Brand: PROZAP ® DUST'R ™

Company: CHEM-TECH

FORMULATION: dust for treating animals

ACTIVE INGREDIENT(S): Tetrachlorvinphos: 3% = 30 g/L

CHEMICAL CLASS of the active ingredient(s): Organophosphate


PARASITES CONTROLLED (spectrum of activity)


Beef & Dairy Cattle

  • Against horn flies, face flies & lice:
    • HAND DUSTING: Apply approximately 2 oz (.06 oz. AI) of dust by shaker can, rotary duster or by spoon to the upper portions of the back, neck and poll and to the face as an aid in the control of face flies. Rub in lightly to carry the dust beneath the hair. Repeat as necessary, but not more than once every 7 days.
    • SELF-TREATING DUST BAG: FORCED USE: Put DUST'R in cotton cloth or double burlap bags or use pre-packed weatherproof cattle dust bags and hang in barn door exits or alleyways leading from animal buildings, salt or mineral blocks, or watering holes. Protect cloth or burlap bags from weather.
    • FREE CHOICE USE: Use the same dust bags as above but place in loafing sheds, holding pens, feedlots, near watering holes or other areas where cattle gather. The free choice use aids in the control of lice.


  • Against lice:
    • HAND DUSTING: Apply 3 to 4 ounces of dust by conventional hand or powder duster to each animal with special attention given to the neck and around the ears. Repeat as necessary but not more often than once every 14 days. In severe infestations, both individual animals and bedding may be treated. One pound of 3% dust should be applied per 150 square feet of bedding.


  • Against mites & lice:
    • WIRE CAGES: 1 lb. (.48 oz. AI) per 300 birds; Plunger, rotary type duster or shaker can duster. For individual treatment direct dust to vent and fluff area. Group treatment may be preferred. Dust should reach skin. Do not repeat more often then every 14 days. Wire rungs and corners should also be treated. For Northern Fowl Mites on roosters, thorough individual application of the dust will assure long-lasting control and reduce reinfestation of breeding flocks.

For off-animal uses read the product label.


  • LD50 (acute oral) in rats: for the a.i. 4000-5000 mg/kg
  • LD50 (acute dermal) in rabbits: >2500 mg/kg
  • Estimated hazard class according to the WHO: U, unlikely to present acute hazard

Suspected poisoning? Read the article on coumaphos safety in this site.

Withholding periods (=withdrawal times) in days for meat & milk (country-specific differences may apply: read the product label)

  • Meat:
    • Cattle: USA NIL
    • Swine: USA NIL
    • Poultry: USA NIL
  • Milk for human consumption: USA NIL when used according to label.

WARNING !!!: Never use on humans, dogs or cats.

Tetrachlorvinphos and all organophosphates (e.g. coumaphos, diazinon, dichlorvos, phosmet, etc.) etc. are highly toxic to birds, fish and aquatic invertebrates. Do not apply directly to water, or to areas where surface water is present, or to intertidal areas below the mean high water mark. Do not contaminate water when cleaning equipment or disposing of equipment washwaters.

You may be interested in the following articles in this site dealing with the general safety of veterinary products:


Risk of resistance? YES; cases of resistance of horn flies to organophosphates have been reported in the USA and elsewhere, but resistance to organophosphates is usually weaker and less widespread than to synthetic pyrethroids (e.g. permethrin). There are also reports on resistance of poultry mites to organophosphates. Resistance to organophosphates of lice and mites of cattle & swine is usually not a problem in most of the USA.

This means that if this product does not achieve the expected efficacy against cattle horn flies or against poultry mites it may be due to resistance. However incorrect use is usually the most frequent cause of product failure.

Alternative chemical classes/active ingredients to prevent resistance of external parasites through product rotation:

These alternative products may not be available in all countries, or may not be available for dusting, or may not be effective against all the concerned parasites.

Learn more about resistance and how it develops.


Are the active ingredients of this product ORIGINAL* or GENERICS**?


*Meaning that they are still patent protected and generics are not yet available
**Meaning that they have lost patent protection and may be acquired from manufacturers of generic active ingredients other than the holder of the original patent.

COUNTRIES where this brand/product is marketed: USA
GENERIC BRANDS available? Rather few, if at all. PROZAP DUST'R is a product containig generic tetrachlorvinphos.

Click here to learn more about GENERIC vs. ORIGINAL drugs.

For an overview on the most used antiparasitic spray, dip & dust BRANDS click here.


Tetrachlorvinphos is an organophosphate discovered and developed by SHELL in the 1960s under the trade name RABON.

PROZAP DUST'R is one of the few products containing organophosphates left for treating animals against external parasites (flies, lice, etc.).

Insecticide dusts such as this product are often one of the cheapest options for insect control on animals. However the active ingredients used in such products are mostly rather old (introduced in the 1950s to 1970s) and many pests have developed resistance to them. For cattle, more modern and more effective active ingredients for the control of external parasites are often not available as concentrates but only as ready-to-use pour-ons, injectables, or in the form of insecticide-impregnated ear-tags. They are usually more effective, more convenient and with a longer protection period than dusts and concentrates, but are also more expensive.

All organophosphates are veteran pesticides developed in the 1950s-1960s and are basically contact insecticides. This means that when the parasite comes in contact with it (e.g. during the blood meal, after landing on a treated host, etc), the active ingredient that impregnates the host's hair coat penetrates through the cuticle (i.e. the "skin" of insects and other arthropods) into its organism and disturbs essential biological processes in the parasite's body, in this case its nervous system.

After administration to livestock or other animals, organophosphates do not have a systemic mode of action, i.e. they are not transmitted to the parasite through the blood or the host. Topically administered organophosphates are very poorly absorbed through the skin of the hosts, and what is absorbed is quickly broken down and/or excreted. Consequently the concentration reached in the blood is too low to kill blood-sucking parasites.

Dusting is a delivery form of insecticides that is still often used on poultry wordlwide, due to the fact that tat many bird species have the natural behavior of dusting themselves. Although still popular in the USA, use of dusts in cattle and swine is rather unusual in many other countries (Europe, Latin America, Australia, etc). Dusting for self-treatment of livestock (e.g. using dust bags) has an inherent weakness: Dosing depends on the behavior of the animals. It is unavoidable that some animals get too much product, and other animals not enough. Besides insufficient protection of some animals, this may cause excessive residues in other animals. And it is generally accepted that underdosing of animals favors resistance development. For these reasons parasiticides for dusting are no more allowed in many countries (e.g. the EU). To learn more about dusting animals click here.

Control of susceptible (i.e. non-resistant) horn flies is usually good, because they spend a lot of time on cattle and thus are exposed to the insecticide for a long period of time. Lice are also exposed to insecticides for a long period of time because they never leave the host. Control of face flies is often not as good, due to their different behavior: they do not spend a lot of time on the animals and visit mainly body parts in the face that are humid with body fluids (eyes, nostrils, around the mouth), where the insecticide concentration is diluted by these body fluids. Control of other flies (stable flies, horse fliesblack flies) is insufficient because they may bite the treated animal anywhere in its body and remain attached and thus exposed to the insecticide only during their blood meals that last a few seconds or minutes, which is too short to kill them.


This article IS NOT A PRODUCT LABEL. It offers complementary information that may be useful to veterinary professionals and users that are not familiar with veterinary antiparasitics. 

Information offered in this article has been extracted from publications issued by manufacturers, government agencies (e.g. EMEA, FDA, USDA, etc.) or in the scientific literature. No guarantee is given on its accuracy, integrity, sufficiency, actuality and opportunity, and any liability is denied. Read the site's DISCLAIMER.

In case of doubt contact the manufacturer or a veterinary professional.