2. • ON:
MYIASIS
POINTS COVERED………..
*MYIASIS GENERAL CONCEPT
*CLASSIFICATION
*CLINICAL REPRESENTATION IN HUMANS.
* SYNDROME
* SYMPTOMS
* DIAGNOSTIC
*CONTROL MEASURE
*TREATMENT
3. MYIASIS:
The term myiasis etymologically is derived from
Greek word myie -fly ,asis –disease.
Defn:
Myiasis is the parasitic infestation of the body of
a live mammal by fly larvae (maggots) that grow inside
the host while feeding on its tissue.
. Although flies are most commonly attracted to open
wounds and urine- or feces-soaked fur, some species
(including the most common myiatic flies,
the botfly, blowfly and screwfly) can create an
infestation even on unbroken skin and have been
known to use non-myiatic flies (such as the
common housefly) as vector agents for their parasitic
5. The various methods by which the larvae can enter
the human body include:
The eggs of the fly gets attached to the underside of a
female mosquito, and penetrates the unbroken skin while
the mosquito feeds
The eggs may also get attached with the clothing or towel
left out in the open to dry and then enter the human skin
The larva can enter the body through open wounds and ,
or even through unbroken skin
Some enter the human body through the nose and ears.
Larvae can reach the stomach and intestine when they are
accidently swallowed with food; this leads to Gastric or
Intestinal Myiasis
6. CLASSIFICATION….
According to tissues
Cavitary myiasis
where the infestation receives the name of the
affected organ, e.g., cerebral myiasis, aural myiasis,
nasal myiasis, and ophthalmomyiasis.
(migratory)
(wound)
7. CUTANEOUS MYAISIS:
cutaneous myiasis is skin infestation by the larvae (maggots) ….
Gasterophilus intestinalis
G. intestinalis is the most frequent cause of human migratory (or creeping) myiasis. G.
intestinalis is usually an intestinal parasite of horses and other equids. Humans are an
accidental host and become infested by direct contact with eggs on the horse's coat or
eggs may be directly laid onto human skin. The larva initially produces a papule . Then
the larva burrows to the lower layers of the epidermis, causing an intensely itchy,
snake-like, and raised red linear lesion that advances at one end and fades at the
other as it searches for a place to develop. The lesion can extend up to 30cm per day
and can continue for several months. The infestation may end spontaneously with or
without suppuration ….
Creeping myiasis (Migratory myiasis)
9. Furuncular myiasis:
Dermatobia hominis
Dermatobia hominis is found in Central and South America. The D. hominis female
fly lays her eggs onto foliage or carrier insects, most commonly mosquitoes. The
eggs are passed to humans by direct contact with foliage, or during a bite from the
carrier.
Once the eggs hatch, the larvae burrow painlessly into the host's skin producing a
small red papule (bump). The papule later becomes a furuncular-like (boil-
like) nodule with a central pore through which the organism breathes. Occasionally
the tail end of the larva can be seen through this pore.
Over the following 5 to 10 weeks the larvae further develop and burrow deeper
into the host's skin, forming a dome-shaped cavity. Symptoms include itching, a
sensation of movement, stabbing pain (often at night), and a serosanguinous (thin,
yellow or bloody) discharge.
The larvae eventually work their way back to the skin surface, then drop to the
ground where they pupate to form flies.
11. Traumatic myiasis.(wound myiasis)
Wound myiasis occurs when fly larvae infest open wounds in a living
host. Mucous membranes (e.g. oral, nasal, and vaginal membranes) and
body cavity openings (e.g. in or around the ears and eye socket) can also
be affected. Severe cases may be accompanied by fever, chills, pain,
bleeding from the infested site, and secondary infection. Blood tests
may show
raised neutrophils and eosinophils. Massive tissue destruction, the loss of
eyes and ears, erosion of bones and nasal sinuses, and death can occur.
Cochliomyia hominivorax (screw-worm fly) : infect around the ears,
nose and eye socket.
Chrysomya bezziana (screwworm fly): infests wounds, areas of soft
skin, and mucous membranes
12. Cochliomyia hominivorax
The female lays her eggs on the edges of wounds or healthy mucous membranes.
Within one day the eggs hatch and the larvae feed on tissue causing massive tissue
destruction and large deep lesions. An odour is produced which attracts more
female flies to lay additional batches of eggs. A single wound can contain up to
3000 larvae, which eventually fall to the ground to pupate.
13. Cavitary myiasis….
It is a type of myiasis where the infestation receives the
name of the affected organ.like,
In nasopharyngeal myiasis, the nose, sinuses, and pharynx
are involved.
Ophthalmomyiasis affects the eyes, orbits, and periorbital
tissue, and intestinal and urogenital myiasis involves
invasion of the alimentary tract or urogenital system.
14. BORADLY CLASSIFIED IN TO 3 TYPES……
Accidental, facultative & obligatory.
Accidental myiasis generally occurs when the eggs or larvae of
a fly contaminate foods that are ingested by an animal host. The
fly species is not parasitic but in order to survive they become
parasitic. Many times the flies will pass through the host’s body
unharmed but their presence can cause discomfort, nausea,
diarrhea, as well as other problems on their way through.
15. Facultative myiasis involves larvae that can be either free
living or parasitic. They are considered opportunistic and have
the ability to exploit living tissue. This is what occurs when
blow fly larvae that normally develop in carrion, invade open
sores on livestock.
Obligatory myiasis involves fly species whose larvae are
always parasitic (screwworms and bot flies). They require a
living host for development.
16. Clinical Presentation in humans…..
As there are so many different types of flies causing myiasis, clincial presentation
will differ depending on:
*Region
*Species
*Number of infesting maggots…
Myiasis is usually clinically classified according to where in the body the larvae are
located. They may be dermal, subdermal, cutaneous, nasopharyngeal, ocular,
intestinal/enteric or urnigenital. With open wounds, they are described as
traumatic. The lesion could also be described as furuncular, if it appears boil-like.
These are large, often painful and itchy nodules (that are highly associated
with Cordylobia and Dermatobia species). They often ooze a sort of serum/pus with
a little blood.
17. #Myiasis is termed “creeping” when you’re able to trace the path of the larvae
beneath the skin.
#Description of skin lesion: A small (2-3 mm) papule that looks similar to an
insect bite will develop and soon enlarge (10-35 mm, 5-10 mm in height). It will
be surrounded by a larger area of induration. This usually takes less than 24
hours. There will be a breathing hole (“punctum”) in the center. The larvae’s
posterior (“small, white, thread-like”) or fluid/bubbles may be seen through
the hole.
#particularly Dermatobia hominis because of its spines as the larva
moves) is a sharp pain or stabbing sensation with larvae wiggling
#Nasal myiasis may obstruct nasal passages, cause severe irritation, and
possibly facial swelling/edema and fever.
#With aural myiasis you might feel crawling sensations and hear buzzing
noises. There may be a bad smelling discharge. If the larvae is in the middle
ear, they may start a trek towards the brain.
#Opthalmomyiasis may also occur- this is when the larvae infect the eye.
Irritaation, edema, and pain would ride along with it.
18. Syndrome + symptoms
How myiasis affects the human body depends on where the
larvae are located. Larvae may infect
dead, necrotic (prematurely dying) or living tissue in various
sites: the skin, eyes, ears, stomach and intestinal tract. They
may invade open wounds and lesions or unbroken skin. Some
enter the body through the nose or ears. Larvae or eggs can
reach the stomach or intestines if they are swallowed with
food and cause gastric or intestinal myiasis
19. presentations of myiasis and their symptoms
Syndrome Symptoms
Cutaneous myiasis
Painful, slow-developing ulcers or furuncle- (boil-)
like sores that can last for a prolonged period
Nasal myiasis
Obstruction of nasal passages and severe irritation.
In some cases facial edema and fever can develop.
Death is not uncommon.
Aural myiasis
Crawling sensations and buzzing noises. Smelly
discharge is sometimes present. If located in the
middle ear, larvae may get to the brain.
Ophthalmomyiasis
Fairly common, this causes severe irritation,
edema, and pain
20. DIAGNOSIS…
The diagnosis of myiasis is made by the finding of fly larvae in tissue.
Identification to the genus or species level involves comparing certain
morphological structures on the larvae, including the anterior and posterior
spiracles, mouthparts and cephalopharyngeal skeleton, and cuticular spines.
Travel history can also be helpful for genus or species-level identification
The diagnosis should not be made on the larvae alone.
The family and genus of the insect may be
determined by the larval morphology…
21. Species of diptera Country of origin Incubation period Appearance of mature maggot
Cochliomyia hominivorax Central & South America 4-8 days
Typical maggot shape, 15-17mm
long, bands of spines encircling
anterior margin of each body
segment.
Cordylobia
anthropophaga
Central & Tropical Africa 10-12 days
Oval, 11-15mm, 3 curved slits in
spiracles, numerous small black
spines.
Cordylobia rodhaini Central & Tropical Africa 10-12 days
Up to 23mm long, scattered spines, 3
sinuous slits in each posterior
spiracle.
Dermatobia hominis Central & South America 5-12 weeks
18-25mm long, pair of flower like
anterior spiracles, spines in rows
Diagnosis may also be made with the help of x-ray (mammography in the rare
case of furnicular lesions of the breast) and ultrasound, to reveal
microcalcitations hinting towards myiasis.
22. PREVENTIONS….
Take extra care going to tropical areas and spending a lot of time outside.
Cover your skin to limit the area open to bites from flies, mosquitoes, and ticks.
Use insect repellant and follow Travelers Health guidelines.In areas where myiasis is known to occur,
protect yourself by using window screens and mosquito nets.
In tropical areas, iron any clothes that were put on the line to dry.
Keeping dishes and pans covered
Maintain good personal hygine
Keep wounds clean
Keep home environment clean
23. TREATMENT…….
• Surgically enlarge the area of infestation and remove the larvae with forceps.
This method is often used for D. hominis, whose larvae have backward-pointing
spikes that prevent easy removal. Damaging the larvae can release fly antigens
that could trigger severe immune reaction.
• For treating human wound myiasis by C. hominivorax: topical administration of
1% ivermectin in propylene glycol for 2 hours.
• Injection of Xylocaine underneath an infested nodule, to force the larvae out .
• Cover the pore containing the larvae with butter, mineral oil, or petrolatum.
The larvae will crawl out of the pore to avoid suffocating.
