Extension Viewpoints: Infectious disease surveillance: What we are learning from bats and mosquitoes

By Ty Betts and Robin Young
PREVIEW Columnist
We know surveillance is used to keep an eye on convenience stores and homes; it is also used to monitor the spread of infectious diseases. Of course, video cameras will not work to spot viruses or bacteria, so researchers at Colorado State University (CSU) are working to create other methods that allow us to watch out for infectious disease harmful to humans.
Anna Fagre, Ph.D. student in CSU’s Department of Microbiology, Immunology and Pathology, investigates how bats might be useful for disease surveillance. In Uganda, Fagre studies bats in caves visited by humans for recreational or religious purposes to determine what diseases or viruses might be present in that area.
“We look at the potential for bats to act as reservoirs for these viruses,” Fagre said.
Through non-lethal sampling, Fagre collects blood, saliva and fecal samples to find out what diseases exist in the bats. This information allows the researchers to determine if a particular disease might spread via blood through arthropod vectors like mosquitoes or through the bat’s own fluids.
As the first veterinarian to receive the $25,000 Robert E. Shope International Fellowship, Fagre specializes in understanding the parasites found on bats, such as ticks and bat bugs, to study how these arthropods might transfer diseases from bats to humans. But her team intends to take data collection a step further.
“When we trap the bats, we’ll be microchipping them, kind of like you would a dog or a cat, so we can identify the bats moving forward,” Fagre said.
With GPS technology, the team will be able to track individual bats, view where they have been and examine whether they’ve picked up a disease between samplings. This can be extremely valuable in pinpointing where a virus is spreading from or what population of bats has been infected.
“It allows us to get a step ahead of the virus,” Fagre explained. “If we know which viruses are present in the bat populations, and we know that humans are interacting with these bats by coming into these caves, then we know exactly which pathogens or viruses to be monitoring for in the human population.”
This information can help doctors to diagnose the problem more quickly in patients with unknown illnesses.
Mosquitos are the ultimate antagonist to the human species, spreading deadly diseases responsible for more deaths than the totality of all our wars. But CSU researchers intend to use mosquitoes to keep a watchful eye on the diseases these insects carry.
Bekah McMinn, graduate student researcher in Department of Microbiology, Immunology and Pathology, is working on a pilot study in Guatemala to test whether we can detect and monitor pathogens in mosquitoes that have recently fed on humans or animals, a method she says could make surveillance of viruses much easier.
“Being able to sample blood from humans and animals in mosquitos is a huge sample source that we can utilize for a number of things,” McMinn said. “The number of applications is kind of limitless.”
By capturing and testing mosquitoes that have recently fed on humans or animals, this study looks to determine whether viral, bacterial or parasitic organisms that are found in the blood of those humans and animals can also be detected from the blood-meal of mosquitos. This method, known as xenosurveillance, allows scientists to monitor pathogens circulating in humans, even diseases the mosquitos aren’t necessarily responsible for spreading. Some of the pathogens the scientists are monitoring include dengue fever, Zika and other viruses.
Xenosurveillance could also track the movement and introduction of pathogens into livestock, such as the Rift Valley fever virus, which is responsible for significant economic consequences from livestock deaths in Africa.
“If we’re able to use mosquitoes as a way to surveil our livestock populations and our deer populations and see if Rift Valley fever virus is actually circulating here, it would rapidly expand our ability to detect and react to this foreign introduction,” McMinn explained.
The use of bats and mosquitoes for disease surveillance can change the way we monitor and prepare to combat diseases. If these methods are proven effective, the risk of being caught off-guard by an outbreak could be greatly diminished. “The impetus behind this project is disease preparedness,” Fagre said.
And while Fagre recognizes that bats are potential vectors for disease transmission, she underlines the value they hold ecologically and as an extraordinary species.
“They provide a lot of important ecosystem services like insect control and pollination,” Fagre said. “We want to better understand the ecology of the bats so we can minimize interactions between humans and bats when the bats are infected with something.”
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This story was posted on March 22, 2020.