Coccidian Infection Causes Oxidative Damage in Greenfinches

Abstract

The main tenet of immunoecology is that individual variation in immune responsiveness is caused by the costs of immune responses to the hosts. Oxidative damage resulting from the excessive production of reactive oxygen species during immune response is hypothesized to form one of such costs. We tested this hypothesis in experimental coccidian infection model in greenfinches Carduelis chloris. Administration of isosporan coccidians to experimental birds did not affect indices of antioxidant protection (TAC and OXY), plasma triglyceride and carotenoid levels or body mass, indicating that pathological consequences of infection were generally mild. Infected birds had on average 8% higher levels of plasma malondialdehyde (MDA, a toxic end-product of lipid peroxidation) than un-infected birds. The birds that had highest MDA levels subsequent to experimental infection experienced the highest decrease in infection intensity. This observation is consistent with the idea that oxidative stress is a causative agent in the control of coccidiosis and supports the concept of oxidative costs of immune responses and parasite resistance. The finding that oxidative damage accompanies even the mild infection with a common parasite highlights the relevance of oxidative stress biology for the immunoecological research.

On the methodological limitations of detecting oxidative stress: effects of paraquat on measures of oxidative status in greenfinches

“…However, we cannot exclude the hypothetical possibility that (quick) restoration of redox homeostasis per se might appear costly in terms of some ecologically relevant currency. Finally, it should be noted in the context of the current study that two previous experiments conducted on greenfinches in our lab have detected increased lipid peroxidation (plasma MDA) in response to the experimental blocking of GSH synthesis and coccidian infection (Sepp et al, 2012b). One possible explanation for discrepancies between the results of the current study and those cited above might be the different timing of blood sampling with respect to treatments between studies.…”

“…In a study by Hõrak and colleagues, the birds were bled 1day after the last injection of buthionine sulphoximine, an inhibitor of GSH synthesis . In the study by Sepp and colleagues, the birds were bled during the peak phase of experimental coccidian infection (Sepp et al, 2012b).…”

Simple and noninvasive method for assessment of digestive efficiency: Validation of fecal steatocrit in greenfinch coccidiosis model

“…One of the antimicrobials—toltrazuril—is designed specifically for treatment of coccidiosis and lacks known effects on microbes other than apicomplexans (see Sepp et al., 2012). Metronidazole has wider spectrum of activity against anaerobic bacteria and protozoans and is widely used for medication of trichomonosis (Samuelson, 1999).…”

“…Both toltrazuril (Sepp et al., 2012) and sulfonamide drug Vetacox (Hõrak et al., 2004) reduce the intensity of coccidian infection; birds treated with sulfonamide have higher plasma triglyceride levels (a marker of nutritional state) and body mass than birds experimentally infected with coccidians (Hõrak et al., 2004). We thus predicted that (i) treatments with toltrazuril and sulfadimethoxine result in decrease in steatocrit values as compared to untreated control birds.…”

Seasonal Patterns and Relationships among Coccidian Infestations, Measures of Oxidative Physiology, and Immune Function in Free-Living House Sparrows over an Annual Cycle

“…Parasite infection and immune activation may affect different aspects of oxidative physiology, including measures of antioxidant system and oxidative damage (Halliwell and Gutteridge 2007;Costantini and Møller 2009;Sorci and Faivre 2009;Sepp et al 2012a). Likewise, different measures of oxidative physiology may indicate similar or dissimilar aspects of infection, immune activation, and oxidative stress (Cohen and McGraw 2009;Costantini and Verhulst 2009;Monaghan et al 2009;Hõrak and Cohen 2010;Metcalfe and Monaghan 2013).…”