Mosquitoes are widely known to transmit diseases all over the world. The most famous of these diseases include dengue, yellow fever, and Zika. However, how much do we know about the capacity of these vectors to transmit cancer cells? As a relatively small virus causes dengue, can we say that the same mosquito can carry and transmit larger cells? We will answer these questions by going through the few research available regarding the correlation between cancer and mosquitoes. Additionally, in knowing these connections, we will also discuss tips on the prevention and control of mosquitoes. This measure should be necessary as even with or without the threat of cancer, the diseases mosquitoes transmit are already well-established.
Mosquito as a Vector
Mosquitoes are the most crucial arthropod vectors in medical studies. It is the cause of detrimental vector-borne diseases such as dengue, malaria, chikungunya, and Zika. Accordingly, different kinds of mosquitoes transmit different kinds of diseases. In terms of the genus of a mosquito, these are some of the diseases they can cause:
- Aedes: chikungunya, dengue, lymphatic filariasis, rift valley fever, yellow fever, zika
- Anopheles: lymphatic filariasis, malaria
- Culex: lymphatic filariasis, West Nile fever, Japanese encephalitis
Aside from filariasis and malaria, viruses cause all of the mentioned diseases above. Compared to the cells which cause cancer, viruses are much smaller. Similarly, the “spores” from parasites that infect mosquitoes in filariasis and malaria are much smaller than a cell. So how is it possible that cancer cells can enter mosquitoes and even transmit to other humans?
Suspicions on Mosquito Cancer Transmission
The idea of mosquito transmission of cancer came from a study more than 60 years ago. Scientists observed a 5% to 10% possibility of transmitting reticulum cell sarcoma from one hamster to another. They noted that 2% of Aedes aegypti mosquitoes transmitted these tumor cells. The mosquitoes were able to contain these tumor cells for around 8 hours.
Another older study supported these findings. However, scientists in the medical community attempted no further studies regarding this direct kind of transmission. We have no information on the explanation regarding this drought in this kind of research. While more and more review articles are suggesting more research on the direct transmission of tumor cells, researchers have come up with other explanations for the relationship between mosquito-borne diseases and cancer.
Through a succession of research regarding mosquitoes and cancer, scientists are now focusing on the indirect effects of mosquito-borne diseases on cancer. They are now looking into correlations between the diseases and cancer while investigating the specific pathways at work. These discoveries would help us understand other risks of cancer developments due to mosquito-triggered mechanisms.
Existing Research on Mosquitoes and Cancer
Admittedly, researchers are aware that there are few studies on the relationship between mosquitoes and cancer. Most review articles point out the need for future research as urgently needed due to the rise of mosquito-borne diseases. There could be yet unknown repercussions of these diseases in terms of cancer developments. As of today, the following studies below have some of the information we have on mosquito and cancer research.
A clear solution to finding out the relationship between mosquitoes and cancer would be to examine a mosquito-borne disease and its correlation with a type of cancer. We can see this in a 2010 study investigating cases of malaria and cancer incidence in 50 US states. Researchers analyzed the comorbidities of cancer mortalities and saw a significant association between malaria and brain cancer mortalities.
The researchers hypothesize that this association may be due to the capacity of the parasite from malaria to induce a suppression mechanism in the host’s immune system. Specifically, the parasite’s infection may suppress the adaptive immune response to heterologous antigens. This in turn causes the supposed suppression of the immune system against cancer cells.
Additionally, scientists are also noticing the capacity of mosquito bites to stimulate hypersensitivity. This can lead to high fever, malaise, and liver problems. Ultimately, this cascade of conditions can also cause immunosuppression and then lead to lymphoma, allergies, and mutations in normal cells into cancer.
Currently, this hypersensitivity and immunosuppression explanation is one of the four major hypotheses scientists use to describe the relationship between mosquito-borne diseases and cancer. We can see all these hypotheses in this 2019 article reviewing the several connections between mosquitoes, infectious diseases, and cancer.
If we review everything we have discussed so far, we have actually discussed two of the hypotheses already. The other hypothesis is the explanation using direct transmission of tumor cells through mosquitoes.
The third hypothesis relies on the preceding research detailing the carcinogenic role of mosquito-vectored parasites. As previously discussed, one of them is malaria with the Plasmodium falciparum. This hypothesis stems from the ability of different parasites to induce carcinogenesis. These parasites include Schistosoma haematobium, Opisthorchis viverrini, and Clonorchis sinensis.
The World Health Organization recognizes that infection with P. falciparum as “probably carcinogenic to humans”. Correlation studies also support this hypothesis due to the high incidence of Burkitt lymphoma in malaria-endemic areas.
Finally, scientists also suggest that there may be other carcinogenic pathogens brought on by mosquitoes that we have yet to discover. These factors include pathogens and substances coming from the different breeding places the mosquitoes go through. However, along with the direct transmission of tumor cells, this hypothesis lacks the research data to hold ground. This is precisely why the article encourages examining this mosquito and cancer relationship further.
Mosquito Prevention Control
Although this discussion seems to suffer from a lack of research data, there is no doubt that mosquitoes are still dangerous as vectors. They carry tons of diseases with them, and as discussed, may cause hypersensitivity and compromise our immune system. In line with this, here are some common tips to prevent these hazardous threats:
- Never leave containers to hold even the smallest pools of water. Some household items prone to small pools of water include tires, buckets, cans, flower pots, and saucers.
- Regularly apply mosquito repellants during summer, especially at night.
- Wear light-colored clothing, preferably long-sleeved.
- Install screens for your windows and doors.
- Check for mosquito-endemic areas when traveling and plan ahead for them. You may use CDC’s Traveler’s Health Guide.