White spot disease in fish

ich disease in fresh water fishes

1. White spot disease in fish PRESENTED BY: HARAPRIYA DEPARTMENT OF AQUATIC ANIMAL HEALTH MANAGEMENT Dt- 01-11-2017

2. Name and description of diseaese It is one of the most prevalent disease affecting mostly cultured and aquarium fishes. Disease caused by Ichthyophthirius multifiliis , characterized by presence of white spots all over the external body surface (skin ,fins, gills). Ichthyophthiriasis comes in front of all parasitic diseases, as it is widespread in all types of intensive culture. Also, outbreaks of this disease lead to mass mortality and reduce the growth rate of fish.

3. Outbreak of disease Stress factor includes: 1 . Overcrowding of fish. 2 . Low dissolved oxygen 3. Chemical pollutants in the water. 4 . High temperature, and spawning activities( 15-25˚c outbreak occur).

4. Mode of transmission: 1 . The disease is transmitted through direct and indirect contact with infected fish. 2 . Water act as vehicle for spreading the infection. 3 . The disease is easily introduced to fish culture by adding new infected fish or contaminated aquatic plants.

5. External pathology: The disease is characterized by appearance of white spots on the skin, gills, fins and cornea of the eye. H owever I. multifiliis only infects the gills, with no obvious gross lesions on the body surface. Ulcers develop in the skin of heavily infected fishes and are often give rise to the sites of secondary bacterial or fungal infections. I nfected fishes swim more rapidly and rub themselves against objects. They become lethargic and eventually cease feeding. In more severe cases the skin may be covered with slimy grey patches and also skin detachments occur. When the gills become infected, they appeared pale in color and swollen, respiration become difficult and the fish aggregate at the water inlet and die.

6. Infected P. sutchi Infected B. splendensis Infected aquarium fish Infected aquarium fish

7. Internal pathology: Skin penetration by theronts in the epidermis causes ulcers. These multiply not only in areas around the parasite, but throughout the epidermis. there is erosion of the epithelia, leading to ulcer formation and exposure of the deeper tissues to bacterial and fungal invasion. The epithelial erosion and ulceration that result from the parasite ’s entrance into and exit from the host. Sometimes when trophonts and mature it break the epithelium and comes out to the water. Fish may die due severe epithelial destruction hence osmoregulatory failure.

8. Ulceration caused by I multifilis on gold fish Deep ulcers on farmed fish

9. Histopathology: host and parasite interaction After infection by throphont approximately 40 h, most trophonts are located next to the basement membrane. The cells between the parasite and the basement membrane become hydrophobic, vacuolated or necrotic, with pyknotic nuclei . Cell damage is observed only in the cellular layers in direct contact with the developing trophont . Host cell debris can be observed in the food vacuoles of the trophont and in the spaces in the epithelial capsule around the parasite. There is evidence of haemorrhage occurring in the skin as a result of parasite invasion. Large, pale-staining, alarm substance cells have been observed in the area of the developing trophont In mild infections only a few leukocytes are seen in the epithelium. Infected fishes develop a lymphocytopenia and neutrophilia.

10. Aetiology: Disease caused by Ichthyophthirius multifilliis . Ich is a holotrichous , histophagous ciliate. It possesses a large, horse shoe shaped macronucleus and at least one small, round micronucleus. It is round to oval in shape. The body surface covered with cilia which is responsible for progressive motility in the water as well as its movement within the epithelium. The full grown parasitic form grows to 0.5 to 1.5 mm , which is quite large for unicellular organisms . During the parasitic the micronucleus, which is responsible for the generative process. Ich is typically a warm water disease and a common temperature for ich outbreaks is 15 – 25 ° C (59– 77 ° F). Parasites complete their life cycle in 3– 6 days at 25 ° C

11. Aetiology: I. multifiliis is placed in Phylum: C iliophora Order : Hymenostomatida Suborder : Ophryoglenina Class : Oligohymenophora Subclass: Hymenostomata Family Ichthyophthiridae Genus: Holotrichia

12. multifilis Horse shoe shaped nucleus microscopic diagram Ich parasite.

13. Life cycle: Direct life cycle of I, multifilis is comprised of : a) infective theront b) obligate fish associated trophont . c) water borne reproductive tomont . A ll the stages of the parasite are ciliate. Free swimming theront penetrate through the mucus and invadens into the surface epithelia of the skin and gill. Upon entering into the host it is transferred into trophont , which feeds and grows within the host body . Trophont actively moves within the epithelium. Parasites exit the fish as the mature tomont , which secrete a protective cyst and divides within it to form 500-1000 daughter cells called tomites . Tomites differentiate into theronts which invades eventually the host or remain in water with some attachment.

14. Life cycle of I. multifilis

15. Geographical distribution: Ich is a cosmopolitan parasite of fishes. There is evidence that it originated in Asia as a parasite of carp. H igher incidence of Ich in salmonid fishes from South African rivers in areas where intensive aquaculture occurred. In Egypt disease was recorded in numerous fish species such as tilapia carp and ornamental gold fish. The parasite has a wide geographical distribution and has been found in European part of Soviet Union, Central Asia, Siberia and USA.

16. Host range: Ich appears to parasitize all freshwater fishes . H igher incidence of Ich in salmonid fishes from South African rivers in areas where intensive aquaculture occurred. The majority of infected fishes were gizzard shad ( Dorosoma cepedianum ) and threadfin shad ( Dorosoma petenense ) However it affects to all the pond cultured as well as the aquarium fishes.

17. Treatment and control: The objective for the treatment of a disease is to break the cycle of infection. In I. multifiliis infection, the most vulnerable stage is the free-swimming theront . The simplest treatment is reduction or removal of theronts . The repeated transfer of fishes to different aquaria is effective. Daily transfer for 5–7 days is usually sufficient to break the cycle of parasite . exposing the water to ultraviolet light can control Ich infections. The recycled water is passed through an ultraviolet light sterilizer and exposed to 91,900 µW/cm before being cycled back into the aquaria containing fish. Theronts are killed at temperatures higher than 30°C.

18. Treatment… .Fishes in aquaria are treated with 25 ppm (1 ml formalin to 10 gallons of water ) of formalin on alternate days until the infection is cleared. Usually the water is changed on days between treatments. Pond fishes are treated with 5 to 8 gallons of formalin/acre foot water. Bath treatments are also used; fishes are treated with 160–250 ppm formalin for 1 h daily until mortality stops. Malachite green has also been used, either alone or in combination with formalin. The zinc-free oxalate salt of malachite green is the only form of the chemical that is effective against Ichthyophthirius . Acriflavin , in a neutral state or Acriflavin hydrochloride is used as a long bath at 10 ppm for 3 to 20 days. Acetic acid, it is used as a bath (1%) solution in five minutes for aquarium fishes.

19. Treatment: Sodium chloride, it has a dual purpose as its use kills the free swimming tomonts and theronts . In addition, it compensates the decrease of serum sodium caused by the epithelial damage and helping the infected fish to maintain the immune defense . Basically, it should be only used in treatment of aquarium fishes by short baths at a level of 1.5 to 2.5% for 10 to 30 minutes/ 7 days . 7. Potassium permanganate, it must be used in freshly prepared solutions. In ponds the does is 2 ppm for scaleless fishes and 2 to 5 ppm for scald ones as continuous treatment. 8. Methylene blue, it is recommended at 23 ppm as a permanent bath in aquaria at a temperature between 21˚c and 26˚c daily.

20. Prophylactic measures: Control of I.multifiliis outbreaks requires good animal husbandry and management in addition to the use of therapeutic agents. Dead fishes should be removed as soon as they are found because trophonts begin to drop off and encyst within hours . Aquaria, ponds and should be drained,and in race ways water should be continuously exchangedand and allowed to dry after an outbreak. Drying kills the parasite. The bottom of a dried pond should be treated with lime. If ponds cannot be drained completely,the residual water should be treated with a disinfectant such as calcium hypochlorite.

21. THANK YOU……