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Epidemic dropsy is a sometimes fatal condition seen in India, Nepal, Fiji, South Africa, Mauritius and rarely elsewhere. It is caused by accidental or deliberate contamination of cooking oil (esp. mustard oil, rape seed oil) by toxic argemone oil (Argemone mexicana; "prickly poppy"; fam. Papaveraceae). Do not confuse the name argemone with agrimony, which belongs to the Roseceae or Rose Family. Toxic argemone oil should not be confused with the so-called "spanish toxic oil syndrome" of 1981 (myalgia, eosinophilia) or with triorthocresyl phosphate poisoning (jake paralysis, ginger paralysis) which resulted from adulteration of cooking oil with lubricating oil.
The main toxic component in argemone oil is a glycoside, sanguinarine. The name sanguinarine refers to bloodroot, Sanguinaria canadensis, a perennial herb, which contains the same alkaloid. Other toxic alkaloids which are present are dihydrosanguinarine, berberine, protopine, optisine, chelerytherine and others. Sanguinarine is a benzophenanthrine alkaloid and is being studied as a potentially antineoplastic agent (induction of cell death pathways). It is a cumulative toxin. Sanguinarine can be absorbed through the skin and contaminated oil used for massage can lead to sporadic cases. The toxin interferes with carbohydrate metabolism.
The Mexican poppy - Argemone mexicana- originated in the New World, but has now become a common weed in India. The specific name mexicana refers to it native place Mexico. The generic name argemone comes from the Greek argema, meaning cataract. Interestingly, the juice of this plant was once very popular in the treatment of cataract and hence the name. In India, the plant occurs as a local weed in the cold season, exclusively in low rainfall regions at elevation from sea level to 2,500 m. The plant, although from a semi-tropical climate, is remarkably well adapted to colder and drier conditions. It is weedy in disturbed areas in waste places, roadsides, old fields, pastures, barnyards and gardens.
It is an annual herb with bright yellow sap. The spiny leaves are thistlelike. The showy flowers have 4-6, bright yellow petals (there are also white forms) and many stamens. Seeds are blackish-brown, round and netted and resemble those of mustard (Brassica nigra). The seeds can be pressed to obtain oil. In India, the oil of argemone is known as katkar oil and it has several legitimate uses. It is used for lighting lamps, as it is very cheap. Although the seeds of argemone look very much like those of mustard seeds, there are some important differences between the two. If the seeds are placed between two fingers and rubbed, the argemone seeds are found to have spiny edges. Mustard seeds do not have such spiny edges. Furthermore the seeds of mustard are heavier having a specific gravity of 1.3 as compared to 1.08 of argemone. The seeds of mustard will sink in saline water of appropriate specific gravity (say 1.2), while those of argemone will float.
Those defending people accused of intentional adulteration (mainly merchants and retailers of mustard oil) often point to the fact that the two plants often grow together and ripe at the same time, so during harvesting, there is an inadvertent mixing of the two seeds. This argument appears fallacious for several reasons. Argemone grows mostly on fallow land and mustard has a canopy that does not let anything grow under it. In India -where most cases occur- mustard ripens in March and argemone in May. By May mustard has already been harvested, so adulteration is usually intentional.
There were repeated dropsy epidemics in India, with many cases in 1934 (>2000 cases) and in 1998. In 1998 epidemic dropsy claimed 52 lives and caused 2500 more to be hospitalised. This prompted the Indian government to temporary ban the use of all mustard oil. New cases appeared in the summer of 2003. Since epidemic dropsy cannot be produced in animals, most studies on argemone oil toxicity have been done on human cases.
Epidemic dropsy is characterized by nausea and diarrhoea, followed by pitting oedema of the extremities, extensive dilatation of vessels of the skin, subcutaneous tissues (incl. fat) and uveal tract, cardiac insufficiency and liver abnormalities, including painless hepatomegaly. Concurrent glaucoma and retinal haemorrhages can occur, but it is not clear how strong this association is. The heart shows no degenerative changes, but cardiac muscle fibres will be separated by dilated capillaries. Tachycardia, irregular heart beat and low blood pressure are common. There tends to be right heart failure. Although the function of the left ventricle seems to be preserved in this condition, there is pulmonary oedema, due to a capillary leak syndrome. In general there is a slight fever. The legs can be painful. There can be a diffuse or patchy erythema as well as nodular skin lesions (sarcoidosis-like) and telangiectases. Clinical cases can resemble beriberi, but peripheral neuritis is absent. Serum albumin and calcium are reduced due to leakage of protein-rich fluid into the tissues. There is a relative hypovolemia. Although one would expect haemoconcentration, anaemia and moderate azotemia occur, although the mechanism is not clear
Sporadic cases occur but are easily missed because of low clinical suspicion by the treating doctor. The diagnosis is clinical and is supported by the detection of sanguinarine in urine (HPLC, thin layer chromatography). There is no known antidote. Treatment will be supportive. Calcium gluconate infusions and antioxydantia such as vitamin C and E will be administered, although the efficacy is unclear. Treatment for cardiac decompensation will be started. Most people will recover in 2-3 weeks (sometimes up to 6 weeks), but lethal cases occur.
There is a simple test to detect argemone oil in edible oil. One should take about 2 ml of oil in a test tube, add 2 ml of concentrated HNO3, heat and observe the colour. A red layer at the lower level in the test tube shows the presence of argemone oil. If positive, further chemical analysis by chromatography (HPLC or thin layer) will be performed to confirm the presence of the toxin. The toxicity of contaminated oil can be eliminated by heating to 240°C for 15 minutes.
