Cerebellar Hypoplasia in Two Juvenile African Grey Parrots (Psittacus erithacus).

Two sibling 12-week-old DNA-sexed female African grey parrots (Psittacus erithacus) were presented for progressive whole-body tremors, proprioceptive deficits, and an inability to stand unassisted. A third bird in the clutch (DNA-sexed as a male) exhibited no clinical signs. Physical examination of the affected birds revealed ataxia, inability to stand without assistance, and a reliance on their beaks to assist with their mobility. Hematologic and biochemical analyses were normal, as were radiographic images of both birds. Cerebellar disease of unknown origin was diagnosed, and the birds were euthanized. Postmortem examinations of the brains of both parrots revealed marked reduction in cerebellar size and poor folia formation. Microscopic review of the cerebellums demonstrated decreased density of the granular layer and thinning of the molecular layer with poorly organized and differentiated Purkinje fibers, consistent with a diagnosis of cerebellar hypoplasia. There are limited clinical reports and experimental studies examining cerebellar disease in birds. Conditions described have included cerebellar hypoplasia, cerebellar abiotrophy, and cerebellar dysplasia. Although these terms are used interchangeably due to similar clinical signs, histopathology is needed to differentiate between the different disease conditions. This case describes cerebellar hypoplasia that suggested a developmental etiology in 2 African grey parrots.

Complex central nervous system malformations in a Dutch Warmblood foal.

A neonatal Dutch Warmblood colt was evaluated for inability to stand, incoordination and intention tremor. Despite partial improvement in clinical signs during the first 4 days of hospitalization, neurological deficits remained. Magnetic resonance imaging identified a unilateral infratentorial arachnoid cyst-like lesion with ipsilateral compression and displacement of the cerebellar hemisphere, absent corpus collosum, polymicrogyria, suspect leukoencephalopathy, and noncompressive occipitoatlantal malformation. Improvement in clinical signs during the first 6 months of life suggests that horses can survive with complex congenital neurological malformations, but prognosis for athletic performance is poor. The accessibility of magnetic resonance imaging should improve the diagnostic accuracy of central nervous system disorders in neonatal foals in which congenital malformations are suspected. Euthanasia often is elected in foals with suspected congenital central nervous system disorders because of poor prognosis for athletic performance, limiting understanding of clinical progression in these cases.

A Deletion in GDF7 is Associated with a Heritable Forebrain Commissural Malformation Concurrent with Ventriculomegaly and Interhemispheric Cysts in Cats.

An inherited neurologic syndrome in a family of mixed-breed Oriental cats has been characterized as forebrain commissural malformation, concurrent with ventriculomegaly and interhemispheric cysts. However, the genetic basis for this autosomal recessive syndrome in cats is unknown. Forty-three cats were genotyped on the Illumina Infinium Feline 63K iSelect DNA Array and used for analyses. Genome-wide association studies, including a sib-transmission disequilibrium test and a case-control association analysis, and homozygosity mapping, identified a critical region on cat chromosome A3. Short-read whole genome sequencing was completed for a cat trio segregating with the syndrome. A homozygous 7 bp deletion in growth differentiation factor 7 (GDF7) (c.221_227delGCCGCGC [p.Arg74Profs]) was identified in affected cats, by comparison to the 99 Lives Cat variant dataset, validated using Sanger sequencing and genotyped by fragment analyses. This variant was not identified in 192 unaffected cats in the 99 Lives dataset. The variant segregated concordantly in an extended pedigree. In mice, GDF7 mRNA is expressed within the roof plate when commissural axons initiate ventrally-directed growth. This finding emphasized the importance of GDF7 in the neurodevelopmental process in the mammalian brain. A genetic test can be developed for use by cat breeders to eradicate this variant.

Cerebellar hypoplasia and dysplasia in a juvenile raccoon with parvoviral infection.

A juvenile raccoon (Procyon lotor) was submitted dead to the Minnesota Veterinary Diagnostic Laboratory for rabies testing without history. The animal had marked hypoplasia of the cerebellum. Histology demonstrated that most folia lacked granule cells and had randomly misplaced Purkinje cells. Immunohistochemistry revealed the presence of parvoviral antigen in a few neurons and cell processes. PCR targeting feline and canine parvovirus yielded a positive signal. Sequencing analyses from a fragment of the nonstructural protein 1 (NS1) gene and a portion of the viral capsid protein 2 (VP2) gene confirmed the presence of DNA of a recent canine parvovirus variant (CPV-2a-like virus) in the cerebellum. Our study provides evidence that (canine) parvovirus may be associated with cerebellar hypoplasia and dysplasia in raccoons, similar to the disease that occurs naturally and has been reproduced experimentally by feline parvoviral infection of pregnant cats, with subsequent intrauterine or neonatal infections of the offspring.

Neuropathogenicity of newly isolated avian leukosis viruses from chickens with osteopetrosis and mesenchymal neoplasms.

ABSTRACT The prototype fowl glioma-inducing virus (FGVp) causes fowl glioma and cerebellar hypoplasia in chickens. In this study, we investigated whether a strain of avian leukosis virus (ALV), associated with avian osteopetrosis and mesenchymal neoplasms, is able to induce fowl glioma. We encountered avian osteopetrosis and mesenchymal neoplasms, including myxosarcoma and rhabdomyosarcoma, in Japanese native chickens used for both egg-laying and meat production. These birds were also affected by non-suppurative encephalitis and glioma in their brains. Four ALV strains (GifN_001, GifN_002, GifN_004, GifN_005) were isolated, and a phylogenic analysis of envSU showed that these isolates were classified into different clusters from FGVp and the variants previously reported. Whereas the envSU shared a high identity (94.7%) with that of Rous sarcoma virus (strain Schmidt-Ruppin B) (RSV-SRB), the identity between envTM of GifN_001 and that of FGVp was high (94.5%), indicating that GifN_strains may emerge by recombination between FGVp and other exogenous ALVs. Specific-pathogen-free chickens inoculated in ovo with GifN_001 revealed fowl glioma and cerebellar hypoplasia. These results suggest that the newly isolated strains have acquired neuropathogenicity to chickens.

Ocular Neural Heterotopia in a Moroccan Uromastyx (Uromastyx acanthinurus nigriventris).

A juvenile female Moroccan uromastyx (Uromastyx acanthinurus nigriventris) that died unexpectedly was necropsied. Necropsy examination revealed minimal intracoelomic fat, small numbers of intestinal nematodes and intraocular masses within the vitreous chamber of both eyes. One of the intraocular masses was focally contiguous with the optic nerve and composed of neuroparenchyma with rare glial cells, consistent with a diagnosis of neural heterotopia. This condition is considered a neuroectodermal malformation, readily recognized in human medicine but rarely reported in animals. To the authors' knowledge, this is the first case of intraocular neural heterotopia reported in a reptile.

Spongy Myelinopathy in Newborn Beef Calves Associated with Consumption of Corn Infected with Stenocarpella maydis.

Stillbirth and perinatal mortality with neurological signs and lesions were diagnosed in two calves following ingestion by their dams of corn infected with Stenocarpella maydis during the third trimester of gestation. Grossly, the brain and spinal cord were unremarkable. Microscopically, diffuse severe status spongiosis of the white matter was detected in the cerebral hemispheres, brainstem, spinal cord and cerebellum. To the best of our knowledge this is the first pathological description of congenital disease in calves associated with the consumption of S. maydis-infected corn; the findings resemble those reported for the naturally occurring and experimentally induced disease in lambs.

Congenital tremor in piglets: Is bovine viral diarrhea virus an etiological cause?

Congenital tremor in pigs involves several etiologies, including pestivirus, which may cause neurological injuries in different animal species. To evaluate whether bovine viral diarrhea virus (BVDV), an important pestivirus, is one of the etiological agents of congenital tremor in swine, gilts and the fetuses were challenged at 45 days of gestation with BVDV-2. Four pregnant gilts were inoculated oronasally, four gilts underwent fetal intrauterine inoculation, and two gilts constituted the control group. Antibody titers were determined by virus neutralization (VN), and viral RNA was detected by RT-PCR. Blood samples were collected from all gilts and piglets born to obtain whole blood and serum for analysis. One third of the neonates were euthanized at three days old, and samples of the encephalon, brain stem and spinal cord were collected for anatomopathological evaluation and viral RNA detection. The piglets that remained alive were clinically evaluated every day, and blood sampling was performed regularly for 35 days. The piglets from gilts in both inoculation treatment groups showed no clinical neurological signs and were born with no viral RNA in their blood and organs. Piglets born from oronasally inoculated gilts did not present antibodies against BVDV-2 at birth, although they were acquired by passive maternal transfer. In contrast, intrauterine-inoculated piglets were born with high antibody titers (80 to 640) against the agent, which remained high until the end of the experimental period. Microscopically, no noticeable changes were observed. Macroscopically, 29.5% of the total piglets euthanized, from both inoculation groups, were born with a low cerebellar:brain ratio. Nevertheless, some piglets had a high cerebellar:brain ratio, indicating the need for standardizing this value. Thus, it was concluded that BVDV is not an etiological agent for congenital swine tremor.

Diagnostic yield and accuracy of postmortem cytological sampling from the brain surface of animals with neurological abnormalities.

Clarification of central nervous system (CNS) disorders frequently requires pathological investigation via brain biopsy or postmortem examination. The use of cytology is usually restricted to diagnosis of mass lesions and septic meningitis. The value of brain cytology at postmortem examination has not been explored sufficiently. This study aimed to clarify the diagnostic value of meningeal imprint cytology at postmortem brain examination. Samples were taken from cerebrum and cerebellum and stained with the modified Wright stain and with haematoxylin-eosin. The slides were evaluated and findings were compared to brain histopathology with respect to resemblance, discrepancy and diagnostic validity. The study included 169 cases involving multiple animal species. Histopathology identified inflammatory disorders in 60/135 (44.4%) cases, neoplasia in 19/135 (14.1%) and non-infiltrative diseases in 56/135 (41.5%). Cytology revealed pathological changes in 79/135 (58.5%) of these cases. The histopathological diagnosis was reproduced in 57/135 (42.2%) cases, 43/57 (75.4%) of which were inflammatory. Non-diagnostic cases included 16/135 (11.9%) with sub-diagnostic cytological features and 3/135 (2.2%) with unclear phenomena. In 55/135 (40.7%) of brains with histological lesions, cytology proved inferior, providing negative results, including 40/55 (72.7%) cases with non-infiltrative diseases, 12/55 (21.8%) with inflammation and 3/55 (5.5%) with neoplasia. Conversely, 3/34 (8.8%) of controls showed cytological abnormalities. Cytological sampling from CNS adds to the sensitivity of neuropathological investigations, even if restricted to non-invasive surface imprints. The diagnostic accuracy exceeds 40%, with infiltrative diseases being five times more likely to be detected than non-infiltrative diseases.

Unilateral cerebellar hypoplasia and mesencephalic malformation in a Hanoverian foal.

Neurological cases, especially in foals, are rare in the daily practical work. The most common causes are traumata and infectious diseases of the central nervous system (CNS). This case report provides further insights into the wide spectrum of possible neuropathological lesions by detailing a complex malformation with unilateral neurological signs that occurred later post natum. Thus, clinicians should also be aware of malformations in case of respective neurological patients. A Hanoverian foal was presented with progressive ataxia. General and blood examination revealed no further alterations. By neurologic examination, a unilateral hypermetria was diagnosed and a cysternography of the head was performed. A cerebellar malformation was assumed and the foal was euthanized due to poor prognosis. At necropsy, a unilateral absence of a cerebellar hemisphere and vermis accompanied by contralateral malformation of the mesencephalon was diagnosed. The missing areas of the right cerebellar hemisphere were replaced by a cystic formation. The left part of the mesencephalic lamina quadrigemina was reduced in size and the corpus callosum was hypoplastic. Additional microscopical findings were most obvious near the cyst formation and included angiofibrosis in remaining cerebellar and mesencephalic parenchyma and leptomeninges, heterotopia of cerebellar neurons, sclerosis in cerebellar cortex, focal proliferation of meningeal cells and mild mononuclear perivascular infiltrates. Occassional irregular neuronal arrangement in the mesencephalon was also present. Infectious agents such as Borna disease virus, rabies virus, and equine herpesvirus were not detected. Therefore, the complex malformation in this foal might have been caused by a destructive, possibly ischemic event, or could represent a sequel of a primary retrocerebellar cyst with accompanying compression of adjacent parenchyma.

Identification of feline panleukopenia virus proteins expressed in Purkinje cell nuclei of cats with cerebellar hypoplasia.

Parvoviruses depend on initiation of host cell division for their replication. Undefined parvoviral proteins have been detected in Purkinje cells of the cerebellum after experimental feline panleukopenia virus (FPV) infection of neonatal kittens and in naturally occurring cases of feline cerebellar hypoplasia. In this study, a parvoviral protein in the nucleus of Purkinje cells of kittens with cerebellar hypoplasia was shown by immunoprecipitation to be the FPV viral capsid protein VP2. In PCR-confirmed, FPV-associated feline cerebellar hypoplasia, expression of the FPV VP2 protein was demonstrated by immunohistochemistry in Purkinje cell nuclei in 4/10 cases and expression of the FPV non-structural protein NS1 was demonstrated in Purkinje cell nuclei in 5/10 cases. Increased nuclear ERK1 expression was observed in several Purkinje cells in 1/10 kittens. No expression of the G1 and S mitotic phase marker proliferating cell nuclear antigen (PCNA) was evident in Purkinje cell nuclei. These results support the hypothesis that FPV is able to proceed far into its replication cycle in post-mitotic Purkinje cells.

Purkinje cell heterotopy with cerebellar hypoplasia in two free-living American kestrels (Falco sparverius).

Two wild fledgling kestrels exhibited lack of motor coordination, postural reaction deficits, and abnormal propioception. At necropsy, the cerebellum and brainstem were markedly underdeveloped. Microscopically, there was Purkinje cells heterotopy, abnormal circuitry, and hypoplasia with defective foliation. Heterotopic neurons were identified as immature Purkinje cells by their size, location, immunoreactivity for calbindin D-28 K, and ultrastructural features. The authors suggest that this cerebellar abnormality was likely due to a disruption of molecular mechanisms that dictate Purkinje cell migration, placement, and maturation in early embryonic development. The etiology of this condition remains undetermined. Congenital central nervous system disorders have rarely been reported in birds.

Recurrent outbreaks of myelodysplasia in newborn calves.

The present study records recurrent outbreaks of myelodysplasia of unknown origin occurring in a specific geographical location in the north of Spain, and involving up to 30% of the calves born in affected herds. The affected calves were of different breeds and displayed non-progressive signs of spinal cord dysfunction. The disease has occurred annually in February-March over a period of at least 15 years. Only calves born to cattle grazed on mountainside pastures and under high grazing pressure were affected. Seven calves were subjected to necropsy examination. Myelodysplasia was not associated with vertebral defects or arthrogryposis and involved the entire length of the spinal cord. Microscopically, there was abnormal distribution of the grey matter, aberrations of the central canal and failure of formation of the ventral median fissure. Infectious, nutritional and physical disorders were ruled out as possible aetiologies. A critical period of embryonic susceptibility to the causal agent was identified. This was during the time of secondary neurulation when cows in the early stages of gestation were grazed on mountainside pastures. Consequently, the presence of neuroteratogenic plants in these pastures is proposed as a likely cause. Two plants, Carex brevicollis and Erythronium dens-canis, which contain alkaloids, were identified on the mountainsides where affected cattle were grazed and not in other pastures, and are proposed as the possible aetiology of the disease.

Magnetic resonance imaging of intracranial malformations in dogs and cats.

Intracranial malformations may occur because of an inherent developmental defect or secondary to in utero injury to the brain with subsequent hypoplasia and atrophy. They can cause neurologic deficits in growing animals, although some anomalies may not produce clinical signs until adulthood. Malformations of the brain include hydrocephalus, hydranencephaly/porencephaly, holoprosencephaly, corpus callosum agenesis/dysgenesis, lissencephaly, polymicrogyria, meningoencephalocele, intracranial cysts, cerebellar malformations, and hamartomas. These conditions are defined and reviewed with an emphasis on their features in magnetic resonance images.

Dystocia and fetotomy associated with cerebral aplasia in a greater one-horned rhinoceros (Rhinoceros unicornis).

The captive greater one-horned rhinoceros population consists of 176 animals. Since 1971, a total of 226 calves were born into this captive population. However, 24% of the offspring born were either stillborn or did not survive the first 3 months. The causes for this high rate of stillbirth and neonate mortality have not yet been documented. Here, we report on the veterinary management of a dystocia and foetotomy resulting from a malpositioned greater one-horned rhinoceros foetus. The dead foetus presented with a forelimb flexed at the shoulder joint, with all other joints extended. The foetus was dissected into five parts and extracted during two anaesthesias on two consecutive days. The dam recovered fully and came into oestrous 31 days after surgery. Post-mortem and CT examination of the malformed foetal head revealed cranioschisis with cerebral aplasia and cerebellar hypoplasia. The cerebral aplasia presented here and in other recent cases suggests that neural tube defects and cranial malformations may be associated with more captive rhinoceros stillbirths than previously considered. Epidemiologic studies of these phenomena and possible nutritional deficiencies or hereditary defects are warranted.

Effects of heavy oil in the developing spotted halibut, Verasper variegatus.

It is well known that heavy oil (HO) on the sea surface causes serious problems in the aquatic environment. In particular, some species of teleosts which develop on the sea surface are thought to be affected by the HO which flows out from tankers or coastal industry. However, the toxicological effects of HO are not fully understood. We performed exposure experiments using the Pleuronectiformean fish, spotted halibut (Verasper variegatus), which is an important fishery resource in Japan. In course of the development, HO-exposed embryos showed remarkable delay in developmental processes including somite formation. We further observed abnormal development of the head morphology. Notably, treated embryos had relatively small eyes and craniofacial structures. These findings strongly suggest that HO seriously affects the cell proliferation and differentiation of the embryo. In addition, HO-exposed embryos showed abnormal neuronal development. We also performed the exposure in the larval stage. Treatment of post-hatching larvae with HO resulted in significantly greater mortality compared with controls. Through these observations, we finally conclude that HO is strongly toxic to halibut in their early life stages.

The fungicide benomyl inhibits differentiation of neural tissue in the Xenopus embryo and animal cap explants.

The toxic effect of benomyl on the embryogenesis of Xenopus laevis was investigated, and the tissues most affected by benomyl were identified. The toxicity of benomyl at various concentrations (5-20 microM) was tested with the Xenopus frog embryo teratogenesis assay (FETAX), used with slight modification. All test embryos subjected to 20 microM of benomyl died, and exposure to 10 and 15 microM benomyl produced growth inhibition and 11 types of severe external malformations. Histological examination of the test embryos showed dysplasia of the brain, eyes, intestine, otic vesicle, and muscle and swelling of the pronephric ducts and integuments. Among the tissues and organs affected, malformation of neural tissue was the most severe. The presumptive ectoderm isolated from st. 9 embryo was cultured in 10 ng/mL of activin A to induce neural tissue and mesoderm. When it was cultured with 10 ng/mL of activin A in the presence of 1 and 10 microM of benomyl, neural tissue induction was inhibited more severely than that of any other tissue. The gene expression of cultivated explants was investigated by reverse transcription-polymerase chain reaction (RT-PCR) assay in order to study the inhibition of neural tissue by benomyl. The results showed that with increasing benomyl concentration, the expression of the neural-specific marker NCAM (neural cell adhesion molecule), was more strongly inhibited than the muscle-specific marker muscle actin. Electron micrographs of test explants showed many residual yolk platelets and mitochondrial degeneration. In the present investigation the most severe toxic effects of benomyl were seen in the nerve tissues of the Xenopus embryo. This inhibition of neural development may have been caused by the inhibition of the assembly of neural microtubules and by the effect of benomyl on neuronal proliferation and migration.