Species-specific PCR for the identification of Cooperia curticei (Nematoda: Trichostrongylidae) in sheep

A molecular assessment of Ostertagia leptospicularis and Spiculopteragia asymmetrica among wild fallow deer in Northern Ireland and implications for false detection of livestock-associated species

BACKGROUND

Wild deer populations utilizing livestock grazing areas risk cross-species transmission of gastrointestinal nematode parasites (GINs), including GINs with anthelmintic resistance (AR) traits. Wild deer have been shown to carry problematic GIN species such as Haemonchus contortus and Trichostrongylus species in the UK, but the presence of livestock GINs in Northern Ireland deer populations is unknown. Also, is it not known whether AR traits exist among GINs of deer such as Ostertagia leptospicularis and Spiculopteragia asymmetrica in pastureland where anthelmintics are heavily used.

METHODS

Adult-stage GIN samples were retrieved from Northern Irish wild fallow deer abomasa. Individual specimens were subject to a species-specific PCR analysis for common sheep and cattle GIN species with ITS-2 sequence analysis to validate species identities. In addition, the beta-tubulin gene was subject to sequencing to identify benzimidazole (BZ) resistance markers.

RESULTS

ITS-2 sequencing revealed O. leptospicularis and S. asymmetrica, but species-specific PCR yielded false-positive hits for H. contortus, Teladorsagia circimcincta, Trichostrongylus axei, T. colubriformis, T. vitrinus and Ostertagia ostertagi. For beta-tubulin, O. leptospicularis and S. asymmetrica yielded species-specific sequences at the E198 codon, but no resistance markers were identified in either species at positions 167, 198 or 200 of the coding region.

DISCUSSION

From this report, no GIN species of significance in livestock were identified among Northern Ireland fallow deer. However, false-positive PCR hits for sheep and cattle-associated GINs is concerning as the presence of deer species in livestock areas could impact both deer and livestock diagnostics and lead to overestimation of both GIN burden in deer and the role as of deer as drivers of these pathogens. ITS-2 sequences from both O. leptospicularis and S. asymmetrica show minor sequence variations to geographically distinct isolates. AR has been noted among GINs of deer but molecular analyses are lacking for GINs of wildlife. In producing the first beta-tubulin sequences for both O. leptospicularis and S. asymmetrica, we report no BZ resistance in this cohort.

CONCLUSIONS

This work contributes to genetic resources for wildlife species and considers the implications of such species when performing livestock GIN diagnostics.

Molecular identification and phylogenetic analysis of gastrointestinal nematodes in different populations of Kazakh sheep

Gastrointestinal nematode (GIN) infection in sheep has been recognized globally as a major problem challenging animal health and production. The objective of this study is to use a molecular diagnosis of the prevalence for gastrointestinal nematode (GIN) dominant species of Kazakh sheep and its hybrid (Kazakh × Texel). The internal transcribed spacer 2 (ITS-2) sequences of ribosomal DNA (rDNA) were used as the target sequence. In the study, three dominant species of nematodes, namely Haemonchus contortus, Trichostrongylus spp., and Teladorsagia (Ostertagia) circumcincta from the Kazakh sheep and the F1 and F2 generations of Texel × Kazakh sheep hybrids were subjected to molecular identification and phylogenetic analysis. The fecal and single larva genomic DNA were extracted and amplified by PCR using specific primers to determine the infection rate of the three nematode species. In addition, the PCR products were sequenced and analyzed using bioinformatics methods to construct a phylogenetic tree. The results showed that all the three species had their ITS-2 specific amplified. According to the sequence homology analysis of PCR products, the results showed a high homology (above 98.5% homology) with H. contortus, Trichostrongylus spp., T. circumcincta ITS-2 sequences in GenBank. Phylogenetic analysis showed that the ITS-2 sequences of the three species were on the same branch as the ITS-2 sequences of the same species in NCBI. And on different branches from those of the ITS-2 sequences of different families, genera and species. Sequences carried out on three species from different samples showed a close relationship and little genetic difference in phylogenetic tree. The infection rates based on fecal DNA were 35.59, 25.55, and 11.24% for H. contortus, Trichostrongylus spp., and T. circumcincta, respectively. While the infection rates based on larva DNA, were 24.07, 18.89, and 13.26% for H. contortus, Trichostrongylus spp., and T. circumcincta, respectively. The seasonal prevalence of the three dominant species in spring was significantly higher than that in autumn and winter. And there was no significant difference between Kazakh, F1 and F2 sheep considering the infection rate of the studied three species of nematodes. This study provides valuable molecular approaches for epidemiological surveillance and for assisting in the control of Nematodirus infection in sheep.

Influence of breed and parasite challenge on the immune response to naturally acquired intestinal nematode infection in sheep

Natural infection by intestinal nematodes was assessed in Santa Ines and Ile de France sheep breeds, over a five-month grazing period, with emphasis on the development of the immune response in lambs under two anthelmintic treatment regimens. Nineteen Santa Ines and 19 Ile de France male lambs were allocated into two treatment groups: animals under suppressive treatment with anthelmintics; and animals under targeted selective treatment (TST). The nematodes Trichostrongylus colubriformis and Strongyloides papillosus showed the highest infection intensity in the TST animals in both breeds. Parasite-specific immunoglobulin G levels were significantly higher and more rapidly induced in Santa Ines lambs. Additionally, these lambs had higher levels of parasite-specific immunoglobulin A in intestinal mucus. Animals under TST had higher means of mast cells and globule leukocytes in the intestinal mucosa due to longer and greater parasite challenge in comparison with the suppressive group. A breed effect (P < 0.05) was recorded for mast cells, with Santa Ines lambs presenting the highest counts. Although Santa Ines lambs had lower intestinal nematode counts than Ile de France lambs, they had shown a large variation in T. colubriformis burden, with most of them presenting a marked worm burden, despite showing an earlier and more intense immune response to intestinal nematode infection.

Evaluation of a Cooperia oncophora double-domain ASP-based vaccine against Cooperia spp. infections in cattle and sheep

A double-domain activation-associated secreted protein (dd-Co-ASP) isolated from the bovine small intestinal parasite Cooperia oncophora was previously shown to be an effective vaccine candidate to protect calves against a homologous challenge infection. The aim of this study was to investigate whether the dd-Co-ASP protein, purified from a Belgian C. oncophora isolate, would offer protection against a C. oncophora isolate from the southern hemisphere as well as other Cooperia species such as C. punctata in cattle and C. curticei in sheep. Two vaccination studies were performed, i.e. one in cattle and one in sheep, in which the protective effects of dd-Co-ASP, supplemented with Quil A as an adjuvant, were compared with an adjuvant control. Whereas our results showed a 75 % reduction in Cooperia spp. cumulative faecal egg counts, the results obtained in sheep demonstrated that dd-Co-ASP was ineffective in raising a protective immune response against a C. curticei challenge infection. Even though sequence analysis of the dd-Co-ASP gene revealed restricted sequence heterogeneity in the double domain ASP within and between bovine Cooperia species, the results of the vaccine study suggest that there is sufficient conservation at the protein level to yield cross-protection, holding promise for the development of a general Cooperia vaccine for use in cattle.

Nematode Identification Techniques and Recent Advances

Nematodes are among the most diverse but least studied organisms. The classic morphology-based identification has proved insufficient to the study of nematode identification and diversity, mainly for lack of sufficient morphological variations among closely related taxa. Different molecular methods have been used to supplement morphology-based methods and/or circumvent these problems with various degrees of success. These methods range from fingerprint to sequence analyses of DNA- and/or protein-based information. Image analyses techniques have also contributed towards this success. In this review, we highlight what each of these methods entail and provide examples where more recent advances of these techniques have been employed in nematode identification. Wherever possible, emphasis has been given to nematodes of agricultural significance. We show that these alternative methods have aided nematode identification and raised our understanding of nematode diversity and phylogeny. We discuss the pros and cons of these methods and conclude that no one method by itself provides all the answers; the choice of method depends on the question at hand, the nature of the samples, and the availability of resources.

A Revised Checklist of Cooperia Nematodes (Trichostrogyloidea), Common Parasites of Wild and Domestic Ruminants

This review updates the current knowledge on the taxonomy of intestinal nematodes of the genus Cooperia parasitizing in wild and domestic ruminants. The emphasis is put on revision of 19 valid species belonging to the genus. This analysis focuses on main features of the genus Cooperia, including its geographic occurrence and the life cycle details. The most widespread congeners are Cooperia curticei, C. oncophora, C. pectinata, and C. punctata, having nearly worldwide distribution. The fifth species, referred by electronic databases from the European territory as Cooperia asamatiSpiridonov, 1985, is unveiled here originally as nomen nudum.

Implication of the fecal egg count reduction test (FECRT) in sheep for better use of available drugs

Abstract The aim here is to present data on the efficacy of anthelmintics in sheep flocks in Rio de Janeiro, Brazil, and to discuss the interpretation of the fecal egg count reduction test (FECRT) for each nematode genus. Fecal eggs counts and pre- and post-treatment coprocultures were performed, the former to evaluate the efficacy of and the latter to determine the overall parasite prevalence. An additional efficacy test was performed at Farm # 1 a year after the initial test. Severe anthelmintic resistance was found for the flocks, with no FECRT sensitivity at any of the 22 farms evaluated. However, an analysis of the infective larvae showed that some drugs were effective against certain parasitic genera; i.e., levamisole was more effective against Haemonchus spp. and moxidectin against Trichostrongylus spp. In the additional FECRT performed at Farm # 1, moxidectin and nitroxynil were ineffective separately, but when applied in combination they were highly effective due to their efficacy against Haemonchus (nitroxynil) and Trichostrongylus (moxidectin), respectively. The use of the FECRT targeting the parasitic nematode species prevalent on farms may make it possible to choose more effective anthelmintics.

Mitochondrial genome evidence suggests Cooperia sp. from China may represent a distinct species from Cooperia oncophora from Australia

Cooperia spp. are parasitic nematodes parasitizing in small intestine of ruminants with a worldwide distribution. Infection of ruminants with Cooperia species can cause severe enteritis, causing significant socio-economic losses to the livestock industry. However, it is yet to know whether there is genetic diversity in mitochondrial (mt) DNA sequences of Cooperia nematodes from different geographic regions. The objective of the present study was to examine sequence difference in mt genomes between Cooperia sp. from China and other Cooperia species. We determined the sequences of the internal transcribed spacer (ITS-1 and ITS-2) of nuclear ribosomal DNA (rDNA) of 11 Cooperia specimens collected from the small intestine of a Tianzhu White yak in Gansu Province, northwestern China, which had 99% similarity with that of C. oncophora from Brazil (GenBank accession Number: AJ544290) in ITS-1, and 99% similarity with those from Denmark (AB245040), Scotland and Australia (AJ000032) in ITS-2, indicating that specimens used in the present study should at least represent parasites in Cooperia. We then determined the complete mt genome sequences of one representative specimen of Cooperia sp. from China (CspC), compared the mt DNA sequences with that of C. oncophora from Australia (COA, GQ888713), and conducted phylogenetic analysis with selected nematodes using both maximum likelihood (ML) and Bayesian inference (BI) methods based on both concatenated 12 PCGs, rrnL and rrnS sequences and partial cox2 sequences. The complete mt genome sequence of CspC (KY769271) is 13, 583 bp in length, which is 91 bp shorter than that from COA. The sequence difference over the entire mt genome between CspC and COA was 12.2% in nucleotide and 6.3% in inferred amino acids, with nad4L and nad1 being the most variable and the most conserved PCGs, respectively. Phylogenetic analysis indicated that CspC and COA were closely-related but distinct taxa. The determination of mt genome sequences for Cooperia sp. from China also provides novel resources for further studies of taxonomy, systematics and population genetics of Cooperia from different geographical locations.

PCR primers for straightforward differentiation of Haemonchus contortus, Haemonchus placei and their hybrids

Haemonchus contortus and Haemonchus placei are among the major parasites of small ruminants and cattle. Although infection with these nematodes is host-specific, with H. placei predominating in cattle and H. contortus in sheep, cross-infections are observed in areas where both parasites are sympatric, and hybrid offspring can occur. Therefore, a fast and precise method is required for differentiating the parasites. Identification based on spicule morphometry is the most common technique for differentiating Haemonchus species. However, because these measurements overlap between species, morphological analysis is insufficient for differentiating between helminth species. In this work, we present a reliable, conventional polymerase chain reaction (PCR)-based method that uses two species-specific primer pairs to differentiate between H. contortus and H. placei specimens and their hybrids. Each primer pair produces one single and distinct amplification band for each species, which enables the detection of hybrid specimens. These primer pairs were validated by testing eight different populations of H. contortus, H. placei and hybrids.

Overview of anthelmintic resistance of gastrointestinal nematodes of small ruminants in Brazil

Abstract Frequent and inappropriate use of all classes of antiparasitic drugs in small ruminants has led to failures in their effectiveness, culminating in a global problem of anthelmintic resistance. Brazil stands out as one of the world’s leaders in publications about anthelmintic resistance, and for having the most numerous reports of this resistance in small ruminants in the Americas. These studies have involved mainly the fecal egg count reduction test (FECRT) and its correlation with field management practices. In vivoeffectiveness testing is conducted in areas where livestock is of greater economic significance, e.g., in the South (sheep) and Northeast (goats), or is important for research and economic centers, such as the Southeast (sheep). The most widely studied species is sheep, for which the widest range of drugs is also evaluated. Despite significant advances achieved in molecular research, laboratory analyses should include knowledge about the reality in the field so that they can become feasible for the producer. Moreover, molecular studies can be underpinned by the analysis of field studies, such as the maintenance of antiparasitic effectiveness over time and the mechanisms involved in this process.