Zoopharmacognosy: Self-Medication in Animals

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It is a behaviour in which animals apparently medicate themselves by selecting and ingesting or topically applying plants, soil, insects and psychoactive drugs to prevent or reduce the harmful effects of pathogens and toxins. It is also described as use of plant’s secondary compounds and other non-nutrient factors by animals to control or treat disease.

History:

The term “Zoopharmacognosy” was first coined by Professor Dr. Eloy Rodriguez (Biochemist), Cornell University, USA. However, the idea was proposed for the 1st time by Daniel H. Janzen, in the year 1978 and he compiled all the anecdotal accounts of possible self-medication in animals.

By nature, animals are clever and may selectively forage on leaves, stems, roots and algae to maintain their health. In the last few decades scientists have discovered that these parts of plants have medicinal properties that can cure infections and various diseases. The discovery of coffee was based on chance observation by a shepherd. He observed that the goat get stimulated after consuming the berries of wild coffee plants in highlands of Ethopia. The observation of consumption of plants “chota chand” by the mongooses, in foothills of Himalayas before fighting with cobras has led to the discovery of potent antidote of snake-bite, present in their roots.

Two types of self-medication in animals exist, one is Preventive medication which is prevention of diseases or parasitic infestation and other is Therapeutic medication which is treatment or cure or disease by self-medication. When wild life (animals) gets hurt, they rush toward berberis plant, which is multi potent medicinal plant and they either eat berries or suck leaves or barks of berberis plant which is uncommon routinely.

Types of zoopharmacognosy

  • Dirt medicine or Geophagy/Dirt eating:

The dirt/soil eating as clay or chalk has been observed in many animals (including herbivores), bats, birds, primates and even in humans. Clay licking behaviour in South American parrots reveals that clay contains kaolin, smectite and mica. The preferred soil in kaolinite results in surpassing or approach pure bentonite in their capacity to bird’s quinine and tannic acid. South Eastern Peru soil contains calcium and sodium so avian geophagy occurred on it. Sodium helps in detoxification process in birds. Japanese macaques have been observed to ingest 2.9797g/individual/day of soil due to its buffer activity. Yellow stone grizzly bears ingest clay/soil having high concentration of magnesium, potassium and sulphur presenting anti-diarrhoeal property.         

  • Anting or Insect medicine

Many birds and animals exposed themselves to the insects particularly ants. Rubing crushed ants directly (Active anting). Babblers and weavers undergo active anting. Or let them crawl in plumage by lying on ants nests (Passive anting). European jay, Crows and Waxbills, Squirrels and Monkeys are the mammals that partake in passive anting. It helps in feather maintenance and soothing skin by secreting formic acid, miticides, insecticides, bactericides, fungicides and supplement for birds preen oil. Sometimes birds expose themselves to millipedes or lime fruit plant. More than 200 song birds’ species partake in anting process.

  • External plant medication or Topical application of plants as medicine

The masticated plant materials as leaves and the some insects have been rubbed on body by primates with sole purpose to repel or get rid of ectoparasites. As North American brown bears mix their saliva with Osha roots (bear roots: contain 105 active chemicals as coumarins; a fly repellent, for stomachic and infections etc.) to make a paste for fur rubbing.  Highly toxic materials of millipedes have been rubbed by the Venezuelian Capuchin monkeys on their fur during humid season to avoid insects attack or to treat skin irritation. Anti-microbial foliage of birds in the nests, presenting volatile compounds which act as fly repellent and also inhibit bacterial growth.

  • Internal plant medication

The folivorous (leaf eating animals) like Hoatzin have specialized bacteria in their crop to breakdown undigestible leafy plants. So these animals use the leaves of plants as treatment materials. Cats when swallow any indigestible compound like hairs they consume grass to get rid of it. The bacteria present in bird’s gut also neutralize toxic secondary compounds present in the consumed plants. The chimpanzees use Aspilia leaves (have antiparasitic, antibacterial and antineoplastic properties) un-chewed rolled in oral cavity but and engulfed to treat upset stomach and also in rainy season as antiparasitic material. Bitter pith (V. amygdalina) chewing and leaf swallowing helps the chimpanzees to treat nematode infestation by self-medication. After chewing bitter pith recovery was evident after 20-24hours. EPG of O. stephanostomum was found to drop from 130 to 15 in 20hours. African great Apes utilize plants secondary compounds and non-nutritional substances to control intestinal parasites and to get relief from GIT upsets. Certain varieties of baboons in Ethopia consume leaves and fruits of plant Balanites aegyptica for control of schistosomiasis. Phytochemicals (secondary metabolites) have also been consumed by animals as antiparasitic medication by various animals.

Plants as stimulants

Chachma baboons in South Africa consume small amounts of leaves of specific plants grouped as Euphories for their stimulant property. Plants of family Solanaceae and Euphorbiaceae are well known for stimulant property. A powerful stimulant Tabernanthe iboga has several indole alkaloids and it is also used as aphrodisiac in many religious societies of Gabon. In 1968 widespread use reported by people of Gorillas, porcupine & bush pig going into wild frenzies after digging up and ingestion of the root this plant was reported.

Reproductive remedies

Females of Muriqui monkeys found in Brazil get themselves prepared before breeding season. This is achieved by consuming the leaves from a plant Apuleia leiocarpa (JF Macbr) and Platypodium alegans vog., and the fruits of Enterobium contortisiliquim Morong. The former two plants contain isoflavonoids, that has properties similar to estrogen and thus decrease fertility and latter plant carries a compound known as stigmasterol which is precursor of progesterone that increases the chance of conception. African elephant (Loxodonta Africana) consumes the leaves of tree Branginaceae to induce labor. Pregnant lemurs eat tamarind and barks to boost milk production.

How this behaviour is acquired by next generation

Infants imitate their mothers when they feed on specific medicinal plants when they are ill. Ill animals consume certain items other than their natural food, if feel relieved they will then utilize that item in future. Our early ancestors were always taking medicinal plants like Aspilia and Berberis. That’s why today we can eat medicinal plants, because our ancestor’s physiology has adapted to eating these plants. The research pertaining to animal’s self-medication also applies to human being or vice versa. Co-evolution of host and parasite has resulted in biological methods to decrease the parasitic infection due to adaptations to physiological immune responses.

Conclusive remarks

This intelligent behaviour has intrigued scientists from various disciplines including animal and plant biology, chemistry, medicine and environmental science. That’s why the discovery of many medicinal substances has occurred by the use of these compounds or plants by the animals. Zoopharmocognosy will throw light on new solutions of our ever expanding medicinal needs.

This article is collectively authored by Mubashrah Mahmood and Iqra Shehzadi University of Agriculture, Faisalabad.


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