Woodchuck

Studies in humans have strongly suggested that people who are chronically infected with the hepatitis B virus are at high risk for developing cancer of the liver. Despite the existence of a vaccine, 250 million people world-wide are carriers of the virus; and, of these, at least 10 percent may eventually succumb to malignant liver disease. But it can take 30 or 40 years for the cancer to develop, and laboratory proof of a link with the hepatitis B virus was lacking.

Woodchucks are now assisting medical researchers in studying the link between hepatitis B virus and human liver cancer. About a decade ago, it was discovered that a strikingly similar virus afflicts half of the woodchucks in the mid-Atlantic states.

In a recent study, it was reported that of 200 woodchucks infected with the virus soon after birth, two-thirds became chronic carriers. More than 60 of these carriers have been followed for three years or more, and almost all of them have gone on to develop severe liver disease and cancer.

In a group of 100 uninfected woodchucks, not a single animal developed liver disease. Medical researchers are now tracing the whole disease process to discover how the hepatitis virus causes liver cells to become cancerous.