Brand: CYRAZIN ™ Spray-on for Sheep
PARASITES CONTROLLED* (spectrum of activity)
* Country-specific differences may apply: read the product label.
- For the control of blowfly strike on coarse-woolled sheep.
- Length of protection: New Zealand, up to 6 weeks
* Can be slightly different in some countries: read the product label!
Use recommendations in the NZL, based on weight:
|Weight in kg||Total Dose (mL)||Gun setting (mL)||Number of bands|
|For the prevention of all commonly struck areas|
Read the product label for further details on dosing and administration.
- LD50 (acute oral) in rats: 1467 - 4050 mg/kg for the active ingredient. Estimate for the formulation: >5000 mg/kg.
- LD50 (acute dermal) in rats: >3100 mg/kg mg/kg for the active ingredient. Estimate for the formulation: >5000 mg/kg.
- Estimated hazard class according to the WHO classification of pesticides for cyromazine: U, unlikely to present acute hazard
Suspected poisoning? Read the article on cyromazine safety in this site.
Withholding periods (=withdrawal times) for meat, milk & shearing (country-specific differences may apply: read the product label)
- Meat: New Zealand 14 days.
- Milk for human consumption: New Zealand, discard milk for 35 days following treatment.
- Shearing: New Zealand 2 months.
You may be interested in the following articles in this site dealing with the general safety of veterinary products:
- Safety for humans
- Safety for domestic animals
- Safety for the environment
- Hazard classifications of pesticides
Risk of resistance? LOW, mainly in Australia.
- Organochlorines (e.g. DDT, dieldrin): introduced in 1946 in Australia, field resistance detected in 1957. Withdrawn for safety reasons in the 1970s.
- Organophosphates (e.g. diazinon, malathion): introduced in 1957 in Australia, field resistance detected in 1965. Withdrawn for safety reasons in the mid 2000s.
- Benzoylphenyl ureas (e.g. diflubenzuron): introduced in 1993 in Australia, field resistance detected in 2001. Claim for blowfly strike prevention removed in 2008. Since then approved only for lice control.
First cases of blowfly field resistance to the mentioned chemical classes appeared usually about 10 years after product introduction. Other chemical classes such as synthetic pyrethroids (e.g. cypermethrin) and macrocyclic lactones (e.g. ivermectin) have been used only marginally for blowfly strike prevention during these years, i.e. it can be assumed that the selection pressure on blowflies exerted by chemicals of these two classes has been rather low.
It is now about 35 years since the introduction of the first cyromazine product (VETRAZIN Liquid for dipping and jetting) in the late 1970s, and so far only one case of light tolerance in the field (Nimmitabel) has been reported in 2011 for Lucilia cuprina in Australia. However, even in the affected properties the product still accomplished its label claims. Tolerant flies exhibited a Resistance Factor (RF) of about 3, meaning that a three-fold concentration of cyromazine was required to kill the tolerant maggots when compared with the susceptible ones. RFs for organochlorines, organophosphates and/or benzoylphenyl ureas can reach more than 100, which means that more than a hundred-fold concentration of these compounds is required to kill resistant flies when compared with susceptible flies.
The reasons for this unexpected behavior of cyromazine regarding resistance are not completely elucidated. It may be related to the fact that the organochlorines, organophosphates and benzoylphenyl ureas were mostly used twice a year (once against blowfly strike prevention, once against lice), whereas cyromazine is usually used only once a year, which results in a lower selection pressure. It has also been also proposed that the gene mutations that confer resistance to cyromazine are not completely dominant, and that the cyromazine-tolerant flies have little biological advantage over the susceptible ones. These factors together make it difficult for the cyromazine-tolerant flies to multiply and become predominant in the fly population.
To our knowledge no reports on resistance or tolerance of blowflies (Lucilia cuprina, Lucilia sericata) to cyromazine have been reported in New Zealand, UK (and other EU-countries) or South Africa, regions where cyromazine has been also vastly used against blowfly strike for decades.
- Organophosphates (mainly diazinon). High blowfly resistance in Australia already. Withdrawn in Australia.
- Synthetic pyrethroids (e.g. α-cypermethrin). Short protection periods.
- Macrocyclic lactones (mainly ivermectin). Not available in all countries for blowfly strike prevention.
- Spinosad. Short protection periods. Not available in all countries for blowfly strike prevention.
- Benzoylphenyl ureas (mainly diflubenzuron, triflumuron). No more approved for blowfly strike prevention in Australia due to high resistance.
These alternative products may not be available in all countries, or may not be available as spray-ons/pour-ons.
For an overview on the most used antiparasitic pour-on brands click here.
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: New Zealand
GENERIC BRANDS available? YES, a few in Australia and New Zealand. So far none in the UK.
Click here to learn more about GENERIC vs. ORIGINAL drugs.
CYRAZIN Spray-on for Sheep is a local brand of MERIAL, basically a generic version of the original VETRAZIN Spray-on from CIBA-GEIGY (→ NOVARTIS → ELANCO).
Cyromazine is a so-called Insect Growth Regulators (IGR) belonging to the group of the Chitin Synthesis Inhibitors (CSI). It was introduced in the late 1970s (by CIBA-GEIGY → NOVARTIS → ELANCO). It is narrow-spectrum larvicide. It is abundantly used in sheep, moderately in poultry, marginally in horses, but not in other livestock or pets. It is also moderately used in agricultural pesticides.
Chitin is a component of the cuticle of insects, which is an essential part of their outer skeleton. If chitin is not properly produced, fly maggots die when they attempt the next molt. However, cyromazine does not really inhibit chitin synthesis, but interferes with its correct deposition. The consequence is the same: Fly maggots cannot complete molting and die. Other CSIs such as the benzoylphenyl ureas (BPUs, e.g. diflubenzuron, triflumuron) do actually inhibit chitin synthesis. But whereas BPUs exert this effect an almost all insects, cyromazine is quite specific for Dipterans (flies, mosquitoes, etc.) and some beetles. This makes it much less harmful for the environment, but also ineffective against other sheep pests such as lice.
As all IGRs, cyromazine does not immediately kill the fly maggots (larvae), i.e. it has no knockdown effect. Larvae will die at their next attempt to molt to the next developmental stage, which may take 1-4 days to occur, depending on age of the maggots at the time of treatment, humidity, temperature, etc. For this reason, cyromazine and other IGRs are usually not used for curing established strikes, but for preventing their development by killing the very small first-stage larvae that hatch out of the eggs deposited by the adult flies on the wool.
Cyromazine is quite soluble in water, in contrast with many other parasiticides that are rather lipophilic. This means that heavy rains may significantly shorten the length of protection of this and other cyromazine-based products.
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.