Humoral response to West Nile virus vaccination in alpacas and llamas.
OBJECTIVE
To determine humoral responses to an equine West Nile virus (WNV) vaccine in healthy alpacas and llamas and compare responses in alpacas and llamas with responses in horses.


METHODS
Clinical trial.


METHODS
28 alpacas, 56 llamas, and 16 horses.


METHODS
Horses received 2 vaccinations at 4-week intervals, and alpacas and llamas received 3 vaccinations at 3-week intervals. Fifty-five llamas received a fourth vaccination 3 weeks after the third. Blood samples were collected immediately prior to each vaccination, 3 weeks after the last vaccination for alpacas and llamas, and 4 weeks after the last vaccination for horses and tested for virus-neutralizing antibodies. Samples from 29 randomly selected vaccinated llamas were used.


RESULTS
None of the animals developed any local or systemic adverse reactions. Four of 28 (14%) alpacas, 4 of 29 (14%) llamas, and 7 of 16 (44%) horses were seropositive 3 (llamas and alpacas) or 4 (horses) weeks after administration of the first vaccination; 27 of 28 (96%) alpacas, 26 of 29 (90%) llamas, and 15 of 16 (94%) horses were seropositive after administration of the second vaccination; and all 28 alpacas and 28 of 29 (97%) llamas were seropositive 3 weeks after administration of the third vaccination.


CONCLUSIONS
Results suggest that vaccination with the equine WNV vaccine is safe in alpacas and llamas. Administration of 3 vaccinations generally resulted in virus-neutralizing antibody titers similar to those observed following 2 vaccinations in horses; however, because it is not known what antibody titer would be protective against clinical WNV disease in alpacas or llamas, we cannot conclude that the vaccine was efficacious.
Department of Clinical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis, OR 97331, USA.
Michelle A
MA
Kutzler
Rocky J
RJ
Baker
Donald E
DE
Mattson
D000818:Animals; D000914:Antibodies, Viral / Q000096:biosynthesis* / Q000097:blood; D002161:Camelids, New World / Q000276:immunology* / Q000821:virology; D005260:Female; D006734:Horse Diseases / Q000276:immunology / Q000517:prevention & control*; D006736:Horses; D008297:Male; D009500:Neutralization Tests / Q000662:veterinary; D011897:Random Allocation; D012449:Safety; D013997:Time Factors; D014611:Vaccination / Q000662:veterinary; D015164:Vaccines, Inactivated / Q000008:administration & dosage; D014765:Viral Vaccines / Q000008:administration & dosage / Q000276:immunology*; D014901:West Nile Fever / Q000276:immunology / Q000517:prevention & control / Q000662:veterinary*; D014902:West Nile virus / Q000276:immunology*
D000914:Antibodies, Viral; D015164:Vaccines, Inactivated; D014765:Viral Vaccines