History repeats itself, and so do epidemics. Yet, over time we have become better prepared to handle epidemics.
Before the holidays, when one Holstein cow in Washington State tested positive for mad cow disease, an epidemic had occurred. Yes, just one case of mad cow disease is an epidemic – and rightly so – because of the tremendous public health risks from this disease.
We need to reflect back 20 years to Britain’s initial grudging response to mad cow disease to realize its devastating consequences. We can also define the full medical name of mad cow to recognize its seriousness: bovine (involving cattle) spongiform (brain tissue having holes like a sponge) encephalopathy (infection of the brain), BSE.
In 1985 a country veterinarian in southern England examined cattle with strange symptoms. The cow had head tremors and incoordination. The disease resembled the sheep disease scrapie, well known for a 100 years. Yet no humans were ill, and the British agriculture minister reassured the world that British beef was safe. He even demonstrated by having his 4 year old daughter eat a hamburger on national television. By 1993 mad cow disease peaked to 100,000 confirmed cases in cattle.
Ten years after the initial cases of mad cow disease, humans started falling ill. Initially the victims were thought to have depression, yet later they developed twitching and symptoms similar to Parkinson’s disease. Ultimately they died within 14 months. This happened to young otherwise healthy adults.
The illness was named as vCJD or variant Creutzfeldt-Jakob disease. Scientists now believe that when people eat the infected meat of cattle with mad cow disease, they contract vCJD. vCJD manifests symptoms of dementia a decade late and subsequently leads to death.
The symptoms of vCJD also resembled a disease known to doctors as kuru which was only seen among a tribe of people in the Highlands of Papua New Guinea. Epidemiologists found that the disease was being spread by a strange tribal custom of people eating the brains of dead relatives not knowing they were infected. Once the practice of cannibalism was stopped the disease disappeared.
Kuru, mad cow (BSE) and vCJD are cousins belonging to the same family of diseases. They are caused by prions. Prions are not parasites, fungi, bacteria, or viruses (the fundamental four infectious agents), but they are a new class of agents. Prions are free floating and replicating proteins. Almost like a loose weapon, the prions attack cells yet they have a special appetite for brain and nerve cells, resulting in gradual neurological decline.
In United Kingdom 177,500 cases of mad-cow disease were reported by 2000, with 88 cases of vCJD. British beef was banned for years.
The likely source of the BSE among cattle was from the sheep scrapie. Meats from infected sheep were fed to cows as feed. Ultimately it resulted in BSE. Infected beef when eaten by humans results in vCJD. Such are the footprints of a species jumping prion.
Having learned their lesson the hard way the British meat industry went through a drastic reform. Under new laws cattle were no longer fed animal remains and a constant vigilance for any new disease symptoms were galvanized in the minds of veterinarians and doctors.
Often at casual conversations I am asked if the media is hyping the lone case of mad-cow disease. I respond, “It is not media hype but history which has taught us. This one case of mad cow disease may be an isolated incident or it may be a tip of an iceberg with hundreds of infected cows yet to be discovered. We hope it is just an isolated incident.