vCJD Continues to Baffle Scientists; Teenagers Susceptible

That young people tend to eat more beef products is not enough to explain the strikingly high proportion of new variant Creutzfeldt-Jacob (vCJD) disease cases among children and adolescents. An article published this week in BMC Infectious Diseases, shows that young people must also be more susceptible to vCJD infection because of their age.

New detailed estimates of the UK populations dietary exposure to bovine material according to age have recently become available. Pierre-Yves Boëlle and his colleagues from Assistance Publique Hôpitaux de Paris and Université Joseph Fourier, Grenoble plugged this information into a mathematical model that predicts the age distribution of vCJD cases.

We found that exposure alone could not explain the young age of vCJD cases as seen in the UK, said Boëlle. An additional effect of age-dependent susceptibility was required to fully account for the age of the vCJD cases.

If the researchers considered exposure to beef products as the only risk factor, the predicted age distribution did not fit well with the actual age distribution of the 137 reported cases. This model predicted that 48 percent of those with vCJD are over 40, whereas in reality only 10 percent of people affected by the disease fall into this age group.

The predicted distribution of cases was much closer to the actual age distribution if the researchers considered both exposure and an age-dependent susceptibility to the disease as risk factors. The susceptibility to vCJD was predicted to increase during childhood, peak during adolescence and decrease sharply afterwards.

With this model, 12 percent of cases were estimated to be in people over 40, and the predicted ages of people with the disease showed good agreement with the actual distribution of cases.

The researchers suggest that, one possible explanation for the difference in susceptibility could be that the permeability of the intestinal barrier changes with age, as the number of Peyers patches decrease. However, they stress that further research is needed, as this is a very unusual characteristic of an infectious disease.

Source: BMC Infectious Diseases and BioMed Central Limited