Cyromazine

Cyromazine is a triazine insect growth regulator used as an insecticide and an acaricide. It is a cyclopropyl derivative of melamine. Cyromazine works by affecting the nervous system of the immature larval stages of certain insects.

References:
[1]. Levot GW, et al. Survival advantage of cyromazine-resistant sheep blowfly larvae on dicyclanil- and cyromazine-treated Merinos. Aust Vet J. 2014 Nov;92(11):421-6. [2]. Levot GW, et al. Survival advantage of cyromazine-resistant sheep blowfly larvae on dicyclanil- and cyromazine-treated Merinos. Aust Vet J. 2014 Nov;92(11):421-6.

Cyromazine resistance in a field strain of house flies, Musca domestica L.: Resistance risk assessment and bio-chemical mechanism.[Pubmed:27728890]

Chemosphere. 2017 Jan;167:308-313.

Developing resistance management strategies for eco-friendly insecticides is essential for the management of insect pests without harming the environment. Cyromazine is a biorational insecticide with very low mammalian toxicity. Resistance to Cyromazine has recently been reported in house flies from Punjab, Pakistan. In order to propose a resistance management strategy for Cyromazine, experiments were planned to study risk for resistance development, possibility of cross-resistance and bio-chemical mechanisms. A field strain of house flies with 8.78 fold resistance ratio (RR) to Cyromazine was re-selected under laboratory conditions. After seven rounds of selection (G1-G7), the RR values rapidly increased from 8.8 to 211 fold. However, these values declined to 81fold when the Cyromazine selected (CYR-SEL) strain was reared without selection pressure, suggesting an unstable nature of resistance. The CYR-SEL strain showed lack of cross-resistance to pyriproxyfen, diflubenzuron, and methoxyfenozide. Synergism bioassays using enzyme inhibitors: piperonyl butoxide (PBO) and S,S,S-tributylphosphorotrithioate (DEF), and metabolic enzyme analyses revealed increased activity of carboxylesterase (CarE) and mixed-function oxidase (MFO) in the CYR-SEL strain compared to the laboratory susceptible (Lab-susceptible) strain, suggesting the metabolic resistance mechanism responsible for Cyromazine resistance in the CYR-SEL strain. In conclusion, risk of rapid development of Cyromazine resistance under consistent selection pressure discourages the sole reliance on Cyromazine for controlling house flies in the field. The unstable nature of Cyromazine resistance provides window for restoring Cyromazine susceptibility by uplifting selection pressure in the field. Moreover, lack of cross-resistance between Cyromazine and pyriproxyfen, diflubenzuron, or methoxyfenozide in the CYR-SEL strain suggest that Cyromazine could be rotated with these insecticides whenever resistance crisis occur in the field.

Lethal Effects of the Insect Growth Regulator Cyromazine Against Three Species of Filth Flies, Musca domestica, Stomoxys calcitrans, and Fannia canicularis (Diptera: Muscidae) in Cattle, Swine, and Chicken Manure.[Pubmed:28122880]

J Econ Entomol. 2017 Apr 1;110(2):776-782.

The presence of various species of filth flies is a widespread problem where livestock, including poultry, are maintained and where manure accumulates. The house fly, Musca domestica L.; the stable fly, Stomoxys calcitrans (L.); and the little house fly, Fannia canicularis (L.) (each Diptera: Muscidae), the target pests in our study, can mechanically spread diseases, and S. calcitrans can bite cattle, causing losses in meat and milk production. Chemical control is widely used to suppress filth flies, but resistance to conventional insecticides has become problematic. Hence, an alternative approach, insect growth regulators (IGRs), has been adopted by many livestock producers. We assessed the ability of the IGR Cyromazine in granular and granular-based aqueous formulations to suppress the three muscid species from developing in poultry, cattle, and swine manure collected from commercial livestock production facilities. Each of the two formulations provided either strong or complete control of the pests for the 4-wk duration of the study, excluding the granular formulation that provides control of only F. canicularis developing in poultry manure for 2 wk. The two Cyromazine-based IGR formulations appear to be effective tools that, if rotated appropriately with other insecticides, can be incorporated into integrated pest management strategies for filth fly suppression.

Attapulgite Nanoparticles-Modified Monolithic Column for Hydrophilic In-Tube Solid-Phase Microextraction of Cyromazine and Melamine.[Pubmed:26743944]

Anal Chem. 2016 Feb 2;88(3):1535-41.

In current study, a novel monolithic capillary column with embedded attapulgite nanoparticles has been developed and exploited as a stationary phase in hydrophilic in-tube solid phase microextraction (SPME) of Cyromazine and melamine. The fibrillar attapulgite nanoparticles were embedded in the poly(1-vinyl-3-(butyl-4-sulfonate) imidazolium-co-acrylamide-co-N,N'-methylenebis(acrylamide)) (poly(VBSIm-AM-MBA)) monolith via in situ polymerization. The attapulgite/polymerization ratio of the monolith was finely optimized. Primary factors of in-tube SPME including sample solvent, elution solvent, sample loading volume, elution volume, sample loading flow rate, and elution flow rate were thoroughly evaluated. Under optimal conditions, the limits of detection (LODs) were found to be 21.1 and 0.3 ng mL(-1) for Cyromazine and melamine in the milk formula sample, respectively. Also, the recoveries of Cyromazine and melamine spiked in the sample ranged from 94.5% to 109.9% with RSDs less than 7.6%.

Plasma pharmacokinetics and tissue depletion of cyromazine and its metabolite melamine following oral administration in laying chickens.[Pubmed:27900792]

J Vet Pharmacol Ther. 2017 Oct;40(5):459-467.

The study was designed to characterize the plasma pharmacokinetics and tissue depletion profiles (including eggs) of Cyromazine (CYR) in chickens following oral administration alone or in combination with melamine (MEL). In order to assess the pharmacokinetic profile of CYR, chickens were administered 1 or 10 mg/kg (single oral doses), whereas residue studies were conducted in chickens fed CYR alone (5 or 10 mg/kg) or CYR (5 mg/kg) and MEL (5 mg/kg) for a period of 14 days. Estimates for the apparent volume of distribution (1.66 L/kg), clearance (7.17 mL/kg/min), and elimination half-life (2.82 h) were derived by noncompartmental analyses. The highest concentration of CYR occurred in liver but fell below detectable limits within 3 days following drug withdrawal from feed. Combined feeding of MEL with CYR did not significantly alter CYR tissue levels. CYR residues were detected only in egg white and were undetectable at the 2nd day postadministration. No MEL was found in eggs unless it had been added to the feed, and when present, it almost exclusively restricted to the egg white. Based upon the results of this initial study of CYR pharmacokinetics and residue depletion, it appears that use of CYR as a feed additive either alone (5 or 10 mg/kg) or in combination with MEL (both agents at 5 mg/kg) does not produce unsafe residue levels in edible products as long as appropriate withdrawal periods are followed for tissues (3 days) and eggs (2 days). However, our results indicate that adoption of a zero-day withdrawal period should be reconsidered in light of these results.