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Myiasis. By Karma Tiberg Biology 4800 Spring 2011. Outline. What is myiasis? Flies causing myiasis Life cycle Effects on livestock Effects on humans A few types of myiasis in humans Treatment options. What is Myiasis?.

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By Karma Tiberg

Biology 4800

Spring 2011

  • What is myiasis?
  • Flies causing myiasis
  • Life cycle
  • Effects on livestock
  • Effects on humans
  • A few types of myiasis in humans
  • Treatment options
what is myiasis
What is Myiasis?
  • Myiasis is the disease caused by the feeding of larval dipterans on living and necrotic tissue, liquid body-substance, or ingested food
  • Described in two ways:
    • Location of the affected area
    • Relationship between the fly and its host (obligate, facultative, or accidental)
  • Can affect all vertebrates including humans!
the flies
The Flies
  • There are three main families of flies that cause myiasis:
    • Oestridae (obligate parasites)
    • Calliphoridae (obligate or facultative)
    • Sarcophagidae (obligate or facultative)
effects on livestock
Effects on Livestock
  • Pests that cause huge economic losses worldwide (in the hundreds of millions annually)
  • Cause stress to the livestock and reduction in livestock health
  • High infection levels, or migration of larvae into important regions can lead to death
  • Damage to the hides
effects on humans
Effects on Humans
  • Mainly a problem for rural populations especially in tropical and subtropical regions
    • A problem of countries with a low socioeconomic status, limited access to health care, and poor hygienic practices
  • A problem for elderly people
  • Most commonly infected by obligate and facultative fly species
  • Humans may become infected if they spend extended periods of time around livestock
  • Depending on the species of fly and the type of infection, the effects can range from minor to severe and potentially fatal
  • Secondary infections are common
types of myiasis in humans
Types of Myiasis in Humans
  • Cutaneous
    • Furuncular
    • Creeping
    • Wound
  • Nasopharyngeal
  • Opthamomyiasis
  • Oral
  • Intestinal
  • Cerebral
  • Furuncular
    • Infection of skin on the scalp, face and extremities
    • Swelling localized at the area of infection
    • Small opening is maintained in the skin to promote respiration, and waste excretion by the growing larvae
    • Mainly a problem in tropical locations, but can be a problem in the U.S. and Canada
      • Human botfly - Dermatobiahominis(family Oestridae)
      • Tumbu fly – Cordylobiaanthropophaga(family Calliphoridae)
      • *Wohlfahrtia vigil – (family Sarcophagidae)

2. Creeping Myiasis

  • Infection of humans by the larvae of horse bot flies (Gasterophilus) and cattle bot flies (Hypoderma)
    • Both in the family Oestridae
  • Larvae typically do not develop in humans
  • Travel around the epidermis looking for proper host cues
    • Painful “Migrating lumps” and the production of long tunnels
  • Gasterophilus tunnels are located in the epidermal layer
  • Hypoderma tunnels are located deep in subcutaneous tissue but may migrate to other tissues
  • Wound Myiasis
    • Flies deposit eggs or larvae on

the outer margins of a wound or sore

    • Larvae feed and travel through living flesh
    • Can be fatal if left untreated
    • Wound myiasis can develop into other forms of myiasis depending on where the larvae migrate in the body
      • Screwworm Flies - Cochliomyiahominivorax, Chrysomyabezziana
      • Wohlfahrtiamagnifica (family Sarchphagidae)
      • Bluebottle flies
  • Less common in humans
  • Occurs in people who spend

extended periods of time around livestock

      • Sheep bot fly (Oestrus ovis)
  • Fly inserts larva into the nostril of host
  • Larvae can cause extensive damage to the nose, sinuses and pharynx due to the feeding on living and necrotic tissue
  • In some cases larvae can migrate out of the sinuses into the eyes, ears, mouth or brain causing myiasis in those locations
  • Affects the eyes, orbits and periorbital tissue
  • Larvae cause the destruction of these tissues through feeding and migration
  • Often caused by migrating fly larvae or flies that preferentially infect soft and susceptible tissues
  • May lead to blindness if not treated
oral myasis
Oral Myasis
  • Infestation of the oral cavity by fly larvae
      • Sheep bot fly
  • Migratory larvae, or opportunistic infection of a sore or lesion (wound myiasis)
      • varejeira fly - Cochliomya hominivorax
intestinal myiasis
Intestinal Myiasis
  • This is often a result of accidental infection
    • Ingestion of fly eggs or larvae in water or contaminated food and subsequent larval development within intestines
  • Can be a result of migration of larvae
cerebral myiasis
Cerebral Myiasis
  • Extremely rare
  • A traumatic skull fracture followed by the depositing of eggs or larvae into the wound
      • Human bot flies
      • Screwworm Flies
  • Migration of larvae into the brain originating from another area of the body
      • cattle bot flies (Hypoderma)
shoo fly don t bother me
Shoo fly, don’t bother me!
  • Preventative measures are usually the best way to minimize human (or livestock) infection with myiasis
    • Use of insect repellents with DEET
    • Improve hygienic practices
    • Limit exposure to livestock and other common hosts, or treatment of livestock with insecticides and larvicidal drugs (endectocides)
    • Introduction of coprophageous insect species
  • Suffocation of larvae within the skin and then careful extraction of the larvae (Furuncular)
  • Treatment with Ivermectin products
  • Surgery
  • Caca, I., K. Unlu, S. Soker Cakmak, K. Bilek, B. Sakalar and G. Unlu. 2003. Orbital myiasis: case report. Japanese Journal of Ophthalmology 47: 412-414
  • Colwell, D.D., D. Otranto and J. R. Stevens.2009. Oestrid flies: eradication and extinction versus biodiversity. Trends in Parisitology 25: 500-504
  • Lucas, E. M., C. Diez, A. Gutierrez, F. Montiaga, J. Arnaiz, A. Gonzalez Mandly, E. Sanchez and N. Valle. 2008. Unusual MRI findings in a patient with history of frontal fracture and skin infestation by fly larvae, as a possible sign of intracerebral myiasis. Clinical Neurology and Neurosurgery.110: 725-728
  • Robbins, K. and A. Khachemoune. 2010. Cutaneous myiasis: a review of the common types of myiasis. International Journal of Dermatology 49: 1092-1098
  • Shinohara, E. H., M. Z. Martini, H. G. Oliveira Neto and A. Takahashi. 2004. Oral myiasis treated with ivermectin: Case report. Brazilian Dental Journal.15: 79-81
  • 1999, Intestinal Myiasis caused by Eristalis tenax, Journal of Clinical Microbiology 37: 3082