title: Can Haemonchus placei-primary infected naïve lambs withstand Haemonchus contortus infections?
abstract: An experiment was conducted with the objective of evaluating whether a 5000 L3 larvae Haemonchus placei primary infection, a less pathogenic parasite species for sheep, could attenuate highly pathogenic Haemonchus contortus infections in lambs. Thirty nine 6-month-old lambs were divided in three primary-infection groups: (HcPI) H. contortus-primary infected lambs, (HpPI) H. placei-primary infected lambs, and (CTRL) non-infected control lambs. Later, these same individuals, then aged 10-month old, were cross challenged with Haemonchus parasite species, creating four groups: HcPI challenged with H. placei (HcPI-HpCH), HpPI challenged with H. contortus (HpPI-HcCH), HcPI challenged with H. contortus (HcPI-HcCH), and CTRL. After a 60-day challenge period, all animals were necropsied for gastrointestinal worm counts. HcPI faecal egg count average was found to be twice the HpPI FEC group (p<0.0001). The HcPI also showed lower packed cell volume averages compared to the other groups (p<0.0001). Both H. contortus- and H. placei-primary infections displayed immune responses with similar IgG levels. For the challenge trial, the larval doses used were not enough to trigger clinic infection signs in all treated groups, compared to controls, and H. placei primary infection was not able to maintain anti-H. contortus IgG levels in a subsequent H. contortus infection.
authors.affiliation: Centro de Ciências Rurais, Universidade da Região da Campanha, Bagé, RS, Brazil.
authors.forename: Regina Celis Pereira
authors.initials: RCP
authors.lastname: Reiniger
authors.affiliation: Programa de Pós Graduação em Veterinária, Universidade Federal de Pelotas, RS, Brazil.
authors.forename: Luciana Laitano
authors.initials: LL
authors.lastname: Dias de Castro
authors.affiliation: EMBRAPA, Brazil. Electronic address: magda.benavides@embrapa.br.
authors.forename: Magda Vieira
authors.initials: MV
authors.lastname: Benavides
authors.affiliation: Instituto de Biologia, Departamento de Microbiologia e Parasitologia, Universidade Federal de Pelotas, RS, Brazil.
authors.forename: Maria Elisabeth Aires
authors.initials: MEA
authors.lastname: Berne
mesh_terms: D000818:Animals; D005243:Feces / Q000469:parasitology; D006188:Haemonchiasis / Q000276:immunology / Q000469:parasitology / Q000662:veterinary*; D006189:Haemonchus / Q000145:classification* / Q000276:immunology; D010270:Parasite Egg Count / Q000662:veterinary; D012756:Sheep; D012757:Sheep Diseases / Q000276:immunology / Q000469:parasitology*
keywords: Cross infection; Haemonchus species; Primary-infection; Sheep