Filiarial Worms Flashcards
What is the epidemiology of Lymphatic Filariasis?
Sub-Saharan Africa
South East Asia
Small pockets of South America
Increased incidence age
120 million cases
2nd commonest cause of disability worldwide
What are the parasites that cause Lymphatic Filariais?
Wuchereria Bancrofti
Brugia Malayi
Brugia Timori
What vectors are associated with W. Bancrofti?
Anopheles, Culex, Adaes, Mansoni
What vectors are associated with Brugia Malayi
Mansoni
What is the periodicity of Brugia Malayi?
Some have nocturnal periodicity
Some have sub-periodic periodicity
Which parasite of Lymphatic Filariasis also infects animal hosts like monkeys, cats
Brugia Malayi
What is the most prevalent Parasite of Lymphatic Filariasis?
Wuchereria Bancrofti (90% of cases)
What bacteria has a symbiotic relationship with LF and Onchocerciasis?
Wolbachia
What is the lifecycle of Lymphatic Filariasis?
L3 Larva –> Enter into lymphatics –> Sheathed microfilariae which live in blood and lymphatics –> taken up by mosquito at a further feed –> Enter into the mosquito gut and develop into L1 larvae –> L3 larvae in the probiscis, ready for the next feed
What is the pathophysiology of lymphatic filariasis and scarring?
Adult filarial worms provoke huge inflammatory responses when they die –> Granuloma formation and lymphatic scarring –> Lymphangitis and Lymphadenitis
How does Lymphatic Filariasis present?
Most cases are asymptomatic
Filarial Fever (occurs when adult worms are dying):
- Acute lymphadentitis
- Fever
- Lymphoedema
- Pulmonary eosinophilia (microfilariae in the blood tend to hang out in the pulmonary vasculature)
How do you diagnose LF?
Lymph Node Aspirate and serum microscopy
(Periodic samples required)
VEGF (not used clinically, but in studies has been shown as a good way of determining the extent of lymphatic involvement
Rapid Antigen Diagnostic test (only works for W. Bancrofti)
How do you manage lymphatic filariasis?
DEC (6mg/kg for 12/7)
+ Ivermectin 150mcg/kg
+ Albendazole 400mcg
+ Doxycyline 200mg/d for 6 weeks
What part of the lifecycle does DEC target?
Marco and Microfilariae
What part of the lifecycle does Ivermectin treat?
Microfilariae
If you cannot use DEC due to concurrent Onchocerciasis infection, how does your management change?
Doxycycline + Ivermectin + Albendazole
Ivermectin needs to be repeated for at least 10 years as it does not target adult worms
There has been lots of work in recent years to try and eliminate LF. What measures are recommended?
Vector Control
MDA
MMDP (morbidity management and disability prevention)
What WHO programme is focused on Lymphatic Filariasis?
GPELF: Global program for elimination of Lymphatic Filariasis
What is the recommended MDA in:
- Areas with LF with no risk of Onchocerciasis or Loiasis
Annual:
DEC (6mg/kg stat) + Albendazole (400mg stat)
What is the recommended MDA in:
- Areas with LF and Onchocerciasis
*** DEC cannot be used in Onchocerciasis, as causes rapid macrofilarial death and inflammatory response –> Blindness
SO
Ivermectin + Albendazole Annually
What is the recommended MDA in areas of Lymphatic Filariasis and Loiasis?
Albendazole
**Rapid macrofilarial death from DEC can be harmful in Loiasis
**Ivermectin is assocaited with meningoencephalitis and cannot be used
What is onchocerciasis?
River Blindness
What is the epidemiology of Onchocerciasis
- River breeding sites
- M > F (fishermen)
- West and central africa
What is the parasite in Onchocerciasis?
Onchocerca Volvulus
What is the vector in Onchocerciasis?
Black Fly (Simulium spp)
How big can adult female onchocerca be?
up to 80cm thats bloody mental
What bacteria co-infects onchocerca volvulus and acts commensally to make its life cycle more efficient
Wolbachia
What is the pathophysiology of Onchocerciasis?
disease symptoms occur when there is macrofilarial death –> large inflammatory response. Macrofilarial death is what leads to eye blindness
What is the lifecycle of Onchocerca Volvulus
L3 Larva injected by black fly –> enters in subcutaenous tissue –> released microfilariae –> re-ingested by black fly at further feed
How long can onchocerca worms live for?
12-18 months
How does Onchocerciasis present?
Skin changes –> Leopard skin, Lizard Skin, Pruritis, inflammation and ‘troublesome itch’
Punctate and sclerosing ketatitis
Sowda
Hanging Groin
Nodding Syndrome (epilepsy)
Hypopituitary disease
How do you diagnose Onchocerciasis?
Skin Snip Biopsy
DEC Patch Test (Maziotti sign)
Eosinophilia (all filarials)
?How do you manage Onchocerciasis
Ivermectin +/- Doxycycline
Which medications do you have to avoid in Onchocerciasis to prevent blindness as a result of filarial death?
DEC and Albendazole
How do you prevent Onchocerciasis?
Vector Control
MDA
Test and Treat
What is Loiasis?
Eye worm
What is the epidemiology of Loiasis?
DRC, Congo, Gabon
rainforests
What is the parasite in Loiasis?
Loa Loa
What is the vector in Loa Loa
Deer tick (Chrysops)
How does Eye worm present?
Soft tissue inflammation
Eye worm
Meningoencephalitis (rare)
**people used to think it was harmless but no we think it probably causes a lot of inflammatory changes
How do you diagnose Loa Loa?
Direct visualisation
Microscopy of Blood/CSF/ Urine/Sputum
*** Quantitative Blood Smears are reqiured to determine how to treat
How do you manage Loa Loa?
> 30000 worms - Albendazole
8000 - 30000 - Albendazole + Ivermectin
2000-8000 - Ivermectin
<2000 - DEC
**DEC is the ultimate treatment you need to give to get rid of Loiasis
What are calabar swellings?
Transient swellings under the skin associated with Loa Loa infection
What is the incubation of Loa Loa?
5 months (minimum)
How does WHO recommend you diagnose Onchocerciasis?
Skin Snip
Eye Slit Lamp
Serology: IgG4, OvAg (no other serology is good enough)
How should you treat onchocerciasis monoinfection?
For individual treatment, ivermectin is provided as a single dose of 150 μg/kg PO.
±6/52 doxycycline
Treatment should be repeated in 3- to 6-month intervals for 10-15 years
How can you diagnose Loa Loa rapidly in areas with lots of Onchocerciasis?
Mobile LoaScope
For regions co-endemic of onchocerciasis and L. loa, a mobile phone-based, point-of-care microscopy tool – the LoaScope – has proven helpful to easily identify patients with high parasitaemia of L. loa and to exempt them from mass treatment with ivermectin. This technology has increased the acceptance of ivermectin MDA for onchocerciasis and lymphatic filariasis in L. loa co-endemic areas.
