Hello, my name is Dr. Kara and I have over 20 years of experience as a veterinarian. I am very sorry to hear about Alfie's abnormal behavior of eating dirt in the garden. The behavior that you are seeing is called "pica" and that just means eating non-food items.
Do his gums and tongue look very pale in color?
In some cases pica is a sign of anemia or a decreased amount of red blood cells. In those cases we will see pale gums and tongue.
But it can also indicate primary intestinal disease, diabetes, hyperadrenocorticism (overactive adrenal gland) or hypoadrenocortisim (poorly functioning adrenal gland)or metabolic organ disease. In some cases it can also indicate developing cancer or senility.
Has Alfie had any blood tests done or a urinalysis checked to look for underlying disease?
Is he losing weight?
At this point I think diagnostic testing needs to be done if it hasn't already been done. I highly recommend checking a complete blood count, biochemistry profile, a thyroid profile and a urinalysis to start.
If those things look normal then another recommended test would be an abdominal ultrasound. This allows us to evaluate his abdominal organ architecture, vasculature, and abdominal lymph nodes. We can collect aspirates and biopsies of any organs that look abnormal which will give us a more definitive diagnosis and thus a better treatment plan as it is a focused plan based upon his particular problem.
If all of his tests come back normal and he is displaying other odd behavior then medication to help brain function, such as Denamarin and Anipryl (l-selegilene) can be tried.
Best of luck with Alfie, please let me know if you have any further questions.