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Cutaneous round cell neoplasms (RCNs) are among the most common skin tumors of dogs. Although a diagnosis can be made in most cases following the examination of H&E-stained routine samples, less-differentiated neoplasms can exhibit overlapping morphologic features that may be challenging to the pathologist, and require immunohistochemistry or molecular testing to reach a final diagnosis. Many patients with cutaneous RCNs are initially seen by a general practitioner and are not referred to a veterinary teaching hospital until a diagnosis has been made. For this reason, anatomic pathology residents at some academic or other training institutions may not be exposed frequently to RCNs during the surgical biopsy service as part of their residency training. In an attempt to fill that gap, here we review the key routine histologic features of canine cutaneous RCNs.

Cutaneous and mucocutaneous plasmacytoma (PCT) is a common neoplasm of dogs. Tumors can be single or multiple and occur predominantly in the oral cavity, lip, ears, digits, and trunk. Although these tumors typically offer no diagnostic challenge for the pathologist, subsets of PCTs with atypical morphologic configurations may make differentiation from other neoplasms difficult. We describe 6 cases of canine cutaneous and mucocutaneous PCT with pseudoglandular arrangement of neoplastic cells. The mean age of affected dogs was 11.3 y, and multiple breeds and sites were affected. Histologically, neoplastic cells were arranged in sheets, packets, and pseudoglandular structures containing central accumulations of blood or eosinophilic material admixed with neoplastic cells and hemosiderin-laden macrophages. Given the presence of pseudoglandular structures resembling neoplastic acini, epithelial neoplasia was occasionally included in the differential diagnosis. Neoplastic cells were strongly immunopositive for multiple myeloma oncogene 1 ( MUM-1) and immunonegative for pancytokeratin AE1/AE3. Canine cutaneous and mucocutaneous PCTs with pseudoglandular morphology may resemble epithelial neoplasia and raise questions about tumor histogenesis.

Aspergillosis is one of the most frequent mycosis affecting avian species. Here is reported an outbreak of aspergillosis affecting 60-day-old white Pekin mallards (Anas platyrhynchos). About 10% of animals in a lot of 200 mallards from a commercial husbandry presented respiratory disorders and skin lesions at slaughter. Three out of 13 animals sent to diagnosis showed, simultaneously, airsacculitis, lung and liver presenting white nodules with variable diameters and elevated, yellowish brown, crusted, multifocal skin lesions located at the base of the feather follicles in the breast. Histopathological examination of lung and liver samples revealed nodules of different sizes with small areas of necrosis surrounded by intense granulomatous inflammation and the presence of fungal hyphae. The skin samples showed dermatitis surrounding a severe necrotizing folliculitis, associated with fungal hyphae. Mycological evaluation of tissues allowed the isolation of Aspergillus fumigatus from the skin samples and Aspergillus flavus from lungs and liver samples. The application of quicklime (CaO) in the litter as part of the disinfection procedures could have contributed to the development of skin lesion in the mallards, predisposing the fungal installation in the damaged site. The occurrence of cutaneous lesions associated with A. fumigatus is a rare manifestation of aspergillosis in birds, and this appears to be the first case reported in white Pekin mallards.

A 6 yr old female Labrador retriever was evaluated for an acute onset of difficulty walking and a head tilt. Initial physical examination revealed bilateral retinal detachment, a left-sided head tilt, positional rotary nystagmus, and lumbar hyperpathia. Pertinent preliminary diagnostic findings included systemic hypertension, bony lysis and adjacent sclerosis of the vertebral endplates of the first and second lumbar vertebrae, and positive urine and blood cultures for a yeast identified as Candida spp. Concerned about disseminated candidiasis after subsequent subretinal aspirates confirmed the presence of a yeast-like organism, therapy with voriconazole was initiated. Because of progressive clinical deterioration and the poor prognosis for recovery, the dog was eventually euthanized. Postmortem histological examination of tissues, including the affected vertebral endplates, revealed numerous intralesional algae compatible with Prototheca spp. To the authors' knowledge, this report is the first to document a case of protothecal diskospondylitis with possible concurrent candidiasis in a dog. Although typically associated with signs referable to the gastrointestinal tract, this report underscores the importance of not excluding protothecosis as a differential diagnosis when such signs are absent. Lastly, the use of voriconazole appears ineffective for reversing the clinical course of late-stage disseminated protothecosis.

A spontaneous outbreak of neurological disease in swine caused by the ingestion of Aeschynomene indica seeds and reproduction of the disease in the same specie are reported. In the natural outbreak the morbidity, mortality and lethality rates were respectively 25%-40%, 8.5%-20%, and 25%-66%. Clinical signs were variable degrees of incoordination of gait, falls, sternal recumbency with wide base stance of the hind limbs, lateral recumbency and death. For experimental reproduction of the intoxication, 5 (A-E) pigs were fed a ration containing 10% (PigA), 15% (Pig B) and 20% (Pigs C-E) of A. indica seeds. Pigs A and B were euthanatized and Pigs C-E died of acute disease respectively 16, 21 and 24 hours after the start of the experiment. Clinical signs were similar to those observed in pigs from the spontaneous outbreak. Histopathological findings in the brain of pigs fed rations with 20% A. indica seeds (C-E) were congestion, edema and hemorrhage and swollen capillary endothelia in nuclei and in the telencephalic cortex. Pigs fed 10% and 15% A. indica had histopathological changes in the brain of discrete focal symmetrical areas of malacia. These findings indicate that one or more toxic principles in A. indica seeds are responsible for this neurological condition and that clinical outcome and pathological changes are dose-dependent. The symmetrical malacic foci from the ingestion of A. indica seeds in pigs affected vestibular and cerebellar nuclei, putamen, and the mesencephalic substantia nigra, oculomotor, and red nucleus; thus, focal symmetrical encephalomalacia is suggested as a better name for the disease.

Seventeen pregnant ewes were orally fed variable amounts of either green or dried leaves of Ateleia glazioviana in 1 through 24 daily doses. All 17 ewes manifested some form of reproductive failure. Nine (52.9%) aborted their fetuses at 4 through 36 d after starting being fed the leaves of the plant; 1 had a stillbirth and in another 1 intrauterine fetal death was diagnosed. The other 6 ewes delivered 8 weak lambs, 7 of which died from few min to 48 h after birth. Three ewes had neurologic disturbances and loss of weight. Thirteen ewes were euthanatized 1-48 h after lambing or pregnancy loss; 2 of them had gross and histopathological changes related to the A glazioviana. Gross and histopathological changes observed in 7 lambs and in a stillborn, and histopathological changes found in 4 aborted fetuses from A glazioviana-fed ewes, were similar to those found in spontaneous poisoning by A glazioviana in adult cattle. It is concluded that A glazioviana has a powerful abortifacient activity whether ingested green or dried. The abortions caused by A glazioviana were not due to placental damage, but rather to transplacental induced fetal lesions consisting of toxic cardiomyopathy and spongy degeneration of the white matter of the brain. Fetuses succumbing to these lesions were expelled from the uterus; those not lethally affected are born weak with meager chances to survive.

Epidemiological, clinical and pathological aspects of an unreported plant poisoning are described in sheep from southern Brazil. The disease occurred during the summer of 2003/2004 in 173 crossbred sheep with morbidity, mortality and lethality rates respectively of 31.8%, 8.1%, and 25.5%. Affected sheep were reluctant to move; when forced to walk they had stiff uncoordinated gaits, dragged their toes and bumped into objects in their path. When standing they assumed a wide base position with the legs widely spread apart. Increased respiratory rates, laborious breathing and cyanosis were marked in affected sheep that died. The experimental feeding of 2 sheep with the fruits of Eythroxylum argentinum reproduced the clinical disease. Except for consistent findings of distended bladder and the presence of E. argentinum undigested seeds in the abomasum and rumen in 4 necropsied sheep, no significant necropsy and histopathological findings were found. It was concluded that the ingestion of fruits of E. argentinum was the cause of this disease in sheep.

Rhodococcus equi is an important pathogen of foals that causes severe pneumonia. To date, there is no licensed vaccine effective against R. equi pneumonia of foals. The objectives of our study were to develop an electron beam (eBeam) inactivated vaccine against R. equi and evaluate its immunogenicity. A dose of eBeam irradiation that inactivated replication of R. equi while maintaining outer cell wall integrity was identified. Enteral administration of eBeam inactivated R. equi increased interferon-γ production by peripheral blood mononuclear cells in response to stimulation with virulent R. equi and generated naso-pharyngeal R. equi-specific IgA in newborn foals. Our results indicate that eBeam irradiated R. equi administered enterally produce cell-mediated and upper respiratory mucosal immune responses, in the face of passively transferred maternal antibodies, similar to those produced in response to enteral administration of live organisms (a strategy which previously has been documented to protect foals against intrabronchial infection with virulent R. equi). No evidence of adverse effects was noted among vaccinated foals.