Colombia has warned of a health emergency in tilapia, for which authorities have already ordered 400,000 vaccines to contain the Streptococcus agalactiae ST7 bacteria.
Suspicions began to arise with the increase in farm mortality until June 8, when the Colombian Agricultural Institute (ICA) confirmed the presence of Streptococcus aglactiae ST7 bacteria in tilapia farms in different areas of the country. So far, total of 43 outbreaks have been reported, for which the government has taken action following the increase of the first 29 reported outbreaks.
"Since last March, we were facing a mortality that was out of the average from year to year," explained Juan Fernando Roa Ortiz, manager of the ICA. For this reason, a health emergency was declared "to take all the necessary measures as sanitary authority to reduce the impact of fish mortality".
With the sanitary emergency in effect, diligent efforts are underway to prevent the spread of the disease. For the moment, the main initiative is the importation of 400,000 doses of bivalent autovaccine from the Virbac laboratory. Roa Ortiz explained that this vaccine was a meantime measure while others are under study. Concretely, one vaccine that includes the strains isolated from the outbreaks detected in the country, provided by the Vecol laboratory.
Roa explained that "the important aspect is to reduce the impact. Act quickly is the essential message," he said.
The ICA also stated that, for the moment, there is no notification. "Scientific publications or reports from other official veterinary services that indicate that other species are affected."
Streptococcus agalactiae ST7 is particularly concerning among its variant bacteria as it represents one of the predominant fish mortality rates.
The ST7 has various particular pathological manifestations. Among those are pericarditis, epicarditis, myocarditis, endocarditis, meningitis, and septicemia. In simpler terms, one can observe erratic swimming, disorientation, lethargy, and bent bodies due to scoliosis as manifestations of ST7 infection. In addition, ocular lesions of different types are also related to the disease.
Transmission can occur directly or indirectly. On the one hand, direct infection occurs through contact between an infected fish and a healthy one. On the other hand, indirect infection occurs when the bacterium is in water with low oxygen and high ammonia concentration.