The anthelmintic potential of Bacillus thuringiensis to counter the anthelmintic resistance against Haemonchus contortus

Abstract

Haemonchus contortus (H. contortus) has developed resistance to nearly all available anthelmintic medications. Hence, alternative strategies are required to counter anthelmintic resistance. The present study investigated the anthelmintic potential of Bacillus thuringiensis (B. thuringiensis) against H. contortus. Bacterial spp were identified by conventional methods and confirmed by PCR; In addition, PCR amplification of the bacterial 16S rRNA gene detected B. thuringiensis at 750 base pairs (bps). The amplified products were sequenced, and the sequence data were confirmed using the Basic Local Alignment Tool (BLAST), which showed a significant alignment (97.98%) with B. thuringiensis and B. cereus. B. thuringiensis were selected to isolate purified crystal proteins (toxins), The protein profile confirmed by SDS-PAGE showed three prominent bands at 70, 36, and 15 kDa. In addition, the larval development of H. contortus was examined in vitro using two different treatments. Purified crystal protein diluted in 10 mM NaCl at a concentration of 2 mg/ml significantly reduced (P < 0.001) larval development by 75.10% compared to 1 × 10⁸ CFU/ml spore-crystal suspension reduced (43.97%). The findings of in vitro experiments indicated that purified crystal protein was more toxic to the H. contortus larva than the spore-crystal suspension and control group. Moreover, To test the antinematodal effects of B. thuringiensis toxins in vivo, we chose 12 male goats (6 months old) and reared these animals in parasite-free conditions. We performed Fecal egg count reduction tests (FECRT) on samples collected before and after treatment at various times denotes 48 h post-treatment with Purified crystal proteins was significantly decreased (842 ± 19.07) EPG compared to 24 (2560 ± 233.66) and 12 h (4020 ± 165.22). Similarly, after 48 h of treatment, the FECRT of the Spores-crystal mix was reduced (2920 ± 177.20) EPG followed by 24- and 12-h denotes (4500 ± 137.84) and (4760 ± 112.24), respectively. Results of the above experiment suggested that purified crystal proteins have more anthelmintic potential in vivo. Current findings determine that B. thuringiensis toxin against H. contortus could be used in small ruminants to counter anthelmintic resistance. This study also suggested that future research structured on these proteins' pharmacokinetics and mode of action.

Keywords: Anthelmintic resistance; Bacillus thuringiensis; Biological control; Crystal proteins; Haemonchus contortus; In vitro; In vivo; Spores-crystal suspension.