Pestology Blog
Ant Detecting Robots, Malaria Transmission, and Mosquito Repellent Devices
Fairfax, VA – February 1, 2024
In this episode, Mike shares new breakthroughs in artificial intelligence technology used to locate invasive ants, Laura highlights research looking at how age impacts malaria transmission in mosquitoes, and Ellie reviews a recent study investigating if mosquito repellent devices impact pollinators. We're joined by special guest, William Hoffman of Hoffman Exterminators.
Featured Article Summaries
Ant Detecting Robots
Use of Artificial Intelligence for Automated Detection and Surveillance of Red Imported Fire Ants Nests
I’ve covered research papers that involved the red imported fire ant (RIFA), Solenopsis invicta, in previous articles and podcast episodes, so I’ll keep my background information relatively brief1. The important cliff notes are that RIFA is an incredibly damaging invasive pest that wreaks havoc on non-native ecosystems. It’s native to South America and has slowly made its way around the world thanks to various methods of human mediated transport. Workers are incredibly aggressive when foraging for food and defending territory, allowing this species to easily outcompete other ants and organisms for resources. The RIFA also packs a painful sting that can be fatal to anyone with an allergy to insect stings. To convert their destruction into cold hard cash, the RIFA ranks as the 5th costliest invasive species globally, accounting for approximately $17 billion in economic damages and management costs over the past few decades (1970 to 2017)2.
Stopping the spread of the RIFA is critical to minimizing ecological and economic damages as well as protecting public health. But that’s easier said than done. Despite our best efforts to contain it, the RIFA has spread across most of the southern US since its initial introduction in the 1930’s. Early detection is critical to stopping or slowing the RIFA’s expansion, but finding stow-away ants in transported goods can be tough. In the past, detection methods have included physical inspections of transported goods and visual surveillance to locate mounds and foraging workers in the field. Both options can be effective but there is always the potential for human error as reproductives or small nest fragments hidden in transported goods can easily be missed, and smaller mounds may be overlooked.
Researchers at China’s Lanzhou University set out to improve fire ant surveillance by removing the human element all together with the help of advanced robotics and artificial intelligence (AI). The team trained an open-source AI system to identify RIFA nests by uploading over 1,000 images taken of nest mounds from various angels and conditions. Once the AI program was ready, it was installed onto a state-of-the-art robotic Cyberdog equipped with sophisticated sensors, cameras, thermal imaging devices, chemical detectors, and other technology that allow the robot visually process the surrounding environment and compare that data to the upload of fire ant mound images.
To test the performance of the ant-detecting robot k9 against humans, researchers gave the Cyberdog and three human surveyors 10 minutes to inspect a 300-square-meter nursery for RIFA mounds. At the end of the survey period, the Cyberdog found three times more nests than its human counterparts. In addition, the cyberdog missed fewer nests and had a lower false detection rate than the human inspectors.
Although this technology is still in the early development phase and likely comes with a heavy price tag, this study gives great promise to what the future of pest surveillance and invasive species management might look like. Imagine a not-so-distant future where you show up to your client’s home to perform their regular service. Before going inside to chat with your client, you deploy your CyberDog Pest Detector 1000 (I totally made this name up by the way) to inspect the exterior of the structure and surrounding property. By the time you’ve finished resolving any interior issues, the CyberDog has prepared a detailed report of pest activity and has mapped locations and treatment recommendations for each incidence logged. This is all hypothetical of course, but based on the direction that technology and AI are heading, this may not be as far “fetched” as it sounds.
Article by Mike Bentley, PhD, BCE
References
Xin Su, Guijie Shi, Jiamei Zhong, Yuling Li, Wennan Dai, Guohua Xu, Eduardo G. P. Fox, Hualong Qiu, Zheng Yan. Use of Artificial Intelligence for Automated Detection and Surveillance of Red Imported Fire Ants Nests. bioRxiv 2023.05.26.542461; doi: https://doi.org/10.1101/2023.05.26.542461
Malaria Transmission
Mosquito Ageing Modulates The Development, Virulence and Transmission Potential of Pathogens
One of the most important reasons for pest management is the protection of public health. A number of the pests that we are charged with managing can transmit serious diseases. But do we fully understand how those diseases are transmitted from insect to human?
The transmission of pathogens from an invertebrate host to a vertebrate host is not always a hard and fast rule. There are several factors that can influence the success of transmission, such as the immune response of both the invertebrate and the vertebrate to the pathogen, the type of pathogen, the level of infection of the pathogen in the invertebrate, and more. However, one of the factors that has not been fully studied is the age of the insect host and how it can affect the success of transmission to the vertebrate host. Age can potentially be a huge factor in how pathogens are transmitted, as both the behavior and the biology of the insect host can drastically change across their lifetimes.
This paper specifically looked at the effects of adult age of Anopheles colluzzii (a member of the Anopheles gambaie species complex) on the transmission of Plasmodium falciparum, or the protozoan parasite that causes malaria. Plasmodium falciparum is transmitted through the bite of female Anopheles mosquitoes when they blood feed to produce eggs and is the deadliest parasite in humans. Plasmodium falciparum is responsible for the majority of the deaths associated with malaria.* The researchers raised Anopheles colluzzii mosquitoes in the lab, and then provided them with a blood meal that was infected with Plasmodium falciparum either 12 days, 8 days, or 4 days post-emergence from the pupal stage.
First, the researchers examined the ability of the different age groups of mosquitoes to act as a competent host for the parasite. This was done by counting the number of different life stages of the parasite that were visible when they dissected the adult mosquitoes. The researchers found that the oldest mosquitoes, which were fed the infected blood meal at 12 days, featured the lowest number of parasites compared to the two other age groups. This suggests that mosquitoes exposed at a later age to the parasites are less likely to be successful hosts for the parasite.
Similarly, the researchers also looked at the progression of the parasite’s lifecycle within the mosquito post-feeding on the infected bloodmeal. This aspect of the study determined if age of the mosquito influenced Plasmodium falciparum’s development. The researchers found that despite the age differences with the mosquitoes, the development of Plasmodium continued at its normal pace, and did not differ between mosquitoes fed at 4-days or 12-days post-emergence.
The researchers also examined the combined effects of age and infection status on mosquito survival. The mosquitoes that fed on an infected blood meal either 4- or 8-days post-emergence showed no difference in survival compared to their uninfected counterparts. However, the mosquitoes that fed on the infected bloodmeal at 12-days post-emergence had a significantly longer lifespan compared to their uninfected counterparts. This suggests that Plasmodium may have a “fountain of youth” effect on older mosquitoes that gave them a median of an extra two days of survival.
After taking all this data into account, the researchers then created a model to estimate the ability of each age group to transmit Plasmodium falciparum. Unsurprisingly, the model revealed that the mosquitoes that were exposed at the youngest age had the highest potential to transmit the parasite. But the mosquitoes that were exposed at an older age of 12 days post-emergence were not that far behind them, and still had a higher potential for passing on the parasite than their uninfected counterparts.
So what does all this data tell us about age and how it affects transmission of Plasmodium falciparum in Anopheles colluzzii? Mostly, much like a Facebook status in approximately the late 2000s: it’s complicated. While mosquitoes that were exposed to the parasite at a younger adult age still hold the crown for the highest transmission potential, it appears that there are confounding factors that can still make mosquitoes exposed at an older adult age just as capable of transmission, but at a lower potential. Although the mosquitoes exposed at an older age don’t appear to be great hosts for the parasite, the extended lifespan offers more potential for the mosquito to spread Plasmodium falciparum. This may be especially true as previous studies have shown that Anopheles mosquitoes will not only increase their bloodmeal intake, but will also increase the number of times that they seek out a bloodmeal.^
If anything, this study has proven that age is not just a number, but an important factor to consider in disease transmission. While this study focused on the transmission of one disease, it emphasizes the complicated factors that can contribute to how a disease is passed on from invertebrate to a vertebrate. Understanding how a disease may be passed on from an invertebrate host to a vertebrate host can dictate management strategies of not only the pathogen, but also can potentially dictate how and when we treat for these public health pests.
Article by Laura Rosenwald, BCE
References
Somé BM, Guissou E, Da DF, Richard Q, Choisy M, Yameogo KB, Hien DF, Yerbanga RS, Ouedraogo GA, Dabiré KR, Djidjou-Demasse R, Cohuet A, Lefèvre T. Mosquito ageing modulates the development, virulence and transmission potential of pathogens. Proc Biol Sci. 2024 Jan 10;291(2014):20232097. doi: 10.1098/rspb.2023.2097. Epub 2024 Jan 3. PMID: 38166422; PMCID: PMC10762442.
*Severe malarial anemia: Innate immunity and pathogenesis. Perkins, D. J.; Were, T.; Davenport, G. C.; Kempaiah, P.; Hittner, J. B.; Ong'Echa, J. M. (2011). International Journal of Biological Sciences. 7 (9): 1427–1442. doi:10.7150/ijbs.7.1427. PMC 3221949. PMID 22110393.
^The malaria parasite, Plasmodium falciparum, increases the frequency of multiple feeding of its mosquito vector, Anopheles gambiae J.C. Koella , F.L. Sørensen and R.A. Anderson. Proceedings of the Royal Society of London. Series B: Biological Sciences Volume 265, Issue 1398 Published:07 May 1998 https://doi.org/10.1098/rspb.1998.0358
Mosquito Repellent Devices
A Volatilized Pyrethroid Insecticide from a Mosquito Repelling Device Does Not Impact Honey Bee Foraging and Recruitment
This paper looks at the effects of mosquito repelling Thermacell devices that use pyrethroids. Pyrethroids are a class of insecticides that are derived from pyrethrum which is from chrysanthemum flowers. There are a wide variety of pyrethroid products available and in particular this study looks at prallethrin which works in the mosquito repellant devices by turning into a gas that can spread through the air and affect flying insects. Now this aims to work on mosquitos but since it is in the air, any other insects, including beneficial pollinators, could fly by and potentially be affected.
Honey bees are a common pollinator and work well as a study organism. In case you weren’t convinced that bees are really cool, one of my favorite bug facts is that bees are very trainable. They won’t sit or roll over but you can get them to feed at particular places. This research took advantage of that fact and based on other studies’ methods of training, got the experimental groups to learn where a particular feeder was and prompted them to forage there. Foraging behavior is a good metric for determining if bees are affected by the product because foraging relies on flight and dance communication of individuals and since pyrethroids affect the nervous system of an insect, these behaviors would not perform well if affected.
The experiment began with setting up a foraging area and training the bees to forage there by placing the feeders close to the hive and stepwise moving them away to about 100 meters final distance. The researchers marked bees as they foraged at the feeder with color/number coded plastic discs so they could monitor visits from each bee.
They split the feeder into two locations equidistant to the hive and one had the repellant device placed about 2 meters away. This is within the effective range of the device. The observational times and active device time was between 4pm and 8pm which is typical of when users may deploy the device in residential areas like their patio in the evening. The observations were recorded by camera and the marked bees were able to be tracked from the feeders and to the hive. There was a concurrent deposition study performed to make sure the repellant devices were working properly which they were, exactly as intended.
They found no significant difference between the control and treatment feeders and the various metrics of foraging to them. The different metrics they looked at between the footage from the hive and the feeders were foraging frequency, waggle dance propensity, waggle dance frequency, and feeder persistency. The waggle dance, if you are unfamiliar, is the series of movements honey bees perform at the hive to communicate the location of and other information about a feeding source. Other bees will go to the described location to forage. Because this was no different between the control and treatment, the conclusion is that the pyrethroid based aerial mosquito repellant device has no observable effect on honey bee foraging behavior. This means that it is potentially safe for bees and the general public can use it without worry of affecting their local pollinators.
Now, I do want to clarify that this may not extend to every product within the pyrethroid class, but in lab tests, all were more toxic to mosquitos than to honey bees. So overall, this device may be a good option for residential areas for those especially concerned about their bees.
Article by: Ellie Lane
References
Margaret J Couvillon, Bradley D Ohlinger, Connor Bizon, Lindsay E Johnson, Laura C McHenry, Benjamin E McMillan, Roger Schürch, A volatilized pyrethroid insecticide from a mosquito repelling device does not impact honey bee foraging and recruitment, Journal of Insect Science, Volume 23, Issue 6, November 2023, 11, https://doi.org/10.1093/jisesa/iead079
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