination with Chinese herbs for treatment of horses affected with anhidrosis. ANIMALS: 44 horses affected with anhidrosis for up to 3 years' duration were enrolled. Inclusion required both compatible clinical signs and results of a quantitative intradermal terbutaline sweat test. METHODS: Study horses were randomly allocated into 2 groups. Group 1 (n = 19) was treated with daily Chinese herbs and 4 weekly acupuncture sessions. Group 2 (n = 25) was given daily hay powder as a placebo and 4 weekly sham acupuncture sessions. Horses were tested by quantitative intradermal terbutaline sweat test within 2 days after treatment completion and again 4 weeks following treatment. RESULTS: Terbutaline-induced sweat responses (mg) were not different between groups within 2 days and 4 weeks after treatment. Two days after treatment, ratios of sweat responses (compared to baseline) were higher (P < .05) in the treatment group compared to the placebo group at terbutaline concentrations of 1.0, 100, and 1,000 µg/mL. The number of horses responding to treatment was higher in the treatment group (5/19 [26%]), compared to horses in the placebo group (1/25 [4%]) for 1 of 5 terbutaline concentrations 2 days (10 µg/mL) or 4 weeks (0.1 µg/mL) after treatment. CLINICAL RELEVANCE: Ratios of sweat responses were higher in treatment horses 2 days after treatment, compared to baseline, but not 4 weeks later. The efficacy of a traditional Chinese veterinary medicine protocol for anhidrosis treatment with acupuncture and Chinese herbs was low but higher in treated horses compared with placebo.

[Opinion among veterinarians on equine Lyme disease - results of a questionnaire study]. / Tierärztliches Meinungsbild zur Equinen Lyme-Borreliose ­ Ergebnisse einer Fragebogenstudie.

AIM: Recording equine veterinarians opinion on equine Lyme disease. MATERIAL AND METHODS: A survey was conducted to get a general impression of the opinion of German equine vets on the topic of equine Lyme Borreliosis. The main focus of this questionnaire study was set on the diagnostic and therapeutic approach of the horse vets. RESULTS: Overall almost half of the veterinarians (48 %) detected only rarely or never serological antibodies against Bb , 47 %found occasionally and 5 % frequently Borrelia antibodies within their clientel.Concerning the existence of clinical LB in horses, 51 % of the veterinarians reported clinical cases, 43 % thought it might be possible but have not seen cases themselves and 6 % categorically ruled out the existence.On average, further diagnostic measures for LB diseases were initiated 15 ± 9 times per year and 1.4 ± 1.0 cases of equine LB diseases were diagnosed per year. In the majority of 68 % of the cases, the veterinarians chose serological tests as diagnostic measures, followed by a combination of serological tests and Antigen detection tests (27 %) and only 5 % of the veterinarians were using Antigen detection tests exclusively. Blood and skin biopsies were submitted most frequently for direct Antigendetection. The treatment of horses with positive laboratory results indicating Lyme disease and clinical symptoms assessed as suitable was carried out by 93 % of the veterinarians with antibiotics and 7% with homeopathy. Doxycycline (68 %) was used most frequently. The antibiotic treatment was applied over a period of 3 (31 %) to 4 (63 %) weeks.Regarding the question of a possible vaccination, 39 % of veterinarians do not offer vaccination against Lyme borreliosis, 20 % have not yet used it, but do not categorically reject it, and 41 % regularly carry out vaccinations against Lyme borreliosis. CONCLUSION AND CLINICAL RELEVANCE: The opinion on the clinical relevance of Equine Lyme Borreliosis among german equine veterinarians vary considerably. Uniform diagnostic guidelines and, possibly, recommendations for therapy would serve to counteract the existing uncertainty concerning this disease within the equine veterinary community.

Integrative Approach to Neck Pain and Dysfunction.

Equine cervical pain and dysfunction may be difficult to diagnose and effectively manage. Understanding techniques in integrative medicine often allows the practitioner to observe and palpate areas of pain and dysfunction in the horse being evaluated in ways often not taught or used in conventional medicine. There are many integrative therapies that also may be utilized to more effectively manage these horses, resulting in a more comfortable and functional horse.

Optimizing Health - Integrative Medicine & Poor Performance.

Addressing poor performance issues in horses is a common yet challenging request to veterinarians. Often, there are limited field diagnostic or therapy choices. Growing lay popularity in integrative therapies, as well as increasing clinical incorporation, is creating more awareness of their clinical applications. Many modalities are showing increasing evidence of positive outcomes with minimal harm, but additional safety and efficacy evaluation is needed. Integrative modalities have unique ways of perceiving disease patterns that are different from more modern approaches, and these different perspectives can be used diagnostically and therapeutically either combined with more conventional approaches, or when those approaches fall short.

Systemic calcinosis in a Quarter Horse gelding homozygous for a myosin heavy chain 1 mutation.

CASE DESCRIPTION: A 9-year-old Quarter Horse gelding was presented for lethargy, decreased appetite, polyuria and polydipsia (PU/PD), and severe muscle wasting suggestive of immune-mediated myositis. CLINICAL FINDINGS: The horse displayed lethargy, fever, tachyarrhythmia, inappetence, PU/PD, and severe epaxial and gluteal muscle wasting. Clinicopathologic findings were consistent with previously reported cases of systemic calcinosis in horses, including increased muscle enzyme activity, hyperphosphatemia, increased calcium-phosphorus product, hypoproteinemia, and an inflammatory leukogram. A diagnosis of systemic calcinosis was established by histopathologic evaluation of biopsy specimens from skeletal muscle, lung, and kidney. TREATMENT AND OUTCOME: Symptomatic treatment was complemented by IV treatment with sodium thiosulfate to reverse calcium-phosphate precipitation in soft tissue and PO aluminum hydroxide to decrease intestinal phosphorus absorption and serum phosphorus concentration. CLINICAL RELEVANCE: This is the first report in the veterinary literature of an antemortem diagnosis of systemic calcinosis in the horse that was successfully treated and had favorable long-term outcome.

Detection and inhibition of IgE antibodies reactive with cross-reactive carbohydrate determinants in an ELISA for allergen-specific IgE in horses.

BACKGROUND: It has been demonstrated that immunoglobulin (Ig)E specific for cross-reactive carbohydrate determinants (CCD) is present in the serum of sensitized humans, dogs and cats, and that these CCD-specific antibodies might confound serological testing. HYPOTHESIS/OBJECTIVE: The objective was to determine whether or not CCD-reactive antibodies occur in horses and to investigate the prevalence of CCD-reactive IgE antibodies in equine sera using a monoclonal cocktail-based enzyme-linked immunosorbent assay designed to detect allergen-specific IgE in horses, and to evaluate a means for successful inhibition of these CCD. METHODS AND MATERIALS: Sera from 28 horses suspected of clinical allergy were evaluated, with and without a proprietary inhibitor which contains carbohydrates derived from bromelain (BROM-CCD), using a panel of 72 allergens that include 15 grasses, 17 trees, nine weeds, five mites, 12 fungi, 12 insects and two environmental allergens. RESULTS: Twenty-five samples were shown to be reactive to at least one of the allergens, and 15 were reactive to 10 allergens or more. BROM-CCD had minimal effect on the mite reactivity in any of the positive samples; however, substantial inhibition for pollen allergens (trees, grasses and weeds) was demonstrable. Reduction in signal to pollens ranged from 20% to 100% for samples that were inhibited by CCD-BROM. CONCLUSIONS AND CLINICAL IMPORTANCE: These results demonstrate that CCD-reactive IgE antibodies are evident in horses and that BROM-CCD can be effective in reducing reactions with these irrelevant carbohydrates and will likely yield a more accurate in vitro allergen reactivity profile for selection of allergens included in an immunotherapeutic regime.

Diagnostic and Clinical Course of Small Colon Recurrent Impaction Associated with Severe Myenteric Ganglionopathy in A Mare.

A 10-year-old Koninklijk Warmbloed Paardenstamboek Nederland (KWPN, Netherlands-based organization for registration of the Dutch Warmblood horses) mare was evaluated three times over four months because of recurrent colic. At every referral, a physical examination revealed a small colon impaction, which partially responded to food deprivation and oral administration of water and magnesium sulphate. Due to the recurrent nature of the small colon impaction, several differential diagnoses were considered: inflammatory bowel disease (IBD), chronic salmonellosis and myenteric ganglionopathies. At first admission, an exploratory laparotomy was proposed, but the owner declined. On the second hospitalisation, the mare underwent a standing exploratory laparoscopy, but no abnormality related to the small colon was detected and resolved with a soap-based enema. At the third hospitalisation, the owner agreed to the exploratory laparotomy, which allowed surgical biopsies of the caecum and the large and small colon. Lymphomonocytic enteritis and mild myenteric ganglionitis were diagnosed. After laparotomy, the mare regularly fed and defecated, but a few days later, tachycardia, fever and abundant gastric reflux occurred. As the clinical condition rapidly deteriorated, the owner elected for euthanasia. A post-mortem histological examination showed severe chronic lymphocytic enterocolitis and typhlitis associated with the marked depletion of myenteric ganglion bodies. Small colon impaction is a very common disorder of the small colon in horses. In the presence of myenteric ganglionopathies, this case proposes the controversial matter of primary or secondary disorders of enteric neuromuscular function as the base of repeated small colon impactions of the horse. In this mare, recurrent small colon impaction was considered secondary to severe myenteric ganglionopathy associated with chronic intestinal pseudo-obstruction.

Primary Hypoparathyroidism and Recurring Hypocalcemia in a Quarter Horse Gelding-A Case Report.

Hypoparathyroidism is an uncommon endocrine disorder in the horse characterized by a transient or permanent parathyroid hormone insufficiency. Hypoparathyroidism is associated with hypocalcemia and hyperphosphatemia, primarily presenting with clinical signs consistent with hypocalcemia. This case report describes clinical presentation and treatment of a horse with severe hypocalcemia due to primary hypoparathyroidism. A 17-year-old, 542 kg Quarter Horse gelding presented for shaking and tremors. Significant findings include generalized muscle fasciculations, synchronous diaphragmatic flutter, and a markedly hypermetric hindlimb gait. Hematology revealed a moderate hyperkalemia, hyperphosphatemia, hypomagnesemia, and severe hypocalcemia. Initial treatment consisted of oral and intravenous calcium supplementation and fluid therapy. Thirty-six hours after presentation, clinical signs resolved, and treatment was discontinued. Clinical signs reoccurred after the discontinuation of treatment. A presumptive diagnosis of primary hypoparathyroidism was made based on low parathyroid hormone in the presence of low ionized calcium. The patient was maintained on oral calcium carbonate (feed grade lime) and vitamin AED supplementation. Hypoparathyroidism is rare but oral supplementation of calcium with calcium carbonate resulted in a favorable outcome with no apparent decrease in performance. Long-term supplementation may be required to prevent disease recurrence.

Cadaveric comparison of the accuracy of ultrasound-guided versus 'blind' perineural injection of the tibial nerve in horses.

During diagnostic evaluation of hindlimb lameness in horses the tibial nerve block is traditionally performed based on anatomical reference points, but it can be difficult to achieve effective local anaesthesia using this blind technique. Ultrasound (US)-guided injection could increase the accuracy of injection. The aim of this study was to compare the accuracy of both techniques. Twenty-one paired sets of cadaver hindlimbs were injected with 1 mL methylene blue using the blind or US-guided technique. There was no significant difference in stain width and length and in coloured nerve length between techniques. However, the successful rate of nerve staining was 85.7% and 47.6% for the US-guided and blind technique, respectively (P = 0.02; odds ratio 6.6; 95% confidence interval, 1.5-29.4). This study suggests that the US-guided technique is more accurate than the blind technique. However, in the treated sample, a single US-guided injection did not consistently result in nerve staining.

Pulmonary vein firing initiating atrial fibrillation in the horse: Oversized dimensions but similar mechanisms.

Atrial fibrillation is triggered by the pulmonary veins in humans. Although atrial fibrillation is known to occur in other species, the mechanisms of disease in these are not known. Here we present evidence for pulmonary vein triggers in the horse, where 3D HD Grid mapping was undertaken in the conscious state in the absence of fluoroscopy.

Acute kidney injury due to Leptospira interrogans in 4 foals and use of renal replacement therapy with intermittent hemodiafiltration in 1 foal.

Four 2-month-old foals were presented to an equine hospital with acute kidney injury caused by Leptospira interrogans infection. Clinical signs were nonspecific and included lethargy, fever, and unwillingness to nurse. The most important hematologic and clinicopathologic findings were azotemia, anemia, thrombocytopenia, hyponatremia, and hypochloremia. The diagnosis was based on urinary real-time PCR, serology using a microscopic agglutination test, or both. The most important serovars involved were L. interrogans serogroup australis serovar Bratislava and Australis. Treatment consisted of IV fluid therapy and antimicrobial treatment. Renal replacement therapy with hemodiafiltration was performed in 1 of the foals. All foals survived to discharge. This report highlights the importance of early diagnosis and treatment in foals with acute kidney injury caused by L. interrogans infection.

Changes in saliva analytes in equine acute abdominal disease: a sialochemistry approach.

BACKGROUND: The biochemical components of saliva can change in certain pathologies in horses, for example in acute abdominal disease. The aim of this study was (1) to evaluate if a panel of biochemical analytes usually used in serum can be measured in saliva of horses and (2) to study the possible changes of these biochemical analytes in saliva of horses affected by acute abdominal disease. A panel of 23 analytes was analytically validated in saliva of horses and possible changes in these analytes in a pilot study with six healthy horses and six horses with acute abdominal disease were evaluated. The analytes with significant changes were then evaluated in a larger population of 20 healthy and 37 diseased horses. RESULTS: Seven analytes showed significant increases in the pilot study which were confirmed in the larger population. The analytes which showed significant changes, and their median fold increase and significance shown in the larger population were salivary γ-glutamyl transferase (gGT, 2.3 fold, P = 0.001), creatine kinase (CK, 6.2 fold, P < 0.001), urea (2.3 fold, P = 0.001), total bilirubin (2.6 fold, P < 0.001), total proteins (3.2 fold, P < 0.001), phosphorus (P, 4.5 fold, P < 0.001) and alpha-amylase (sAA, 8.5 fold, P < 0.001). Total proteins, P and sAA showed sensitivities higher than 70% at their optimal cut-off points and a specificity of 100% in differentiating between healthy horses and those with acute abdominal disease. CONCLUSIONS: A panel of 23 biochemical analytes can be measured in saliva of horses, where gGT, CK, urea, total bilirubin, total protein, P and sAA levels are raised in horses with acute abdominal disease.

Is Electrical Nerve Stimulation the Answer for Management of Equine Headshaking?

Horses with trigeminal mediated headshaking (TMHS) have a decreased activation threshold of the trigeminal nerve and clinical signs are suspected to be a manifestation of trigeminal neuralgia. Electrical nerve stimulation (ENS) is used for management of neuralgia in humans and appears to work via gate control theory. Use of an equine specific percutaneous ENS program in over 130 TMHS horses has resulted in approximately 50% success return to previous work. Electroacupuncture may also be useful in the management TMHS. Optimization of ENS procedures for TMHS is likely to require a greater understanding of the etiopathogenesis of the aberrant neurophysiology.

Synostosis of the first and second ribs in six horses.

CASE DESCRIPTION Over a 2-year period, 6 horses (4 Selle Français, 1 Hanoverian, and 1 Thoroughbred) were referred for evaluation of forelimb lameness. All horses had radiographic evidence of synostosis of the first and second ribs (SFSR). CLINICAL FINDINGS For 1 horse, the SFSR was considered the probable cause of the lameness (grade 3/5), with a shortening of the cranial phase of the stride in the affected limb. For 3 horses, it was considered a possible cause of the lameness (grade 1/5) for the same reason. For 2 horses, SFSR was considered an incidental finding unassociated with any clinical signs. The 4 horses with lameness suspected as attributable to SFSR had a moderate to severe amount of irregularly marginated new bone formation at the site of the SFSR, with a cranial displacement of the first rib, compared with findings for the 2 horses in which the SFSR was considered incidental. A likely congenital abnormality of the first rib was first suspected on nuclear scintigraphy in the 1 horse for which it was performed or on radiography of the caudal cervical portion of the vertebral column (3 horses) or shoulder joint (2 horses). TREATMENT AND OUTCOME The horse in which SFSR was considered the probable cause of the lameness was retired to the field and remained chronically lame. Two of the 3 horses in which SFSR was considered a possible cause of lameness received an IV infusion of tiludronate disodium and mesotherapy over the caudal cervical and cranial thoracic regions; both returned to competition but with poor results. One of the 2 horses with subclinical SFSR never developed lameness on the affected side. No follow-up information was available for the other 2 horses. CLINICAL RELEVANCE SFSR can be an incidental finding in horses, with or without clinical manifestations. This abnormality should be considered as a differential diagnosis for horses with forelimb lameness and associated shortening of the cranial phase of the stride that fails to improve with diagnostic analgesic techniques.

Investigation of ventricular pre-excitation electrocardiographic pattern in two horses: clinical presentation and potential causes.

Two horses referred to the Unitat Equina, Fundació Hospital Clínic Veterinari, Universitat Autònoma de Barcelona, for unrelated clinical problems, and with no previous history of cardiac disease exhibited an intermittent ventricular pre-excitation electrocardiographic pattern during hospitalization. Both animals showed decreased plasma total and ionized magnesium concentrations, but no other relevant electrolyte disturbances were detected. Altered interventricular septal motion associated with ventricular pre-excitation beats (VPBs) was detected on M-mode echocardiography in both horses. The likely localization of an accessory pathway (AP) was identified in case 2 using pulsed-wave tissue Doppler imaging in the left anterior paraseptal location. Decreased frequency of the VPB was observed with long-term magnesium supplementation and restoration of plasma magnesium concentrations. The presence of ventricular pre-excitation electrocardiographic pattern was attributed to higher sensitivity of the AP to hypomagnesemia in both cases.

Catastrophic gastric rupture in a horse secondary to psyllium pharmacobezoars.

A mare was euthanized because of gastric rupture secondary to complete duodenal obstruction by 2 bezoars located in the pylorus and proximal duodenum. Infrared spectroscopy showed that the bezoars were composed of psyllium. The mare had been receiving treatment with a pelleted psyllium product at 4 times the recommended dosage. Veterinarians should be aware that treatment of colic in horses with pelleted psyllium products could be associated with gastric impaction.

Rupture gastrique catastrophique secondaire à des pharmacobézoards de psyllium en boulettes chez un cheval. Une jument a été euthanasiée en raison d'une rupture gastrique secondaire à une obstruction duodénale complète par deux bézoards situés dans le pylore et le duodénum proximal. La spectroscopie infrarouge a montré que les bézoards se composaient de psyllium. La jument avait reçu un traitement composé d'un produit de psyllium en boulettes à quatre fois la dose recommandée. Les vétérinaires devraient être au courant que le traitement des coliques chez les chevaux avec des produits de psyllium en boulettes pourrait être associé à une impaction gastrique.(Traduit par Isabelle Vallières).

Determination of irritant threshold concentrations of multiple tree, grass, weed and mould allergens for intradermal testing of horses residing in the southern USA.

BACKGROUND: Appropriate allergen threshold concentrations (TCs) for intradermal testing (IDT) have not been established in horses for many pollen and mould allergens. OBJECTIVES: To determine the TCs in non-allergic horses and describe the frequency of late phase reactions for 26 allergens, including trees, grasses, weeds and moulds in horses residing in the southern Unites States. ANIMALS: Twenty four clinically normal horses in the southern United States. METHODS: Threshold concentrations for different allergens were determined using IDT subjective measurements at 30 minutes. Delayed reactions were evaluated at 4 and 24 h. RESULTS: Threshold concentrations (all PNU/mL) were established for eight tree allergens (black willow 1,000, box elder 1,000, live oak 1,000, pecan 2,000, white ash 4,000, red oak 4,000, red mulberry 2,000 and green ash 2,000); two grass allergens (Johnson grass 250 PNU/mL and Kentucky blue grass 500 PNU/mL); two weeds (carelessweed 1,000 PNU/mL, great ragweed 500 PNU/mL) and one mould (Curvularia 8,000 PNU/mL). The TC was not determined due to excessive reactivity at the lowest concentration tested (1,000 PNU/mL) for bahia and perennial rye grass. Eleven other allergens did not meet the criteria to establish a TC when evaluated at 30 min due to lack of positive reactions. Multiple allergens caused positive reactions in ≥10% of horses at 4 h. Reactions at 24 h were rare with the exception of one horse. CONCLUSIONS AND CLINICAL IMPORTANCE: This study identified intradermal TC for multiple pollen and mould allergens in horses. These values may prove useful for optimizing allergen concentrations for IDT of allergic horses.

Equine antibody response to larval Parascaris equorum excretory-secretory products.

Parascaris equorum is an intestinal nematode of foals and young horses that can produce mild to severe pathology. Current diagnosis is limited to detection of patent infections, when parasite eggs are identified during fecal examinations. This study examined the use of larval P. equorum excretory-secretory (ES) products in a western blot test for diagnosis of prepatent equine P. equorum infection. Sera from adult mares negative for patent P. equorum infections, foals prior to consuming colostrum, and P. equorum infected foals were used as controls in this study. Study samples included sera from 18 broodmares prior to parturition and sera from their foals throughout the process of natural infection. Sera from study horses were examined for IgG(T) antibody recognition of ES products. Foals naturally infected with P. equorum possessed IgG(T) antibodies against 19kDa, 22kDa, 26kDa, and 34kDa ES products. However, passive transfer of colostral antibodies from mares was shown to preclude the use of the crude larval ES product-based western blot test for diagnosis of prepatent P. equorum infections in foals.