There are no teensy cups. But a new urine test for wild mosquitoes has proved for the first time that it can offer an early warning that local pests may be spreading disease.
The new test added a pee-collecting card to a mosquito trap. That card picked up telltale genetic traces of West Nile and two other worrisome viruses. Researchers in Australia described the new technique April 4 in the Journal of Medical Entomology.
The idea grew out of testing insect saliva. Scientists unveiled such tests in 2010. These lured mosquitoes into tasting cards coated with honey. The skeeters left some saliva behind. Scientists then checked for genetic traces of viruses in that saliva.
Saliva checking had its charms. The cards do not have to stay cold the way samples of whole insects do. And the saliva method did not take as much work as checking chickens or pigs for signs of a virus.
But the tiny traces of saliva left on these cards were almost too small to test. A mosquito drools fewer than five nanoliters of saliva when it tastes a card. In contrast, mosquitoes excrete about 1.5 microliters of liquid per pee. That’s a flood compared with saliva.
That flood prompted Dagmar Meyer of James Cook University in Cairns, Australia and her colleagues to create a urine collector. They used standard overnight traps that lure mosquitoes with light. They also used longer-standing traps that exhale carbon dioxide, which lures a mosquito.
The team set out 29 urine traps in two insect-rich spots in Queensland, Australia. Researchers also set out saliva traps. When mosquitoes entered a urine trap, their pee dripped through a mesh floor onto a collecting card. Adding a moist wick of water kept trapped mosquitoes alive and peeing longer. That improved the sample.
Pee traps picked up three viruses — West Nile, Ross River and Murray Valley encephalitis (En-seff-uh-LY-tis). The saliva ones only detected two, the researchers report.
carbon dioxide (or CO2) A colorless, odorless gas produced by all animals when the oxygen they inhale reacts with the carbon-rich foods that they’ve eaten. Carbon dioxide also is released when organic matter burns (including fossil fuels like oil or gas). Carbon dioxide acts as a greenhouse gas, trapping heat in Earth’s atmosphere. Plants convert carbon dioxide into oxygen during photosynthesis, the process they use to make their own food.
colleague Someone who works with another; a co-worker or team member.
constant Continuous or uninterrupted.
encephalitis An inflammation of the brain, usually caused by a viral infection. The disease can impair movement, clarity of thinking and other facets of brain function. In severe cases, this condition can lead to death.
entomology The scientific study of insects. One who does this is an entomologist.
excrete To remove waste products from the body, such as in the urine.
genetic Having to do with chromosomes, DNA and the genes contained within DNA. The field of science dealing with these biological instructions is known as genetics. People who work in this field are geneticists.
honey A viscous (gooey) material that honeybees store in their honeycombs. The bees make it from nectar. Foraging bees visit flowers in search of that sugary liquid. honey.
insect A type of arthropod that as an adult will have six segmented legs and three body parts: a head, thorax and abdomen. There are hundreds of thousands of types of insects, which include bees, beetles, flies and moths.
journal (in science) A publication in which scientists share their research findings with experts (and sometimes even the public). Some journals publish papers from all fields of science, technology, engineering and math, while others are specific to a single subject. The best journals are peer-reviewed: They send all submitted articles to outside experts to be read and critiqued. The goal, here, is to prevent the publication of mistakes, fraud or sloppy work.
Queensland One of the states that makes up the northeast corner of the country of Australia.
sentinel A guard or something that watches over others, or that effectively offers some warning of a potential problem. (in ecology) Species that scientists monitor to get information about the environment in which those organisms live. These species might be more sensitive to some environmental hazards, and so can indicate to researchers when those hazards are reaching dangerous levels.
virus Tiny infectious particles consisting of RNA or DNA surrounded by protein. Viruses can reproduce only by injecting their genetic material into the cells of living creatures. Although scientists frequently refer to viruses as live or dead, in fact no virus is truly alive. It doesn’t eat like animals do, or make its own food the way plants do. It must hijack the cellular machinery of a living cell in order to survive.
West Nile A disease caused by a virus that is transmitted by mosquitoes. Most people develop no symptoms. But about one in five infected people will get a headache, body aches, joint pains, vomiting, diarrhea, fever or some rash. A very small share of infected people will also develop coma, seizures or paralysis.
Journal: D.B. Meyer et al. Development and field evaluation of a system to collect mosquito excreta for detection of arboviruses. Journal of Medical Entomology. Published online April 4, 2019. doi:10.1093/jme/tjz031.