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Quick, hydrated limes impractical for controlling vibriosis in shrimp ponds

Ing. Juan Portal Dr. Carlos A. Ching

Use can be harmful to workers and cause stress to shrimp during an outbreak

vibriosis
Shrimp farmers in Latin America commonly use hydrated lime at rates of 75-100 kg/ha to manage outbreaks of pathogenic Vibrio species with uncertain results. Eventually, many have to use probiotics or antibiotics to control the vibriosis.

Although the application of lime has proven to be beneficial in controlling shrimp diseases like Taura syndrome and white spot syndrome by keeping optimum alkalinity levels, trials conducted at the Fisheries Engineering Faculty of Tumbes University in Peru showed that using lime for controlling vibriosis can be im-practical.

This is based on the minimum inhibitory concentrations (MICs) found for hydrated and quick lime against pathogenic strains of Vibrio parahaemolyticus and V. alginolyticus. For instance, it would require applications of 4,000 kg/ha hydrated lime to control V. alginolyticus and 9,000 kg/ha for V. parahaemolyticus. If applied at such high concentrations, the lime would cause drastic pH changes in pond water and stress the affected shrimp.

Inhibitory concentrations

Research was done to determine the minimum inhibitory concentrations of calcium oxide quick lime and calcium hydroxide hydrated lime against pathogenic strains of Vibrio parahaemolyticus and V. alginolyticus identified in a shrimp farm next to the Tumbes University campus and isolated in agar.

Both types of lime were tested at a pure bacterial concentration of 5 x 103 colony-forming units (CFUs) per mL for an incubation period of 24 hours at 28 degrees-C. Using an adaptation of the standard methods described by the U.S. National Committee for Clinical Laboratory Standards, researchers found MIC values of 30 ppm for calcium oxide use against both V. parahaemolyticus and V. alginolyticus, 900 ppm for calcium hydroxide treatment of V. parahaemolyticus and 400 ppm for control of V. alginolyticus with calcium hydroxide.

Trials were conducted in two phases: an exploratory phase using a wide range of concentrations for both types of lime and a final phase in which more accurate values were obtained (Tables 1-4).

Portal, Inhibitory effects of calcium oxide, Table 1

Calcium Oxide ConcentrationReplicate 1Replicate 2Replicate 3Replicate 4Replicate 5Rate of Effectiveness
100 ppm+++++100%
90 ppm+++++100%
80 ppm+++++100%
70 ppm+++++100%
60 ppm+++++100%
50 ppm+++++100%
40 ppm+++++100%
30 ppm+++++100%
20 ppm++40%
10 ppm0%
0 ppm0%
+ = positive inhibitory effect, – = negative inhibitory effect


Table 1. Inhibitory effects of calcium oxide against a pathogenic strain of Vibrio parahaemolyticus.

Portal, Inhibitory effects of calcium oxide, Table 2

Calcium Oxide ConcentrationReplicate 1Replicate 2Replicate 3Replicate 4Replicate 5Rate of Effectiveness
100 ppm+++++100%
90 ppm+++++100%
80 ppm+++++100%
70 ppm+++++100%
60 ppm+++++100%
50 ppm+++++100%
40 ppm+++++100%
30 ppm+++++100%
20 ppm+20%
10 ppm0%
0 ppm0%
+ = positive inhibitory effect, – = negative inhibitory effect


Table 2. Inhibitory effects of calcium oxide against a pathogenic strain of Vibrio alginolyticus.

Portal, Inhibitory effects of calcium hydroxide, Table 3

Calcium Hydroxide
Concentration
Replicate 1Replicate 2Replicate 3Replicate 4Replicate 5Rate of Effectiveness
1 ppt+++++100%
900 ppm+++++100%
800 ppm++40%
700 ppm0%
600 ppm0%
500 ppm0%
400 ppm0%
300 ppm0%
200 ppm0%
100 ppm0%
0 ppm0%
+ = positive inhibitory effect, – = negative inhibitory effect


Table 3. Inhibitory effects of calcium hydroxide against a pathogenic strain of Vibrio parahaemolyticus.

Portal, Inhibitory effects of calcium hydroxide, Table 4

Calcium Hydroxide
Concentration
Replicate 1Replicate 2Replicate 3Replicate 4Replicate 5Rate of Effectiveness
1 ppt+++++100%
900 ppm+++++100%
800 ppm+++++100%
700 ppm+++++100%
600 ppm+++++100%
500 ppm+++++100%
400 ppm+++++100%
300 ppm0%
200 ppm0%
100 ppm0%
0 ppm0%
+ = positive inhibitory effect, – = negative inhibitory effect


Table 4. Inhibitory effects of calcium hydroxide against a pathogenic strain of Vibrio alginolyticus.

Both quick and hydrated limes used at their MICs showed inhibitory effects that worked through a sudden pH increase of the medium. The inhibitory effects occurred at pH levels above 9.5 for quick lime and over 9.0 for hydrated lime. When these MIC values for both types of lime were applied in pond water, it was found that the action of quick lime lasted for 10 minutes, and the action of hydrated lime lasted for 15 minutes.

Vibriosis management?

Some Latin-American shrimp farmers have reported beneficial results in the use of hydrated lime against pathogenic Vibrio attacks at concentrations of 75-100 kg/ha based on the “disinfectant power” of such concentrations. However, the authors have visited many shrimp farms in Latin America that have had uncertain results with the application of these liming rates. Farmers who limed at 75-100 kg/ha eventually had to use other methods, such as the application of probiotics or antibiotics in feed, to overcome Vibrio outbreaks.

Also in this study, quick and hydrated limes were applied at 75 kg/ha to tanks containing pond water with the pathogenic Vibrio strains tested for MICs. Results showed the applications were not successful in controlling the bacterial populations, even under optimal water parameters (Table 5).

Portal, Pond water parameters, Table 5

Pond Water ParameterBefore Lime ApplicationOne Hour After Application
Control
One Hour After Application
Calcium Oxide
One Hour After Application
Calcium Hydroxide
pH8.58.69.89.5
Temperature (° C)3030.530.630.5
Dissolved oxygen (mg/L)5.55.45.45.6
Total alkalinity (ppm)158153159162
Total hardness (ppm)3,5603,5503,5403,550
Table 5. Pond water parameters taken before and one hour after the application of quick and hydrated limes.

Perspectives

Although this study found that a smaller amount (300 kg/ha) of quick lime was required for inhibiting Vibrio species than the 4,000 and 9,000 kg/ha of hydrated lime needed, the use of quick lime is not recommended because it can be harmful to workers who apply it. The sudden rise in water pH quick lime generates can also cause stress to shrimp during a Vibrio outbreak.

(Editor’s Note: This article was originally published in the July/August 2013 print edition of the Global Aquaculture Advocate.)