CIFA ArguVax- 1

Background

One of the major problems in freshwater carp aquaculture is the production loss due to the branchiuran ectoparasite Argulus sp., also called as ‘Fish Lice’; which is an economically important pathogen of finfish in temperate and tropical waters. An average loss of 29,524.40 INR/ha/yr was estimated in the year 2013 to occur due to an argulosis outbreak in Indian major carp farming (Sahoo et al., 2013). Hence, in that scenario, a loss to the tune of INR 300 crores is estimated to be incurred due to this parasite in a year in India. Control of Argulus sp. is achieved by routine applications of chemical pesticides including organophosphates or synthetic pyrethroids. The damaging effect of these chemicals on the environment and wildlife has already been recognized. Also, there is an increasing concern over the impact of these pesticides on human health. Moreover, these chemicals do not prevent infection in carp farms on a long-term basis and sometimes their repeated use might lead to resistance in Argulus sp. Therefore, there has been a need to find better ways of minimizing production losses due to argulosis. Control by vaccination could provide an effective and safe alternative to these harmful chemicals. Once developed, a vaccine against Argulus would address the problem by providing fish with immunity against the parasite, thus reducing infestations and improving the associated economic and environmental impacts.

            The anticipated market size of a vaccine against argulosis is huge considering the requirements in India and worldwide. Let’s take into consideration of only rohu (Labeo rohita) in India as per 2023 data of ~8 million tonnes carp production (Handbook on Fisheries Statistics, 2023). Rohu production from aquaculture will be ~3.84 million tonnes (80% from aquaculture & 60% cultured are rohu). Thus, approximately 548 crores of fingerlings will be required to reach this production at an average 1 kg grow-out each with 70% survival and hence, that is the scope for CIFA: ArguVax-I annually. The vaccine also has wider options, if other affected species are taken into account globally.

Technology Details

Vaccination seems an effective and efficient alternative to control argulosis as it has been proven in many other infectious diseases. However, the identification of a protective antigen is crucial for any vaccine development process. The present invention thus focused on identifying a suitable vaccine candidate antigen from Argulus siamensis proteins by immunoproteomics approach. A number of immunogenic proteins were identified and subsequently, a 19 mer peptide was designed from one of those proteins by bioinformatics analyses. The peptide was outsourced for chemical synthesis and conjugation to KLH (keyhole limpet hemocyanin). The conjugated peptide along with Freund’s incomplete adjuvant (FIA) were applied as vaccine in rohu (L. rohita) in injection mode. The vaccinated fish were boostered similarly after day 14 and when challenged with live A. siamensis parasites, showed protection (reduction in parasite load and mortality). Later on, the vaccine was tried in immersion mode (without any adjuvant) in rohu, considering its applicability in mass vaccination that also showed protection as above. The vaccine was finally evaluated in rohu immersion-vaccinated along with montanide adjuvant (Seppic, France) in wet laboratory and, reared and co-habitation challenged with parasites in outdoor pond conditions. The vaccinated fish showed significantly reduced parasite burden (>70%) up to a period of >6 months.  Thus, it is recommended to use the vaccine in immersion mode along with montanide adjuvant in rohu.

The developed vaccine is completely a new product as the peptide sequence used is novel and it has shown effective as a vaccine in rohu against A. siamensis parasites. The main features and benefits of the invention are its higher efficacy against Argulus parasites on one hand and no adverse effects on aquatic lives as well as the environment on the other, unlike the chemicals routinely used for control of the parasites. Also, the vaccine is safe and effective for the host with no possibility of developing resistance in the parasite. Further, the developed vaccine provides a long period (≥ 6 months) of protection in carps against the Argulus parasite and, thus would reduce the economic loss to the fish farmers.