J. M. Ensink

Penile and preputial tumours in the horse: A retrospective study of 114 affected horses

REASONS FOR PERFORMING STUDY Preputial and penile tumours are more common in horses than in other domestic animals, but no large surveys of male horses with tumours of the external genitalia are available. OBJECTIVE To present a retrospective analysis of male horses with neoplasms of the external genitalia. METHODS The penile and preputial tumours of 114 horses were evaluated. Data recorded included age, gelding or stallion and breed; type and site of lesion; involvement of regional lymph nodes; histopathology (including grading of squamous cell carcinoma); and results of radiographic examination of the thorax. RESULTS Mean age of horses was 19.5 years with no apparent breed predilection. Common presenting clinical signs were irregularities (e.g. the presence of a mass and/or ulceration) on the integument of the penis and prepuce, and purulent or sanguineous discharge from preputial orifice. Squamous cell carcinoma (SCC) was the most prevalent neoplasm followed by papillomas and melanomas. A basal cell carcinoma, neurofibrosarcoma, adenocarcinoma or fibrosarcoma were each found on single horses. Squamous cell carcinomas with poor differentiation had a higher tendency to metastasise than did more differentiated tumours. CONCLUSIONS Squamous cell carcinoma is the most common urogenital tumour of the male horse and occurs primarily in old horses. Horses with poorly differentiated SCCs tend to have a higher incidence of regional metastases. Pathology of lymph nodes, even when not palpably enlarged, is a valuable diagnostic exercise. Radiology of the thorax to detect lung metastases is of little value.

Brain abscesses as a metastatic manifestation of strangles: symptomatology and the use of magnetic resonance imaging as a diagnostic aid

REASONS FOR PERFORMING STUDY The occurrence of unexpectedly high numbers of horses with neurological signs during two outbreaks of strangles required prompt in-depth researching of these cases, including the exploration of magnetic resonance imaging (MRI) as a possible diagnostic technique. OBJECTIVES To describe the case series and assess the usefulness of MRI as an imaging modality for cases suspected of space-occupying lesions in the cerebral cavity. METHODS Four cases suspected of suffering from cerebral damage due to Streptococcus equi subsp. equi infection were examined clinically, pathologically, bacteriologically, by clinical chemistry (3 cases) and MRI (2 cases). In one case, MRI findings were compared to images acquired using computer tomography (CT). RESULTS In all cases, cerebral abscesses positive for Streptococcus equi subsp. equi were found, which explained the clinical signs. Although the lesions could be visualised with CT, MRI images were superior in representing the exact anatomic reality of the soft tissue lesions. CONCLUSIONS The diagnosis of bastard strangles characterised by metastatic brain abscesses was confirmed. MRI appeared to be an excellent tool for the imaging of cerebral lesions in the horse. POTENTIAL CLINICAL RELEVANCE The high incidence of neurological complications could not be explained but possibly indicated a change in virulence of certain strains of Streptococcus equi subsp. equi. MRI images were very detailed, permitting visualisation of much smaller lesions than demonstrated in this study and this could allow prompt clinical intervention in less advanced cases with a better prognosis. Further, MRI could assist in the surgical treatment of brain abscesses, as has been described earlier for CT.

Penile and preputial squamous cell carcinoma in the horse: a retrospective study of treatment of 77 affected horses.

REASONS FOR PERFORMING STUDY The most common penile and preputial neoplasm in the horse is the squamous cell carcinoma (SCC), but no large surveys of treatment and effects of the grade of the tumour, based on the degree of differentiation, on outcome of affected horses are available. OBJECTIVES Analysis of treatment of male horses affected with SCC of the external genitalia and long-term results of treatment. METHODS Seventy-seven cases of SCC were evaluated. Data recorded included treatment, outcome, post operative histopathology and retrospective tumour grading. RESULTS Treatments included: cryosurgery, excision, partial phallectomy, partial phallectomy and sheath ablation, and en bloc penile and preputial resection with penile retroversion and removal of inguinal lymph nodes. The incidence of recurrence after partial phallectomy was 25.6% (10/39) and following incomplete removal was 17.9% (7/39). The incidence of recurrence after en bloc resection with retroversion was 12.5% (1/8). In horses with confirmed inguinal lymph node metastasis, the incidence of recurrence was 25.0% (1/4). Poorly differentiated SCCs were more likely to metastasise than well differentiated SCCs, and there was a greater chance that the treatment would be unsuccessful. The success of treatment, complete removal and in preventing recurrence of the tumour, of male horses with SCC of the external genitalia was 55.7%. CONCLUSIONS Horses that receive only partial phallectomy for treatment for SCC of the external genitalia have a high incidence of recurrence in contrast to horses that receive an en bloc resection. Tumour grading of SCC can help predict prognosis and guide selection of treatment.

Side effects of oral antimicrobial agents in the horse: a comparison of pivampicillin and trimethoprim/sulphadiazine

To evaluate the side effects of oral pivampicillin and trimethoprim/ sulphadiazine, 200 horses receiving these antimicrobial agents were studied. The horses received either trimethoprim/ sulphadiazine (30 mg/kg twice daily) or pivampicillin (25 mg/kg twice daily) for three or more days. No adverse effects other than loose faeces and diarrhoea were detected. The risk of diarrhoea was significantly less after the oral administration of pivampicillin (3 per cent) than after trimethoprim/ sulphadiazine (7 per cent). Horses whose appetite was reduced appeared to be predisposed to develop diarrhoea after the administration of either oral antimicrobial agent.

Penile and preputial tumours in the horse: literature review and proposal of a standardised approach.

Penile and preputial tumours are not uncommon in the horse, but can cause discomfort and lead to serious complications. Several types of tumour of the male external genitalia have been described. The most common type is the squamous cell carcinoma (SCC), which is found mainly in older horses. Reports of a breed predilection for penile tumour formation are equivocal, but castration, coat colour, poor hygiene and various infectious agents have all been suggested to predispose to the development of some types of tumour (e.g. SCC, papilloma and melanoma). Careful assessment of the primary tumour is an important first step in the design of an optimal treatment protocol. Invasiveness, differentiation grade, tumour size and presence of metastases are all relevant to the decision to pursue additional diagnostic procedures or specific treatment options. To date, no standard protocol has been reported for the approach to penile tumours in the horse and treatments range from minimally invasive therapies (e.g. topical use of 5-fluorouracil) to radical surgical interventions (e.g. en bloc penile and preputial resection with penile retroversion). Completeness of removal of the neoplasm and therefore risk of recurrence is highly dependent on the type of therapy chosen. However, the size and histopathological features of the primary tumour are also important factors with respect to the likelihood of recurrence. This review describes the most common penile and preputial neoplasms in the horse, and outlines a standard protocol aimed at arriving at a specific diagnosis and tailoring the therapeutic approach accordingly.

Expression of p53, Ki67, EcPV2- and EcPV3 DNA, and viral genes in relation to metastasis and outcome in equine penile and preputial squamous cell carcinoma

REASONS FOR PERFORMING STUDY Equine penile and preputial squamous cell carcinoma (SCC) is a potentially lethal disease of which little is known regarding the relationship between tumour characteristics and prognosis. OBJECTIVES To assess the relationship between tumour differentiation grade (tumour subtype), presence of papillomaviruses, expression of viral genes (E2, E6, L1), nuclear proteins p53 and Ki67 and metastasis in equine penile and preputial SCC and to assess the relationship of tumour subtype, presence of papillomavirus type 2, p53 and Ki67 with survival. STUDY DESIGN Retrospective case-control study using archived material. METHODS Samples (n = 103) from 87 horses with penile and/or preputial intraepithelial neoplasia (PIN), papilloma or SCC and corresponding case files were evaluated. Tumours were graded microscopically and p53 and Ki67 expression evaluated immunohistochemically. Equine papillomavirus (EcPV) types 2 and 3 DNA was detected by conventional PCR. Real-time PCR was used for quantification of E2, E6 and L1 mRNA. RESULTS Equine papillomavirus type 2 DNA was detected in 89.4% and EcPV3 in 1.5% of horses. No differences in quantitative expression of E2, E6 and L1 oncogenes between subtypes were found. Expression of p53 and occurrence of metastasis were positively correlated to a less differentiated subtype (r = 0.429, P<0.001 and r = 0.769, P = 0.001, respectively). Differences in survival between subtypes were significant (log Rank P<0.001); horses with less differentiated tumours were more likely to die of the disease (papilloma 8.3%; G1 26.1%; G2 26.3%; G3 63.3%). CONCLUSIONS In equine penile and preputial SCC, tumour grading is an important prognosticator for survival and a predictor for presence of metastases. Expression of p53 and Ki67 and presence or expression of EcPV2 and EcPV3 do not appear to be important prognosticators.

Single intraoperative administration of antibiotic to cows with caecal torsion: Wound infection and postoperative performance. A retrospective and prospective study.

Summary Wound infection and postoperative performance after a single intra-abdominal administration of 9 g sodium ampicillin in cows operated on for caecal dilatation or torsion (n=33) were evaluated. In the 25 animals that left the clinic in good health (76% short-term survival), no wound infection occurred. Postoperative performance was normal in 21 of these animals (84%). The figures for short-term survival and postoperative performance are comparable to those from a retrospective study of 169 animals operated on between 1985 and 1990. Single intra- abdominal administration of sodium ampicillin during surgery provides good protection against infection without negative effects on the postoperative performance.

Bioavailability of pivampicillin and ampicillin trihydrate administered as an oral paste in horses.

Summary Pivampicillin was administered as an oral paste to five healthy adult horses, and an oral paste with ampicillin trihydrate was administered to three horses. Pivampicillin was administered to both starved and fed horses, ampicillin trihydrate was administered to fed horses only: The dose of pivampicillin was 19.9 mg/kg, and the dose of ampicillin trihydrate was 17 mg/kg. Both doses are equivalent on a molecular basis to 15 mg/kg ampicillin. Ampicillin concentrations in plasma were determined up to 24 hours after administration. After administration of pivampicillin to starved and fed horses the mean areas under the plasma concentration-time curve (AUCs) were 23.0 and 19.3 μg.h.ml(-1), respectively. After administration of ampicillintrihydrate to fed horses the mean AUC was 0.7 μg.h.ml(-1). The peak plasma concentrations were 4.8, 6.7, and 0.1 μg/ml, after administration of pivampicillin to starved and fed horses and of ampicillin trihydrate to fed horses, respectively. There was no statistically significant difference in peak plasma concentration or AUC between pivampicillin administered to starved or fed horses. It is concluded that pivampicillin administered as an oral paste at a dose of 19.9 mg/kg gives satisfactory plasma concentrations in both starved and fed horses, whereas ampicillin trihydrate produces negligible plasma concentrations. Pivampicillin binds to feedstuffs at the pH found in the horses stomach and small intestine. After incubation for 6h at pH 6, approximately 15% remains in solution, and after incubation for 3h at pH 1.9, approximately 40% remains in solution. Ampicillin, which binds to feedstuffs to a lesser extent, has a lower bioavailability than pivampicillin. Therefore, binding to feedstuffs does not seem to be a critical factor in the absorption of aminopenicillins.

Treatment and long-term follow-up of distichiasis, with special reference to the Friesian horse: a case series

REASONS FOR PERFORMING STUDY Distichiasis is very uncommon in horses and treatment options and outcome remain unknown. OBJECTIVES To describe treatment and long-term follow-up of distichiasis in the horse. STUDY DESIGN Retrospective clinical study. METHODS Case records of horses admitted for diagnosis and treatment of uni- or bilateral distichiasis between 2003 and 2012 were reviewed. Long-term (>6 months after last treatment) follow-up was by telephone conversation with the owner or referring veterinarian. Data were analysed using a Chi-squared test. RESULTS Eighteen cases were identified, of which 17 were Friesians. All horses had signs of corneal irritation or ulceration concurrent with distichiasis. In total, 29 eyes were affected with distichiasis of which 23 had clinical signs. All corneas were stained with fluorescein and 13 had fluorescein positive defects (45%). The lower eyelid was affected more often. Two different electrocautery devices were used for treatment. The complications were slight scarring of the eyelids (100%) and clinical recurrence (54%). Successful resolution of the clinical signs after one treatment occurred in 46% of the horses and in 77% of the horses satisfactory long-term results were found after a mean of 2 treatments (range: 1- 6 treatments). There was significant correlation between number of hairs and recurrence (P<0.002). CONCLUSIONS There is a breed predisposition of distichiasis in the Friesian horse. In Friesian horses that present with uni- or bilateral corneal irritation or corneal ulceration, careful examination of the eyelid margins should be performed to diagnose distichiasis. Electrocautery is a valid and successful therapeutic modality which is minimally invasive, inexpensive, has a low complication rate and is easy to perform in the standing sedated horse. The recurrence rate is low in horses with less than 5 distichiae.

Oral bioavailability of pivampicillin in foals at different ages.

The plasma disposition of ampicillin after intravenous administration at a dose rate of 15 mg/kg was studied in six healthy, 1-month-old foals. The oral bioavailability of pivampicillin was determined in the same foals at four ages, ranging from 11 days to 4 months. Pivampicillin was administered orally at a dose rate of 19.9 mg/kg, which is equivalent on a molecular basis to 15 mg/kg ampicillin. Ampicillin concentrations in plasma were determined up to 12 hours after administration. After intravenous administration, the mean distribution and elimination half-lives of ampicillin were 0.121 and 0.624 h, respectively. The volume of distribution (Vss) appeared to be 0.334 l/kg. Orally administered pivampicillin was rapidly absorbed in all age groups, producing mean peak plasma concentrations of 3.83 to 5.69 micrograms/ml 1 h after administration. The mean bioavailability of pivampicillin in the different age groups ranged from 39.4 to 52.9%. There was no statistically significant difference in peak plasma concentration or bioavailability between the age groups. It is concluded that pivampicillin at a dose rate of 19.9 mg/kg orally gives satisfactory plasma concentrations in foals of all ages.