Epizootiology and Effect of Avian Pox on Hawaiian Forest Birds

Riper, Charles van; Riper, Sandra G. van; Hansen, Wallace R.

doi:10.2307/4090224

Cited by 90 publications

(112 citation statements)

References 21 publications

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“…Although the field of wildlife biology has an extensive history of CMR usage with strong theoretical and empirical underpinnings, the empirical study of wildlife diseases is a relatively newer avenue of investigation in this field. In this burgeoning area of interest, a standard method for estimating disease prevalence has been to establish a sampling framework around a target population and report proportions of infected individuals from that sample under the assumption that detection probabilities are invariant temporally, spatially, and between relevant health states of individuals (e.g., Dobson and Meagher 1996, Delahay et al 2000, Van Riper et al 2002, Fallon et al 2003, Joly et al 2003.…”

Section: Introductionmentioning

confidence: 99%

State-Specific Detection Probabilities and Disease Prevalence

Jennelle

Cooch

Conroy

et al. 2007

Ecological Applications

110

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Investigations of disease dynamics in wild animal populations often use estimated prevalence or incidence as a measure of true disease frequency. Such indices, almost always based solely on raw counts of infected and uninfected individuals, are often used as the basis for analysis of temporal and spatial dynamics of diseases. Generally, such studies do not account for potential differences in observer detection probabilities of host individuals stratified by biotic and/or abiotic factors. We demonstrate the potential effects of heterogeneity in state-specific detection probabilities on estimated disease prevalence using mark-recapture data from previous work in a House Finch (Carpodacus mexicanus) and Mycoplasma gallisepticum system. In this system, detection probabilities of uninfected finches were generally higher than infected individuals. We show that the magnitude and seasonal pattern of variation in estimated prevalence, corrected for differences in detection probabilities, differed markedly from uncorrected (apparent) prevalence. When the detection probability of uninfected individuals is higher than infected individuals (as in our study), apparent prevalence is negatively biased, and vice versa. In situations where state-specific detection probabilities strongly interact over time, we show that the magnitude and pattern of apparent prevalence can change dramatically; in such cases, observed variations in prevalence may be completely spurious artifacts of variation in detection probability, rather than changes in underlying disease dynamics. Accounting for differential detection probabilities in estimates of disease frequency removes a potentially confounding factor in studies seeking to identify biotic and/or abiotic drivers of disease dynamics. Given that detection probabilities of different groups of individuals are likely to change temporally and spatially in most field studies, our results underscore the importance of estimating and incorporating detection probabilities in estimated disease prevalence (specifically), and more generally, any ecological index used to estimate some parameter of interest. While a mark-recapture approach makes it possible to estimate detection probabilities, it is not always practical, especially at large scales. We discuss several alternative approaches and categorize the assumptions under which analysis of uncorrected prevalence may be acceptable.

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Section: Introductionmentioning

confidence: 99%

State-Specific Detection Probabilities and Disease Prevalence

Jennelle

Cooch

Conroy

et al. 2007

Ecological Applications

110

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“…Habitat loss began with Polynesian colonists, who cleared much of the low-elevation and seasonally dry forest for agricultural purposes (7). Europeans and other colonists introduced new agricultural technology and additional domesticated animals; the introduction of cattle and sheep in particular led to the development of pasturages in high-elevation forest that further reduced the amount of suitable habitat for native forest birds (8,9). Today, the distribution of montane tropical rainforest is constrained by agriculture and urban development at low elevations, and pasture remains the major human land use at high elevations.…”

mentioning

confidence: 99%

Interactions of climate change with biological invasions and land use in the Hawaiian Islands: Modeling the fate of endemic birds using a geographic information system

Benning

LaPointe

Atkinson

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

260

221

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“…I did not clinically confirm field diagnoses of pox because risk of biopsy was too high in this endangered bird. Atkinson et al (2005) and van Riper et al (2002) similarly did not biopsy birds to confirm field diagnoses of pox, but van Riper et al (2002) confirmed field diagnoses in a sample of dead birds (n ¼ 10) by examination of tissue obtained during necropsy. Although pox is the most likely cause of the lesions observed in elepaio, I refer to them as pox-like lesions or simply lesions because I did not clinically confirm diagnoses.…”

Section: Elepaio Monitoringmentioning

confidence: 94%

“…In a few cases I confirmed sex by behavior (e.g., singing, copulation) or genetically. I regarded elepaio with 1) soft swellings, warty growths, open sores, or crusty scabs on the toes, feet, legs, or face as having active pox-like lesions, 2) missing or deformed toes or feet as having inactive pox-like lesions, and 3) no visible pox-like symptoms as healthy (VanderWerf et al 2006, van Riper andForrester 2007). I did not clinically confirm field diagnoses of pox because risk of biopsy was too high in this endangered bird.…”

Section: Elepaio Monitoringmentioning

confidence: 99%

“…Avian malaria (Plasmodium relictum) and avian poxvirus (Poxvirus avium) are serious threats that cause high mortality in some species of Hawaiian forest birds and limit their distributions (Warner 1968, Atkinson et al 1995, van Riper et al 2002, but immunity to these diseases has been discovered in Oahu amakihi (Hemignathus flavus; Shehata et al 2001) and Hawaii amakihi (H. virens;Woodworth et al 2005, Foster et al 2007). Prevalence of malaria and poxvirus is high in Oahu elepaio (Vander-Werf et al 2006), so the impact of these diseases is potentially serious, but their actual effect on wild birds is unknown.…”

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confidence: 99%

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Importance of Nest Predation by Alien Rodents and Avian Poxvirus in Conservation of Oahu Elepaio

VanderWerf

2009

J Wildl Manag

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The Oahu elepaio (Chasiempis sandwichensis ibidis) is an endangered forest bird endemic to the Hawaiian island of Oahu (USA) and is threatened by nest predation from alien rodents and mosquito‐borne diseases. I investigated importance of these threats and evaluated success of conservation efforts from 1995 to 2008. I controlled rodents with snap‐traps and bait stations in 3 valleys and switched sites from non‐treatment to treatment over time. I mist‐netted and color‐banded 91 elepaio, inspected them for symptoms of avian poxvirus (Poxvirus avium), and estimated survival using multistate mark‐recapture models. I determined annual fecundity of each breeding pair and monitored success of 212 nests. The oldest known Oahu elepaio was ≥15 years old. Survival of females was higher with rodent control (0.82 ± 0.05) than without (0.55 ± 0.12), but survival of males was not affected by rodent control (0.86 ± 0.02 with vs. 0.84 ± 0.04 without). Survival of elepaio with active or inactive pox‐like lesions was 4–10% lower than survival of elepaio with no pox symptoms. Rodent control resulted in higher annual fecundity (0.69 ± 0.05 vs. 0.33 ± 0.06 fledglings/pair) and nest success (62% vs. 33%). Female site‐fidelity, mate fidelity, and female encounter probability were lower in the absence of rodent control because more females switched territories and mates after nest failure. Population growth calculated from survival and fecundity estimates was stable with rodent control (1.07 ± 0.04) but declining without rodent control (0.69 ± 0.05). Elepaio numbers have continued to decline despite rodent control, probably because some young birds disperse into adjacent unmanaged areas that act as sinks. The best immediate management strategy for Oahu elepaio is to conduct rodent control over larger areas. Restoration of native forest would benefit elepaio by providing nest sites that are less attractive to rodents. Construction of predator‐proof fences and eradication of predators would provide the best long‐term protection for elepaio.

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Epizootiology and Effect of Avian Pox on Hawaiian Forest Birds

Cited by 90 publications

References 21 publications

State-Specific Detection Probabilities and Disease Prevalence

State-Specific Detection Probabilities and Disease Prevalence

Interactions of climate change with biological invasions and land use in the Hawaiian Islands: Modeling the fate of endemic birds using a geographic information system

Importance of Nest Predation by Alien Rodents and Avian Poxvirus in Conservation of Oahu Elepaio

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