Aquatic Animal Disease Report

1. White Spot Disease (WSD)

Pathogen: White spot syndrome virus (WSSV)

Species affected: Penaeus monodon and Litopenaeus vannamei (10-85 DOC)

Name of affected area: reported in 18 provinces (total area 7,279 ha) including Hai Phong, Quang Ninh, Nghe An, Ha Tinh, Quang Tri, Quang Binh, Quang Ngai, Thua Tien Hue, Phu Yen, Binh Dinh, Ho Chi Minh, Long An, Tien Gang, Ben Tre, Tra Vinh, Soc Trang, Bac Lieu and Ca Mau.

Mortality rate: average to high, 100% in some cases within 10 d.

Clinical signs: lethargic or moribund shrimps aggregated at pond surface and edges, slow to erratic swimming behavior, overall body color often reddish, minute to large (0.5-2.0 mm diameter) white inclusions embedded in the cuticle;

Control measures: early harvest, strict isolation of infected ponds from movement, strengthened control of transportation, disinfection of infected ponds using Calcium hypochlorite (chlorine).

2. Yellowhead Disease (YHD)

Pathogen: Yellowhead virus (YHV)

Species affected: Litopenaeus vannamei

Name of affected area: reported in Quang Tri, Thua Thien Hue and Bac Lieu provinces with 35.67 ha affected.

Mortality rate: could reach 100% in 2-5 days after infection.

Clinical signs: Affected shrimps showed sudden increase in feeding activity and abnormal growth, then loss of appetite; aggregated near the pond surface or at the edge of the ponds followed by mortalities. Body is discolored, cephalothorax/hepatopancreas swollen and turned to color yellow or brown. Tissues of most organs (gills, hepatopancreas, gut epidermis) were necrotic with degenerated cell nuclei. Shrimps were most sucsceptible at the age of 20-70 DOC (no infection in shrimps under 15 DOC). Fastest transmission of the disease was observed in shrimps at 20-30 DOC when mortality could reach 100% over 2-5 days of infection.

Control measures: Disinfection and discharge of contaminated water; movement and transportation control.

3. Acute Hepatopancreatic Necrosis Diseae (AHPND)

Pathogen: Vibrio parahaemolyticus with Phage A3

Species affected: Penaeus monodon and Litopenaeus vannamei (10-45 DOC)

Name of affected area: reported in 18 provinces and caused losses in total shrimp culture area of 2,125 ha.

Affected provinces include Nam Dinh, Hai Phong, Quang Ninh, Nghe An, Ha Tinh, Quang Tri, Quang Binh, Phu Yen, Khanh Hoa, Ho Chi Minh, Dong Nai, Long An, Tien Giang, Ben Tre, Tra Vinh, Soc Trang, Bac Lieu and Ca Mau.

Mortality rate: could reach 95% in intensive and semi-intensive farms;

Clinical signs: shrimps become lethargic with soft, darkened shells, mottling of the carapace. Pathology appears to be limited to hepatopancreas.

Control measures: strict isolation of infected ponds from movement and transport controls, disinfection of infected ponds using Calcium hypochlorite (chlorine).

Source: http://www.enaca.org/modules/library/publication.php?publication_id=1143&title=quarterly-aquatic-animal-disease-report-q2-2014