Mad cow disease has been found in a dairy cow on a farm in the Lower Mainland city of Delta, the Canadian Food Inspection Agency confirmed on Wednesday.

The agency said it has the carcass of the 5½-year-old cow and no part of it entered the human food or animal feed systems.

It said the animal's age, combined with the average incubation period of bovine spongiform encephalopathy (BSE), indicates the cow was exposed to a very small amount of infected material, likely during its first year of life.

The agency is now tracing other animals from the same herd and trying to determine how the cow became infected.

In April 2006, another B.C. dairy cow was found to have mad cow disease, which the food inspection agency said was caused by contaminated feed.

The latest case was detected on a farm by a national surveillance program that targets cattle most at risk, the agency said. About 160,000 animals have been tested since 2003.

Although a ban on feed that may contain animal products takes effect in Canada on July 12, the Food Inspection Agency said it still expects to find a small number of BSE cases over the next 10 years as it works toward eliminating the disease.

Former B.C. Cattleman's Association president Mark Nairn told CBC News he doubts the latest case will affect exports of beef, as  many countries still have import bans on older Canadian cattle that were put in place after the first outbreak in 2003.