Onchocerciasis-Medicines For Treatment,Dosage.
Onchocerciasis is also known as river blindness. The best medicine for treating river blindness is ivermectin. This medicine kills the baby worms slowly and does not cause the dangerous reaction of other treatment. If ivermectin is not available, an experienced health worker can give diethylcarbamazine first and then also suramin.
This disease is a kind of filariasis, common in many parts of Africa. The infection is caused by tiny worms that are carried from person to person by small, hump-backed flies or gnats known as black flies (simulids) which breed in fast running water.
- Several months after black fly bites and the worms enter the body, lumps begin to form under the skin, usually around the hips or chest wall, occasionally on the head and often in deeper places where they cannot be felt. These lumps which are painless and 2 to 3 cm in size contain the full grown worms in pairs, and they produce baby worms which spread extensively in the skin and deeper tissues. Even before these lumps can be felt, there are four early symptoms to ask about or look for.
- Itching on the trunk or wherever the baby worms are spreading.
- Pains in the neck, shoulder or hip-joints, or general pains all over the body. Many
- patients first come for help because of the backache and rheumatic pains.
- Enlargement of the lymph nodes in one or both sides of the groin.
- Thickening of the skin on the back or the abdominal wall with prominent pores like the skin of an orange. To view this, the skin must be viewed with the light coming from one side.
If at this stage, the person can be taken for medical help, a ‘skin snip’ taken from over the hip can be put under a microscope, the baby worms (micro-filariae) will be seen and treatment can be started.
If a young farmer has recurring backache to the point that he or she cannot work, have him or her tested for onchocerciasis.
If the condition is neglected, more severe effects on the skin and on the eyes may occur.
- The skin becomes wrinkled gradually like the skin of an old man or woman. White spots and patches may appear on the shin, often called ‘leopard skin’. In occasional cases, there is a generalized dry dermatitis (scaly rough skin) of the lower limbs and buttocks, often called ‘craw-craw’ or ‘sowda’.
- The baby worms can invade the eyes especially when there are nodules on the head. This causes eye irritation and eventually blindness. For this reason onchocerciasis is usually called ‘river blindness’. However, in the wet tropics, eye problems only affect 1 person out of every 20 persons. In drier areas, they may be more common.
The worms are injected into a person when an infected fly bites him or her.
Early treatment can prevent blindness. This should begin at the stage of backache and enlarged glands in the groin. One should not wait for eye symptoms to appear. Treatment then is more difficult.
- Ivermectin is the safest medicine and one dose of tablets lasts for 6 to 12 months. It may be available free through the local health department.
- Diethylcarbamazine (DEC) is still widely used to kill the baby worms but has to be given for 1 to 3 weeks, with several repeat courses every 2 or 3 months. Reaction with itching, fever, more aches and pains can be severe at the beginning. There has to be special care if the eyes are affected, so an experience health worker should supervise treatment.
- Injections of suramin are used to kill the adult worms.
- Early surgical removal of the lumps lowers the number of worms.
- Phenobarbital may be used to help sleep during the first few days of treatment.
- Avoid sleeping outside the house, especially in the daytime which is when the flies usually bites.
- Cooperate with programmes for the control of black flies. This may require clearing vegetation from the banks of fast-running streams.
NOTE : Early treatment prevents blindness and also helps limit the spread of the disease.
MEDICINES FOR ONCHOCERCIASIS
This medicine is also known as Mectizan, it comes in 6 mg and 3 mg tablets. To determine the correct dose, if possible weigh the person first. Give one dose. Another dose is sometimes needed 6 months to 1 year later.
CAUTION : Do not give to children who weigh less than 15 kg or children who are under 5 years old and also to pregnant or breast feeding women or to persons with meningitis or other serious illness.
Dosage of ivermectin
Give one time
- Heavy adults over 64 kg : 2 tablets (12 mg)
- Average adults between 45 yo 63 kg : One and half tablets (9 mg)
- Light adults and youths between 26 to 44 kg : 1 tablet (6 mg)
- Children between 15 to 25 kg : half tablet (3 mg)
This is also known as Hetrazan, Banocide. It comes in 50 mg tablets. This drug kills the young worms quickly but not the adult worms. As the young worms die, they cause a marked (Mazzotti) reaction with fever, joint pains and much itching which is worse at night.
Dosage should therefore be low at first, then gradually increased. As the adult worms remain alive and produce more young worms, repeat courses have to be given. To help sleep at night during the reaction, phenobarbitol tablets may be needed.
If the eyes are also affected, DEC(diethylcarbamazine) should only be used under the supervision of an experienced health worker. Extra steroid tablets to protect the eyes may be needed.
Give twice a day for three weeks. In each dose:
- For adults : Start with 1 tablet (50 mg) and increase after each day or two to 2 tablets, then 3 tablets, then 4 tablets (200 mg). Keep on with 4 tablets morning and evening until 21 days is complete. The repeat course which may be needed when itching and joint pains return after 2 or 3 months; need only be 4 tablets (200 mg) twice daily for 5 days.
- Children between 8 to 14 years old : Half the dose
This is also known as Naphuride, Bayer 205, Antrypol, Germanin. Suramin is more effective than diethylcarbamazine in killing adult worms and should be used after treatment with diethylcarbamazine when reactions have nearly stopped.
Suramin sometimes poisons the kidneys. If swelling of the feet or other signs of urinary poisoning occur, stop using this medicine. Person with kidney problems should not use it.
Suramin must be given intravenously and should only be used with the assistance of an experienced health worker.
For adults, inject 1 gm of suramin in 10 ml of distilled water once a week for 5 to 7 weeks. Start with a small test dose of 200 mg. Treat allergic reactions with antihistamines.