Mould: The Hidden Threat to Mosquito Control

Attractive Targeted Sugar Bait (ATSB) is an outdoor tool designed to help control mosquito populations. It works by taking advantage of the fact that Mosquitoes often seek out sugary substances. When they consume ATSB, which can include Insecticides or toxic chemicals, it can lead to their demise. Simple, right? This has led to the testing of various chemicals for mosquito control, including familiar names like pyrethroids and neonicotinoids.

#How ATSB Works

The original version of ATSB was sprayed on plants near water bodies where mosquitoes breed. This method effectively reduced mosquito numbers in various regions, but it raised some environmental concerns. Spraying could harm non-target organisms, which isn’t ideal when trying to create a balance in nature.

The newer version, referred to as ATSB 1.2, uses a fruit syrup to attract mosquitoes. This syrup is mixed with dinotefuran, a type of insecticide. The ATSB stations are placed outdoors, usually hung on walls under roofs, which helps to control mosquitoes that invade our homes. In prior tests, ATSB has shown remarkable success, cutting down populations of female mosquitoes significantly.

#The Mould Problem

Despite the promising results, there’s a fly in the ointment-or should we say mould in the bait? During trials in western Kenya, researchers found mould growing on many ATSB bait stations. This was especially common when the bait stations were placed in exposed areas with limited roof overhang. Mould growth can be linked to weather conditions, such as humidity and rainfall, which are abundant in western Kenya.

In Zambia, mould accounted for almost 30% of the damage to ATSBs, and the longer they were left in the field, the more mould they developed. Bait stations that got torn were particularly prone to mould growth. So, if you think mould is just a problem for your old bread, think again! It can cause chaos in the battle against mosquitoes as well.

#What Mould Likes

Mould thrives on certain materials, such as cardboard and wood, and it loves moisture and carbohydrates. As it turns out, ATSB is mostly sugar (approximately 70% sugar solution), providing an excellent buffet for mould. If too much mould grows, it may reduce the effectiveness of ATSB by making it less appealing to mosquitoes or blocking their access to the sugary bait.

Mould isn’t just bad for mosquitoes; it raises potential health concerns for humans living nearby. The current guidelines state that if ATSB stations have mould spots bigger than a pencil eraser, they need to be removed. This can lead to a waste issue if the stations are taken down too frequently.

#The Study Aim

To figure out just how much mould affects ATSB's ability to kill mosquitoes, researchers decided to conduct experiments. They looked at the feeding rates of mosquitoes on both mouldy and clean ATSBs in a controlled lab environment. They also checked how the effectiveness of ATSB changed after being deployed beyond the six-month mark advised by the manufacturer.

#The Research Setup

The researchers selected 100 ATSB stations and placed them in Asembo, an area in western Kenya. This was part of a larger study involving ATSBs from March 2022 to March 2024. Fifty of these stations were freely exposed to the elements, while the other fifty were protected under a roof. They hung the bait stations about six feet off the ground, hoping to minimize unwanted wildlife interference while maximizing mosquito attraction.

#Mould Culturing & Identification

To investigate the mould problem, the researchers took six bait stations that were significantly mouldy and more than six months old. They transported these to their lab, where they scraped off some mould and placed it in a growth medium to see what types of mould were there. Spoiler alert: the mould came back looking white and fluffy but quickly turned black. The sneaky culprit turned out to be a type of mould called Aspergillus niger.

#Getting Mosquitoes for Testing

In order to test how effective ATSBs were, researchers needed mosquitoes. They collected Anopheles larvae near Ahero and raised them in the lab. For a few days, these baby mosquitoes were well-fed and pampered until they grew into adult mosquitoes, ready to do their part in the experiment.

#Testing Feeding Rates and Mortality

Once the mosquitoes were ready, the researchers carried out monthly tests to check how effective the ATSB stations were. They took mouldy stations from exposed areas and non-mouldy ones from protected areas to see how many mosquitoes were attracted to each type. They also had some brand-new, never-used bait stations for comparison.

For the testing, they placed each ATSB in a cage with a bunch of mosquitoes that were given 48 hours to feed. The researchers then counted how many mosquitoes were dead and how many had consumed the bait, checking for the presence of uranine dye, which indicates they had fed.

#The Results

Upon analyzing the data, it became apparent that both the time the ATSB had been out in the field and its location mattered significantly. Mouldy stations had a lower feeding rate after just five months compared to the ones kept in controlled lab environments. By the fifth month, feeding rates had dropped to about 87% for the mouldy bait while lab bait still maintained around 92%.

Although there were no significant differences at individual time points, the overall trend showed that exposed bait stations consistently had lower feeding rates.

#Mosquito Mortality Rates

Just like the feeding rates, mortality rates were also affected. The researchers found that the mouldy ATSBs had lower mortality rates over time compared to the clean ones. By the fifth month, the mouldy bait's mortality rate dropped below that of the lab controls, raising concerns about its long-term effectiveness.

While no significant differences were detected at specific points in time, the final estimate showed some decline. Remarkably, even after a whole year, ATSBs could still deliver a dose of insecticide, but there were signs that extending use beyond six months might require a review of the product.

#The Mould Mystery

After all this testing, it was clear that a balance was needed. While the ATSB stations still worked, the environmental conditions really dictated their effectiveness. The mould could be a serious problem since it may block access to the bait and create a less appealing option for mosquitoes.

The worry is not just about mosquitoes but also about human exposure to these moulds. Identifying and understanding the species of mould that grow on these stations is crucial. In this case, Aspergillus niger was the main suspect, but the safety levels of these fungi were still unclear.

#The Community Perspective

The growth of mould on ATSB stations can also impact how communities perceive the effectiveness of this mosquito control method. If people see unsightly mould growing on things hung near their homes, they could develop negative feelings about the ATSB altogether.

The community’s acceptance is vital for any control strategy to work. It’s essential to find a way to keep bait stations functional and maintain the community’s trust while considering operational practicality.

#Possible Solutions

Given the mould issues, it becomes evident that the design of ATSB stations may need to be reconsidered. Perhaps it's time to think about adding anti-mould agents to the product so it can resist these environmental conditions.

The study highlights that in places with high humidity, like western Kenya, mould is much more likely to grow than in drier areas, such as Mali, where previous tests showed no mould.

#Recommendations for Future Studies

The current testing method relied on lab cages. Mosquito behavior can vary in natural settings, so researchers should consider a more holistic approach in future studies. This also means looking at weather patterns over time to trace how they affect both mosquito feeding and mould growth.

With a limited number of ATSB stations tested, future research should involve more samples to get a clearer picture. The current study couldn’t fully differentiate between the effects of mould and the environmental location because the two were intertwined.

#Conclusion

In summary, while the ATSB stations have proven to be effective in controlling mosquito populations up to a certain period, mould growth creates some challenges that should not be overlooked. Feeding and mortality rates decline after five months, but whether this is directly attributable to mould or environmental factors remains to be seen.

Going forward, it’s essential to find a balance between efficacy and safety, ensuring that these products remain effective while also being safe for the people who live near them. This study laid the groundwork for understanding how outside influences, like mould, can impact health interventions. With a little humor and a can-do attitude, who knows? We just might keep the mosquitoes at bay while keeping our homes clean!