Evaluation of domestic pigeons as sentinels for detecting arbovirus activity in southern California.

Flocks of sentinel domestic pigeons (Columbia livia) detected increases in St. Louis encephalitis (SLE) and western equine encephalomyelitis (WEE) virus activity in southern California concurrently with flocks of sentinel chickens. However, occasional low-titered, transient seroconversions to both WEE and SLE viruses also occurred in pigeons during periods when virus activity was not detected by seroconversions in sentinel chickens, by virus isolation from Culex mosquitoes, or by human disease. Moreover, SLE virus seroconversions detected in pigeons by a hemagglutination inhibition (HI) test frequently could not be confirmed either by a plaque-reduction neutralization test (PRNT) on the same sera, or by an HI test on the next monthly serum sample from the same bird. Experimental infection studies, in which pigeons were inoculated subcutaneously with SLE (SOUE 16-84) virus, confirmed that pigeons developed low-titered and transient HI antibodies that were detectable infrequently by PRNT. In contrast, experimental infection with WEE (BFS 1703) virus produced elevated antibody responses that were detectable by HI for 8-12 weeks and by PRNT for at least 25 weeks. Pigeons infected with SLE virus rarely developed detectable viremias, whereas most birds infected with WEE virus developed viremias on postinfection day 1 that persisted for two or three days. Host-preference studies indicated that pigeons were less attractive as bait in lard can traps to host-seeking Culex mosquitoes than were chickens, and that blood-engorged Culex females collected near sentinel locations fed more frequently upon galliform than columbiform birds. Collectively, these results indicated that sentinel pigeons would not provide an adequate replacement for sentinel chickens to monitor WEE or SLE viruses, and would be a dead-end host for SLE virus.