Myiasis ....a parasitic disease.

Myiasis with all its types,symptoms,causative agents ,diagnosis and treatment.

1. PARASITOLOGY SEMINAR PRESENTATION BY U.ID

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 larvae.

4. Myiatic flies…. Bot fly Blow fly Screw fly

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 )

8. 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.

10. Bot fly

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.

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