Eastern equine encephalitis virus in birds: relative competence of European starlings (Sturnus vulgaris).

Abstract

Abstract. To determine whether eastern equine encephalitis (EEE) virus infection in starlings may be more fulminant than in various native candidate reservoir birds, we compared their respective intensities and durations of viremia. Viremias are more intense and longer lasting in starlings than in robins and other birds. Starlings frequently die as their viremia begins to wane; other birds generally survive. Various Aedes as well as Culiseta melanura mosquitoes can acquire EEE viral infection from infected starlings under laboratory conditions. The reservoir competence of a bird is described as the product of infectiousness (proportion of feeding mosquitoes that become infected) and the duration of infectious viremia. Although starlings are not originally native where EEE is enzootic, a starling can infect about three times as many mosquitoes as can a robin.

Experimental Inoculation of House Sparrows (Passer Domesticus) With Buggy Creek Virus

“…Our results for BCRV in house sparrows suggest a viremia profile largely consistent with that reported for other alphaviruses, in which virus is most easily detected in blood for typically 1-2 days after initial infection (Hardy and Reeves, 1990;Komar et al, 1999;Lindströ m and Lundströ m, 2000;Kramer et al, 2002;Reisen et al, 2003). That all but one inoculated sparrow seroconverted suggests that our experimental infections were successful, but, perhaps surprisingly, only one of six sparrows showed high levels of viremia, and four of the six inoculated sparrows showed no evidence of viremia by plaque assay.…”

“…Two of the CONTROL birds (A1398, CDC0005) with evidence of BCRV RNA in blood (by RT-PCR) were each housed with one of the two inoculated individuals that showed BCRV viremia by plaque assay (birds A1397 and CDC0004, respectively), and the other positive CONTROL bird (A1399) was housed with an inoculated individual (3575) that was positive by RT-PCR. That we found evidence of plaque-forming virus in nasopharyngeal swabs from inoculated individuals suggests that infectious BCRV can be transmitted orally among sparrows, and perhaps the control birds were exposed through use of watering or food trays shared with inoculated birds or through other contact with virus shed orally (Holden, 1955;Komar et al, 2003). The presence of BCRV in skin also provides another potential mechanism of bird-to-bird transmission, if individuals peck each other during aggressive interactions and potentially break the skin.…”

“…This may reflect in general the greater sensitivity of RT-PCR to detect the presence of viral RNA (Kramer et al, 2002). Birds were more likely to be positive for BCRV by RT-PCR on days 6-15 than on days 1-5, a perplexing result given that virus titers in most bird species are highest immediately after infection (e.g., Hardy and Reeves, 1990;Komar et al, 1999;Kramer et al, 2002;Reisen et al, 2003). The RT-PCR detections through day 15 may simply indicate low levels of virus (or viral RNA) in blood that are not sufficiently strong to be detectable by plaque assay or, more importantly, sufficiently strong or viable to infect invertebrate vectors.…”

“…For eastern (EEEV) and western equine encephalomyelitis (WEEV) viruses, for example, a variety of mostly passerine bird species exhibit sufficiently elevated viremia levels to infect mosquitoes for typically the first 1-2 days after inoculation, but viremias are frequently undetectable beyond 3 days postinoculation (Hardy and Reeves, 1990;Komar et al, 1999;Kramer et al, 2002;Reisen et al, 2003). Interestingly, the introduced, nonnative European starling (Sturnus vulgaris) was a more effective amplifying host (with higher levels of viremia) for the alphavirus EEEV in Massachusetts than were several native bird species tested (Komar et al, 1999).…”

Pathology and Virus Detection in Tissues of Nestling House Sparrows Naturally Infected With Buggy Creek Virus (Togaviridae)

“…Eastern equine encephalitis virus and Highlands J virus (HJV), an alphavirus in the Western equine encephalomyelitis virus (WEEV) complex, cause clinical illness and death in pen-raised Chukars (Alectoris chukar; Ranck et al, 1965) and domestic turkeys . Experimental infection studies with wild passerine birds and alphaviruses generally have shown low mortality and transient to no morbidity in adults of most species (Komar et al, 1999;Reisen et al, 2003;Huyvaert et al, 2008), although response to experimental infection can vary by species. For example, European Starlings (Sturnus vulgaris) inoculated with EEEV died more frequently than other species tested (Komar et al, 1999), and White-crowned Sparrows (Zonotrichia leucophrys), Goldencrowned Sparrows (Zonotrichia atricapilla), Tricolored Blackbirds (Agelaius tricolor), and Red-winged Blackbirds (Agelaius phoeniceus) died when inoculated with passaged strains of WEEV, whereas other passerines, including House Sparrows (Passer domesticus), were unaffected by experimental virus infection (Hardy and Reeves, 1990).…”