ADVANCED DIAGNOSTIC IMAGING AND PATHOLOGIC FINDINGS OF THYROID LESIONS IN TWO SHORT-BEAKED ECHIDNAS (TACHYGLOSSUS ACULEATUS).

Two zoo-maintained short-beaked echidnas (Tachyglossus aculeatus) had long histories of intermittent anorexia and lethargy. Case 1 presented with a recurrence of these signs after transfer to another facility and died shortly after arrival. A focal area of hyperattenuation within the paratracheal tissue of the cranial mediastinum was noted antemortem on CT. Postmortem, this corresponded with severe thyroid follicular hyperplasia with lymphoplasmacytic thyroiditis. Additional findings included a systemic fungal infection without an inflammatory response, suggesting underlying factors such as torpor or immunosuppression. In Case 2, an intrathoracic mass was identified during a preshipment examination. CT confirmed a contrast-enhanced mass compressing the cranial vena cava and right atrium, and the animal was euthanized. The mass was diagnosed histologically as thyroid adenocarcinoma. These cases report thyroiditis and thyroid adenocarcinoma in echidna and describe the use of IV contrast and CT as a diagnostic aid in this species.

Accidental finding of Hashimoto-like thyroiditis in male B.U.T. 6 turkeys at slaughter.

In the context of a study on the tolerance of rapeseed meal in B.U.T. 6 turkeys, thyroid glands were histologically and immunohistochemically examined because of potential thyreostatic effects. In all groups including the controls with no rapeseed meal in their food, there was a high incidence of lymphocytic infiltration and thyroiditis (14% of thyroids with moderate to severe lymphocytic thyroiditis). Thirty per cent of mononuclear inflammatory cells were immunohistochemically identified as T cells. There were occasional accumulations of PAX-5 labelled cells, indicating germinal centre development. These lesions resemble Hashimoto's disease in humans. The effect on thyroid function is unknown. Mild hypothyreosis might enhance productivity but also explain dispositions towards diseases seen in context with thyroid dysfunction such as skin diseases (foot pad disease?) and cardiovascular problems. Further studies on thyroid function in these turkeys are needed.

The thyroid gland in bottlenose dolphins (Tursiops truncatus) from the Texas coast of the Gulf of Mexico: normal structure and pathological changes.

Fresh thyroid glands (n=60) from Atlantic bottlenose dolphins that died after stranding along the Texas coast between 1991 and 2005 were examined. Organ weight ranged from 11 g in a neonate (length 109 cm) to 58 g in a large (249 cm) male. More typical weights were 25-45 g (mean=30.6 g). Glands tended to be larger in pregnant and lactating females (mean 37.4 g; n=5) than in non-pregnant animals of comparable size. In infancy, the gland tended to be compact, relatively homogeneous, and sometimes partly lobular, but with advancing age it became more lobular, the lobules being defined by fibrous bands. In one 8-year-old female (233 cm), and in a large male (295 cm) aged>25 years the gland was represented by a cluster of lobules. Lobulation was not necessarily accompanied by increased weight, distinguishing it from hyperplasia. With age, variation in follicle size and colloid density tended to increase. Two animals (3%) had adenomas and five (8%) had discrete hyperplastic nodules, not to be confused with lobulation. Five (8%) had macroscopically identifiable colloid-filled cysts (1-4 mm in diameter). Nine animals (15%) had squamous cysts (4-15 mm) containing creamy white fluid. Other abnormalities included patchy or diffuse interstitial fibrosis (six cases, 10%) amyloidosis (two cases), thyroiditis (one case) and vasculitis (one case). No malignant neoplasms were found. Cells presumed to be C cells (light cells, parafollicular cells) were identified immunohistochemically with synaptophysin antibody.

Lack of association between repeated vaccination and thyroiditis in laboratory Beagles.

BACKGROUND: Intensive vaccination protocols have been suggested as partially responsible for an increased prevalence of autoimmune diseases in dogs in recent years. The aim of this study was to determine whether repeated routine vaccination in dogs is associated with an increased prevalence of thyroiditis. METHODOLOGY/PRINCIPAL FINDINGS: We conducted a prospective experimental study with 20 healthy purpose-bred Beagles. Five dogs were vaccinated with a multivalent vaccine and a rabies vaccine. Five dogs received only the multivalent vaccine, and 5 dogs received only the rabies vaccine. Five dogs were unvaccinated controls. The multivalent vaccine was administered at 8, 10, 12, 16, 20, 26, and 52 weeks of age and every 6 months thereafter. The rabies vaccine was administered at 16 and 52 weeks of age and then once a year. Blood samples were collected 1 week before euthanasia for evaluation of thyroid profiles and measurement of antibodies directed against canine thyroglobulin. Dogs were euthanized at 5.5 years of age, and the thyroid glands were evaluated histopathologically. Thyroiditis was present in 8 of 20 (40%) dogs at postmortem examination. No association was found between a dog being vaccinated and the prevalence of thyroiditis at postmortem examination. However, the power of the study to detect such an association was low because of the unexpected high prevalence of thyroiditis in the unvaccinated control dogs. Thyroid function tests were abnormal in 2 of 8 dogs with thyroiditis but were normal in all dogs without thyroiditis. CONCLUSIONS/SIGNIFICANCE: There was no evidence to support an association between routine vaccination and thyroiditis at postmortem examination in beagle dogs after repeated vaccination.

Prevalence of autoantibodies to thyroglobulin in dogs with nonthyroidal illness.

OBJECTIVE: To evaluate a thyroglobulin autoantibody (TgAA) assay and determine a diagnostic threshold. SAMPLE POPULATION: Serum samples from dogs with various endocrine abnormalities and from 30 obese adult female Beagles. PROCEDURE: TgAA were determined by use of the ELISA. Six experiments were done: 1, definition of positive results for TgAA using samples from normal and T3 autoantibody (T3AA) positive dogs; 2, establishment of prevalence of positive results in 91 clinically normal dogs; 3, evaluation of positive results for sera from dogs with nonthyroidal illnesses; 4, testing of samples from dogs with primary hypothyroidism but absence of T4AA or T3AA, or both; 5, determination of prevalence of false-negative results in dogs that are T4AA and/or T3AA positive, which were (18 dogs) or were not (22 dogs) receiving L-thyroxine replacement therapy; and 6, examination of thyroid biopsy specimens from 18 dogs (8 TgAA positive and 10 TgAA negative). RESULTS: Positive results were defined as at least twice (200%) the optical density of the negative-control sample. False-positive results were obtained for only 3.4% of 146 dogs with nonthyroidal illness. Thirty-seven percent of dogs with primary hypothyroidism, but no evidence of T4AA or T3AA, or both, were TgAA positive. False-negative results were found in 1 of 22 and 2 of 18 T3AA-positive dogs with and without thyroid replacement therapy, respectively. Thyroid biopsy specimens from 8 TgAA-positive dogs had evidence of lymphocytic thyroiditis, whereas those from 10 TgAA-negative dogs did not. CONCLUSION AND CLINICAL RELEVANCE: The assay is sensitive and specific for identification of lymphocytic autoimmune thyroiditis in dogs, and has potential for aiding early diagnosis of thyroiditis in dogs and identifying dogs likely to perpetuate hypothyroidism in breeding programs.

Multisystemic inflammatory disease in a borzoi dog.

A six-week-old female borzoi puppy from a brother-sister mating developed a generalised illness characterised by anorexia, temporary intention tremor, episodic pyrexia, tachypnoea, conjunctivitis, otitis and neck pain. Haematological abnormalities included an inflammatory leukogram and regenerative anaemia. Blood cultures remained sterile; clinical chemistry values were unremarkable. The puppy had recurrent seizures and was euthanased when 18 weeks old. Post mortem examination revealed a multisystemic inflammatory disease involving thyroids, lymph nodes, spleen, pancreas, bladder and lung, but no lesions to account for the neurological signs. The cause of this generalised disease was not recognised. The histological features are unusual and resemble those described in other dogs of this breed.

Effects of testosterone on the development of autoimmune thyroiditis in two strains of chicken.

The effect of testosterone on organ-specific spontaneous autoimmune thyroiditis (SAT) was examined in two strains of chicken: the Obese (OS) strain, which develops SAT at several weeks of age and the control Special C (Sp. C) strain. Both were originally selected from the C strain and are homozygous for the B13 major histocompatibility haplotype. Testes development and testosterone levels in the OS strain were considerably less than those found in comparably aged birds of the Sp. C strain. Testosterone supplementation of the OS strain significantly decreased thyroid infiltration by lymphocytes while castration of the Sp. C strain significantly enhanced infiltration. These results suggest that testosterone reduces SAT and that the hormonal constitution in both strains of chicken affect the frequency of occurrence and severity of this disorder.

Experimental thyroid autoimmunity in the dog.

Thyroid autoimmunity was induced in 6 crossbred dogs by a single injection of thyroid extract in complete Freund's adjuvant alone, or followed by reimmunization with thyroid extract and incomplete Freund's adjuvant or peanut oil. Total thyroxine levels, autoantibodies to thyroglobulin and thyroid microsomal antigen and thyroid histopathological changes were sequentially monitored for up to 150 days. All dogs developed fluxuating levels of thyroid autoantibodies detectable by enzyme-linked immunosorbent-assay (ELISA). Histopathological damage was observed in one or more thyroid gland biopsies in 4 of the dogs, in 3 cases the lesions were of lymphocytic thyroiditis, in the fourth dog the lesion was a granulomatous reaction. Histopathological thyroid damage was observed in biopsies taken during periods of maximal autoantibody titer. Fixed immunoglobulin was not demonstrable in thyroid gland biopsies by direct immunofluorescence. In 5 dogs total thyroxine levels fell to below the normal range at some period during the study. However in only one dog did this correlate with a time when biopsy findings revealed histopathological thyroid damage. High levels of thyroid autoantibody may indicate histopathological thyroid damage in dogs, however lower levels of thyroid antibody may be found without evidence of histological damage or alteration in thyroid function.

A survey of the pathology of marmosets (Callithrix jacchus) under experiment.

A survey of the pathology of 567 laboratory-bred cotton-eared marmosets (Callithrix jacchus) is presented. There were few significant pathological changes in animals used in studies up to 6 months in duration, suggesting that the marmoset can be a useful non-human primate species for routine toxicology. The most common pathological changes encountered were chronic colitis, chronic thyroiditis and interstitial mononuclear infiltration in the kidney. No internal parasites were encountered, nor were any viral or bacterial diseases identified. Fungal disease was confined to a few cases of oesophageal mycoses. In a long term study a variety of pathological changes have been observed, including a 'wasting' syndrome, not related to skeletal muscle myopathy, with atrophy of the gastrointestinal tract, salivary glands and gonads, haemosiderosis and fatty change in the liver and osteoporosis. It is suggested that these changes may be related to protein deficiency and that the nutritional requirements of the marmoset require further investigation.

Autoimmune lymphocytic thyroiditis in dogs.

Primary diseases of the thyroid gland, especially lymphocytic thyroiditis and idiopathic follicular atrophy, were the most common lesions associated with clinical hypothyroidism in pet dogs. Lymphocytic thyroiditis resembled naturally occurring lymphocytic thyroiditis in the Obese-strain of White Leghorn chickens and Hashimoto's thyroiditis in man. The morphology of the thyroid lesion and frequent occurrence of circulating thyroglobulin autoantibodies suggested that lymphocytic thyroiditis was immune-mediated in pet dogs. Thyroid lesions similar to naturally occurring autoimmune thyroiditis in experimental dogs were induced by a local thyroidal graft-versus-host reaction. The lesions observed in the thyroid lobe which was not injected with immunocompetent cells appeared to develop from the formation of thyroid antibodies in the gland by migrating host lymphocytes. Autoimmune lymphocytic thyroiditis occurred secondary to an unrelated immune response occurring in target tissue.

Lymphocytic thyroiditis in dogs; induction with a local graft-versus-host reaction.

Fifty million allogeneic canine lymphocytes were injected in the left lobe of the thyroid gland of 10 dogs. The left lobe of the gland was surgically removed at 1 and 4 weeks after injection. The intrathyroidal injection of immunocompetent cells resulted in local graft vs host reaction within the thyroid gland. Multifocal infiltration of lymphocytes, plasma cells, and macrophages associated with scattered, isolated, or small groups of degenerated follicular cells were present in the follicular wall and colloid on day 7. Thyroidal lesions at 1 month after injection were characterized by extensive destruction of follicular cells, disseminated foci of mononuclear cell infiltration, and electrondense deposits between follicular cells and the basement membrane. The contralateral (noninjected) lobe of the thyroid gland at 4 weeks after injection was infiltrated by lymphocytes, macrophages, and many plasma cells. The inflammatory lesions were associated with multifocal areas of degeneration of follicular cells and focal electron-dense thickenings of the basement membrane. The noninjected lobe, following hemithyroidectomy at 1 week after injection of the thyroid gland undergoing graft-vs-host reaction, either had a focal infiltration of polymorphonuclear leukocytes, lymphocytes, macrophages, and mast cells or had no significant lesions.

What are Askanazy cells?

Considerable confusion exists over the names that are used in the study of thyroid pathology. In particular is the use of the name Askanazy cell. This is said to occur in Hashimoto's disease and has been described by a variety of names.

Genetic and cellular control of spontaneous autoimmune thyroiditis in OS chickens.

B-locus genotypes have been defined in Obese strain (OS) chickens that spontaneously develop autoimmune thyroiditis (SAT), and in White Leghorn Cornell C strain (CS) chickens from which the OS was selected. The B-locus influences SAT, and some possible mechanisms are discussed. Thymic abnormalities in OS, as contrasted with CB birds, are also discussed and may play a role in SAT, as may an intrinsic defect in the thyroid gland itself.

Spontaneous autoimmune thyroiditis in the BUF rat.

The inbred BUF rat develops autoimmune thyroiditis spontaneously. The incidence is related to the age of the animal and is increased by neonatal thymectomy and by treatment with methylcholanthrene. Autoantibodies to thyroglobulin can be demonstrated by indirect immunofluorescence and hemagglutination, but skin tests are negative. The "spontaneous" autoimmune disease may be due to the conjunction of an unusually vigorous immunological response to thyroglobulin and the loss of thymic suppressor function.

Role of age and sex in chronic thyroiditis in rats fed 3'-methyl-4-dimethylaminoazobenzene.

Inbred male and female Buffalo strain rats were started at 4, 8, 12, 24, or 52 weeks of age on 0.06% 3'-methyl-4-dimethylaminoazobenzene in a low-protein, choline-deficient diet. Eight-week-old males and females were the most susceptible to the development of chronic thyroiditis, but females were more susceptible than the males. Female rats of other ages developed a slightly higher incidence of thyroiditis than the male rats, the difference being most noticeable for rats 12 weeks old.