Bacteria Associated with the Parasitic Nematode Haemonchus contortus and Its Control Using Antibiotics

Abstract

Internal parasitism, a significant cause of production losses in sheep, is routinely controlled by anthelmintic drenches. A better understanding and alternative control strategies are needed to combat the increasing resistance. This study investigated the presence of resident bacteria in the field strain of Haemonchus contortus. Adult female worms were collected from the abomasa of sheep. DNA was extracted from adult female worms and parasite eggs laid in vitro using long or shorter enzymatic incubation methods. Polymerase Chain Reaction (PCR) was performed using universal bacterial and phylum Firmicutes-specific primers; PCR products were cloned and sequenced. The analysis of the sequences shows a majority of the sequences belong to rumen bacteria, mainly Ruminococcus. Streptococcus was detected in four eggs, and adult worm samples and the sequences had a very high homology to the Streptococcus sequences in the database. Clostridium was detected only in the adult samples, whereas Nevskia and Pseudomonas were detected only in the egg samples. Three antibiotics, Ampicillin (Amp), Gentamycin (Gen) and Tetracycline (Tet), individually or combination, were tested to establish proof of concept that abomasal nematode parasites can be controlled by killing the resident bacteria. A larval migration inhibition assay was used to test the hypothesis. Tet (10 and 20 mM) resulted in around 30% mortality in larvae. Amp and Gen did not result in significant levels of larval mortality but, when given in combination, resulted in significant mortality of the larvae, suggesting the role of antibiotics in controlling the parasites by targeting the resident bacteria.

Bacteria associated with ovine gut parasites Trichuris ovis and Haemonchus contortus

“…The most abundant bacterial phyla in H. contortus are in agreement with previous assessments for the species, although previous studies reported Tenericutes in H. contortus , which we have not found (Bouchet et al 2022; El-Ashram and Suo 2017; Mafuna et al 2021; Sinnathamby et al 2018). Though comparing the microbiome of different life stages of H. contortus , these studies have not compared it with the microbiome of any other nematode species inhabiting the same host.…”

“…Furthermore, this study revealed some unique genera in H. contortus that were not found by previous studies (Bouchet et al 2022;Mafuna et al 2021;Sinnathamby et al 2018). These include Spiroplasma, Collinsella, Dialister, Holdemanella, Agathobacter, Veillonella, Catenibacterium, Megamonas, Butyricicoccus and Empedobacter which could have been incorporated from the host.…”

The microbial community associated with Parascaris spp. infecting juvenile horses

“…study, the phylum Bacteroidetes was the most prevalent [ 78 ]. In three H. contortus studies, a limited number of phyla were detected overall [ 73 , 74 , 76 ], whereas 23 were identified in another [ 75 ], which is similar in number to the 22 phyla identified in this study. A total of 36 phyla were identified in Trichuris spp.…”

“…are the only other parasites of veterinary importance to have had their microbiota analyzed. Four microbiota studies have been completed for H. contortus [ 73 – 76 ] and two for Trichuris spp. [ 77 , 78 ].…”

“…Despite the successful use of the microbiota for control of filarial nematodes, parasite microbiota as a whole remain understudied. Four microbiota studies have been completed for Haemonchus contortus , the most important nematode parasite affecting small ruminants, and have explored the microbiota of life stages [ 73 , 74 ] and sexes [ 73 , 75 ], the effect of antibiotics on parasite longevity [ 76 ], and the identification of intracellular bacteria via microscopy [ 74 ]. Two microbiome studies have been completed for Trichuris spp., an important parasite of humans and pigs [ 77 , 78 ].…”