Preliminary molecular detection of influenza RNA in synanthropic cockroaches from shiraz, Iran

Cockroaches are recognized as significant mechanical vectors for a wide spectrum of pathogens, posing a considerable public health risk. Their habitation in unsanitary environments and promiscuous feeding habits allow them to acquire and disseminate bacterial agents, viruses-including poliovirus and influenza-and protozoan parasites such as Microsporidia and Giardia, as well as the eggs of parasitic worms. This study investigates the potential of cockroaches to mechanically carry influenza viruses, a subject that remains underexplored despite the significant global burden of influenza. During the seasonal peak of influenza activity, a total of 322 cockroaches were collected from various high-risk locations in Shiraz, Iran, including hospital premises, university dormitories, and academic faculties. The sampling targeted two predominant species, Blattella germanica and Periplaneta americana, captured from diverse microhabitats such as kitchens, rooms, and sewers. Using a highly sensitive real-time PCR methodology, which targeted the conserved matrix genes of influenza A and B viruses, both external body surface washes and internal digestive tract samples were analyzed. The results confirmed the presence of influenza A virus RNA in four external surface samples of Blattella germanica and in two internal digestive tract samples of Periplaneta americana. Notably, the majority of positive samples (5 out of 6) were for influenza type A, with one sample positive for influenza type B. The overall detection rate was low (1.86%, 6/322), these findings demonstrate that cockroaches in urban environments can indeed harbor influenza virus RNA, either externally on their bodies or internally within their digestive systems. This molecular detection highlights the presence of viral RNA, suggesting possible mechanical carriage. However, the detection of RNA alone does not confirm the presence of viable, infectious virus, which is a key limitation of this study. Given their intimate association with human dwellings and food sources, this molecular evidence indicates potential but unconfirmed route for mechanical carriage that warrants further investigation. Crucially, our study design cannot assess transmission risk. Consequently, the findings underscore the necessity for additional comprehensive studies to assess viral viability and to elucidate the potential, yet unproven, role of cockroaches in the epidemiology of influenza.