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1 April 2011 The Effect of Coccidians on the Condition and Immune Profile of Molting House Sparrows (Passer domesticus)
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Feather molt is recognized as an energetically costly activity for birds, and parasite infestation during molt has the potential to reduce host fitness because parasites sequester essential nutrients and stimulate the immune system. We manipulated the coccidian parasite load of captive male House Sparrows (Passer domesticus) by suppressing the natural infection of control birds with an anticoccidial drug and infecting experimental birds with coccidian oocysts. Following infestation, the effect of chronic coccidian infection on individual condition, molt and 12 indices of physiological and immunological function was assessed. We found a significant positive relationship between infestation and heterophil/lymphocyte ratio measured at capture, indicating infectioninduced stress. We also found that coccidians negatively affected feather growth during molt: the increase in wing length of the noninfected birds was significantly higher than that of infected birds. In comparison to control birds, infected birds showed a significantly higher concentration of white blood cells and greater blood bactericidal activity. There was also a positive correlation between infection intensity, agglutination and lysis of blood in the experimentally infested birds, which indicated activation of the constitutive innate immune system during infection. Finally, the total antioxidant capacity of the blood increased significantly, while the carotenoid concentration decreased significantly in infected compared with control birds. Therefore, we showed that coccidians stimulated several measures of the constitutive innate immunity, including the bactericidal activity of the blood, and that coccidians can have significant negative effects on the health and possibly fitness of molting House Sparrows.

© 2011 by The American Ornithologists' Union. All rights reserved. Please direct all requests for permission to photocopy or reproduce article content through the University of California Press's Rights and Permissions website,
Péter László Pap, Csongor István Vágási, Gábor Árpád Czirják, Adriana Titilincu, Adela Pintea, Gergely Osváth, Attila Fülöp, and Zoltán Barta "The Effect of Coccidians on the Condition and Immune Profile of Molting House Sparrows (Passer domesticus)," The Auk 128(2), 330-339, (1 April 2011).
Received: 4 June 2010; Accepted: 1 December 2010; Published: 1 April 2011

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