Abstract
Pathogens pose a major risk to wild host populations, especially in the face of ongoing biodiversity declines. Beak and feather disease virus (BFDV) can affect most if not all members of one of the largest and most threatened bird orders world-wide, the Psittaciformes. Signs of disease can be severe and mortality rates high. Its broad host range makes it a risk to threatened species in particular, because infection can occur via spill-over from abundant hosts. Despite these risks, surveillance of BFDV in locally abundant wild host species has been lacking. We used qPCR and haemagglutination assays to investigate BFDV prevalence, load and shedding in seven abundant host species in the wild in south-east Australia: Crimson Rosellas (Platycercus elegans), Eastern Rosellas (Platycercus eximius), Galahs (Eolophus roseicapillus), Sulphur-crested Cockatoos (Cacatua galerita), Blue-winged Parrots (Neophema chrysostoma), Rainbow Lorikeets (Trichoglossus moluccanus) and Red-rumped Parrots (Psephotus haematonotus). We found BFDV infection in clinically normal birds in six of the seven species sampled. We focused our analysis on the four most commonly caught species, namely Crimson Rosellas (BFDV prevalence in blood samples: 41.8%), Sulphur-crested Cockatoos (20.0%), Blue-winged Parrots (11.8%) and Galahs (8.8%). Species, but not sex, was a significant predictor for BFDV prevalence and load. 56.1% of BFDV positive individuals were excreting BFDV antigen into their feathers, indicative of active viral replication with shedding. Being BFDV positive in blood samples predicted shedding in Crimson Rosellas. Our study confirms that BFDV is endemic in our study region, and can inform targeted disease management by providing comparative data on interspecies variation in virus prevalence, load and shedding.
Highlights
Wildlife diseases pose major threats to biodiversity; data on the abundance and distribution of pathogens in natural populations are often lacking, which impedes conservation efforts [1, 2]
We detected Beak and feather disease virus (BFDV) in all four focal species, namely Crimson Rosellas, Galahs, Sulphur-crested Cockatoos and Blue-winged Parrots, and prevalence in these species ranged from 8.8% to 41.8% in blood samples, and from 18.8% to 49.0% in cloacal swabs (Fig 1, Table 1)
Pairwise comparisons between species for BFDV prevalence in both sample types showed that Crimson Rosellas had a significantly higher prevalence than Galahs
Summary
Wildlife diseases pose major threats to biodiversity; data on the abundance and distribution of pathogens in natural populations are often lacking, which impedes conservation efforts [1, 2]. Not all hosts are likely to be infected and to transmit pathogens, so pathogen prevalence and transmission rates can show high heterogeneity between host species [8, 9] This heterogeneity can be caused by fluctuations in host resistance and tolerance to pathogens [6, 10], and by temporal and geographical factors influencing pathogen occurrence [11]. Prevalence and load can be influenced by host sex, due to sex-specific immune responses [12] Such host individual- and species-specific effects can influence the outcome of infections and can often be important for the management of wildlife disease [13]
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