Extracts of ethnoveterinary plants used to control myasis caused by blowflies in animals are effective in several mechanisms and may have valuable practical applications

Myiasis caused by blowfly larvae is a serious problem affecting animal health and commercial production especially of sheep all over the world. The flies have developed resistance against the commercial pesticides used. We investigated seven plant species used by rural pastoralists to treat these infestations. Extracts of several plant species had good antimicrobial activity (MICs 0.04 to 0.6 mg/ml) against pathogens infecting wounds. Because flies are attracted by volatiles emitted by these microorganisms, treating wounds with such an extract would limit infestation. The activity of extracts on killing, paralysing and metamorphosis of third instar larvae of Lucilia cuprina and Chrysomya marginalis (Diptera: Calliphoridae) were investigated. Several species had promising activities on the larvae. Dose related response activities were determined on four of the most promising plant species (Aloe zebrina Baker, Clausena anisata (Wild) Hook. f. ex. Benth, Erythrina lysistemon Hutchand, Spirostachys africana Sond.). The parameters investigated were larval behaviour, larval development, larval emergence of adult flies, decreased ingestion of meat by the larvae, pupae mass and adult emergence rates. For C. anisata and S. africana extracts the increase in the concentration was also associated with larvae circling on top of the plastic cups possibly indicating repellency and the emerging adult flies being smaller. C. anisata was selected for field evaluation of blow flies on two farms. Larvae exposed to liver baits treated with C. anisata developed slower, had a prolonged larval period, smaller body size, sluggish behaviour, delayed pupation and reduced eclosion rates in comparison to the controls. The active compounds from C. anisata were isolated and characterized. The results have been patented.

References:

[1] Mukandiwa L, Eloff JN, Naidoo V (2012) Veterinary Parasitology 190, 566 – 572.

[2] Mukandiwa L, Eloff JN, Naidoo V (2012) Journal of Ethnopharmacology 143, 812 – 818