Effects of repellent secretion of variegated grasshopper (Zonocerus variegatus) (L) on free living stages of Heligmosomoides bakeri

Abstract Background Infections caused by parasitic worms in humans and animals are a significant global health concern. Chemical disinfectants used to control helminths have been known to have adverse environmental effects. This study evaluated the effects of the repellent secretion of the variegated grasshopper ( Zonocerus variegatus ) on egg embryonation, hatching inhibition, and larval mortality of a rodent helminth species- Heligmosomoides bakeri . Zonocerus variegatus adults were collected from farmlands in Federal University of Agriculture, Abeokuta, Ogun State, Nigeria, and their repellent secretion was obtained using a glass pasture pipette. Fresh H. bakeri eggs from experimentally infected mice were processed using standard methods. Forty-five petri dishes were divided into three treatment groups: Z. variegatus repellent secretion (ZVRS), sodium hypochlorite (NaOCl), and distilled water (DW). Eighty fresh H. bakeri eggs were added to each petri dish and incubated with 0.5 ml of ZVRS, NaOCl, and DW at 4 °C. Larval stages (L 1 , L 2 , and L 3 ) were exposed to the same treatments and observed at various intervals. Results The ZVRS and DW did not inhibit embryonation of H bakeri eggs, while NaOCl achieved 100% inhibition after 24 h. ZVRS inhibited 88.8% of eggs after 48 h, reducing to 68.9% by day seven. Sodium hypochlorite maintained 100% inhibition throughout. For larval mortality, ZVRS showed 0.0% mortality after 30 min but increased over time, reaching 37.5% and 52.5% for L 1 and L 2 at 24 h. Sodium hypochlorite consistently showed 100% mortality, while DW showed 0.0%. At the end of the exposure period, 16.25% of L 1 and 5% of the L 2 exposed to ZVRS reached the infective stage (L 3 ) but could not establish infection in mice. Conclusion The study demonstrated that Zonocerus variegatus repellent secretion has anthelmintic properties which could provide guidelines for development of safe and affordable disinfectants.