Abstract:
Lymphoma is a common haematopoietic neoplasm in dogs. Several breeds have been shown
to have a predisposition to lymphoma; however, very little information exists regarding the
South African dog population. This study assessed whether any breed had increased odds of
developing lymphoma compared with others, and also investigated the effects of age, sex and
neutering status on disease prevalence. Two study populations and their corresponding
reference populations were studied retrospectively. Odds ratios (ORs) for lymphoma in 49 dog
breeds, together with their 95% confidence intervals (CI), were calculated. Age effect was
assessed by calculating ORs for different age categories in one of the populations. The chisquare
test was used to evaluate differences in the prevalence of the various sex and neutering
categories in one lymphoma population compared with its reference population. Fourteen
breeds had significantly increased odds of developing lymphoma, and one breed had
significantly decreased odds (p < 0.050). The median ages of the two lymphoma populations
were 6.5 and 8.0 years, with the 6.1–9.0 year category having significantly increased odds of
developing lymphoma (OR 1.61, CI 1.2–2.16, p = 0.002). In one of the lymphoma populations,
higher proportions of males (p = 0.033) and neutered females (p = 0.006) were found when
compared with the reference population. These findings suggest that certain breeds in South
Africa have a higher risk of developing lymphoma, and that sex hormones may play a role in
lymphoma pathogenesis. The findings may provide useful information for pet owners and
veterinarians.
