New kit offers rapid SRS detection on the farm
A recently developed on-farm detection kit for piscirickettsiosis (SRS) can confirm the bacteria’s presence within 90 minutes and might help reduce the impact of a disease that costs the Chilean salmon industry US$750 million a year.
Piscirickettsia salmonis is the bacterial agent causing piscirickettsiosis, a disease responsible for both direct losses caused by fish mortalities and indirect losses, for example by degrading quality due to skin injuries.
These losses cost the Chilean salmonid farming sector up to $750 million per year. SRS is also a problem in Canada, and last year there was an incidence in Ireland.
No successful vaccine
Three decades have passed since P. salmonis was first discovered in Chilean salmon and there is no successful vaccine yet against either of its two most frequent strains (LF-89 and EM-90). Consequently, most treatments involve the antibiotics florfenicol or oxytetracycline. However, use of different preventive measures in recent years, such as probiotics, and improved smolt quality and farming practices, have helped to reduce antibiotic dependence.
Now an on-farm detection kit has been developed which can diagnose the disease within 90 minutes, without lab equipment or highly qualified staff. Moreover, the portable kit reduces the number of trips from sites to labs for analysis, and therefore help farms maintain social distancing during the Covid-19 pandemic.
On-farm kit
WikiGen SRS is a molecular kit for the qualitative detection of P. salmonis by means of an isothermal nucleic acid amplification method with polymerases and recombinases, followed by development by lateral flow assay.
Marco Rozas, founder and technical director at Newenko Group, the company that developed the test, said the kit is much more rapid than sending a sample to a laboratory and can lead to timely and effective treatment and thus reduce mortalities.
“You can obtain results after 90 minutes with WikiGen, versus 7,200 minutes (five days) in a lab. Then, if you treat quickly, there are more chances for the fish to consume medicated feed, which increases the possibility of obtaining an effective therapy. By contrast, if you arrive late, the fish have lost their appetite and in-feed treatment is wasted. The medicine is also more likely to pass into the marine sediment,” he explained.
91% sensitivity
According to Rozas, compared to lab analysis using techniques such as Elisa and PCR, this kit detects SRS with 91% of sensitivity and specificity, and an accuracy of 90%. It is also able to recognise both LF-89 and EM-90 strains.
“What is most significant in the current pandemic, is that this kit can be used by any official or technician at the farm, thus providing an effective and efficient solution and allowing control measures to be applied in a timely manner,” Rozas said.
