Comparison of beak and feather disease virus prevalence and immunity-associated genetic diversity over time in an island population of red-crowned parakeets

Abstract

Pathogen outbreaks in the wild can contribute to a population's extinction risk. Concern over the effects of pathogen outbreaks in wildlife is amplified in small, threatened populations, where degradation of genetic diversity may hinder natural selection for enhanced immunocompetence. Beak and feather disease virus (BFDV) was detected for the first time in an island population of red-crowned parakeets (Cyanoramphus novaezelandiae) in 2008 on Little Barrier Island (Hauturu-o-Toi) of New Zealand. By 2013, the prevalence of the viral infection had significantly decreased within the population. We tested whether the population of red-crowned parakeets showed a selective response to BFDV, using neutral microsatellite and two immunity-associated genetic markers, the major histocompatibility complex (MHC) and Toll-like receptors (TLRs). We found evidence for selection at viral-associated TLR3; however, the ability of TLR3 to elicit an immune response in the presence of BFDV warrants confirmation. Alternatively, because red-crowned parakeet populations are prone to fluctuations in size, the decrease in BFDV prevalence over time may be attributed to the Little Barrier Island population dropping below the density threshold for viral maintenance. Our results highlight that natural processes such as adaptation for enhanced immunocompetence and/or density fluctuations are efficient mechanisms for reducing pathogen prevalence in a threatened, isolated population.

Pathogen-associated selection on innate immunity genes (TLR4, TLR7) in a neotropical rodent in landscapes differing in anthropogenic disturbance

“…However, studies on the cause–response relationships between TLRs and viral pathogens in wildlife remain rare. Knafler et al ( 2016 ) have shown a relationship between TLR3 and the beak and feather virus in red-crowned parakeets ( Cyanoramphus novaezelandiae ), but without further elaborating on the effect of specific haplotypes on infection status. Loots et al ( 2018 ) reported a possible beneficial effect of a SNP in TLR2 on canine distemper virus susceptibility in South African lions, resulting in an amino acid exchange within the LRR.…”

Molecular Epidemiology of Bacterial Wilt in the Madagascar Highlands Caused by Andean (Phylotype IIB-1) and African (Phylotype III) Brown Rot Strains of the Ralstonia solanacearum Species Complex

“…The genetic diversity and population structure of the RSSC strains prevalent in Malagasy potato growing basins were investigated, and our understanding of potato BW epidemiology was improved. Most studies have investigated the population diversity and biology of plant pathogens to gain better insight into disease etiology ( Milgroom and Peever, 2003 ). Major agronomic areas of the potato growing basins of Madagascar were prospected for RSSC strains at different agroecological scales and strains were typed using MLVA schemes.…”

Leveraging an existing whole‐genome resequencing population data set to characterize toll‐like receptor gene diversity in a threatened bird

“…Given that there has been little to no genetic exchange between the populations for decades, these differences can most likely be attributed to genetic drift. Previous research in other bird species has also found genetic differentiation in both neutral (microsatellites) and TLR loci, which generally indicates that genetic drift may be stronger than selection (Gonzalez-Quevedo et al, 2015;Grueber et al, 2013;Knafler et al, 2016). However, it is possible that selection at TLR loci may contribute to the genetic differentiation between populations (Grueber et al, 2013;Knafler et al, 2016Knafler et al, , 2017.…”