B.R. Jones

Elucidating the risk factors of feline lower urinary tract disease.

A questionnaire-based case-control study investigating the association of a range of host-related, owner-related and environmental risk factors with feline lower urinary tract disease was conducted in New Zealand over a 2-year period from 1991 to 1993. The study was subsequently extended in two ways, to examine the influence of the use of litter trays and to correlate weather records with the appearance of the disease in one particular region of the country. A range of statistical techniques was employed to analyse the data, including univariate odds ratio and chi-squared calculations, time series analysis, Poisson regression and conditional and unconditional logistic regression. Variables that were positively associated with lower urinary tract disease included low activity levels, the use of a litter tray coupled with restriction indoors, a high number of rainfall days in the month preceding the appearance of clinical signs, stress factors such as moving house within the last 3 months or the presence of more than one cat in the household, and a diet high in dry cat food. There was some indication that high levels of fluid consumption reduced the effect of a diet high in dry cat food. Other variables that appeared to have some protective effects included a routine visit to the veterinarian in the last 12 months and the use of alternative food sources such as rodents and birds.

First WNK4-Hypokalemia Animal Model Identified by Genome-Wide Association in Burmese Cats

Burmese is an old and popular cat breed, however, several health concerns, such as hypokalemia and a craniofacial defect, are prevalent, endangering the general health of the breed. Hypokalemia, a subnormal serum potassium ion concentration ([K+]), most often occurs as a secondary problem but can occur as a primary problem, such as hypokalaemic periodic paralysis in humans, and as feline hypokalaemic periodic polymyopathy primarily in Burmese. The most characteristic clinical sign of hypokalemia in Burmese is a skeletal muscle weakness that is frequently episodic in nature, either generalized, or sometimes localized to the cervical and thoracic limb girdle muscles. Burmese hypokalemia is suspected to be a single locus autosomal recessive trait. A genome wide case-control study using the illumina Infinium Feline 63K iSelect DNA array was performed using 35 cases and 25 controls from the Burmese breed that identified a locus on chromosome E1 associated with hypokalemia. Within approximately 1.2 Mb of the highest associated SNP, two candidate genes were identified, KCNH4 and WNK4. Direct sequencing of the genes revealed a nonsense mutation, producing a premature stop codon within WNK4 (c.2899C>T), leading to a truncated protein that lacks the C-terminal coiled-coil domain and the highly conserved Akt1/SGK phosphorylation site. All cases were homozygous for the mutation. Although the exact mechanism causing hypokalemia has not been determined, extrapolation from the homologous human and mouse genes suggests the mechanism may involve a potassium-losing nephropathy. A genetic test to screen for the genetic defect within the active breeding population has been developed, which should lead to eradication of the mutation and improved general health within the breed. Moreover, the identified mutation may help clarify the role of the protein in K+ regulation and the cat represents the first animal model for WNK4-associated hypokalemia.

Chlamydia infection in cats in New Zealand

Conjunctival swabs collected in 1991-92 from 333 pedigree and non-pedigree cats were tested for the presence of Chlamydia spp. antigen using an ELISA antigen kit. Forty (18.4%) of the 217 samples from cats with conjunctivitis were positive. Seven (6%) of 116 samples from cats which were in contact with cats with conjunctivitis but which showed no clinical signs at the time of sample collection were positive. Positive-testing cats were frequently from multi-cat households. Chlamydia spp. is present and associated with conjunctivitis in cats in New Zealand. Infection may occur concurrently with viral diseases. Feline calicivirus was recovered from 27 (21 with conjunctivitis) of 37 cats tested in five catteries. Four cats (with conjunctivitis) were FIV-positive.

Protozoa1 encephalomyelitis of dogs involving Neosporum caninum and Toxoplasma gondii in New Zealand

In a retrospective study of 15 cases of encephalomyelitis in dogs, three cases of Neospora caninum and two cases of Toxoplasma gondii infection were identified using immunohistochemical staining of central nervous system sections. All cases of neosporosis showed ataxia and progressive hind limb paralysis due to multifocal non-suppurative meningoencephalomyelitis which was most severe in the spinal cord and base of the brain stem. Neospora tissue cysts could not be distinguished morphologically from those of T. gondii using light microscopy, but electron microscopy confirmed their characteristic features. Although Neospora abortion in cattle has only recently been recognised in New Zealand, this study has shown that neosporosis has been present in dogs since at least 1972.

The pathology of an inherited hyperlipoproteinaemia of cats

The gross and histological features of congenital lipoprotein lipase deficiency are described in eight cats. The main histological features could be directly related to the presence of the chylomicronaemia. They consisted of lipid accumulation within clear vacuoles or ceroid accumulation within residual bodies in parenchymatous organs such as the liver, spleen, lymph nodes, kidney and adrenal gland. Xanthomata were seen in various sites, probably arising either from frank haemorrhage or the leakage of lipid-rich plasma perivascularly. As in human lipoprotein lipase deficiency there was no evidence of the formation of atherosclerotic plaques. Focal degenerative changes were, however, present within arteries and this may indicate blood vessel weakness and explain the tendency to haemorrhage and xanthomata/granulomata formation. The degeneration and fibrous replacement of glomeruli and nephrons possibly arises from pressure necrosis of adjacent xanthomata and alterations in renal blood flow.

Myotonia in related Chow Chow dogs

Summary A myopathy associated with myotonia was observed in three related Chow Chow dogs. The clinical signs were first noticed at 2 to 3 months of age. They included muscle spasm and stiffness of gait which decreased in severity with exercise. Electromyographic findings and the demonstration of a muscle percussion dimple confirmed the presence of myotonia. Dystrophic changes were observed in muscle biopsies but histochemical techniques did not demonstrate fibre type changes. An inherited aetiology was suspected but not confirmed.

Nerve sheath tumours in the dog and cat.

Schwannomas were diagnosed in twelve dogs and five cats at Massey University Small Animal Clinic and Hospital over a 15-year period (1977-92). A further two feline cases were reported at the Batchelar Animal Health Laboratory. In six dogs, the tumour involved nerves of the brachial plexus. Clinical signs observed in these dogs were forelimb lameness, muscle wasting and pain on movement of the affected limb or neck. Hindlimb paresis was observed in two dogs. Surgical excision of the brachial plexus tumour was attempted in one dog, leading to an 8-month remission of signs. In one dog, the tumour involved the sacral nerves, and in two dogs the cranial nerves were affected. Three dogs had skin nodules. Seven of the twelve affected dogs were destroyed. In five cats, the tumours developed on the carpus, tarsus or interdigital area of a forelimb or hindlimb as a slowly developing nodular lesion. In the other two cats, the site of the tumour was the flank and the lateral thigh respectively. Surgical excision of the tumour was successful in three cats.

Neutropenia with a probable hereditary basis in Border Collies

This paper documents a disease of Border Collies characterised by chronic neutropenia which probably resulted in recurrent bacterial infections manifesting as osteomyelitis and sometimes gastroenteritis. The neutropenia occurred despite hyperplasia of the myeloid cells in the bone marrow and a shift to the right in myeloid cell maturation. The underlying defect is currently unknown but may result from the inability of neutrophils to escape from the bone marrow into the peripheral circulation. Necrosis and new bone formation commonly involved the metaphyseal regions of long bones. Other findings included a fasting hypercholesterolaemia and the occasional presence of nucleated red blood cells in circulation, despite a non-regenerative anaemia. An autosomal recessive mode of inheritance is suspected. This condition has some features of a rare human disease called myelokathexis which is also believed to have in autosomal recessive mode of inheritance.

Localised tetanus in two cats after ovariohysterectomy

Localised tetanus was diagnosed in two cats 14 and 21 days after ovariohysterectomy by a left flank surgical approach. The diagnosis in each case was based on their history, clinical signs and diagnostic investigations which excluded other possible diagnoses. Both cats showed scoliosis of the lumbar spine and left hind limb spasticity. One cats clinical signs were exacerbated after the administration of corticosteroids. One cat was treated with oral amoxycillin and diazepam, and the second cat received penicillin, tetanus antitoxin, methocarbarnol and diazepam. Both cats improved after treatment but recovery was prolonged and the spasticity did not resolve until 12 weeks after diagnosis in one cat. The second cat was lost to follow up after 8 weeks.

Granulomatous meningoencephalomyelitis of dogs in New Zealand

A progressive neurological disease affecting twenty-two young adult dogs of smaller breeds is reported. The disease was most often acute in onset and the neurological signs included cervical pain, seizures, behavioural changes, ataxia, head tilt, muscle tremor and paresis. The lesions were those of a disseminated granulomatous meningoencephalomyelitis in which perivascular cuffs of macrophages and lymphoid cells were the predominant finding. Severe lesions were most often seen in the cerebral white matter although the brain stem, mid-brain and spinal cord were also commonly affected.