Myiasis

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Myiasis

• 511 Zoo
• Prepared by Dr. Reem Alajmi

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Defention

• Myiasis can be defined as the invasion of organs
  and tissues of humans or other vertebrate animals
  with dipterous larvae, which for at least a
  period feed upon the living or dead tissues or,
  in the case of intestinal myiasis, on the hosts
  ingested food.

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Types of myiasis

• Different terms are used to describe myiasis
  which affects different parts of the body. For
  example, cutaneous, dermal or subdermal myiasis,
  urogenital myiasis, ocular myiasis,
  nasopharyngeal myiasis, etc.
• Myiasis may be obligatory or facultative.

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Obligatory myiasis

• In obligatory myiasis it is essential for the fly
  maggots to live on a live host for at least a
  certain part of their life such as larvae of
  Chrysomaya bezziana and Dermatobia hominis.

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Facultative myiasis

• In facultative myiasis larvae are normally
  free-living, but under certain conditions they
  may infect living hosts. Several types of fly,
  including species of Calliphora, Lucilia and
  Sarcophaga, which normally breed in meat may
  cause myiasis in people by infecting festering
  sores and wounds.
• There is no obligatory intestinal myiasis of
  humans, maggots may enter human digestive system
  accidentally. In contrast, obligatory intestinal
  myiasis occurs in animals.

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Types of myiasis

• Occasionally facultative urogenital myiasis
  occurs in humans this usually involves larvae of
  Musca or Fannia species. Where the adult female
  attracted to unhygienic discharges and lay their
  eggs near genital orifices, and on hatching the
  minute larvae enter the genital orifice and pass
  up the urogenital tract. Considerable pain may be
  caused by larvae obstructing these passages, and
  mucus, blood and eventually larvae may be
  discharged during urination.

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Types of myiasis

• Flies that can cause myiasis are classified into
  three families
• - Calliphoridae (non-metallic flies and
  metallic flies).
• - Sarcophagidae.
• - Oestridae.

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Calliphoridae Non-metallic flies

• 1- Cordylobia anthropophaga
• - the common name is tumbu or mango fly.
• - It has three larval instars, each of them has
  different body shape.

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Calliphoridae Non-metallic flies

• Medical importance
• - The larvae cause boil-like swellings on
  almost any part of the body. These swellings may
  become sore and inflamed, but they dont usually
  contain pus.
• - Generally just one or two larvae are found
  in patient however more than 60 larvae have been
  recovered from a person

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Calliphoridae Non-metallic flies

• The standard method of extracting a larva is to
  cover the small hole in the swelling with
  medicinal liquid paraffin. This prevents the
  larva from breathing through its posterior
  spiracles with the result that it wriggles a
  little, further out of the swelling to protrude
  the spiracles. In so doing it lubricated the
  pocket in the skin, and the larva can then
  usually be extracted by gently pressing around
  the swelling.

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Calliphoridae Metallic flies

• Cochliomyia hominivorax
• - Its common name is New World screwworm
• Genus Chrysomyia
• - Its common name is Old World screwworms
• 10 species are present, but the most
• important one is Chrysomya bezziana,
• because its larvae are obligatory parasites.

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Medical importance of screwworms

• Larvae are obligatory parasites of living tissues
  and cause human myiasis, which can be very sever,
  resulting in considerable damage and
  disfigurement, especially if the face is
  attacked.
• Larvae mainly invade natural orifices, such as
  the nose, mouth, eyes or vagina, they can cause
  excruciating pain and misery.
• Larvae may cause permanent damage.

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Medical importance of screwworms

• Formerly maggots in open wounds or body openings
  were often removed my irrigating infested areas
  with 5-15 chloroform mixed with vegetable oil,
  but because of health and safety regulations,
  ethanol can be substituted for chloroform.
• Surgery may be necessary to exposé deeply
  embedded larvae.
• Both screwworms species may cause myaisis in
  cattle, goats, sheep and horses and are
  responsible for enormous economic losses to
  livestock industry.

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Genus LuciliaGenus Calliphora

• Greenbottles in the genus Lucilia
• Bluebottles in the genus Calliphora
• There medical importance
• - The dirty habit of blowflies of feeding on
  excreta, decaying material and virtually all
  foods of humans makes them potential vectors of
  numerous pathogens. However, their medical
  importance is usually associated with facultative
  myiasis.

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Genus LuciliaGenus Calliphora

• Larvae are develop in foul-smelling wounds and
  ulcerations, especially those producing pus.
• They have been recorded in hospitals underneath
  the bandages and dressing of patients.
• Removal of these maggots usually without any
  problems because they can be picked out of wound
  with sterile forceps and antibiotic dressings
  applied.

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Sarcophagidae Flesh-flies

• Only species in the genera Sarcophaga and
  Wohlfahrtia are of medical importance.
• Sarcophaga medical importance
• - Larvae may occur in wounds cause facultative
  myiasis, but usually causing little damage
  because they feed mainly on necrotic tissues.
• - Accidentally they may cause intestinal
  myiasis.

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Sarcophagidae Flesh-flies

• Wohlfahrtia medical importance
• - The most common species is W. magnifica,
  causes obligatory myaisis in humans and animals
  (camels, domestic livestock and dogs)
• - Some 120 170 larvae are deposited, often in
  several batches, in scratches, wounds, sores and
  ulcerations.
• - In people the ears, eyes and nose are
  frequently infested, and this can result in
  deafness, blindness and even death.

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Oestridae Bot-flies

• The family Oestridae comprises four subfamilies,
  three of which (Oestrinae, Gasterophilinae and
  Hypodermatinae) contain important obligate
  parasites of domesticated animals. The subfamily
  Cuterebrinae contains species that cause myiasis
  to human, rodents, monkeys and livestock.
• The human botfly Dermatobia hominis invade the
  subcutaneous tissues of humans on various parts
  of the body, including head, arms, abdomen,
  buttocks, thighs, scrotum and axillae.

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Oestridae Bot-flies

• They produce boil-like swellings which suppurate
  and this may attract other myiasis-producing
  flies.
• Surgical removal of larvae under sterile
  conditions may be necessary.

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Other myiasis producing flies

• The black blowfly, sometimes cause facultative
  myiasis in human.
• Several species of flies commonly cause myiasis
  in livestock. There are, for example, flies
  infesting donkeys and camels, others infesting
  sheep and goats, cattle and horses and donkeys.

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• In a group of 3, write a short report on
  different types of myaisis based on the location
  of myiasis. Explain one of these types by giving
  example of the cause, the host, the medical
  importance if it has.
• Note each group should explain different type of
  myiasis.