Cody J. Alcott

Multinodular pulmonary fibrosis in five horses

CASE DESCRIPTION 5 horses were evaluated because of decreased appetite, weight loss, fever, cough, tachypnea, and respiratory distress. CLINICAL FINDINGS Tachycardia, tachypnea, increased respiratory effort, lethargy, fever, poor body condition, and nasal discharge were detected in various combinations on initial physical examination. Evaluation of the lower portion of the respiratory tract via radiography and ultrasonography revealed a severe nodular interstitial pattern. Histologic examination of lung tissue revealed interstitial expansion of alveolar parenchyma with collagen, intraluminal accumulation of neutrophils and macrophages within the alveoli, and occasional intranuclear inclusion bodies within alveolar macrophages. Equine herpesvirus type 5 was detected in samples of lung tissue, bronchoalveolar lavage fluid, or both via polymerase chain reaction assay in all cases. A diagnosis of equine multinodular pulmonary fibrosis (EMPF) was established. TREATMENT AND OUTCOME Horses were provided supportive treatment and were administered a variety of medications including corticosteroids and acyclovir. Two horses survived and returned to their previous level of activity. Three horses were euthanized because of either deterioration of clinical condition (n=2) or failure to improve within 4 weeks of initiation of treatment (1). CLINICAL RELEVANCE EMPF should be considered as a differential diagnosis for adult horses with interstitial pneumonia and should be suspected on the basis of characteristic radiographic, ultrasonographic, and histopathologic findings. Equine herpesvirus type 5 is found in association with EMPF; although the exact pathogenic role this virus plays in EMPF is unknown, equine herpesvirus type 5 may be an etiologic agent or cofactor in the development of EMPF.

Factors associated with recovery from paraplegia in dogs with loss of pain perception in the pelvic limbs following intervertebral disk herniation

OBJECTIVE To investigate associations between recovery of locomotion and putative prognostic factors in dogs with loss of deep pain perception in the pelvic limbs caused by intervertebral disk herniation (IVDH). DESIGN Prospective cohort study. ANIMALS 78 client-owned dogs evaluated for IVDH that underwent spinal decompression surgery. PROCEDURES Dogs with complete loss of deep pain perception in the pelvic limbs and tail underwent routine examinations, advanced imaging, and spinal decompression surgery in accordance with standards of practice and owner consent. For each dog, information was prospectively collected on duration of clinical signs prior to onset of paraplegia; delay between onset of paraplegia and initial referral evaluation; date of recovery of locomotion, death, or euthanasia (3-month follow-up period); and whether dogs had received corticosteroid drugs before surgery. Severity of spinal cord compression at the lesion epicenter was measured via CT or MRI. RESULTS 45 of 78 (58%) of dogs recovered the ability to ambulate independently within 3 months after spinal decompression surgery. No evidence of prognostic value was identified for any of the investigated factors; importantly, a greater delay between onset of paraplegia and referral evaluation was not associated with a poorer prognosis. CONCLUSIONS AND CLINICAL RELEVANCE In this group of dogs with IVDH, immediacy of surgical treatment had no apparent association with outcome. The prognosis for recovery may instead be strongly influenced by the precise nature of the initiating injury.

Baseline plasma cortisol and ACTH concentrations and response to low-dose ACTH stimulation testing in ill foals

OBJECTIVE To evaluate baseline plasma cortisol and ACTH concentrations and responses to low-dose ACTH stimulation testing in ill foals. DESIGN Cross-sectional study. ANIMALS 58 ill foals. PROCEDURES Baseline cortisol and ACTH concentrations and cortisol concentrations after administration of a low dose of cosyntropin were determined within 6 hours after admission. Foals were assigned to 4 groups on the basis of age (<or=24 hours vs 1 to 56 days) and presence of septicemia (yes vs no). Values were compared among groups and with values previously reported for healthy foals. RESULTS Plasma cortisol concentrations 30 and 60 minutes after cosyntropin administration in foals<or=24 hours old were significantly higher than corresponding cortisol concentrations in older foals. In all 4 groups, plasma cortisol concentration 30 minutes after cosyntropin administration was significantly higher than baseline cortisol concentration or concentration 60 minutes after cosyntropin administration. No differences in baseline cortisol or ACTH concentration or in the ACTH-to-cortisol ratio were detected between groups or when ill foals were compared with healthy foals. A small number of ill foals had low baseline cortisol and ACTH concentrations or low responses to cosyntropin administration, compared with healthy foals. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that most ill foals in the present study population had adequate responses to cosyntropin administration. However, a small subset of ill foals appeared to have dysfunction of the hypothalamic-pituitary-adrenal axis.

Alloimmune neonatal neutropenia and neonatal isoerythrolysis in a Thoroughbred colt

A 3-day-old Thoroughbred colt was originally presented for treatment of neonatal isoerythrolysis, which was treated with a blood transfusion. However, persistent neutropenia was observed despite the absence of detectable infection. Subsequently, a granulocyte agglutination test was performed by incubating the colt’s neutrophils with the mare’s serum; results were positive, leading to a clinical diagnosis of alloimmune neonatal neutropenia. The diagnosis was further supported via flow cytometric analysis. The colt was hospitalized and treated prophylactically with antimicrobials and 4 separate doses of recombinant human granulocyte colony-stimulating factor (rhG-CSF; 1.4–3.5 µg/kg, subcutaneously) in attempts to maintain the neutrophil count within reference intervals over a 4-week period. The colt’s neutrophil count increased after administration of rhG-CSF and eventually stabilized within reference intervals by day 20. The colt maintained normal neutrophil counts after discharge and was reportedly healthy at 6 months of age. Alloimmune neonatal neutropenia should be considered in foals with persistent neutropenia in the absence of infection. Alloimmune neonatal neutropenia can be treated with prophylactic antimicrobials combined with rhG-CSF with a favorable outcome.

Clinical and Immunomodulating Effects of Ketamine in Horses with Experimental Endotoxemia

BACKGROUND Ketamine has immunomodulating effects both in vitro and in vivo during experimental endotoxemia in humans, rodents, and dogs. HYPOTHESIS Subanesthetic doses of ketamine will attenuate the clinical and immunologic responses to experimental endotoxemia in horses. ANIMALS Nineteen healthy mares of various breeds. METHODS Experimental study. Horses were randomized into 2 groups: ketamine-treated horses (KET; n = 9) and saline-treated horses (SAL; n = 10). Both groups received 30 ng/kg of lipopolysaccharide (LPS, Escherichia coli, O55:B5) 1 hour after the start of a continuous rate infusion (CRI) of racemic ketamine (KET) or physiologic saline (SAL). Clinical and hematological responses were documented and plasma concentrations of tumor necrosis factor-α (TNF-α) and thromboxane B(2) (TXB(2)) were quantified. RESULTS All horses safely completed the study. The KET group exhibited transient excitation during the ketamine loading infusion (P < .05) and 1 hour after discontinuation of administration (P < .05). Neutrophilic leukocytosis was greater in the KET group 8 and 24 hours after administration of LPS (P < .05). Minor perturbations of plasma biochemistry results were considered clinically insignificant. Plasma TNF-α and TXB(2) production peaked 1.5 and 1 hours, respectively, after administration of LPS in both groups, but a significant difference between treatment groups was not demonstrated. CONCLUSIONS AND CLINICAL IMPORTANCE A subanesthetic ketamine CRI is well tolerated by horses. A significant effect on the clinical or immunologic response to LPS administration, as assessed by clinical observation, hematological parameters, and TNF-α and TXB(2) production, was not identified in healthy horses with the subanesthetic dose of racemic ketamine utilized in this study.

Physiologic effects of nasopharyngeal administration of supplemental oxygen at various flow rates in healthy neonatal foals

OBJECTIVE To evaluate the effects of various flow rates of oxygen administered via 1 or 2 nasal cannulae on the fraction of inspired oxygen concentration (FIO2) and other arterial blood gas variables in healthy neonatal foals. ANIMALS 9 healthy neonatal (3- to 4-day-old) foals. PROCEDURES In each foal, a nasal cannula was introduced into each naris and passed into the nasopharynx to the level of the medial canthus of each eye; oxygen was administered at 4 flow rates through either 1 or both cannulae (8 treatments/foal). Intratracheal FIO2, intratracheal end-tidal partial pressure of carbon dioxide, and arterial blood gas variables were measured before (baseline) and during unilateral and bilateral nasopharyngeal delivery of 50, 100, 150, and 200 mL of oxygen/kg/min. RESULTS No adverse reactions were associated with administration of supplemental oxygen except at the highest flow rate, at which the foals became agitated. At individual flow rates, significant and dose-dependent increases in FIO2, PaO2, and oxygen saturation of hemoglobin (SaO2) were detected, compared with baseline values. Comparison of unilateral and bilateral delivery of oxygen at similar cumulative flow rates revealed no differences in evaluated variables. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that administration of supplemental oxygen via nasal cannulae appeared to be a highly effective means of increasing FIO2, PaO2, and SaO2 in neonatal foals. These findings may provide guidance for implementation of oxygen treatment in hypoxemic neonatal foals.

Agreement between arterial partial pressure of carbon dioxide and saturation of hemoglobin with oxygen values obtained by direct arterial blood measurements versus noninvasive methods in conscious healthy and ill foals

OBJECTIVE To determine agreement between indirect measurements of end-tidal partial pressure of carbon dioxide (PetCO(2)) and saturation of hemoglobin with oxygen as measured by pulse oximetry (SpO(2)) with direct measurements of PaCO(2) and calculated saturation of hemoglobin with oxygen in arterial blood (SaO(2)) in conscious healthy and ill foals. DESIGN Validation study. ANIMALS 10 healthy and 21 ill neonatal foals. PROCEDURES Arterial blood gas analysis was performed on healthy and ill foals examined at a veterinary teaching hospital to determine direct measurements of PaCO(2) and PaO(2) along with SaO(2). Concurrently, PetCO(2) was measured with a capnograph inserted into a naris, and SpO(2) was measured with a reflectance probe placed at the base of the tail. Paired values were compared by use of Pearson correlation coefficients, and level of agreement was assessed with the Bland-Altman method. RESULTS Mean ± SD difference between PaCO(2) and PetCO(2) was 0.1 ± 5.0 mm Hg. There was significant strong correlation (r = 0.779) and good agreement between PaCO(2) and PetCO(2). Mean ± SD difference between SaO(2) and SpO(2) was 2.5 ± 3.5%. There was significant moderate correlation (r = 0.499) and acceptable agreement between SaO(2) and SpO(2). CONCLUSIONS AND CLINICAL RELEVANCE Both PetCO(2) obtained by use of nasal capnography and SpO(2) obtained with a reflectance probe are clinically applicable and accurate indirect methods of estimating and monitoring PaCO(2) and SaO(2) in neonatal foals. Indirect methods should not replace periodic direct measurement of corresponding parameters.

Plasma Vasopressin Concentrations in Healthy Foals from Birth to 3 Months of Age

BACKGROUND Arginine vasopressin (AVP) has received increased attention in equine critical care but there is minimal information of AVP concentration in foals. The clinical usefulness of measuring AVP in ill foals depends on knowledge of age-related changes in AVP concentrations in healthy foals. HYPOTHESIS Plasma AVP concentrations will be significantly different when measured from birth to 3 months of age in healthy foals. ANIMALS Thirteen healthy university-owned foals. METHODS Prospective, observational study. Blood was collected from healthy foals at birth and 3, 5, 7, 10, 14, 21, 28, 42, 56, and 84 days of age. Plasma was harvested and plasma AVP concentrations were determined by radioimmunoassay. RESULTS No statistically significant differences were detected in plasma AVP concentrations over the study period. Plasma AVP concentrations over the entire study period was 6.2+/-2.5 pg/mL. CONCLUSIONS AND CLINICAL IMPORTANCE There was no age-related variation in plasma AVP concentrations detected in healthy foals from birth to 3 months of age suggesting that AVP concentrations are similar across foals of these ages.

Shunt tube placement for amelioration of cerebrospinal fluid flow obstruction caused by spinal cord subarachnoid fibrosis in dogs

OBJECTIVE To describe a novel technique for ameliorating cerebrospinal fluid flow obstruction secondary to pia-arachnoid fibrosis in dogs and report outcome. STUDY DESIGN Descriptive report and retrospective case series. ANIMALS Dogs with cerebrospinal fluid (CSF) flow obstruction (n = 7). METHODS Medical records were searched for dogs that had a subarachnoid-subarachnoid shunt placed for treatment of CSF flow obstruction. Data collected included age, sex, breed, clinical signs and duration of signs prior to examination, neurologic status and localization prior to surgery, pre-surgical diagnostics, surgical technique, histopathology, postoperative neurologic examination, time to discharge from hospital, and outcome. RESULTS All dogs were diagnosed at surgery with a fibrotic adhesion between the arachnoid and pia mater. A subarachnoid shunting tube was implanted to allow CSF flow across the lesion site. Five dogs showed improvement of clinical signs, 3 of which showed complete recovery and 2 of which showed improvement without resolution of all clinical signs. Two dogs showed no change at 7 and 24 months postoperatively. CONCLUSION Bridging a region of pia-arachnoid fibrosis with a tube placed in the subarachnoid space can ameliorate or prevent progression of associated clinical signs.

The Association of Specific Constituents of the Fecal Microbiota with Immune-Mediated Brain Disease in Dogs.

Meningoencephalomyelitis of unknown origin (MUO) is a common, naturally-occurring, clinical disease of pet dogs. It is an immune-mediated condition that has many similarities with experimental autoimmune encephalitis (EAE) in rodents and so investigation of its pathogenesis may aid in understanding factors that contribute to development of multiple sclerosis in people. Gut microbiota are known to modulate immune responses that influence susceptibility to immune-mediated brain disease. In this study we aimed to compare abundance of specific constituents of the fecal microbiota, namely Faecalibacterium prausnitzii and Prevotellaceae, between dogs diagnosed with MUO and matched controls. Fecal samples were obtained from 20 dogs diagnosed with MUO and 20 control dogs matched for breed, age and gender. Bacterial abundance was measured using qPCR and 16S rRNA sequencing. We found that Prevotellaceae were significantly less abundant in cases compared with controls (p = 0.003) but there was no difference in abundance of F.prausnitzii. There was no evidence of other differences in gut microbiota between groups. These data, derived from this naturally-occurring canine clinical model, provide strong corroborative evidence that high abundance of Prevotellaceae in the gut is associated with reduced risk for developing immune-mediated brain disease.