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COVID-19 VIRUS DISEASE

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A corona virus that has been named Covid-19 appeared in central China in late 2019 and subsequently spread to many parts of the world to cause a widespread pandemic. By May 2020 transmission was determined to be primarily through human contact, but no studies have been made to determine if insect vectors might also be involved.

It is well established that the mosquito genera Aedes and Culex are vectors of virus diseases that affect humans with symptoms similar to those of Covid-19. Because many species in these and other mosquito genera are able to reproduce in temporary pools of water they may be considered as primary suspect candidates for transmission of Covid-19. Studies would involve identifying non-human alternate hosts such as birds, rodents and bats, the latter being suspect as an original source of the disease.

The insect family Ceratopogonidae and genera Culicoides and Leptoconops are also known to spread virus diseases of humans. These are very tiny insects whose populations often soar to thousands of individuals in urban and wild areas. They breed in soils containing organic matter and are extremely difficult to control. Unlike the larger mosquito group, these flies are small enough to pass through screened doors and windows. Repellents applied repeatedly to skin are the only effective controls.

As of September 2020 many discussions of these flies may be found on the Internet. An example is a posting by Franziska Sick et. al. entitled "Culicoides Biting Midges--Underestimated Vectors for Arboviruses of Public Health and Veterinary Importance. The authors explain that Culicoides  biting midges, are small hematophagous dipterans, which serve as putative vectors of multiple arboviruses of veterinary and public health importance. Despite its relevance in disease spread, the ceratopogonid genus Culicoides is still a neglected group of species, mainly because the major human-affecting arboviruses are considered to be transmitted by mosquitoes. However, when a pathogen is detected in a certain vector species, a thorough search for further vectors often remains undone and, therefore, the relevant vector species may remain unknown. Furthermore, for many hematophagous arthropods, true vector competence is frequently only suspected and not experimentally examined. Thus, the authors illuminate the general impact of Culicoides biting midges and summarize the knowledge about biting midge-borne disease agents using the order Bunyavirales, the largest and most diverse group of RNA viruses, as an example. When considering only viruses evidentially transmitted by Culicoides midges, the Simbu serogroup (genus Orthobunyavirus) is probably the most important group within the virus order. Its members are of great veterinary importance, as a variety of simbuviruses, e.g., the species Akabane orthobunyavirus or Schmallenberg orthobunyavirus, induces severe congenital infections in pregnant animals. The major zoonotic representative of this serogroup occurs in South and Central America and causes the so-called Oropouche fever, an acute febrile illness in humans.