H. contortus (Barber's pole worm) is an economically significant parasite available in tropical and temperate areas. It is a major cause of economic losses in small ruminants and significantly impacts the livestock industry worldwide (Wang et al., 2017, Sanders et al., 2020). H. contortus is a blood-feeding pathogenic strongyle of the gastrointestinal tract (GIT) that cause Haemonchosis; it can change hematological, biochemical, and immune markers with stimulation of oxidative stress. It is a leading cause of anemia in small ruminants worldwide, particularly those raised in pasture-based systems in warm, rainy climates. Nowadays, H. contortus survives in low-risk zones due to climate change. (Arsenopoulos et al., 2021 Flay et al., 2022 Rinaldi et al., 2015). Control of this parasite was achieved mainly using anthelmintics in conjunction with grazing management where possible. However, the producer is increasingly facing anthelmintic resistance, a stark reality for many small ruminant producers. Moreover, consumers are more aware of the dangers of drug residues in meat and dairy products, and due to these aspects, small ruminant production is affected (Sanders et al., 2020; Alam et al., 2020, Ana Paula et al., 2016). Previous findings revealed that 98% of sheep and goat farms in the United States were resistant to benzimidazole, 54% levamisole, 76% of ivermectin, and 24% of moxidectin, respectively (Howell et al., 2008). However, farmers have frequently used ivermectin since 1981, even though no new class of anthelmintics has been developed (Kaplan and Vidyashankar, 2012). Resistance to several anthelminthic groups gradually develops in livestock hosts in specific parasite species and across a broad range of parasite species. Hence novel anthelmintics were required on an urgent basis (Alam et al., 2020; Sanders et al., 2020). According to the research findings, probiotics containing Bacillus spp. may be an excellent choice to reduce nematode parasites' risk to sheep herds. Biological control with the help of competent strains of genus Bacillus including B. thuringiensis and B. circulans, have Nematocidal properties and revealed a 98% of lethal effect against H. contortus larvae isolated from goats and sheep species (Sinott et al., 2012, Sinott et al., 2016 and Lopez-Arellano et al., 2002 Beena et al., 2019). B. thuringiensis contains non-hemolytic parasporal crystal toxins Crystal (Cry) and Cytolytic (Cyt) genes. These toxins belong to the bacterial plasmid, commonly called delta endotoxin, and are mainly produced during sporulation (Sieiro et al., 2021; Nagamatsu et al., 2010). Crystal proteins produce a toxic effect on a target organism. Likewise, Cytolytic proteins show hemolytic activity. These toxins are harmless to animals and plants and are completely biodegradable. Recently, a new non-small molecule method for treating gastrointestinal nematodes (GINs) uses B. thuringiensis crystal protein 5B (Cry5B), a naturally occurring protein produced by B. thuringiensis widely and safely used as a bio-insecticide worldwide (Sanders et al., 2020). Scientists studied the H. contortus larvicidal effect of bacillus toxin when they fed bacterial supplements to the naturally infected sheep population. The bacterium was found in fecal material within four hrs. (Sinott et al., 2016). B. thuringiensis exists in gram-positive spore-forming with entomo-pathogenic effects. Therefore, B. thuringiensis is a viable alternative tool for controlling harmful species (Bravo et al., 2005). Besides discrimination between B. cereus and B. thuringiensis, it is pretty tricky. According to some data, distinguishing between B. thuringiensis from B. cereus is possible via a single feature, such as the presence of a parasporal crystal protein; these proteins are distinguishing feature of B. thuringiensis that distinguishes it from B. cereus (Chen and Tsen. 2002).

In this study, B. thuringiensis and B. cereus spp, identified from the Sindh province of Pakistan, were screened for their nematocidal properties against H. contortus larvae in Barbari goats, spores of Bacillus spp from that area are unavailable. That's why we submit the bacteria for sequencing to confirm the species of the bacterium. According to (FAO) and other resources, approximately 24.24 million sheep and 49.14 million goats are available in Pakistan. The Barbari goat population is 2.4 million worldwide; nearly all are in Pakistan. This country's environmental conditions are very suitable for raised species of small ruminants and favor the inhabitants of H. contortus. Pakistan had recently flooded, and parasitic infections plagued the livestock population. As a result, this study aimed to find a way to biologically control the H. contortus population and save the small ruminants.