14 Jan 2022
Alex Gough looks at some of the companion animal research released of late in this Research Review column in Vet Times.
Alex Gough
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Image: goodluz / Adobe Stock
A large volume of information is available on the internet and other media regarding diets for pets, but much of it is not evidence-based, or is known to be detrimental.
Veterinarians will often recommend to owners a change of their pets’ diet, to prevent future health problems or to help manage an existing problem. Some owners may be resistant to dietary advice from vets, however, for reasons of cost, convenience or belief in the benefit of an existing diet.
Alvarez and Shultz1 performed an investigation into the effect of statements made by vets on owners’ decision-making regarding their pet’s diet. The owners of dogs and cats presenting for wellness appointments at a veterinary medical teaching hospital or a low-cost community clinic were included in the study. In total, 84 dog owners and 36 cat owners completed a survey.
Part one of the survey – relating to signalment and current diet, including owner satisfaction with the diet – was completed by the owners of the pets after a vet student examined the pet and obtained a history. After the appointment, the owners completed a second part, which included owner demographics and questions on the level of agreement of the owners with statements that could be made about their pet’s diet.
Statements regarding the pet’s health was the most effective way of getting an owner to change their mind about diet. Statements based on the vet’s personal preferences were least effective. In total, 93% of owners were at least somewhat willing to change their pet’s diet based on the advice of a vet.
Cutaneous spindle cell squamous cell carcinoma (SCSCC) is an unusual form of squamous cell carcinoma. Rodriguez Guisada et al2 reported a study of cutaneous SCSCC in 18 cats. The cats had an average age of 11.8 years and all the tumours were found on the face, with 72% on the pinnae.
Changes indicative of actinic keratosis and the dorsal location of the tumours suggested a role of sunlight exposure in the pathogenesis of the tumours. No evidence existed of papillomavirus infection.
Cases were followed up for between 7 and 25 months – 78% had no recurrence; 1 case had regional lymph node metastasis. Cutaneous location, mitotic count and presence of clean surgical margins were associated with prognosis.
Myasthenia gravis is an uncommon, but often devastasting autoimmune disease affecting the neuromuscular junction. Immune-mediated damage to the acetyl choline receptors causes signs of muscular weakness, which can be focal or generalised.
Forgash et al3 performed a retrospective study to assess whether age and the presence of neoplasia were associated with prognosis and remission.
A total of 94 dogs diagnosed by acetylcholine receptor antibody testing were included in the study. Immunological remission was defined as a return of the acetycholine receptor antibody level to less than 0.6nmol/L.
In total, 96% of cases were treated with an anticholinesterase drug, and in 67% of cases this was the sole treatment. Immune modulators were also used.
A total of 31% of dogs achieved clinical remission – that is, no clinical signs four or more weeks after ceasing treatment; 15% showed a lack of clinical signs while on treatment and an improvement in clinical signs while on treatment was seen in 26%t. No improvement was seen in 29% of dogs.
In total, 59% of dogs tested showed immunological remission. Clinical remission was found to be less likely in older dogs, and dogs presenting with regurgitation and high initial acetylcholine receptor antibody concentration. Younger age and comorbid endocrine disease were associated with a greater chance of remission.
Angiotensin-converting enzyme inhibitors (ACEis) are proven to be effective treatments for congestive heart failure, but evidence for the optimum dosing strategy is lacking.
Ward et al4 performed a retrospective study to test the hypothesis that in dogs with cardiac disease, a dose-response relationship exists for long-term outcome. A total of 144 dogs with cardiac disease were included in the study – 63 that were currently suffering from or had previously had congestive heart failure; 75% of dogs received twice-daily dosing.
Renal function, blood pressure and electrolyte levels were not affected to a clinically relevant level between the first prescription of ACEi and the first re-evaluation, which was on average 14 days later.
In multivariable analysis, twice-daily dosing was associated with a better two-year survival, as was higher serum potassium concentration at the first visit. Only 5.6% of dogs decreased ACEi dose or discontinued treatment because of adverse effects.
The authors concluded that ACEis are well tolerated and twice-daily dosing may optimise their beneficial cardiac effects.
Measurement of serum creatinine has long been the standard method of assessing kidney function in dogs and cats, but its sensitivity to small changes is limited. More recently, symmetrical dimethylarginine (SDMA) has become increasingly used as a way to detect earlier or more subtle changes in renal function.
Two recent studies by the same group examine the performance of creatinine and SDMA as kidney biomarkers in dogs and cats.
Michael et al5 performed a longitudinal study to look at the persistence of increased creatinine in dogs and cats. Little information exists on how creatinine changes over time after an increase is recorded. This large study looked at the probability of an increase in creatinine persisting, and how creatinine and SDMA behaved where creatinine was persistently increased.
Creatinine and SDMA were measured at baseline and two further time points up to 18 months later. To be included in the study, the baseline creatinine and SDMA had to be within normal limits. For dogs that had an increased creatinine at the second time point, the probability of this increase persisting to the third time point was 49% and for cats this figure was 58%.
For dogs that didn’t have an increased creatinine at the second time point, the probability of an increase at the third time point was 3% for dogs and 7% for cats. In most animals with persistently increased creatinine, a concordant rise in SDMA was seen.
In the second study, Mack et al6 assessed retrospective SDMA data in a large number of cats and dogs. SDMA is a sensitive biomarker of glomerular filtration rate, but the significance of mild elevations is uncertain.
As with the previous study, the data was assessed at three time points, with the baseline SDMA measurement being within normal limits at the first time point and elevated at the second time point.
If SDMA was mildly elevated at the second time point then the probability of it being persistently elevated was 42% for dogs and 53% for cats. For animals with increased SDMA at the second and third time points, creatinine was concurrently increased at the second time point in 18% of dogs and 20% of cats. However, by 24 months this had increased to 55% of dogs and 61% of cats.
For higher values of SDMA at the second time point, creatinine was increased in more than 90% of dogs and cats at 24 months.
The authors concluded that even mild elevations of SDMA can be an early sign of kidney disease, and higher levels of SDMA are associated with a higher chance of long-term persistently elevated SDMA and creatinine.
It is well understood that the accuracy of clinical tests are affected by analytical factors, such as the performance of a laboratory machine compared to the true value of the measurement.
However, pre-analytical factors also cause clinical measurements to vary. These can be patient factors such as exercise, diet and stress prior to the act of measurement, which can cause the measured value to move away from the true mean.
Other pre-analytical factors affecting the result include measurement technique and storage conditions.
Giraldi et al7 examined how pre-analytical factors affect the results of measurements of feline urine protein. Specifically, the effect of cat litter and storage conditions on urine protein creatinine ratio (UPC) was measured.
A total of 22 urine specimens were placed in contact with cat litter for an hour, then the supernatant was collected and creatinine was measured at various dilutions, and various storage times and temperatures.
Cat litter exposure did not affect the UPC. UPC ratios were also stable after four freeze-thaw cycles and at storage temperatures above freezing. However, UPC levels were decreased compared to baseline at 8 and 12 weeks of storage at -20°C. Higher levels of dilution also altered the UPC ratio. None of the changes appeared to be clinically important, however.
The authors concluded that UPC does not appear to be clinically affected by exposure to cat litter, various storage temperatures or dilutions, but that further research is needed to examine other potential variables.
