Synanthropic Flies—A Review Including How They Obtain Nutrients, along with Pathogens, Store Them in the Crop and Mechanisms of Transmission

Abstract

An attempt has been made to provide a broad review of synanthropic flies and, not just a survey of their involvement in human pathogen transmission. It also emphasizes that the crop organ of calliphorids, sarcophagids, and muscids was an evolutionary development and has served and assisted non-blood feeding flies in obtaining food, as well as pathogens, prior to the origin of humans. Insects are believed to be present on earth about 400 million years ago (MYA). Thus, prior to the origin of primates, there was adequate time for these flies to become associated with various animals and to serve as important transmitters of pathogens associated with them prior to the advent of early hominids and modern humans. Through the process of fly crop regurgitation, numerous pathogens are still readily being made available to primates and other animals. Several studies using invertebrate-derived DNA = iDNA meta-techniques have been able to identify, not only the source the fly had fed on, but also if it had fed on their feces or the animal's body fluids. Since these flies are known to feed on both vertebrate fluids (i.e., from wounds, saliva, mucus, or tears), as well as those of other animals, and their feces, identification of the reservoir host, amplification hosts, and associated pathogens is essential in identifying emerging infectious diseases. New molecular tools, along with a focus on the crop, and what is in it, should provide a better understanding and development of whether these flies are involved in emerging infectious diseases. If so, epidemiological models in the future might be better at predicting future epidemics or pandemics.

The Movement of Pathogen Carrying Flies at the Human–Wildlife Interface

“…risk (Graczyk et al 2001;Calibeo-Hayes et al 2003). The synanthropic flies implicated in increasing disease risk encompass a taxonomically broad and extremely species rich group of Diptera, including a rich diversity from the families Calliphoridae, Sarcophagidae and Muscidae (Greenberg 1973;Stoffolano 2022).…”

The Entomopathogenic Fungus Conidiobolus coronatus Has Similar Effects on the Cuticular Free Fatty Acid Profile of Sensitive and Resistant Insects

“…However, the immune response of C. vicina is generally weak, characterized by hemocytes with low phagocytic and encapsulating activity, an inefficient polyphenol oxidase (PO) system and a hemolymph with low lysozyme activity [15]. Therefore, an effective cuticle is essential for protecting C. vicina larvae, which, given their lifestyle and habitat, are constantly exposed to pathogens [15,64,65]. In contrast, Galleria mellonella larvae, despite having both humoral and cellular components in their immune systems, are vulnerable to C. coronatus infection because of their relatively thin and easily degraded cuticle [15,46].…”