Ectoparaciticides Flashcards
What is a pesticide/insecticide?
A pesticide or insecticide is a compound which destroys insect parasite, but in veterinary medicine this name is applied also to substances which are active against parasites living on the skin or which spend part of their life in the body, e.g. warble fly larvae (known as ectoparasites).
Describe the 3 groups of ectoparasites
- those, which larvae migrate through the tissues of the host, e.g. horse bots, cattle warbles, sheep nostril fly larvae – control by organophosphates during the migration larval stage by topical or oral dosing.
- those, which burrow into the skin or penetrate deep into the hair follicles, e.g mange mites – treatment by surface applications of topical forms of spray, emulsions etc. or in the form of dips.
- those, which live mainly on the skin surface – lice, poultry mites, fleas, ticks – are all effectively controlled by surface sprays or dips. Ivermectin is active on skin surface when given by SC or by pour-on.
Name the 9 groups of pesticides
- MACROCYCLIC LACTONES
- PHENYLPYRAZOLES
- NEONICOTINOIDS
- ISOXAZOLINES
- ORGANOCHLORINE COMPOUNDS
- ORGANOPHOSPHOROUS COMPOUNDS 7. CARBAMATES
- PYRETHROIDS
- OTHER PESTICIDE COMPOUNDS
Name the active substances of macrocyclic lactones
IVERMECTIN (Ivomec®, Ecomectin®) MOXIDECTIN (Equest®, Advocate®) EPRINOMECTIN SELAMECTIN (Stronghold ®) DORAMECTIN MILBEMYCIN
Use of macrocyclic lactones
They have been introduced for animal use as anthelmintics (1981) and later as pesticides for the treatment and control of a range of external parasites.
Mode of action of macrocyclic lactones
Macrocyclic lactones enhance the release of gamma amino butyric acid (GABA) at presynaptic neurons. GABA acts as an inhibitory neurotransmitter and blocks the post-synaptic stimulation of the adjacent neuron in nematodes or the muscle fiber in arthropods.
By stimulating the release of GABA, lactones cause paralysis of the parasite and eventual death.
What is the active substance of phenylpyrazoles?
Fipronil
Fipronil use
it is applied topically (spot-on), marketed as Frontline®, TopSpot®
it is indicated for the treatment of fleas and ticks in dogs and cats
because of significant deposition in sebum, sebaceous glands and hair follicles, the
substance is continuously secreted out of the hair follicle forming a layer on the stratum corneum
Fipronil mechanism of action
fipronil acts on the central nervous system - in invertebrates it interferes with the passage of chloride ions in GABA regulated chloride channels, thereby disrupting CNS activity
Fipronil contraindications
Do not use on kittens less than 12 weeks of age and on puppies less than 10 weeks old. The manufacturer warns that the product may be harmful to debilitated, aged, pregnant, or nursing animals.
Name the active substance of neonicotinoids
Imidacloprid
Imidacloprid use
imidacloprid is a chloronicotinyl nitroguanidine insecticidal agent synthesized from the nitromethylene class of compounds Use: topical spot-on solution (Advantage®) is indicated for the treatment of adult and larval stage fleas in dogs and cats
Imidacloprid mechanism of action and contraindications
Mode of action: as an insecticide is to act on nicotinic acetylcholine receptors on the postsynaptic membrane causing CNS impairment and death
Contraindication: do not use on debilitated, aged, pregnant, or nursing animals and do not use on kittens or puppies less than 4 months of age
Name the active substances of isoxazolines
FLURALANER (Bravecto®)
AFOXOLANER (Nexgard®)
SAROLANER (Simparica®)
Use and mode of action of fluralaner and afoxolaner
are systemic insecticides and acaricides that are administered orally
Use: for flea and tick treatment in dogs
Mode of action: both, fluralaner and afoxolaner inhibit GABA-gated chloride channels
and L-glutamate-gated chloride channels. Potency of fluralaner is comparable to fipronil.
Describe Sarlolaner
of the same pharmacological properties as fluralaner or afoxolaner
Use: in dogs for the treatment of tick infestations, flea infestations, ear mite infestations, sarcoptic mange infestations and demodicosis
Why are organochlorine compounds not used anymore? Mechanism of action.
They have high lipid solubility and low volatility therefore these are very persistent. This and their ability of accumulation in lipid tissue caused that they are not used more in many countries (DDT is carcinogenic agent).
They act as contact poisons, causing CNS stimulation, which leads to lack of coordination, paralysis and death.
Toxicity of Lindane (organochlorine compund) and the antidote
Symptoms are typical for neurotoxic agents: hyperexcitability, convulsion, paralysis and death. Can be toxic for host as well.
Antidote: Pentobarbitone in subanaesthetic doses, calcium borogluconate i. v.
Toxaphen use and toxicity
Its value is mainly for residual effect. Its advantage is the effectivity against ticks (Ixodes), including those, which are resistant to other pesticides. It is also satisfactory for the control of sheep ked.
Safety: In general, acute toxicity is 4x greater than DDT, but the chronic is less
Name the active substances of organochlorine compounds
Lindane and Toxaphen
What are some common properties of organophosphorus compounds?
low mammalian toxicity, low persistency and stability for short periods
Mechanism of action and toxicity of organophosphorus compounds
They are both contact and stomach poisons. They act by inhibition and neutralizing of acetylcholinesterase and consequently ACH is accumulated in the synapse leading to death.
All organophosphates are toxic to man and animals due to the blockage of acetylcholinesterase activity. This action may be counteracted by atropine and oximes. Could also be toxic for host.
Name the active substances of carbamates
Carbaryl (Sevin), Propoxur
Mechanism of action and use of carbamates
Carbamates have an anticholinesterase activity but they are more reversible as OP, so carbamates have a low mammalian toxicity.
Most of them act as contact poisons with effect at the nerve ganglion. Carbamates are used predominantly for the control of external parasites on both large and small animals. Their activity against Hypoderma bovis is however very often not sufficient.
What is carbaryl used for?
It is active against ticks, lice, fleas and keds. Carbaryl is used as a powder or dip and is incorporated in collars for dogs and cats.
Use of propoxur
against ticks, lice in powder with activity up to 1 week
Use of pyrethroids
Against ticks
Against lice, keds and sheep scab
Against flies
Which pyrethroids are against ticks?
Permethrin, Cypermethrin and Fenvalerate
Name the active substances of other pesticide compounds
Amitraz, Rotenone, Pyrethrins
Use and mechanism of action of Amitraz
It is an amidine derivative.
Use: Primarly, it is It is specifically recommended for the control of ticks, but is also active against cattle and pig and dog mange.
Mechanism of action: the pharmacologic action of amitraz is not well understood. It may have effects on the CNS of susceptible organisms.
What is rotenone?
Rotenone is a product obtained from plant Derris eliptica. It is an effective inseticide, but is not persistent, should be used frequently (7-10 days). It is a stomach and contact poison. Rotenone is very toxic for fish; already 1 ppm kills the fish. Animals except pigs tolerate it well.
Pyrethrins use and mechanism of action
They are extracted from plants, today are used together with other agents which prolog the short lasting effects of pyrethrins (like piperonylbutoxide). Pyrethrins are contact poisons which have a rapid paralytic action, giving knock-down action, from which some insects may recover. They are active against lice and fleas.
