Abstract
This is the first report of SARS-CoV-2 detection on field-collected Musca domestica housefly surface and tissue samples using the high-sensitive PCR assay which suggests the possible insect-borne transmission. The study was conducted in Shiraz city, southern Iran, in May and Jun 2020. Adult flies were sampled at the outdoor areas of two hospitals treating COVID-19 patients. Fly samples were first washed twice to remove the insect surface attached to SARS-CoV-2 virions. After that, the disinfected fly samples were homogenized. Fly surface washout and homogenate samples were tested using Taq Man real-time PCR assay for the SARS-CoV-2 virus. In a total of 156 houseflies, 75% of samples from the body washout samples were positive for SARS-CoV-2. Strikingly, 37% of the homogenized specimens were positive for the SARS-CoV-2, suggesting the possible infection of the insects or uptake of the virion to the insect metabolism. The other possibility is the houseflies up took the blood or blood fluids of the patients and the RNA of the SARS-CoV-2 survived in the insect body without replicating. Our preliminary findings suggest that the houseflies could transmit SARS-CoV-2 as a mechanical or biological vector especially during the warm seasons while increasing the population and activity of houseflies.
Highlights
This is the first report of SARS-CoV-2 detection on field-collected Musca domestica housefly surface and tissue samples using the high-sensitive PCR assay which suggests the possible insect-borne transmission
Our preliminary findings suggest that the houseflies could transmit SARS-CoV-2 as a mechanical or biological vector especially during the warm seasons while increasing the population and activity of houseflies
The possibility of transmitting viral diseases that cause acute respiratory infections in humans and animals has been studied in different parts of the world and the possibility of mechanical transmission of these viruses by some species of insects has been p roven[4,5,6,7,8,9,10,11,12,13,14]
Summary
This is the first report of SARS-CoV-2 detection on field-collected Musca domestica housefly surface and tissue samples using the high-sensitive PCR assay which suggests the possible insect-borne transmission. The possibility of transmitting viral diseases that cause acute respiratory infections in humans and animals has been studied in different parts of the world and the possibility of mechanical transmission of these viruses by some species of insects has been p roven[4,5,6,7,8,9,10,11,12,13,14]. The housefly (Musca domestica) is a non-blood feeding insect of the order Diptera that can be a mechanical vector of many diseases, especially nosocomial infections, due to its unique behavioral and nutritional mechanisms This insect can transmit pathogens mechanically to humans in four main ways: (1) adherence of pathogens to its body through the legs, wings, and surface of the abdomen, etc. We know from previous studies that, the housefly might suck the liquids such as sweat, or fecal that contains the SARS-CoV-2 and the insect might contain the RNA only
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