Biosafety of Beauveria Bassiana as a biopesticide: No effects on sex hormones in experimental rats

Abstract

This study evaluates the possible antagonistic effects of challenging wistar rats with the entomopathogenic fungi (Beauvaria bassiana) on their reproductive hormones. The fungus was isolated from diseased African grasshoper (Zonocerus variegatus) picked from cassava plantation within Adekunle Ajasin University Akungba-Akoko University farm. The insects were brought to the laboratory and watched for the onset of disease symptoms. Veen’s media was used in the isolation of the entomopathogenic fungus from the insect cadavers after surface-sterilization and humid-incubation. Spore and conidia suspension of the entomopathogenic fungus was then prepared from a 14-day old culture of the microbe and used to infect another batch of the insect to confirm entomopathogenicity.  An inoculum of the fungus was prepared and the concentration was adjusted to 10⁶ sfu/ml. The inoculum was used to challenge the laboratory rats and watched for a period of 7days before being sacrificed. A control experiment was set up where the animals were not challenged with any microbe. Blood were collected into heparin bottles through ocular puncture and analysed for selected reproductive hormones using immunoassay kit. The rats were examined to ascertain they are in uniform reproductive cycle to minimize the spiking or reduction in hormonal concentration as a result of a varying phase before being sacrificed.  Results showed a change in some hormonal levels in challenged rats compared to rats within the control group. Progesterone level was 6.67±1.16ng/mL in challenged rats while it was 6.33±0.58ng/mL in rats within the control group. Testosterone level was 3.40±0.20ng/mL and 3.50±0.17ng/mL respectively in rats within the challenged and control group respectively. However, Follicle Stimulating Hormone level was 2.00±0.10 mIU/mL and 1.93±0.12mIU/mL in challenged and control rats respectively.  Despite the reduction, the values were still within the acceptable range with the exception of testosterone. This shows that usage of B. bassiana as an entomopathogenic fungus in the formulation of biopesticides pose less risk to the handler and the environment upon its deliberate release or accidental exposure.