Could Arthropods be the unexpected reservoirs of the 2022 and 2024 Mpox outbreaks?

Medical News: The 2022 Mpox (Monkeypox) outbreak involving the Clade 2b variants took the world by surprise, spreading across six World Health Organization (WHO) regions and resulting in over 86,000 confirmed cases and 111 deaths globally. With such a vast spread in non-endemic countries, scientists are racing to understand the various factors involved in the transmission of this zoonotic virus.


The disease triangle of mpox virus. Human mpox is a zoonotic infection with a disease triangle: the reservoir, the host, and the vector, respectively. According to the definition, the disease triangle is a conceptual model that shows the interactions between the environment, the host, and an infectious agent 

Now in 2024, we have a new outbreak involving the new Mpox Clade 1b variant which is fast spreading across the African continent with increasing lethal consequences.
 
To further complicate the matter, the Mpox Clade 2b variant is evolving and rapidly mutating at an unprecedented rate and is churning out numerous new lineages.
https://gisaid.org/mpox-variants-dashboard/
 
Among the many emerging questions is whether arthropods, such as mosquitoes or ticks, could be accidental reservoirs contributing to the virus’s spread. This Medical News delves into a recent questions and data presented by researchers that explores the possibility of arthropod involvement in the 2022 Mpox outbreak and highlights key findings from this fascinating research.
 
A Rising Concern: The Spread of Mpox
Mpox, caused by the monkeypox virus, has historically been linked to specific animal reservoirs, such as rodents and primates. However, the unprecedented nature of the 2022 outbreak, particularly its occurrence in non-endemic areas, prompted researchers to explore new potential transmission routes. As climate change impacts both human and animal habitats, "spillover" events, where viruses jump from animals to humans, become more likely. This article focuses on whether arthropods could play a role in spreading Mpox through such spillover events.
 
Arthropods, such as ticks, mosquitoes, and fleas, are already known to transmit various viruses that affect both animals and humans. For example, the Aedes aegypti mosquito is a notorious vector for diseases like chikungunya and dengue fever. Could similar arthropods act as reservoirs or secondary vectors in the case of Mpox?
 
The Role of Arthropods in Virus Transmission
Arthropod-borne infections, commonly referred to as vector-borne diseases, are a significant concern worldwide. These infections are spread by biting insects such as mosquitoes, ticks, and mites, and include diseases caused by viruses, bacteria, and parasites. In the context of Mpox, researchers are considering whether certain arthropods could transmit the virus after feeding on infected animals or humans.
 
The study in question specifically investigated whether arthropods could serve as re servoirs or play a role in secondary transmission. Given the virus’s potential for human-to-human transmission, researchers wanted to determine if infected arthropods might be facilitating the spread. A key point of focus was on species that are naturally exposed to Mpox reservoirs, such as mosquitoes that feed on humans, monkeys, and squirrels.
 
Genetic Mutations and Their Impact
One of the key findings of the study is that the 2022 Mpox virus exhibited a unique genetic structure, including specific mutations that could affect how the virus is transmitted. Researchers identified mutations in the viral genome, including in the immunogenic surface glycoprotein B21, which could have implications for how the virus spreads among humans and animals. Additionally, the study noted that 15 single nucleotide polymorphisms (SNPs) linked to human-to-human transmission exhibited mutation biases, suggesting that the virus is evolving.
 
These mutations raise concerns about the potential for increased transmission, particularly as genetic changes could make it easier for the virus to spread via different routes. The involvement of arthropods in the virus’s transmission could be a crucial factor in explaining the virus’s spread across multiple continents.
 
Arthropods and Mpox: The Evidence So Far
To date, no definitive evidence confirms that arthropods are primary vectors for Mpox. However, there are intriguing indicators that suggest a possible role. For example, antibodies against Mpox have been detected in a variety of species, including shrews and squirrels, which are known to interact with arthropods in their natural habitats.
 
The study found evidence of Mpox virus infection in rodents like Funisciurus and Cricetomys, raising questions about the role of insects in transmitting the virus between these animals and humans.
 
Moreover, the researchers noted that the RNA interference (RNAi) pathway, an antiviral defense mechanism in arthropods, plays a role in determining whether viruses like mpox can successfully replicate in these insects. If the virus can evade this immune response, it could replicate in specific arthropod species, potentially enabling them to transmit the virus to humans.
 
The Complexity of Mpox Transmission
The natural lifecycle of the Mpox virus is still not fully understood, and the potential role of arthropods adds another layer of complexity. According to the study, the lifecycle of Mpox involves a complex interplay between reservoir hosts (such as squirrels or shrews) and incidental species like humans and arthropods. In this scenario, arthropods might serve as incidental vectors, transmitting the virus after feeding on infected reservoir hosts.
 
Interestingly, researchers also noted parallels between Mpox and other poxviruses, such as the lumpy skin disease virus (LSDV), which is transmitted by mosquitoes and ticks. This suggests that while Mpox is primarily a zoonotic virus, arthropod involvement cannot be entirely ruled out without further investigation.
 
The Need for Further Research
The study concludes that more research is urgently needed to fully understand the various transmission routes of the Mpox virus. As the world continues to grapple with viral outbreaks, understanding how viruses spread - especially through unexpected means like arthropods - is crucial for preventing future pandemics.
 
Ongoing research is expected to focus on identifying whether specific arthropods serve as accidental reservoirs or secondary vectors in the Mpox lifecycle. Additionally, understanding the impact of climate change on virus spillover events will be key to preventing future outbreaks of zoonotic viruses.
 
Conclusion
In summary, while there is no conclusive evidence that arthropods are responsible for the 2022 Mpox outbreak, the study sheds light on a new area of research that could have significant implications for public health. The unique genetic mutations identified in the virus, coupled with its potential interaction with arthropods, suggest that the transmission of Mpox is more complex than previously thought.
 
As the world continues to face new viral threats, research into the potential role of arthropods in the spread of Mpox could help scientists develop better strategies for monitoring and controlling outbreaks. For now, the scientific community remains vigilant, and further investigation is needed to clarify the role of these insects in the transmission of the virus.
 
The study findings were published as a correspondence in the peer-reviewed journal: New Microbes and New Infections.
https://www.sciencedirect.com/science/article/pii/S2052297523000574
 
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https://www.thailandmedical.news/news/stop-calling-mpox-clade-2b-mild-young-argentinian-man-dies-from-so-called-mild-strain