‘Altered body odour indicates malaria even if microscope doesn’t’
Making a friend is hard work. Keeping one is even harder, especially for young children. A novel study published in the Journal of Family Psychology sheds light on why childhood friendships fall apart and is the first to demonstrate that parents are an important source of these breakups.
Looking at data from 1,523 children (766 boys) from grades one to six, researchers from Florida Atlantic University and the University of Jyvaskyla in Finland conducted a survival analysis to identify the characteristics of parents that predict the stability of their children’s friendships. The researchers examined mother and father reports of their own depressive symptoms and parenting styles and used these reports to predict the occurrence and timing of the dissolution of best friendships from the beginning to the end of elementary school (grades one to six).
The researchers assessed three commonly recognized parenting styles: behavioural control such as curfews and monitoring; psychological control such as shaming and guilt; and warmth and affection. They also assessed parental depression to disentangle the unique contributions of parenting styles from parent mental health difficulties known to shape parenting. Lastly, they assessed the children’s peer social status or how wellliked they are by other children to separate the effects of parenting from difficulties that children have getting along with peers.
“We already know that peer status plays an important role in friendship outcomes. For example, well-liked children have more long-lasting relationships than do their classmates,” said Brett Laursen, Ph.D., co-author of the study and a professor and graduate studies coordinator in the Department of Psychology in FAU’s Charles
Typhoid Mary may have infected a hundred or more people, but asymptomatic carriers of malaria infect far more people every year. An international team of researchers is working toward a way to identify malaria patients including infected individuals who show no malaria symptoms.
People who have malaria but are not symptomatic abound in the heaviest areas of malaria infestation. Even blood tests do not necessarily pick up infection with the plasmodium parasite, especially at low parasite densities. DNA tests for the parasite usually show infection, but they are far from rapid.
“Our previous work in a mouse model found that malaria infection altered the odours of infected mice in ways that made them more attractive to mosquitoes, particularly at a stage of infection where the transmissible stage of the parasite was present at high levels,” said Consuelo De Moraes, adjunct professor of biology, Penn State, and professor of environmental systems science, ETH Zurich. “We also found long-term changes in the odour profiles of infected mice.”
The researchers wanted to see if they could identify changes in human odours associated with malaria infection that might be useful for diagnosing infected individuals. They were particularly interested in identifying those who were infected, but had no symptoms. The researchers initially used microscopy and an SD Bioline Rapid Diagnostic Test to identify patients with malaria. Because these methods have limited sensitivity, particularly when parasite loads are low, infections were confirmed by DNA tests. They identified 333 people who unambiguously were either infected with malaria or were not infected with malaria.
Only if both microscopy and DNA studies were negative were subjects considered malaria-free. Infected patients for the initial
“We were hoping that positive behaviors would help extend the life of friendships and that it would be a buffer or a protective factor,” said Laursen. “This wasn’t the case -warmth and affection don’t appear to make that much of a difference. It’s the negative characteristics of parents that are key in determining if and when these childhood friendships end.”
Findings from this study also confirmed that most friendships were transitory; fewer than 10 percent of first-grade best friendships survived from the first to the sixth grade, with roughly half (48 percent) studies were both microscopy and DNA positive for malaria. In some later analyses, the researchers included 77 people who were positive for malaria according to DNA, but showed no parasites in the microscopic tests. Malaria infection does not create new volatile chemicals in the body, but alters the amounts -- up or down -- of volatile chemicals that are already present in the odors of healthy people.
“It is interesting that the symptomatic and asymptomatic infections were different from each other as well as from healthy people,” said Mark C. Mescher, adjunct professor of biology, Penn State, and professor of environmental systems science, ETH Zurich.
This difference among infected, infected asymptomatic, and healthy individuals may eventually lead to tests capable of rapidly and accurately identifying infected people, even those without symptoms.
The researchers report in (May 14) issue of Proceedings of the National Academy of Sciences that predictive models using machine learning reliably identify infection status based on volatile biomarkers. They state “our models identified asymptomatic infections with 100 percent sensitivity, even in the case of low-level infections not detectable by microscopy.” These results far exceed any currently available rapid diagnostic tests.
“But, we should emphasize that we are a long way away from developing a practical diagnostic assay based on odour cues,” said De Moraes.
For a test to succeed it would need to be rapidly and cheaply deployable under field conditions, but still detect infections with high sensitivity.
“In the near term, our goal is to refine the current findings to find the most reliable and effective biomarkers we can,” said Mescher. “This is really basic science to identify the biomarkers of malaria. There is still a lot more work to be done to develop a practical diagnostic assay,”