filariae

Question 1

filariae
phylum:
class:

pathogenic vs non-pathogenic filariae

Answer 1

phylum: nemathelminthes
class: nematoda

pathogenic:
Wuchereia bancrofti
Brugia malayi
Loa loa
Onchocerca volvulus

non-pathogenic:
Mansonella ozzardi
Mansonella perstans

Question 1

true or false:
The basic life cycle is the same for all members of the filariae.

Answer 1

true
[No matter the species, all filarial worms follow the same basic life cycle inside the human body.
The larvae grow, become adult worms, and start producing more microfilariae (baby worms).
These microfilariae circulate in the blood and can be picked up by another mosquito, spreading the infection.]

Question 1

briefly explain the 2 morphological forms

Answer 1

ADULT WORMS
creamy white and threadlike appearance
males: 20-500 mm in length
females: twice in size length of the adult males

LARVAE (AKA MICROFILARIAE)
slender and size range under 150-350um in length

Question 1

How does a person get infected with filarial worms?

Answer 1

an infected arthropod insect bites a person and injects 1 to 4 infective larvae at the feeding site
(it initiates the human infection)

Question 2

what are the 2 key characteristics helpful in speciating the microfilariae forms

Answer 2

distribution of nuclei
presence or absence of a delicate transparent covering (aka sheath)

Question 3

briefly explain the life cycle of a filariae

Answer 3

1. larvae migrate to the tissue for their development
   [After entering through a mosquito bite, the larvae move to tissues to grow]
2. resulting adult worms reside in the lymphatics, subcutaneous tissue or intestinal body cavities (peritoneal cavity etc)
3. fertilized adult female worms lay live microfilariae = take up residence in blood or dermis
   [adult female worms produce tiny baby worms (microfilariae) that spread into the blood or skin = sexual reproduction]
4. microfilariae exit the body via blood meal by appropriate arthropod vector (intermediate host: arthropod vector)
   * blood meal: when the vector bites us using blood meal from the human host
   [ a mosquito bites an infected person, it sucks up the microfilariae from the blood.
   Mosquito = Intermediate Host (It helps the parasite grow but doesn’t get sick).]
5. larvae development into infective stage takes place in the insect host
   [Inside the mosquito, the baby worms develop into the infective stage.]
6. parasite is transferred into uninfected humans
   [infected mosquito bites another person, it injects the larvae, starting the cycle again.]

Question 4

Definitive Host vs. Intermediate Host

Answer 4

Definitive Host = The parasite’s final home:
This is where the parasite grows into an adult and reproduces.
Example: Humans are the definitive host for filarial worms because the worms become adults and reproduce inside the body.

Intermediate Host = The parasite’s temporary home
This is where the parasite develops but does NOT fully mature or reproduce.
Example: Mosquitoes are the intermediate host for filarial worms because the baby worms (microfilariae) grow into the infective stage inside the mosquito, but they don’t become adults.

Key Difference:
Definitive Host = Parasite reaches adulthood and reproduces.
Intermediate Host = Parasite grows but does NOT mature into an adult

Question 5

A phenomenon whereby the parasites are present in the bloodstream during a specific time.

Answer 5

periodicity
*present in the bloodstream

[they are smart - It’s like catching a bus at the right time where parasites “wait” for the mosquito to come so they can continue their life cycle!]

Question 6

what are the 3 types of periodicity

Answer 6

1. Nocturnal - occurring at night
2. Diurnal - occurring during the day
3. Subperiodic - the timing of occurrences is not clear-cut

Question 7

the primary method of diagnosis for filariae

Answer 7

1. Microscopic examination of the
   microfilariae in Giemsa-stained blood
2. A tissue scraping of an infected nodule

*whole blood samples may also be collected

Question 8

what are the other blood test

Answer 8

SOC: whole blood

1. knott technique
2. membrane filtration

*Knott technique and Membrane filtration is used for low microfilaremia (low microfilariae in blood.)

3. serologic test
   - have been develop and available
   -however, concern as to their specificity and thus considered as viable diagnostic techniques

Question 9

why is serologic test are not always reliable

Answer 9

as they might give false results
- these tests checks for immune system reactions to the parasite

Question 10

how to perform knott technique

Answer 10

1. 1 mL of blood can be mixed with 140 mL of 2% formalin and then centrifuged.
2. The supernatant is discarded and the sediment is studied.
   [after centrifugation, sediment sa bottom of test tube]
3. Spread like a thin blood film, fixed and stained.
   [can view under the microscope]

Question 11

how to perform membrane filtration

Answer 11

makes use of syringe attached to a Swinney filter holder

1. 1 mL of fresh or anticoagulated blood is drawn up into the syringe and lyzed by adding 10 mL of distilled water.
   ○ Anticoagulant blood - no
   coagulant.
   ○ Lyzed - rupture the RBC.
2. Lyzed blood is then passed through the Swinney membrane filter where microfilariae will be recovered.
3. A membrane filter can be examined like a wet smear preparation or may be dried, fixed, and then stained.
   ○ Afterwards, view under the
   microscope.

Question 12

this blood test makes use of syringe attached to a Swinney filter holder

Answer 12

membrane filtration

Question 13

common name and common associated disease/ condition names for each filariae
- Wuchereria bancrofti
- Brugia malayi
- Loa loa
- Onchocerca volvulus
- Mansonella ozzardi
- Mansonella perstans

Answer 13

common name:
- Bancroft’s Filaria
- Malayan Filaria
- Eye worm (African)
- Blinding filaria
- New World filaria
- Perstans filaria

common associated disease/ condition names:
- Bancroft’s filariasis or Elephantiasis
- Malayan filariasis or Elephantiasis
- Loiasis
- River blindness, Onchocerciasis
- None (Nonpathogenic)
- None (Nonpathogenic)

Question 14

morphology of microfilariae and adult worm of Wuchereria bancrofti

Answer 14

● Microfilariae
○ 240 to 300 um long
○ Sheath is present (Thin and delicate)
○ Numerous nuclei in the body
○ Anterior end is blunt and round
○ Posterior end or tail end is free of nuclei

● Adult Worm
○ White and thread like appearance
○ Females: 40 - 100 mm
○ Males: 20 - 40 mm

Question 15

morphology of microfilariae and adult worm of Brugia malayi

Answer 15

Morphology
● Microfilariae → little bit shorter than W. bancrofti
○ 200 to 280 um long
○ Sheath is present
○ Rounded and anterior end
○ Numerous nuclei in the body
○ Presence of two distinct nuclei
in the tip of a somewhat pointed tail

● Adult worms
○ Resemble those of W. bancrofti
○ White and threadlike appearance
○ Females: 53 mm in length
○ Males: 24 mm in length

Question 16

morphology of microfilariae and adult worm of Loa loa

Answer 16

Morphology
● Microfilariae
○ 248 to 300 um long|
○ Sheath is present
○ Nuclei fill the organism
○ Nuclei at the tip of the pointed tail are arranged in continuous rows.

● Adult worm
○ White and cylindrical threadlike appearance
○ Females: 38 - 72 mm in length
○ Males: 28 - 35 mm in length

Question 17

morphology of microfilariae and adult worm of Onchocerca volvulus

Answer 17

● Microfilariae
○ 150 to 355 um long
○ Sheath is absent
○ Body contains numerous nuclei that extend from the rounded anterior end, almost to but not including the tip of the somewhat pointed tail.
○ Found in subcutaneous tissue and not blood specimens.

● Adult worms
○ Thin and wirelike in appearance.
○ Col up in knots inside infected skin nodules.
○ Females: 500 mm in length
○ Males: 25 - 50 mm in length

Question 18

morphology of microfilariae and adult worm of Mansonella ozzardi

Answer 18

● Microfilariae
○ 220 um long
○ Sheath is absent
○ Numerous nuclei that do not
extend to the tip of the long, narrow, and tapered tail
○ Rounded, blunt anterior end
○ The posterior end is short and not as tapered as that of Onchocerca.

● Adult worms
○ Females: 65 - 80 mm; Average of
70 mm in length.
○ Males: 32 mm in length.

Question 19

morphology of microfilariae and adult worm of Mansonella perstans

Answer 19

● Microfilariae
○ 200 um long
○ Sheath is absent
○ Body is filled with nuclei that
extend all the way to the tip of the tail
○ Anterior or tail end is rounded and blunt.
● Adult worms
○ Females: 82 mm in length
○ Males: 43 mm in length
○ Resides in peritoneal and pleural
cavities as well as the mesentery

Question 20

specimen of choice and lab diagnostic method of choice
for each filariae
1. Wuchereria bancrofti
2. Brugia malayi
3. Loa loa
4. Onchocerca volvulus
5. Mansonella ozzardi
6. Mansonella perstans

Answer 20

SOC:
every filariae is blood except for
Onchocerca volvulus: skin snips

lab diagnostic method of choice:
1. Examination of fresh Giemsa-stained blood (detects microfilariae)
2. Examination of stained blood films (detects microfilariae)
3. Examination of microfilariae in
Giemsa-stained blood.
4. Examination of microfilariae in Giemsa-stained slides of tissue biopsies.
5. Examination of microfilariae in Giemsa-stained blood
6. not stated

Question 21

lab diagnosis for Wuchereria bancrofti

Answer 21

HEPARINIZED BLOOD (blood that does not clot)
○ More sensitive method for microfilariae recovery.
○ Blood is filtered through a nucleopore filter, and then the filtered contents are stained and
examined

KNOTT TECHNIQUE
○ Light infections
○ 1 ml blood mixed with 10 mL of 2% soln. of formalin, and then centrifuged. Sediment is spread like a thin blood film, stained and examined.

[heparinized blood - more sensitive method
knott technique - light infections, when few worms are in the blood]

other tests:
- serologic tests - including antigen and antibody detection
- PCR assays

Question 22

lab diagnosis for Brugia malayi

Answer 22

Knott Technique other tests: - serologic methods

Question 23

lab diagnosis for Loa loa

Answer 23

Knott Technique other tests: - serologic methods

Question 24

lab diagnosis for Onchocerca volvulus

Answer 24

Skin snips should be obtained with as little blood as possible to avoid contamination of the sample with other species of microfilariae that may be present in the blood Adult worms may be recovered from infected nodules. other lab tests: - serologic test (check for antibodies that fight the parasite) - PCR test: detect low-lvl infections (detects even a small no. of worms in the body)

Question 25

how are organisms residing in the eye are best seen by in Onchocerca volvulus

Answer 25

ophthalmologic examination using a slit lamp (special microscope) - to look for worms inside the eyes eye doctor (ophthalmologist)

Question 26

why do we need to avoid blood in skin snips

Answer 26

If there’s too much blood, the sample might get mixed with other worm species from the bloodstream, making the test confusing.

Question 27

what are the diagnosis to look for Onchocerca volvulus

Answer 27

patient history travel residence history presence of eosinophilia (increases when there is a parasitic infections) ocular discomfort

Question 28

periodicity for each parasite 1. Wuchereria bancrofti 2. Brugia malayi 3. Loa loa 4. Onchocerca volvulus 5. Mansonella ozzardi 6. Mansonella perstans

Answer 28

1. nocturnal periodicity ○ Peak hours: 9:00 PM - 4:00 AM ○ Present at night 2. nocturnal periodicity ○ Specimens collected during the nighttime hours - most likely to yield large numbers of circulating microfilariae. 3. diurnal periodicity ○ Peak hours: 10:15 AM - 2:15 PM *Migrating adult worms may be extracted from a variety of body locations, including the eye. 4. not stated 5 and 6. non-periodic ○ No known optimum time for collecting the blood sample ○ Can be collected at any time

Question 29

what are the diagnosis to look for Loa loa

Answer 29

residence in an endemic area travel history eosinophilia, calabar transient subcutaneous swelling

Question 30

epidemiology 1. Wuchereria bancrofti 2. Brugia malayi 3. Loa loa 4. Onchocerca volvulus 5. Mansonella ozzardi 6. Mansonella perstans

Answer 30

1. Found in the subtropical and tropical areas of the world. ○ Central Africa, Nile, Delta, India, Pakistan, Thailand, Arabian sea coast Philippines, Japan, Korea, China, Haiti, Dominican Republic, Costa Rica, Brazil. 2. Mosquito breeds that primarily located in the Philippines, Indonesia, Sri Lanka, New Guinea, Vietnam, Thailand, and specific regions of Japan, Korea, and China 3. Chrysops fly inhabits Africa, especially the rainforest belt region. 4. Africa and Central America, East Africa, Zaire, Angola, parts of Mexico, Colombia, Brazil, and portions of Venezuela 5. Known to exist in North America, Central. and South America, parts of the West Indies and Caribbean. Bolivia, Colombia, Peru, Hait, the Dominican Republic, and Puerto Rico. 6. Parts of Africa, selected areas in the Caribbean Islands, Panama, and northern South America. *Primates (monkeys and apes) are thought to harbor M. perstans or a closely related species as reservoir hosts. [act as reservoir hosts, meaning they help the parasite survive in nature and can pass it to humans through insect bites.]

Question 31

this spp is also known to infect felines and monkeys.

Answer 31

Brugia malayi *Primary Definitive Host: Human

Question 32

life cycle of Wuchereria bancrofti

Answer 32

● Vector and Intermediate Host: ○ Mosquito (Culex, Aedes, and Anopheles spp.) *These are the genera of the mosquitoes. ● In the human host, ○ Adult worms reside in the lymphatics where they lay their microfilariae. ● Microfilariae live in the blood and lymphatics.

Question 33

life cycle of Brugia malayi

Answer 33

● Vector ○ Mosquito (Aedes, Anopheles and Mansonia spp.) ○ Anopheles mosquito can also transmit W. bancrofti as co-infection - Co-infection: anopheles mosquito can transmit W. bancrofti and B. malayi infection *All other aspects of the life cycle of B. malayi are similar to that of W. bancrofti

Question 34

life cycle of Loa loa

Answer 34

● Vector: Chrysops fly ● Adult worms take up residence and multiply throughout the subcutaneous tissues. ● Microfilariae are present in the blood.

Question 35

life cycle of Onchocerca volvulus

Answer 35

● Vector: Simulium blackfly ○ Breeds in running water, particularly along streams and rivers ● Resulting adult worts encapsulate in subcutaneous fibrous tumors where they coil and microfilariae emerge. ● Microfilariae may migrate to infected nodules, subcutaneous tissues, skin, and into the eye. - may cause blindness.

Question 36

life cycle of Mansonella ozzardi

Answer 36

● Vector: Culicoides sucking midge or Simulium blackfly ● M. ozzardi is transferred by the injection of infective larvae to the human definitive host.

Question 37

life cycle of Mansonella perstans

Answer 37

● Vector: Culicoides sucking midge ○ The insects usually settle in areas in and around the eye. ● Life cycle of M. perstans is similar to that of M. ozzardi ● Incubation period of this organism once inside the host is unknown.

Question 38

what are the clinical symptoms of Wuchereria bancrofti

Answer 38

ASYMPTOMATIC ○ Adult patients, who were exposed during childhood to W. bancrofti, may become infected and experience no symptoms. ○ Eosinophilia in the blood may be noted in blood tests - some light infection can still observe eosinophilia (high eosinophil count in the blood). ○ Physical examination reveals enlarged lymph nodes in the groin area. ○ Self-limiting infections due to adult worms eventually dying and there are no signs of microfilariae being present. ○ Patients may undergo the entire process and not even know it. [The infection may go away on its own if the worms die without leaving baby worms (microfilariae)] SYMPTOMATIC 🔹 Bancroftian Filariasis - Fever, chills, eosinophilia, formason of granulomatous lesions. lymphangitis, and lymphadenopathy. - Bacterial infections with Streptococcus may also occur. (Secondary infections) 🔹 Severe Cases: Elephantiasis - swelling of the lower extremities. genitals and breasts may also be involved. - Calcification or formation of abscesses may occur on the death of adult worms. [Dead worms can harden (calcify) or cause pus-filled infections (abscesses)]

Question 39

treatment, prevention and control of Wuchereria bancrofti

Answer 39

● Treatment ○ Diethylcarbamazine (DEC) and Ivermectin (Stromectol) when used in combination with albendazole. ○ Surgical removal of excess tissue may be appropriate for the scrotum. ○ Unna's paste boots, elastic bandages, or simple elevation, have proven successful in reducing the size of an infected enlarged limb. ● Prevention and Control - using personal protection when entering known endemic areas - destroying breeding areas - using insecticides - educating the inhabitants of endemic areas

Question 40

clinical symptoms of Brugia malayi

Answer 40

OFTEN ASYMPTOMATIC - eve w the presence of microfilariae in the blood - fevers may take months to years to develop after initial infection (slow infection after initial infection) - formation of granulomatous lesions, microfilariae invasions into the lymphatics, chills, lymphadenopathy, lymphangitis and eosinophilia - elephantiasis of the legs - elephantiasis of the genitals is possible but less common

Question 41

treatment, prevention and control of Brugia malayi

Answer 41

● Treatment ○ Similar to that for W. bancrofti, with the most useful medication being diethylcarbamazine (DEC) ○ Side effects may include inflammatory reactions after treatment and can be severe. ● Prevention and Control - using personal protection when entering known endemic areas - destroying breeding areas - using insecticides - educating the inhabitants of endemics areas

Question 42

clinical symptoms of Loa loa

Answer 42

LOASIS ○ Pruritus or itching and localized pain. ○ Calabar swellings at the site. ○ Localized subcutaneous edema may occur anywhere on the body and is thought to result from the migration and death of the microfilariae ○ Adult worms may only be noticeable when seen migrating under the conjunctiva of the eye or crossing under the skin of the bridge of the nose.

Question 43

treatment, prevention and control of Loa loa

Answer 43

● Treatment ○ Treatment of Choice: Surgical removal of adult L. loa worms ○ Ideal time to remove the adult worms are when they are attempting to cross the eye or the bridge of the nose. ○ Medication of Choice: Diethylcarbamazine (DEC) ■ Known to be effective but should be used with caution as it may result in serious side effects, such as encephalitis in heavily infected patients. ● Prevention and Control - using personal protection, destroying breeding areas - use of prophylactic DEC

Question 44

clinical symptoms of Onchocerca volvulus

Answer 44

● Onchocerciasis: River Blindness ○ Chronic and non-fatal condition - can cause blindness ○ Localized symptoms caused by the development of infected nodules ○ Severe allergic reactions to the presence of microfilariae ○ Scratching leads to secondary bacterial infections ○ When the eye is involved, lesions, due to the body's reaction to the microfilariae, may lead to blindness. ○ Changes in overall skin appearance, such as loss of elasticity, and location of nodules in the body.

Question 45

treatment, prevention and control of Onchocerca volvulus

Answer 45

● Treatment ○ Drug of Choice: Ivermectin ○ No known medication that destroys both adult worms and microfilariae without some toxic effects or complications. ○ Therapy may be necessary for very long periods of time due to the long life of adult worms. ■ Can live up to 15 years or more. ○ Surgical removal of adult worms may be performed. ● Prevention and Control - using personal protection - controlling the vector breeding grounds with the use of insecticides

Question 46

clinical symptoms of Mansonella ozzardi

Answer 46

● Asymptomatic infections are common. ● Symptoms such as eosinophilia, urticaria, lymphadenitis, skin itching, and arthralgia may occur. ● Adult worms cause minimal damage to the areas they inhabit.

Question 47

treatment, prevention and control of Mansonella ozzardi

Answer 47

● Asymptomatic infections are not typically treated. ● Those who require treatment usually receive ivermectin. ● DEC has proven to be ineffective.

Question 48

clinical symptoms of Mansonella perstans

Answer 48

● Worms usually appear singly, therefore, damage to affected tissue is minimal. ● Minor allergic reactions or no symptoms at all. ● Some may exhibit moderate eosinophilia, presence of Calabar swellings, headache, edema, and lymphatic discomfort. ● May be responsible for joint and bone pain, as well as enlargement and associated pain in the liver

Question 49

treatment, prevention and control of Mansonella perstans

Answer 49

● Treatment ○ Treatment of Choice: Diethylcarbamazine (DEC). ○ Alternative Mebendazole. ○ Ivermectin has not been proven effective. *Asymptomatic infections are often not treated ● Prevention and Control - using insecticides targeted against the vector, personal protection

Question 50

why should heavily infected patients should take Diethylcarbamazine (DEC) with cautions

Answer 50

as it may result in serious side effects such as encephalitis but it is known to be effective

Question 51

what is a distinctive symptoms of Loa loa and how is it different from Onchocerca volvulus

Answer 51

distinctive symptoms: Adult worms migrating across the conjunctiva (surface of the eye). difference: Loa loa - visible migration of adult worms across the conjunctiva = calabar swelling *can also be seen under the skin, often on the nose Onchocerca volvulus - causes blindness but no visible migration of worms in the eye.