Tracking cholera in a drop of blood

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Dhaka, Mar 15, 2019 (BSS) – Bangladeshi researchers and US collaborators have jointly developed a method to use blood samples to identify individuals recently infected with cholera aiming to improve cholera surveillance.

Six blood serum markers identified in cholera patients have been shown to confirm recent cholera infection in individuals with 93 percent accuracy, using machine learning methods, according to the study.

It says traditional cholera surveillance is based almost entirely on clinical reporting of watery diarrhea and a few laboratory-confirmed cases. While only a few develop severe symptoms, many do not seek medical care at all and the traditional system does not accurately represent the exact scenario.

Researchers from icddr,b, Johns Hopkins Bloomberg School of Public Health, the University of Utah, Massachusetts General Hospital, Harvard Medical School and Harvard T.H. Chan School of Public Health jointly conducted the study to develop the cholera tracking method.

The research team analysed more than 1,569 blood samples obtained from cholera patients, who received care at the icddr,b Dhaka Hospital, and their uninfected household members between December 2006 and December 2015. The findings of the research were recently published in Science Translational Medicine journal.

“Our work shows that a drop of blood likely contains enough information to tell if someone was infected with the bacteria in the past year,” said Dr Andrew Azman, assistant scientist in Epidemiology at Johns Hopkins Bloomberg School of Public Health and lead author on the study.

“It gives us another way to track cholera without having to fully rely on clinical data from the less than ideal health surveillance systems often available in cholera-affected countries,” he said, reports EurekAltert.

Dr Firdausi Qadri, senior scientist at icddr,b Infectious Diseases Division, said researchers will now be able to predict the exposure status of an endemic population, after studying cholera immune responses for several decades to understand infection, and plan strategies to prevent active or passive disease prevention.

“We are working on simpler sampling methods to further optimise procedures for analysing large populations for antibody responses,” she said, according to an icddr,b webpost.

Appropriately tracking cholera is important since an infected person, even while without symptoms, the bacteria sheds for up to a week after infection, sometimes passing the disease to others, typically through contaminated water.

Dr Daniel Leung, an assistant professor of infectious diseases at University of Utah Health and co-author of the study, said establishing such a serosurveillance method overcomes many of the shortcomings of traditional surveillance approaches.

He said it provides a new way to track the spread of cholera in short-term outbreaks as well as assess long-term burden of cholera across different populations.

A recent study titled ‘Cholera Control and Prevention in Bangladesh: An Evaluation of the Situation and Solutions’ shows there are at least 100,000 cholera cases and about 4,500 deaths each year in Bangladesh alone. More than 66 million people are at risk of cholera with an incidence rate of 1.64 per 1,000.

Bangladesh remains endemic for cholera with a biannual peak in certain areas of the country. Cholera transmission increases during both floods and droughts. Water temperature in ponds and rivers, in addition to rainfall, also has a remote association with cholera transmission.

Despite efforts to improve the availability of safe water and adequate sanitation, cholera continues to kill more than 100,000 people around the world every year. To combat this needless suffering, the World Health Organization’s Global Task Force for Cholera Control set a goal to eliminate cholera as a public health threat by 2030.

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