University:
American Career College
Course:
NURS115 | Intermediate Medical
Academic year:

2021
Views:

101

Pages:

29
Author:

Opfer8fg

2- Enterobius vemicularis 2- Enterobius vemicularis (Oxyur) Enterobiasis or oxyuriasis Pinworm, seatworm or threadworm infection Kermak (Persian) Deedan dabousia (Arabic) Geographic distribution/epidemiology:  Cosmopolitan  Worldwide about 1.5 billion of humans are infected This worm is besides Ascaris lumbricoides one of the most common human parasites Location in host:  The adults are located in the lumen of the caecum and appendix (colon and rectum), sometimes with the anterior end attached to the mucosa  In heavy infections they may also be present in the ascending colon and ileum Biology, morphology:  Pinworms are: 1) Small cylindrical nematodes 2) Pointed at either end 3) They have three lips around the mouth but no buccal capsule 4) The esophagus is muscular and has a posterior bulb 5) They have cephalic alae (cuticle has cervical alae continued as lateral projections, which enable Enterobius to be easily recognized in sections of appendix) Adult worms (Females):  The whitish appearing adult females reach a length of up to 1 cm  Females are characterized by their long but small posterior end, which led to the trivial name “pin worm”  Females leave during night (during the rest of the infected person) the anus and glue their fertilized eggs at the perianal skin  Adult worms (Males):  Males are: 1) 2) 3) 4) 5) 2–5 mm long have no pointed posterior end die rather quickly after copulation with a female seen on the surface of human feces the posterior end is curved ventrally and has a single copulatory spicule Anterior part of E. vermicularis. Note cephalic alae and esophageal bulb .  Eggs (Ova):  50–60 (average 54) μm × 20–30 μm  Have a thin semi-transparent shell  They are ovoid and flattened on one side  They are D like shape (ovoid and flattened on one side)  Eggs are usually laid partially embryonated and contain infective rhabditiform larvae (L2) in 4–7 h at 35°C (they require oxygen for complete development and do not develop below about 22°C). Life cycle  The gravid female migrates out of the anus in the evening or at night and lays numerous sticky eggs on the perianal and perineal skin  The female normally dies after oviposition (burst)  Eggs are usually laid partially embryonated and contain infective rhabditiform larvae (L2) in 4–7 h at 35°C (they require oxygen)  The outer albuminous layer of the egg is very sticky and in sensitized individuals can cause an intense itching, as does the adult female (this often leads to scratching and eggs then lodge under the fingernails)  when L2 containing egg ingested, the larvae hatch in the duodenum (small intestine) and form L3 The L3 lodge in the crypts of the ileum and moult twice The young adults move down to the colon, attach to the mucosa and become mature in 15–43 days Retroinfection:  Retroinfection can occur if the larvae hatch on the perianal skin and migrate back up the anus 1) Site of inhabitation: cecum and colon 2) Infective stage: embryonated egg (L2 egg) 3) Infective route: by mouth (Oral) 4) Without intermediate host and reservoir host 5) Life span of female adults: 1-2 months Symptoms of the disease (Enterobiasis)  About one-third of pinworm-infected persons are asymptomatic  Major symptom is anal pruritus (itching around the anus):  In most of the cases, nightly itching around the anus occurs, which leads to sleeplessness (insomnia) and restlessness  In the case of female patients, also infections of the urogenital system had been reported, which were detected by occurrence of intense itching  Only in very rare cases, direct symptoms of disease occurred such as abdominal pain, diarrhoea, cramps, etc Adult Pinworms on the perianal skin Diagnosis:  Patients claiming the above cited itching symptoms should be asked to visit the physician without cleaning the anal region  Egg in stool examination:  Diagnosis depends on recovery of the characteristic eggs. The eggs and the female adults can be removed from the folds of the skin in the perianal regions by the use of the cellophane tape method  The examination should be made in the morning, before the patient has washed or defecated Pathway of infection: Oral by uptake of eggs containing larvae (L2)  This may occur by self-infections (hand-mouth) or when touching egg-contaminated toilets or door grips Prophylaxis (Prevention and control): In cases of enterobiasis in a family or in a kindergarten, intense handwashing and hot water cleaning of toilets should be done Medication of the whole family is needed as well as hot washing of the underwear of treated persons Treatment: Single dosages of mebendazole (100 mg) Single dosages of albendazole (200–400 mg (children below 2 years: 15 mg/kg bodyweight)  Albendazole is the drug of choice. Repeated retreatment may be necessary for a radical cure Other anthelmintics like: pyrvinium or pyrantel are effective