Researching a vaccine for dysentery

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BY JESSICA ADDINGTON

A cure for one of the oldest and deadliest diseases known to man, dysentery, is under research at SDSU. Dr. Weiping Zhang is currently working on a vaccine to cure dysentery infection in both pigs and humans.

“Agricultural-based universities like SDSU are better suited to study human diseases because experiments are first performed on animals that are similar to the human genome before human trials can begin,” Zhang said.

There are two main types of dysentery causing bacteria: Enterotoxigenic Escherichia coli (ETEC) and shigella. ETEC claims far more victims than shigella, especially in children under the age of five. The World Health Organization conservatively estimates about 100 million people contract dysentery every year and about 100,000 of these cases result in death.

Zhang’s goal is to cure both human dysentery (ETEC and shigella) and swine dysentery (Brachyspira hyodysenteriae). This is why both the National Institute on Health and the USDA are funding him. Other universities are also doing research with dysentery including John Hopkins University and Oklahoma State University.

The first symptoms of dysentery are diarrhea and pneumonia. Dysentery is caused by certain pathogens found in contaminated water and food. This disease is mostly seen in developing countries where water and food supplies are easily contaminated. Proper nutrition is hard to find and waste and fecal matter aren’t disposed of in a safe way.

Dysentery can be treated if it is caught early and the victim is hospitalized and put on Intravenous therapy, but in most developing countries there is little or no medical help available. The mortality rate is much higher worldwide than it is in the United States.

Many organizations are funding research to find a vaccine to dysentery. Some organizations and foundations that are funding Zhang’s research are the Bill and Melinda Gates Foundation, the US Department of Agriculture, the Department of Health and Human Services and the National Institute of Health.

When experiments come to mind, just about everyone thinks of mice in cages. But there are several reasons why mice aren’t suitable for studying human diseases. According to Zhang, mice are easier to acquire and cheaper than other animals, but they are almost always used to test immune responses to certain diseases.

“Pigs are the best models for human disease studies because their immune system, organs, proteins and genome are almost exactly like humans. Swine are susceptible to diarrhea and closer to humans than mice or rabbits.”

A scientist may be able to produce more test results and data with mice, but that information would not help as much, since mouse genomes have too many differences from the human genome. The most important reason Zhang isn’t using mice is that mice don’t develop diarrhea; therefore they are no help to his dysentery research.

With the grant money and research, Zhang is almost ready for human trials. His vaccine will be tested on volunteers in developing countries such as Bangladesh and Africa.