Cutaneous malignant melanoma in a Haller's round ray Urobatis halleri.

Multiple black raised nodular masses were noted on the dorsal surface of an adult male Haller's round ray Urobatis halleri. Biopsy of 2 masses was performed, and histopathology revealed proliferative sheets of melanocytes exhibiting mild anisocytosis and anisokaryosis, supporting a diagnosis of malignant melanoma. Approximately 2 mo following the biopsy procedure, the round ray became acutely anorexic and was found dead in its enclosure. A full necropsy was performed, and tissues were submitted for histopathology. The black raised nodular masses again exhibited histologic features of a melanoma. In addition to the nodular masses present, multiple flat areas of increased pigmentation were also present throughout the course of the case and were not suggestive of neoplasia histologically. The transformation of benign to malignant neoplasia has been well described in other species and may have played a role in the development of multiple tumors in this case.

Ectopic Intrathoracic Hepatic Tissue and Accessory Lung Lobe Aplasia in a Dog.

A 6 yr old male Yorkshire terrier was presented for an ~6 yr history of progressive cough and dyspnea. Thoracic radiographs revealed a 6 cm diameter mass within the right caudal thorax. Thoracic ultrasound identified an intrathoracic mass ultrasonographically consistent with liver tissue and a chronic diaphragmatic hernia was suspected. Exploratory laparotomy was performed, but no evidence of a diaphragmatic hernia was identified. Thoracic exploration identified abnormal lung parenchyma. The accessory lung lobe was removed using a stapling devise near its base. The consolidated mass had the gross appearance of liver and was histologically identified as ectopic hepatic tissue. Ectopic hepatic tissue, unlike ectopic splenic and pancreatic tissue, is rare and generally has a subdiaphragmatic distribution. This solitary case report demonstrates that ectopic intrathoracic hepatic tissue should be considered a differential diagnosis for a caudal mediastinal mass.

Strain impact on equine herpesvirus type 1 (EHV-1) abortion models: viral loads in fetal and placental tissues and foals.

Equine herpesvirus-1 (EHV-1) continues to cause both sporadic and epidemic abortions despite extensive vaccination. Lack of progress in the development of protective vaccines may be hindered by the lack of equine abortion models that employ contemporary EHV-1 strains. The objective of our experiments was to compare a contemporary EHV-1 strain with a previously described challenge strain, and to quantify EHV-1 loads in various maternal and fetal tissues. Infection experiments were performed in two groups of 7 pregnant pony mares at 270-290 days of gestation with a contemporary EHV-1 strain (University of Findlay 2003 isolate - OH03) or an EHV-1 strain isolated over 30 years ago, and previously described in abortion models (Ab4). All mares in both groups exhibited nasal viral shedding and viremia. Infection with OH03 resulted in 1/7 abortion and infection with Ab4 resulted in 5/7 abortions. In the OH03 challenge, placentas of foals delivered at term showed little detectable virus, while the aborted fetus expressed high levels of virus infection in the spleen and liver, lower levels in the lung and thymus, and lowest levels in the chorioallantois. After Ab4 challenge, high viral loads were detected in fetal and placental tissues in abortions. In the two normal deliveries, the chorioallantois contained virus levels comparable with the chorioallantois of aborted foals and both foals shed EHV-1 starting on day 4 of life, but were clinically healthy. Our results demonstrate the continued importance of strain selection for abortion models, and this study is the first report of viral load quantification using contemporary methods. Extremely high EHV-1 loads in decidua from abortions illustrate the infection risk posed to other horses.

Association of histologic tumor characteristics and size of surgical margins with clinical outcome after surgical removal of cutaneous mast cell tumors in dogs.

OBJECTIVE: To evaluate the relationship between width and depth of surgical margins, amount of edema within and around the tumor, and degree of demarcation between the tumor and surrounding tissues with the clinical outcome following surgical removal of cutaneous mast cell tumors (cMCTs) in dogs. DESIGN: Retrospective cohort study. ANIMALS: 100 dogs with 115 resectable cMCTs. PROCEDURES: Information about the dogs' clinical outcomes following cMCT removal was obtained from primary care veterinarians. Histologic sections of excised tumors were assessed retrospectively for tumor grade and measurement of the narrowest lateral and deep margins of nonneoplastic tissue excised with the tumors; edema within the tumor and surrounding tissues was assessed as minimal, moderate, or severe. Tumors were classified as poorly, moderately, or well demarcated on the basis of the degree of mast cell infiltration into the adjoining connective tissue. RESULTS: Following tumor excision (with no additional postsurgery treatment), 96 dogs had no local recurrence or metastatic disease for 27 to 31 months; 4 metastatic disease-related deaths (dogs with grade II or III tumors) occurred within 3 to 9 months. Histologically, mean lateral and deep surgical margins around the tumors were 8.9 and 5.3 mm, respectively. No recurrence of tumor or metastatic disease developed following excision with lateral margins ≥ 10 mm and deep margins ≥ 4 mm. Edema and degree of demarcation were not correlated with outcome. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that most grade I and II cMCTs in dogs can be successfully treated by complete surgical removal with margins smaller than those currently recommended.

Photodermatitis and photokeratoconjunctivitis in a ball python (Python regius) and a blue-tongue skink (Tiliqua spp.).

A male ball python (Python regius) and a female blue tongue skink (Tiliqua spp.) of unknown age were evaluated for anorexia, lethargy, excessive shedding, corneal opacity (python), and weight loss (skink) of approximately three weeks' duration. These animals represented the worst affected animals from a private herpetarium where many animals exhibited similar signs. At necropsy, the python had bilateral corneal opacity and scattered moderate dysecdysis. The skink had mild dysecdysis, poor body condition, moderate intestinal nematodiasis, and mild liver atrophy. Microscopic evaluation revealed epidermal erosion and ulceration, with severe epidermal basal cell degeneration and necrosis, and superficial dermatitis (python and skink). Severe bilateral ulcerative keratoconjunctivitis with bacterial colonization was noted in the ball python. Microscopic findings within the skin and eyes were suggestive of ultraviolet (UV) radiation damage or of photodermatitis and photokeratoconjunctivitis. Removal of the recently installed new lamps from the terrariums of the surviving reptiles resulted in resolution of clinical signs. Evaluation of a sample lamp of the type associated with these cases revealed an extremely high UV output, including very-short-wavelength UVB, neither found in natural sunlight nor emitted by several other UVB lamps unassociated with photokeratoconjunctivitis. Exposure to high-intensity and/or inappropriate wavelengths of UV radiation may be associated with significant morbidity, and even mortality, in reptiles. Veterinarians who are presented with reptiles with ocular and/or cutaneous disease of unapparent cause should fully evaluate the specifics of the vivarium light sources. Further research is needed to determine the characteristics of appropriate and of toxic UV light for reptiles kept in captivity.

Fibropapilloma of the glans penis in a horse.

An 18-year-old Arabian stallion was presented for recent onset of stranguria. Physical examination of the distal portion of the glans penis revealed multiple, smooth, glistening, grayish-pink, variably sized, exophytic, nodular masses circumferentially surrounding the external urethral orifice. Partial penile amputation was performed, and the entire specimen was submitted for histological evaluation. Microscopically, the masses consisted of abundant amounts of loosely arranged fibrovascular stroma with low numbers of spindloid to stellate fibrocytes. The overlying epithelium was mildly to moderately hyperplastic with short anastomosing rete ridges (pseudoepitheliomatous hyperplasia). The lesion was diagnosed as fibropapilloma because of features similar to bovine penile fibropapilloma including anatomical location, gross appearance, and histological characteristics. A sarcoid was considered but negated as the lesion lacked the classical streaming and interlacing spindle cell population, "picket-fence" appearance at the epithelial interface, and long, thin, dissecting rete ridges typical of most equine sarcoids. Polymerase chain reaction for the Bovine papillomavirus-1 and Bovine papillomavirus-2 E5 gene and for Equine herpesvirus 1, 3, and 4 was negative on formalin-fixed tissue specimens.

Adaptive significance of avian beak morphology for ectoparasite control.

The beaks of Darwin's finches and other birds are among the best known examples of adaptive evolution. Beak morphology is usually interpreted in relation to its critical role in feeding. However, the beak also plays an important role in preening, which is the first line of defence against harmful ectoparasites such as feather lice, fleas, bugs, flies, ticks and feather mites. Here, we show a feature of the beak specifically adapted for ectoparasite control. Experimental trimming of the tiny (1-2 mm) maxillary overhang of rock pigeons (Columba livia) had no effect on feeding efficiency, yet triggered a dramatic increase in feather lice and the feather damage they cause. The overhang functions by generating a shearing force against the tip of the lower mandible, which moves forward remarkably quickly during preening, at up to 31 timesper second. This force damages parasite exoskeletons, significantly enhancing the efficiency of preening for parasite control. Overhangs longer than the natural mean of 1.6mm break significantly more often than short overhangs. Hence, stabilizing selection will favour overhangs of intermediate length. The adaptive radiation of beak morphology should be re-assessed with both feeding and preening in mind.

Impact of feather molt on ectoparasites: looks can be deceiving.

Animals possess a variety of well-documented defenses against ectoparasites, including morphological, behavioral, and immune responses. Another possible defense that has received relatively little attention is the shedding of the host's exterior. The conventional wisdom is that ectoparasite abundance is reduced when birds molt their feathers, mammals molt their hair, and reptiles shed their skin. We carried out an experimental test of this hypothesis for birds by manipulating molt in feral pigeons (Columba livia) infested with feather lice (Phthiraptera: Ischnocera). We used two standard methods, visual examination and body washing, to quantify the abundance of lice on the birds. The visual data indicated a significant effect of molt on lice. However, the more robust body washing method showed that molt had no effect on louse abundance. Two factors caused visual examination to underestimate the number of lice on molting birds. First, molt replaces worn feathers with new, lush plumage that obscures lice during visual examination. Second, we discovered that lice actively seek refuge inside the sheath that encases developing feathers, where the lice cannot be seen. The apparent reduction in louse abundance caused by these factors may account for the conventional wisdom that feather molt reduces ectoparasite abundance in birds. In light of our experimental results, we argue that it is necessary to reinterpret the conclusions of previous studies that were based on observational data. Additional experiments are needed to test whether shedding of the host's exterior reduces ectoparasites in other birds, mammals, and reptiles, similar to the impact of facultative leaf drop on herbivorous insects on trees.