Dactylogyrosis (Gill fluke)

 

Definition:

Dactylogyrosis is a parasitic disease caused by species of genus dactylogyrus, affecting the fresh water & marine water fishes characterized by respiratory manifestation.

 

Etiology:

The disease caused by the genus Doctylogyrus. The genus belongs to monogenetic trematodes. There are several recognized species from Dactylogyrus, which they parasitized on freshwater and marine fish. These species are D.vastator, D.extensus, D.anchoratus, D.lamellatus etc.). All Dactylogyridae have seven pairs of marginal hooks and usually one pair of median hooks. They have two to four eyespots located on the anterior of the body. The ovary is round to oval in the shape & the testes are unpaired. All Dactylogyridae are oviparaus with no uterus. They known as gills flukes because of most are located on the gills of their host. A widely distributed species are D.vastator and D.extensus.

 

Susceptible species:

The most species of freshwater & salt-water fishes are susceptible to take the infection with Dactylogyrus sp.

 

Mode of transmission:

Transmission of monogenetic trematodes occurred from fish to other by direct contact or contaminated water.

 

Clinical signs:

1.     Infected fish become restless and collect in large number at water inlet.

2.     The gills are pale, sometimes mosaic-patterned & covered with mucus.

3.     Fish gasp for air & their respiration is impeded.

4.     Young fish suffer from inappetence and emaciated. The head becomes large as compared to the body.

5.     Dark coloration can appear among the diseased fishes.

6.     At the point of attachment of the parasites there is destruction of the epithelium & disruption of tissues.

7.     The edge of the gill has grayish coloration & appears clotted & the opercula appear to be somewhat opened. Hyperplasia and necrosed of the gills may occur.

8.     Sometimes develop a white to gray-white areas of thickening mucous on the skin, especially behind the fins or anterior to dorsal fin.

9.     Secondary infection with bacteria or fungi may also present.

 

Diagnosis:

1.     Case history.

2.     Clinical signs.

3.     Skin scraping or a piece of gills arch mounted with a few drops of water and examined under the microscope.

 

Treatment and control:

1.     The diseased fish is treated with:

a.     Sod. Chloride: 2.5% for 1 hour by bath.

b.     Mebendazole: 1mg/liter for 24 hour by bath method.

c.      Acetic acid: 1 to2ml of glacial acetic acid/1liter for 1-10 minutes by bath method.

d.     Formalin: 250-330mg/1 liter for 1-30 miutes by bath method.

1.     Good management & nutrition help in control of the infection.

2.     Nurseries and rearing ponds must be supplied with water free from parasites.

3.     The introduction of exotic fish must be prevented can be carriers of parasites.

4.     Spawning fish can be freed from parasites by short bath in solution of common salt or formalin.