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Philornis downsi infestation

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Philornis downsi infestation

Pictures

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PictureTitleCaptionCopyright
Medium tree finch, Camarhynchus pauper, female. C. pauper is a critically endangered species threatened by P. downsi
TitleMedium tree finch
CaptionMedium tree finch, Camarhynchus pauper, female. C. pauper is a critically endangered species threatened by P. downsi
CopyrightJeremy Robertson
Medium tree finch, Camarhynchus pauper, female. C. pauper is a critically endangered species threatened by P. downsi
Medium tree finchMedium tree finch, Camarhynchus pauper, female. C. pauper is a critically endangered species threatened by P. downsiJeremy Robertson
Adult Philornis downsi
TitleAdult
CaptionAdult Philornis downsi
CopyrightJody O'Connor
Adult Philornis downsi
AdultAdult Philornis downsiJody O'Connor
Third instar larvae: note blood in gut [of darker] larvae.
TitleLarvae
CaptionThird instar larvae: note blood in gut [of darker] larvae.
CopyrightJody O'Connor
Third instar larvae: note blood in gut [of darker] larvae.
LarvaeThird instar larvae: note blood in gut [of darker] larvae.Jody O'Connor
Dead nestlings of Camarhynchus pauper (Medium tree finch) with signs of P. downsi parasitism.
TitleEffects of parasitism
CaptionDead nestlings of Camarhynchus pauper (Medium tree finch) with signs of P. downsi parasitism.
CopyrightJody O'Connor
Dead nestlings of Camarhynchus pauper (Medium tree finch) with signs of P. downsi parasitism.
Effects of parasitismDead nestlings of Camarhynchus pauper (Medium tree finch) with signs of P. downsi parasitism.Jody O'Connor
Floreana Island, Galapagos. Habitat of P. downsi and its hosts.
TitleFloreana Island
CaptionFloreana Island, Galapagos. Habitat of P. downsi and its hosts.
CopyrightJody O'Connor
Floreana Island, Galapagos. Habitat of P. downsi and its hosts.
Floreana IslandFloreana Island, Galapagos. Habitat of P. downsi and its hosts.Jody O'Connor
Philornis pupae and larvae.
TitlePupae and larvae
CaptionPhilornis pupae and larvae.
CopyrightJody O'Connor
Philornis pupae and larvae.
Pupae and larvaePhilornis pupae and larvae.Jody O'Connor
Dead nestling of Camarhynchus pauper (Medium tree finch) with Philornis larvae.
TitleDead nestling
CaptionDead nestling of Camarhynchus pauper (Medium tree finch) with Philornis larvae.
CopyrightJody O'Connor
Dead nestling of Camarhynchus pauper (Medium tree finch) with Philornis larvae.
Dead nestlingDead nestling of Camarhynchus pauper (Medium tree finch) with Philornis larvae.Jody O'Connor

Identity

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Preferred Scientific Name

  • Philornis downsi infestation

Overview

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The genus Philornis contains approximately 50 species (Dudaniec and Kleindorfer, 2006) of flies whose larvae live in birds’ nests and feed on the blood of nestlings; they are distributed in the Neotropical regions of Central and South America. P. downsi was first described from Trinidad (Dodge and Aitkin, 1968), where it is not considered invasive; it was reported from the Galapagos Islands in 1997 (Fessl et al., 2001), but retrospective examination of an insect collection showed that it was already present there by 1964 (Causton et al., 2006). It is thought to have been accidentally introduced. It causes high levels of mortality among species such as Darwin’s finches (members of the Emberizidae), and there is serious concern about its effects on their populations – it has already been implicated in the decline of critically endangered endemic species (Fessl et al, 2006b; O’Connor et al., 2010d).

Hosts/Species Affected

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The number of parasites feeding on each nestling may be diluted in nests with larger broods (4-5 nestlings) (Dudaniec et al. 2006). Tree-finch (Camarhynchus) species generally have smaller brood sizes (2-3 nestlings) (Kleindorfer 2007), which may increase larval feeding on fewer nestlings. More P. downsi larvae are found in nests of Darwin’s finch species that are larger-bodied and build larger nests (Dudaniec et al., 2007; Kleindorfer and Dudaniec 2009). Larger-bodied hosts may provide resources for a greater number of P. downsi larvae, while larger nests may offer more space for both larval and pupal stages (see Kleindorfer and Dudaniec 2009). More larvae per nest (30-50 larvae) are found on elevated islands that have a humid highland forest, and an agricultural zone. Bulgarella et al. (2015) found that levels of parasitism in nests of bird species in mainland Ecuador were much lower than in the nests of Galapagos birds; they also state, citing other sources, that a total of 37 host species have been recorded from different parts of the range.

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Last updated: 10 Jan 2020
Continent/Country/Region Distribution Last Reported Origin First Reported Invasive Reference Notes

North America

Trinidad and TobagoPresent1968Dodge and Aitkin (1968)Various locations across the island of Trinidad

South America

ArgentinaPresentSilvestri et al. (2011)Chaco province. First reported in 2008-10
BrazilPresentCABI (Undated)Present based on regional distribution.
-Rio de JaneiroPresent1999Mendonça and Couri (1999)Angra dos reis
EcuadorPresentBulgarella et al. (2015)First reported from mainland Ecuador in 2013-4
-Galapagos IslandsPresent, WidespreadIntroducedInvasiveFessl et al. (2001); Causton et al. (2006); Wiedenfeld et al. (2007)Galapagos Islands: Santa Cruz, Floreana, Gardner por Floreana, Isabela, San Cristobal, Champion, Pinzon, Santiago, Marchena, Fernandina, Santa Fe, and Daphne

Pathology

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P. downsi larval feeding can result in up to 55% blood loss per nestling (Fessl et al., 2006a), and reduced nestling blood haemoglobin levels (Dudaniec et al., 2006). Immunological responses to P. downsi parasitism are yet to be tested.

Diagnosis

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Parasitised nestlings are commonly found with: grossly enlarged nares (nasal cavities), deteriorated and cavernous beaks that are often devoid of a nasal septum, and body lesions from larval attachment; dead nestlings are often found with large open body cavities with significant tissue loss (see Fessl et al. 2006b). Repeated movement of larvae through the nares at all instar stages causes enlargement of nasal openings observed in Darwin’s finches (Galligan and Kleindorfer, 2009; O’Connor et al., 2010b).

List of Symptoms/Signs

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SignLife StagesType
Digestive Signs / Cracked beak Other:All Stages Sign
Digestive Signs / Dryness oral mucosa Other:Juvenile Sign
Digestive Signs / Malformation of the beak Other:All Stages Sign
Digestive Signs / Oral mucosal ulcers, vesicles, plaques, pustules, erosions, tears Other:Juvenile Sign
General Signs / Discomfort, restlessness in birds Other:Juvenile Sign
General Signs / Lack of growth or weight gain, retarded, stunted growth Other:Juvenile Sign
General Signs / Sudden death, found dead Other:Juvenile Sign
General Signs / Underweight, poor condition, thin, emaciated, unthriftiness, ill thrift Other:Juvenile Sign
Respiratory Signs / Decreased respiratory rate Other:Juvenile Sign
Respiratory Signs / Mucoid nasal discharge, serous, watery Other:Juvenile Sign
Respiratory Signs / Nasal mucosal ulcers, vesicles, erosions, cuts, tears, papules, pustules Other:Juvenile Sign
Respiratory Signs / Purulent nasal discharge Other:Juvenile Sign
Skin / Integumentary Signs / Skin laceration, cut, tear, bite Other:Juvenile Sign

Epidemiology

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Adult P. downsi flies are non-parasitic and vegetarian feeding mainly on fruit. They oviposit in birds’ nests, where they lay eggs on nest material surfaces or on nestlings. Fly eggs have also been found on the nasal openings (nares) of nestlings. The eggs hatch into 1st instar larvae, which proceed to feed within the nestlings’ nares. The 2nd and 3rd instar stages reside in the nest base and emerge at night to feed on the blood and tissues of nestlings either by external attachment or by entering through the nares to feed internally (Fessl et al., 2006b; O’Connor et al., 2010b). Larvae pupate in the nest base after about 7 days, and emerge as flies approximately 14 days later. Female flies are known to mate with up to 5 males per laying event (Dudaniec et al., 2008) although other details of the fly’s mating behaviour are largely unknown. More larvae are found per nest on the 5 elevated Galapagos islands, which all have an elevated humid highland area, agricultural areas, higher annual rainfall, and large populations of breeding birds (Wiedenfeld et al., 2007).

Impact

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Economic Impact

About 27,000 people now live in the Galapagos, and more than 100,000 tourists visit the islands each year to experience the distinctive biodiversity, including its endemic birds. Darwin’s finches are iconic to the field of evolutionary biology, and attract large numbers of scientists, bird-watchers and biology enthusiasts to the islands. The loss of these species may ultimately lead to a reduction in eco-tourism opportunities for the Galapagos community.

Environmental Impact

P. downsi has been given the highest risk ranking for invasive organisms threatening biodiversity in the Galapagos Islands (Causton et al., 2006). Rare finch species such as the critically endangered mangrove finch (Camarhynchus heliobates) and Darwin’s medium tree-finch (C. pauper) are at an increased risk of extinction due to P. downsi parasitism (Fessl et al, 2006b; O’Connor et al., 2010d). C. pauper has high numbers of larvae per nest, over 40% of its nestlings die due to parasitism, and its sole population on Floreana Island (approximately 1600 individuals) is small and declining (O’Connor et al., 2010c, 2010d). Mist-netting surveys regularly observe adult finches with physically deformed beaks and nasal openings, a relict of P. downsi parasitism (Galligan and Kleindorfer, 2009). Fledglings that survive parasitism may experience continued fitness costs as adults in the form of: reduced sexual attractiveness and pairing success, reduced feeding efficiency, and increased susceptibility to disease; Kleindorfer et al. (2019) found that males with enlarged nostrils due to P. downsi had altered songs, increasing the time it took for them to find mates, and potentially leading to hybridization between finch species.

Prevention and Control

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Local Control

Nest bases can be sprayed with a 1% pyrethrin solution to kill larvae and help prevent re-infestation. Care must be taken to prevent contact between the nestlings and pyrethrin: the top layer of nest material is removed before treatment, and is placed back in the nest to form a layer between the nestlings and the pyrethrin-treated nest base. Other than spraying individual nests with pyrethrin, attempts to develop short- and long-term control methods such as trapping and using the sterile insect technique have so far been unsuccessful.

National and international control policy

The Galapagos National Parks and Charles Darwin Research Station have established quarantine measures to reduce the risk of further spread of this parasite, or new introductions of other pests. Incoming and outgoing cargo is inspected for organic material and live animals, new standards have been put in place for importing live birds, and research equipment is quarantined before scientists can begin projects on uninhabited islands. P. downsi is only listed as a quarantine pest in Ecuador.

References

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Bulgarella, M., Quiroga, M. A., Brito Vera, G. A., Dregni, J. S., Cunninghame, F., Mosquera Muñoz, D. A., Monje, L. D., Causton, C. E., Heimpel, G. E., 2015. Philornis downsi (Diptera: Muscidae), an avian nest parasite invasive to the Galápagos Islands, in mainland Ecuador. Annals of the Entomological Society of America, 108(3), 242-250. http://www.bioone.org/loi/esaa doi: 10.1093/aesa/sav026

Causton CE, Peck SB, Sinclair BJ, Roque-Albelo L, Hodgson CJ, Landry B, 2006. Alien insects: threats and implications for conservation of Galápagos Islands. Annals of the Entomological Society of America, 99(1):121-143. http://docserver.esa.catchword.org/deliver/cw/pdf/esa/freepdfs/00138746/v99n1s14.pdf

Couri MS, Tavares MT, Stenzel RR, 2006. Parasitoidism of chalcidid wasps (Hymenoptera, Chalcididae) on Philornis sp. (Diptera, Muscidae). Brazilian Journal of Biology, 66(2A):553-557. http://www.bjb.com.br

Dodge HR, Aitkin THG, 1968. Some new and little known species of Philornis Meinert (Diptera, Muscidae). Journal of the Kansas Entomological Society, 41:134-154

Dudaniec RY, Gardner MG, Donnellan S, Kleindorfer S, 2008. Genetic variation in the invasive avian parasite, Philornis downsi (Diptera, Muscidae) on the Galápagos archipelago. BMC Ecology, 8(13):(31 July 2008). http://www.biomedcentral.com/1472-6785/8/13

Dudaniec RY, Kleindorfer S, 2006. Effects of the parasitic flies of the genus Philornis (Diptera:Muscidae) on birds. Emu, Journal of the Royal Australasian Ornithologists Union, 106(1):13-20. http://www.publish.csiro.au/nid/96.htm

Dudaniec RY, Kleindorfer S, Fessl B, 2006. Effects of the introduced ectoparasite Philornis downsi on haemoglobin level and nestling survival in Darwin's Small Ground Finch (Geospiza fuliginosa). Austral Ecology, 31(1):88-94. http://www.blackwell-synergy.com/servlet/useragent?func=showIssues&code=aec

Dudaniec RY, Kleindorfer S, Fessl B, 2007. Interannual and interspecific variation in intensity of the parasitic fly, Philornis downsi, in Darwin's finches. Biological Conservation, 139:325-332

Dvorak M, Vargas H, Fessl B, Tebbich S, 2004. On the verge of extinction: a survey of the mangrove finch Cactospiza heliobates and its habitat on the Galápagos Islands. Oryx, 38(2):171-179

Fessl B, Couri MS, Tebbich S, 2001. Philornis downsi Dodge & Aitken, new to the Galapagos Islands (Diptera, Muscidae). Studia Dipterologica, 8(1):317-322

Fessl B, Kleindorfer S, Tebbich S, 2006. An experimental study on the effects of an introduced parasite in Darwin's finches. Biological Conservation, 127(1):55-61. http://www.sciencedirect.com/science/journal/00063207

Fessl B, Sinclair BJ, Kleindorfer S, 2006. The life-cycle of Philornis downsi (Diptera: Muscidae) parasitizing Darwin's finches and its impacts on nestling survival. Parasitology, 133(6):739-747. http://journals.cambridge.org/

Fessl B, Tebbich S, 2002. Philornis downsi - a recently discovered parasite on the Galápagos archipelago - a threat for Darwin's finches? Ibis (London), 144(3):445-451. http://www.blackwell-synergy.com/servlet/useragent?func=synergy&synergyAction=showAbstract&doi=10.1046/j.1474-919X.2002.00076.x

Galligan TH, Kleindorfer S, 2009. Naris and beak malformation caused by the parasitic fly, Philornis downsi (Diptera: Muscidae), in Darwin's small ground finch, Geospiza fuliginosa (Passeriformes: Emberizidae). Biological Journal of the Linnean Society, 98(3):577-585. http://www.blackwell-synergy.com/loi/bij

Geden CJ, Moon RD, Butler JF, 2006. Host ranges of six solitary filth fly parasitoids (Hymenoptera: Pteromalidae, Chalcididae) from Florida, Eurasia, Morocco, and Brazil. Environmental Entomology, 35(2):405-412. http://docserver.esa.catchword.org/deliver/cw/pdf/esa/freepdfs/0046225x/v35n2s29.pdf

Kleindorfer S, 2007. Nesting success in Darwin's small tree finch (Camarhynchus parvulus): evidence of female preference for older males and more concealed nests. Animal Behaviour, 74:795-804

Kleindorfer S, Dudaniec R, 2009. Love thy neighbour? Social nesting pattern, host mass and nest size affect ectoparasite intensity in Darwin's finches. Behavioral Ecology and Sociobiology, 63:731-739

Kleindorfer, S., Custance, G., Peters , K. J., Sulloway, F. J., 2019. Introduced parasite changes host phenotype, mating signal and hybridization risk: Philornis downsi effects on Darwin's finch song. Proceedings of the Royal Society B: Biological Sciences, 286(1904), article 20190461. https://royalsocietypublishing.org/doi/10.1098/rspb.2019.0461 doi: https://doi.org/10.1098/rspb.2019.0461

Legner EF, Brydon HW, 1966. Supression of dung-inhabiting fly populations by pupal parasites. Annals of the Entomological Society of America, 59(4):638-651

Marchiori CH, Pereira LA, Filho OMS, Borges VR, 2003. Parasitoids of flies collected on human faeces in Itumbiara County, Goias State, Brazil. Biotemas, 16(1):121-128

Mendonça E de C, Couri MS, 1999. New associations between Philornis Meinert (Diptera, Muscidae) and Thamnophilidae (Aves, Passeriformes). Revista Brasileira de Zoologia, 16(4):1223-1225

O'Connor JA, Dudaniec RY, Kleindorfer S, 2010. Parasite infestation and predation in Darwin's small ground finch: contrasting two elevational habitats between islands. Journal of Tropical Ecology, 26(3):285-292. http://www.journals.cup.org/action/displayAbstract?fromPage=online&aid=7452396&next=true&jid=TRO&volumeId=26&issueId=03

O'Connor JA, Robertson J, Kleindorfer S, 2010. Video analysis of host-parasite interactions in nests of Darwin's finches. Oryx, 44(4):588-594. http://journals.cambridge.org/action/displayJournal?jid=ORX

O'Connor JA, Sulloway FJ, Kleindorfer S, 2010. Avian population survey in the Floreana highlands: is Darwin's Medium Tree Finch declining in remnant patches of Scalesia forest? Bird Conservation International, 20(4):343-353. http://journals.cambridge.org/action/displayJournal?jid=BCI

O'Connor JA, Sulloway FJ, Robertson J, Kleindorfer S, 2010. Philornis downsi parasitism is the primary cause of nestling mortality in the critically endangered Darwin's medium tree finch (Camarhynchus pauper). Biodiversity and Conservation, 19(3):853-866. http://www.springerlink.com/content/p47h876t1034415l/?p=fe09c0be027a40f7b1c044251ec1d193&pi=15

Oliva A, 2008. Parasitoid wasps (hymenoptera) from puparia of sarcosaprophagous flies (Diptera: Calliphoridae; Sarcophagidae) in Buenos Aires, Argentina. Revista de la Sociedad Entomológica Argentina, 67(3-4):139-141

Silvestri L, Antoniazzi LR, Couri MS, Monje LD, Beldomenico PM, 2011. First record of the avian ectoparasite Philornis downsi Dodge & Aitken, 1968 (Diptera: Muscidae) in Argentina. Systematic Parasitology, 80(2):137-140. http://springerlink.metapress.com/link.asp?id=103002

Wiedenfeld DA, Jiménez GA, Fessl B, Kleindorfer S, Valerezo JC, 2007. Distribution of the introduced parasitic fly Philornis downsi (Diptera, Muscidae) in the Galapagos Islands. Pacific Conservation Biology, 13:14-19

Distribution References

Bulgarella M, Quiroga M A, Brito Vera G A, Dregni J S, Cunninghame F, Mosquera Muñoz D A, Monje L D, Causton C E, Heimpel G E, 2015. Philornis downsi (Diptera: Muscidae), an avian nest parasite invasive to the Galápagos Islands, in mainland Ecuador. Annals of the Entomological Society of America. 108 (3), 242-250. http://www.bioone.org/loi/esaa DOI:10.1093/aesa/sav026

CABI, Undated. CABI Compendium: Status inferred from regional distribution. Wallingford, UK: CABI

CABI, Undated a. CABI Compendium: Status as determined by CABI editor. Wallingford, UK: CABI

Causton C E, Peck S B, Sinclair B J, Roque-Albelo L, Hodgson C J, Landry B, 2006. Alien insects: threats and implications for conservation of Galápagos Islands. Annals of the Entomological Society of America. 99 (1), 121-143. http://docserver.esa.catchword.org/deliver/cw/pdf/esa/freepdfs/00138746/v99n1s14.pdf DOI:10.1603/0013-8746(2006)099[0121:AITAIF]2.0.CO;2

Dodge H R, Aitkin T H G, 1968. Some new and little known species of Philornis Meinert (Diptera, Muscidae). Journal of the Kansas Entomological Society. 134-154.

Fessl B, Couri M S, Tebbich S, 2001. Philornis downsi Dodge & Aitken, new to the Galapagos Islands (Diptera, Muscidae). Studia Dipterologica. 8 (1), 317-322.

Mendonça E de C, Couri M S, 1999. New associations between Philornis Meinert (Diptera, Muscidae) and Thamnophilidae (Aves, Passeriformes). Revista Brasileira de Zoologia. 16 (4), 1223-1225. DOI:10.1590/S0101-81751999000400030

Silvestri L, Antoniazzi L R, Couri M S, Monje L D, Beldomenico P M, 2011. First record of the avian ectoparasite Philornis downsi Dodge & Aitken, 1968 (Diptera: Muscidae) in Argentina. Systematic Parasitology. 80 (2), 137-140. http://springerlink.metapress.com/link.asp?id=103002 DOI:10.1007/s11230-011-9314-y

Wiedenfeld D A, Jiménez G A, Fessl B, Kleindorfer S, Valerezo J C, 2007. Distribution of the introduced parasitic fly Philornis downsi (Diptera, Muscidae) in the Galapagos Islands. Pacific Conservation Biology. 14-19.

Links to Websites

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WebsiteURLComment
Galapagos National Parkshttp://www.galapagospark.org
Global Invasive Species Databasehttp://www.issg.org/database/welcome/

Organizations

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Ecuador: Galapagos National Parks (Parque Nacional Galapagos) (PNG), Puerto Ayora, Isla Santa Cruz, Galapagos, http://www.galapagospark.org

Galapagos Islands: Charles Darwin Research Station (CDRS), run by the Charles Darwin Foundaton, Puerto Ayora, Isla Santa Cruz, Galapagos, http://www.darwinfoundation.org/english/pages/index.php

Contributors

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23/10/09 Original text by:

Jody O'Connor, School of Biological Sciences, Flinders University, GPO Box 1200, Adelaide, SA 5001, Australia

Sonia Kleindorfer, School of Biological Sciences, Flinders University, GPO Box 1200, Adelaide, SA 5001, Australia

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