Ovine ß-globin gene: A new qPCR for rapid haplotype identification and association with susceptibility to Haemonchus contortus infection.

Two ß-globin allelic haplotypes (A and B) were identified in domestic sheep, wherein animals which are homozygous for ßB allele (BB haplotype) have a deletion of pre-adult ßC-globin and consequently are less tolerant to anemia and hypoxia. Since Haemonchus contortus infection, is associated with severe anemia, studies performed from 1960s to 1990s investigated the association between ß-globin haplotype and resistance against this parasite. However, the findings were controversial, pointing out from increased resistance in animals harboring the ßA allele to inexistence of association. Thus, our study aimed to develop a qPCR for ß-globin haplotype identification, and to evaluate the association between ß-globin haplotype and resistance against H. contortus in a group of sheep submitted to artificial infection with this parasite. A total of 286 lambs of Morada Nova breed were experimentally challenged with 4000 H. contortus L3 and monitored for 112 days from weaning. Significantly improved (p < 0.05) phenotypic profiles (lower fecal egg counts, higher packed cell volume and birthweight) were observed for AA haplotype animals, especially when compared to BB animals, while AB animals were similar to BB. This is the first report of a qPCR assay for ovine ß-globin haplotype identification. In view of significant differences of phenotypic profiles between haplotype groups, the developed qPCR may constitute an important tool for sheep producers to improve genetic selection of parasite resistant animals.

Local and systemic immune mediators of Morada Nova lambs with divergent Haemonchus contortus resistance phenotypes.

AIMS: Local and systemic immune mediators of Morada Nova lambs with divergent Haemonchus contortus resistance phenotypes were evaluated. METHODS AND RESULTS: Lambs were ranked through faecal egg counts (FEC) after two parasitic challenges with 4,000 H.contortus L3 . After the second challenge, the lambs underwent a third artificial infection and were euthanized 7 days later. Immune-related genes were quantified locally in abomasal mucosa and lymph nodes (CD4, IFNγ, IL4, IL5, IL13, IL2RA and MS4A2) and systemically in the whole blood (IL4 and IL13). Anti-H. contortus IgG and IgA antibodies and eosinophils and mast cells counts were also investigated. Resistant animals presented higher systemic IgG and IgA titres, both negatively correlated with FEC. Susceptible animals had higher blood levels of IL4 transcripts. At the local level, resistant lambs had higher eosinophils counts and superior MS4A2 levels in abomasal fundic mucosa, besides higher IgA levels in abomasal mucus, while susceptible lamb had superior IL4 expression in abomasal lymph nodes. CONCLUSION: These data indicate that resistant lambs had an immune response mediated by antibody-mediated cytotoxicity. Also, the systemic humoral profile, particularly IgA isotype, seems to be a good resistance marker for Morada Nova sheep, as we found differences between groups even when FEC did not differ.

Viability of Haemonchus placei parasitism in experimentally infected young goats.

The present study aimed to evaluate the viability of Haemonchus placei parasitism in experimentally infected goats. For that, 14 75 days old kids male Saanen kids were placed in one of the four experimental groups: GI - infected with 5000 H. placei L3 (n = 4); GII - infected with 5000 H. contortus L3 (n = 4); GIII - infected with 2500 H. contortus L3 + 2500 H. placei L3 (n = 4), and GIV - control, inoculated with distilled water (n = 2). Each kid received, orally, the infective dose in a single inoculum. Based on daily fecal egg counts, the average pre-patent period was determined as 24 days for H. contortus, and 31 days for H. placei. Regarding the Haemonchus spp. recovered at necropsy, the experimental groups GI, GII, and GIII had, respectively, an average of 25.5, 619.5, and 724.75 (120 H. placei, and 604.75 H. contortus) adult specimens, and no immature forms. Under the conditions of this study, the viability of goat infection by H. placei was confirmed, although, with low susceptibility. Nevertheless, the parasitism of this helminth species was more intense when associated with H. contortus. This fact indicates that in common grazing between cattle and young goats, when the latter end up ingesting both Haemonhcus species, especially in a mixed infection, H. placei may also parasitize them.