filariae Flashcards
filariae
phylum:
class:
pathogenic vs non-pathogenic filariae
phylum: nemathelminthes
class: nematoda
pathogenic:
Wuchereia bancrofti
Brugia malayi
Loa loa
Onchocerca volvulus
non-pathogenic:
Mansonella ozzardi
Mansonella perstans
true or false:
The basic life cycle is the same for all members of the filariae.
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.]
briefly explain the 2 morphological forms
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
How does a person get infected with filarial worms?
an infected arthropod insect bites a person and injects 1 to 4 infective larvae at the feeding site
(it initiates the human infection)
what are the 2 key characteristics helpful in speciating the microfilariae forms
distribution of nuclei
presence or absence of a delicate transparent covering (aka sheath)
briefly explain the life cycle of a filariae
- larvae migrate to the tissue for their development
[After entering through a mosquito bite, the larvae move to tissues to grow] - resulting adult worms reside in the lymphatics, subcutaneous tissue or intestinal body cavities (peritoneal cavity etc)
- 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] - 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).] - larvae development into infective stage takes place in the insect host
[Inside the mosquito, the baby worms develop into the infective stage.] - parasite is transferred into uninfected humans
[infected mosquito bites another person, it injects the larvae, starting the cycle again.]
Definitive Host vs. Intermediate Host
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
A phenomenon whereby the parasites are present in the bloodstream during a specific time.
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!]
what are the 3 types of periodicity
- Nocturnal - occurring at night
- Diurnal - occurring during the day
- Subperiodic - the timing of occurrences is not clear-cut
the primary method of diagnosis for filariae
- Microscopic examination of the
microfilariae in Giemsa-stained blood - A tissue scraping of an infected nodule
*whole blood samples may also be collected
what are the other blood test
SOC: whole blood
- knott technique
- membrane filtration
*Knott technique and Membrane filtration is used for low microfilaremia (low microfilariae in blood.)
- serologic test
- have been develop and available
-however, concern as to their specificity and thus considered as viable diagnostic techniques
why is serologic test are not always reliable
as they might give false results
- these tests checks for immune system reactions to the parasite
how to perform knott technique
- 1 mL of blood can be mixed with 140 mL of 2% formalin and then centrifuged.
- The supernatant is discarded and the sediment is studied.
[after centrifugation, sediment sa bottom of test tube] - Spread like a thin blood film, fixed and stained.
[can view under the microscope]
how to perform membrane filtration
makes use of syringe attached to a Swinney filter holder
- 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. - Lyzed blood is then passed through the Swinney membrane filter where microfilariae will be recovered.
- A membrane filter can be examined like a wet smear preparation or may be dried, fixed, and then stained.
○ Afterwards, view under the
microscope.
this blood test makes use of syringe attached to a Swinney filter holder
membrane filtration
common name and common associated disease/ condition names for each filariae
- Wuchereria bancrofti
- Brugia malayi
- Loa loa
- Onchocerca volvulus
- Mansonella ozzardi
- Mansonella perstans
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)
morphology of microfilariae and adult worm of Wuchereria bancrofti
● 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
morphology of microfilariae and adult worm of Brugia malayi
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
morphology of microfilariae and adult worm of Loa loa
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
morphology of microfilariae and adult worm of Onchocerca volvulus
● 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
morphology of microfilariae and adult worm of Mansonella ozzardi
● 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.
morphology of microfilariae and adult worm of Mansonella perstans
● 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
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
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
lab diagnosis for Wuchereria bancrofti
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
lab diagnosis for Brugia malayi
Knott Technique
other tests:
- serologic methods
lab diagnosis for Loa loa
Knott Technique
other tests:
- serologic methods
lab diagnosis for Onchocerca volvulus
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)
how are organisms residing in the eye are best seen by in Onchocerca volvulus
ophthalmologic examination using a slit lamp (special microscope)
- to look for worms inside the eyes
eye doctor (ophthalmologist)
why do we need to avoid blood in skin snips
If there’s too much blood, the sample might get mixed with other worm species from the bloodstream, making the test confusing.
what are the diagnosis to look for Onchocerca volvulus
patient history
travel
residence history
presence of
eosinophilia (increases when there is a parasitic infections)
ocular discomfort
periodicity for each parasite
1. Wuchereria bancrofti
2. Brugia malayi
3. Loa loa
4. Onchocerca volvulus
5. Mansonella ozzardi
6. Mansonella perstans
- nocturnal periodicity
○ Peak hours: 9:00 PM - 4:00 AM
○ Present at night - nocturnal periodicity
○ Specimens collected during the nighttime hours - most likely to yield large numbers of circulating microfilariae. - 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.
- not stated
5 and 6. non-periodic
○ No known optimum time for collecting the blood sample
○ Can be collected at any time
what are the diagnosis to look for Loa loa
residence in an endemic area
travel history
eosinophilia,
calabar
transient subcutaneous swelling
epidemiology
1. Wuchereria bancrofti
2. Brugia malayi
3. Loa loa
4. Onchocerca volvulus
5. Mansonella ozzardi
6. Mansonella perstans
- 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. - Mosquito breeds that primarily located in the Philippines, Indonesia, Sri Lanka, New Guinea, Vietnam, Thailand, and specific regions of Japan, Korea, and
China - Chrysops fly inhabits Africa, especially the rainforest belt region.
- Africa and Central America, East Africa, Zaire, Angola, parts of Mexico, Colombia, Brazil, and portions of Venezuela
- 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. - 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.]
this spp is also known to infect felines and monkeys.
Brugia malayi
*Primary Definitive Host: Human
life cycle of Wuchereria bancrofti
● 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.
life cycle of Brugia malayi
● 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
life cycle of Loa loa
● Vector: Chrysops fly
● Adult worms take up residence and multiply throughout the subcutaneous tissues.
● Microfilariae are present in the blood.
life cycle of Onchocerca volvulus
● 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.
life cycle of Mansonella ozzardi
● Vector: Culicoides sucking midge or Simulium blackfly
● M. ozzardi is transferred by the injection of infective larvae to the human definitive host.
life cycle of Mansonella perstans
● 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.
what are the clinical symptoms of Wuchereria bancrofti
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)]
treatment, prevention and control of Wuchereria bancrofti
● 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
clinical symptoms of Brugia malayi
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
treatment, prevention and control of Brugia malayi
● 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
clinical symptoms of Loa loa
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.
treatment, prevention and control of Loa loa
● 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
clinical symptoms of Onchocerca volvulus
● 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.
treatment, prevention and control of Onchocerca volvulus
● 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
clinical symptoms of Mansonella ozzardi
● 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.
treatment, prevention and control of Mansonella ozzardi
● Asymptomatic infections are not typically treated.
● Those who require treatment usually receive ivermectin.
● DEC has proven to be ineffective.
clinical symptoms of Mansonella perstans
● 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
treatment, prevention and control of Mansonella perstans
● 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
why should heavily infected patients should take Diethylcarbamazine (DEC) with cautions
as it may result in serious side effects such as encephalitis
but it is known to be effective
what is a distinctive symptoms of Loa loa and how is it different from Onchocerca volvulus
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.
