Comparison of the numbers of artemisia plants required to meet the world demand for artemisia a) to provide ACT (Artemisinin Combination Therapies) drugs and b) to provide artemisia tea
Assumption 1: We base the calculation on the experience of growing and harvesting Artemisia annua of a colleague in Brazil: The plants were spaced at intervals of one metre. This corresponds to 10,000 plants per hectare. Under optimal conditions, that gave 45 tons of fresh plants. Of those 45 tons, 15 tons were stems, and a further 27 tons of water were lost in drying. Thus the product was 3 tons of dried leaves per hectare or 300 g per plant. (see Note1)
Assumption 2: 400 million adult treatments for malaria are required per year.
Assumption 3: The leaves have an artemisinin content of 0.7% (see Note 2). Then 3 tons of dried leaves contain about 21 kg artemisinin, or one plant provides 2.1 g of artemisinin.
a) For ACT drugs:
Assumption 4: Each pharmaceutical treatment for malaria requires 3 grams of artemisinin (see Note 3). The yield of artemisinin from one hectare is therefore enough for 7000 treatments. Thus one plant yields only 0.7 treatments.
400 million treatments /0.7 = 571 million plants. At 10,000 plants per hectare (monoculture, see Note 4), 57,100 hectares are required, and 171,300 tons of dried leaves.
b) For artemisia tea: Since one treatment requires 35 grams of dried leaves, one hectare provides enough leaves for more than 85,000 treaments. Thus one plant yields between 8 and 9 treatments.
400 million treatments /8 = 50 million plants. At 10,000 plants per hectare (monoculture) 5000 hectares are required, and 15,000 tons of dried leaves.
If this calculation is correct and the assmptions are reasonable, more than 10 times as many Artemisia annua plants are required to treat malaria patients with drugs containing extracted artemisinin as compared with artemisia tea.
1. ICRAF have reported a yield of 200 g of dried leaves per plant (more). Using this figure, the above requirements for the world supply shoud be increased by 50%.
2. The concentrtion of artemisinin in the leaves of Artemisia annua fluctuates between 0.5 and 1.2%, but is more commonly at the lower end of this scale. For the pharmaceutical industry this percentage is critical, but for tea it is relativly unimportant.
3. The dosage recommended by the World Health Organisation is as fallows:
Monotherapy: 20 mg/kg in divided loading dose on the first day, fallowed by 10 mg/kg once a day for 6 days. For a 60 kg adult, this works out as 1200 mg on the first day, fallowed by 600 mg daily on subsequent days, i.e. a total of 4800 mg or 4.8 g.
Combination therapy: 20 mg/kg in a divided loanding dose on the first day, fallowed by 10 mg/kg once a day for two more days plus mefloquine (15-25 mg of base per kg) as a single or split dose on the second and/or third day. For a 60 kg adult, this works out as 1200 mg on the first day, and 600 mg for two or more days, giving a total of least 2400 mg or 2.8 g.
4. Anamed recommends a mixed rather than a monoculture in order to minimize loss through plant disease… Therefore the plants should be spread over a larger area. In fact anamed recommends small scale village cultivation of Artemisia annua, so that the supply is close to the need.