For Forrest Gump, life was like a box of chocolates. For Mark Parcells, it’s more of a race between virus and vaccine.
Parcells, a molecular virologist at the University of Arkansas, is using a fluorescent protein from jellyfish to detect the virus that causes Marek’s disease in poultry.
Marek’s disease, or MDV, is a herpes virus that — within a mere six weeks — can cause potentially fatal, cancerous tumors in poultry (but is not harmful to humans).
The only herpes virus that causes cancer in animals, MDV infects many chickens, but only 1/10 to 1/100 of a percent of them actually come down with cancer from the disease. That may not sound like many, but with the 8 billion broilers processed for food annually in the United States, that amounts to about 1 million to 8 million birds per year. The diseased birds are pulled from processing facilities and destroyed. Estimated losses because of the disease are about $100 million.
The U.S. poultry industry spends about $80 million per year to vaccinate every chicken egg processed in the country (on the 18th day of incubation) against MDV. The cost, about a penny per egg, is 50 to 100 times more expensive than most poultry vaccines.
But some chickens come down with the disease anyway, either from a “mis-vaccination” or because the disease has mutated and managed to skirt the vaccine, said Parcells, an assistant professor of poultry science.
The result? Chickens that appear to have the flu, frequently shivering and showing signs of neurological problems that appear as paralysis of one leg or as if the chicken is leaning forward and holding its wings as far as possible behind it.
“It’s the spookiest thing,” Parcells said of the behavior of diseased birds. “It’s the most prevalent cancer in the animal kingdom.”
MDV spreads when chickens inhale skin sloughed off by an infected bird. In this country, many growers clean out chicken houses only once or twice a year, meaning birds are growing in an environment “that challenges them with the virus,” Parcells said.
In Europe, growers have started cleaning out chicken houses after every batch of broilers is taken to market, and the disease has been drastically reduced, Parcells said. In England, many growers don’t even vaccinate eggs against MDV disease anymore.
Since broilers are only grown for about six and a half weeks before they’re processed, the virus has had to speed up to have any effect before the birds are killed and wind up on grocery store shelves.
“What we’re seeing is a massive pressure on the virus to maintain itself in a population that lives for only six weeks,” Parcells said. “It’s like a big, blooming pot of evolution if you look at it.”
Jellyfish use “bioluminescence” to attract food or for the purpose of mating.
Parcells and his research team take the a gene from the DNA of jellyfish protein and splice it into poultry cells infected with MDV. The result is that cancerous cells glow bright green when replicating themselves.
“So we now have a tool for studying how, during infection, the virus reactivates and infects different tissues,” he said.