How is CJD transmitted?
CJD is not an airborne disease, nor can it be transmitted through touching or casual contact. This means that close family of sporadic CJD patients at no more risk of infection than the rest of the general population.
Infection has been passed in some cases by various transplant operations such as dura mater grafts (the tissue covering the brain) or a cornea transplant. In other cases the use of insufficiently sterilised electrodes in the brain have caused infection, while there is also a risk of infection through the use of pituitary growth hormone which has been created from the pituitary glands of cadavers. When infection is linked to a medical procedure, doctors refer to the case as an iatrogenic case.
When, in Great Britain and France, the new variant CJD (vCJD or nvCJD) appeared in patients under the average age for the disease, there was concern that by consuming beef contaminated with the disease, BSE could be passed to humans. While tests do show that there is a strong similarity in the prions which cause both BSE and vCJD there is in fact no proof that this theory is correct.
There are concerns that CJD may be transmittable through blood or plasma. Some animal studies do suggest that the blood of an infected animal may be capable of transmitting the disease, however this trend has not been shown in humans. It is argued that if there are in fact infectious agents contained within blood or plasma, their concentration will be very low. However, as scientists do not know the amount of infectious prions an individual must have before developing CJD, it is difficult to know how potentially infectious these fluids are. Despite this uncertainty, it is important to note that millions of people receive bloody transfusions every year, and there have not been any reported incidences of CJD infection through this process.
Although there is no evidence to support the theory that blood from sporadic CJD patients could be infectious, scientific study has shown that infectious prions from both vCJD and BSE may build up in the spleen, the lymph nodes and the tonsils. These studies may therefore suggest that a blood transfusion from a vCJD patient may be capable of transmitting the disease.
Can cow’s milk carry CJD?
There has never been an instance of detectable infection of cow’s milk. The milk of cow’s infected with BSE has been assessed with no positive result for infectious prions. Both milk and milk products are therefore considered safe for consumption.