An assessment of benzimidazole resistance against caprine nematodes in Central India

Prevalence status and detection of benzimidazole resistance using AS-PCR in Haemonchus contortus of goats from Marathwada region, Maharashtra, India

This study examined Haemonchus contortus prevalence and benzimidazole resistance in eight districts of Marathwada, Maharashtra, India. A comprehensive investigation of 264 abomasa of goats collected from abattoirs and goats necropsied at the College of Veterinary Sciences and Animal Husbandry, Parbhani, revealed 21.21 % a prevalence of H. contortus. The incidence of H. contortus did not vary much across seasons and it was highest in summer (23.42 %), followed by monsoon (22.89 %), and lowest in winter (15.71 %). Statistically non-significant (p < 0.05) prevalence was observed in male and female animals. A detailed examination of 168 adult H. contortus worms from eight districts revealed the presence of all conceivable genotypes including homozygous resistant (rr), susceptible (SS), and heterozygous (Sr) BZ susceptible genotypes. The rr was the most frequent at 50 %, followed by SS at 27 % and Sr at 22 %. The presence of the SNP was observed in in all eight randomly selected and sequenced samples.

New Insights on Tools for Detecting β-Tubulin Polymorphisms in Trichuris trichiura Using rhAmpTM SNP Genotyping

Soil-transmitted helminth (STH) infections, commonly treated with benzimidazoles, are linked to resistance through single nucleotide polymorphisms (SNPs) at position 167, 198, or 200 in the β-tubulin isotype 1 gene. The aim of this study was to establish a novel genotyping assay characterized by its rapidity and specificity. This assay was designed to detect the presence of SNPs within the partial β-tubulin gene of Trichuris trichiura. This was achieved through the biallelic discrimination at codons 167, 198, and 200 by employing the competitive binding of two allele-specific forward primers. The specificity and reliability of this assay were subsequently confirmed using Trichuris samples isolated from captive primates. Furthermore, a molecular study was conducted to substantiate the utility of the β-tubulin gene as a molecular marker. The assays showed high sensitivity and specificity when applied to field samples. Nevertheless, none of the SNPs within the β-tubulin gene were detected in any of the adult worms or eggs from the analyzed populations. All specimens consistently displayed an SS genotype. The examination of the β-tubulin gene further validated the established close relationships between the T. trichiura clade and Trichuris suis clade. This reaffirms its utility as a marker for phylogenetic analysis.

Detection of Benzimidazole Resistance-Associated Single-Nucleotide Polymorphisms in the Beta-Tubulin Gene in Trichuris trichiura from Brazilian Populations

Preventive chemotherapy is recommended by the WHO as the main strategy for controlling infections caused by nematodes in humans, aiming to eliminate the morbidity associated with these infections. This strategy consists of routine periodic administration of benzimidazoles, among other drugs. Although these drugs decrease the intensity of infections, they have the potential to exert selection pressure for genotypes bearing mutations associated with drug resistance, which may result in the establishment of resistant worm populations. There is evidence in the literature of resistance to these drugs in nematodes that infect humans, including in the species Trichuris trichiura. Single-nucleotide polymorphisms (SNPs) in the beta-tubulin gene located at codons 167, 198, and 200 are associated with the mechanism of resistance to benzimidazoles in nematodes. Here, we standardized a molecular technique based on an amplification refractory mutation system-polymerase chain reaction (ARMS-PCR) to analyze codons 167, 198, and 200 of T. trichiura. The ARMS-PCR methodology was successfully established to evaluate the codons of interest. A total of 420 samples of individual eggs were analyzed from populations obtained from five Brazilian states. A mutation in codon 198 was observed at a frequency of 4.8% (20/420), while for the other two codons, no polymorphism was observed. This is the first report of the presence of this mutation in populations of T. trichiura in Brazil. This fact and the emergence of the problem already observed in other species reinforces the need for regular monitoring of SNPs related to benzimidazole resistance using techniques that are highly sensitive and specific.

Moving beyond the state of the art of understanding resistance mechanisms in hookworms: confirming old and suggesting new associated SNPs

Hookworms represent a serious problem for human and animal health in different parts of the world. One of the suggested control strategies for parasitosis caused by members of the Ancylostomatidae family is mass drug aministration with benzimidazole compounds. This strategy has been proven to lead to the establishment of resistant strains in several nematodes related to SNPs at codons 167, 198 and 200 of the beta-tubulin isotype-1 gene. Through bioassay and in vivo analysis, we successfully isolated an albendazole-resistant A. ceylanicum strain by drug selective pressure. We observed a strong correlation between the presence of SNPs at codon 198 and drug resistance. We also described for the first time, in hookworms, the presence of SNP A200L, already described at low frequencies in ruminant nematodes. The results presented here are important for updating the current knowledge about anthelmintic resistance in hookworms. The answers and the new questions raised may provide a basis for the establishment of more effective control strategies.

Nanoparticles as Alternatives for the Control of Haemonchus contortus: A Systematic Approach to Unveil New Anti-haemonchiasis Agents

Haemonchus contortus is an infectious gastrointestinal nematode parasite of small ruminants. This study addresses the in vitro/in vivo anti-haemonchiasis potential, toxicological effects, and mechanism of action of nanoparticles. Online databases were used to search and retrieve the published literature (2000 to 2021). A total of 18 articles were selected and reviewed, out of which, 13 (72.2%) studies reported in vitro, 9 (50.0%) in vivo, and 4 (22.2%) both in vitro/in vivo efficacy of different nanoparticles. Mostly, organic nanoparticles (77.7%) were used including polymeric (85.7%) and lipid nanoparticles (14.3%). The highest efficacy, in vitro, of 100% resulted from using encapsulated bromelain against eggs, larvae, and adult worm mortality at 4, 2, and 1 mg/ml, respectively. While in vivo, encapsulated Eucalyptus staigeriana oil reduced worm burden by 83.75% and encapsulated Cymbopogon citratus nano-emulsion by 83.1%. Encapsulated bromelain, encapsulated Eucalyptus staigeriana oil, and encapsulated Cymbopogon citratus nano-emulsion were safe and non-toxic in vivo. Encapsulated bromelain damaged the cuticle, caused paralysis, and death. Nanoparticles could be a potential source for developing novel anthelmintic drugs to overcome the emerging issue of anthelmintic resistance in H. contortus. Studies on molecular effects, toxicological consequences, and different pharmacological targets of nanoparticles are required in future research.

Biomedical Evaluation of Lansium parasiticum Extract-Protected Silver Nanoparticles Against Haemonchus contortus, a Parasitic Worm

Here we show the novel anti-helminthic potential of Lansium parasiticum aqueous extract-protected silver nanoparticles (LAgNPs) against albendazole-resistant gastrointestinal parasite Haemonchus contortus. LAgNPs showed LD₅₀ values of 65.6 ± 32.8 nM (12 h), 139.6 ± 39.9 nM (12 h), and 64.3 ± 8.5 nM (24 h) against adult male, female, and L3 larvae, respectively. LAgNPs was also quite effective in inhibiting egg hatching, with an IC₅₀ value of 144.4 ± 3.1 nM at 48 h of exposure. Exposure to LAgNPs generated oxidative stress and mediated physical damage in the worms' tissue. A sharp increase in reactive oxygen species and nitric oxide synthase levels was prominent due to LAgNPs' exposure. In response to oxidative stress, a sharp increase of stress-responsive enzymes' activity, like catalase, superoxide dismutase, and glutathione peroxidase activity, along with the concentration of glutathione, was observed in worm tissue, which indicated a LAgNP-responsive alteration of metabolism. The results give rise to the opportunity for the development of alternative treatment for drug-resistant parasitic worms.

Cuminaldehyde induces oxidative stress-mediated physical damage and death of Haemonchus contortus

Cuminaldehyde (CA), a monoterpenoid, preset in many plant sources including cumin, induces reactive oxygen-related damage and death in Haemonchus contortus, a parasitic worm with an LD50, values of 127.3 ± 7.5, 184.5 ± 12.1 and 104.1 ± 7.9 μg/mL for an adult female, adult male worms (12 h) and L3 larvae, respectively (24 h). Fifty percent of inhibition of egg hatching (IC50) was obtained at 142.4 ± 11.4 μg/mL after 48 h of exposure. Scanning electron microscopy revealed physical damage to the anterior and posterior ends, intestinal, ovarian, and esophageal regions of the warms on exposure to ca. The exposure of worms to CA also led to a systemic increase in reactive oxygen species (ROS) within 3 h. The better activity was seen with CA compared to standard antihelminthic drug albendazole (Alb). 74 μg/mL CA showed 2.3 fold more increase of catalase (CAT), 0.61 fold increase of superoxide dismutase (SOD), 3.3 fold increase of glutathione peroxidase (GPx) activity and 17.5 fold increase of glutathione (GSH) activity in comparison with Alb (500 μg/mL) for the same time of exposure (3 h). A firm increase of (2.9 fold) was also observed in nitric oxide synthase (NOS) activity within 12 h of exposure with CA (74 μg/mL) in comparison with Alb. Therefore the preclinical potential of CA is much higher than widely used antihelminthic drug Alb. The results open new opportunities to explore CA as a new active antihelminthic molecule.

Molecular detection of benzimidazole resistance in Haemonchus contortus of sheep in Punjab

Single nucleotide polymorphism (SNP) at codon 167, 198 and 200 of β-tubulin isotype 1 gene accounts for benzimidazole resistance in Haemonchus contortus. To assess the anthelmintic resistance to benzimidazole group, allele specific polymerase chain reaction (AS-PCR) was employed on 50 adults of local abattoir of Ludhiana and 138 harvested larvae of H. contortus from faecal samples collected from field flocks of 6 districts of western zone of Punjab. The adults were found to be homozygous resistant (rr) showing 100% prevalence of resistant allele (r). AS-PCR on 138 larvae collected from different districts of Punjab showed 49.28% (69) homozygous resistant (rr), 3.62% (5) homozygous susceptible (SS) and 46.37% (64) heterozygous (rS) population. Species was confirmed as H. contortus by PCR-RFLP from the three fragments of size 462 bp, 211 bp and 147 bp. The pioneer study on the molecular diagnosis of benzimidazole resistance in H. contortus showed an overall allele frequency for resistant and susceptible population to be 0.72 (TTC) and 0.28 (TAC), espectively indicating development of high level of resistance in sheep.

First identification of the benzimidazole resistance-associated F200Y SNP in the beta-tubulin gene in Ascaris lumbricoides

The main control strategy for Ascaris lumbricoides is mass drug administration (especially with benzimidazoles), which can select strains of parasites resistant to treatment. Mutations in the beta-tubulin isotype-1 gene at codons 167, 198 and 200 have been linked to benzimidazole resistance in several nematodes. The mutation in codon 200 is the most frequent in different species of parasites, as previously observed in Necator americanus and Trichuris trichiura; however, this mutation has never been found in populations of A. lumbricoides. This study aimed to screen for single nucleotide polymorphisms (SNPs) in the beta-tubulin isotype-1 gene at codon 200 in A. lumbricoides. We developed a technique based on an amplification refractory mutation system (ARMS-PCR) for the analysis of 854 single A. lumbricoides eggs collected from 68 human stool samples from seven Brazilian states. We detected the mutation in codon 200 at a frequency of 0.5% (4/854). This is the first report of this mutation in A. lumbricoides. Although the observed frequency is low, its presence indicates that these parasite populations have the potential to develop high levels of resistance in the future. The methodology proposed here provides a powerful tool to screen for the emergence of anthelmintic resistance mutations in parasitic nematode populations.

Efficacy of herbal extracts and closantel against fenbendazole-resistant Haemonchus contortus

This study assessed the efficacy of closantel vis-à-vis herbal extracts with known anti-parasitic properties, against fenbendazole-resistant nematodes in goats maintained under a semi-intensive system of management at the University goat farm, Jabalpur. Fifty goats were randomly assigned to five groups, each comprising 10 animals, irrespective of their breed, age and sex. Each animal in Group I, II and III was orally administered with aqueous leaf extracts of neem (Azadirachta indica) at 1 g/kg body weight, sitaphal (Annona squamosa) at 1.5 g/kg body weight and tobacco (Nicotiana tabacum) at 1 g/kg body weight, respectively, whereas Group IV was an untreated control group. Each animal in Group V was orally treated with closantel at 10 mg/kg body weight. During the course of the study, all animals were maintained under an identical semi-intensive system of management. Compared to the untreated control group (Group IV), there was no conspicuous reduction in post-treatment (day 10) faecal egg counts (FEC) in animals administered with the herbal extracts (Groups I, II and III), which is suggestive of poor anti-parasitic activity. However, using the faecal egg count reduction test (FECRT), the overall efficacy of closantel was recorded as 95.64%. This supports the rotational use of closantel as a preferred choice over the benzimidazole group of anthelmintics and/or herbal extracts to meet the acute challenge of in situ development of drug-resistant gastrointestinal nematodes, especially Haemonchus contortus.

Standardization and application of a modified RFLP-PCR methodology for analysis of polymorphisms linked to treatment resistance in Ancylostoma braziliense

BACKGROUND

Single nucleotide polymorphisms (SNPs) in codons 167, 198 and 200 of the beta-tubulin isotype 1 gene are associated with benzimidazoles resistance in many helminths. Codon 167 mutation has never been described in hookworms; however, polymorphisms in codons 198 and 200 have been described for Ancylostoma caninum and Necator americanus. These mutations have never been investigated in Ancylostoma braziliense; therefore, it is not known if they are present in this species and whether they are correlated with treatment resistance. The RFLP-PCR technique has been used to analyze these polymorphisms in some nematodes, but depending on the species, these alterations do not create or eliminate any restriction enzyme cleavage site, making it impossible to use this technique. Here, we describe the standardization and application of a modified RFLP-PCR technique for detecting polymorphisms in individual A. braziliense worms recovered from naturally infected dogs in two Brazilian states.

RESULTS

The molecular techniques used were sensitive, specific, and easy to apply. To our knowledge, we report for the first time the presence of a polymorphism at codon 198 of the beta-tubulin gene of A. braziliense (1/81; 95% CI: 0-3.69%).

CONCLUSIONS

It is not known whether the presence of the mutation in codon 198 of the beta-tubulin gene of A. braziliense has importance for this parasite. However, based on studies of other helminths, it is possible that this polymorphism is directly related to the resistance to benzimidazoles. This may be a major concern, since this nematode has considerable relevance as a parasite of canids and felids and as one of the agents of cutaneous larva migrans in humans. Standardized methodologies will be useful for screening for polymorphisms in the beta-tubulin gene of canine hookworms in a broader population. The method could also be adapted for the analysis of other SNPs in other nematode species.