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In view of the prevailing insecticide resistance and increasing safety and health concerns, there is an urgent need to develop effective and environmentally friendly methods to control stored-product pests. S-methoprene, a microbial volatile compound with insecticidal properties, has been identified as a potential candidate for this purpose. However, its efficacy against storage pests is not well understood. In this study, wheat was treated with S-methoprene at a rate of 5 mg/kg and stored in ambient conditions within a grain bin. Samples were collected after 90 and 365 days, and bioassays were conducted on 20 mixed-sex developmental stages of Tribolium castaneum and T. confusum. S-methoprene showed significant ovicidal, pupicidal, and adulticidal activity against T. castaneum and T. confusum. The efficacy of S-methoprene was found to be influenced by the developmental stage of the pests and the timing of its application. In the 90-day treatment group, the hatching rate of three T. castaneum strains was zero, while that of T. confusum strains from Guangdong and Beijing was (1.67±2.04)% and 0%, respectively. S-methoprene treatment in the 90-day group resulted in effective pupicidal activity against both T. castaneum and T. confusum, with the F1 generation of adults being unable to reproduce. However, in the 365-day treatment group, the pupicidal activity significantly decreased, and the F1 generation of adults were able to reproduce but their F1 generation pupae can not hatch. The adulticidal activity of both pests had some effects in both treatments, but the mortality rate significantly decreased in the 365-day treatment group. The F1 generation of T. castaneum only consisted of larvae, while some larvae of T. confusum were able to pupate but could not further develop into adults. T. castaneum was found to be more susceptible to S-methoprene than T. confusum. After S-methoprene induction, the activity of three detoxification enzymes in Tribolium species was affected in varying degrees and had different variation patterns. The activity was positively correlated with induction time.

OBJECTIVE To cohouse cats experimentally infected with Bartonella clarridgeiae (Bc) with naive cats in a flea-free environment or with Ctenocephalides felis, Bartonella henselae (Bh), Mycoplasma haemofelis, and Candidatus Mycoplasma haemominutum to determine which flea could be a vector and to assess whether transmission of the infectious agents could be blocked by fipronil and (S)-methoprene. ANIMALS Specific pathogen-free cats (n = 34). METHODS In experiment 1, Bc was inoculated in 1 cat that was housed with 9 naive cats without C felis. In experiment 2, the 2 cats inoculated with Bc were housed with 6 other cats (2 inoculated with Bh, 2 inoculated with M haemofelis, and 2 inoculated with Candidatus M haemominutum) in the center (enclosure 2) of 3 housing enclosures separated by mesh walls that allow passage of fleas but precludes fighting. C felis were placed only on cats in enclosure 2 (5 times). Cats in enclosures 1 (n = 8) and 2 (8) were untreated, and cats in enclosure 3 (8) were administered fipronil and (S)-methoprene. Blood was collected from all cats for PCR assays for the pathogens. RESULTS None of the cats housed with the cat inoculated with Bc became PCR positive in the absence of C felis. All cats in enclosure 2 became Bc DNA positive. While 2 of 8 cats in enclosure 1 became Bc PCR positive, none of the treated cats in enclosure 3 became infected. CLINICAL RELEVANCE The study demonstrated that C felis can be a vector for Bc. The results support the recommendation that flea control products can reduce the risk of transmission of flea-borne pathogens. [ABSTRACT FROM AUTHOR]

What Is Already Known About This Topic?: Anopheles sinensis ( An. sinensis ) is the predominant malaria vector in China. The impact of S-methoprene on the emergence process of mosquito larvae suggests its potential as a control method for vector mosquitoes. However, the efficacy of S-methoprene in controlling An. sinensis has not yet been demonstrated., What Is Added by This Report?: The effectiveness of S-methoprene against An. sinensis was assessed in laboratory and semi-field conditions in Yunnan Province., What Are the Implications for Public Health Practice?: These results offer valuable options and guidance for utilizing S-methoprene products in malaria reimportation prevention areas within Yunnan Province., Competing Interests: No conflicts of interest., (Copyright and License information: Editorial Office of CCDCW, Chinese Center for Disease Control and Prevention 2024.)

A simple, robust and QC (quality control) friendly high performance liquid chromatography (HPLC) method was developed and validated for simultaneous determination of four active pharmaceutical ingredient [namely fipronil, (S)-methoprene, eprinomectin, and praziquantel] and their key degradation products in a broad-spectrum topical finished product. Typical sample of the finished product contains a total of 30-plus peaks of interest. Analytes were separated on a HALO C18 column (150 mm × 4.6 mm i.d., 2.7 µm particle size) with a gradient elution at 50 °C column temperature and 0.6 mL/min flow rate. Detection wavelength of 245 nm is used for praziquantel, eprinomectin and their degradation products, 265 nm for (S)-methoprene and its degradation products and 280 nm for fipronil and its degradation products and for the antioxidant, BHT. Mobile phase of the method is composed of 10 mM potassium phosphate buffer and 1,4- Dioxane (98/2, v/v, pH 5.0) as mobile phase-A, and EtOH/MeOH/MeCN/IPA (86/4/6/4, v/v/v/v) as mobile phase-B. All analytes of interest were adequately separated by this single HPLC method. The stability-indicating capability of the method has been demonstrated by successfully separating the degradation products in the stressed degraded samples of the finished product. Limit of quantitation (LOQ) and limit of detection (LOD) of the method is 0.3% and 0.1% of target analytical concentration for each individual API in the finished product. This method has been demonstrated to be sensitive, robust, specific, accurate and stability-indicating for analysis of the topical drug product containing praziquantel, fipronil, eprinomectin and (S)-methoprene., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Mosquitoes and mosquito-borne illnesses significantly impact public health and human well-being. To address this concern, environmentally compatible larvicides have become a critical component of integrated mosquito management. However, the number of available larvicides is at a historical low. Currently, larvicides that harness microbials and insect growth regulators account for most products. Screening of new active ingredients (AIs) or improvement of existing AIs is thus necessary to augment the capacity for mosquito control. S-methoprene possesses a similar molecular structure and identical function to mosquito juvenile hormone and has been one of the main targets for research and development. The efficacy and safety of S-methoprene have been well documented since the late 1960s, and numerous products have been commercialized to combat pests of economic importance. However, S-methoprene is vulnerable to environmental factors that lead to its degradation, which has created challenges in formulation development, particularly where extended efficacy is desired. A derivative of S-methoprene, namely S-methobutene, with molecular modification has become available. This derivative has demonstrated an enhanced activity of inhibition of emergence (IE) against species across the Aedes, Anopheles, and Culex genera at IE10, IE50, and IE90. Furthermore, S-methobutene consistently outperformed S-methoprene during a 120-day aging process against the southern house mosquito Cx. quinquefasciatus, where the IE% in S-methobutene was significantly higher than that in S-methoprene on most aging intervals. The former had significantly longer residual activity than the latter. The potential of S-methobutene for further development and application is discussed in consideration of its enhanced activity and stability., (© The Author(s) 2023. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

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Flea infestations of pets continue to persist due to the lack of knowledge of flea biology and ecology. It is not unusual that pet owners believe regular hygiene, such as shampooing their dogs can replace regular insecticidal treatment. The objective of this study was to compare in a flea simulated environment, modelling exposure similar to that found in a home, that the use of regular physiological shampoo does not control fleas adequately when compared to a long acting topical formulation. Three groups of six dogs were formed: one untreated control group, one group treated monthly with the topical formulation of fipronil/(S)-methoprene, and a third group treated weekly with a hygiene shampoo. All dogs were infested with adult unfed Ctenocephalides felis fleas (200 ± 5) on Days -28 and -21. Each animal’s sleeping box was fitted with a plastic cup mounted to the inside roof of the box. The sleeping bench of each animal was covered with a carpet to accommodate flea development. The dogs were maintained in their kennels throughout the study. In order to maintain the environmental flea challenge, C. felis pupae (100 ± 5) were placed in the plastic cup in each animal’s sleeping box on Days -14, -7, 0, 7, 14, 21, 28, 35 and 42. The dogs were combed and fleas counted weekly on Days -1, 3, 10, 17, 24, 31, 38, 45, and 51. The fleas were placed immediately back on the dogs. On Day 60, fleas were counted and removed. Flea infestations in the untreated control group at each count averaged between 46.2 and 74.2 fleas throughout the study. The average number of fleas infesting dogs was significantly different (p < 0.05) between the untreated and the two treatment groups and between the two treatment groups at all counts throughout the two months study (Days 3, 10, 17, 24, 31, 38, 45, 51 and 60). The efficacy was never below 99.1% in the fipronil/(S)-methoprene group, and efficacy in the shampoo group was never above 79.2%. Weekly shampooing in treatment group 3 was intentionally delayed after Day 42, to evaluate wether missing a weekly bath would affect the flea population. The Day 48 data indicate that forgetting or delaying a single weekly shampooing resulted in a clear increase in flea numbers and a significant decrease in efficacy from 68.2% to 34.8%. The fipronil(S)/methoprene treatment allowed a continuous control as demonstrated by the high efficacy against fleas, and also the number of flea-free dogs on seven of the nine weekly assessments, in spite of what was essentially a continuous flea challenge model.

West Nile virus remains the leading cause of arboviral neuroinvasive disease in the United States, despite extensive efforts to control the mosquito vectors involved in transmission. In this study, we evaluated the effectiveness of Altosid SR-20 (active ingredient, S-methoprene 20%) larvicide applications using truck-mounted ultra-low volume (ULV) dispersal equipment to target Culex pipiens Linnaeus (Diptera: Culicidae) and Cx. restuans (Theobald)larvae. A combination of emergence bioassays, open-field measurements of deposited S-methoprene and spray distribution using gas chromatography-mass spectrometry, and assessments of adult Culex spp. populations in response to applications were conducted over the summer of 2020 within the North Shore Mosquito Abatement District (IL, USA). Open-field applications revealed that dispersed Altosid SR-20 using ULV equipment was effective (75% emergence inhibition in susceptible lab strain Cx. pipiens larvae) up to 53 m. In suburban neighborhood applications, we found that S-methoprene deposition and larval emergence inhibition (EI) in front yards did not differ significantly from backyards. An overall EI of 46% and 28% were observed for laboratory strain Cx. pipiens and wild Cx. restuans larvae respectively, and both had an EI significantly higher than the untreated control group. The EI of exposed wild Cx. pipiens larvae did not differ from the untreated controls, suggesting an increased tolerance to S-methoprene. No difference in abundance of gravid or host-seeking adult Culex spp. post-application was detected between treated and untreated sites. These results document the ability of area-wide application to distribute S-methoprene, but this strategy will need further modifications and evaluation for Culex spp. management., (© The Author(s) 2022. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

The sustained speed of kill against Dermacentor reticulatus of two topical combinations, one containing fipronil/amitraz/(S)-methoprene and the other, imidacloprid/permethrin, was evaluated in dogs. Two treated groups and one untreated control group of eight adult Beagle dogs each were randomly formed based on pre-infestation rates and bodyweight. Each treatment was administered topically once on Day 0, according to the recommended label dose and instructions for use. All dogs were infested with 50 adult unfed D. reticulatus starting on Day 1, then weekly, for a total of five weeks. While most studies determine tick efficacy at 48 hours (h), in this study, all remaining ticks were counted and categorized 24 h following each infestation. The numbers of ticks (living or dead) that remained attached on treated dogs were compared to those on the control animals. The percent reduction of attached ticks (disruption of attachment) at 24 h on dogs treated with fipronil/amitraz/(S)-methoprene remained above 92% for four weeks. The reduction of attached ticks at 24 h on dogs treated with imidacloprid/permethrin did not reach 80% during the entire study. The number of ticks attached at 24 h was significantly (p < 0.05) lower in the fipronil/ amitraz/(S)-methoprene group than in the imidacloprid/permethrin group in assessments on Days 2, 15, 22, 29 and 36. When assessing efficacy based upon live ticks on treated versus control dogs, fipronil/amitraz/(S)-methoprene 24 h efficacy was above 95% for four weeks, decreasing to 77.8% at Day 36. The 24 h efficacy of imidacloprid/permethrin ranged from 56.2% to 86.7% through Day 29, never achieving 90% throughout the study. The 24-hour efficacy of fipronil/amitraz/(S)-methoprene was significantly (p < 0.05) higher than imidacloprid/permethrin at all time points, including Day 36.

In the study reported here, the pioneer fipronil/(S)-methoprene topical product (FRONTLINE® PLUS, Merial Limited, Duluth, GA) was compared to the oral spinosad product (COMFORTIS® Elanco, Greenfield, IN) for efficacy against adult fleas and preventing egg production. The product presentations, doses and labelling were the one applicable in the USA. Using a standard protocol, 200 cat fleas of mixed sex were applied to dogs on Days 1, 7, 14, 21, 28, 35, and 42. Dogs were combed to remove fleas 24 hours post-infestation, the fleas were counted, collected, and then reapplied to each dog following completion of their respective count. At 48 hours post-infestation, comb counts were performed and fleas were removed. No fleas were collected from any dog in the fipronil/(S)-methoprene group at any 24 or 48 hours post-infestation assessment throughout the six weeks study, yielding a preventive efficacy of 100%. For the spinosad treatment, efficacy was 100% at 24 hours and 48 hours through Day 16, and thereafter declined. The results observed in the spinosad-treated dogs were highly variable between animals. At the 24 and 48 hours counts following the Day 21 infestation, only five of eight spinosad-treated dogs (62.5%) were flea-free. Following the Day 28 infestation, spinosad efficacy fell to 85% and 89%, for the 24 hours and 48 hours counts, and only two dogs (25%) were flea free, compared to 100% flea-free dogs in the fipronil/(S)-methoprene group. No fleas were collected from the fipronil/(S)- methoprene treated dogs throughout the entire study, therefore, no eggs were collected at any time from any dog in the group. However, in the spinosad group adult fleas were found on dogs starting on Day 21 and by Day 30, 42 eggs were collected from one dog that had 107 adult fleas counted at 48 hours. At Day 37 and Day 49, more than 100 eggs were collected from each dog in the spinosad-treated and control groups.

The acaricidal efficacy against Dermacentor reticulatus in dogs of the commercial topical combinations fipronil/(S)-methoprene (FRONTLINE Combo® spot-on dog), imidacloprid/permethrin (Advantix®) and metaflumizone/amitraz (ProMeris Duo®) was evaluated and compared. Three treatment groups and one untreated control group of six adult Beagle dogs each were randomly formed. Each treatment was administered topically once on Day-0, according to the recommended label dose and instructions for use. All dogs were infested weekly with approximately 50 adult unfed D. reticulatus over a period of seven weeks. Ticks were removed and counted approximately 48 hours after each infestation. The percent reduction in numbers of ticks for fipronil/(S)-methoprene was ≥ 97 % compared to untreated controls for all seven weekly infestations. The percent reductions for imidacloprid/permethrin and metaflumizone/amitraz were satisfactory initially but fell and stayed below 90 % after three weeks. From the third week onwards, fipronil/(S)-methoprene treated dogs had significantly fewer ticks than imidacloprid/ permethrin or metaflumizone/amitraz treated dogs (p < 0.05).

Abstract Background Efficacy of FRONTLINE® TRITAK® For Dogs (fipronil/(S)-methoprene/cyphenothrin, Merial, Inc., Duluth, GA) against Ixodes scapularis was evaluated in two separate, but concurrent laboratory studies. Methods One day after topical treatment with placebo or active, dogs (n = 24) were infested with 50 unfed adult Ixodes scapularis ticks, with repeat infestations on Days 7, 14, 21 and 28. The number of live ticks was counted at 6 hours post-infestation in the first study (n = 12) and at 24 hours post-infestation in the second study (n = 12). Results Observed efficacies in study 1 were 93-99 % at 6 hour assessments on Day 1 through Day 28 and in the second study, 98-100 % at 24 hour assessments, occurring on Day 2 through Day 29. Conclusions A single dose of FRONTLINE® TRITAK® For Dogs (fipronil/(S)-methoprene/cyphenothrin) (0.67 ml or 1.34 ml) prevented the establishment of a new infestation following treatment, as well as the repeated weekly re-infestations with Ixodes scapularis ticks, for 4 weeks.