Before bite-sized crustaceans such as crayfish, shrimp and shrimp land on our plates, they must first become fat themselves – and it turns out they enjoy the freshwater snails that carry the parasite that causes schistosomiasis, the second most common parasite disease worldwide after malaria.
A recent study from the University of California at Berkeley provides a roadmap on how entrepreneurs can capitalize on the insatiable appetite of freshwater prawns on snails to reduce the transmission of these parasites, also known as leeches, while earning profits tasty animals as food.
The study, published in the journal Nature Sustainability shows how the cultivation of small scale freshwater shrimps – also known as aquaculture – could be a win-win situation for communities in emerging areas and developing countries, where bilharzia is common.
"River shrimp are widely used aquaculture products throughout the world, and we know that these organisms are voracious predators of snails that transmit schistosomiasis," said Christopher Hoover of the UC Berkeley Student in the Department of Environmental Health Sciences of the School of Public Health who conducted the study. "What was not clear is whether we can combine the economic benefits of shrimp aquaculture with shrimp disease control."
Aquaculture is growing rapidly worldwide and has the potential to alleviate the increasing pressure on wildlife to fish. Freshwater shrimp are already being produced in aquaculture systems around the world, from Louisiana to Thailand to Senegal and beyond.
In these aquaculture systems, young shrimps are first reared in hatcheries, then stored in waters where schistosomiasis is transmitted, and finally harvested once they reach a marketable size. As the shrimp grow, they feed on the snails that carry the schistosome parasite.
The parasite is unable to infect the shrimp itself, and schistosomiasis is not transmitted by ingestion.
Researchers used economic and epidemiological models to determine the optimal timing for shrimp storage and harvest, with the common goal of reducing the transmission of schistosomiasis and generating revenue from the sale of harvested shrimp.
"Our results show that there are highly advantageous configurations of aquaculture systems for shrimp that minimize the trade-offs between harvesting shrimp yields and reducing the transmission of schistosomiasis," Hoover said. "We can develop systems that maximize profits while having a significant impact on reducing disease and potentially helping to lift the population of emerging and developing countries out of poverty."
Bilharzia, also known as "snail fever," affects around 250 million people a year and kills as many as 200,000. The disease spreads especially when people come into contact with contaminated water. While medications are available to treat the disease, they may not be sufficient in some situations. Because drug treatments only affect the human component of the parasite's transmission cycle, people are prone to re-infection shortly after treatment.
By intervening on the environmental component of the transmission cycle – the intermediate-snail population – shrimp-based measures can be taken that can complement drug treatment and bring greater benefit to the population.
The model showed that the introduction of native shrimp in infected waters to reduce parasitism is comparable to the standard approach of comprehensive bilharzitic drug regimens and may reduce emissions of parasites after 10 years to almost zero.
Shrimp can also benefit the environment, including the replacement of chemical pesticides to combat snail populations and the restoration of biodiversity in areas where native shrimp species have been decimated by dams.
Chris's research is a new tool for our global efforts to fight schistosomiasis. "Sa id Justin Remais, head of the Department of Environmental Health Sciences and co-senior author of the study." Poverty and schistosomiasis are inextricably linked, and transmission of the parasite is known to inhibit children's growth and cognitive development and prevent adults from working , which increases poverty. Targeted transmission of the parasite itself and support for a local production system If there are economic benefits for the population, this approach has great potential to complement ongoing disease control campaigns that are generally based on drug treatment alone. "
Researchers find shrimp solution to spread deadly diseases
Christopher M. Hoover et al., Modeled Effects of Shrimp Aquaculture on Combating Poverty and Bilharzia, Nature Sustainability (2019). DOI: 10.1038 / s41893-019-0301-7
How Fat Shrimp Can Save Lives (2019, July 23)
retrieved on July 23, 2019
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