Host's genetics influences risk of worm infection
When health organizations must treat a widespread endemic illness in a short period of time, whom should they choose to help first? Medical groups often start by identifying the population subset most susceptible to infection. An increased risk of disease is often due to environmental factors - for example, a group of families that bathe in unclean water - but can also be influenced by a person's genes.
A recent international study anchored by the Hopkins medical school found that a person's DNA helps to determine his or her susceptibility to parasitic infection. Led by Audrey Grant, the team studied the parasitic worm Schistosoma mansoni and its effects on over 300 families in Condia, Bahia, in Brazil.
To assess the role of genetics in S. mansoni infection, the team focused on two specific traits: the participants' immune responses to the parasite and the intensity of their infections.
First, the team indirectly quantified the participants' immune responses to the parasite by measuring the immunoglobulin E (IgE) levels in their blood. IgE is an important class of proteins in the immune system that responds to allergens and parasites.
An infection with S. mansoni leads to increased IgE levels. The team then used a fecal egg count to study the intensity of infection in each individual.
After extensive statistical analysis, the team found that family members responded to the parasite similarly - proof that a person's reaction to S. mansoni is under complex genetic control.
"Studies that investigate heritability . . . constitute a first step in the effort to identify susceptible subsets of the population," Grant said. "Future studies could give rise to new strategies for treatment." Schistosomiasis - infection with any species of the parasitic worm genus Schistosoma - affects over 200 million individuals worldwide. Because aqueous snails act as hosts for the parasite, the disease is often called snail fever.
Schistosomiasis is rarely deadly but can produce chronic fever, diarrhea and internal organ damage. And though the parasite has been successfully eliminated from a number of regions, re-infection is common.
A recent international study anchored by the Hopkins medical school found that a person's DNA helps to determine his or her susceptibility to parasitic infection. Led by Audrey Grant, the team studied the parasitic worm Schistosoma mansoni and its effects on over 300 families in Condia, Bahia, in Brazil.
To assess the role of genetics in S. mansoni infection, the team focused on two specific traits: the participants' immune responses to the parasite and the intensity of their infections.
First, the team indirectly quantified the participants' immune responses to the parasite by measuring the immunoglobulin E (IgE) levels in their blood. IgE is an important class of proteins in the immune system that responds to allergens and parasites.
An infection with S. mansoni leads to increased IgE levels. The team then used a fecal egg count to study the intensity of infection in each individual.
After extensive statistical analysis, the team found that family members responded to the parasite similarly - proof that a person's reaction to S. mansoni is under complex genetic control.
"Studies that investigate heritability . . . constitute a first step in the effort to identify susceptible subsets of the population," Grant said. "Future studies could give rise to new strategies for treatment." Schistosomiasis - infection with any species of the parasitic worm genus Schistosoma - affects over 200 million individuals worldwide. Because aqueous snails act as hosts for the parasite, the disease is often called snail fever.
Schistosomiasis is rarely deadly but can produce chronic fever, diarrhea and internal organ damage. And though the parasite has been successfully eliminated from a number of regions, re-infection is common.
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