Local knowledge regarding medicinal insectsMedicinal insects used

Our study revealed nineteen (19) medicinal insects used by traditional healers, showing very rich ethnomedicine knowledge in the two provinces of Burkina Faso. There are similarities with other studies carried out in the world generally, and in Africa specifically, where bees (Hymenoptera) and their products, but also beetles (Coleoptera) and cockroaches (Blattodea), were predominant in the list of the therapeutic species [11, 14, 18]. Thus, insect and insect-derived products provide ingredients that have been a staple in traditional medicine for centuries in many parts of the world. In fact, their immunological, antiviral, analgesic, antibacterial, anti-cancer, diuretic, anesthetic, antioxidant, anti-inflammatory, anti-rheumatic and immunomodulatory properties are well recognized [12, 27, 28]. The use of medicinal insects varied from one locality to another and also from one country to another. Then, the adult house cricket, Acheta domesticus (Gryllidae), is used for the treatment of deafness in Burkina Faso while in Latin American, it is used for the treatment of scabies, asthma, eczema, lithiasis, earache, oliguresis, rheumatism, urine retention, urinary incontinence and ophthalmological problems [29]. As for locus Schistocerca gregaria (Acrididae), it is used by the traditional healers in Burkina Faso to treat wound. This insect is known to have antiproliferative activity [30,31,32] The Blattodae, Periplaneta americana, is used by the traditional healers in Burkina Faso to treat ear pain, but the same species has been used to treat asthma, toothaches and bronchitis by the Amerindians of the Amazon [33]. It is also used for an asthma treatment in Latin American folk medicine [29]. This property to treat pain is probably due to the presence of molecules isolated from the brains of these insects known to be excellent antibiotics v[34]. The therapeutic practice to use blister beetle Lytta vesicatoria for the treatment of urinary retention has also been reported in other studies undertaken by Read et al. [35]. and Tsuneo et al. [36]. These common uses are probably certainly due to the presence of cantharidin, a compound with notable effects on the urogenital system of vertebrates. In the past, it was prescribed as a remarkable aphrodisiac, but now it is used to induce mating in some domestic animals and as a therapy for some disorders of the urinary tract [14]. Furthermore, a longhorned beetle (Cerambycidae), dung beetle (Scarabaeus laticollis), and 7-spotted ladybirds (Coccinella septempunctata) are used to treat, respectively, breast crack, pain on urination and wound. The larvae of Diptera Musca domestica are used to treat sickle cell anemia and male infertility, respectively, in the province of Houët. As for Lepidoptera, the larvae of Cirina butyrospermi are recognized to have tonic properties in the study areas, as also noted by Oudhia et al. [37]. Its larvae have an ability to regulate blood pressure in hypertension. The fact that insect species are being used for the same purpose by several communities might indicate their pharmacological effectiveness. The widespread use of insects throughout the world suggest that traditional knowledge on zootherapy is to be studied more seriously, in order to lead to the discovery of new sources of drugs [38].

Stage of development of medicinal insects’ use

Overall insects are used at different stages of development. However, in our study, the egg stage was not cited. Larvae, pupae and adults’ stage have nutritional and medicinal qualities [39]. These authors point out that in general, the protein content was found to be higher along with the more mature developmental stages. Honeybee larvae were used for the treatment of male impotence and for raising libido in men. These are usually consumed directly within the wax combs. The use of larvae for treating infertility is probably due to their high protein content of mature larvae (15.4% of fresh weight) [40]. For Musca domestica, larvae are used in treating male infertility whereas in Japan, it is used in treating snake bites and fever, gut and stomach problems and eye disorders [12].

Insect products used in therapy

The insect products cited in our study are the nests of termite and honey and wax of bee. However, other results suggest, in addition to the bee products mentioned above, propolis and royal jelly [41]. Honey is the most widely used as bee product in traditional medicine and its use varies by region. This could be explained by the variation in the composition of honey depending on the region. Indeed, the composition of honey and its content of mineral and organic constituents are strongly linked to foraged flowers [8]. In addition to these products known to medicinal insects, the study showed that insects can impact certain materials and give them therapeutic benefits. This transformation could come from the secretions of these insects. Indeed, insect secretions have been shown to have therapeutic properties as regarding secretions from larvae of Lucia sericata [42, 43]. The nests of termite Macrotermes spp. and Trinervitermes spp. are used to treat diarrhea, fractures and used for its toning effect and those of Nasutitermes spp. is used as an anti-inflammatory activity. Healing properties of termite mounds could be explained by the fact that they contain xyloglucan, a hemicellulose in the wall of dicotyledons that reduces the frequency and duration of diarrhea [44]. Undegraded sugars present in termite droppings could explain their use as plaster to immobilize fractured limbs [45]. Interestingly, Apis mellifera, Vespula vulgaris, Sceliphron sp belonging to Hymenoptera are listed among medicinal insects and their products are used to treat different diseases around the world. Thus, the nest of Sceliphron sp. is used to treat mumps. As to Apis mellifera, besides honey used to treat asthma, burn, constipation, difficulty breathing, voice extinction, general fatigue, insomnia, intestinal helminthiasis, bladder lithiasis, heart diseases, and hip pain, other bee products are highly prized as medicines. Pollen (collected by bees), larvae and pupae have medicinal properties, i.e., pollen is used for the treatment of bleeding gastric ulcer and chronic prostatitis [46,47,48]. Propolis, which is a resinous substance collected from the buds of some trees and flowers by bees to repair damage to their hives, is used in Eastern Europe as an antiseptic and an anti-inflammatory agent for the treatment of wounds and burns [49].

Correlations between medicinal insects and medicinal categories

Insects are used in the treatment of a wide variety of pathologies and symptoms. This broad spectrum of insect action could be understood if we consider the extreme variability of individuals of this class. Also, we can think of a great variability of the active molecules that can be contained in these different insects and products. PCA revealed a strong positive correlation between Cirina butyrospermi larvae and nutritional diseases. Indeed, shea caterpillars are very rich in protein (63%), but also in omega 3, iron, zinc, magnesium, phosphorus (5%) and vitamins A, D, E [50]. PCA has also shown that honey from bees is widely used in the treatment of gastroenterological pathologies. Indeed, it has been revealed that bee products can regulate digestive disorders (diarrhea, colitis, peptic ulcer) induced by the bacterium Helicobacter pylori [51]. Honey can be a complementary treatment for bacterial gastroenteritis in children [52]. This same PCA testified the use of Macrotermes sp. particularly its nest in the treatment of pathologies of rheumatology and gynecology. Other studies have also shown the implication of this insect's nest in the treatment of disorders related to human reproduction. Indeed, Zborowski [53]confirmed in his study that the queens of Macrotermes sp. were believed to have the power to treat female infertility and male impotence. This nest is also used against inflammatory diseases as it has been shown in Mahdi et al. [54].

Association between medicinal insects and plants

As for the association between insects and plants for the treatment of pathologies in the two study areas exhibits many variabilities. This fact could be explained by the different floristic knowledge of traditional healers in the different study areas. Here, plants (flowers, fruits, leaves, barks and roots) were added to insect and their products, either or adjuvant and therapeutic.