Aquaculture is a growth industry and presents an opportunity for diversifying Michigan’s economy. Yet, viruses can kill up to 30 percent of hatchery fish.
When enough people or livestock are vaccinated against a contagious disease, they protect others in the community, an effect known as "herd immunity." Now, Dr. Mohammed Faisal, his graduate student Isaac Standish, and others in the Department of Pathobiology and Diagnostic Investigation have evidence that herd immunity may work in commercial aquaculture, where disease can severely reduce productivity and profits.
Muskellunge, the popular and lucrative Great Lakes game fish, are extremely vulnerable to a common virus, especially in the close quarters of commercial hatcheries. But Standish and his colleagues show for the first time that “muskies” developed immunity following exposure to vaccinated fish. “This provides us an excellent opportunity,” Standish says. “First, we show that immunity can be artificially elicited through vaccination. Then, we demonstrate that a herd response is plausible for aquatic systems.”
Herd immunity is a well-known concept in human medicine. For example, when polioviruses ravaged the US, 100 percent herd immunity was accomplished with only a 65–70 percent of immunization coverage in North America. This critical threshold has been studied for many pathogens, such as smallpox. Until now, little work has been done on aquatic pathogens.
In MSU’s Aquatic Animal Health Laboratory, Standish found that unvaccinated fish stocked with vaccinated fish averaged a mortality rate of 36 percent. However, unvaccinated muskellunge housed alone had an average mortality rate of 80 percent, and vaccinated muskellunge stocked alone experienced a 3 percent mortality rate.
"This work has broad ramifications," says Faisal, who directs the Lab. “This is a milestone toward our understanding of immune response of aquatic animals at the population level. It also is of importance for vaccine administration.” Next steps would involve determining the mechanism of herd immunity on other aquatic species, examining whether protection works with other pathogens, and stocking vaccinated hatchery fish in public water as a means of conferring immunity to wild fish.
Read the full-text article here:
https://www.ncbi.nlm.nih.gov/pubmed/27854310
Int J Mol Sci. 2016 Nov 15;17(11). pii: E1898. Does Herd Immunity Exist in Aquatic Animals? Standish IF1, Brenden TO2, Faisal M3,4.
Read more about research on developing vaccines to control disease in aquaculture here.