Abstract
Infectious diseases are one of the most common threats for both domestic and wild animals, but little is known about the effects on the physiological condition and survival of wild animals. Here, we have tested for the first time in a wild vertebrate facing a viral disease possibly due to herpesvirus (i) whether nestlings with either low levels of oxidative damage or high levels of antioxidant protection are less susceptible to develop visible clinical signs, (ii) whether the disease is associated with the nestlings’ oxidative status, (iii) whether the association between the disease and oxidative status is similar between males and females (iv), and whether cloacal and tracheal swabs might be used to detect herpesvirus. To address our questions, we took advantage of a population of Magnificent frigatebirds (Fregata magnificens) whose nestlings have experienced high mortality rates in recent times. Our work shows that (i) blood lipid oxidative damage is associated with observable clinical signs and survival probabilities of nestling frigatebirds, and (ii) that high glutathione levels in red blood cells are associated with the emergence of visible clinical signs of the disease. Our work provides evidence that differences in the oxidative status of nestlings might underlie individual health and survival.
Highlights
Wildlife infectious diseases have enormous ecological and public health impacts[1]
The aims of this study were to investigate (i) whether nestlings with either low levels of oxidative damage or high levels of antioxidant protection are less susceptible to develop visible clinical signs, (ii) whether the disease is associated with the nestlings oxidative status, (iii) whether the impact of the disease on oxidative status and survival is similar between males and females (iv), and whether the use of cloacal and tracheal swabs might be used as a non-invasive tool to detect the presence of the infectious agent in individuals without clinical signs
Herpesviral DNA was detected in the tracheal and cloacal swabs of seven out of ten healthy-looking individuals sampled during the first period, compared to nine out of ten individuals showing clinical signs at the first sampling period
Summary
Wildlife infectious diseases have enormous ecological and public health impacts[1]. Notorious examples of infectious diseases that are dramatically causing massive population declines are the fungus Batrachochytrium dendrobatidis that is affecting frogs worldwide[2] or a novel infectious cancer that is jeopardizing the future of the Tasmanian devil Sarcophilus harrisii[3]. A recent meta-analysis across many different domestic and animal species has provided support for the hypothesis that OS is likely to be one molecular mechanism responsible of pathological effects of herpesvirus infection[34] This meta-analysis showed that herpesvirus infection decreases the level of non-enzymatic antioxidants, increases the generation of reactive oxygen species (ROS) and causes oxidative damage to biomolecules[34]. Some studies have found OS to be associated with infectious diseases and possibly to be one mechanism responsible for the patho-physiological consequences of several viral infections[26, 34, 40], (i) most of the work has been done on humans and laboratory or domestic animals; and (ii) the role of oxidative stress in determining health and survival perspectives is complex and results have often been contradictory[28, 29]. Our study is relevant for conservation because it may provide conservation practitioners with tools to predict the impact of a pathogen on fitness traits
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