Testosterone treatment to free-ranging male dark-eyed juncos (JUNCO HYEMALIS) exacerbates hemoparasitic infection

Pierre Deviche, Jennifer Parris

Research output: Contribution to journalArticle

24 Citations (Scopus)

Abstract

The "immunocompetence handicap" hypothesis predicts that reproductive hormones, in particular testosterone (T), are immunosuppressive and consequently increase susceptibility to diseases and parasite infections, but this prediction has not been evaluated in free-living birds and the factors mediating the immunosuppressive influence of T remain poorly known. To address these issues, we administered supplemental T via implants to free-ranging adult male Dark-eyed Juncos (Junco hyemalis) and characterized the effects of this treatment on infection with the two most prevalent hematozoan parasites in this species, Leucocytozoon fringillinarum and Trypanosoma avium. Males caught at the beginning of their breeding season (May) received T-filled, empty (control), or no Silastic capsules, and were recaptured five weeks later. Capsule implantation had, by itself, no effect on parasite infections, body mass, or size of an androgen-dependent secondary sexual characteristic, the cloacal protuberance. Testosterone treatment maintained physiologically high plasma levels of the steroid for the duration of the study, thus preventing the seasonal decline in these levels that occurred in control males. As predicted by the immunocompetence handicap hypothesis, the hormone treatment increased blood L. fringillinarum abundance. This increase was specific, in that implanted T did not affect (1) either the prevalence or the incidence of L. fringillinarum, (2) body mass, or (3) size of the cloacal protuberance. Trypanosoma avium prevalence was not influenced by T treatment either, but it increased between May and June, which suggests that it is regulated by factors other than the activity of the reproductive system. These findings provide the first demonstration in free-ranging birds that experimentally elevated physiological T levels increase hematozoan infection.

Original languageEnglish (US)
Pages (from-to)548-562
Number of pages15
JournalAuk
Volume123
Issue number2
DOIs
StatePublished - Apr 2006

Fingerprint

testosterone
Junco hyemalis
immunocompetence
immunosuppressive agents
Trypanosoma
parasite
parasites
infection
body mass
hormone
secondary sexual characteristics
hormones
bird
Leucocytozoon
androgen
birds
reproductive system
steroid
androgens
breeding season

Keywords

  • Androgen
  • Blood parasites
  • Dark-eyed junco
  • Immunocompetence handicap hypothesis
  • Immunosuppression
  • Junco hyemalis
  • Leucocytozoon fringillinarum
  • Passerine
  • Trypanosoma avium

ASJC Scopus subject areas

  • Animal Science and Zoology

Cite this

Testosterone treatment to free-ranging male dark-eyed juncos (JUNCO HYEMALIS) exacerbates hemoparasitic infection. / Deviche, Pierre; Parris, Jennifer.

In: Auk, Vol. 123, No. 2, 04.2006, p. 548-562.

Research output: Contribution to journalArticle

@article{2860dde5d8f14ccd8211010abff6310a,
title = "Testosterone treatment to free-ranging male dark-eyed juncos (JUNCO HYEMALIS) exacerbates hemoparasitic infection",
abstract = "The {"}immunocompetence handicap{"} hypothesis predicts that reproductive hormones, in particular testosterone (T), are immunosuppressive and consequently increase susceptibility to diseases and parasite infections, but this prediction has not been evaluated in free-living birds and the factors mediating the immunosuppressive influence of T remain poorly known. To address these issues, we administered supplemental T via implants to free-ranging adult male Dark-eyed Juncos (Junco hyemalis) and characterized the effects of this treatment on infection with the two most prevalent hematozoan parasites in this species, Leucocytozoon fringillinarum and Trypanosoma avium. Males caught at the beginning of their breeding season (May) received T-filled, empty (control), or no Silastic capsules, and were recaptured five weeks later. Capsule implantation had, by itself, no effect on parasite infections, body mass, or size of an androgen-dependent secondary sexual characteristic, the cloacal protuberance. Testosterone treatment maintained physiologically high plasma levels of the steroid for the duration of the study, thus preventing the seasonal decline in these levels that occurred in control males. As predicted by the immunocompetence handicap hypothesis, the hormone treatment increased blood L. fringillinarum abundance. This increase was specific, in that implanted T did not affect (1) either the prevalence or the incidence of L. fringillinarum, (2) body mass, or (3) size of the cloacal protuberance. Trypanosoma avium prevalence was not influenced by T treatment either, but it increased between May and June, which suggests that it is regulated by factors other than the activity of the reproductive system. These findings provide the first demonstration in free-ranging birds that experimentally elevated physiological T levels increase hematozoan infection.",
keywords = "Androgen, Blood parasites, Dark-eyed junco, Immunocompetence handicap hypothesis, Immunosuppression, Junco hyemalis, Leucocytozoon fringillinarum, Passerine, Trypanosoma avium",
author = "Pierre Deviche and Jennifer Parris",
year = "2006",
month = "4",
doi = "10.1642/0004-8038(2006)123[548:TTTFMD]2.0.CO;2",
language = "English (US)",
volume = "123",
pages = "548--562",
journal = "Auk",
issn = "0004-8038",
publisher = "Ornithological Societies of North America",
number = "2",

}

TY - JOUR

T1 - Testosterone treatment to free-ranging male dark-eyed juncos (JUNCO HYEMALIS) exacerbates hemoparasitic infection

AU - Deviche, Pierre

AU - Parris, Jennifer

PY - 2006/4

Y1 - 2006/4

N2 - The "immunocompetence handicap" hypothesis predicts that reproductive hormones, in particular testosterone (T), are immunosuppressive and consequently increase susceptibility to diseases and parasite infections, but this prediction has not been evaluated in free-living birds and the factors mediating the immunosuppressive influence of T remain poorly known. To address these issues, we administered supplemental T via implants to free-ranging adult male Dark-eyed Juncos (Junco hyemalis) and characterized the effects of this treatment on infection with the two most prevalent hematozoan parasites in this species, Leucocytozoon fringillinarum and Trypanosoma avium. Males caught at the beginning of their breeding season (May) received T-filled, empty (control), or no Silastic capsules, and were recaptured five weeks later. Capsule implantation had, by itself, no effect on parasite infections, body mass, or size of an androgen-dependent secondary sexual characteristic, the cloacal protuberance. Testosterone treatment maintained physiologically high plasma levels of the steroid for the duration of the study, thus preventing the seasonal decline in these levels that occurred in control males. As predicted by the immunocompetence handicap hypothesis, the hormone treatment increased blood L. fringillinarum abundance. This increase was specific, in that implanted T did not affect (1) either the prevalence or the incidence of L. fringillinarum, (2) body mass, or (3) size of the cloacal protuberance. Trypanosoma avium prevalence was not influenced by T treatment either, but it increased between May and June, which suggests that it is regulated by factors other than the activity of the reproductive system. These findings provide the first demonstration in free-ranging birds that experimentally elevated physiological T levels increase hematozoan infection.

AB - The "immunocompetence handicap" hypothesis predicts that reproductive hormones, in particular testosterone (T), are immunosuppressive and consequently increase susceptibility to diseases and parasite infections, but this prediction has not been evaluated in free-living birds and the factors mediating the immunosuppressive influence of T remain poorly known. To address these issues, we administered supplemental T via implants to free-ranging adult male Dark-eyed Juncos (Junco hyemalis) and characterized the effects of this treatment on infection with the two most prevalent hematozoan parasites in this species, Leucocytozoon fringillinarum and Trypanosoma avium. Males caught at the beginning of their breeding season (May) received T-filled, empty (control), or no Silastic capsules, and were recaptured five weeks later. Capsule implantation had, by itself, no effect on parasite infections, body mass, or size of an androgen-dependent secondary sexual characteristic, the cloacal protuberance. Testosterone treatment maintained physiologically high plasma levels of the steroid for the duration of the study, thus preventing the seasonal decline in these levels that occurred in control males. As predicted by the immunocompetence handicap hypothesis, the hormone treatment increased blood L. fringillinarum abundance. This increase was specific, in that implanted T did not affect (1) either the prevalence or the incidence of L. fringillinarum, (2) body mass, or (3) size of the cloacal protuberance. Trypanosoma avium prevalence was not influenced by T treatment either, but it increased between May and June, which suggests that it is regulated by factors other than the activity of the reproductive system. These findings provide the first demonstration in free-ranging birds that experimentally elevated physiological T levels increase hematozoan infection.

KW - Androgen

KW - Blood parasites

KW - Dark-eyed junco

KW - Immunocompetence handicap hypothesis

KW - Immunosuppression

KW - Junco hyemalis

KW - Leucocytozoon fringillinarum

KW - Passerine

KW - Trypanosoma avium

UR - http://www.scopus.com/inward/record.url?scp=33646546020&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=33646546020&partnerID=8YFLogxK

U2 - 10.1642/0004-8038(2006)123[548:TTTFMD]2.0.CO;2

DO - 10.1642/0004-8038(2006)123[548:TTTFMD]2.0.CO;2

M3 - Article

AN - SCOPUS:33646546020

VL - 123

SP - 548

EP - 562

JO - Auk

JF - Auk

SN - 0004-8038

IS - 2

ER -