Does the mosquito have more of a role in certain cancers than is currently appreciated? – The mosquito cocktail hypothesis

Cancer and mosquitoes - An unsuspected close connection

Cancer is a major public health issue and represents a significant burden in countries with different levels of economic wealth. In parallel, mosquito-borne infectious diseases represent a growing problem causing significant morbidity and mortality worldwide. Acknowledging that these two concerns are both globally distributed, it is essential to investigate whether they have a reciprocal connection that can fuel their respective burdens. Unfortunately, very few studies have examined the link between these two threats. This review provides an overview of the possible links between mosquitoes, mosquito-borne infectious diseases and cancer. We first focus on the impact of mosquitoes on carcinogenesis in humans including the transmission of oncogenic pathogens through mosquitoes, the immune reactions following mosquito bites, the presence of non-oncogenic mosquito-borne pathogens, and the direct transmission of cancer cells. The second part of this review deals with the direct or indirect consequences of cancer in humans on mosquito behaviour. Thirdly, we discuss the potential impacts that natural cancers in mosquitoes can have on their life history traits and therefore on their vector capacity. Finally, we discuss the most promising research avenues on this topic and the integrative public health strategies that could be envisioned in this context.

Occurrence, behaviour, and human exposure pathways and health risks of toxic geogenic contaminants in serpentinitic ultramafic geological environments (SUGEs): A medical geology perspective

Serpentinitic ultramafic geological environments (SUGEs) contain toxic geogenic contaminants (TGCs). Yet comprehensive reviews on the medical geology of SUGEs are still lacking. The current paper posits that TGCs occur widely in SUGEs, and pose human health risks. The objectives of the review are to: (1) highlight the nature, occurrence and behaviour of TGCs associated with SUGEs; (2) discuss the human intake pathways and health risks of TGCs; (4) identify the key risk factors predisposing human health to TGCs particularly in Africa; and (5) highlight key knowledge gaps and future research directions. TGCs of human health concern in SUGEs include chrysotile asbestos, toxic metals (Fe, Cr, Ni, Mn, Zn, Co), and rare earth elements. Human intake of TGCs occur via inhalation, and ingestion of contaminated drinking water, wild foods, medicinal plants, animal foods, and geophagic earths. Occupational exposure may occur in the mining, milling, sculpturing, engraving, and carving industries. African populations are particularly at high risk due to: (1) widespread consumption of wild foods, medicinal plants, untreated drinking water, and geophagic earths; (2) weak and poorly enforced environmental, occupational, and public health regulations; and (3) lack of human health surveillance systems. Human health risks of chrysotile include asbestosis, cancers, and mesothelioma. Toxic metals are redox active, thus generate reactive oxygen species causing oxidative stress. Dietary intake of iron and geophagy may increase the iron overload among native Africans who are genetically predisposed to such health risks. Synergistic interactions among TGCs particularly chrysotile and toxic metals may have adverse human health effects. The occurrence of SUGEs, coupled with the several risk factors in Africa, provides a unique and ideal setting for investigating the relationships between TGCs and human health risks. A conceptual framework for human health risk assessment and mitigation, and future research direction are highlighted.

Mosquitoes, Infectious Diseases, and Cancer: A Connection to Study?

Mosquitoes (Diptera: Culicidae) are vectors of pathogens and parasites of great medical and veterinary relevance. The possible association between mosquitoes, infectious diseases, and cancer has been investigated. Despite its potential importance, there is a severe lack of research data on the topic. Herein, current knowledge, tenuous links, and related challenges on the topic were examined, grouping information under four major hypotheses. The first hypothesis is that the infection of mosquito-vectored parasites, with special reference to Plasmodium spp., may lead to cancer. The International Agency for Research on Cancer stated that being infected by Plasmodium falciparum malaria in holoendemic areas is probably carcinogenic to humans (group 2A), considering that P. falciparum infection is able to reactivate the Epstein–Barr virus, leading to endemic Burkitt lymphoma. Also, malaria was recently associated with a cancer incidence increase in the United States. The second hypothesis is that cancer may be spread directly through mosquito bites: Aedes mosquitoes transfer viable tumor cells among vertebrate hosts, even if no plausible mechanisms for these cells to develop cancer into the new host are known. As the third hypothesis, mosquito bites may lead to hypersensitivity, resulting in cancer. Hypersensitivity stimulated by mosquito bites links allergy, oncogenesis, and the Epstein–Barr virus, causing Burkitt lymphoma. One may argue that pathogens transmitted by mosquitoes, such as viruses, may be carcinogenic. However, no detailed research evidences are available to substantiate this last hypothesis. However, despite the intriguing hypotheses outlined above, there is a severe lack of data showing cancer development in organisms exposed to mosquitoes transmitting parasites or pathogens. According to One Health criteria, this benchmark is aimed to outline major questions on this public health issue, stressing the need of multidisciplinary research and discussion.

Puzzling and ambivalent roles of malarial infections in cancer development and progression

Scientific evidence strongly suggests that parasites are directly or indirectly associated with carcinogenesis in humans. However, studies have also indicated that parasites or their products might confer resistance to tumour growth.Plasmodiumprotozoa, the causative agents of malaria, exemplify the ambivalent link between parasites and cancer. Positive relationships between malaria and virus-associated cancers are relatively well-documented; for example, malaria can reactivate the Epstein-Barr Virus, which is the known cause of endemic Burkitt lymphoma. Nevertheless, possible anti-tumour properties of malaria have also been reported and, interestingly, this disease has long been thought to be beneficial to patients suffering from cancers. Current knowledge of the potential pro- and anti-cancer roles of malaria suggests that, contrary to other eukaryotic parasites affecting humans,Plasmodium-related cancers are principally lymphoproliferative disorders and attributable to virus reactivation, whereas, similar to other eukaryotic parasites, the anti-tumour effects of malaria are primarily associated with carcinomas and certain sarcomas. Moreover, malarial infection significantly suppresses murine cancer growth by inducing both innate and specific adaptive anti-tumour responses. This review aims to present an update regarding the ambivalent association between malaria and cancer, and further studies may open future pathways to develop novel strategies for anti-cancer therapies.