Table 1.

Evidence for incrimination of flies as vectors of trachoma

Summary of Barnett’s Criteria	Evidence for accepting criterion
I Effective contact under natural conditions	(A) Frequent fly eye contacts shown in the Gambia (3 every 15 minutes) 4
	(B) Children with infective discharge had double the fly eye contacts 4
	(C) Greater than 90% of fly eye contacts were Musca sorbens 4
II Convincing temporal and geographic association of the presence of vector and infection	(A) Musca sorbens recorded in areas of Australia, Africa, and the Middle East affected by trachoma 7
	(B) High fly densities associated with outbreaks of trachoma 7
	(C) Pilot interventional study showed a significant reduction in trachoma following decrease in fly prevalence and fly eye contacts after pesticide application 6
III Vector harbours pathogen	?
IV Experimental transmission	Flies shown capable of transmitting Chlamydia spp between guinea pigs under experimental conditions 8