U. researchers track cholera epidemics using drops of blood

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SALT LAKE CITY — University of Utah researchers, along with a multi-institutional team, have developed an unprecedented method for identifying people infected with cholera.

Significant advancements have been made to increase the availability of safe drinking water and adequate sanitation across the globe, according to a University of Utah press release. Nonetheless, cholera kills more than 100,000 people each year. The World Health Organization Global Task Force for Cholera Control has made it its goal to eliminate the disease as a health threat once and for all by 2030.

A big obstacle to eliminating cholera is that health scientists lack a sufficient method to sort out who has the disease and who doesn’t. Currently, rates of cholera are generally only known through clinical reports of watery diarrhea with a few lab-confirmed cases. Only a small number of people with cholera develop severe symptoms, which leads to many not seeking medical care. As such, they are not counted in traditional surveillance efforts.

Despite a lack of symptoms, a person who has been infected will still shed bacteria for a week after infection, and they sometimes are able to pass the disease onto others.

“Stool is only tested in a very small minority of cases, and that’s really the only way to confirm that it is cholera,” Daniel Leung, M.D., M.Sc., an assistant professor at University of Utah Health and co-author on the study, told KSL.com. “Current public health surveillance relies on a clinical infrastructure and a laboratory confirmation of the bacteria that causes cholera. Unfortunately in many places where cholera occurs that infrastructure is not there.”

New methods to count cases are necessary to adequately assess global health needs for treating the disease. A multi-institutional, international task force including researchers like Leung from the University of Utah was created to develop a better method of identifying cholera-infected individuals.

Leung and his fellow researchers have established a method of using six markers, or antibodies, to identify in the blood of cholera patients. The results are unprecedented, allowing them to achieve an accuracy of 93 percent.

“We can take blood samples from a portion of the population and, from markers in the blood, we can tell how long ago someone had cholera," Leung told KSL.com. "By sampling a proportion of the population we can tell that “X” number of people had cholera in the population in “X” number of days, weeks, or months ago.”

To come to their conclusion, the team studied more than 1,569 blood samples from cholera patients and their infected household members between 2006 and 2015. The patients were all under the care of icddr,b Dhaka Hospital. They double checked the validity of their test by analyzing North Americans who voluntarily agreed to be infected with cholera. The results were very similar.

In order to actually make leaps forward in reducing rates of the disease, Leung explained that they need to be able to track the progress of their intervention strategy. “We really do need to know who has had cholera, where cholera is, and how many people are susceptible to it,” he told KSL.com.

More effective tracking of cholera isn’t the only public health advancement to come from their research. Leung added, “Instead of needing to take blood from people, here at the University of Utah, we’ve developed a method to look at blood markers in dried blood spots,” he said.

Dried blood spots are blood samples taken using a finger prick, where a small amount of blood is put on a piece of filter paper that can be kept for a couple of days or months at a time at room temperature. This will help them better conduct these tests in places that don’t have effective laboratory infrastructure, which tend to also be the places where cholera is common.

Despite the method being a huge step forward, it's limited due to most of its data originating from a region where cholera is common. The results have been validated in non-endemic areas, but only with a small number of patients. Further, they are unable to distinguish between people infected with cholera and those who received a vaccination for it.

Establishing the differences in blood between people who’ve had cholera and those who’ve received the vaccine is one of Leung’s next projects. Once that limitation has been eliminated, he believes their research will be even more useful.

The team’s current project is to validate the method in Haiti. “We got funding from the National Institute of Health to prospectively do this in Haiti to see if the model works there as well,” Leung explained. “We are also building up collaborations with scientists in sub-Saharan Africa.”

The study is available online in the Feb. 20 edition of the journal Science Translational Medicine.


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