Filarial Nematodes - Onchocerciasis, Filariasis, Loiasis Flashcards
Why are Tetracyclines effective against helminths? Eg onchocerciasis and filarisis
How long rx?
They depend on intracellular bacteria - Wolbachia for their development and fertility
- Wolbachia are sensitive to Tetracyclines
Requires 6 weeks of treatment
Onchocerciasis size of adult worm? Full name?
Basic life cycle? Key vector
- 40cm long and can live 15 years
-Onchocerca volvulus - lives in sub cut tissue and produces microfilariae (350um)
- These are taken up by a blackfly called Simulium
Where do simulium flies live?
Fast flowing water -> get Onchocerasis mostly in people living near rivers
Onchocerciasis 3 key parts of sx
- Cutaneous itchy papular rash (leopard skin)
- Sub cutaneous nodules
- Eye disease (river blindness)
How does Onchocerasis present on the skin? How does it progress? Often mistaken for?
- Acute/chronic papular onchodermatitis
- Itchy, hyperpigmented papules
- Can progress to atrophy and depigmentation of skin which leads to excessive wrinkles (or ‘hanging groin’ appearance)
- also called leopards skin
- Often initially mistaken for scabies
What causes the subcutaneous nodules in Onchocerciasis
Adult worms getting trapped and becoming enclosed in fibrous tissue
Eye disease in Onchocerasis (2 types)
- Anterior keratitis ‘snow flake’ opacity visible. This pannus may continue to sclerose and cover cornea
- Posterior Eye- may present with widespread chorioretinitis with pigment changes. Sometimes accompanied by optic atrophy
Diagnosis Onchocerasis? What is the rapid diagnostic test called?
- Skin snip / biopsy for microfilariae (insensitive)
- Can use PCR - rare and expensive
- Rapid diagnostic test LIPS (Luciferase immunoprecipitation system) assay. This can also distinguish between O volvulus, W Bancrofti, l loa and stronglyotides.
Onchocerciasis rx?
Doxy for 6 weeks then single dose ivermectin
Ivermectin - can be used for mass chemo
- Doxy can be used to target Wolbachia AND also kills adults if 6 week course
- Ivermectin Doesn’t work well on adult worms so often need multiple doses over many years
- (Moxidectin is a potent version of ivermectin)
High load loa microfilaraemia rx eg >2500Mf/ml? Why not ivermectin
Either Albendazole for 3 weeks then DEC
Or Apheresis prior to DEC
Ivermectin -> facilitates loa entry into CNS
How do most Onchocerasis eradication programs work
Mass chemo with ivermectin
Cause of lymphatic filariasis? How big do they get? Vector ? What is required for its sexual reproduction?
- Wuchereria bancrofti. Males 4cm females 10cm and release 10000 microfilariae daily
- Mosquito - various types but key one is culex quinquefasciatus which breads in drains / polluted water
- Wolbachia bacteria
Filariasis key sx
- Often get fever
- Acute filarial lymphangitis (death of worm and inflammatory response to it) . Inflam nodule which may form an abscess
- Elephantiasis
- Often get bacterial infections in lymphatic due to slow flow / breaks in skin
- Often epididymitis / hydrocoele etc
- chyluria
Filariasis dx?
- immunochromatographic card test (ICT) - now first line
[Rapid diagnostic test] - ELISA or PCR
- Peripheral thick blood films with Giemsa stain. Works best in middle of night
Which form of filariasis in Asia with milder symptoms and only rare elaphantitis
Brugia Malayi
Management of filariasis if single diagnosis? If confection with Onchocerasis?
Diethylcarbamazine 6mg/kg for 12 days
- AND 6 weeks Doxy
If Onchocerciasis too, give Ivermectin
- then DEC 4 weeks later
Filariasis control strategies
- Mass drug administration (albendazoe / ivermectin / diethlycarbamazine
- Morbidity management + disability prevention
- Vector control - mosquito nets and treatment of enclosed water in towns with polystyrene beads prevents mosquitos breading
Loasis ‘the eye worm’ is transmitted by? Size of adult worm?
- Chrysops - Red flys from tropical forests in Africa
- 3-7cm
What is the name for trauma caused by migrating loa in extremities
Calabar swelling
Loasis dx
- May complain of worms in white of eye
- Thick blood films with Giesma staining
Loasis rx ? How to prevent mazzoti reaction? What to do if high microfilariae load >2500Mf/m
- Diethycarbamazine 2mg/kg for 7-10 days
- Add ivermectin 150ug/kg as a single dose prior to treatment to help prevent mazzoti reaction
- High Mf load - course of albendazole prior to Diethylcarbamazine
OR if rich -> pre-treatment apheresis
Treatment of filarial infection then several days later develops fever urticaria, swollen tender lymph nodes ans appears shocked with abdo pain and arthralgia? Key drug?
Mazotti reaction - most commonly after DEC (but could be other microfilarial chemo)
Occur within 7 days
Lymphatic filariasis life cycle
L3 lava injected by culex (usually)
Male and female mate in lymphatic
Produce microfiliarae L1 which would not infect humans.
mosquito takes up
Matures into L2 then L3 in mosquito
Differential to lymphatic filariasis that is caused by silica
Podoconiosis - disease will be bilateral
Name 3 Ddx with firm skin nodules
Cutaneous Cysticercosis
Bot fly
Abscess
Onchocerciasis
What time best for loa loa blood film
4pm
Lymphatic fil + oncho rx?
First treat the onchocerciasis with Ivermectin or Moxidectin 8 mg po
as single dose;
wait one month and then give DEC for lymphatic filariasis
Lymph + loa rx
If < 2,500 Loa loa microfilaria/mL, Diethylcarbamazine 21 days.
If > 2,500 Loa loa microfilaria/mL, refer to expert center for possible pre-treatment apheresis.
* Or give Ivermectin 150 µg/kg po once followed by single dose of DEC 6 mg/kg
> 20,000 - Doxy only
2 bugs that cause lymphatic filariasis
Wuchereria bancrofti 90%
Brugia malayi 10% - only causes below knee sx eg cold abscesses but no hydrocoele.
What causes chyluria in lymphatic filariasis
Anastomosis between abdo lymphatic and renal collecting system
Tropical pulmonary eosinophilia 90% in who. Key sx
Young males 90%
Wheeze - ONLY at night classically
US lymphatic filariasis key finding
Filiarial dance sign in scrotal lymphatics
Why not DEC for lymphatic filariasis control program
Side effects + bad reactions if coinfection eg oncho
Usually use ivermectin instead
Why Doxy 4 weeks then ivermectin if lymphatic filariasis confection with Onchocerasis rather than diethlycarbamazine?
DEC + Oncho -> inflammation -> Risk of blindness if microfilariae in eye
What is mazotti test
Give small amount of DEC in Onchocerasis
Become intensity itchy
[Dangerous as may cause blindness]
2 cause of lymphatic filariasis
Wuchereria bancrofti 90%
Brugia malayi 10% - only causes below knee sx eg cold abscesses but no
2 cause of lymphatic filariasis
Wuchereria bancrofti 90%
Brugia malayi 10% - only causes below knee sx eg cold abscesses but no
What are options for lymphatic filariasis? Which eradicate macro vs microfilarial. Which for individual cases?
DEC + doxy
Drugs of choice individual cases
aggressive macrofilaricidal regimen; 20% eradication
Single dose is microfilaricidal
Ivermectin
Single dose microfilaricidal; control programs
Not macrofilaricidal
Albendazole
Single dose micro and somewhat macrofilaricial
DEC/ALB combination
Aggressive Rx for 1 week then repeat annually
80% antigen clearance rate at 4 years
Oncho + loa rx
Ivermectin first (for oncho)
Then DEC for loa loa
Loa rx
- Screen for others first and if mono infection
- Check loa load
<2500microfilaria/ml
Diethylcarbamazine for 21 days
> 2500microfilaria/ml
Refer for apheresis prior to therapy
OR albendazole for 3weeks then DEC
Oncho monoinfection Rx
Doxy for 6 weeks
then single dose ivermectin
What abx contraindicated in oncho
DEC
loa + oncho infection rx
Oncho rx first with Ivermectin IF loa <2500microfil/ml
wait 6 months then treat loa with Diethylcarbamazine
If >2500mf/ml requires pre treatment apheriesis
Lymphatic filariasis mono infection rx
diethylcarbamazine single dose
6 weeks doxy
Lymphatic filariasis + oncho rx
1st treat oncho with ivermectin /moxidectin
Wait 1 month then DEC for Lymphatic filariasis
Lymphatic filariasis + loa rx
If <2500 loa microfil/ml
Diethylcarbamazine for 21 days
If >2500 may need treatment apheresis
OR ivermectin
THEN Diethylcarbamazine
Lymphatic filariasis + >20,000mf/ml of loa rx
Doxycycline only
Filariasis life cycle
Onchoceraisis life cycle
Loa loa life cycle
What disease might I give you?
Chrysops
vector of Loa loa
A wuchereria - Sheath. no nucleus at the end. Head end nuclei really obvious
B brugia - Sheath, has a sub terminal amd terminal nucleus
C o volvulus - Skin snip nuclei don’t get to end
D loa loa - Sheath, nuclei are large and longer.
E m Perstans - No sheath nuclei to end
F m streptocerca -Skin nuclei to end. Tail almost always has a J shape
G m ozzardi - No sheath nuclei not to end (ONLY filaria in Peru)
B Malayi
Best test for bancrofti
Rapid Card test
Which 2 microfilariae in the skin? Differentiate
O volvulus - nuclei don’t get to end
[0 nuclei at the end]
Mansonella streptocerca- nuclei to end. Tail almost always has a J shape
[cerca - like onchocerca = both in skin]
Which 3 blood born microfiliarae have a sheath? Differentiate them?
Wuchereria bancrofti - no nucleus at the end. Head end nuclei really obvious
Brugia malayi - has a sub terminal amd terminal nucleus (big gap between them)
Loa loa - nuclei are large and longer. Head nuclei not really obvious
Which 2 blood born microfiliarae don’t have a sheath? Differentiate
Mansonella Perstans - nuclei to end
Mansonella ozzardi - nuclei not to end and not very distinct
-Only filaria in Peru
-[Ozzardi O nuclei at end]
Which filiarial infection best blood film at night?
4pm?
Wuchereria bancrofti at night
loa loa at 4pm
Which filiarial has a circulating antigen test? What is important about this?
Wuchereria bancrofti
Tells you there is a viable adult worm not just microfilariae
ELISA or rapid card/strip test
Wuchereria bancrofti - Sheath no nucleus at the end. Head end nuclei really obvious
Wuchereria bancrofti - Sheath no nucleus at the end. Head end nuclei really obvious
Wuchereria bancrofti - Sheath no nucleus at the end. Head end nuclei really obvious
Brugia malayi - Sheath - has a sub terminal amd terminal nucleus (big gap between them)
Brugia malayi - has a sub terminal amd terminal nucleus (big gap between them)
Loa loa - Sheath . nuclei are large and longer. Head nuclei not really obvious
Loa loa - Sheath . nuclei are large and longer. Head nuclei not really obvious
Loa loa - Sheath . nuclei are large and longer. Head nuclei not really obvious
O. volvulus in a subcutaneous nodule
O. volvulus in a subcutaneous nodule
O. volvulus in a subcutaneous nodule
Skin
Onchocerca volvulus - nuclei don’t get to end
Onchocerca volvulus - nuclei don’t get to end
In skin
Mansonella Perstans - Blood, no sheath, nuclei to end
Mansonella Perstans - Blood, no sheath, nuclei to end
Why cant you treat loa >2500mf/ml with ivermectin
Facilitation of loa migration into CNS -> bad
26 yo man with 6 yr working in Africa
ROS mild swelling in the forearms.
Loa loa (calabar swelling)
Hydrocoele after living in Africa for a while
Wuchereria bancrofti
(Brugia malayi - only usually below knee )
