(10/29/21) BATON ROUGE, La. — Tick-borne rickettsial diseases like Rocky Mountain spotted fever and typhus are omnipresent worldwide and can be deadly if untreated, so why not stop them at their source – tick saliva? That is precisely what a $2 million grant awarded to the LSU AgCenter, Texas A&M University and the University of South Alabama seeks to determine.
The four-year grant funds the combined research of teams led by AgCenter entomologist Daniel Swale, Kevin Macaluso, chair of the Department of Microbiology and Immunology at the University of South Alabama and Albert Mulenga, associate head of the College of Veterinary Medicine and Biomedical Sciences at Texas A&M. Swale says the three scientists have combined their specializations in physiology and toxicology (Swale), microbiology and Rickettsia biology (Macaluso) and proteomics (Mulenga) to develop novel approaches to reduce the health burden of tick-borne diseases and resolve the epidemiology of rickettsial diseases.
“The founding principle behind the grant is to study how the tick salivary gland is able to generate and secrete saliva and how the pathogen interacts with the tick to alter this process,” Swale said.
Swale explained that a pathogen is the agent that causes a disease in humans. In this case, Rickettsia is the bacterial pathogen that can cause a variety of diseases in humans, such as Rocky Mountain Spotted Fever and Typhus. But, for some reason, not all rickettsial species do so, which has led Swale and his colleagues to seek to determine why these bacterial pathogens have differential pathogenicity.
“The question is two parts,” Swale said. “What does the pathogen do to the tick to promote its own transmission and cause disease in humans, and can we mitigate that by developing a chemical to prevent the interaction from occurring?”
Able to remove the salivary glands and study them under the microscope, the teams are researching how much saliva is produced from an isolated salivary gland to see if the pathogen causes the gland to become more active, and if they can shut the process down through newly developed chemistry.
“We measure the electrical potentials on the salivary gland membrane,” Swale said. “We want to find out if pathogen invasion into the salivary gland cells rely on electrical properties of that cell and, if so, can our chemistries alter that to prevent invasion into the salivary gland and subsequently prevent transmission.”
Swale credits one of his students, Zhilin Li, a doctoral candidate in the AgCenter Department of Entomology, for helping launch the project.
“He did an incredible job collecting data sets that facilitated the grant acquisition,” Swale said.
At this point, Swale admits the teams don’t yet understand much about the interactions of Rickettsia and a tick’s salivary glands, so they are seeking to define and enhance their knowledge to develop anti-transmission products that work from physiological, toxicological and molecular biology perspectives.
“The AgCenter is doing cutting-edge research on a variety of different topics from honeybees and agricultural pests to human disease vectored by arthropods,” he said. “The LSU AgCenter and the opportunities it provides to perform wide-ranging, impactful work like this is crucial for not only the citizens of Louisiana, but for the world at large.”
A normal tick gland with saliva secretion (above) and a gland treated with chemistry developed by LSU AgCenter entomologist Daniel Swale and his colleagues that prevents salivation (below). Photo by Daniel Swale/LSU AgCenter