Birds Shed RNA-Viruses According to the Pareto Principle

Abstract

A major challenge in disease ecology is to understand the role of individual variation of infection load on disease transmission dynamics and how this influences the evolution of resistance or tolerance mechanisms. Such information will improve our capacity to understand, predict, and mitigate pathogen-associated disease in all organisms. In many host-pathogen systems, particularly macroparasites and sexually transmitted diseases, it has been found that approximately 20% of the population is responsible for approximately 80% of the transmission events. Although host contact rates can account for some of this pattern, pathogen transmission dynamics also depend upon host infectiousness, an area that has received relatively little attention. Therefore, we conducted a meta-analysis of pathogen shedding rates of 24 host (avian) – pathogen (RNA-virus) studies, including 17 bird species and five important zoonotic viruses. We determined that viral count data followed the Weibull distribution, the mean Gini coefficient (an index of inequality) was 0.687 (0.036 SEM), and that 22.0% (0.90 SEM) of the birds shed 80% of the virus across all studies, suggesting an adherence of viral shedding counts to the Pareto Principle. The relative position of a bird in a distribution of viral counts was affected by factors extrinsic to the host, such as exposure to corticosterone and to a lesser extent reduced food availability, but not to intrinsic host factors including age, sex, and migratory status. These data provide a quantitative view of heterogeneous virus shedding in birds that may be used to better parameterize epidemiological models and understand transmission dynamics.

Individual differences in boldness influence patterns of social interactions and the transmission of cuticular bacteria among group-mates

“…Interindividual variation in behaviour and contact networks of infected and susceptible individuals have vast consequences for many emerging diseases in wildlife [53] and humans [5]. Here, we did not find support for our original hypothesis, but rather found that S. dumicola contact networks are behaviourally disassortative, and that the transmission of cuticular bacteria is more likely when exposed individuals were bolder than their susceptible colony-mates.…”

The Association Between SAα2,3Gal Occurrence Frequency and Avian Influenza Viral Load in Mallards (Anas Platyrhynchos) and Blue-Winged Teals (Spatula discors)

“…Species-based variation in SAα2,3Gal has been observed in other experimental infection studies (10,38). Jankowski et al (21) analyzed the variation of sialic acid receptors expressed by erythrocytes in various avian species and found that approximately 20% of the species expressed 80% of the overall sialic acid receptor quantity in all species studied.…”

“…Group names refer to their species (mallard = M, teal = B), whether they received LPAIV treatment (inoculated with virus= T, control = C), and the DPI they were sacrificed (# to follow T/C). The minimum sample size per group was based on individual viral load variation observed in populations as small as ten individuals (10). Additional birds were placed in groups on DPI of most importance such as high viral shedding (DPI 1-3) and early detection of antibody titer (DPI 5) (55).…”

Modelling filovirus maintenance in nature by experimental transmission of Marburg virus between Egyptian rousette bats

“…For example, the curve shows that 25.0% of the inoculated bat population was responsible for 98.3% of MARV oral shedding, 50.0% of the bats were responsible for 99.4% of oral shedding and 75.0% of the bats were responsible for 99.4% of oral shedding. Using a previously established approach 18 , two inoculated bats were classified as supershedders (685734 and 691198), as each of them shed virus at levels greater than the 80th percentile (4.82 log 10 TCID 50 eq ml −1 ) and together accounted for 91.1% of the total MARV oral shedding. MARV oral shedding was detected in both of these bats at nine time points each, and infectious virus was isolated from five oral swabs taken from bat 685734 and three oral swabs taken from bat 691198.…”