Myiasis (with special reference to Waterfowl, Hedgehogs, Elephants and Bears)
 

Disease Summary

Alternative Names (Synonyms)

• Blowfly strike
• Fly larvae infestation
• Maggot infestation

See also: 

• Bots (Gastric Myiasis) in Elephants
• Elephant Foot Fly Infection
• Old World Screw-worms in Elephants
• Skin Warbles in Elephants

Disease Type

Infectious/Non-Infectious Agent associated with the Disease

• Flesh fly Wohlfahrtia opaca, black blowfly Phormia regina
• Calliphorid flies (Bluebottles, screw-worms etc.) which lay eggs on wounds, infected skin or skin dampened or soiled with normal discharges or faeces (B46, B208.2.w2)
• Lucilia spp. (J15.21.w1, B224, B228.9.w9, B291.12.w12); Lucilia sericata in wounds of two hedgehogs in Austria. (J192.71.w1)
• Calliphora spp. (J15.21.w1)
• Sarcophagidae blowflies: Calliphora vicina R.D and Lucilia illustris (Mg.) as causes of primary myiasis, also Lucilia ampullacae, Lucilia caesar and Sarcophaga melanura. (J158.46.w1)
• Hemipyrellia fernandica in Kenya and South Africa. (J157.82.w1)
• In a Ursus arctos - Brown bear in a zoo in New Mexico, the larvae were not identified but the possibility of Callitroga hominovorax (true screw-worm) was suggested. (J196.54.w1)
• Cochliomyia hominivorax (screwworm) was reported in one Ursus americanus - American black bear in Marion County in Florida, USA, but the fly was eradicated from Florida in the late 1950s/early 1960s. (B419.14.w14)

Further information on Disease Agents has only been incorporated for agents recorded in species for which a full Wildpro "Health and Management" module has been completed (i.e. for which a comprehensive literature review has been undertaken). Only those agents with further information available are linked below:

Infective "Taxa"

• Wohlfahrtia opaca (Invertebrate Species Summary)
• Phormia regina (Invertebrate Species Summary)
• Calliphoridae - (Family)
• Sarcophagida - (Family)

Non-infective agents

Physical agents

References

Disease Author

Major References / Reviews

Code and Title List

• B11.3.w10, B15, B32.32.w12, P4.1992.w1.
• B208.2.w2, J15.21.w1, B212.w26, B224, B228.9.w9, B228.11.w11, B259.w7, B291.12.w12, B337.3.w3

Other References

Code and Title List

In bears
B419.14.w14, J196.54.w1, 

Detailed Clinical and Pathological Characteristics

General

• Larvae may infest wounds, weeping skin or normal orifices (eyes, nose, ears, anus, vulva, prepuce) (B208.2.w2, J15.21.w1, B224, B228.9.w9)

• Larvae may infest wounds or 'weeping' skin and move into living flesh; larvae may also enter newly-hatched downies at umbilicus or even through the cracked eggshell during hatching (B15, B32.32.w12, P4.1992.w1).

• Larvae may be found in body orifices or associated with wounds. (J15.21.w1, J192.71.w1, B156.7.w7, B228.9.w9, B259.w7, B291.12.w12)

• Larvae may be found in neglected wounds of Elephas maximus - Asian Elephant. (B212.w26)

• Larvae on wounds. (J196.54.w1)

Clinical Characteristics

• Fly eggs/maggots visible in the tissue of a living animal; usually associated with wounds or with normal body orifices in a debilitated animal. (B224, B208.2.w2)

• Maggots in tissues of a living bird, often associated with open wounds or weeping skin (B15, B32.32.w12, P4.1992.w1).

• Maggots or eggs of blowflies may be found in and around normal orifices (eyes, nostrils, mouth, ears, anus, vagina, prepuce), wounds, infected areas of skin or damp areas of skin e.g. skin folds of the axilla).
  • May cause direct damage to superficial and deeper tissues and may also lead to secondary infection..
  • Severe infestation, involving deep tissues, may be fatal or require euthanasia on welfare grounds.

(J158.46.w1,V.w44, J15.21.w1, J192.71.w1, B156.7.w7, B228.9.w9, B259.w7, B291.12.w12)

• Maggots may be found in neglected skin wounds of Elephas maximus - Asian Elephant. (B212.w26)
  • There is often a thin, offensive discharge and a fetid odour associated with the infected wound. (B212.w26)

• Hundreds of maggots were seen infesting a raw open fight wound (about 15 cm long by 10 cm wide) on the nape of an adult grizzly bear (Ursus arctos - Brown bear) in a zoo in New Mexico. (J196.54.w1)
• Recurrent infestation with fly larvae in chronic foot lesions in an Ursus maritimus - Polar bear.(P1.1979.w3)

Incubation

Mortality / Morbidity

• Deaths in newly-hatched ducklings reported. (B15)

• Maggots and eggs are commonly found on e.g. casualty animals and orphaned animals in warm weather.
• Mortality associated with myiasis in hedgehogs has been reported, also severe infection may require euthanasia on welfare grounds.
• (B208.2.w2, J15.21.w1, B224, B228.9.w9, B259.w7, V.w44)

Pathology

• Fly larvae (maggots) in subcutis area (under skin), and deeper into tissues, or in wounds (P4.1992.w1, B15).
• Large amounts of soft tissue may be consumed in a few hours (B11.3.w10)

Human Health Considerations

Disease / Agent has been reported in either the wild or in captivity in:

• Any mammal or bird which is debilitated or has damage to the skin is susceptible to flystrike - Myiasis.
• Newly-hatched Northern shoveler Anas clypeata and blue-winged teal Anas discors ducklings; attacked by Flesh fly Wohlfahrtia opaca (B15).
• Geese (wound infection with Phormia regina, black blowfly)(B32.32.w12).

In Hedgehogs:

• In 18 hoglets about 8-14 days old, two older juveniles and one adult (caught in a wire fence) hedgehog Erinaceus europaeus in Denmark, mid-August to early September 1977 in Denmark. (J158.46.w1)
• Common in hedgehogs in the UK. (B228.9.w9)
• Occasionally found on young and sick hedgehogs. (B214.3.26.w11)
• Juvenile hedgehogs Erinaceus europaeus found by members of the public abandoned/accidentally separated from their mother and which did not survive. (J180.26.w1)
• In juveniles and adult: in wounds and in body orifices (mouth, nose, ears), requiring euthanasia in severe cases. (V.w44)
• Lucilia sericata in wounds of two hedgehogs in Austria. (J192.71.w1)
• In hedgehogs with wounds, also in hoglets without obvious injuries. (B259.w7)

In Elephants:

• Occurs in Elephas maximus - Asian Elephant in Asia. (B212.w26)

In Bears:

• Cochliomyia hominivorax (screwworm) was reported in one Ursus americanus - American black bear in Marion County in Florida, USA, but the fly was eradicated from Florida in the late 1950s/early 1960s. (B419.14.w14)
• Unidentified fly larvae, possibly Callitroga hominovorax (true screw-worm) were found on a Ursus arctos - Brown bear in a zoo in New Mexico. (J196.54.w1)

Further information on Host species has only been incorporated for species groups for which a full Wildpro "Health and Management" module has been completed (i.e. for which a comprehensive literature review has been undertaken). Host species with further information available are listed below:

 Host Species List

• Anas clypeata - Northern shoveler
• Anas discors - Blue-winged teal
• Anser anser domesticus - Domestic goose

MAMMALS:

• Bears (Ursidae - Bears (Family))
• Elephants (Elephantidae - Elephants (Family))
• Elephas maximus - Asian Elephant
• Erinaceus europaeus - West European Hedgehog
• Ursus americanus - American black bear
• Ursus arctos - Brown bear

(List does not contain all other species groups affected by this disease)

Disease / Agent has been specifically reported in Free-ranging populations of:

• Any mammal or bird which is debilitated or has damage to the skin is susceptible to flystrike - Myiasis.
• Newly-hatched Northern shoveler Anas clypeata and blue-winged teal Anas discors ducklings; attacked by Flesh fly Wohlfahrtia opaca (B15).

In Hedgehogs:

• In 18 hoglets about 8-14 days old, two older juveniles and one adult (caught in a wire fence) hedgehog Erinaceus europaeus in Denmark, mid-August to early September 1977 in Denmark. (J158.46.w1)
• Common in hedgehogs in the UK. (B228.9.w9)
• Occasionally found on young and sick hedgehogs. (B214.3.26.w11)
• Juvenile hedgehogs Erinaceus europaeus found by members of the public abandoned/accidentally separated from their mother and which did not survive. (J180.26.w1)
• In juveniles and adult: in wounds and in body orifices (mouth, nose, ears), requiring euthanasia in severe cases. (V.w44)
• In hedgehogs with wounds, also in hoglets without obvious injuries. (B259.w7)

In Bears:

• Cochliomyia hominivorax (screwworm) was reported in one Ursus americanus - American black bear in Marion County in Florida, USA, but the fly was eradicated from Florida in the late 1950s/early 1960s. (B419.14.w14)

Further information on Host species has only been incorporated for species groups for which a full Wildpro "Health and Management" module has been completed (i.e. for which a comprehensive literature review has been undertaken). Host species with further information available are listed below:

Host Species List

• Anas clypeata - Northern shoveler
• Anas discors - Blue-winged teal

MAMMALS:

• Bears (Ursidae - Bears (Family))
• Erinaceus europaeus - West European Hedgehog
• Ursus americanus - American black bear

(List does not contain all other species groups affected by this disease)

General Information on Environmental Factors/Events and Seasonality

In hedgehogs:

• In summer. (V.w44)

Regions / Countries where the Infectious Agent or Disease has been recorded

• In Erinaceus albiventris in Kenya and Erinaceus frontalis in Africa, with Hemipyrellia fernandica identified as the fly involved. (J157.82.w1)
• In Elephas maximus - Asian Elephant in Asia. (B212.w26)

Regions / Countries where the Infectious Agent or Disease has been recorded in Free-ranging populations

• Cochliomyia hominivorax (screwworm) previously was an important parasite in Florida, USA but the fly was eradicated in the late 1950s/early 1960s. (B419.14.w14)

General Information on Investigation / Diagnosis

• Presence of larvae on the eyes, within natural orifices (ears, nose, mouth, anus, prepuce, vulva, cloaca) or on open wounds or within tissues. Check carefully using a good light source. (B15, B224, B291.12.w12).

• Physical Examination of Birds - General
• Necropsy of Birds - General
• Physical Examination of Mammals
• Necropsy of Mammals
• History & Documentation
• Treatment and Care - General
• Environmental Assessment
• Chapter 2 - B36 Field Manual of Wildlife Diseases - Specimen Collection and Preservation
• Chapter 3 - B36 Field Manual of Wildlife Diseases - Specimen shipment
• Appendix A - B36 Field Manual of Wildlife Diseases - Sample specimen history form

Similar Diseases (Differential Diagnosis)

• If found on a carcass, must be distinguished from infestation by larvae after death. (V.w5)

Specific Medical Treatment

• Direct application of  an appropriate insecticide:
  • e.g. coumaphos (Negasunt, Bayer) (J15.21.w1, B259.w7)
  • Coumaphos (Negasunt, Bayer) may be used on adults. (B156.7.w7)
    • Negasunt may cause toxicity in hedgehogs. (B151)
  • Topical application of Ivermectin (Ivomec Injection for Cattle, Merial) diluted 1:9 with water just prior to use, up to (maximum) 1 mL of the mixture. (B151)
  • Fenthion (Tiguvon 10%, Bayer), applied at one drop per 100 g bodyweight to the back of the hedgehog has been found effective. (B291.12.w12)
  • For myiasis in the ears, one or two ear drops (GAC Ear Drops, Arnold's Veterinary Products) may be useful after physical removal of eggs and maggots in case any have been missed. (B151)
  • For the eyes, a chloramphenicol eye ointment may be applied following physical removal of eggs or recently-hatched maggots, to suffocate any which remain. (B151)
• Parenteral Ivermectin may be given in case one or two maggots have been missed during physical removal. (B151)
• Parenteral antibiotics (e.g. long-acting Amoxycillin) should be given to avoid secondary bacterial infection. (B151, B259.w7)
• Flunixin meglumine may be given to individuals from which large maggot burdens have been removed (analgesic, anti-inflammatory and anti-toxic). (B151)
• In an Ursus arctos - Brown bear, when circumstances did not allow restraint, an organophosphate insecticide in appropriate dilution was thrown over the wound on two successive days. This was apparently successful, with the wound closing and healing well. (J196.54.w1)

• Treatment and Care - General

General Nursing and Surgical Techniques

• Keep wounds cleaned.
• Physically remove visible larvae from wounds, eyes, ears and other orifices. (B214.3.26.w11, B228.11.w11)
  • Forceps and a tooth brush may be useful for removing maggots from the hair and spines. (B291.12.w12)
  • Careful manual removal is important for eye infestations.
  • Flushing of wounds and orifices may assist in completing the removal of small larvae. (B259.w7)
    • A sterile non-irritant fluid should be used for flushing maggots from the eyes. (B337.3.w3)
  • A glass pipette and bulb may be used to gently suction maggots away. (B224)
  • A dilute antiseptic solution may be used to flush out the ears. (B259.w7)
• A hair drier may be used to gently heat and dry the skin to encourage maggots to move out of a wound. (B228.11.w11, B259.w7)
• Fingertip pressure from behind the eye socket may be used to expel fly eggs from the eye socket. (B151)
• Dripping 30% alcohol into the ears encourages maggots to crawl out.  (B228.11.w11, B291.12.w12)
• Hydrogen peroxide (H₂O₂) may be used on less sensitive areas. (B291.12.w12)
• A fine "nit comb" may be used to remove fly eggs and very small maggots from the hair coat. (B337.3.w3)
• If a chemical has been used to kill maggots infecting wounds it is important to make sure that all the dead maggots are removed, for example using tweezers, to ensure that they do not remain in the wound and rot. (B337.3.w3)
• If, following removal of maggots, the hedgehog continues scratching at one area of its body (e.g. an ear) check that site in case some maggots are still present.  (B337.3.w3)

In elephants:

• Physical removal of maggots using forceps is recommended. It is important to remember that there may be pockets of the wound, not immediately visible, in which more maggots may be present, therefore the wound should be inspected for the following two or three days for any maggots which were not removed initially. (B212.w26)

• Treatment and Care - General

Preventative Measures

• Carefully inspect wounds/lesions and natural orifices of weak/juvenile animals for fly eggs/larvae, particularly in the warmer months, and remove these.
• Keep wounds clean.
• Apply topical insecticides to wounds/lesions

(B11.3.w10, B208.2.w2)

• Treatment and Care - General
• Preventative Medicine for Birds - General
• Preventative Medicine for Mammals

Environmental and Population Control Measures

• Preventative Medicine for Birds - General
• Preventative Medicine for Mammals
• Environmental and Population Management