Extra Intestinal Nematodes

Extra-Intestinal Nematodes  Trichinellaspiralis
3. Serous Cavity
Filarial Nematodes live in either: Subcutaneous tissues, Lymphatic system,
 Mansonellaperstans
or the serous cavity of the abdomen
 Mansonellaozzardi
 Arthropod-borne worms
 Belong to the superfamily Filaroidea
 Slender thread-like worms Periodicity
 Female worms are viviparous
Nocturnal Periodicity –Largest number of microfilariae occur in the blood
 Microfilariae can either be Sheathed or Unsheathed
during night (Wuchereriabancrofti)
Sheathed Microfilariae Unsheathed Microfilariae
Diurnal Periodicity– Largest number of microfilariae in the blood occur
during the day (Loa loa)

Nonperiodic– Microfilariae circulate at constant levels during the day and
night (Onchocerca volvulus)

Subperiodic– Microfilariae are detected in the blood during the day but are
detected in higher numbers during late afternoon or at night



Filarial Nematodes

 Life cycle is passed in 2 hosts: Definitive Host (man) and Blood-
sucking Arthropods
 Eight species are known to infect man but 6 of them are pathogenic
Classification based on the location on the body  Infection is called Filariasis, traditionally refers to lymphatic filariasis
1. Lymphatic Microfilariae caused by W. bancroftiand Brugia spp.
 Wuchereriabancrofti(Bancroftianfilariasis) Basic Life Cycle
 Brugiamalayi(Brugianfilariasis)
 Brugiatimori  5 larval molts: 3 in the insect vector and 2 in the human reservoir
2. Subcutaneous  Infection begins with the bite of an infected arthropod vector
 Loa loa
 Onchocerca volvulus
 Mansonellastreptocerca
 Parastrongylus 1. Infective L3 larvae are deposited into the skin or blood of the
 Anisakis human via bite of the vector

, 2. Larva attains sexual maturity. During this time parasite undergoes 2 Microfilariae
mold and become adult (L5)
 Colorless, translucent body with a blunt head
3. Adult female worm gives birth to L1 larva. Up to 50,000
microfilariae per day can be produced  Measures 250-300 µm in length and 6-10 µm in thickness
4. Microfilariae are ingested by the arthropod vector; 2 molts occur,  Can move forwards and backgrounds within the sheath
infective L3 larvae develop and capable of infecting the human host  Covered by hyaline sheath
 Do not multiply or undergo further development in the human body
 Life span: 2-3 months
Wuchereriabancrofti(BancroftianFilariasis)

Historical Background

 Ancient Egyptian, Hindu, and Persian physicians (600 BC) – first to
note Elephantiasis
 1863, Demarquay discovered microfilariae in hydrocele fluid
 1868, Wucherer found organisms in chylous urine
 1872, Lewis found microfilariae in blood
 1872, Bancroft found adult worm in a lymphatic abscess

Morphology

Adult worm
 Periodicity: Nocturnal periodic; between 9-10 PM and 2-4 AM
 Minute and thread-like with smooth cuticle and tapering ends  Correlates with night biting habit of the vector
 Creamy-white, long, and filiform in shape  During day time spends mainly in the capillaries of the lung and
Female kidneys or in the heart and great vessels
 Insect Vectors:
 80-100mm x 0.24-0.30mm in diameter o Aedespoicilius
 Posterior end is straight o Anopheles minimusflavirostris
 Viviparous and directly liberates sheathed microfilariae into lymph o Culexquinquifasciatus(poor vector) – rest of Asia

Male Breeding Sites

 40 mm long x 0.1 mm in diameter
 Posterior end is curved and contains 2 spicules of unequal length

Life Span: >10-15 years