Epidemiology of protozoan and helminthic parasites in wild passerine birds of Britain and Ireland

Avian endoparasites play important roles in conservation, biodiversity and host evolution. Currently, little is known about the epidemiology of intestinal helminths and protozoans infecting wild birds of Britain and Ireland. This study aimed to determine the rates of parasite prevalence, abundance and infection intensity in wild passerines. Fecal samples (n = 755) from 18 bird families were collected from 13 sites across England, Wales and Ireland from March 2020 to June 2021. A conventional sodium nitrate flotation method allowed morphological identification and abundance estimation of eggs/oocysts. Associations with host family and age were examined alongside spatiotemporal and ecological factors using Bayesian phylogenetically controlled models. Parasites were detected in 20.0% of samples, with corvids and finches having the highest prevalences and intensities, respectively. Syngamus (33%) and Isospora (32%) were the most prevalent genera observed. Parasite prevalence and abundance differed amongst avian families and seasons, while infection intensity varied between families and regions. Prevalence was affected by diet diversity, while abundance differed by host age and habitat diversity. Infection intensity was higher in birds using a wider range of habitats, and doubled in areas with feeders present. The elucidation of these patterns will increase the understanding of parasite fauna in British and Irish birds.

Protozoan and Helminth Infections of Aviary-Reared Alectoris rufa (Galliformes: Phasianidae) before Releasing for Hunting in the Czech Republic: Infection Dynamics and Potential Risks

Age-related dynamics of protozoan and helminth infections in the red-legged partridge, Alectoris rufa, were studied in an intensive breeding aviary in the Czech Republic before releasing birds for hunting purposes. Pooled fecal samples (n = 900) were examined over 3 rearing seasons (2012-2014). A total of 4 protozoan species, Cryptosporidium baileyi, Cryptosporidium meleagridis, Eimeria kofoidi, and Eimeria legionensis, and 4 helminths, Capillaria phasianina, Eucoleus perforans, Heterakis gallinarum, and Syngamus trachea, was found. The most common parasite was S. trachea (prevalence 20-26%) in dead birds (n = 99), which represents a high risk for breeders. Co-occurrence of protozoans and helminths indicated similarities in infection dynamics throughout the 3 breeding seasons. Mixed infections of Cryptosporidium baileyi and C. meleagridis with other parasitic species are reported for the first time. Our findings provide new insights into breeding of A. rufa and may help to improve the efficacy of disease control strategies and prevention, especially with the potential for spreading of parasitic infections to wildlife through released birds into open areas.

Syngamus asphyxiation in a captive ring-necked pheasant

A deceased ring-necked pheasant (Phasianus colchicus) presented for necropsy following a history of chronic wasting. Necropsy revealed nematodes consistent with the genus Syngamus partially obstructing the trachea. Phylogentic analysis failed to reveal conclusive results regarding the species. Syngamus spp. can cause obstruction of the trachea in several different hosts. Additional genetic data from this taxon would aid in the more precise identification of diagnostic specimens.

Taxonomic status of Syngamus nematodes parasitizing passeriform hosts from Central Europe: Morphological, morphometric and molecular identification

The systematic position and validity of species within genus Syngamus have always been controversial. In this present work, we evaluated the taxonomic status and phylogenetic relationships between three species of Syngamus nematodes (Syngamus trachea, Syngamus taiga and Syngamus merulae) and one taxa, determined only to the generic level, collected from respiratory tracts of passeriform hosts from Central Europe using newly obtained sequences of 2 nuclear markers (internal transcribed spacers 1 and 2 [ITS1, ITS2]) and a fragment of mitochondrial cytochrome oxidase I [COI] gene. Our results clearly showed that S. trachea, S. taiga and S. merulae are valid, molecularly and morphologically distinct species. Moreover, molecular analysis of adult female of Syngamus sp. collected from tracheae of the European robin Erithacus rubecula clearly indicate that these comprise separate species. In the derived phylogeny, the Syngamus clade is divided into two sub-clades: one comprised Syngamus species with a characteristic, well-developed cuticular collar around the oral opening (S. trachea and S. taiga) and a second that groups taxa without or with rudimentary collar (S. merulae and currently sequenced Syngamus sp. from Erithacus rubecula). These results clearly suggest that the degree of collar development (well-developed vs. rudimentary/absent) may be an important phylogenetic feature for determining the structure of the genus Syngamus on subgeneric level. Additionally, our results support historical division of the genus Syngamus into two subgenera S. (Syngamus) and S. (Ornithogamus).

Spatio-temporal factors influencing the occurrence of Syngamus trachea within release pens in the South West of England

Syngamus trachea is a pathogenic tracheal nematode that causes syngamiasis in wild and game birds, especially when birds are managed at high densities. Despite its pathogenic nature, very little is known about its epidemiology and relationship with ambient temperature and humidity. The spatial and temporal modelling of disease was undertaken on two pheasant estates within the South West of England from April 2014 to August 2014. Significant differences between the mean numbers of eggs per gram of soil were identified between pens at both site 1 and site 2 but did not differ significantly between sites. Egg abundance was significantly associated with soil moisture content, with greater egg survival between years in pens with higher average volumetric soil moisture content. Previous years stocking density and pen age were also associated with greater egg survival between years with more eggs being recovered in pens with greater stocking densities, and pens that had been sited longer. The greatest model to explain the variation in the numbers of eggs per gram of soil per pen was a combination of soil moisture content, stocking density and pen age. Larval recovery differed significantly between sites. Larval abundance was significantly and positively associated with temperature and relative humidity at site 1. Similarly, temperature and humidity were also positively and significantly associated with larval abundance at site 2. Rainfall did not influence larval recovery at either site 1 or site 2. The model with the greatest ability to explain larval abundance at both sites, was a combination of temperature, humidity and rainfall. Infection status (positive faecal egg counts) was significantly and positively associated with larval abundance at both sites, but rainfall was only positively associated at site 1. Temperature and humidity were positively associated with infection status at site 2, but not at site 1. The present study highlights the influence of climatic variables on both egg survival and larval abundance, and could therefore be used to develop more targeted treatment strategies around periods of higher disease risk. The frequent use of release pens is a clear factor in the epidemiology of syngamiasis, and it is recommended that pens be rested and/or rotated in order to reduce infection pressure in subsequent flocks.