The prevalence in cats is around 7.4 per 1000 (Lederer et al. 2007).
All cats are susceptible to diabetes but it is usually seen in middle aged to older cats. A higher incidence is seen in neutered male cats.
An increased incidence of diabetes mellitus has been noted in Burmese cats in Australia and the UK (McCann et al. 2007, Rand et al. 1997). The prevalence of diabetes in Burmese cats in Australia is 22.6 per 1000 cats, significantly higher than in the general population (Lederer et al. 2007). This may be related to abnormalities in triglyceride metabolism in Australian Burmese cats (Kluger et al. 2008).
References
Kluger EK, Hardman C, Govendir M, Baral RM, Sullivan DR, Snow D, Malik R. (2008) Triglyceride response following an oral fat tolerance test in Burmese cats, other pedigree cats and domestic crossbred cats. Feline Med Surg Jul 28. [Epub ahead of print]
Lederer R, Rand JS, Jonsson NN, Hughes IP, Morton JM. (2007) Frequency of feline diabetes mellitus and breed predisposition in domestic cats in Australia. Vet J Dec 20. [Epub ahead of print]
McCann TM, Simpson KE, Shaw DJ, Butt JA, Gunn-Moore DA. Feline diabetes mellitus in the UK: the prevalence within an insured cat population and a questionnaire-based putative risk factor analysis. J Feline Med Surg 9(4):289-299.
Panciera DL, Thomas CB, Eicker SW, Atkins CE. (1990) Epizootiologic patterns of diabetes mellitus in cats: 333 cases (1980-1986). J Am Vet Med Assoc 197(11):1504-1508.
Rand JS, Bobbermien LM, Hendrikz JK, Copland M. (1997) Over representation of Burmese cats with diabetes mellitus. Aust Vet J 75(6):402-405.

Estimates of the incidence of diabetes mellitus in dogs and cats range from 1 : 100 to 1: 500 (Panciera et al. 1990).