An epidemiological analysis of factors influencing the increase in Taenia ovis prevalence during the New Zealand Echinococcus granulosus control program.

There was an 8-fold increase in the national prevalence of Taenia ovis in dogs during the first decade of the New Zealand hydatid disease control program. The temporal patterns in the prevalence of T. ovis were similar in both rural working dogs and urban pet dogs, with the highest prevalence found in the sheep farming areas. The dramatic increase in the prevalence of T. ovis was a reflection of the change in source of food for many working dogs, from the traditional raw viscera to carcase meat of sheep, a change necessitated by hydatid disease control. Other factors influencing the rise in prevalence of T. ovis in rural dogs were investigated using stepwise multiple regression techniques. The results of the regression analyses suggested that the rate of increase in the prevalence of T. ovis was influenced by 4 major factors: Taenia hydatigena variables (initial prevalence and rate of progress in control), an ethnic variable (Maori proportion in local population), canine variables (numbers of dogs per farm and per owner), and animal husbandry variables (pasture type, sheep density and numbers of sheep per farm). The results were discussed in the light of present knowledge of the epidemiology and immunology of the taeniid cestodes.