Single‐Layer Centrifugation Reduces Equine Arteritis Virus Titre in the Semen of Shedding Stallions

Several countries have adopted strategies for preventing and/or controlling equine viral arteritis based on vaccination and restricting the breeding activities of carrier stallions. However, in some cases, carrier stallions are only identified after they have transmitted virus to a mare. Therefore, a mechanism for separating virus from spermatozoa in the semen of carrier stallions would facilitate control measures for preventing disease transmission. In this study, the use of several modifications of single‐layer centrifugation (SLC, SLC with an inner tube and double SLC) through Androcoll‐E, a species‐specific colloid were evaluated for their ability to separate spermatozoa from virus in ejaculates from carrier stallions. The three types of SLC significantly reduced the virus titre in fresh semen at 0 h and in stored semen at 24 h (p < 0.001) but did not completely eliminate the virus. Sperm motility parameters such as total motility and progressive motility were significantly increased after colloid centrifugation, whereas curvilinear velocity and amplitude of lateral head deviation were decreased, and the remainder (straight line velocity, average path velocity, straightness, linearity, wobble and beat cross‐frequency) were not significantly affected by the processing. Although virus titres were reduced in the SLC samples, significant levels of infectivity still remained, especially in stallions shedding large amounts of virus. It remains to be determined whether SLC‐processed sperm samples from stallions shedding low virus titres retain sufficient equine arteritis virus to cause infection in mares through artificial insemination.     

Jejunocolic Anastomosis for the Surgical Management of Recurrent Cecal Impaction in a Horse

A 5-year-old Thoroughbred gelding with recurrent cecal impaction refractory to medical management was treated with a side-to-side jejunocolic anastomosis. Cecal impaction did not recur after surgery. The horse gained weight and performed successfully for 14 months, but experienced three episodes of mild abdominal pain between 14 and 20 months after surgery. Mild cecal gas distention and firm ingesta in the colon were detected on rectal examination. The horse's feces remained soft after surgery, except during the colic episodes when dry, firm feces were passed.     

Evaluation of Intestinal Staples for End-to-end Anastomosis of the Small Intestine in the Horse

Segments of jejunum that had been subjected to ischemia 1 month previously were resected en bloc in six horses. Everted end-to-end anastomoses were performed by application of double rows of stainless steel staples. The anastomotic sites were examined at 3 weeks, 3 months, 6 months, and 8 months postoperatively. All but one of the horses experienced colic at some point after the second postoperative week. At 3 weeks, there was extensive adhesion and stricture formation associated with the anastomoses. With increasing time postoperatively, there were progressively less severe adhesions and strictures. At 6 and 8 months, there was separation of the muscularis with noticeable thinning at the anastomotic site.     

Taking Advantage of the Positive Side‐Effects of Smallpox Vaccination

From the introduction of smallpox vaccination approximately 200 years ago right up to its discontinuation (1980), reports by physicians and scientists about positive side‐effects such as healing of chronic skin rashes, reduced susceptibility to various infectious diseases, e.g. measles, scarlet fever and whooping cough, and even the prophylactic use of the vaccination, e.g. against syphilis, were published again and again. Comparison with the period after cessation of vaccination confirms the experiences of the above vaccinators. As early as 1956, targeted research on these observations led to evidence of the ‘ring‐zone phenomenon’, i.e. the production of soluble antiviral substances in infected chicken embryos and cell cultures. With the help of modern immunological and bioengineering methods, it was later possible to demonstrate that these effects are based on the activation of lymphoreticular cells and the regulatory effect of certain cytokines within the context of the non‐specific immune system. These findings led to the development of paramunization with paraspecific vaccines from highly attenuated animal pox viruses. During attenuation, deletions in the virus DNA occur. Attenuated animal pox strains are therefore suited for the production of vector vaccines. The fact that these vector vaccines demonstrate an especially high level of paraspecific efficacy and lack harmful effects is likewise the result of the attenuated animal pox viruses. Optimum regulation of the entire immune system leads to increased paramunity already in the first few days after vaccination and to enhanced antigen recognition and thus accelerated commencement of specific immunity.     

Transfer of Deep Circumflex Iliac Flaps to the Tarsus by Microvascular Anastomosis in the Horse

Eighteen deep circumflex iliac flaps were elevated in healthy adult horses. Four flaps survived well when elevated as islands, but five orthotopic flaps and nine heterotopic flaps transferred to the tarsus and face failed. Technical reasons could explain the failure of the orthotopic flaps, but not the heterotopic flaps. Failure of the heterotopic flaps was apparently caused by the no-reflow phenomenon.     

A Potential Technique Error in Stapled Side-to-Side Anastomosis of the Small Intestine of the Horse

Anastomotic leakage was noted to occur at the junction of the staple lines used to create the stoma during small intestine side-to-side anastomosis. The anastomosis was performed in a clinical equine patient by joining the lateral surfaces of the intestinal segments using a gastrointestinal anastomosis stapling instrument (GIA). The cause of this problem was investigated by performing six anastomoses in the jejunum of a single anesthetized adult horse using the GIA; three anastomoses were created by joining the antimesenteric edges of the bowel segments and three anastomoses were created by joining the lateral surfaces of the bowel segments. Bowel segments were then dissected to examine the stoma and the integrity of the staple lines. No defects were detected in anastomoses performed by joining the antimesenteric edges. Anastomoses performed by joining the lateral surfaces all had a defect at the junction of the double rows of staples used to create the stoma. Such defects would have allowed leakage of fluid and/or ingesta at the anastomotic site.     

Single‐port laparoscopic incisional hernia repair in a horse

A 16‐year‐old Italian Saddle Horse gelding was referred for treatment of an incisional hernia that developed 7 months after a ventral midline laparotomy for treatment of acute abdominal pain. Physical examination revealed a hernia approximately 20 cm long and 15 cm wide on the ventral aspect of the abdomen. Ultrasonography revealed the dimensions of the hernia ring to be approximately 15 cm in length and 10 cm in width. A single‐port laparoscopic incisional hernia repair using an operating 0° laparoscope was performed with an appropriately sized (24 × 18 cm) piece of mesh fixed in place with simple interrupted transabdominal sutures. At 4 weeks post operatively, follow‐up physical examination and ultrasonography confirmed healing of the surgical site with no evidence of hernia recurrence. The same evaluation was done 6 months post operatively, and the horse returned to its previous level of activity 8 months post operatively. In horses, laparoscopic application of mesh should be considered among the treatment options for incisional hernia. In the present case, this technique was performed with a single port using an operative laparoscope, in contrast to the multiportal techniques reported previously. The case presented here demonstrates that single‐port laparoscopic herniorrhaphy is feasible, and allows proper placement of an expanded polytetrafluoroethylene intraperitoneal mesh in horses     

Mandibular squamous cell carcinoma in a 5‐year‐old Tennessee Walking Horse

Squamous cell carcinoma (SCC) is the second most common neoplasm reported in the horse, but occurs rarely in the oral cavity. Clinical signs may be insidious in onset and mimic other non‐neoplastic processes, thus delaying appropriate treatment. Timely evaluation and advanced diagnostic imaging may offer the opportunity to initiate definitive treatment. This report describes a young gelding with mandibular SCC that was evaluated for mandibular swelling failing to respond to symptomatic therapy.     

Soft tissue sarcomas in the pharyngeal region of a 5‐year‐old Quarter Horse mare

This case report describes the identification of multiple soft tissue sarcomas in the pharyngeal region of a 5‐year‐old Quarter Horse mare. Diagnostic work‐up included physical examination, radiography, ultrasonography, endoscopic examination of upper airways and guttural pouch, and post mortem examination with histopathology. Humane euthanasia was indicated due to the chronicity of the condition, prognosis and financial constraints.     

Pharmacokinetics of Single‐Dose Rectal Zonisamide Administration in Normal Dogs

Background

Few medications are available for parental administration to animals with seizures. Rectal administration of medications is often used if the animal cannot be administered oral medications.

Hypothesis/Objectives

To determine the pharmacokinetic differences in zonisamide when administered rectally in either of 2 vehicles and PO to dogs.

Animals

Eight healthy research dogs.

Methods

Randomized cross‐over design. Zonisamide, 10 mg/kg, was administered rectally in polyethylene glycol (PEG‐R), rectally in water (H₂O‐R), and as an oral capsule. Plasma zonisamide concentrations were measured until 72 hours after administration. Zonisamide was quantitated by HPLC and plasma concentration versus time curve data was analyzed by using noncompartmental modeling.

Results

Mean maximum plasma zonisamide concentrations (μg/mL) were significantly higher after oral administration (11.56 ± 4.04) compared to H₂O‐R (5.00 ± 1.83) (P = .004). Disappearance half‐life (hours) and mean time to maximum concentration (hours) were not significantly different between methods of administration. Mean relative bioavailability of PEG‐R (85 ± 69%) was significantly higher than that of H₂O‐R (53 ± 37%) (P = .039). Dogs tolerated all dosing forms with no evidence of adverse effects.

Conclusions and Clinical Importance

The vehicle in which zonisamide is dissolved influences rectal bioavailability, with PEG preferred to H₂O‐R. Because of the prolonged time to maximum concentration, rectal administration of zonisamide should not be used to treat status epilepticus in dogs. A dose higher than what was used in this study might be necessary, if currently recommended minimum therapeutic concentrations (10 μg/mL) are to be achieved with a single‐dose administration.     

Phase I Dose Escalation of Single‐Agent Vinblastine in Dogs

Background: Vinblastine (VBL) is commonly used in dogs at a dosage of 2.0 mg/m². The minimal toxicity observed at this dosage indicates that higher dosages might be well tolerated. Hypothesis: The maximum tolerated dosage (MTD) for a single VBL treatment is higher than the previously published dosage of 2.0 mg/m². Animals: Twenty‐three dogs with lymphoma or cutaneous mast cell tumors. Methods: Dogs received 1 single‐agent VBL treatment IV. The starting dosage was 3.0 mg/m², and dosages were increased in increments of 0.5 mg/m² in cohorts of 3 dogs. Hematologic toxicity was assessed with weekly CBCs. Gastrointestinal toxicity was assessed from medical histories from owners. Once the MTD was determined, additional dogs were treated with VBL at that dosage. Dogs whose cancers responded to VBL continued to receive treatments q2–3 weeks. Results: VBL dosages ranged from 3.0 to 4.0 mg/m². Neutropenia was the dose‐limiting toxicity, with the nadir identified 7 days after treatment and resolving by 14 days after treatment. The MTD was 3.5 mg/m². Sixteen dogs were treated at this dosage, and 3 experienced severe toxicity characterized by asymptomatic grade 4 neutropenia, febrile grade 4 neutropenia, and death. Gastrointestinal toxicity was mild and self‐limiting. Preliminary evidence of antitumor activity was identified in 2 of 12 dogs with lymphoma treated at the MTD. Conclusions and Clinical Importance: In dogs, single‐agent VBL is well tolerated at a dosage of 3.5 mg/m² IV. At this dosage, the minimum safe treatment interval is q2 weeks, and adjunct treatment with prophylactic antibiotics should be considered.