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Title: Persistence of exotic Newcastle disease virus (ENDV) in laboratory infected Musca domestica and Fannia canicularis

Author
item CHAKRABARTI, SEEMANTI - UNIV CALIF, RIVERSIDE
item King, Daniel
item CARDONA, CAROL - UNIV CALIF, DAVIS
item GERRY, ALEC - UNIV CALIF, RIVRESIDE

Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/21/2008
Publication Date: 10/2/2008
Citation: Chakrabarti, S., King, D.J., Cardona, C.J., Gerry, A.C. 2008. Persistence of exotic Newcastle disease virus (ENDV) in laboratory infected Musca domestica and Fannia canicularis. Avian Diseases. 52:375-379.

Interpretive Summary: The primary mode of transmission of exotic Newcastle disease virus (ENDV) is from infected to healthy birds. ENDV was recovered from samples of flies collected from premises that contained ENDV infected backyard chickens. To assess the ability of house flies (Musca domestica) and little house flies (Fannia canicularis) to acquire and retain ENDV, flies were allowed to feed on a food source containing ENDV for 24 hours and samples of flies were collected daily thereafter for virus isolation. Sampled flies were dissected to determine the amount of virus that could be recovered from the gut compared to that recovered from external body parts contaminated while feeding on the infective food source. Infective virus was recovered primarily from the fly gut rather than external body parts and enough virus persisted in the gut of both fly species to maintain a chicken infectious dose for up to four days. Flies feeding on manure from infected chickens could therefore potentially disperse virus to nearby premises, a biosecurity concern. Fly control should be included as a component of biosecurity especially during an eradication program.

Technical Abstract: House flies (Musca domestica) and little house flies (Fannia canicularis) were examined for their ability to take up and harbor a velogenic strain of exotic Newcastle disease virus (family Paramyxoviridae, genus Avulavirus, ENDV). Laboratory reared flies were allowed to feed on evaporated milk containing ENDV at a virus concentration of 10^8.3 egg infectious doses /0.1 ml. Flies exposed to this infectious food source for 24 h became transiently infected with virus. Consumed virus persisted predominantly in the mid and hindgut with relatively little virus isolated from the remainder of the fly body. Virus persisted similarly in both fly species, with a maximum ENDV titer of 10^5.98/fly for house fly and 10^4.78/fly for little house fly at 1 day post-exposure with titers decreasing on subsequent days to 10^2.38/fly for house fly and >=1/fly for little house fly at 5 days post-exposure. Both fly species maintained viral titers greater than the infective dose for a susceptible chicken for up to 4 days post-exposure to the infectious food source. The decrease in viral titer over time was significantly explained by logistic regression for both fly species (p<0.05). The slope of the regression line was not different for the two fly species (p< 0.05) indicating a similar rate of virus loss.