A novel yet simple method of producing oral vaccine for fish could become a crucial innovation in the way vaccines are administered to fish, especially tilapia.

By Melpha Abello

A research team led by Dr. Anacleto M. Argayosa, assistant professor at the Institute of Biology of the University of the Philippines Diliman, has developed a fish oral vaccine with a nanocomposite biomaterial as a carrier for improved vaccine delivery.

The research was titled, “Clay micro encapsulation of gamma-irradiated Aeromonas hydrophila for fish oral vaccine development,” and funded by the Philippine Council for Agriculture, Aquatic and Natural Resources Research and Development of the Department of Science and Technology.

The research team also included Chelo Pascua, Florentino Sumera, Anthony Yason, and Alpha Espigar.

According to Argayosa, oral vaccination is considered the most desirable method of immunizing fish due to the following advantages: it is non-invasive; there is no need to handle the fish; it is easily administered; it is suitable for mass immunization; and it has potential applications for other animal species.

The major problem in the development of oral vaccine for fish, however, is the degradation of the antigens in the stomach due to acidity (low pH) and digestive enzymes.
This, says Argayosa, reduces the efficacy of the oral vaccine below its desired level.

The challenge, Argayosa says, is how to keep the antigens intact as it reaches the immunization site (hind gut).

This was addressed by inactivation and clay microencapsulation of the antigen using biocomposite nano particles such as layered silicate with plate thickness of 1 nanometer (nm) and surface dimension of 300-600 nm. Argayosa says that the biocomposite nano particles
could withstand the stomach environment of the fish and deliver the antigens to target gut-associated lymphoid tissues, inducing mucosal and systemic immune response, that ultimately prevent morbidity or mortality in orally vaccinated fish.

The vaccine can be dressed onto fish pellets to make administration easier, Argayosa says.

Worldwide, the Philippines is the fourth largest tilapia producer. In 2012, the country produced 260,500 tons of tilapia valued at 10 billion.

However, the country could have produced more tilapia if not for the losses caused by mortalities. In the case of Taal Lake— whose annual stocking rate of 600 million fry ranks it among the major producers of tilapia in the country—the mortality rate is high at 50 percent in the first month of rearing. At 0.50/fry, this is equivalent to a 150 million potential loss in fry cost in Taal Lake alone per year. Argayosa reports that among the causes of mortality is bacterial infection by pathogen Aeromonas spp., which can be addressed through oral vaccination.

Last year, Argayosa’s research on the production of oral fish won the National Prize of the 2013 Ambassador Alfredo M. Yao Intellectual property awards.

“The science and technology of oral vaccine is simple yet promises innovative production engineering and various applications waiting to be explored for animal and human health,” says Argayosa.

The research team is now working on the transfer of the technology to the commercial sector, hoping that it will attract investment from the government and the private sector. For the
protection of oral fish vaccine technology, a Philippine patent application has been filed by the office of vice-chancellor for research and development.

This story appeared in Agriculture Monthly’s June 2014 issue.