Comparison of ovine β-globin haplotype sequences and a new multiplex PCR for identification

Deletion of pre-adult β^C-globin in sheep harboring BB haplotype of β-globin was associated to decreased tolerance to anemia and hypoxia, and consequently, reduced resistance to Haemonchus contortus infection, which is closely related to severe anemia. Recently, a qPCR using hydrolysis probe was successfully developed for β-globin haplotype identification, and association between resistance against H. contortus and presence of β^A allele was observed in Morada Nova sheep. Thus, this study aimed to better investigate the differences between β-globin haplotypes and to develop a conventional multiplex PCR, as an alternative to qPCR assay for β-globin haplotype identification. A total of 333 Morada Nova lambs had their blood collected and tested by both qPCR and new multiplex PCR, and 100 % of agreement was observed between the results. Since different primers were designed for such assay development, including different target genes, high specificity of both methods may be also highlighted. Three A haplotype samples were submitted to DNA Sanger sequencing of β-globin gene and compared to sequences previously deposited in Genbank. One nucleotide deletion in intronic region was observed only in AA haplotype of Morada Nova animals, while in BB animals the nucleotide remained present. To the best of our knowledge, this is the first report of multiplex conventional PCR for ovine β-globin haplotype identification. The advantages of the developed conventional PCR are reduced reagents costs (less than a half price) and wider reachability, since even labs without real time PCR thermocyclers are able to offer this assay. Therefore, it may become an important tool for sheep producers to improve genetic selection of parasite resistant animals.

Medicinal plant extracts and nematode control

Abstract

Several aspects should be taken into consideration in relation to the use of active botanical extracts or compounds in parasite control: extraction, conservation, phytochemical study, determination of lethal concentration in vitro, toxicity to the host, effective dose in vivo, residual period, stability, residues/metabolites generated and costs. The in vitro tests that have been used to screen biological activity were developed to detect parasite resistance to anthelmintics. In this way, the effects of a potent plant extract can be underestimated or dismissed if the selected methods disregard some factors that can influence the results, such as solubility or an indirect effect on the nematode. Despite this, the development of strategies that are less dependent on in vivo testing is important. There is a need for fuller investigations not restricted only to indicating whether or not a phytotherapy was effective against parasites. The divergence between efficacy in vitro and inefficacy in vivo can be attributed to key factors related to bioavailability as well as pharmacology of the botanical substances in the host organism. It is important to focus studies to determinate the most appropriate adjuvants and to develop formulation models that can be adapted according to the nature of the plant extract or bioactive compound isolated, to serve as starting points for the development of semi-synthetic and synthetic substances.

In vitro anthelmintic activity of aqueous leaf extract of Annona muricata L. (Annonaceae) against Haemonchus contortus from sheep

Despite the overall progress of sheep farming in Brazil, infections with the gastrointestinal parasite Haemonchus contortus represent one the most important problems in sheep production, aggravated by the increasing resistance of nematodes to traditional anthelmintic drugs caused by inadequate sheep flock management by breeders. Ethnopharmacological data indicate Annona muricata as a promising alternative for the control of gastrointestinal nematodes because of its general anthelmintic properties. The aim of this work was to evaluate the in vitro anthelmintic effects of A. muricata aqueous leaf extract against eggs, infective larvae and adult forms of parasitic nematode H. contortus. At higher doses, A. muricata extract showed 84.91% and 89.08% of efficacy in egg hatch test (EHT) and larval motility test (LMT), respectively. In the adult worm motility test, worms were completely immobilized within the first 6-8h of nematode exposition to different dilutions of extract. Phytochemical analysis indicated the presence of phenolic compounds in A. muricata aqueous leaf extract that may be responsible for the anthelmintic effects observed. Moreover those results validate the traditional use of A. muricata as a natural anthelmintic and then the pharmacological potential of its compounds for future in vivo investigations.