Gut microbial signatures associated with moxidectin treatment efficacy of Haemonchus contortus in infected goats

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Highlights

Abstract

Parasitic infections are associated with profound changes in the structure and function of the gut microbiome in various host-parasite systems. Here we examined the microbial composition and function in the abomasum, proximal colon and feces of Haemonchus contortus-infected goats after a partial anthelmintic drug clearance. A single-dose treatment of H. contortus-infected goats with Cydectin (moxidectin) resulted in an 83.9 % and 61.8 % reduction in fecal egg counts (EPG) and worm burden, respectively (P < 0.01), and restored abomasal pH to a normal baseline level. The treatment significantly increased the abundance of Proteobacteria, particularly that of Campylobacter, in the proximal colon. It also significantly affected several basic pathways, including bacterial secretion, butyrate metabolism, and LPS biosynthesis, and seemingly reduced the cellulolytic capacity in the colon. Several network modules displayed a strong correlation with EPG and worm burden. The Mantel test indicated a strong correlation between treatment related network topologies of the operational taxonomic units (OTU) belonging to Actinobacteria and Rikenellaceae and EPG and worm burden levels, respectively. Furthermore, microbial signatures that may better predict anthelmintic efficacy were identified. A signature or balance represented by the log ratio of the abundance of Verrucomicrobiaceae and Camplyobacteraceae had a strong correlation with EPG (r = 0.80). These novel insights into the interactions between H. contortus and gut microbiome in the caprine host and the consequence of a partial anthelmintic clearance on animal health and well-being may facilitate the design of more effective next-generation anthelmintics.

Introduction

The barber's pole worm Haemonchus contortus, a voracious blood sucking parasite of the abomasum of ruminants, represents the primary constraint to profitable sheep and goat production in many regions of the world. The economic cost of the infection is enormous; and it is estimated that the annual cost of roundworms in Australia ranges from $5.80 to $11.09 per ewe, depending on management schemes (https://rune.une.edu.au/web/handle/1959.11/10927). Approximately 80 % of the cost is related to lost production while the remaining 20 % represents the cost of parasite controls. Adult H. contortus worms can consume up to 30 μl of blood per day, rapidly causing severe anemia, affecting feed efficiency and increasing mortality in young animals (Zajac, 2006). Furthermore, the rapid emergence of anthelmintic resistant strains in this parasite species is becoming a serious global concern (Gilleard, 2013). Recent findings suggest that the widespread use of anthelmintics and adaptation to climate changes are shaping genetic diversity in H. contortus (Salle et al., 2019). Evolutionary divergence facilitates the development of a different set of strategies to regulate parasitic infections in small ruminants (Hoste et al., 2010). A direct comparison of eggs per gram of feces (EPG) from sheep and goats grazing together on the same pasture suggests that the mechanisms of resistance in goats are different from those in sheep (Pomroy et al., 1986). Moreover, worldwide production of goats is increasing at a more rapid rate than that of sheep. However, the bulk of our scientific data on host-Haemonchus interactions in small ruminants has been accumulated from ovine studies. As a result, emphasis on specific caprine studies is warranted.

Parasitic infections are known to be associated with profound changes in the structure and function of the host gut microbiome (Afrin et al., 2019; Clark et al., 2018; Li et al., 2016, 2012b; Pan et al., 2019; Wang et al., 2019; Wu et al., 2012). Recently, pathophysiological relevance of the microbiome of different stages of H. contortus under in vitro and in vivo conditions has been recognized (El-Ashram and Suo, 2017; Sinnathamby et al., 2018). Our previous study showed that an experimental H. contortus infection in parasite-naïve Alpine goats reduces bodyweight gain and results in a significant increase in abosamal pH values (Li et al., 2016). The infection causes a profound change in microbial composition at the site of infection, the abomasum. The infection alters the balance of archaea and bacteria and the abundance of ∼ 25 % of the OTUs detected in the abomasal microbiome. The infection-induced alterations in the abomasal microbial community may negatively influence host protein metabolism and immune function. Furthermore, parasitic infections increase the abundance of pathogenic bacteria, such as those in the genus Campylobacter (Li et al., 2012b; Wang et al., 2019), and the family Pasteurellaceae (Li et al., 2016), which may increase the risk of subsequent bacterial and viral disease particularly in parasite susceptible animals (Clark et al., 2018).

While it is generally accepted that parasitic infections are associated with significant alterations in gut microbial composition and function, many other questions remain to be answered. For example, can parasite-induced disruptions in the gut microbiome be restored using anthelmintics? Are there any ecological consequences of a partial drug clearance of parasite worms to the gut microbial community? In this study, we investigated the host-parasite-microbiome interactions using 16S rRNA gene-based approaches and global network algorithms in a goat model. Further, we focused on the potential negative consequences of an ineffective anthelmintic treatment on microbial communities along the gastrointestinal tract in goats infected with H. contortus.

Section snippets

Animal experiment

Sixteen male kid goats [breed: Sire (Boer) x Dam (Kiko x Savanna x Boer)] at an age of 19–28 weeks were purchased locally. All animal care procedures were strictly followed according to a protocol approved by the USDA Beltsville Area Institutional Animal Care Committee (Animal Protocol #12-025). The goats were dewormed with moxidectin at the recommended dose and vaccinated with Clostridium perfringens types C and D and tetanus (CDT vaccine) prior to arrival in Beltsville. The efficacy of

Anthelmintic treatment reduced microbial richness in the proximal colon

Oral administration of a single dose of moxidectin, a milbemycin macrocyclic lactone, to goats experimentally inoculated with H. contortus L3 significantly reduced EPG and worm burden by 83.9 % and 61.8 %, respectively (Fig. 1, P < 0.01) at 16 days after dosing. The treatment led to a marginal improvement in abomasal pH, from 2.97 to 2.54. Unlike in naïve goats, where a primary Haemonchus infection significantly elevated abomasal pH (Li et al., 2016), the goats used in this study had prior

Author contributions

Conceived and designed the experiment: JFU, RVA, RWL

Performed the experiment: FL, YX, AMZ, YH, JFU

Analyzed the data: FL

Wrote the manuscript: FL, RWL

Declaration of Competing Interest

The authors declare that they have no conflict of interest.

Acknowledgments

Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U. S. Department of Agriculture (USDA). The USDA is an equal opportunity provider and employer. YH and RVA were supported by maintenance. The study was supported by National Institutes of Health- National Institute of Allergy and Infectious Diseases (R.V.A., grant number R01 AI056189); Agriculture and Food Research

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