Para Lec

• Enterobius vermicularis


  Pinworm (US), Threadworm (UK, Australia and New Zealand), Seatworm

  
• Enterobius vermicularis


  • Worldwide distribution, commonly affects children
• Habitat


  Adult worms are found in the caecum and appendix

  
• Pinworm eggs are easily seen under a microscope
• Lifespan of Enterobius vermicularis adults is about 7–8 weeks

  
• Life cycle of Enterobius vermicularis

  1. Eggs laid by gravid female in perianal region

  2. Embryonated eggs ingested by humans

  3. Eggs hatch in intestine

  4. Adults develop in large intestine (cecum)

  5. Gravid female migrates to perianal region at night to lay eggs

  6. Retroinfection occurs when egg hatches and larva migrates up rectum

  
• Enterobiasis


  • Occurs mostly in children
  • About one-third of infections are asymptomatic
• Trichinella spiralis


  Pork tapeworm
• Trichinella spiralis


  • Infection occurs in pork-eating countries like Europe and America
  • Encysted larvae present in striated muscles of pigs and rats
  • Humans are accidental hosts

  
• Wuchereria bancrofti


  Bancroft filarial worm
• Wuchereria bancrofti


  • Distributed widely in the tropics and subtropics
  • Adult worms reside in the lymphatic system of humans
  • Microfilariae found in blood

  
• Wuchereria bancrofti is one of the three parasites that causes lymphatic filariasis (elephantiasis)
• Vector/intermediate host


  Culex quinquefasciatus mosquito
• Life cycle of Wuchereria bancrofti

  1. Mosquito takes blood meal, ingests microfilariae

  2. Microfilariae shed sheaths, penetrate midgut, migrate to thoracic muscles

  3. Develops into L1 larva

  4. Molts twice, develops into L3 larva

  5. L3 larvae migrate to head and proboscis

  
• Vector or intermediate host of W. bancrofti

  Culex quinquefasciatus
• Pathogenesis and clinical features of W. bancrofti infection

  • Asymptomatic phase with high microfilaremia
  • Inflammatory (acute) phase with fever, lymphatic inflammation, lymphoedema
  • Obstructive (chronic) phase with lymph vessel and node blockage, lymph stasis, lymphoedema, elephantiasis
• Involvement of genitalia and chyluria are characteristics of W. bancrofti infection and not of B. malayi infection
• Elephantiasis affects men mainly in the legs, arms and scrotum, and women in the legs, arms and breasts
• Elephantiasis in B. malayi infection involves the leg below the knee
• Incubation period is about 8–12 months
• Adult filarial worm contains endosymbiotic bacteria, Wolbachia spp. which has a role in the pathogenesis of its infection and is also essential for worm fertility

  
• Wolbachia has become a target for antifilarial chemotherapy
• Pathogenesis and clinical features of tropical pulmonary eosinophilia (TPE)

  • Failure in suppression of immune response to microfilarial antigens, microfilariae filtered out and destroyed in lungs with allergic inflammatory reaction
  • Presents with low-grade fever, loss of weight, pulmonary symptoms like dry nocturnal cough, dyspnea and wheezing
  • Persistent eosinophilia
  • Chest X-ray shows changes similar to miliary tuberculosis
  • Associated with high level of serum IgE and filarial antibodies
  • Microfilariae absent in peripheral blood
  • Responds to treatment with diethylcarbamazine (DEC)
• Diagnosis of lymphatic filariasis


  • Microscopic examination of thick blood film, chylous urine and hydrocele fluid for microfilariae
  • Serodiagnosis using immunochromatographic test (ICT)
  • Molecular diagnosis using PCR
• DEC provocation test


  Patient given single oral dose of 50–100 mg diethylcarbamazine, followed by blood sample 30–45 minutes later to "flush out" microfilariae into peripheral blood during day time
• Treatment of lymphatic filariasis

  • Diethylcarbamazine (DEC) 6 mg/kg/day orally for 1 day or 12 days
  • Ivermectin 400 μg/kg single dose orally
  • Tetracyclines to inhibit endosymbiotic Wolbachia bacteria
  • Elevation, elastic bandage and foot care for elephantiasis
  • Surgery for hydrocele
  • Bed rest, high protein diet and DEC for chyluria
• Prevention and control of lymphatic filariasis

  • Control of vector mosquito
  • Use of mosquito nets and repellents
  • Detection and treatment of cases
• Brugia malayi occurs in India, Indonesia, Philippines, Malaysia, Thailand, Vietnam, China, South Korea and Japan
• Brugia timori is found in Timor, Indonesia
• Habitat of adult filarial worms

  • Lymphatic system of human
  • Blood for microfilariae

  
• Brugia malayi adult worms


  • Generally similar to W. bancrofti but smaller in size

  
• Brugia malayi microfilariae


  • Sheathed, stained with Giemsa, kinky, cephalic space longer (ratio 2:1), overlapping body nucleus with 2 terminal nuclei
• Life cycle of Brugia malayi


  1. Similar to W. bancrofti, but intermediate hosts are Mansonia, Anopheles and Aedes mosquitoes

  2. Nocturnal periodic and nocturnal subperiodic forms

  3. Periodic form transmitted by Mansonia and Anopheline mosquitoes, subperiodic form by Mansonia in forest swamps

  4. Natural animal infections are rare, but cats, dogs and monkeys can serve as reservoirs
• Prevention and control methods for Brugia malayi are similar to W. bancrofti
• Brugia timori is limited to Timor island of Eastern Indonesia
• Vector of B. timori is Anopheles barbirostris, which breeds in rice fields and is a night feeder
• No animal reservoir is known for B. timori
• Brugia timori microfilariae


  • Sheath fails to take Giemsa stain, cephalic space ratio 3:1
• Lesions produced by B. timori are milder than those of bancroftian or B. malayi filariasis
• DEC and albendazole are used in the treatment of Brugia timori filariasis