Dichlorvos (=DDVP) is an antiparasitic active ingredient used in veterinary medicine in dogs and livestock against external parasites (lice, mites, fleas, flies, ticks, etc.). It is also used against agricultural and household pests. It belongs to the chemical class of the organophosphates.
Common name: DICHLORVOS = DDVP
EFFICACY AGAINST PARASITES
Type of action: Broad spectrum contact, non systemic ectoparasiticide: insecticide, acaricide, tickicide, louisicide, larvicide
Main veterinary parasites controlled: flies, lice, fleas, mosquitoes, ticks, mites, etc.
Efficacy against a specific parasite depends on the delivery form and on the dose administered.
Click here for general information on features and characteristics of PARASITICIDES.
Click here to view the article in this site with the most common dosing recommendations for dichlorvos used in domestic animals.
Oral LD50, rat, acute*: 50 mg/kg
Dermal LD50, rat, acute*: 75-90 mg/kg
* These values refer to the active ingredient. Toxicity has to be determined for each formulation as well. Formulations are usually significantly less toxic than the active ingredients.
MRL (maximum residue limit) set for animal tissues (e.g. beef, mutton pork or chicken)*:
- CODEX: No
- EU: No
- USA: Yes
- AUS: Yes
* This information is an indicator of the acceptance of an active ingredient by the most influential regulatory bodies for use on livestock. MRL's for animal tissues may be set also for agricultural pesticides that are not approved for use on animals but are used on commodities fed to animals. A MRL may be also set in the form of an IMPORT TOLERANCE for active ingredients not approved in a particular country but approved for imported animal commodities.
Withholding periods for meat, milk, eggs, etc. depend on delivery form, dose and national regulations. Check the product label in your country.
Learn more about dichlorvos = DDVP safety (poisoning, intoxication, overdose, antidote, symptoms, etc.).
General safety information for antiparasitics is available in specific articles in this site (click to visit):
- General safety of antiparasitics for domestic animals
- General safety of antiparasitics for humans
- General safety of antiparasitics for the environment
Never use agricultural or hygiene products with this or any other active ingredient on livestock or pets, even if there are veterinary products with this same active ingredient approved for use on animals. The formulations for agricultural or hygiene use are different and may be toxic for livestock or pets.
It is obvious that veterinary products are not intended for and should never be used on humans!!!
MARKETING & USAGE
Decade of introduction: 1950
Introduced by: CIBA-GEIGY, BAYER, SHELL
Some original brands: NUVAN, VAPONA, BERNILENE
Patent: Expired (particular formulations may be still patent-protected)
Use in LIVESTOCK: Yes, moderate, declining, as most organophosphates
Use in HORSES: Yes, scarce and declining, as most organophosphates
Use in DOGS and CATS: Yes, moderate, declining, as most organophosphates
Main delivery forms:
Use in human medicine: No
Use in public/domestic hygiene: Yes
Use in agriculture: Yes
Generics available: Yes, a lot
In livestock & horses: Yes, as for all organophosphates: very frequent worldwide in such species as cattle ticks (Boophilus spp), horn flies (Haematobia irritans), sheep lice (Damalinia ovis), poultry mites (Dermanyssus gallinae), houseflies (Musca domestica), mosquitoes
In pets: Yes, quite frequent worldwide in dog and cat fleas (Ctenocephalides spp)
Dichlorvos is a classical, veteran parasiticide belonging to the organophosphates. Dichlorvos is also known as DDVP. A particular feature of dichlorvos is that it is very volatile.
Dichlorvos has been used a lot in the 1960's to 1990s, both in livestock and pets, as well as in agriculture, public and domestic hygiene.
In dogs and cats it is still used in numerous shampoos, soaps, baths, sprays, powders and the like, but its use has strongly declined after the introduction of more modern and safer flea and tick control spot-ons (= pipettes) and tablets.
In the 1970's dichlorvos was also used in drenches for ruminants against gastrointestinal roundworms. This usage was abandoned after the introduction of safer and more efficient endoparasiticides in the 1980's (e.g. benzimidazoles, macrocyclic lactones, etc.)
However, there is a clear trend to replace all organophosphates with less toxic compounds, and dichlorvos products have been withdrawn or strongly restricted in several countries in the last years (e.g. the EU banned all dichlorvos products for livestock and agriculture in 2006).
Due to its volatility and its high dermal toxicity dichlorvos is especially dangerous for operators because it can be easily inhaled or absorbed through the skin. Several studies have shown that dichlorvos is mutagenic for microorganisms, but there is no coclussive evidence for carcenogenicity in mammals.
In several countries there are commercial veterinary products that contain 100% dichlorvos! They are probably the most toxic veterinary products available worldwide. Needless to say that they must be handled with utmost precaution.
Efficacy of dichlorvos
As most organophosphates dichlorvos is a broad-spectrum insecticide, acaricide and larvicide. Dichlorvos has the particular feature of being very volatile. This makes it especially suited for fumigation against flying insects (e.g. mosquitoes, wasps, etc.) and crawling insects (e.g. cockroaches, ants, etc.). Topically administered it is also especially effective against various cutaneous myiasis, e.g. screwworms, human bot flies (Dermatobia hominis). Due to its volatility it has almost no residual effect against ticks and flies, and this is why it is often used in mixtures with synthetic pyrethroids.
However, resistance of important veterinary parasites to all organophosphates, including dichlorvos, is widespread, especially in in cattle ticks (Boophilus spp), horn flies (Haematobia irritans), sheep lice (Damalinia ovis), poultry mites (Dermanyssus gallinae), mosquitoes, dog and cat fleas (Ctenocephalides spp) and houseflies (Musca domestica). As a consequence, products with this active ingredient may not achieve the expected efficacy in many places. The same applies to all other organophosphates. This is also a reason for their progressive replacement with newer active active ingredients with a different mode of action.
Pharmacokinetics of dichlorvos
Percutaneous absorption (i.e. through the skin) of topically administered dichlorvos depends on the animal species, the administered dose, and the extension of the treated body surface. Due to its volatility dichlorvos is easier absorbed through the skin or after inhalation than most other organophosphates. However, once absorbed into blood it is very quickly metabolized in the liver to less toxic compounds and very rapidly excreted through urine. Maximum plasma concentrations are detected about 2 hours after administration. Half-life in blood is shorter than 15 minutes.
Mechanism of action of dichlorvos
As all organophosphates insecticides dichlorvos acts on the nervous system of the parasites (but also of mammals, birds, fish and many organisms!) as inhibitor of acetylcholinesterase (also known as AchE), an enzyme that hydrolyzes acetylcholine (Ach). Ach is a molecule involved in the transmission of nervous signals from nerves to muscles (so-called neuromuscular junctions) and between neurons in the brain (so-called cholinergic brain synapses).
AchE's role is to terminate the transmission of nervous signals where Ach is the neurotransmitter (there are several other neurotrasmitters). By inhibiting the activity of AchE, carbamates prevent the termination of those nervous signals, i.e. the neurons remain in constant activity and excitation, massively disturbing the normal movements of the parasites. The bottom line for the parasites is that they are paralyzed and die more or less quickly. Organophosphates bind irreversibly to AchE, in contrast with carbamates, another chemical class of parasiticides, which bind reversibly to AchE.
Click here to view the list of all technical summaries of antiparasitic active ingredients in this site.