|Clinical Guidelines and Treatment Manual (MSF, 1993, 319 p.)|
|Chapter 6 - Parasitic diseases|
Group of conditions caused by infection with various nematodes, the most common being Wuchereria bancrofti, Brugia malayi, Onchocerca volvulus, Loa loa and Dracunculus medinensis. Adult forms of both sexes live and reproduce in human lymphatics, in the skin or in deep tissues. Their larvae, microfilariae, reach the blood or skin and are thus the infective form for biting vectors as well as being the form upon which diagnosis is based.
Transmission is by vector: mosquitoes for lymphatic filariasis (Bancroftian and Malayan), blackflies for onchocerciasis, Chrysops flies for loiasis and tiny crustaceans (Cyclops) for dracunculiasis (Guinea worm).
Clinical features and diagnosis
- Inflammatory symptoms: acetylsalicylic acid (PO): 3 g/d divided in 3 doses or indomethacin (PO): 75 mg/d divided in 3 doses
- If allergic symptoms develop (e.g. urticaria, pruritis) promethazine (PO): 75-100 mg/d divided in 3-4 doses; child: 1 mg/kg/d divided in 3 doses or chlorpheniramine(PO):12 mg/d divided in 3 doses
LOIASIS AND LYMPHATIC FILARIASIS
The main drug used is diethylcarbamazine, often abbreviated to DEC. It is essentially a microfilariacide and may not kill all adult worms. Therapy with DEC should always be supervised as the drug is often poorly tolerated (allergic reactions). Dosages should start low and be increased progressively. DEC is contraindicated during pregnancy. Usual presentation is in 50 mg tablets.
Adult: commence with 25 mg/d divided in 2 doses (= 1/8 tab x 2/d). Increase progressively by doubling the dose each day until the 5th day, dose is 200 mg x 2/d=2 tab x 2/d) x 10 days.
Child: 3 mg/kg x 2/d x 10 days, to be reached progressively over 5 days.
A second therapeutical course can be repeated after 10 days.
In this infection diethylcarbamazine can cause a fatal
encephalitis or allergic shock. Much care is needed. Reinfection after treatment
is very common, so if symptoms are mild, it may be better to withold therapy.
Dosage can be adjusted to extent of infestation
(beyond 50,000 microfilaria/ml blood: +++ caution).
Where treatment considered essential because of severity of infection: diethylcarbamazine
Adult: 3 mg x 2/d (= 1/32 tab x 2/d) the 1st day increasing progressively till in seven days 200 mg x 2/day (= 2 tab x 2/day) x 21 days.
Child: begin progressively to reach in seven days 3 mg/kg x 2/d x 21 days.
Always give antihistamines in association.
If promethazine does not control reactions to treatment, treat with prednisone (or prednisolone): 15-30 mg/d in a single dose x 3-5 days, then decrease progressively. If necessary, dexamethasone IV or IM: 4-20 mg / kg.
Note: where Loiasis is endemic (West Africa), all treatment with diethylcarbamazine, should commence with 3 mg/kg x 2 days (protocole for Loiasis) whatever form of filaria is being treated. This is to avoid the sometimes fatal complications of inopportune treatment where there is also unrecognised associated loiasis.
The treatment of choice is ivermectin (Mectizar), microfilaricide, 6 mg tablets.
The recommended long term management of communities is one dose every 6 months the first year, then a single dose annually.
Contraindications: child < 5 years, pregnant women, women in their first week of breast feeding.
Side efects are due to lysis of microfilaria (allergic manifestations, pain, fever) and respond well to antihistamines and acetyl salicylic acid. Rarely orthostatic hypotension occurs but responds to injected cofficosteroids (single dose or 1-2 days).
There is no problem with associated filarias even Loiasis.
If ivermectin not available: diethylcarbamazine in dosage for lymphatic filariosis.
TREATMENT OF MACROFILARICIDES
This should be abandonned as too dangerous.
- See table.
- Individual chemoprophylaxis for Loiasis is possible, 100 mg diethylcarbamazine PO/week in a single dose (or 2 doses of 50 mg/week). It is indicated for non residents going to an endemic zone provided, they are not already infected with Loiasis (risk of serious reactions).