Plague Persistence: Insecticide Resistance and Climate Change Threats

Key Quotes

"so the interesting thing about the bubonic plague is that after these great pandemics that killed many people in the medieval ages and during what we call the asian plague which was really where we saw a lot of the outbreak also in in the asian area india china etcetera in the late 1800s and early 1900s and that sort of continued sporadically till probably the 1920s or 30s and this is when we thought that was the end of plague right but but this is really was a critical time when actually the organism the bacteria that causes plague yersinia pestis became established in reservoir rodent hosts all over the world because it was a time obviously when people started to travel a lot for example in the united states right we were getting ships that were coming from asia onto the pacific coast places like san francisco and and seattle and areas like that where you'd see rats that were infested with fleas carrying the plague"

Dr. Viveka Vadi Vallo explains that the bacteria causing plague, Yersinia pestis, became established in rodent populations globally during a period of increased travel in the late 1800s and early 1900s. This establishment occurred even after major pandemics, indicating the bacteria's persistence in animal hosts. Vadi Vallo highlights how international shipping facilitated the spread of infected rats and fleas to new regions, such as the Pacific coast of the United States.

"so when we think about plague right it's really a disease of rodents and fleas and humans tend to be just these incidental infected hosts at some point when they happen to run into an infected flea or a rodent that you know might die of of plague and then the fleas are looking for a new blood meal right so a human comes by flea jumps on and then passes the bacteria onto them"

Dr. Viveka Vadi Vallo clarifies that plague is fundamentally a disease affecting rodents and fleas, with humans acting as accidental hosts. Vadi Vallo describes how humans become infected when they encounter fleas that have previously fed on infected rodents. These fleas then transmit the bacteria to humans while seeking a new blood meal.

"we know that the the disease we say is endemic on probably practically every continent except for probably australia and we have areas that are real hotspots where we know that we can do surveillance work and we can detect plague especially when we have rodent die offs like in the united states we might see prairie dogs etcetera which actually are the main rodent species that infected with with the plague when they when we see die offs of these populations we can go out there we can do surveillance we can figure out if it's plague and then and then we know that the disease is around and we see that all over the world china mongolia madagascar africa the congo tanzania places like that south america's places like peru etcetera we know where this disease the regions where this disease is is especially prominent"

Dr. Viveka Vadi Vallo states that plague is endemic on nearly every continent, with specific "hotspots" identified through surveillance. Vadi Vallo points to rodent die-offs, such as those observed in prairie dog populations in the United States, as indicators of plague presence. She lists various countries across Asia, Africa, and South America where the disease is particularly prominent.

"right so it can be easily treated with antibiotics that's correct and i think in areas where we have these robust public health systems and that's usually you know places like the united states right we have resources but when we have outbreaks in in poor countries like madagascar and you know the democratic republic of the congo we usually have a situation where these are really resource poor countries right they they don't necessarily have the resources to be able to go out there and treat people with antibiotics very easily so this is where we see disease outbreaks as a bigger problem"

Dr. Viveka Vadi Vallo confirms that plague is treatable with antibiotics, but access to this treatment is a significant issue in resource-poor countries. Vadi Vallo contrasts the situation in countries with strong public health systems, like the United States, with that of nations such as Madagascar and the Democratic Republic of the Congo. She explains that limited resources in these latter countries hinder effective and widespread antibiotic treatment, leading to more severe outbreaks.

"but a lot more is known about those vectors and how they function um in order to transmit the disease less is known about fleas and for me that's where my interest lies because the way we manage plague really all over the world is through managing flea populations using insecticide spraying that's our primary way kill the host yes kill the host exactly is there a better way do you think i don't know if there's a better way i mean i think that one of the concerns though with that particular management strategy is that more and more we see that there's insecticide resistance building up"

Dr. Viveka Vadi Vallo expresses that less is understood about fleas, the vectors for plague, compared to other arthropod vectors like ticks or mosquitoes. Vadi Vallo states her research interest lies in fleas because current global plague management relies heavily on insecticide spraying to control flea populations. She raises concerns about the increasing development of insecticide resistance, suggesting a need for alternative strategies.

"i think we could be worried about that one very discerning feature of the plague in some areas and there've been studies done on on this is that plague outbreaks usually follow a very wet period or you know a period of high rainfall in some areas we don't know what underlies that but you know if we see shifts in climate in endemic areas that might result in probably flooding or heavy rainfall etcetera we might want to be cautious or we might want to consider that that might result in maybe an exacerbated period of plague in the environment and so you know risk of human infection becomes greater in that scenario"

Dr. Viveka Vadi Vallo suggests that climate change could potentially exacerbate plague outbreaks, noting a correlation between plague occurrences and periods of high rainfall or wet conditions. Vadi Vallo explains that shifts in climate leading to increased flooding or heavy rainfall in endemic areas might create conditions favorable for plague. She advises caution, as this could lead to an increased risk of human infection.