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2025 SEM 2 CLINICAL PARASITOLGY (LEC) > filarial worms > Flashcards

filarial worms Flashcards

1
Q

Phylum:
Class:

A

Phylum: nemathelminthes
Class: nematoda
*they are blood and tissue species

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2
Q

Habitat

A

Reside in the
- subcutaneous tissues
- lymphatic system
- serous cavities of humans

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3
Q

Reproduction

A

Female worms are ovoviviparous
- releasing larvae known as microfilariae

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4
Q

Detection

A

Microfilariae can be found in the peripheral blood or cutaneous tissues depending on the species

  • Microfilariae – diagnostic stage for filariasis
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5
Q

Periodicity

A

Microfilariae in the peripheral blood may exhibit
- nocturnal periodicity
- diurnal periodicity
- no periodicity at all (sub-periodic)

*The basis of periodicity is unknown but may be linked to the biting habits of the vector.

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6
Q

What are the 2 hosts required in the life cycle

A

Definitive host → Humans
Intermediate host → Blood-sucking arthropods

*Microfilariae develops into infective larvae (L3) inside the arthropod host

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7
Q

Survival of the adult worm and microfilariae

A

Adult worms: live for many years in the human body
- organs increases in size
Microfilariae: survive only for a few months

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8
Q

Morphology of the two forms

A

Adult worms:
Creamy white, threadlike appearance
Males is 20-500mm
Female have the size
*produces microfilariae found in the blood

Microfilariae:
Slender, 150-350 um in length
Key identifying features
- nuclear distribution in the tail tip
- presence or absence of a sheath

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9
Q

Life cycle

A
  1. Infection starts when infective larvae enter the human body via an arthropod bite.
  2. Larvae migrate to tissues and mature into adults within a year.
  3. Adult worms reside in the lymphatics, subcutaneous tissue, or body cavities.
    - the ones that mature, reproduce and release microfilariae
  4. Female worms give birth to live microfilariae found in blood or dermis.
  5. Transmission occurs when an arthropod ingests microfilariae during a blood meal.
    - microfilariae: diagnostic and infective stage to the vector
  6. Arthropod (intermediate host) supports larval development into the infective stage.
  7. Once mature, the infective larvae are transferred to another human, restarting the cycle.
    Species Variation:
    - adult worm location
    - microfilariae presence
    - vector type vary by specie
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10
Q

Types of periodicity

A
  • Nocturnal – Parasites appear at night.
  • Diurnal – Parasites appear during the day.
  • Subperiodic – No clear-cut timing.

*Appear in the bloodstream at specific times
*Linked to the feeding behavior of the parasites’ vector

!!helps determine the optimal time for specimen collection!!

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11
Q

What’s the significance of periodicity

A

Helps determine the optimal time for specimen collection

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12
Q

What are the diagnostic methods for filariasis

A
  1. Microscopic examination (Pri method)
    Detects microfilariae in
    - giemsa-staine blood smear
    - tissue scraping from infected nodules
    - whole blood samples

Knot technique:
used to concentrate n detect microfilariae by lysing blood cells

  1. Serological tests
    have specific concerns
    not universally considered reliable for diagnosis
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13
Q

A mode of reproduction in which embryos develop inside eggs that remain within the mother’s body until they hatch.

A

Ovoviviparous
- no direct maternal nourishment is provided
-example: W. bancrofti and B. malayi
■ Produce microfilariae (embryonated larvae)
■ Released into the bloodstream rather than laid as eggs

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14
Q

The characteristic of occurring at regular intervals or cycles.

A

periodicity
- present int he peripheral blood that usually fluctuates or increases during specific time of the day

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15
Q

why does periodicity peak at certain times

A

It aligns with the feeding behavior of the mosquito vector
= maximizing transmission.

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16
Q

A protective covering or enclosing structure around an organ, tissue, or other biological component.

A

Sheath
- helps in species identification and blood smear (can also be a diagnostic method)

  • example: W. bancrofti and B. malayi = sheathed
    ■ Retain the egg membrane as a protective covering

[develops inside an egg.
when it hatches, instead of completely leaving the egg behind, it keeps part of the egg membrane around it—sheath.
it stays around the parasite as a thin protective layer but does not contain or hold any eggs.]

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17
Q

Openly displayed or clearly apparent, not hidden or secret.

A

Overt
[easy to see and not hidden]

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18
Q

What are the overt symptoms of lymphatic filariasis?

A

Lymphedema
Elephantiasis
Hydrocele

  • Infections can be asymptomatic for years before manifesting overt symptoms
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19
Q

A bacterium that lives within the cells of a host organism in a mutually beneficial (symbiotic) relationship.

A

Endosymbiotic bacterium
- example: Wolbachia spp.
■ Essential for worm survival and reproduction

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20
Q

Infective stage for humans →
Infective stage for mosquitoes →

A

Infective stage for humans → L3 larvae
Infective stage for mosquitoes → Microfilariae (picked up from an infected person’s blood)

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21
Q

Early and immature larval stage

A

Microfilariae

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22
Q

what are the key identifying features

A

Nuclear distribution in the tail tip
Presence or absence of a sheath

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23
Q

common name
1. WUCHERERIA BANCROFTI
2. BRUGIA MALAYI
3. LOA LOA
4. ONCHOCERCA VOLVULUS
5. MANSONELLA OZZARDI
6. MANSONELLA PERSTANS

A
  1. Bancroft’s filaria
  2. Malayan filaria
  3. African eye worm
  4. Blinding filaria
  5. New World Filaria
  6. Perstans Filaria
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24
Q

how is the nuclei distributes in the Wuchereia bancrofti

A

Free from nuclei at the end of the tail

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25
distribution in 1. WUCHERERIA BANCROFTI 2. BRUGIA MALAYI 3. LOA LOA 4. ONCHOCERCA VOLVULUS 5. MANSONELLA OZZARDI 6. MANSONELLA PERSTANS
1. in tropical and subtropical regions. 2. endemic to Southeast Asia, including India, Indonesia, the Philippines, Malaysia, Thailand, Vietnam, China, South Korea, and Japan. (smaller geographic range compares to W. bancrofti) 3. limited to West and Central Africa, where its vector, Chrysops (mango fly – rainforest), is endemic. 4. primarily found in tropical Africa, Central America, and South America. - small focus of infection exists in Yemen and South Arabia. - East Africa, Zaire, Angola, parts of Mexico, Colombia, Brazil, and portions of Venezuela. 5. Western hemisphere (North America, Central and South America, West Indies, Caribbean) 6. Africa, Caribbean, Panama, Northern South America
26
habitat - adult worms - microfilariae 1. WUCHERERIA BANCROFTI 2. BRUGIA MALAYI 3. LOA LOA 4. ONCHOCERCA VOLVULUS 5. MANSONELLA OZZARDI 6. MANSONELLA PERSTANS
1. & 2. Adult worms: Lymphatic system. Microfilariae: Blood circulation. 3. Adult worms: Subcutaneous tissues and eyes. Microfilariae: Bloodstream 4. Adult worms: Subcutaneous or fibrous nodules within CT Microfilariae: Skin and subcutaneous lymphatics - often near adult worms 5. Adult worms: Body cavities, visceral fat, mesenteries (exact location unclear) Microfilariae: Blood, capillaries, intravascular spaces of skin 6. Adult worms: Peritoneal and pleural cavities mesentery Microfilariae: Blood, no known preference for tissue migration
27
periodicity & survival 1. WUCHERERIA BANCROFTI 2. BRUGIA MALAYI 3. LOA LOA 4. ONCHOCERCA VOLVULUS 5. MANSONELLA OZZARDI 6. MANSONELLA PERSTANS
1. Nocturnal periodicity: - 10 PM - 2 AM - Matches night-biting habits of mosquitoes. - Do not develop further in humans. If not taken up by mosquitoes, they die in 2-3 months. 2. Nocturnal periodicity: 10 PM - 2 AM Subperiodic activity: (Noon - 8 PM), whereas W. bancrofti is strictly nocturnal. *malayi has an animal reservoir, making it harder to eliminate, while W. bancrofti affects only humans. 3. Diurnal periodicit: 12 noon - 2 PM 4. not stated 5. & 6. Non-periodic (can be detected any time in blood)
28
Vector (Intermediate Host)
1. Culex quinquefasciatus (pri vector) Aedes spp. Anopheles spp. 2. Mansonia Anopheles Aedes 3. Chrysops (mango fly – rainforest), 4. Simulium black fly - which breeds in fast-flowing rivers and streams 5. Culicoides midges Simulium blackflies *depending on the loc 6. Culicoides midges
29
W. bancrofti morphology - size - sheath - cephalic (anterior) end - tail (posterior) end - body structure - distinguishing feature
transes
30
What is the key contrast between W. bancrofti and B. malayi?
Wuchereria bancrofti has a 1:1 cephalic space ratio and lacks terminal nuclei in the tail, while Brugia malayi does not.
31
life cycle of W. bancrofti
transes * B. malayi is similar but has diff mosquito vectors
32
what are the pathogenesis of
lymphatic filariasis ASYMPTOMATIC PHASE: high levels of microfilariae in the blood = high microfilaremia common in endemic regions—many patients do not show symptoms due to immune tolerance. *individuals may develop immune tolerance, preventing acute manifestation INFLAMMATORY (ACUTE) PHASE: immune system reacts to antigens released by adult worms, leading to inflammation. Symptoms: - High fever - Lymphangitis – Inflammation of lymph vessels - Lymphadenitis – Swollen lymph nodes - Lymphedema – Swelling due to fluid buildup (fluid retention due to lymphatic blockage) Additional complications in males: - Orchitis – inflammation of testes - Epididymitis – Inflammation of the epididymis (Symptoms last 5-7 days and subside as the immune response stabilizes.) OBSTRUCTIVE (CHRONIC) PHAS: long-term blockage of lymphatic vessels by adult worms = chronic inflammationand immune cell infiltration Cells involved: (invade the affected lymph nodes) - macrophages - eosinophils - lymphocytes - plasma cells Results in: - Thickening & fibrosis of lymph vessels wall → Lymph stasis - Granuloma formation → Scarring & calcification - Lymphatic valve damage → more severe lymph scasis - Pitting edema (early stage) → Swelling that leaves a dent when pressed - Non-pitting edema (later stage due to fibrosis) → Elephantiasis (increased permeability of lymphatic vessels. leakage of protein-rich fluid into the tissues)
33
Elephantiasis Developmentin W. bancrofti
Hard, non-pitting edema (irreversible swelling) - due to fibroblast infiltration and tissue fibrosis. Commonly affected areas: - Genitals, limbs, breasts - Chyluria – Lymph in urine due to lymphatic rupture - Lymph varices – Lymph vessel dilation - Hydrocele – Fluid buildup in the scrotum
34
Role of Wolbachia Bacteria in Pathogenesis
An endosymbiotic bacterium lives inside Wuchereria bancrofti worms. - Essential for worm survival & fertility. - Exacerbates host immune responses, increasing inflammation -It is a target for antifilarial chemotherapy (antibiotics against Wolbachia can weaken the worms) - Doxycycline - Diethylcarbamazine (DEC)
35
Tropical Pulmonary Eosinophilia (TPE)
A hypersensitivity reaction caused by an excessive immune response to microfilarial antigens in the lungs (not a direct parasite effect). Symptoms: - Dry nocturnal cough, wheezing, dyspnea (shortness of breath) - Low-grade fever, weight loss - Persistent eosinophilia (high eosinophil count in blood) - Elevated IgE levels & strongly positive serology for filarial antibodies Key contrast: - Unlike lymphatic filariasis, TPE mainly affects the lungs and is caused by an hypersensitivity reaction rather than direct parasitic effect. *Responds well to DEC treatment.
36
Affected Body Parts by Gender of Lymphatic Filariasis
Men: Legs, arms, scrotum (hydrocele, lymph scrotum). Women: Legs, arms, breasts.
37
briefly explain the Miliary TB-like change in the lungs
lungs develop small, scattered spots that look like tuberculosis (TB) on X-rays. microfilariae absent in blood *responds well to DEC treatment
38
diagnosis for W. bancrofti
1. microscopic examination giemsa-stained blood smear, best collected at night (9pm-4am) due to nocturnal periodicity 2. knott technique lysis of RBC to concentrate microfilariae 3. nucleopore filtration bloof ilteres through a membrane, stained and examined 4. serologic tests antigens/ antibody detection, PCR assays (variable sensitivity) 5. TDE diagnosis no microfilariae in blood high IgE positive serology X-ray changes like miliary TB
39
W. bancrofti - treatment - prevention and control
TREATMNET Diethylcarbamazine (DEC) - drug of choice - 6mg/kg/day orally either 1 day or 12 days. One day treatment is generally as effective as the 12-day regimen Ivermectin - 400 ug/kg single dose orally Tetracyclines - effect in the treatment of filariasis by inhibiting endosymbiotic bacteria (Wolbachia species). PREVENTION AND CONTROL ○ Control of the vector mosquito (anti-larval, anti-adult) ○ Use mosquito net and mosquito repellants ○ Detection and treatment of cases
40
morphology of B. malayi
transes
41
Which mosquitoes transmit the nocturnal periodic form and nocturnal subperiodic form of B. malayi?
nocturnal periodic form: Mansonia and Anopheles (found in swamps & rice fields) nocturnal subperiodic form: Mansonia (found in forest swamps).
42
What animals can be reservoirs for B. malayi?
Cats, dogs, and monkeys - can carry the parasite and help in transmission.
43
briefly explain the pathogenesis of B. malayi
Asymptomatic Phase: - high microfilaraemia - no symptoms in endemic areas Acute (Inflammatory) Phase: - fever - lymphangitis - lymphadenitis, - lymphedema Chronic (Obstructive) Phase: - lymphatic obstruction - fibrosis, granuloma formation Elephantiasis Location: - legs (below knee) - rarely affects genitals Lymphatic Complications: - mild hydrocele - rare chyluria
44
briefly explain Brugia timori - found - vector - animal reservoir - cephalic space ratio - treatment
found: limited to Timor, Indonesia. vector: Anopheles barbirostris (breeds in rice fields, nocturnal feeder). animal reservoir: no known, striclty human transmission Microfilariae have a 3:1 cephalic space ratio (longer than B. malayi). treatment: Diethylcarbamazine (DEC) + Albendazole. *lesions are milder compared to B. malayi and W. bancrofti.
45
Wuchereia vs Brugia - terminal nuclei - periodicity - sheath - size - elephantiasis - zoonotic reservoir - vectors
★ Terminal nuclei ○ W: none ○ B: present two distinct nuclei ★ Periodicity ○ W: nocturnal ○ B: nocturnal and sub-periodic ★ Sheath ○ W: present ○ B: present ★ Size ○ B. malayi is smaller than W. bancrofti ★ Elephantiasis ○ W: affects genitals ○ B: affects lower legs only ★ Zoonotic reservoir ○ W: no zoonotic reservoir ○ B: there is zoonotic reservoir ★ Vectors ○ W: Culex, Aedes, Anopheles ○ B: Mansonia, Aedes, Anopheles
46
morphology of loa loa
transes
47
life cycle of loa loa
transes
48
Disease of Loa loa, does not cause elephantiasis
Loiasis key symptoms and manifestation: 1. Calabar Swellings (Fugitive Swellings) - Transient subcutaneous swellings, up to 3 cm in size, appearing on extremities - Swellings disappear and reappear elsewhere due to adult worm migration 2. Ocular Manifestations - Worm migration through the subconjunctival tissue can cause visible movement of the worm across the eye. - Can result in eye irritation, redness, and foreign body sensation - Rarely causes permanent vision loss but can be distressing to patients - Localized inflammation and itching around migration sites - Mild fever, eosinophilia, and generalized pruritus (itching).
49
lab diaggnosis of loa loa
1. microscopic examination giemsa-stained blood smear - best collected during midday12-2pm due to diurnal periodicity 2. knott technique - blood lysis technique to concentrate microfilariae 3. serologic tests - antibody detection (useful in cases with low microfilaremia) 4. ophthalmic examination - direct visualization of worms migrating across the eye *used for confirming cases where the worm is seen 5. PCR - molecular detection of Loa loa DNA in blood samples
50
morphology of Onchocerca volvulus
transes
51
life cycle of Onchocerca volvulus
transes
52
Why is Onchocerciasis called "River Blindness"?
prevalent along riverbanks, where blackflies (Simulium spp.) breed and transmit the parasite. *in fast-flowing rivers
53
Leading cause of infectious blindness worldwide
Onchocerciasis
54
Symptoms of Onchocerciasis
Develop localized symptoms from subcutaneous nodules Suffer severe allergic reactions to microfilariae presence in the skin Scratching due to itching leads to sec bacterial infections When microfilariae reach the eye, the body's immune response leads to: - Chronic inflammation and lesions. - Progressive corneal scarring, uveitis, optic nerve damage. - Blindness, a significant complication in infected adults. *Symptoms of skin changes and nodule locations vary between the Eastern and Western Hemisphere
55
Fibrous nodules containing adult worms form under the skin and connective tissue.
Onchocercomas (Subcutaneous Nodules) - nodules are painless but may cause chronic inflammation and disfigurement
56
Severe itching (pruritus) due to microfilariae migration in the skin.
Skin Manifestations (Onchodermatitis) - skin thickening and loss of elasticity (commonly referred to as “lizard skin” or “sowda” in severe cases - Depigmentation ("leopard skin") in chronic cases, often seen on shins and lower extremities.
57
Lab diagnosis of Onchocerca volvulus
1. Skin snip biopsy Gold standard - a small skin sample is taken, incubated in saline and examined for emerging microfilariae 2. Sit-lamp examination Identified microfilariae in the cornea and anterior eye chambers 3. PCR Highly sensitive for detecting O. Volvulus DNA in skin samples 4. Serologic tests Antibody tests are available but may cross-react with other filaria, infections 5. Mazzotti test Ivermectin challenge test - causes a severe itching reaction if O. volvulus microfilariae are present
58
Causative agents of serous cavity filariasis
Mansonells ozzardi Mansonella perstans
59
Morphology of Mansonella ozzardi and Mansonella perstans
transes
60
Mansonella ozzardi and Mansonella perstans - general pathogenicity - skin symptoms - systematic symptoms - severe complication
O: asymptomatic but some mild cases reported P: mostly asymptomatic but can cause mild discomfort O: mild urticaria, skin itching P: calabar-like swelling , edema, skin irritation O: lymphadenitis, arthralgia, eosinophilia P: headache, lymphatic, discomfort, joint pain, liver enlargement O: none P: mild liver enlargement, joint and bone pain
61
Primary diagnostic of Mansonella ozzardi and Mansonella perstans
Microscopic identification of microfilariae in blood

2025 SEM 2 CLINICAL PARASITOLGY (LEC) (6 decks)

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