Lymphatic Filariasis Quiz

Tissue & Body Fluid Nematode

• Helminths are multicellular parasites.
• Helminths are divided into Nemathelminths (roundworms), Platyhelminths (flatworms).
• Class Nematoda includes roundworms.
• Class Trematoda includes flukes.
• Class Cestoda includes tapeworms.

Helminthology

• Helminths (worms) are multicellular parasites.
• They are divided into: Nemathelminths (round worms), Platyhelminths (flat worms).
  • Class Nematoda: roundworms
    • Intestinal nematodes (large intestine, small intestine)
    • Tissue nematodes (Filarial worms)
  • Class Trematoda (flukes):
    • Blood trematodes
    • Hepatic trematodes
    • Intestinal trematodes
    • Lung trematodes
  • Class Cestoda (tapeworms):
    • Intestinal cestodes
    • Somatic/tissue cestodes

Differences between Cestodes, Trematodes, and Nematodes

• Cestodes (Tapeworms):
  • Shape: Tape-like and segmented
  • Head end: Suckers present; some have hooklets
  • Alimentary canal: Absent
  • Body cavity: Absent
  • Sexes: Monoecious (except some species)
  • Life cycle: Requires two hosts (except some species)
  • Larva forms: Cysticercus, hydatid cyst, coenurus, cysticercoid, coracidium, plerocercoid, and procercoid
• Trematodes (Flukes):
  • Shape: Leaf-like and unsegmented
  • Head end: Suckers present; no hooklets
  • Alimentary canal: Present but incomplete
  • Body cavity: Absent
  • Sexes: Monoecious (except schistosomes)
  • Life cycle: Requires three hosts (except schistosomes)
  • Larva forms: Cercaria, metacercaria, redia, miracidium, and sporocyst
• Nematodes (Roundworms):
  • Shape: Elongated, cylindrical, and unsegmented
  • Head end: No sucker, no hooklets; some have well-developed buccal capsules.
  • Alimentary canal: Complete from mouth to anus
  • Body cavity: Present
  • Sexes: Diecious (except filarial worms and Dracunculus)
  • Life cycle: Requires one host (except filarial worms and Dracunculus)
  • Larva forms: Rhabditiform larva, filariform larva, and microfilaria.

Filarial

• Infection by filarial worms belonging to superfamily Filarioidea.
• Classified according to adult worm body location.
  • Lymphatic filariasis
  • Subcutaneous filariasis
  • Serous cavity filariasis
• Types: Wuchereria bancrofti, Brugia malayi, Brugia timori

Lymphatic Filariasis

• Also known as elephantiasis.
• Painful, disfiguring swelling of the legs and genital organs (classic late-stage sign).
• Caused by filarial worms.
• Transmitted by mosquitoes carrying filarial worm infective larvae.
  • Vectors: mosquito
  • Species depends on geographical area.
• Common in developing countries.
• Three species of human filarial worms are found.
• In Malaysia only B. malayi & W. bancrofti are found.
• Endemic in 8 Malaysian states.
• Prevalent in tropical and sub-tropical areas with many mosquito vectors.
• Incidence in Malaysia decreasing due to effective control programs.

Morphology-Wuchereria bancrofti

• Adult worms: whitish, thread-like, smooth cuticle, tapering ends; female (4–10 cm) larger than male (2–4 cm); lifespan 10–15 years.
  • Found in lymphatic vessels and lymph nodes.
• Embryos (microfilariae Mf): 250–300 µm length; colorless, transparent; blunt heads and pointed tails; covered by hyaline sheath; active movement; discrete, countable body nuclei; no terminal nuclei; short cephalic ratio (1:1); present in peripheral blood.
  • Nocturnal periodicity (between 22:00 and 02:00); not in blood during day time.
• Microfilariae do not multiply in human body; they die if not taken by a female mosquito.

Morphology-Brugia malayi

• Adult worms are similar to W. bancrofti but smaller in size (53mm female, 24mm male).
• Microfilariae: tail has two distinct terminal nuclei (subterminal & terminal); released into bloodstream; kinky, cephalic space is longer (ratio is 2:1)
• Sheath is stained, overlapping body nuclei.

Morphology-Brugia timori

• Endemic in Timor Island, Indonesia.
• Microfilariae larger than those of B. malayi; sheath does not stain with Giemsa stain; 5–8 nuclei present in tail.
• Lesions are milder.

Morphology-Loa-loa

• Loa-loa is also known as African eyeworm.
• Causes loiasis (fugitive swellings).
• Vectors: Day-biting flies, Chrysops.
• Microfilariae is sheathed, and nuclei extend up to tail tip.
• Microfilariae appears during the day (diurnal periodic).

Morphology-Onchocerca volvulus

• Produces onchocerciasis ("river blindness").
• Adult worm is white, with transverse striations on cuticle, curved posterior end.
• Microfilariae is unsheathed, tail-tip free of nuclei, nonperiodic.
• Definitive host: Humans.
• Intermediate host: Female black flies (Simulium).

Morphology-Mansonella streptocerca

• Seen only in West Africa.
• Adult worms live in the dermis, just under the skin surface; unsheathed microfilariae found in skin.
• Vectors: Culicoides species.
• Reservoir hosts: Chimpanzees.
• Infection: dermatitis with pruritus and hypopigmented macules.
• Diagnosis: microfilariae in skin clippings.
• Treatment: Ivermectin.

Morphology-Mansonella ozzardi

• New World filaria, seen in Central and South America and the West Indies.
• Adult worms in peritoneal and pleural cavities of humans.
• Nonperiodic, unsheathed microfilariae in blood.
• Vectors: Culicoides species.
• Infection is asymptomatic, except for possible transient abdominal pain, rashes, angioedema, and malaise.

Morphology-Mansonella perstans

• Extensively distributed in tropical Africa and coastal South America, adult worms in body cavities (mainly peritoneum and often in the pleura).
• Unsheathed and subperiodic microfilaria.
• Vectors: Culicoides species; reservoir hosts are African primates
• Infection generally asymptomatic, possible transient abdominal pain, rashes, angioedema, and malaise.
• Diagnosis: microfilaria detected in the peripheral blood or serosal effusions; Treatment: Doxycycline.

Life Cycle- filarial worms

• Infective larvae enter the human skin through mosquito bites.
• Develop into adult worms in the lymphatic system.
• Adult female worms produce sheathed microfilariae that migrate into lymphatic and blood channels.
• When the vector mosquito takes a blood meal, it ingests the microfilariae.
• Microfilariae shed sheaths, penetrate the mosquito's midgut and migrate to thoracic muscles.
• Develop into L1 larva.
• Molts twice and develops into L3 larva.
• L3 larvae migrate to heads and proboscis, infecting another human when the mosquito takes a blood meal.

Treatment

• Medication: DEC and Albendazole (in combination)
• Surgical for hydrocele (rarely successful), elephantine legs: elevation, elastic bandages, foot care.
• Special boots or elastic bandages to reduce enlarged limb size
• Medical management of chyluria: bed rest, high protein diet, and treatment with DEC.

Prevention & Control

• National Lymphatic Filariasis Elimination Program (Malaysia): mass drug administration (annual, 5 cycles) in endemic areas; health education (community knowledge, healthy lifestyle, personal hygiene).
• Blood screening and probe study to identify new endemic areas, chemotherapy in endemic areas.
• Vector control: spraying, treated nets for periodic infections, adding larvae-eating fish to ponds.
• Proper clothing, use of repellents to avoid contact with vectors

Laboratory Diagnosis

• Microscopic examination of blood smears (thick and thin, Giemsa or H&E); blood collection at night (10 pm–2 am) for microfilaria detection.
• Concentration techniques (centrifugation, filtration through Nucleopore membrane).
• Detection of adult worms in lymph node biopsies.
• Serological tests (ELISA, immunochromatographic test [ICT]).
• Molecular diagnosis (PCR) to detect filarial DNA in blood.
• Chylous urine (milky appearance), as well as hydrocele fluid.

Clinical Manifestations of Classical Filariasis

• Asymptomatic: microfilariae present in blood in endemic areas; no clinical signs.
• Acute (inflammatory): fever, malaise, headache, chills, lymphadenitis, lymphangitis, lymphoedema.
• Chronic (obstructive): 10-15 years, hydrocele (swelling of scrotum, fluid accumulation in testes), lymphedema (swelling of upper and lower extremities), elephantiasis (enlargement and thickening of lower and/or upper extremities, scrotum, breasts), Lymphangiovarix (lymph vessel dilation), chyluria (lymph in urine).

Pathogenesis

• Depends on the host's immune system and inflammatory responses.
• Infection of W. bancrofti-Wuchereriasis or bancroftian filariasis.
• Brugia malayi causes brugian/malayan filariasis, similar to bancroftian filariasis, but there is no chyluria and no involvement of male genitalia; usually restricted to the legs.

Pathogenesis of Occult Filariasis

• Also known as Meyers Kouwenaar syndrome, it's a hypersensitivity reaction to microfilarial antigens, not due to lymphatic involvement.
• Microfilariae are not found in blood (destroyed by allergic inflammation in tissues).
• Features: massive eosinophilia, hepatosplenomegaly, pulmonary symptoms (dry cough, dyspnea, wheezing).
• Occurs as a result of hypersensitivity to microfilarial antigens.
• Also include arthritis, glomerulonephritis, thrombophlebitis, and tenosynovitis.
• Absence of classical lymphatic filariasis features.
• Common in tropical pulmonary eosinophilia with low-grade fever, weight loss, dry nocturnal cough, dyspnea, asthmatic wheezing, marked increase in eosinophils (>3000 µm, up to 50,000 or more).
• Chest X-ray shows mottled shadows, similar to miliary tuberculosis, elevated serum IgE (>1000 IU/mL), filarial antibodies.

Questions

• Listed topics include discussing lymphatic filariasis, endemic lymphatic filariasis in Malaysia (types and vectors, periodicity, pathogenesis, and clinical manifestations) and discussing lymphatic filariasis (diagnosis, and prevention)

Test your knowledge on lymphatic filariasis, focusing on its causative agents Wuchereria bancrofti and Brugia timori. Understand the vectors, lifecycles, and distinctions between male and female worms. This quiz is designed for students and professionals in parasitology and infectious diseases.