Filariasis Flashcards
What are filarial nematodes?
Thread like worms which live in the blood.
What are the three species that cause lymphatic filariasis and where are they found geographically?
Wuchereria bancrofti (tropics), Brugia malayi (south east asia), Brugia timori (Indonesia)
What are the vectors of lymphatic filarial worms?
Mosquitoes
Where is the location of adult worms in LF?
lymph
Where is the location of larvae in LF?
blood
How do you distinguish between W.bancrofti and B.malayi?
Both sheathed, bancrofti nuclei don’t extend to tip of tail, B.malayi have a gap and then 2 terminal nuclei.
Describe life cycle of B.malayi and W.bancrofti
- Mosquito takes a blood meal, L3 larvae enter skin of human.
- Larvae migrate to lymph nodes and develop into adult worms.
- Adult worms produce sheathed microfilariae that are released into bloodstream.
- Mosquito takes a blood meal and ingests MF.
- MF shed sheath, penetrate midgut and migrate to thoracic muscles.
- Migration of larvae to proboscis.
What are the symptoms of LF?
elephantiasis, hydrocoele, lymphangitis, secondary infections
LF methods of control?
mosquito control, large scale treatment of a population with albendazole and either ivm or dec to clear mf in blood
LF treatment?
surgery for hydrocoele, albendazole + ivm or dec, doxycycline for wolbachia therapy
When should a blood smear for diagnosis of LF be taken?
9pm-2am because of nocturnal periodicity- MF less active during the day as the mosquitoes bite at night
What methods of LF diagnosis are there?
Giemsa stained thick blood smear
CFA antigen test (Bancrofti)
Brugia rapid dipstick
Ultrasound detection of adult worms
What is hydrocoele
swelling of scrotum
In filarial worms what does wolbachia depletion do?
- Blocks embryogenesis- so no release of MF
- Blocks transmission as parasites unable to develop in mosquito without it-no mf
- adults die 1-2 years later
What is the current AWOL goal for the future?
find a new anti-wolbachia drug with…
- less than 7 days regimen
- utility in children and women of child bearing age
- alternative drug against resistant parasites
- safe drug for Loa loa co-endemic areas
What is the common name for Loiasis?
African Eye Worm
What is the vector of Loa loa?
Chrysops ( horsefly/ deerfly)
Where is Loa loa found?
Central and West Africa- affects forest dwellers
How can you diagnose Loa loa?
- adult worm visible migrating across front of eye
2. sheathed MF visible in blood film between 10am-2pm.
What are the symptoms of loa loa?
Calabar swellings, itching, eye worm, eosinophilia
Describe the life cycle of Loa loa
- Day biting of fly, injects L3 into host
- Migrate to subcutaneous tissue and mature into adults
- Adult males and females mate and produce sheathed MF that migrate to skin, blood, urine, lungs, CNS.
- Adult worms migrate through skin and eyes
- MF taken up by fly bite
- MF mature through several larval stages in fly and migrate to proboscis
Treatment of Loa loa
Surgical removal of worms under skin and across eye
Prevention of Loa loa
prevent bites, DEC prophylaxis (kills mf and adults), vector control
What parasite causes river blindness and what is the vector?
Onchocerca volvulus, blackfly (Similum genus)
Describe the life cycle of Onchocerca volvulus
- Blackfly takes blood meal and L3 enter bite wound.
- migrate to subcutaneous tissue
- form nodules as they mature into adult worms
- adult males and females mate within nodules
- females release unsheathed MF which migrate to skin
- blackfly takes a blood meal and ingests MF
- MF mature through larval stages and migrate to proboscis
Symptoms of river blindness
- itchy skin rashes, skin nodules, vision changes ( due to immune response to dying MF)
- blindness(immune response to dying mf in eye)
- lizard skin atrophy ‘aging’
- leopard skin
Diagnosis of river blindness
skin snip, examine eye, antibody test, pcr
Treatment of river blindness
ivermectin, doxycycline, NO DEC
prevention of river blindness
mass treatment at risk populations with ivermectin every 6-12 months
vector control
protect against bites
What are the advantages of other diagnostic methods of LF over microscopy?
Can be taken any time of day, quick, whole blood fingerprick, more sensitive than mf
what does MMDP stand for and what does it involve?
Morbidity Management Disability Prevention
Exercises, elevation, cleaning leg
When do deerflies bite?
During the day
What is Mansonellosis?
Skin filariasis caused by species of Mansonella species (M. ozzardi, M. perstans, M. streptocerca. Vector is midgies.
What are calabar swellings?
Local skin swellings with oedema produced as worms migrate through skin.
What parasite and vector causes Guinea worm?
Dracunculus medinensis, water flea
Describe life cycle of guinea worm
- Cyclops ‘water flea’ eats L1 and matures.
- Ingestion of water containing infective L3 (either by human or fish/frogs)
- Larvae penetrate gut wall of host when flea dies
- Fertilized adult female migrates to skin surface and causes ulceration.
- Release of L1 on contact with water
Treatment of guinea worm
- wind worm out around a matchstick over several days, but it can burst, releasing bacteria and causing cellulitis
- tiabendazole decreases inflammation
- prophylactic antibiotics
Diagnosis of guinea worm
skin ulceration and emerging worm
Prevention of guinea worm
- safe drinking water
- encourage infected people to avoid water during worm emergence
- avoid bathing in a source of drinking water- disease mapping
- health education
Define control
The reduction of disease incidence, prevalence, morbidity or mortality; continued intervention measures are required to maintain the reduction
Define elimination of disease
Reduction to zero of the incidence of a specified disease; continued intervention measures are required.
Define elimination of infection.
Reduction to zero of the incidence of infection; continued measures to prevent re-establishment of transmission are require
Define eradication
Permanent reduction to zero of the worldwide incidence of infection; intervention measures are no longer needed.
What are main methods of prevention of filariasis?
MDA and vector control
what are anti-wolbachia mode of action beneftis
- curative- slow kill avoids side effects
- safe in loa loa co-infection
- permanently sterilises adult worms- no recrudescence
- blocks transmission
- improves clinical disease
why does the parasite need wolbachia?
- needed in many metabolic pathways such as tca cycle, purine and pyrimidine biosynthesis, supports growth and development of filarial nematodes at times of greatest metabolic demand
- most at L4 stage
- found in hypodermal cord cells and near reproductive organs in females
