title: Attempts to vaccinate ewes and their lambs against natural infection with Haemonchus contortus in a tropical environment.
abstract: A vaccine containing integral membrane glycoproteins from the intestine of Haemonchus contortus was evaluated in three groups of grazing sheep each containing 13 ewes and their 16 lambs naturally infected with gastrointestinal nematodes. Two groups were vaccinated with either 5 or 50μg of the antigen per immunisation, while the third, the control group, received adjuvant alone. The sheep were immunised six times at 3week intervals, partly because the vaccine antigens are hidden and thus no immunological boost would be delivered by subsequent infection and partly because the level of Haemonchus spp. challenge was expected to be high. The vaccinated ewes, first immunised approximately 1month before lambing, showed a circulating antibody response but no signs of reduced anaemia or Haemonchus spp. egg counts, compared with control ewes. Several ewes with severe haemonchosis in all three groups had to be given precautionary treatment with anthelmintic drugs. In contrast, vaccinating their lambs with either 5 or 50μg of the antigen per immunisation resulted in 10 fold higher antibody titres. In the case of the lower antigen dose this was associated with significantly less anaemia, 72% reduction in the overall number of Haemonchus spp. eggs produced and significantly fewer worms compared with control lambs. It is hypothesised that the heavily pregnant or lactating ewes did not have sufficient physiological reserves to mount a protective response following vaccination in the tropical weather and high challenge conditions that prevailed. Nevertheless, the vaccine could afford useful protection for lambs against H. contortus.
authors.affiliation: UNESP - Universidade Estadual Paulista, Departamento de Parasitologia, Instituto de Biociências, Caixa Postal 510, Botucatu, SP CEP 18.618-000, Brazil. Electronic address: bassetto@ibb.unesp.br.
authors.forename: C C
authors.initials: CC
authors.lastname: Bassetto
authors.affiliation: UNESP - Universidade Estadual Paulista, Departamento de Parasitologia, Instituto de Biociências, Caixa Postal 510, Botucatu, SP CEP 18.618-000, Brazil.
authors.forename: M É
authors.initials: MÉ
authors.lastname: Picharillo
authors.affiliation: Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik, EH26 0PZ Edinburgh, UK.
authors.forename: G F J
authors.initials: GF
authors.lastname: Newlands
authors.affiliation: Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik, EH26 0PZ Edinburgh, UK.
authors.forename: W D
authors.initials: WD
authors.lastname: Smith
authors.affiliation: UNESP - Universidade Estadual Paulista, Departamento de Produção Animal, Faculdade de Medicina Veterinária e Zootecnia, Fazenda Experimental Lageado, Botucatu, SP CEP 18.618-000, Brazil.
authors.forename: S
authors.initials: S
authors.lastname: Fernandes
authors.affiliation: UNESP - Universidade Estadual Paulista, Departamento de Produção Animal, Faculdade de Medicina Veterinária e Zootecnia, Fazenda Experimental Lageado, Botucatu, SP CEP 18.618-000, Brazil.
authors.forename: E R
authors.initials: ER
authors.lastname: Siqueira
authors.affiliation: UNESP - Universidade Estadual Paulista, Departamento de Parasitologia, Instituto de Biociências, Caixa Postal 510, Botucatu, SP CEP 18.618-000, Brazil.
authors.forename: A F T
authors.initials: AF
authors.lastname: Amarante
mesh_terms: D000818:Animals; D000909:Antibodies, Helminth / Q000097:blood; D000947:Antigens, Helminth / Q000008:administration & dosage / Q000276:immunology; D001938:Brazil; D005243:Feces / Q000469:parasitology; D005260:Female; D005767:Gastrointestinal Diseases / Q000276:immunology / Q000469:parasitology / Q000517:prevention & control / Q000662:veterinary*; D006188:Haemonchiasis / Q000276:immunology / Q000469:parasitology / Q000517:prevention & control / Q000662:veterinary*; D006189:Haemonchus / Q000276:immunology*; D006400:Hematocrit / Q000662:veterinary; D010270:Parasite Egg Count / Q000662:veterinary; D012756:Sheep; D012757:Sheep Diseases / Q000276:immunology / Q000469:parasitology* / Q000517:prevention & control*; D018709:Statistics, Nonparametric; D014329:Tropical Climate; D014612:Vaccines / Q000008:administration & dosage* / Q000276:immunology
chemical_list: D000909:Antibodies, Helminth; D000947:Antigens, Helminth; D014612:Vaccines
keywords: Antibodies; Gastrointestinal nematodes; Haemonchus; Protective antigens; Sheep; Tropical environment; Vaccine