Professor Maria Diuk-Wasser eco-epidemiology laboratory studies how human activity affects tick-borne diseases, including Lyme disease and babesiosis. Two new papers by current and former members of the lab – one just published, the other just accepted for publication – offer new details about how these diseases incubate and spread. Here, Diuk-Wasser discusses the articles’ findings and how they change our understanding of these diseases.
Prenatal transmission from mother to child could be the cause of an increase in babesiosis (at least in mice).
The one from the lab first paper focuses on two pathogens: Borrelia burgdorferithat causes Lyme disease, and Babesia microtiswhich causes babesiosis, a disease that has been on the rise in the northeastern United States during the last years. These two pathogens are transmitted by the same blacklegged tick and can infect the same host.
The pathogen that causes babesiosis can be passed from mother to child, which is not something that can happen with Lyme.
“One thing we found is that mother-to-offspring transmission is really fundamental to the ability of babesiosis to spread,” Diuk-Wasser said. “These results are important because although our study involves mice, prenatal mother-to-child transmission of babesiosis has also been observed in humans.”
Mother-to-child transmission of babesiosis appears to be more responsible for its spread than concurrent infection with Lyme disease.
Diuk-Wasser’s lab initially set out to explore how the pathogens that cause Lyme disease and babesiosis interact: do they help or suppress each other? Babesiosis is not transmitted as easily as Lyme, but it is on the increase, so their hypothesis was that the pathogen that causes Lyme enhances or facilitates the emergence of babesiosis.
“I was surprised how much more important mother-to-child transmission (in mice) was than co-infection with Lyme, which our original hypothesis centered on,” Diuk- water.
The paper uses field data collected on Block Island, Rhode Island, along with laboratory data, to create a mathematical model that estimates the ability of the pathogen responsible for spreading babesiosis.
Climate change could be partly responsible for the increase in babesiosis.
In the past, in the northeastern United States, many outdoor wild mice died during the winter, while ticks lived and transmitted a pathogen. But, Diuk-Wasser said, “we think more mice are surviving winters now and incubating Babesia during the winter, and it is a secondary factor that stimulates transmission.
Different strains of Lyme disease thrive in different host animals, which may explain why so many strains thrive.
There are still many strains of Lyme in the environment, some of which make people sicker than others. A question for researchers is why Lyme doesn’t behave like other diseases, such as COVID-19, where one strain tends to take over, replicate and cause the vast majority of infections.
In their second paper, Diuk-Wasser’s lab set out to explore the idea that certain strains of Lyme might be better suited to some animals than others. What they found was that some strains of the pathogen that causes Lyme disease are much more common in birds and others are much more common in mice, which at least partly explains why you see them all maintained in the wild.
Birds are more important to the spread of Lyme disease than previously known.
“We initially thought that the Lyme variants that cause the most severe disease in humans are those carried by mice, but this study showed that it’s actually more of a mix,” Diuk said. -Wasser. “Birds also incubate certain strains that are dangerous to humans. This indicates that birds are more important to the spread of Lyme disease than we thought. »
The fact that there are multiple strains (more than 15) circulating simultaneously at any one time allows us to catch Lyme disease repeatedly, even in the same season. “It’s not like COVID-19, where one dominant strain is circulating and then another is circulating several months later,” Diuk-Wasser said. Because so many strains are circulating and because animals tend to carry multiple strains at once, herd immunity is never achieved, either in human or animal populations.