October 7, 2008

 

US researchers working on Campylobacter vaccine

University of Arizona researchers are making progress in reducing food-borne illness in humans by developing a vaccine for campylobacter in poultry.

 

Campylobacter jejuni sickens more people than salmonella. Raw chicken is one of the most common carriers of the bacteria.

 

A professor in the University of Arizona department of veterinary science and microbiology, Lynn Jones said Campylobacter is now the number one food-borne pathogen in the United States and the world, surpassing Salmonella. In the US alone, 2.4 million cases are reported annually, with costs exceeding US$1 billion.

 

The most common symptoms of human Campylobacter poisoning include fever, cramps, watery diarrhea and sometimes dysentery.

 

It is estimated that about twenty to eighty percent of all broiler houses are contaminated with Campylobacter.

 

 

The team thinks it has found a new poultry vaccine to Campylobacter jejuni infection in chickens.

 

Scanning electron microscopy shows the string-like adhesion molecule for Campylobacter jejuni on a surface membrane in a laboratory. This simulates what happens when it adheres to the host's intestine.

 

In research trials, the vaccine has significantly reduced the pathogen's ability to colonize young chickens' intestines, where the infection begins.

 

Funded by the USDA, Professor Jones and graduate students started analyzing Campylobacter's infection process about four years ago.

 

The team discovered that the pathogen first attached itself to the surface of the chick's intestines and then began to multiply. Attacking the adhesive mechanism seemed to be the key.

 

The team identified the gene responsible for producing Campylobacter's adherence protein and built a trial vaccine around it using Salmonella bacteria as a vector.

 

The adherence gene is then inserted into Salmonella bacteria, which is nonpathogenic for poultry. The resulting live vaccine, containing Salmonella programmed to make the Campylobacter adhering protein, was fed to young chickens.

 

Professor Jones says once the Salmonella in the vaccine produced the Campylobacter protein, the chicks made antibodies against it in their intestines. In the first study of 15 birds, there was a significant reduction of 98 percent in Campylobacter infection compared to the control. The trial is therefore repeated on a larger scale.

 

The vaccination process is simple, easy to produce and protective to the chick, according to Professor Jones. The Salmonella lives four to five days, enough time to stimulate antibody production, and dies. Chickens need to be vaccinated early as they are infected at just two to three weeks of age.

 

Preliminary figures show that 270 million Campylobacter organisms were present in non-vaccinated birds, compared with just 67,000 in vaccinated ones.

 

At least 500 organisms is needed to produce disease in humans. The chlorine in the packing house chillers usually reduces numbers of bacteria by 1,000 to 100,000 organisms, so the chickens should be free of Campylobacter after processing.

 

The Arizona group was the first to discover the adherence protein, which is only produced when Campylobacter jejuni colonises certain surfaces, like chicken intestine and skin. They have a patent pending in both the US and EU for the gene that produces it.

 

Professor Jones said a commercial vaccine, which would cost a penny per chick, could be ready in three to five years.

 

He added the vaccine would be a great intervention method for Campylobacter when the USDA and FDA mandate reduces numbers of food-borne pathogens in chicken, probably in two to three years.