The emergence and spread of finch trichomonosis in the British Isles

Abstract

Finch trichomonosis, caused by the protozoal parasite Trichomonas gallinae, was first recognized as an emerging infectious disease of British passerines in 2005. The first year of seasonal epidemic mortality occurred in 2006 with significant declines of greenfinch Carduelis chloris and chaffinch Fringilla coelebs populations. Here, we demonstrate that large-scale mortality, principally of greenfinch, continued in subsequent years, 2007 -2009, with a shifting geographical distribution across the British Isles over time. Consequent to the emergence of finch trichomonosis, the breeding greenfinch population in Great Britain has declined from ca 4.3 million to ca 2.8 million birds and the maximum mean number of greenfinches (a proxy for flock size) visiting gardens has declined by 50 per cent. The annual rate of decline of the breeding greenfinch population within England has exceeded 7 per cent since the initial epidemic. Although initially chaffinch populations were regionally diminished by the disease, this has not continued. Retrospective analyses of disease surveillance data showed a rapid, widespread emergence of finch trichomonosis across Great Britain in 2005 and we hypothesize that the disease emerged by T. gallinae jumping from columbiforms to passeriforms. Further investigation is required to determine the continuing impact of finch trichomonosis and to develop our understanding of how protozoal diseases jump host species.

Dual-pathogen etiology of avian trichomonosis in a declining band-tailed pigeon population

“…Unlike in Britain, where epidemic mortality events due to trichomonosis in breeding populations of finches occur in the late summer (Lawson et al, 2012;Robinson et al, 2010), transmission in California band-tailed pigeons followed a pattern similar to that of wood pigeons in Spain where T. gallinae infection prevalence is higher in adults (72.7%) than juveniles (20% or 34.6%, depending on location) (Villanùa et al, 2006) and outbreaks occur in winter and spring (Höfle et al, 2004). The high prevalence of infection in adults and the timing of mortality events in California band-tailed pigeons have strong implications for adult survival and recruitment potential.…”

“…The only previous reports of this genotype were in a live-caught disease-free Madagascar turtle dove sampled in Mahé, Seychelles and in a captive Budgarigar in Scotland that had trichomonosis lesions (Chi et al, 2013;Lawson et al, 2011a). The less common T. gallinae Fe-hydrogenase genotype in band-tailed pigeons, FeH subtype A1, is the etiologic agent of epidemic finch trichomonosis in Britain, where infections have lead to significant declines in greenfinch and chaffinch populations (Lawson et al, 2011a(Lawson et al, , 2012Robinson et al, 2010). The same genotype has also been found in non-passerine bird species in the U.K. including birds of prey and columbids (Chi et al, 2013).…”

“…Trichomonosis also is an emerging infectious disease of passerine birds that most likely become exposed to T. gallinae at artificial food and water sources shared by doves and pigeons (Forzán et al, 2010;Neimanis et al, 2010;Zadravec et al, 2012). Finch trichomonosis emerged in Great Britain in 2005, causing significant decline in breeding populations of greenfinches (Carduelis chloris) and chaffinches (Fringilla coelebs) (Lawson et al, 2012;Robinson et al, 2010). In 2008, the epidemic strain of T. gallinae from Great Britain spread into southern Fennoscandia, causing multiple trichomonosis mortality events in greenfinches and chaffinches over a two year period (Lawson et al, 2011a;Neimanis et al, 2010).…”

The finch epidemic strain of Trichomonas gallinae is predominant in British non-passerines

“…A clonal strain of T. gallinae has recently emerged as the cause of an epidemic disease of finches in Europe (Lawson et al 2011a, b). This emerging infectious disease was first reported in 2005 in Britain; since then unprecedented large-scale mortality, with consequent population declines, of greenfinches (Chloris chloris) has occurred Lawson et al 2012). Since 2007, trichomonosis has been reported in finch species in the Canadian Maritime provinces as well as in southern Fennoscandia and northern Germany (Peters et al 2009;Forzan et al 2010;Neimanis et al 2010;Lawson et al 2011a).…”

“…This emerging infectious disease was first reported in 2005 in Britain; since then unprecedented large-scale mortality, with consequent population declines, of greenfinches (Chloris chloris) has occurred Lawson et al 2012). Since 2007, trichomonosis has been reported in finch species in the Canadian Maritime provinces as well as in southern Fennoscandia and northern Germany (Peters et al 2009;Forzan et al 2010;Neimanis et al 2010;Lawson et al 2011a). Large-scale morbidity and mortality caused by T. gallinae infection continues to occur in British finch populations with an estimated 1·5 million greenfinches, representing c. 35% of the national population, having died of the disease (Lawson et al 2012) and with spillover to other British passerines having occurred Lawson et al 2011b).…”