title: Does Herd Immunity Exist in Aquatic Animals?
abstract: Viral hemorrhagic septicemia virus genotype IVb (VHSV-IVb) is presently found throughout the Laurentian Great Lakes region of North America. We recently developed a DNA vaccine preparation containing the VHSV-IVbglycoprotein(G) gene with a cytomegalovirus (CMV) promoter that proved highly efficacious in protecting muskellunge (Esox masquinongy) and three salmonid species. This study was conducted to determine whether cohabitation of VHSV-IVb immunized fishes could confer protection to non-vaccinated (i.e., naïve) fishes upon challenge. The experimental layout consisted of multiple flow-through tanks where viral exposure was achieved via shedding from VHSV-IVb experimentally infected muskellunge housed in a tank supplying water to other tanks. The mean cumulative mortality of naïve muskellunge averaged across eight trials (i.e., replicates) was significantly lower when co-occurring with immunized muskellunge than when naïve muskellunge were housed alone (36.5% when co-occurring with vaccinated muskellunge versus 80.2% when housed alone), indicating a possible protective effect based on cohabitation with vaccinated individuals. Additionally, vaccinated muskellunge when co-occurring with naïve muskellunge had significantly greater anti-VHSV antibody levels compared to vaccinated muskellunge housed alone suggesting that heightened anti-VHSV antibodies are a result of cohabitation with susceptible individuals. This finding could contribute to the considerably lower viable VHSV-IVb concentrations we detected in surviving naive muskellunge when housed with vaccinated muskellunge. Our research provides initial evidence of the occurrence of herd immunity against fish pathogens.
authors.affiliation: Department of Pathobiology and Diagnostic Investigation, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48824, USA. standi13@msu.edu.
authors.forename: Isaac F
authors.initials: IF
authors.lastname: Standish
authors.affiliation: Department of Fisheries and Wildlife, College of Agriculture and Natural Resources, Michigan State University, East Lansing, MI 48824, USA. brenden@msu.edu.
authors.forename: Travis O
authors.initials: TO
authors.lastname: Brenden
authors.affiliation: Department of Pathobiology and Diagnostic Investigation, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48824, USA. faisal@cvm.msu.edu.|Department of Fisheries and Wildlife, College of Agriculture and Natural Resources, Michigan State University, East Lansing, MI 48824, USA. faisal@cvm.msu.edu.
authors.forename: Mohamed
authors.initials: M
authors.lastname: Faisal
mesh_terms: D000818:Animals; D000914:Antibodies, Viral / Q000096:biosynthesis; D003587:Cytomegalovirus / Q000737:chemistry / Q000235:genetics; D017859:Esocidae; D005393:Fish Diseases / Q000276:immunology / Q000401:mortality / Q000517:prevention & control* / Q000821:virology; D015870:Gene Expression; D006023:Glycoproteins / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology; D006114:Great Lakes Region; D032521:Immunity, Herd; D029141:Novirhabdovirus / Q000276:immunology*; D011401:Promoter Regions, Genetic; D018353:Rhabdoviridae Infections / Q000276:immunology / Q000401:mortality / Q000517:prevention & control* / Q000662:veterinary*; D016019:Survival Analysis; D019444:Vaccines, DNA / Q000008:administration & dosage / Q000096:biosynthesis*; D019562:Viral Load / Q000187:drug effects; D014764:Viral Proteins / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology; D014765:Viral Vaccines / Q000008:administration & dosage / Q000096:biosynthesis*
chemical_list: D000914:Antibodies, Viral; D006023:Glycoproteins; D019444:Vaccines, DNA; D014764:Viral Proteins; D014765:Viral Vaccines
keywords: DNA vaccine; fish; herd immunity; muskellunge