White Feces Disease (WFD)

Name

White feces disease (WFD) or WF.

Clinical signs

The excrement of white feces that float in water or found on feeding trays, shrunk and whitened hepatopancreas (in the part that is normally filled with food), empty digestive tract, as well as low shrimp appetite and growth rate. Infected shrimp will appear darker (especially on the gills) and weak.

Method of diagnosis

Diagnosis can be done by observing initial clinical signs, and further confirmation is done by bringing a sample of the shrimp to the laboratory for testing using PCR method.

Name

Vibrio parahaemolyticus, V. fluvalis, V. alginolyticus, V. mimicus, and parasitic protozoa called gregarines.

Pathogen type

Bacteria and protozoa

Synonyms Vibrio bacteria

Characteristics

The pathogen is a Gram-negative, rod-shaped bacteria classified as fermentative bacteria. The bacteria shows positive results for oxidation and catalase tests (V. fluvalis, V. sealginolyticus, dan V. mimicus). On the other hand, V. parahaemolyticus showed a negative result for catalase test. This bacteria initially interacts with the host (or shrimp) by adhering to host cells, followed by entry to the cells, invasion, and local spread in the shrimp’s body. The bacteria then damages the shrimp’s digestive organ (hepatopancreas).

Toxicity

WFD may occur at around 2 months of cultivation (DoC 50-60), which causes a 20-30% decrease in productivity and a decrease in SR. Mortality rates for this disease can reach 60%.

Predispositional factors

Poorly maintained water quality, such as an overly high salinity, excess feeding, poor feed and fry quality, as well as algal population blooms can trigger this disease occurrence.

Transmission

Bacteria enter shrimp’s digestive tract with food, followed by infection of the hepatopancreas. This disease can also be transmitted to other shrimp through cannibalism. Waste build up at the bottom of the pond further increases the probability of this disease.

Epidemiology

This disease is rampant in Central, East, and West Java along with Bali, Lombok, and Sumbawa. It first entered Indonesia in 2014.

Host or vector

No data.

Infectious dose

Total Vibrio count > 10² CFU/ml can trigger the occurrence of this disease..

Incubation period

No data.

Susceptibility to drugs

No data.

Susceptibility to disinfectants/probiotics

No data.

Physical inactivation

No data.

Early warning

Poor water quality, with a low transparency of under 20 cm, high alkalinity of over 150 ppm, low DO < 3 ppm, high total Vibrio count > 10² CFU/ml, high TOM and TAN, as well as excessive feeding are early warning signs that this disease might occur.

Prevention

Prevention of WFD can be done by reducing stocking density, minimizing organic matter accumulation by changing the water, using chlorine and/or hydrogen peroxide during water preparation, monitoring water quality, using probiotics to control Vibrio bacteria populations, maintaining water color stability and phytoplankton populations by managing the C:N:P ratio, using high-quality fry (SPF or SPR), and controlling feed management.

Treatment

If WFD occurs in the farm, reduce the amount of feed or stop feeding temporarily. Aside from that, improve aeration using paddle wheels, add garlic powder into feed, and use probiotics at a dose 3x higher than usual.

Eradication

To stop WFD after severe infection following total harvest, and to prevent it in the next cultivation cycle, conduct disinfection of farm facilities (tarpaulin/LDPE/HDPE, water tanks) and equipment such as nets, feeding trays, and paddle wheels. Ensure the hygiene of all personnel leaving and entering the farm. Remains of dead shrimp prior to infection should be burnt or buried.

OIE. 2018. Manual of Diagnostic Tests for Aquatic Animals.

Thitamade, S. 2016. Review of current disease threats for cultivated penaeid shrimp in Asia. Aquaculture. 452: 69–87

Thong, P.Y. White Faeces Disease in Shrimp. Shrimp Culture.

UPT DJPB. 2016.