L5: Myiasis Flashcards
What is the definition of Myiasis?
It is the invasion of the tissues of man or animals by larvae of dipterous (have 2 wings) flies.
What is Myiasis classified according to?
- According to the habitat (site of invasion)
- According to the habit (biological habit of the fly)
What are the types of Myiasis according to the habitat?
Internal: intestinal and urogenital
External: cutaneous, ocular, nasopharyngeal, and aural
How does intestinal Myiasis occur?
Flies may deposit their eggs or larvae on human food or on the anus (particularly in children in rural areas) during sleep or defecation in open places.
What are the symptoms of intestinal myiasis?
Larvae find their way to the intestine and cause non-specific symptoms like nausea, vomiting, abdominal discomfort, or pain with diarrhea.
Where can we find larvae in case of intestinal myiasis?
Living and dead larvae appear in stools or vomitus
What are examples of larvae that cause intestinal myiasis?
larvae of Calliphora, Lucilia, Musca, and Fannia.
How does urogenital myiasis take place?
Larvae may enter through urinary or genital orifices or through lesions on orifices during urination in open places.
What are the symptoms of urogenital myiasis?
They may cause obstruction to the urine flow with dysuria or inflammation in the urinary passage with pus, mucus, and blood in the urine.
Where can we find the larvae in case of urogenital myiasis?
Larvae are passed in the urine.
What are examples of larvae that cause urogenital myiasis?
Fannia (the latrine fly) , Musca, Calliphora and Sarcophaga
How does cutenous myaisis take place?
- This occurs when wounds or ulcers are invaded by larvae of the flies.
- Sometimes, larvae may invade intact skin causing boil-like lesions.
What are the symptoms of cutaneous myiasis?
C/P: Sever pruritis, creeping eruption, or boil-like lesion may be presenting symptoms.
What are examples of larvae that can cause cutaneous myiasis?
Example: . Wohlfahrtia, Chrysomia ,Cordylobia and Dermatobia.
How do ocular or nasopharyngeal myiasis take place?
Larvae of some flies are attracted to the discharge coming from the eye or the nose, to find their way to the conjunctiva or the nose and may sometimes reach the brain.
What are the symptoms of ocular or nasopharyngeal myiasis?
- Severe pain in the eye is the first complaint in ocular myiasis followed by lacrimation and conjunctival irritation.
- c/p: Nasal myiasis presented with foul-smelling discharge followed by nasal obstruction, fascial oedema, frontal headache, and epistaxis.
What are examples of larvae that can cause ocular or nasopharyngeal myaisis?
Calliphora, Sarcophaga, and Hypoderma
How can aural myiasis take place?
- Purulent exudates discharged from running ears attract some flies and they lay eggs or larvae there.
- Larvae invade the middle ear, inner ear, or brain tissue in extreme cases.
What are the symptoms of aural myiasis?
C/P: Patient complains of crawling sensation and buzzing noise and sometimes foul-smelling discharge or perforation of the drum occur.
What are examples of larvae that can cause aural myiasis?
Cochliomyia, Wohlfahrtia, Sarcophaga, Lucilia and Chrysomia.
What is myiasis classified into according to the biological habit of the fly?
Specific, Non-specific and accidental
What is specific myiasis?
This is the condition when larvae invade only living tissues (Obligatory tissue parasites)
What are examples of specific myiasis?
- Hypoderma and Dermatobia: the larvae of which, invade the skin causing boil-like swellings
- Wohlfahrtia and Oestrus: invade the eyes, nose, and external ears
What are the sites of specific myiasis and its symptoms at each place?
In the eye, they cause conjunctivitis and corneal ulcers.
In the nose, obstruction and persistent bloody purulent discharge.
In the ears, external otitis.
