Evaluation of the House Fly Musca domestica as a Mechanical Vector for an Anthrax

Antonio Fasanella,Silvia Scasciamacchia,Rosanna Adone,Giuliano Garofolo,Annunziata Giangaspero,Elvira Tarsitano,Frank R Deleo

doi:10.1371/journal.pone.0012219

Abstract

Anthrax is a disease of human beings and animals caused by the encapsulated, spore-forming, Bacillus anthracis. The potential role of insects in the spread of B. anthracis to humans and domestic animals during an anthrax outbreak has been confirmed by many studies. Among insect vectors, the house fly Musca domestica is considered a potential agent for disease transmission. In this study, laboratory-bred specimens of Musca domestica were infected by feeding on anthrax-infected rabbit carcass or anthrax contaminated blood, and the presence of anthrax spores in their spots (faeces and vomitus) was microbiologically monitored. It was also evaluated if the anthrax spores were able to germinate and replicate in the gut content of insects. These results confirmed the role of insects in spreading anthrax infection. This role, although not major, given the huge size of fly populations often associated with anthrax epidemics in domestic animals, cannot be neglected from an epidemiological point of view and suggest that fly control should be considered as part of anthrax control programs.

Highlights

Anthrax is a human and animal disease caused by the encapsulated, large rod, and spore-forming Bacillus anthracis
Detection of B. anthracis in infected fly spots Groups of M. domestica were fed on B. anthracis-infected rabbit carcasses for 2, 4, 6, or 8 h, and the ability of B. anthracis to grow from fly spots was evaluated every 2 h (Figure 1)
B. anthracis-infected carcasses represent the major source of replicating anthrax cells, vegetative organisms, and spores

Summary

Introduction

Anthrax is a human and animal disease caused by the encapsulated, large rod, and spore-forming Bacillus anthracis. The bacteria grow vegetatively within body tissues of the host, with sporulation occurring when vegetative organisms are exposed to the atmosphere. Animal anthrax primarily affects herbivore ruminants, such as cattle, sheep, and goats, which are the most susceptible animal hosts. The disease occurs following ingestion of soil-borne anthrax spores. Human anthrax usually results from a cutaneous infection caused from the handling of infected animal products or, in rare cases, by ingesting or inhaling spores from contaminated animal products [1]. Anthrax spores may spread within a geographic region through water, insects, wild animals, birds, and contamination from body fluids of infected animals [2,3]

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