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ARS Home » Southeast Area » Gainesville, Florida » Center for Medical, Agricultural and Veterinary Entomology » Mosquito and Fly Research » Research » Publications at this Location » Publication #308154
Title: Enhancement of the Musca domestica hytrosavirus infection with orally delivered reducing agents

Author
item BOUCIAS, D - University Of Florida
item BANISZEWSKI, J - University Of Florida
item PROMPIBOON, P - Bionet-Asia Co, Ltd (VACCINE PLANT)
item LIETZE, V - University Of Florida
item Geden, Christopher - Chris

Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2014
Publication Date: 1/1/2015
Citation: Boucias, D., Baniszewski, J., Prompiboon, P., Lietze, V., Geden, C.J. 2015. Enhancement of the Musca domestica hytrosavirus infection with orally delivered reducing agents. Journal of Invertebrate Pathology. 124:35-43.

Interpretive Summary: House flies and stable flies are important pests associated with animals and humans and transmit a wide array of disease organisms. Biological control is an important element in successful fly management, bust most of the research in this area has focused on natural enemies of the larval and pupal stages. An effective biocontrol agent against the adult fly would be a welcome addition to the tools available for fly management. One possible control agent for adult flies is salivary gland hypertrophy virus (SGHV). Flies acquire the virus by feeding in areas where infected flies have deposited virus particles of food items. When a female fly becomes infected she is longer able to produce eggs. Previous attempts to add virus to fly food to develop an infective bait have been disappointing because of the fly’s ability to surround ingested food with a protective sheath (the peritrophic matrix) that is largely impervious to microbes of all kinds. In this study, scientists at the University of Florida and USDA’s Center for Medical, Agricultural, and Veterinary Entomology (Gainesville, FL) attempted to increase the susceptibility of the flies to SGHV by first allowing them to feed on two chemicals that can interfere with the biochomistry of the peritrophic matrix. Both chemicals increased the susceptibility of the flies to the virus by 10 to 20-fold. If technological challenges can be overcome, the results could lead to infective baits with much higher potency than any that have been tried to date.

Technical Abstract: House flies (Musca domestica L.) throughout the world are infected with the salivary gland hypertrophy virus MdSGHV (Hytrosaviridae). Although the primary route of infection is thought to be via ingestion, flies that are old enough to feed normally are resistant to infection per os, suggesting that the peritrophic matrix (PM) is a barrier to virus transmission. Histological examination of the peritrophic matrix of healthy flies revealed a multilaminate structure produced by midgut cells located near the proventriculus. SEM revealed the PM to form a confluent sheet surrounding the food bolus with pores/openings less than 10 nm in diameter. TEM revealed the PM to be multilayered, varying in width from 350-900 nm, and generally thinner in male than female flies. When flies were fed on the reducing agents dithiothetriol (DTT) or tris (2-caboxyethyl) phosphine hydrochloride (TCEP) for 48 hours before per os exposure to the virus, infection rates increased 10- to 20-fold compared with flies that did not receive the reducing agent treatments. PM’s from flies treated with DTT and TCEP displayed varying degrees of disruption, particularly in the outer layer, and lacked the electron-dense inner layer facing the ectoperitrophic space. Both drugs were somewhat toxic to the flies, resulting in >40% mortality at doses greater than 10 mM (DTT) or 5 mM (TCEP). DTT increased male fly susceptibility (55.1% infected) more than females (7.8%), whereas TCEP increased susceptibility of females (42.9%) more than males (26.2%). The cause for the sex differences in response to oral exposure to the reducing agents is unclear. Exposing flies to food treated with virus and the reducing agents at the same time, rather than pretreating flies with the drugs, had no effect on susceptibility to the virus. Presumably, the reducing agent disrupted the enveloped virus and acted as a viricidal agent. In summary, it is proposed that the reducing agents can influence integrity of the PM barrier in a manner that increases the susceptibility of flies to infection by MdSGHV.