23 Tissue Nematodes: Filariasis

Paul Pottinger 19/09/18

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We’re now onto the multicellular organisms!

They make disease through migration of worms through the tissues of definitive host.

THis is different to the intestinal nematodes, who make disease in the intestine.

There are male and remale nematodes

23.1 Lymphatic Filiarisis

Filaroidea

Filaria just means a thread

  • Wuchereria Bancrofti in Africa
  • Brugia malayi (asia)
  • Brugia timori (east timor)

They all share the general theme. Adults living in lympgatics, sc, and deep tissue.

23.2 Life Cycle

Small larval worms that live in mosquitoes, loads of mosquitoes can spread them (culex, mansonia, aedes, anopheles)

These larval worms eat bacteria in mosquito guts, wolbachia bacteria (a normal commensal in mosquitoes)

The mosquito takes a blood meal the larval worms disseminate throughout body, aiming for the lymphatic systems. Loads of proteins and sugars and lipids for the worms.

These adult worms forming are large. Like size of spaghetti large. They have a live birth!

These larval worms then need to aim for the blood stream. They can’t survive for long in blood, so they only come out at night nocturnal periodicity This chronic state of inflammation causes scarring in lymphatics, which then causes lymphoedema

This disease is an anthroponosis. the

23.3 Epidemiology

Not clear why some areas are infected and and why others arent

Around 90 million patients in Africa currently infected.

23.4 Vector

Culex is one vector

23.5 Presentation

23.5.1 Acute Adenolymphangitis

Soft and pitting oedema

Painful, red, warm swelling

Often scrotal involvement (probably just a gravity drainage thing)

23.5.2 Chronic

This is when adult worms are responsible for disease. This is relatively rare.

This forms woody oedema, pretty hard/irreversible.

Often gets secondary bacterial superinfection. This will cause more scarring and worsening

In the scrotum you can get lymphatics eroding into the ureters

So you can get unilateral (really more predominance of one leg over the other), persistent changes. Called “elephantiasis”

When you see a thing that looks like elephantiasis, think podoconiosis (non infectious, lymphatic changes)

23.5.3 Asymptomatic Microfiliariasis

You can make this diagnosis with ultrasound of scrotum

23.5.4 Tropical Pulmonary Eosinophilia

Microfilaria in the lungs cause this. It’s usually seen in men, usually men from southern india. But can be anywhere.

This is rare. Nocturnal cough, wheezing, fever, fatiuge. High peripheral eosinophilia.

Chest xray not specific

This can cause pulmonary fibrosis without treatment.

23.5.4.1 DDX

  • Loefflers Syndrome (but this is a very transient process, TPE is more chronic)
  • Asthma
  • Idiopathic hypereosinophilic syndrome
  • Allergic bronchopulmonary aspergillosis
  • Drug allergy

23.6 Pathology

You can see worms in dilated lymphatic channel on pathology (don’t though)

You can perform a lymphogram (don’t though), these show dilated tortuous channesl with calcifications.

The ureter can get connection of lymphatics. This can cause chyluria. This may worsen following fatty meals. There are very few things that can cause this (histoplasmosis, other stuff that causes distortion of pelvic anatomy, but really really think of lymphatic filiariasis)

23.7 Diagnosis

Nocturnal Blood Films - Same technique as with malaria. But you want to do this at night time! That’s when the parasites are out. If you’re a traveller going across timezones, it usually takes about 6 weeks to catch up with the new time zone.

Is it sheathed or not? Are there nuclei in the tail or not?

Blood films are first line

Antigen testing and serology are also both sensitive. Easy to say a microfilaria, but there it’s difficult to speciate.

23.7.1 POCUS Scrotum

For the Filarial Dance Sign!

23.8 Treatment

DEC - diethyl carbamazine

Relatively safe and well tolerated. Kills adult and MF

You can also consider killing off the wolbachia bacteria in the guts of the worms. With pretreatment of 4 weekly twice daily doxycycline. But v difficult w adherence. And concerns w antimicrobial stewardship

23.8.1 DEC Alternatives

Albendazole. V safe, v tolerated. But it kills adults, not MFs. So combine with Ivermectin that kills MF, not adults.

There are problems with this strategy though for when patients have other parasites.

23.8.2 Procedural

Hydrocele Drainage

Surgery

Nigerian Hydrocelectomies

23.8.3 Supportive care

Wash with soap and water twice daily

Care cuts/abrasions

Keep fingernails and toenails clean

Wear shoes

23.9 Prevention

  • Mosquito Control
  • Mass DEC administration? (Safe, well tolerated, contine for 5-6 years maybe can bring microfilaremia below levels necessary for infection to continue, success claimed in china, china put DEC in the salt and s. korea)

23.10 External Source

(A future free of LF)[http://filariasis.org]