White spot disease, caused by the parasite Ichthyophthirius multifiliis, is one of the most prevalent and destructive diseases affecting both cultured and aquarium fish. The disease is characterized by the appearance of white spots on the skin, gills, and fins. Stress factors such as overcrowding and poor water quality can lead to outbreaks. The parasite has a direct life cycle alternating between an infective theront stage, an obligate fish-associated trophont stage, and a waterborne tomont stage. Treatment involves breaking the life cycle through measures such as frequent water changes and chemical treatments, while control relies on good management practices and disinfection of facilities between outbreaks.

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.
 However 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.
 Infected 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: Ciliophora
Order: Hymenostomatida
Suborder: Ophryoglenina
Class: Oligohymenophora
Subclass: Hymenostomata
Family Ichthyophthiridae
Genus: Holotrichia

12. I. 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.
All 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

16. Geographical distribution:
 Ich is a cosmopolitan parasite of fishes. There is evidence that it originated in Asia
as a parasite of carp. Higher 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.

17. Host range:
 Ich appears to parasitize all freshwater fishes.
 Higher 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.

18. 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.

19. Treatment…
1. .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.
2. 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.
3. 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.
4. Acriflavin, in a neutral state or Acriflavin hydrochloride is used as a long bath at
10 ppm for 3 to 20 days.
5. Acetic acid, it is used as a bath (1%) solution in five minutes for aquarium fishes.

20. Treatment:
6. 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.

21. 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.

22. THANK YOU……