Hydranencephaly and cerebellar hypoplasia in two kittens attributed to intrauterine parvovirus infection

Clinical and MRI findings of a suspected cortical malformation presented as a giant cerebral pseudomass in a German Shepherd dog

A 5-month-old German Shepherd dog was presented with cluster seizures. MR imaging showed a large irregular pseudomass in the central region of the cranial cavity, compatible with a malformation of cortical development. Despite the extensive changes, the patient was neurologically normal interictally 1 year following diagnosis.

Dandy Walker-like malformation in an adult cat with seizures: clinical description and MRI characteristics

Case summary

A 2-year-old male neutered domestic shorthair cat was referred for investigation of a 10-month history of self-limiting, generalised tonic-clonic seizures. The cat was reported to be normal interictally but had always had a static abnormal gait. General physical examination was unremarkable. Neuroanatomical localisation was compatible with a diffuse cerebellar and diffuse forebrain lesion. Complete blood count, biochemistry, bile acid stimulation test, urinalysis, cisternal cerebrospinal fluid (CSF) analysis, Toxoplasma gondii serology and T gondii polymerase chain reaction in CSF were all unremarkable. MRI revealed an abnormal caudal fossa, absent cerebellar vermis and small cerebellar hemisphere with distension of the fourth ventricle. There were no forebrain abnormalities identified in the MRI or CSF changes that could justify the seizures. Considering the clinical presentation, the cat's neurological examination and MRI features, a presumptive diagnosis of Dandy Walker-like malformation (DWLM) and epilepsy of unknown aetiology was made.

Relevance and novel information

This is the first case report of an adult cat diagnosed with cerebellar malformation resembling DWLM and concomitant seizures, its MRI characteristics and long-term follow-up. The 3-year follow-up consultation revealed static neurological status with 2-4 seizures per year. The cat's quality of life remained good at the time of writing.

2020 AAHA/AAFP Feline Vaccination Guidelines

The guidelines are a consensus report on current recommendations for vaccination of cats of any origin, authored by a Task Force of experts. The guidelines are published simultaneously in the Journal of Feline Medicine and Surgery (volume 22, issue 9, pages 813-830, DOI: 10.1177/1098612X20941784) and the Journal of the American Animal Hospital Association (volume 56, issue 4, pages 249-265, DOI: 10.5326/JAAHA-MS-7123). The guidelines assign approved feline vaccines to core (recommended for all cats) and non-core (recommended based on an individualized risk-benefit assessment) categories. Practitioners can develop individualized vaccination protocols consisting of core vaccines and non-core vaccines based on exposure and susceptibility risk as defined by the patient's life stage, lifestyle, and place of origin and by environmental and epidemiologic factors. An update on feline injection-site sarcomas indicates that occurrence of this sequela remains infrequent and idiosyncratic. Staff education initiatives should enable the veterinary practice team to be proficient in advising clients on proper vaccination practices and compliance. Vaccination is a component of a preventive healthcare plan. The vaccination visit should always include a thorough physical exam and client education dialog that gives the pet owner an understanding of how clinical staff assess disease risk and propose recommendations that help ensure an enduring owner-pet relationship.

2020 AAHA/AAFP Feline Vaccination Guidelines*

The guidelines are a consensus report on current recommendations for vaccination of cats of any origin, authored by a Task Force of experts. The guidelines are published simultaneously in the Journal of Feline Medicine and Surgery (volume 22, issue 9, pages 813–830, DOI: 10.1177/1098612X20941784) and the Journal of the American Animal Hospital Association (volume 56, issue 4, pages 249–265, DOI: 10.5326/JAAHA-MS-7123). The guidelines assign approved feline vaccines to core (recommended for all cats) and non-core (recommended based on an individualized risk-benefit assessment) categories. Practitioners can develop individualized vaccination protocols consisting of core vaccines and non-core vaccines based on exposure and susceptibility risk as defined by the patient’s life stage, lifestyle, and place of origin and by environmental and epidemiologic factors. An update on feline injection-site sarcomas indicates that occurrence of this sequela remains infrequent and idiosyncratic. Staff education initiatives should enable the veterinary practice team to be proficient in advising clients on proper vaccination practices and compliance. Vaccination is a component of a preventive healthcare plan. The vaccination visit should always include a thorough physical exam and client education dialog that gives the pet owner an understanding of how clinical staff assess disease risk and propose recommendations that help ensure an enduring owner-pet relationship.

Assessment of body weight for age determination in kittens

OBJECTIVES

The objective of this study was to assess the utility of using body weight for age determination in kittens.

METHODS

Medical records were reviewed for serial body weight measurements collected from neonatal kittens (up to 8 weeks of age) from a breeding colony of specific pathogen-free domestic shorthair cats and for single-point body weight measurements of privately owned pediatric kittens (6-20 weeks of age) presenting for elective sterilization. Body weights were compared with known dates of birth and age assessed by dental eruption in combination with developmental characteristics.

RESULTS

The coefficient of determination (R2) between age and body weight in longitudinally sampled neonatal kittens was 0.88, while that for pediatric kittens sampled at a single time point was 0.54. Among neonatal kittens, predicted age based on the 1 lb (0.45 kg) of body weight gain per month of age guideline corresponded to within 1 week of actual age for 243 (98.8%), 234 (95.1%), 203 (82.5%) and 191 (77.6%) kittens at 2, 4, 6 and 8 weeks of age, respectively. Among pediatric kittens, predicted age based on this guideline corresponded to within 1 week of actual age for 24 (77.4%), 411 (67.5%), 170 (57.0%), 96 (46.6%), 23 (28.8%), 15 (27.8%), one (25%) and five (17.9%) kittens at 6, 8, 10, 12, 14, 16, 18 and 20 weeks, respectively.

CONCLUSIONS AND RELEVANCE

Body weight was an effective means of predicting age in kittens through 10 weeks of age. Factors other than body weight should be considered when estimating kitten age beyond that time point.

Cranial cavity filled with cerebrospinal fluid in an otter (Lontra longicaudis) - case report

ABSTRACT Computed tomography of the head of an otter with a history of incoordination, visual deficits, and seizures was performed. Intracranial images revealed a large non-enhancing fluid attenuating cystic lesion in the left frontoparietal region communicating with the left lateral ventricle and subarachnoid space. These findings are consistent with a congenital brain cavity filled by cerebrospinal fluid, with porencephaly being the most probable diagnosis based on the clinical and tomographic findings. The authors highlight the rarity of such a cystic lesion in wild animals, with this being the first report in otters.

Porencephaly and Periventricular Encephalitis in a 4-month-old Puppy: Detection of Canine Parvovirus Type 2 and Potential Role in Brain Lesions

A 4-month-old puppy died after showing intracranial signs a few days after a suspected viral enteritis. Grossly, the right cerebral hemisphere had a large irregular cavity external to the internal capsule. Histopathological examination revealed a cystic lesion in the right hemisphere and non-suppurative inflammation of the diencephalon and periaqueductal nervous tissue. Porencephaly associated with periventricular non-suppurative encephalitis was diagnosed. A nested polymerase chain reaction (PCR) identified the presence of parvovirus DNA in the brain and real-time PCR typed this as canine parvovirus (CPV) type 2a. Immunohistochemistry revealed the presence of CPV antigen in the cytoplasm of scattered cells in the subependymal layers and choroid plexus epithelium. The porencephaly was not associated with inflammatory lesions or CPV antigen and was considered to have preceded the neurological signs. In contrast, the detection of CPV antigen in the subependymal layers and choroid plexus epithelium supported the association of this virus with the periventricular encephalitis.

Feline Panleukopenia: A Re-emergent Disease

Feline panleukopenia (FPL) is caused by a Carnivore protoparvovirus infection. Feline parvovirus (FPV) causes most cases. When Canine parvovirus 2 (CPV-2) first emerged, it could not replicate in cats. All current CPV variants (CPV-2a-c) can infect cats to cause subclinical disease or FPL. Feline panleukopenia has re-emerged in Australia in shelter cats associated with failure to vaccinate. Parvoviruses can remain latent in mononuclear cells post-infection. Molecular methods such as polymerase chain reaction are used to determine the infecting strain. Current perspectives on causes, epidemiology, diagnosis, treatment, prognostic indicators, and management of outbreaks in shelters are reviewed.

Lymphoplasmacytic Meningoencephalitis and Neuronal Necrosis Associated With Parvoviral Infection in Cats

Neurologic manifestations other than cerebellar hypoplasia are rarely associated with feline panleukopenia virus (FPV) infection in cats. Here the authors describe lymphoplasmacytic meningoencephalitis and neuronal necrosis in 2 cats autopsied after exhibiting ataxia and nystagmus. Gross changes consisted of cerebellar herniation through the foramen magnum, with flattening of cerebrocortical gyri and narrowing of sulci. Histologically, lymphoplasmacytic meningoencephalitis, extensive neuronal necrosis, and neuroaxonal degeneration with digestion chambers were present in the telencephalon and brain stem in both cats. Frozen brain tissue of both cats was positive for parvoviral antigen via fluorescent antibody testing, and formalin-fixed, paraffin-embedded tissue sections of brain were immunoreactive for parvovirus antigen and positive for parvoviral DNA on in situ hybridization. Frozen brain tissue from 1 case was positive for parvovirus NS1 and VP2 genes using conventional polymerase chain reaction, and subsequent DNA sequencing and phylogenetic analysis revealed that the viral strain was a FPV. Reverse transcription quantitative polymerase chain reaction on formalin-fixed, paraffin-embedded brain tissue revealed high levels of parvovirus in both cases, supporting an acute and active viral infection. Although rare, FPV infection should be considered in cases of lymphoplasmacytic meningoencephalitis and neuronal necrosis in cats.

On-farm biosecurity practices and causes of preweaning mortality in Canadian commercial mink kits

Background

Mink are an important animal commodity group in Canada and excessive kit mortality represents a significant loss to production. National biosecurity standards have been developed for Canadian mink farms, but it is unclear how well these standards have been implemented as there are no studies correlating management practices of mink producers with causes of death in mink kits. To that end, we surveyed Ontario mink producers on their biosecurity and management practices and conducted almost 5660 post mortem examinations on found-dead, preweaned kits to characterize mink farm biosecurity practices and causes of death in preweaned kits.

Results

We found that very few biosecurity and management practices were uniformly used by producers, despite good awareness of appropriate practices. Use of personal protective equipment was implemented by fewer than 50% of respondents, while control of mink shed access, disinfection of feed containers after use, and use of a rodent control program were the only practices implemented by greater than 70% of respondents. Only 18% of producers reported regular use of antimicrobials in feed or water, although 91% stated they used antimicrobials for treatment of bacterial diseases on a regular basis. On post mortem examination, no gross abnormalities were noted in 71% of the kits, 45% were thought to be stillborn or aborted, 27% had some form of abnormal fluid distribution in the body, and 2% had a congenital malformation. A subset of 69 gastrointestinal tract samples was submitted for bacterial culture, of which 45 samples yielded sufficient growth. Most interesting was the identification of Salmonella enterica serovar Heidelberg in 11% of samples.

Conclusions

The results of this study will provide a benchmark for Canadian mink producers and their veterinarians, defining the areas to which greater attention should be given to ensure more rigorous biosecurity practices are in place. Ultimately, these improvements in practices may contribute to increased mink production and animal well-being.

Electronic supplementary material

The online version of this article (doi:10.1186/s13028-017-0326-8) contains supplementary material, which is available to authorized users.

2013 AAFP Feline Vaccination Advisory Panel Report

RATIONALE

This Report was developed by the Feline Vaccination Advisory Panel of the American Association of Feline Practitioners (AAFP) to provide practical recommendations to help clinicians select appropriate vaccination schedules for their feline patients based on risk assessment. The recommendations rely on published data as much as possible, as well as consensus of a multidisciplinary panel of experts in immunology, infectious disease, internal medicine and clinical practice.

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.

Porencephaly and hydranencephaly in six dogs

A retrospective study was performed to identify dogs with cerebrospinal fluid-filled cavitatory lesions on MRI. Six dogs were included and the lesions were classified. In the three dogs in the present study with hydranencephaly, unilateral but complete loss of the temporal and parietal lobes was noted and had almost complete loss of the occipital and frontal lobes of a cerebral hemisphere. In the three dogs with porencephaly, there was unilateral incomplete loss of the parietal lobe and one dog had additional partial loss of the temporal and frontal lobes. Two of the dogs with porencephaly had seizures; the third showed no associated clinical signs. The dogs with hydranencephaly had mentation changes and circled compulsively. The two porencephalic dogs with seizures were treated with phenobarbitone. One of the dogs with hydranencephaly showed increased frequency and duration of circling; one dog's clinical signs did not progress and the third dog was euthanased due to increasing aggression. The dog with increased circling had ventriculoperitoneal shunt placement and the circling frequency reduced.

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.

Hydranencephaly associated with cerebellar involvement and bilateral microphthalmia and colobomas

Hydranencephaly is an encephaloclastic central nervous system disorder characterised by severe destruction of the cerebral hemispheres with preservation of posterior fossa structures. We present MRI and neurosonography features of a unique case of hydranencephaly involving cerebellum (in the form of complete liquefaction of cerebellar hemispheres) and cerebral hemispheres with associated bilateral microphthalmia and ocular colobomas. This is an exceptional case as to the best to our knowledge. In humans, such a severe involvement of cerebellum has not been reported in cases of hydranencephaly. It is essential to distinguish hydranencephaly from gross hydrocephalus, as treatment and prognosis of the two are totally different. During differentiation, it is important to remember that severe cerebellar involvement can be seen in hydranencephaly.

Leukoencephalopathy associated with parvovirus infection in Cretan hound puppies

Leukoencephalopathies in dogs encompass presumably inherited conditions such as leukodystrophies, hypomyelination or spongiform degeneration, but other causes, such as virus infections and toxic or nutritional factors, might also play a contributory role. In this report, we provide evidence of parvovirus infection and replication in the brains of five 6-week-old Cretan hound puppies suffering from a puppy shaker syndrome and leukoencephalopathy. Although these puppies belonged to two different litters, they were closely related, tracing back two generations to the same sire. Histologically, a mild to moderate lymphohistiocytic meningitis, with focal lymphohistiocytic leukoencephalitis in two animals, and a mild to moderate vacuolation with myelin loss, mainly in the white matter of the cerebellum was detected. Vacuolation was also found in the corpus callosum, fimbria hippocampi, mesencephalon, capsula interna, basal ganglia, and hypothalamus. By immunohistology and in situ hybridization, either parvoviral antigen, DNA, mRNA, or replicative intermediate DNA were detected in the cerebellum, hippocampus, periventricular areas, corpus callosum, cerebral cortex, medulla oblongata, and spinal cord. Parvovirus antigen, DNA, and mRNA were present in cells of the outer granular layer of the cerebellum and in periventricular cells, most likely representing spongioblasts, glial cells, neurons, endothelial cells, occasional macrophages, and ependymal cells. Sequencing revealed canine parvovirus type 2 stretches. Thus, an association of parvovirus infection with the leukoencephalopathy seems likely, possibly facilitated by a genetic predisposition due to the mode of inbreeding in this particular dog breed.

Manifestations cutanées de la panleucopénie féline chez un chat

Un chat adulte exprimant une forme nerveuse et entéritique de la panleucopénie féline développe des lésions cutanées purpuriques. L’analyse histopathologique de biopsies cutanées met en évidence des lésions de vascularite non leucocytoclasique à prédominance mononucléée. Les vascularites sont particulièrement rares chez le chat et souvent idiopathiques. La démarche diagnostique comprend l’éviction de plusieurs hypothèses, médicamenteuses ou virales (virus d’immunodéficience féline [FIV], virus leucémogène félin [FeLV], péritonite infectieuse féline [PIF]). Ce cas rappelle le purpura Henoch-Schönlein, cause la plus fréquente de vascularite chez les enfants, qui serait associé à diverses causes dont une infection par le parvovirus B19.

Naturally occurring parvovirus-associated feline hypogranular cerebellar hypoplasia-- A comparison to experimentally-induced lesions using immunohistology

Three cases of feline cerebellar hypoplasia are presented. At the time of examination, the ages of the cats ranged from 2 months to 1 year. Necropsy revealed cerebellar and pons hypoplasia. Polymerase chain reaction for parvoviral deoxyribonucleic acid was positive in cerebellar tissue. Cell-specific immunolabeling was used to characterize the lesions, which were characterized into 2 types. In type 1 lesions, the cortex was nearly agranular, with an extremely thin molecular layer; the Purkinje cells were randomly placed and oriented, and their stunted main dendrite produced a thorn-covered atrophic dendritic tree; the basket cell axons ran randomly and had dysmorphic endings; and myelinated fibers were severely reduced in folia axes. In type 2 lesions, the cortex was hypogranular; the Purkinje cells were linearly organized, but their main dendrite extended too far in the molecular layer before giving up smooth, bent secondary dendrites; many basket cells were located along the cerebellar surface, and their axons ran at right angle to the surface; myelinated fibers were moderately reduced. Defects in climbing fiber synapse translocation and elimination were evident in both types of lesion. This immunohistologic study allowed a comparison between lesions in these spontaneous cerebellar hypoplasia cases with those documented when using silver impregnation studies after perinatal experimental cerebellar damage. Such a comparison is consistent with viral infection that occurs before birth in all 3 cases. Progress in parvovirus biology knowledge suggests that viral NS1 protein cytotoxicity might explain degenerative changes in the Purkinje cells that were present, in addition to the development defect.

Non-suppurative meningoencephalitis of unknown origin in cats and dogs: an immunohistochemical study

Non-suppurative meningoencephalitis of unknown cause is a frequent finding in dogs and cats. Fifty-three dogs and 33 cats with non-suppurative meningoencephalitis of unknown aetiology were examined immunohistochemically for 18 different infectious agents, including viruses, bacteria and prion protein^Sc. In 14 (26%) of the dogs and 13 (39%) of the cats a causative agent was identified in the central nervous system (CNS), two dogs and one cat giving positive results for two infectious agents simultaneously. The study revealed infections with known causative agents (porcine herpes virus 1, feline infectious peritonitis virus, Escherichia coli) and a new disease pattern of parvovirus infection in the CNS of dogs and cats. Infection of the CNS with feline leukaemia virus was found in a cat. Five dogs and four cats gave positive results for West Nile virus (WNV) antigen. In one dog, canine parainfluenza virus antigen was detected in the brain. Four dogs and four cats gave positive results for encephalomyocarditis virus (EMCV). The significance of the detection of WNV and EMCV antigen requires further study. The aetiology remained undetermined in 39 dogs (74%) and 20 cats (61%). Although it is possible that non-infectious causes play a more important role than previously thought, infections with hitherto unrecognized agents cannot be ruled out.

The 2006 American Association of Feline Practitioners Feline Vaccine Advisory Panel Report

Vaccination is a medical procedure, and the decision to vaccinate should be based on a risk-based assessment for each cat and each vaccine.

Clinical management of pregnancy in cats

Average gestation length in domestic cats is 65.6 days, with a range of 52–74 days. Average reported litter size is 4.0 kittens per litter; litter size is not correlated with number of matings in a given estrus. Superfecundation is common in domestic cats; superfetation never has been definitively proven to occur. Eclampsia may occur during pregnancy in queens, with non-specific clinical signs. Ectopic pregnancy and uterine torsion have been reported. Pregnancy loss may be due to infectious causes, including bacteria, viruses or protozoa, or non-infectious causes, such as hypoluteoidism and chromosome errors.

Use of a multiplex polymerase chain reaction assay in the antemortem diagnosis of toxoplasmosis and neosporosis in the central nervous system of cats and dogs

OBJECTIVE

To develop a multiplex polymerase chain reaction (PCR) assay for the detection of Toxoplasma gondii and Neospora caninum DNA in canine and feline biological samples. SAMPLE POPULATION; Biological samples from 7 cats with systemic (n = 4) or CNS (3) toxoplasmosis, 6 dogs with neospora- or toxoplasma-associated encephalitis, and 11 animals with nonprotozoal disease.

PROCEDURE

Primers for T gondii, N caninum, and the canine ferritin gene (dogs) or feline histone 3.3 gene (cats) were combined in a single PCR assay. The DNA was extracted from paraffin-embedded brain tissue, CSF, or skeletal muscle. The PCR products with positive results were cloned, and sequence identity was confirmed.

RESULTS

Of 7 cats and 4 dogs with immunohistochemical or serologic evidence of toxoplasmosis, PCR results were positive for all cats and 3 dogs for T gondii, and positive for T gondii and N caninum for 1 dog. Another dog had negative PCR results for both parasites. Of 2 dogs with immunohistochemical or serologic evidence of neosporosis, PCR results were positive for 1 for N caninum and positive for the other for T gondii. All negative-control samples yielded negative results for T gondii and N caninum on the PCR assay.

CONCLUSIONS AND CLINICAL RELEVANCE

Standard tests for toxoplasmosis or neosporosis associated with the CNS rely on serologic, histologic, or immunohistochemical analysis and can be difficult to interpret. The multiplex PCR assay with built-in control reactions could be a complementary clinical tool for the antemortem diagnosis of toxoplasmosis or neosporosis associated with the CNS.

PRENATAL SONOGRAPHIC DIAGNOSIS OF FETAL DEATH AND HYDRANENCEPHALY IN TWO CHIHUAHUA FETUSES

Hydranencephaly and fetal death was diagnosed in two of three fetuses during the abdominal sonographic examination of a 2.5-year-old, intact female Chihuahua that had clinical signs of dystocia 63 days after mating. A cesarean section was performed and one live normal puppy was present. Two dead puppies, each with a markedly enlarged and fluid filled skull were removed.

Polymerase chain reaction (PCR) amplification of parvoviral DNA from the brains of dogs and cats with cerebellar hypoplasia

Cerebellar hypoplasia in cats is caused most commonly by an in utero or perinatal infection with feline panleukopenia virus (parvovirus). Cerebellar hypoplasia has been reported infrequently in dogs, but no viral etiology has been identified to date. DNA was extracted from archival, paraffin-embedded, cerebellar tissue from 8 cats and from 2 canine littermates with cerebellar hypoplasia, 2 canine littermates with cerebellar cortical abiotrophy, 6 dogs with congenital cerebellar vermal defects, 1 dog with congenital hydranencephaly, and 15 dogs and cats with various encephalitdes. The DNA extracted from each cerebellum was subject to polymerase chain reaction (PCR) amplification by 3 primer pairs specific for parvovirus DNA. Sequence analysis of PCR products from each of the 8 cats and 2 dogs with cerebellar hypoplasia confirmed their identity with parvoviral DNA. The 6 dogs with cerebellar vermal defects, 2 dogs with cortical abiotrophy, 1 dog with congenital hydranencephaly, and all control samples were PCR negative for parvovirus. Parvoviral structural proteins were not identified by immunohistochemistry in either dog with cerebellar hypoplasia. This study shows that parvoviral DNA can be amplified from feline and canine archival brain tissue and that cerebellar hypoplasia in dogs might be associated with in utero parvovirus infection.

Feline vaccination guidelines

The 1998 Report of the American Association of Feline Practitioners and Academy of Feline Medicine Advisory Panel on Feline Vaccines was developed to help veterinary practitioners formulate vaccination protocols for cats. The current panel report updates information, addresses questions, and speaks to concerns raised by the 1998 report. In addition it reviews vaccine licensing, labeling, and liability issues and suggests ways to successfully incorporate vaccination protocol changes into a private practice setting.

Vaccine-associated adverse events

Although vaccination plays a vital role in maintaining animal health, there are risks associated with this medical procedure. Veterinarians are beginning to reexamine dogmatic vaccine protocols and consider both risks and benefits of vaccination, with special emphasis on adverse event information generated by practitioner experience. The current status of postmarketing surveillance for commercially available veterinary vaccines is presented, along with a discussion of the strengths and limitations of surveillance programs. An overview of adverse events commonly reported by veterinarians is included, along with practical information on how veterinarians can share their observations and learn about adverse events reported by their colleagues.

Developmental instability of the cerebellum and its relevance to Down syndrome

It has been recognized for many years that cerebellar abnormalities are frequently observed in association with Down syndrome (DS). An important question to be asked about these and other findings in DS is whether their occurrence (i) is attributable to specific loci on the triplicated chromosome or chromosomal segment or (ii) derives from exaggerated responses secondary to the genetic imbalance resulting from trisomy (Ts). Recently, similar cerebellar alterations were observed in subjects with DS and in Ts65Dn mice (Baxter et al., 2000), mice segmentally trisomic for a portion of chromosome 16, which is homologous for loci on the long arm of human chromosome 21. It was concluded by these authors that the occurrence of similar cerebellar changes in DS and in the DS mouse model resulted from triplication of these homologous loci in the two trisomic organisms, i.e. cerebellar development is affected similarly by homologous loci in each species. They wrote that their study of Ts65Dn mice "correctly predicts an analagous pathology in humans". . . and that. . . "The candidate region of genes on chromosome 21 affecting cerebellar development in DS is therefore delimited to the subset of genes whose orthologs are at dosage imbalance in Ts65Dn mice, providing the first localization of genes affecting a neuroanatomical phenotype in DS." Findings described in this review suggest otherwise--that cerebellar findings in DS and in the Ts65Dn mouse are a result of exaggerated vulnerability in general of the cerebellum to disturbing events and that liability to expression of response(s) is exacerbated by trisomy. This conclusion is based on the following: (i) the cerebellum has an extended postnatal development; (ii) numerous genetic, environmental, epigenetic and metabolic conditions express cerebellar changes similar to those observed in Down syndrome; (iii) most if not all chromosomal imbalance syndromes express similar cerebellar abnormalities; (iv) the cerebellum is particularly sensitive to diverse toxic agents which may act prenatally, postnatally and/or in the mature organism; and (v) cerebellar abnormalities similar to those found in Ts65Dn mice have been described in Ts19 mice which have no segments homologous to any segment of human chromosome 21. An unavoidable conclusion from the review is that triplication of specific loci on 21q is an unlikely explanation for the cerebellar findings in DS. A simple positive control, in which the effect of triplication of loci other than those in question on a specific phenotype, should be used in experiments comparing human and experimental trisomies. As pointed out many years ago by Lorke and his coworkers (Lorke et al., 1989; Lorke, 1994; Lorke and Albrecht, 1994) similar phenotypic findings in the presence of different trisomies in the same species would suggest that the trisomic state itself rather than the gene content of a particular trisomy is responsible for the genesis of traits at issue.