United States Department of Agriculture • Animal and Plant Health Inspection Service • Safeguarding American Agriculture 

Veterinary Services 

Centers for Epidemiology and Animal Health August 2011 

_________________________________________________________________________________________________________________________ 

Losses Caused by Enteric 

Septicemia of Catfish (ESC) 

2002–09 

The USDA’s National Animal Health Monitoring System 

(NAHMS) conducted its third national study of the U.S. 

catfish industry, Catfish 2010. There were 424 

participating producers in Catfish 2010. The study 

focused on four States, which were divided into two 

regions. The East region was defined as Alabama and 

Eastern Mississippi; the West region included Arkansas, 

Louisiana, and western Mississippi. Results from Catfish 

2010 related to losses among catfish production types 

due to enteric septicemia of catfish (ESC) are presented 

here. In addition, Catfish 2010 results are compared with 

results from the NAHMS Catfish 2003 study.

ESC remains an important disease of farm-raised 

catfish. Channel catfish (Ictalurus punctatus) are the 

species most susceptible to ESC infection. In 1999, 

economic losses due to ESC were estimated to be as 

high as $60 million (Klesius and Shoemaker, 1999). ESC 

vaccines have been approved in recent years. 

 Clinical signs in catfish infected with ESC are both 

physical and behavioral, neither of which is specific for 

the disease. Visible physical signs include small circular 

red spots on the entire body, bloody areas on base of 

fins, a raised reddish area or ulcerated areas on top of 

the head, bulging eyes, and a bloated abdomen. 

Behavioral signs are a reduction of feeding, erratic 

movement while swimming, and “standing” (floating with 

head up and tail down). Not all fish in the same pond will 

always have the same set of signs, and acute cases 

may have no signs. 

 A gram-negative bacterium, Edwardsiella ictaluri, is 

the cause of ESC. Infection usually occurs in the spring 

and fall when water temperatures fall into a range of 22 

to 28°C (72 to 84°F). Mortality due to infection 

decreases greatly outside this temperature range. Stress 

and poor environmental conditions can lead to higher 

losses due to the disease. Some factors that may be 

related to increased losses include improper diet, poor 

water quality, close confinement, handling, low chloride 

levels, and water temperature fluctuations. Fingerlings 

entering their first fall season after winter suffer the most 

losses, while older fish are generally more resistant.

E. ictaluri is readily spread from fish to fish through 

water or by cannibalism of infected fish. The bacteria 

may enter through the gills or nasal passages to reside 

in the brain, resulting in neurologic signs. In addition, E. 

ictaluri is reputed to be transferred from pond to pond via 

nets or other fomites or by mechanical transfer by birds. 

Early intervention with approved antibiotics delivered 

through feed can be helpful in decreasing mortality 

(Tucker and Robinson, 1991). Management techniques 

involving batch production, increased water quality (e.g., 

aeration), vaccination, and decreased stocking density 

should also assist in control of ESC. 

Broodfish operations 

Broodfish are adult catfish intended for use in 

spawning. In 2009, 11.5 percent of breeding operations 

reported losing broodfish to ESC; however, only 

0.9 percent of all broodfish losses were due to ESC. 

Results from Catfish 2003 were similar to those from 

Catfish 2009. In 2002, the percentage of breeding 

operations that reported losing broodfish to ESC was 

higher than the percentage of all broodfish losses due to 

ESC (9.1 and 1.4 percent, respectively). Broodfish 

losses from ESC are relatively low compared with losses 

due to other causes. This difference is likely due to 

broodfish being exposed to ESC at a young age and the 

subsequent lower susceptibility to the disease. Of other 

identified causes of loss in broodfish, fighting was 

reported by the highest percentage of operations 

(26.4 percent during 2002 and 34.6 percent during 

2009). 

Fry/fingerling operations 

 Fry are newly hatched fish less than 1 inch long. For 

this study, fingerlings were considered to be 1 to 8 

inches (2 to 60 lb/1,000 fish). In 2009, the percentage of 

fry/fingerling operations that lost any fingerlings to ESC 

was three times as high in the West region as in the East 

region (table 1). In 2009, 20.2 percent of fry losses were 

attributed to ESC (data not shown). The percentage of 

operations that reported ESC as a cause of fry/fingerling 

loss was also higher in the West region than in the East 

region in 2002. Additionally, the percentage of all 

fry/fingerling operations that reported ESC as a cause of 

fingerling death in 2002 was nearly three times that 
United States Department of Agriculture • Animal and Plant Health Inspection Service • Safeguarding American Agriculture 

reported in 2009 (52.9 and 19.3 percent, respectively) 

[table 1]. The change in ESC-related losses from 2002 to 

2009 could be due to the more intensive production 

practices (feeding, stocking densities) used in 2002, the 

availability of a new antibiotic, or differences in 

environmental conditions such as water temperatures. 

Table 1. Percentage of fry/fingerling operations that 

lost any fingerlings prior to harvest because of ESC, 

by study* and by region 

Percent Operations 

Catfish 2003 Catfish 2010 

East West 

All 

Operations East West 

All 

Operations 

42.1 57.8 52.9 8.7 27.7 19.3 

*In Catfish 2003, producers were asked to report on reasons for fry 

loss for the previous two years while in Catfish 2010 the loss was 

limited to 2009. 

Foodsize-fish operations 

 Fingerlings are grown to foodsize fish in a variety of 

management conditions, but are harvested at a target 

weight of about 1.5 pounds. In Catfish 2010, a higher 

percentage of operations in the East region than in the 

West region lost any foodsize fish to ESC (table 2). 

Unlike loss in fry/fingerlings, in both study years a higher 

percentage of operations in the East region than the 

West region lost foodsize fish to ESC or had outbreaks 

of ESC.

Table 2. Percentage of foodsize-fish operations that 

had ESC outbreaks or lost any foodsize fish to ESC,* 

by study year and by region

Percent Operations 

Catfish 2003 Catfish 2010 

East West 

All 

Operations East West 

All 

Operations 

65.1 54.9 60.6 43.3 25.4 36.6 

*In Catfish 2003, whether an operation had ESC outbreaks was 

assessed while in Catfish 2010 whether an operation had loss from 

ESC was assessed. 

Conclusions 

 ESC remains an important problem for the catfish 

industry, especially in fingerling production. Additionally, 

even though research shows that older fish are less 

likely to be affected by ESC, many operations with 

foodsize fish have experienced losses due to ESC, 

although these losses seem to be decreasing. Another 

encouraging trend is that ESC in fry and fingerlings also 

seems to be decreasing. These stages of catfish are 

reputed to be the most susceptible to ESC. It is difficult 

to determine whether vaccination, management 

changes, or other factors have led to the overall 

decrease in ESC losses. In any case, the catfish industry 

appears to be making gains in controlling ESC. 

References 

Klesius PH, Shoemaker CA. 1999. Development and 

use of modified live Edwardsiella ictalun vaccine against 

enteric septicemia of catfish. In Schultz R (ed.). 

Advances in Veterinary Medicine 41:523–537. 

Tucker CS, Robinson EH. 1951. Channel Catfish 

Farming Handbook, Chapman & Hall, New York, NY. 

_______________________________ 

For more information, contact: 

USDA–APHIS–VS–CEAH 

NRRC Building B, M.S. 2E7 

2150 Centre Avenue 

Fort Collins, CO 80526-8117 

970.494.7000 

Email: NAHMS@aphis.usda.gov 

http://nahms.aphis.usda.gov

#623.0811 

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