Tag Archives: Australian Shepherd

Velban (Vinblastine) for Injection

ANTINEOPLASTIC Highlights of Prescribing Information A Vinca alkaloid antineoplastic used for a variety of tumors in dogs (& sometimes cats) Contraindications: Preexisting leukopenia or granulocytopenia (unless a result of the disease being treated) or active bacterial infection; reduce dose if hepatic disease Adverse Effects: Gastroenterocolitis (nausea/vomiting), myelosuppression (more so than with vincristine); may also cause constipation, alopecia, stomatitis, ileus, inappropriate ADH secretion, jaw & muscle pain, & loss of deep tendon reflexes CATS can develop neurotoxicity causing constipation or paralytic ileus & aggravating anorexia; can also develop reversible axon swelling & paranodal demyelination Potentially teratogenic Avoid extravasation; wear gloves & protective clothing when preparing or administering Drug Interactions What Is Drug Used For? Vinblastine may be employed in the treatment of lymphomas, carcinomas, mastocytomas, and splenic tumors in small animals. It is more effective than vincristine in the treatment of canine mast cell tumors. Pharmacology / Actions Vinblastine apparently binds to microtubular proteins (tubulin) in the mitotic spindle, thereby Read more […]

The Globe And Orbit

Congenital Abnormalities Microphthalmos. Failure of the eye to develop to normal size is referred to as microphthalmos. Complete absence of the eye (anophthalmos) is extremely unusual in puppies and kittens. Microphthalmos is characterized by varying degrees of enophthalmos, with or without other ocular defects. Microphthalmos with multiple colobomas is an autosomal recessive trait linked to coat color in the Australian shepherd. In addition to small globes, affected dogs may have persistent pupillary membranes, cataract, equatorial staphylomas, choroidal hypoplasia, retinal dysplasia and detachment, and optic nerve hypoplasia. Vision is frequently impaired. Other breeds in which multiple ocular defects have been associated with coat color include the Great Dane, collie, Shetland sheepdog, and dachshund. Microphthalmos is also associated with inherited congenital cataracts in the miniature schnauzer, Old English sheepdog, Akita, and King Charles Cavalier spaniel. Microphthalmos occurs with retinal dysplasia in Bedlington terriers, Sealyham terriers, beagles, Labrador retrievers, and Doberman pinschers. Administration of griseofulvin to pregnant cats may produce microphthalmos in their offspring. Atypical Eye Position. Read more […]

The Anterior Uvea

The irides of the puppy and kitten are often a different color than those of the adult. The blue-gray iris of puppies and kittens usually changes to the adult coloration within a few weeks. Iris color is ultimately related to the degree of stromal pigmentation and is influenced by coat color. Congenital Abnormalities Persistent Pupillary Membranes. Persistent pupillary membranes are strands of tissue that arise from the anterior iris surface and represent remnants of an embryonic vascular system. The persistent pupillary membranes may be confined to the iris surface or may extend from the iris to the cornea or lens (). Persistent pupillary membranes are inherited in the basenji. Iris Cysts. Iris cysts are floating, fluid-filled vesicles that arise from the posterior iris epithelium and are usually found in the anterior chamber. Iris cysts may be unilateral or bilateral and singular or multiple in number. Pupillary Abnormalities. A notch-like defect (coloboma) is occasionally seen in the ventronasal pupillary border of young dogs and cats, resulting in a keyhole-shaped pupil. An eccentric pupil (corectopia) may accompany multiple ocular defects, as occurs in the Australian shepherd. Eccentric pupils are usually Read more […]

The Lens and Vitreous

The lens develops rapidly in the early stages of embryogenesis, during which time it is nourished by the hyaloid vessel. The fully developed lens is avascular; by the second week of life, no remnants of the hyaloid system should remain. The normal lens often exhibits minor imperfections that can be easily detected with magnification in dogs and cats younger than 1 year. These include prominent anterior and posterior Y sutures and minute granules in its nucleus and cortex. A mosaic of brown pigment spots is occasionally seen on the anterior lens capsule near the center of the pupil, representing remnants of embryonic mesoderm. Disease of the vitreous would be expected to influence the lens or retina because of its attachments at the posterior lens surface and the optic disc. Congenital Abnormalities Congenital lens abnormalities include alterations in size or shape. Congenital absence of the lens (aphakia) is uncommon. In microphakia, the margin of the abnormally small lens along with elongated ciliary processes may be observed after pupillary dilation. Microphakia occurs along with other ocular defects in the Saint Bernard and beagle and in cats. Luxation of the microphakic lens may cause glaucoma. Lenticonus is a Read more […]

The Retina and Optic Nerve

Tapetal coloration of the fundus of the puppy and kitten is usually gray or blue at 6 to 8 weeks of age, gradually acquiring its adult coloration by 4 to 7 months of age when the tapetum matures. Myelination of the optic disc may also be incomplete in the puppy and kitten, giving the impression of a small, well-defined nerve head that takes on a more fluffy appearance as adult myelination occurs.Both congenital and acquired disorders of the retina and optic nerve are recognized in the young dog and cat. These may be inherited, as with collie eye anomaly, or secondary to postnatal influences, as occurs with canine distemper-induced retinitis. Congenital abnormalities can be diagnosed as early as 6 weeks of age, when the posterior segment is clearly observed. The more common congenital abnormalities of the canine fundus are summarized in Table Congenital Abnormalities of the Canine Fundus. Acquired abnormalities develop with advancing age and in this discussion are limited to those in dogs and cats younger than 6 months of age. Table Congenital Abnormalities of the Canine Fundus (diagnosed as early as 6-8 wk of age). DISORDER BREED CHARACTERISTIC FEATURES Collie eye anomaly Collie, Shetland sheepdog, Read more […]

The Eye As An Optical Device

A primary function of the eye is to form a crisply focused image on the retina. The optical components through which light travels to reach the retina are the cornea, aqueous humor, lens, and vitreous body. For proper image formation these components must remain transparent and maintain precise relationships to one another. One of the exciting areas of ongoing research is attempting to define the mechanisms whereby these relationships are maintained during growth of the eye. A point source of light located at the visual horizon emits rays that are convergent, divergent, and parallel relative to the eye. At a great distance only rays that are essentially parallel will enter the pupil of the dog. Divergent and convergent rays will pass peripheral to the pupillary aperture. If the eye is focused at infinity (is emmetropic), parallel rays will be refracted and imaged as a point on the dog’s retina. If the dog’s eye is ametropic (either myopic or hyperopic), the rays will not be properly imaged on the retina and will form a blurred circle. As an object is brought closer and closer to the dog’s eye, the percentage of divergent rays entering the pupil will increase, requiring an increase in refractive power of the Read more […]

Adverse CNS reactions caused by drugs

Ivermectin and related drugs The adverse central nervous system effects caused by ivermectin, and similarly acting drugs such as moxidectin and milbemycin, are well documented in the veterinary literature. Theavermectin and milbemycin classes of parasiticides enhance the effects of GABA and stimulate its release from nerve endings. In parasites, increased GABA activity causes paralysis and death of the organism. Ordinarily dogs and cats are resistant to these effects because these drugs do not cross the BBB. However, when these drugs are administered to certain breeds of dog that permit them to cross the BBB, central nervous system toxicity results. Collies, Shetland Sheepdogs, English Sheepdogs, Australian Shepherd Dogs and perhaps other breeds have this susceptibility. It is now recognized that dogs susceptible to ivermectin toxicosis have a mutation in the MDR1 gene that codes for P-gp in the blood-brain barrier. The adverse central nervous system effects of ivermectin are most likely caused by accumulation of the drug in the brain because P-gp, which normally would transport the drug out of the brain through the BBB, is deficient or inhibited. In mice deficient in expression of P-gp (CF-1 mice) the doses of ivermectin Read more […]

Activities

Swimming Swimming is a great way for dogs to get their exercise. It is a low-impact form of exercise that doesn’t tax any joints, but builds muscles. Dogs that are prone to gaining weight can swim to remain in shape and cut pounds from their frames. Good health can be maintained while the dog is having fun. Swimming is also a great way to safely exercise your dog in the summer heat. She can exercise and keep her body temperature down at the same time. Equipment for swimming can be minimal, yet there are certain things to have with you to provide a safe swimming experience for you and your pet. A long leash helps your dog learn to return to your side and gives you some control over where she’s swimming. Wear water shoes of some sort. You should be prepared to go in the water to teach your dog to swim, and you should always be prepared to jump in — even with a seasoned swimmer, just in case something happens. Having a toy to retrieve is helpful once the dog has learned to swim. Not all dogs (even sporting breeds) know how to swim right away, so do not throw your dog into the water in the hopes of his learning quickly. This will only scare him and perhaps cause panic and an accident. Do not make this new learning Read more […]

Sensory Abilities: Audition

The dog’s ear is composed of an outer ear (pinna), auditory canal, and various structures designed to convert sound waves into auditory information. The pinna gathers and directs sound into the auditory canal, where it is carried to the tympanic membrane or eardrum. The eardrum is an extremely sensitive and elastic membrane reacting to the slightest vibrations on its surface: movement of less than one-tenth the diameter of a hydrogen atom can produce an audible sensation. The vibrations caused by the pressure of sound waves on the eardrum are mechanically conducted to the cochlea through the mediation of three tiny bones or ossicles: the malleus, the incus, and the stapes. The cochlea is a snail-like tubular structure that is innervated by the auditory nerve. Sound vibrations are passed into the cochlea at the oval window. These vibrations cause a fluid wave in the cochlear fluid, which causes a rippling effect against the surrounding basilar membrane. The vibratory displacement of the basilar membrane stimulates auditory receptors (called hair cells) to bend rhythmically, thereby evoking a nerve potential that is carried by individual fibers into the auditory nerve. Different sounds are distinguished by the specific Read more […]

The faults and defects of the breeds: Herding Dogs

Australian Cattle Dogs OCD (osteochondrities dissecans) of the hock Australian Shepherds Hip dysplasia; Dwarfism; Spina bifida Bearded Collies Hip dysplasia Belgian Malinois Hip dysplasia Belgian Sheepdogs Hip dysplasia; Neoplaisa Belgian Tervurens Hip dysplasia; Thyroid disorders Border Collies OCD (osteochondrities dissecans); Hip dysplasia Bouviers des Flandres Elbow dysplasia; Hip dysplasia Briards Thyroid disorders; Hip dysplasia Cardigan Welsh Corgis Medial patella luxation Collies (Rough and Smooth) Dwarfism; Neoplasias German Shepherd Dogs Dwarfism; Panosteitis, shown as limb pain and intermittent lameness between the ages of 6 and 12 monts; Hip dysplasia; UAP (ununited anconeal process); Cartilagenous Exostosis; Pannus; Elbow dysplasia; Neoplasias; Thyroid disorders; OCD (osteochondrities dissecans); Degenerative myelopathy causes progressive hind limb paralysis in middle age to older dogs. Old English Sheepdogs Hip dysplasia; Wobblers syndrome Pembroke Welsh Corgis IVD (intervertebrate disk disease); Hip dysplasia; Swimmers syndrome Pulik Hip dysplasia Shetland Sheepdogs Hip dysplasia; Dwarfism; Thyroid disorders; Neoplasias; Muscular dystrophy Read more […]