Deafness in Australian Cattle Dogs associated to QTL on chromosome 20 in genome-wide association study analyses.

Pigment-associated deafness is a common hereditary condition in a range of dog breeds. The aim of this study was to perform a genome-wide association analysis to investigate the genetic architecture of deafness in Australian Cattle Dogs. Genotypes for 104 757 polymorphisms in 216 dogs were available for analyses after quality control. A genomic relationship matrix was used in the mixed model analyses to account for polygenic effects, as we tested each polymorphism for its association with deafness, in a case/control experimental design. Three approaches were used to code the genotypes and test for additive, recessive and dominant SNP effects. The genome-wide association study analyses identified a clear association peak on CFA20, with the most significant SNPs on this chromosome (1.29 × 10-4 ) in the vicinity of MITF. Variants in MITF have been associated with white pigmentation in dogs and with deafness in humans and other species, supporting the premise that canine deafness is associated with variants in or near this gene. A recessive inheritance for the peak in CFA20 is possible given the significant results in the recessive model; however, the estimated heritability was low (4.54 × 10-5 ). Further validation, identification of variants and testing in other dog breeds are needed.

Consequences of a screening programme on the prevalence of congenital hereditary sensorineural deafness in the Australian Cattle Dog.

Genetic disease testing programmes are used in domestic animal breeds to guide selective breeding with the aim of reducing disease prevalence. We assessed the change in the prevalence of canine congenital hereditary sensorineural deafness (CHSD) in litters of Australian Cattle Dogs following the introduction of a brainstem auditory evoked response (BAER) testing programme. We studied 608 pups from 122 litters from 10 breeding kennels. Despite 10 years of testing (1998-2008), no substantial reduction in prevalence of CHSD was evident in these 10 breeding kennels. Even for the subset of litters in which both parents were BAER tested as normal hearing (305 pups from 58 litters), there was no evidence of substantial reduction in prevalence. Odds ratios for CHSD in pups for each extra year since testing in the kennel commenced were 1.01 (95% CI, 0.88-1.17) and 1.03 (95% CI, 0.82-1.30) respectively for these populations. Amongst 284 dogs from 54 litters with extended pedigrees and both parents BAER-tested normal hearing, observed prevalences of CHSD were highest in pups with no BAER-tested normal grandparents (17% or 5/29) and lowest in pups with all four grandparents tested normal (0% or 0/9). In pups for which one, two and three grandparents tested negative, prevalences of CHSD were 12% (9/74), 9% (9/101) and 8% (6/71) respectively. Hence, testing programmes based on phenotypic screening may not lead to a substantial reduction in recessive genetic disease prevalence over the medium term, even when only tested normal parents are used. Exclusive breeding of litters in which both parents and all four grandparents are BAER-tested normal is expected to reduce CHSD prevalence in pups to the greatest extent over the long term.

Correlative imaging findings in seven dogs and one cat with spinal arachnoid cysts.

Information regarding 7 dogs and 1 cat with a spinal arachnoid cyst is presented. All patients were evaluated with survey radiographs and myelography. Computed tomography (CT) following myelography, magnetic resonance (MR) imaging, and sonography, were used in some of the patients. These imaging techniques were evaluated to determine their efficacy in diagnosing arachnoid cysts, ascertaining the extent and internal cyst architecture and detecting associated spinal cord abnormalities. Survey radiographs were nondiagnostic in all patients. Myelographically, the arachnoid cyst was visible in all patients, with partial blockage to flow of contrast medium. CT provided additional information on localization and lateralization of the cyst, and allowed measurement of the degree of spinal cord compression. MR imaging enabled identification of an associated syringomyelia. Sonography was useful for defining the cyst wall and characterizing the internal architecture of the cyst cavity and adjacent spinal cord. Measurements of the degree of spinal cord compression could be made and were similar to measurements made from CT. Additionally, sonography was considered a useful technique for orientating the surgeon to the location and extent of the cyst. In the absence of the availability of CT or MR imaging for evaluating patients with an arachnoid cyst, sonography is considered a valuable technique for directly assessing the spinal cord for associated disease. Decompressive surgery was performed on 4 dogs and 1 cat, all with successful outcomes.

Transient-evoked and 2F1-F2 distortion product oto-acoustic emissions in dogs: preliminary findings.

Transient (click)-evoked oto-acoustic emissions (TEOAEs) and distortion product oto-acoustic emissions (DPOAEs) were recorded in a feasibility study in 7 healthy mixed-breed dogs using the ILO 92 OAE analyser (Otodynamics, Hartfield, UK). Five dogs were found to have normal hearing in both ears and 2 dogs in the left ear only following otoscopy, tympanometry and auditory brainstem response audiometry. Twelve sets of TEOAEs (click-evoked) to 80 dB peSPL click stimulus and 9 sets of DPOAEs (2F1-F2) to 8 different stimulus levels of the primary tones (L1/L2) were collected at 11 test frequencies (F2) in these normal-hearing dogs. TEOAEs were successfully recorded in 11 of the 12 ears using the default user setting and in all 12 ears using the quickscreen program. DPOAEs were successfully recorded in all 9 ears tested. While the TEOAEs parameters matched those for humans, the average signal-to-noise ratio of DPOAEs was considerably higher in the dogs. Stimulus levels at 55/55, 55/45 and 55/35 dB SPL were demonstrated to produce DPOAEs that seem to reflect the active dynamic status of the outer hair cell system. Postmortem DPOAEs at these stimulus levels and TEOAEs at 80 Db peSPL could not be elicited 5 min following euthanasia of dogs. However, DPOAEs could still be recorded albeit with reduced amplitude at stimulus levels where L1 > 55 dB SPL. The results suggest that TEOAEs and DPOAEs in dogs have the potential to provide valuable insights into their mechanisms of generation, and the specific role and behaviour of outer hair cells of the cochlea in certain pathological conditions, particularly in drug-induced ototoxicity, in humans.

Surgical management of multiple congenital intrahepatic shunts in two dogs: case report.

OBJECTIVE: To present details of an unusual type of portosystemic shunt and its surgical management in two dogs. ANIMALS: Two young dogs that had a tentative diagnosis of a portosystemic shunt on the basis of clinical signs and serum biochemical abnormalities. Abdominal ultrasonography and contrast portography demonstrated multiple intrahepatic shunts. In both cases, the multiple shunts arose from a single branch of the portal vein. OUTCOME: It was possible to locate and attenuate flow through the shunts via a transportal venotomy under conditions of hepatic vascular occlusion. Clinical and biochemical abnormalities resolved after surgery in both dogs. Postoperative sonography revealed complete obliteration of the shunt plexus in one of the dogs.

Transmission of human and feline immunodeficiency viruses via reused suture material.

Several documented cases of human immunodeficiency virus (HIV) infection have involved unconventional or unknown modes of transmission of the virus. Some such cases have occurred within a surgical setting. We investigated the potential for transmission of HIV on suture material that had been reused following passage through an HIV-infected patient. Initial experiments were conducted in vitro using HIV. To provide stronger evidence that HIV could be transmitted via this route, further experiments were undertaken in vivo using a feline immunodeficiency virus (FIV)/cat model. Both methods indicated the possibility of transmission of virus if suture materials were reused.