Native to south America but now widely distributed around the world, Bidens pilosa (commonly known as cobbler’s pegs, or blackjack)is an upright perennial plant with bright green leaves which grows up to around 2 metres tall. It has 3-5 tapered oval leaflets with serrated margins, and has numerous small yellow flowers which become dark, brown or black slender seeds.   The names blackjack and cobbler’s pegs both relate to these seeds (‘jack’ meaning thorn or needle, and the seed shape resembling the nails or wooden pegs traditionally used by cobblers to repair shoe soles). Other names it is also known by are Spanish needles and devil’s needles⁽¹⁾.

Closely related species include Bidens frondosa (beggar’s tick) and Bidens tripartita (swamp beggar’s tick), which prefers wet farmland and wetlands.  All three species have become naturalised in Aotearoa New Zealand (Bidens frondosa since at least 1907), and seem to have extended their habitats here in recent years⁽²⁾.  Bidens pilosa is known as a noxious weed, and is now naturalised in more than sixty countries in North and South America, Europe, Africa, Asia, Australia and New Zealand⁽³⁾.

A number of clever mechanisms help Bidens pilosa facilitate this invasiveness ability. Its black slender seeds can disperse by wind and water, and their barbed ends allow them to catch in bird feathers, animal fur or human clothes. Seeds can also germinate at different times of the year, and remain viable for up to 6 years⁽⁴⁾. It is an easily established and rapidly growing plant, particularly in areas of high soil moisture and sun, and in areas of disturbed ground. These characteristics all lend themselves to the changing weather patterns and human activities in Aotearoa NZ, and many other countries.

The phytochemistry of Bidens consists of more than 200 compounds including polyacetylenes, flavonoids, terpenoids, phenylpropanoids, essential oil and other compounds. Some of these have a defense function against natural enemies, and can influence the growth of other surrounding organisms (allelopathy)⁽⁴⁾. Many also contribute to its antimicrobial, anti-inflammatory, immunomodulatory and antioxidant activities⁽¹⁾.

As with many invasive plants or weeds, Bidens pilosa has several useful medicinal properties, and can be usefully applied for a range of health conditions. Traditional applications include for the treatment of wounds, diarrhoea, dysentery and bacterial infections of the gastrointestinal tract, as well as inflammatory conditions and respiratory infections^(5-7).

In some countries including South Africa and other sub-Saharan African countries, it is also being increasingly regarded and promoted as a healthy leafy green vegetable. Recent studies have reported comparable antioxidant and other nutritive benefits to spinach, and a good content of vitamin C, flavonoids and other healthy phenolic compounds^(8-10).

Antimicrobial

Bidens is a good antimicrobial, with a fairly broad spectrum antibacterial activity including against pathogens such as Escherichia coli (E. coli), Enterococcus faecalis, Bacillus cereus and Bacillus subtilis, Klebsiella pneumoniae and Staphylococcus aureus ^(11-14). It is therefore not surprising, that one of its widely used traditional applications in Colombia, Brazil and other south American as well as in several Asian and African countries, is to treat waterborne infections causing diarrhoea and dysentery^{(5, 16)}.

Waterborne infectious diseases such as cholera, typhoid fever, E coli and giardia being major problems in poor and increasingly in many developed countries, as a consequence of poor public sanitation systems, over-burdened waste water management facilities, flooding and other human related pressures, yet access to medical care and antibiotics can be limited. Plants which can help us manage these nasty infections, can therefore be valuable.

Leaf extracts of Bidens have also been shown to inhibit the formation of biofilm and the growth of antibiotic resistant Klebsiella pneumoniae carbapenemase-producing bacteria⁽¹³⁾. This is a serious infection usually transmitted through person-to-person contact or contaminated medical devices, with drug-resistant or poorly treated infections causing more than 200,000 deaths each year⁽¹⁴⁾.

Bidens is also used traditionally in some cultures for the treatment of urinary tract infections (UTI’s). A Brazilian study which tested activities of aqueous extracts of Bidens pilosa, Bidens sulphurea, and Tanacetum vulgare (tansy) against cultures of several bacterial strains isolated from the urine of menopausal women experiencing recurrent UTI’s, found Bidens pilosa to be the most active against E. coli ⁽¹⁵⁾. Incorporation of tea infusions or decoctions of this common weed into the management protocol of UTI’s, therefore has merit.

Anti-parasitical

Bidens pilosa is also among several plants used by indigenous communities in south Brazil and by traditional healers in Uganda and other African countries to treat malaria. This mosquito-borne disease has a huge human and economic cost, and with resistance to drug treatments being a major problem, interest is growing in plants traditionally used to treat malaria and other parasitical illnesses. 

Ethanolic extracts of the roots of Bidens pilosa have been shown by Brazilian workers to reduce parasite levels and mortality in mice^{(17, 18)}, with plants collected from the wild being more active than cultivated ones against chloroquine and fefloquine resistant falciparum isolates (Andrade-Neto). Researchers in both Ghana and Cameroon have also recently reported similar useful outcomes and improved haematological parameters in mice with malaria, using extracts made from the leaves and twigs^{(19, 20)}. 

Potential applications in the treatment of Toxoplasmosis (Toxoplasma gondii infectionhave also been reported from both in vitro and in vivo studies recently⁽²¹⁾. This parasite can cause cause abortions or congenital infection for many different domestic animals as well as humans, and can have severe consequences for immunocompromised patients. While drug treatments exist, these can have a relatively high degree of toxicity.

Poultry and pig industry benefits

Potential applications for Bidens pilosa to help with infection and protozoal control in poultry farming, have been revealed by recent research.

Avian coccidiosis is a common and highly contagious intestinal disease within the poultry industry, caused by organisms within the genus Eimeria. It is a tiny parasitic organism that can cause pain, weight loss and death if left untreated, especially in young chicks.  While antiparasitic drugs are effective, resistance can be a problem, and edible plants are re-emerging as an alternative strategy to combat this disease⁽²²⁾.

Several studies have reported improved health in chickens with coccidiosis, when their feed was supplemented with Bidens pilosa^(23-26).  Protective effects were reported at an organic chicken farm in China, after feed supplementation at a dose of 0.025% or more of Bidens pilosa for 56 days⁽²⁶⁾. Another study found that even a three day treatment with Bidens pilosa was shown to suppress Eimeria tenella as evidenced by a reduction in mortality rate, oocyst excretion and gut pathological severity. Oocysts of the parasite were not directly killed by Bidens pilosa, but the plant suppressed oocyst sporulation, sporozoite invasion, and schizonts in its life cycle. These effects correlated with modulation of gut bacteria ⁽²⁵⁾. Elevated body weight gain, lowered feed conversion ratio and chick performance, were significantly improved as a result of Bidens supplementation^{(23, 24)}.In addition to these effects on the parasite itself, Bidens boosted T cell-mediated immunity⁽²³⁾.

Vietnamese researchers have also reported several beneficial outcomes through incorporation of Bidens pilosa into the diet of growing pigs⁽²⁷⁾. Supplementation with a powdered mix of 60% Bidens pilosa with four other plants had no impact on the final body weight or feed conversion ratio of 10 week old pigs over a 7 week period, but it reduced serum cholesterol, LDL and urea concentrations, with no adverse effect on performance or nutrient digestibility.

Other uses

Research supports additional applications for Bidens pilosa in various other common human health conditions. These include type 2 diabetes mellitus, amyotropic lateral sclerosis, neuropathic pain, liver conditions and certain forms of cancer. These will be discussed in my next blog.

Summary

Increasing difficulties are being incurred by populations and communities in many parts of the world to afford or access drug medicines, and food as well as medicine security is being threatened by changing climates and geopolitical events. Against this background, locally available plants are becoming more important. Traditional knowledge shows us how plants play an important role as both foods, medicines or preventatives for a range of human and animal health conditions, and should be brought more to the fore, of research funding strategies and programmes.

Bidens pilosa and other Bidens species, seem to be under-regarded and under-utilised as both foods and medicines, and yet they are becoming increasingly invasive in many countries including Aotearoa New Zealand.  

In recent years I’ve paid more attention to this plant, gathering and using it successfully as a topical application to minor wounds and grazes and post-surgical skin lesions. Its combination of antimicrobial, anti-inflammatory and astringent properties make it ideal to support minor wound management. It can also be useful when taken in large doses as an infusion or tincture, as part of the prophylaxis of management of  UTI’s.

Furthermore, several potential applications for animal health and husbandry, are being supported by new and emerging evidence in recent years. Parasitical conditions such as eimeriosis in poultry farms can have a large impact on animal health and productivity, and parasites whose hosts include sheep, cattle, pigs and other farmed animals, can also have a huge toll. Further research into outcomes following incorporation of this common invasive plant into the feeds and supplements used in our animal farming industries, is therefore justified.

References:

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2. NZ Plant Conservation Network, https://www.nzpcn.org.nz/flora/species/bidens-pilosa/
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