direct route of drug administration. Parenteral methods like manual injection and automatic injectors can be used for small numbers of valuable fish. Drugs are typically injected intramuscularly into the epaxial musculature, intraperitoneally just below the vent, or into the dorso-median sinus of salmonids. Parenteral administration requires anesthetizing the fish first to prevent injury. It is suitable for vaccination or treatment of limited numbers of valuable fish when other administration routes cannot be used.

1. ROUTE OF ADMINISTRATION OF DRUGS
AND
METHOD OF APPLICATION TO FISH:
Mr. Jayanta Subhash Tiple
Assistant Professor (Contractual),
Dept. of Aquatic Animal Health
Management (MFsc),
College of Fishery Science, Udgir - 413517
Dist. Latur (MS), MAFSU, Nagpur.

2.  Fish pharmacology is essential for undertaking treatment of
fishes using any therapeutic chemicals or drugs.
 Before recommending any medicine to treat the fish diseases
the following factors should be consider:
i. water quality,
ii. Pathogens
iii. fish mortality rate
iv. legal issues
v. economics of treatment
 According to WHO in 1966 – “Drugs is any substance or
product which is used or intended to be used to modify or
explore physiological systems or pathological states for the
benefit of the recipient.

3. Points to consider :
• Fish are poikilothermic – systemic drugs are usually metabolized more slowly than
in terrestrial animals.
• Chemical therapeutants used for external treatment may alter dissolved oxygen
availability to the fish
• Many chemical therapeutants are potentially toxic to fish and function within a
narrow therapeutic range.
• Many chemical therapeutants will interfere with biological filters used in recirculated
systems
• Fish should always be starved for 24 hours before treatments are given.
ROUTEOF ADMINISTRATIONOF DRUGS AND METHODOF APPLICATIONTOFISH:

4.  The basic principle of treating aquatic vertebrates are the same as for any other
terrestrial vertebrates. However, the fluid mechanics and variable nature of
aquatic habitat retains few problems and requires special consideration in fish
therapeutics.
 The poikilothermic nature of fishes must also be considered when searching for the
proper drug and its route of administration. Otherwise desirable drugs may render
inactive or unsuitable for use, if these considerations are ignored during therapeutics.
M ethods by which
drugs are given to fish
Enteral Parentral (
injected) Topical

5. How the drugs is givento Fish
ENETRAL
PARENTAL
TOPICAL

6. Enteral
method Water medication
Gavage
1.

7.  Oral administration is a route of administration where drugs are
administered through the mouth. Less wasteful method of
administration than water medication.
 In-feed medication is standard practice for a large number of
diseases but it is actually prophylactic not therapeutic.
 Medicated feed in pellet form either of floating or sinking variety are
thrown upon the surface of the water a process termed broadcasting
feeding. Antibacterial & Anti parasitic drugs used in feed for feed
medication method.
 It is also useless for mature adult anadromous fish such as
salmonids returning to freshwater to breed, as these too do not
feed.
 In other classes of vertebrates there specie differences especially for
proteinaceous drugs such as gonadotropins and gonadotrophin-
releasing hormones, and some vaccines.

8. Dosages are normally expressed in mg/kg b.w/day where kg b.w. means kg of
bodyweight. Feed medication is on the basis of g/tonne of feed, and the required rate will
depend on the fishes’feed intake.
Furthermore to facilitate accurate weighing and to ensure homogeneous mixing it is normal
to use a premix rather than 100% drug.
Given that:
1. The fish to be medicated are feeding at x% of bodyweight per day;
2. The required dose rate is y mg/kg b.w./day;
3. The premix contains z% active ingredient;

9. The ideal way to medicate feed is to add the medicinal
product to the feed mix prior to pelleting.
Surface-coating
pelleted feed
This process is suitable to the medication of small batches of
feed and can be used for drugs which are heat-liable.
It is therefore the normal means of medicating feed on fish
farms.
Spray-medication
of pelleted feed
Sex hormones are important examples of a class of drugs
which are, for practical purposes, insoluble in water and
which are used in very small doses.
Pelleted M edicated
Feed

10. Leaching:
 Leaching of drug into the water occurs with all forms of in-feed
medication but is a particular problem associated with surface-
coated feed.
 Extent of leaching varies according to the water solubility of the
active ingredient and time for which the feed remains in the water
 The smaller the pellets the faster will be the leaching
Micro-encapsulation of drugs:
 A micro-capsule structure that has been well researched so far is a calcium
alginate core and a chitosan-alginate shell into which the drug is mixed.
 Whether a micro-capsule is retained in the stomach or not is largely a
question of its size.
Artemia Enrichment:
 To enrich artemia cysts they are decapsulated and placed in seawater
which has been pre-sterilized by UV light and is well oxygenated.
 Artemia enrichment has the disadvantage of other forms of in-feed
medication that only healthy fishes can be treated, also a costly and
extremely wasteful method.

11.  In water medication
1. By Bath treatment
2. By Immersion or dipping
3. by Flushing
Bybath treatment
ByDipping
Byflushing

12. i. By Immersion or Dipping:
 The preparation of a small volume of medicated water
in a separate container from that holding the fish.
 The fish, usually held in a net, are immersed in it for a
short period of time and then returned to their normal
environment.
 It is also advisable that the water to be medicated
should be taken from the pond or tank containing the
fish so that chemical and temperature stresses are
minimized.
Advantage
 use of certain antibacterial drugs in aquaria where
filters are used to effect bacterial oxidation of
ammonia to nitrites and nitrates
Disadvantage
 fish are exposed to the stresses of chasing, handling
and netting
By Immersion or Dipping

13.  Bathing differs from dipping as the fish are kept in the water
where they live in.
 It also differ from medicating the water in an aquarium in that,
quite apart from differences in scale and the exposure of fish
shouldn’t be more than 60mins. It is done for a limited time
 In bathing the bottom of the net cage is raised, typically to 2
meters, thus limiting the volume of water to be medicated. This
reduces the weight of drug required and hence reduces both the
cost and degree of environmental contamination.
 Tarpaulins are placed around the cage, separating the contained
from the surrounding water and the drug is added, preferably at
several points in the bath to ensure rapid mixing.
Disadvantage
 Bath treatment is wasteful and
environmentally contaminating.
 Additionally, it’s also Labour-intensive.
By Bath Treatment

14.  In this method, fishes are kept in running water or a raceway system, wherein immersion can be
achieved through flushing, which is also popularly known as, a California flush.
 This means shutting off the flow, medicating the water and after an appropriate interval,
restarting the flow and hence removing the medicated water.
 Flushing is more wasteful, and hence more environmentally polluting, than dipping.
 The major drawback of this method is to obtain a homogenous distribution of the
medication in water.
 An adaptation of this procedure is commonly used in hatcheries for the control of fungal
(Saprolegnia) infection.

15.  Hyperosmotic Infiltration (HI) is a development of immersion designed to accelerate the
absorption of macromolecules or even of particles such as antigenic bacteria.
 The procedure as originally devised consists of two separate immersions.
 First immerse the fish is in a pharmacologically inert solution, hypertonic to fish plasma;
10% urea and 5.23%sodium chloride for 3 minutes.
 Remove fish from the tank and immediately immerse the fish in the medicine or vaccine
solution and then followed by the solution to be absorbed.
 Most recently trials have been conducted with a ‘one step’procedure of a single immersion in a
combination of the ‘carrier’and drug solutes.
By Hyperosmotic Infiltration
iv. By Hyperosmatic infiltration

16.  Gavage is a form of oral administration extensively used in experimental work
 It is rarely used in routine fish management as it is labour intensive
and stressful to the fish.
 Few fish such as brood fish or valuable ornamentals have to be dosed orally.
Gavage

17.  Gavage
This is extensively used in
experimental work because the
dose can be known accurately.
It is rarely used in routine fish
management as it is labour
intensive and stressful to the
fish.
It involves the use of a stomach
tube of caliber appropriate to
the individual fish.
Gavage

18. Parenteral
method
Manual
Injection
Automatic
Injectors
Machine
Injections
Implantation
 Most effective and direct route of drug
administration. Suitable for small
number of valuable fishes.
 Mostly used for aquarium fishes.
2.

19. Indication:
Venepuncture and even cardiac puncture are occasionally used for
experimental purpose, but routine injections are avoided as they are labour-intensive
or capital intensive or both and are always stressful to the fish. Indication for
injection:
i. Vaccination.
ii. Treatment of limited number of valuable fish with drugs which
cannot be given by other route of administration.
iii. The ‘Hormone and Heat stress” diagnostic procedure for
salmonid smolt to check for “stress inducible furunculosis”
(SIB).

20. Intramuscular injection
•given into the epaxial
musculature, normally
approximately mid-way
between the the mid-dorsal
line and the lateral line.
•At the former muscle mass is
deep, and the latter the scales
are smaller.
Intraperitoneal injection
• given into the mid
ventral line just below
vent.
• mostly given to carp
during induced breeding.
Injection into the dorso-median
sinus
•recommended for salmonids
dorso-median sinus (DMS).
•point of insertion is in the
mid-dorsal line in the angle at
the caudal margin of the
cranial dorsal fin.
Manual Injection:
A prerequisite for injection is that the fish should be anaesthetized; without this precaution
injury is likely to be caused to the fish and possibly also to the operator. The needle is always
directed forward between the scales;it should never pierce a scale.

21.  Most effective and direct route
of drug administration.
 Suitable for small number of
valuable fishes.
 Mostly used for aquarium
fishes.
Types of Parenteral method:
1. Intramuscular (IM):
 into skeletal muscle
 given into mid dorsal line
and lateral line
Intramuscular

22. 2. Intraperitoneal (I I):
 given into the mid ventral line
just below vent.
 mostly given to carp during
induced breeding.
3. Intradermal (ID):
 given into skin.
4. Subcutaneous (SB):
 into subcutaneous tissue.
5. Intravenous (IV):
 given into veins
6. Intra - arterial (IA):
 given into arteries.
Intraperitoneal
Subcutaneous
Intra - arterial
Intravenous
Intradermal

23. M achine Injection:
Machines aíe available foí the íapid injection of laíge numbeís of fish. In píactice
this means vaccination by the intíapeíitoneal íoute. An example is the Maíivax. ľhis
contains a specially designed automatic injectoí actuted by compíessed aií when a
fish is slid against a sensitive guaíded button. Anesthesia is not needed with the
machine, but even so use of the machine is safeí foí the opeíatoí than manual
píoceduíes than manual píoceduíes with anesthesia.
Implantation:
Implantations may be intramuscular or intraperitoneal.
Prolonged medication with a drug. It is sometimes
formulated as a pellet or capsule for implantation

24.  simplest and most direct method of
treating fishes
 apply the drug directly to the body
surfaces.
 In this method, the individual fish
caught and drugs applied on the
surface of body.
 Usually used for treatment of skin
ulcer on the valuable ornamental
fishes.
 mostly used Skin disinfectants,
antibacterial drugs, protective
sealant.
 Types of Topical method
1. Inhalation
2. Intranasal
3. Intra vaginal
4. Transdermal
 Used for
gaseous
drugs.
 Fastest
method
 Application
of drugs to
the skin
E.g.,
Nitroglycerine
Inhalation
Transdermal

25.  Simplest and most direct method of treating fishes.
 Apply the drug directly to the body surfaces.
 In this method, the individual fish caught and drugs applied on the surface
of body.
 Usually used for treatment of skin ulcer on the valuable ornamental fishes.
 Mostly used skin disinfectants, antibacterial drugs, protective sealant.
Inhalation:
Used for gaseous
drugs. Fastest
method
Intranasal:
usually to produce a
local effect directly
inside the nose.
Transdermal:
Application of drugs
to the skin. E.g.,
Nitroglycerine
Types of Topical method
Intranasal

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