LONDON: The human form of mad cow disease, called variant Creutzfeldt-Jakob disease, or vCJD, has an incubation period of as many as 50 years, according to latest research findings.
Researchers in the U.K., who carried out studies on a disease specific to Papua New Guinea, caused by prions, which are similar to those responsible for the bovine spongiform encephalopathy, or mad cow disease, say that people could be infected with vCJD, the human form of the disease, for 50 years without developing the illness. To this extent, the potential of the epidemic could be underestimated, they wrote in the medical journal Lancet.
Some 160 people have so far been diagnosed with vCJD in the U.K, while instances of the fatal disease have also been reported in France, Italy, Ireland, the Netherlands, Canada, Japan and the United States.
Scientists had originally thought the incubation period could be up to 20 years. But, John Collinge of the University College and his team, which carried out the latest studies believe it could be longer and as such the epidemic that may happen could be bigger.
Collinge and his team had studied kuru, the disease caused by a mutated prion related to cannibalism that reached epidemic proportions in Papua New Guinea where cannibalism had been in vogue till the 1950s as a ritual. They identified 11 patients with kuru and found that the estimated incubation periods for the prion causing kuru were as long as 56 years.
They now suspect the incubation period for vCJD-causing prion could be longer because the infection is transmitted between species -- from cows to humans. Collinge says the people so far identified with vCJD could be a distinct genetic subpopulation with unusually short incubation periods for the prion.
The Lancet wrote an editorial saying, "Any belief that vCJD incidence has peaked and that we are through the worst of this sinister disease must now be treated with extreme skepticism."
Bovine spongiform encephalopathy is caused in cattle by prions, which are misfolded brain proteins, and contracted through contaminated feed. The first case was found in the U.K. in 1986. Humans can catch the vCJD, by eating contaminated beef.
