Gregarines
Caused by protozoan Nematopsis sp. Gregarines infection block intestine regular function reducing growth rate in pond cultured P. vannamei. These parasites have a commensal relationship with shrimp once colonize gut. It is present in all type of soils at different salinity ranges.
Symptoms
- Feed consumption reduction.
- Poor growth rate.
- Yellow discoloration on the mid g.i. tract.
Mode of Transmission
In most of the shrimp ponds there are different types of polychaetes including Polydora which has been attributed Gregarine infection once shrimp use it as regular diet. These worms also transmit the disease through feces contaminating the soil. Gregarines attach to intestine wall reproducing in colonies once life cycle in complete. There are different criteria believing that direct disease transmition between shrimp to shrimp does not occur.
Diagnosis
During Nematopsis sp. infection microscopic or basic view observations can be made in order to stop infection. Once colonized, hundreds of gregarines are found in the mid-section of the intestine; usually no feed residue is found in the gut after gregarine blocking passage. Gregarine count on individual shrimp is a practical method to estimate level of infection and accurate medication treatments.
Control
Removal of infections agents (Polydora) from pond sediments between growing cycles is recommended. Once gregarine presence is determined there are 2 actions to consider: Wash the pond bottom and treat it with different rates of use of calcium hydroxide and use commercial medication in pelleted feed at rates per kg of feed depending on infection parameters. Gregarine infection can be prevented using growth promoter agent Biolactor® at rates of 2.0 Kg per ton of shrimp feed every 15 days of the month. It contains different natural agents which removes worm adherence to the intestine wall during early gregarine stages. Biolactor® contains Julianiaceae extract, natural herb that removes toxins from g.i. tract including pathogenic bacteria and parasites. Is a natural tool to help shrimp and other species to promote health and reduce medication treatments. A regular rate of use is between 1.0 to 2.0 Kg per ton of feed during a complete cycle.
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