Avian trichomonosis mortality events in band-tailed pigeons (Patagioenas fasciata) in California during winter 2014–2015

Abstract

Avian trichomonosis is an upper digestive tract disease of birds typically caused by the protozoan parasite Trichomonas gallinae. In California (U.S.A), trichomonosis is known to cause periodic epidemics in the Pacific Coast band-tailed pigeon (Patagioenas fasciata monolis), a migratory upland game bird. We summarize the mortality events that occurred during winter 2014–2015 including the duration, estimated mortality, pathology, and genetic identity of infecting parasites. Increased mortality was reported from locations in 25 counties between November 2014 and June 2015. Based on reports, carcasses received, wildlife rehabilitation center admissions, site visits, and regular monitoring by local personnel, total mortality was estimated at 18,440. At necropsy, birds had multiple coalescing lesions in the oral cavity involving the upper palate and/or around the tongue and glottis, esophagus, crop, and/or proventriculus. Birds collected from Contra Costa (63.9%; 30/47); Marin (75.0%; 6/8), San Mateo (46.7%; 14/30), and Santa Clara (35.0%; 37/106) counties were more likely to have lesions extending into their head involving muscle, sinuses, ear canals, eye sockets, and bone (χ2 = 62.9; df = 11; P < 0.001). Histopathologic findings included pharyngitis, esophagitis, myositis, and air sacculitis of the pneumatic bone of the skull. Mixed bacterial colonies were found multifocally at the fronts of the necrosis in six of the eleven birds examined histologically. Infecting trichomonads included T. gallinae subtype A2 (n = 5), un-typed T. gallinae (n = 4), mixed infection with T. gallinae subtype A2 and T. stableri (n = 1), and mixed infection with un-typed T. gallinae and T. stableri (n = 1). The winter 2014–2015 epidemic was the largest on record in terms of duration, locations, and birds affected. Infection dynamics may have been exacerbated by the drought in California. Increased monitoring of band-tailed pigeons is needed to understand the long-term impacts of large-scale mortality events on their population.

Genotypic diversity and epidemiology of Trichomonas gallinae in Columbidae: Insights from a comprehensive analysis

“…Trichomonas gallinae is a protozoan that mainly infects birds such as Columbiformes, Passeriformes, and Falconiformes ( Santos et al, 2019 ). It affects the upper digestive and respiratory tracts and potentially causes various levels of clinical symptoms ( Rogers et al, 2018 ). As a result, it can have significant implications for avian populations.…”

Evidence for strain-specific virulence ofTrichomonas gallinaein African columbiformes

“…Trichomonas gallinae is the causal agent of trichomoniasis, an emerging infectious disease linked to mortality in finches in the UK and Europe (Robinson et al ., 2010 ). Trichomonas gallinae is historically known as a parasite of columbids and raptors (Stabler, 1954 ), where it was generally thought to cause few clinical signs (but see Bunbury et al ., 2008 ) with the exception of occasional mortality events (Höfle et al ., 2004 ; Rogers et al ., 2018 ). However, the emergence of a novel strain (termed the type A strain; Gerhold et al ., 2008 ) linked to the finch epizootic (Lawson et al ., 2011 ) has been associated with mortality in adult and nestling European turtle doves Streptopelia turtur (Stockdale et al ., 2015 ), in which T. gallinae is found at very high prevalence in the UK (86%: Lennon et al ., 2013 ; 100%: Stockdale et al ., 2015 ) and Europe (93% from samples collected using standard T. gallinae sampling and culture techniques: Marx et al ., 2017 ).…”