CANADIAN MANCHESTER TERRIER CLUB HEALTH SURVEY: THYROID
In total 44 individuals returned surveys. Information was reported for a total of 312 Manchester Terriers, of which 37 (approximately12% of the sample) were reported to have a thyroid condition. It should be noted that the raw number of dogs reported to have a thyroid condition for the current survey is similar to that found for the 2002 CMTC/AMTC General Health Survey. The general survey indicated 32 Manchester Terriers suffered from thyroid disease in the period from 1990-2002. Although this only represented 3% of the total number of dogs included in the general survey, it is likely that as a result of the specific nature of the current survey, individuals who's animal did not/does not have a thyroid condition may not have been inclined to complete the current thyroid survey. At this stage, there is no indication that the prevalence of this condition in the Manchester Terrier population has increased since the 2002 survey.
The previous survey did not include information relating thyroid conditions to either variety or sex. This information was collected in the current survey and is displayed in Table 1. The rate of reported thyroid conditions was very similar in the two varieties, with 12% of TMTs and 11% of SMTs in the current sample suffering from some form of the disorder. There was a bit more disparity between males and females. A total of 21 males, representing 16% of the males in the sample had a thyroid condition, whereas only 16 females or 9% of the females in the sample had a thyroid condition. The average age of diagnosis was 4.8 years. Age of diagnosis varied from 1 year to 12 years of age.
Table 1: Prevalence of Thyroid Disease
Variety/Sex Number
Number with Thyroid Disorder
. . . TMT male 85
15
TMT female 113
9
SMT male 45
6
SMT female 69
7
For those animals with a thyroid condition, respondents were asked to indicate if the animal had been spayed/neutered and the age at which the procedure was done. Information was provided for 34 animals. Twenty-one animals (approximately 62% of those with a thyroid condition for whom data was available) had been spayed or neutered. The average age of the spay/neuter was 2.9 years, with a range from 3 months to 10 years. A majority of the altered animals (18 individuals) were diagnosed with a thyroid condition after they were spayed or neutered, on average 2 years after the operation. It should be noted that desexing is not necessarily a causal factor in the development or onset of thyroid disease.
The responses regarding testing method are displayed in Table 2. The most common testing method for diagnosing a thyroid condition was measuring T3 & T4 levels, however, as can been seen in the table, approximately 28% of the respondents indicated they did not know which test had been used to diagnose their Manchester Terrier.
Table 2: Testing/Diagnosis Method
Method Frequency
Percent
. . . T3Levels 1
2.8
T4 Levels 6
16.7
T3 &T4 Levels 13
36.1
cTSH 1
2.8
TGAA 0
0
Circulating T3AA & T4AA 0
0
Thyroid Antibody DST Profile 5
13.9
Unknown 10
27.8
For the majority of animals with a reported thyroid disorder (21 animals, 58%), the survey respondent indicated they did not know what the exact diagnosis was. Of those that did indicate a specific diagnose, 11 indicated it was autoimmune thyroiditis (primary thyroiditis), 1 indicated a deficiency of TSH (secondary thyroiditis) and 3 indicated a deficiency of TRH (tertiary thyroiditis). No individuals indicated their Manchester Terrier was diagnosed with Hyperthyroidism (the body producing excess thyroid hormones).
In terms of severity of the disorder, 8 individuals (22%) reported not knowing the severity of the diagnosis. Five individuals (14%) indicated their animal was diagnosed with “very low thyroid level”. A majority of individuals (15 individuals, 42%), however, reported “low thyroid levels” and 7 others (20%) reported “low-normal thyroid level”. A single individual reported “very high thyroid level”, however, given that this individual indicated a specific hypothyroid diagnosis in the previous question, it is likely that this is an error. Given these data, it would seem that most Manchester Terriers with thyroid disorders (56%) are not severely affected. Analyses were conducted to examine if reported severity of the condition was related to either sex or variety. It should be noted, that because of the small number of respondents these analyses can only be interpreted as suggestive. None-the-less, separate analyses of variance indicate significant differences in reported severity with males and Toy Manchester Terriers exhibiting more severe cases (i.e. lower thyroid levels). It should be noted, that although there are differences between the varieties in terms of reported severity of the disorder, toys and standards appear to be equally likely to suffer from thyroid disease.
Most animals (56%) were medicated with Soloxine. Only 4 animals (11%) were medicated with Synthroid, and the remaining 12 animals (33%) were reported to receive some other (unidentified) form of medication.
Respondents were asked to report on various behavioural attributes that have been suggested in previous literature to be associated with thyroid disorders. A vast majority of animals (69%) were reported to exhibit no aggressive behaviours towards other dogs. Ten animals (28%) were reported as displaying dog aggression, and one respondent indicated they did not know if their animal was dog aggressive. The pattern was very similar for aggression towards humans. Again the majority of Manchester Terriers (25 individuals, 69%) showed no aggression towards humans, while 11 individuals (31%) had shown aggression towards humans. Of the 12 individuals who responded to this item, for 10 of the dogs the onset of aggressive behaviour was described as “sudden” and only 2 were described as showing a “gradual” onset of aggressive behaviour. The average age for the onset of aggressive behaviours (in these 12 individuals) was 2.7 years and ranged from 4 months to 10 years of age. Respondents were asked to indicate if their animals suffered from a variety of minor symptoms prior to displaying aggression. Two individuals were reported as being inattentive, 4 individuals were fearful, 10 had skin or coat problems, and 3 displayed seasonal allergies.
Before being diagnosed with thyroid disease the most common symptom, reported for 25 individuals (69% of the sample) was “dry, scaly skin and dandruff, coarse, dull coat, bilateral symmetrical hair loss, rat tail, puppy coat, hyper-pigmentation, seborrhoea or greasy skin, pyoderma or skin infections, chronic offensive skin odor”. For 8 individuals “lethargy, mental dullness, exercise intolerance, neurological signs, seizures, weight gain, cold intolerance, mood swings, hyper-excitability, stunted growth, chronic infections”. Two individuals were reported as suffering from constipation or infertility prior to diagnosis, and one other was reported as suffering from “weakness, stiffness, paralysis, facial paralysis, tragic expression, knuckling or dragging feet, wasting, head tilt, or drooping eyelids”.
A majority of individuals (22, 61%) indicated they did not know if the parent(s) of their dog had been tested for thyroid disease. Seven individuals (19%) indicated neither parent had been tested for thyroid disease. Only for 4 individuals was it reported that both the sire and dam of the individual had been tested.
Very few respondents responded to the final items regarding testing animals they personally had bred. It is likely that many breeders, who did not complete the previous items because none of their animals suffered from thyroid disease, missed this final section of the survey. The lack of response also indicates that a large proportion of the respondents to this survey were primarily pet owners. Of the individuals who responded to the final items, 3 indicated they did not thyroid test their animals, while the remaining 10 indicated they always or sometimes tested for the disorders before breeding. However, 75% of those who responded (9 out of 12) indicated they did not require the owner of other dogs to be tested before breeding to them. Five individuals indicated they had never produced a pup who developed thyroid disease, while 6 indicated they had. Data from 10 individual litters were reported. Of these 4 “thyroid litters” came from parents who had both tested clear of thyroid disease, while 3 involved at least one parent with a thyroid condition.
Conclusions
In spite of the relatively low number of animals reported on in the current survey, several trends can be noted. First, the evidence suggests that thyroid disease is equally prevalent in both Manchester Terrier varieties. However, there is some suggestion that the disorder maybe more severe in Toy Manchester Terriers. Second, the results of the current study suggest the disorder might be more common in males than females, and again there may be a trend for the disorder to be more severe in males than in females. Third, the majority of animals did not exhibit aggression or other behavioural problems prior to their diagnosis. Finally, the most common symptom(s) displayed before diagnosis were related to poor skin or coat conditions.