No abstract

Lymphocytic thyroiditis is a common canine condition that can lead to functional hypothyroidism. It is associated with more than 50% of cases of canine hypothyroidism. Evidence in human beings and experimental situations suggests that it is a disease of defective immunoregulation, but specific investigation of the molecular pathogenesis of the naturally occurring disease in dogs has not yet been carried out. The condition is heritable in those breeds that have been studied, and progression to hypothyroidism, if it occurs, can be slow. Factors that influence the progression from subclinical thyroiditis to hypothyroidism in dogs are still to be identified, but excessive iodine intake is an important factor in other species.

Pha rmacological management of feline hyperthyroidism offers a practical treatment option for many hyperthyroid cats. Two drugs have been licensed for cats in the last decade: methimazole and its pro-drug carbimazole. On the basis o f current evidence and available tablet sizes, starting doses of 2·5 mg methimazole twice a day and 10 to 1 5 mg once a day for the sustained release formulation of carbimazole are recommended. These doses should then be titrated to effect in order to obtain circulating total thyroxine (TT4) concentrations in the lower half of the reference interval. Treated cases should be monitored for side-effects, especially during the first months of treatment. Some side-effects may require discontinuation of treatment. At eac h monitoring visit, clinical condition and quality of life should also be evaluated, with special attention to possible development of azotaemia, hypertension and iatrogenic hypothyroidism. When euthyroidism has been achieved, monitoring visits are recommended after 1 month, 3 months and biannually thereafter. Cats with pre-existing azotaemia have shorter survi val times. However, development of mild azotaemia during the initial course of treatment, unless associated with hypothyroidism, does not appear to decrease survival time. The long-term effects of chronic medic al management require further study.

Thyroid hormone autoantibodies may falsely increase measured triiodothyronine (T3) and thyroxine (T4) concentrations in dogs; results suggest that T3 concentration may be falsely increased in approximately 57 of 1,000 dogs with hypothyroidism and that T4 concentration may be falsely increased in approximately 17 of 1,000 dogs with hypothyroidism. Results also suggested that dogs of certain breeds were significantly more or less likely to have THAA than were dogs in general.

Lymph node cytology is a useful diagnostic procedure but educating veterinarians to improve sampling and smearing may increase diagnostic yield.

Frequencies of antimicrobial resistance were determined amongst 14,555 clinical Staphylococcus intermedius group (SIG) isolates from UK dogs and cats to estimate resistance trends and quantify the occurrence of meticillin-resistant Staphylococcus pseudintermedius (MRSP). Reports from two diagnostic laboratories (13,313 general submissions, 1242 referral centre only submissions) were analysed retrospectively (2003/2006-2012). MRSP were defined by phenotypic resistance to meticillin and concurrent broad β-lactam resistance; a subset was confirmed genetically (SIG-specific nuc and mecA). Trends were analysed by Cochran-Armitage test. Resistance remained below 10 per cent for cefalexin, amoxicillin-clavulanic acid and the fluoroquinolones. Increasing resistance trends were seen in both laboratories for ampicillin/amoxicillin (both P<0.001), cefovecin (both P<0.046) and enrofloxacin (both P<0.02). Resistance to cefalexin increased over time in referral hospital isolates (P<0.001) to clindamycin (P=0.01) and trimethoprim-sulfamethoxazole (P=0.001) amongst general laboratory submissions. Overall, 106 MRSP were isolated (0.7 per cent of submissions) including 32 (2.6 per cent of submissions, all genetically confirmed) from the referral centre population (inter-laboratory difference P<0.001). Against a background of widely susceptible SIG isolates, a new trend of increasing resistance to important antimicrobials was identified overtime and the emergence of MRSP from UK clinical cases was confirmed. Attention to responsible use of antibacterial therapy in small animal practice is urgently needed.

Human IRMA for PTHrP (1-84) can be used to measure PTHrP in cats. Malignancies, particularly carcinomas, appear to secrete PTHrP and induce HHM in this species. Immunohistochemistry alone cannot predict the occurrence of HHM in cats.

Dogs exhibit a range of immune-mediated conditions including a lymphocytic thyroiditis which has many similarities to Hashimoto's thyroiditis in man. We have recently reported an association in Doberman Pinschers between canine hypothyroidism and a rare DLA class II haplotype that contains the DLA-DQA1*00101 allele. We now report a further series of 173 hypothyroid dogs in a range of breeds where a significant association with DLA-DQA1*00101 is shown.