Gary O. Maupin

Use of Novel Compounds for Pest Control: Insecticidal and Acaricidal Activity of Essential Oil Components from Heartwood of Alaska Yellow Cedar

Abstract Laboratory bioassays were conducted to determine the activity of 15 natural products isolated from essential oil components extracted from the heartwood of Alaska yellow cedar, Chamaecyparis nootkatensis (D. Don) Spach., against Ixodes scapularis Say nymphs, Xenopsylla cheopis (Rothchild), and Aedes aegypti (L.) adults. Four of the compounds from the essential oil have been identified as monoterpenes, five as eremophilane sesquiterpenes, five as eremophilane sesquiterpene derivatives from valencene and nootkatone, and one as a sesquiterpene outside the eremophilane parent group. Carvacrol was the only monoterpene that demonstrated biocidal activity against ticks, fleas, and mosquitoes with LC50 values after 24 h of 0.0068, 0.0059, and 0.0051% (wt:vol), respectively. Nootkatone from Alaska yellow cedar was the most effective of the eremophilane sesquiterpenes against ticks (LC50 = 0.0029%), whereas the nootkatone grapefruit extract exhibited the greatest biocidal activity against fleas (LC50 = 0.0029%). Mosquitoes were most susceptible to one of the derivatives of valencene, valencene-13-aldehyde (LC50 = 0.0024%), after 24 h. Bioassays to determine residual activity of the most effective products were conducted at 1, 2, 4, and 6 wk after initial treatment. Residual LC50 values for nootkatone did not differ significantly at 4 wk posttreatment from the observations made at the initial 24-h treatment. The ability of these natural products to kill arthropods at relatively low concentrations represents an alternative to the use of synthetic pesticides for control of disease vectors.

Transmission of the Agent of Human Granulocytic Ehrlichiosis by Ixodes spinipalpis Ticks: Evidence of an Enzootic Cycle of Dual Infection with Borrelia burgdorferi in Northern Colorado

Previous work described an enzootic cycle of Borrelia burgdorferi sensu lato (hereafter referred to as B. burgdorferi) maintained by the rodent Neotoma mexicana and the tick Ixodes spinipalpis in northern Colorado. We investigated the incidence of coinfection among rodents with the agent of human granulocytic ehrlichiosis (aoHGE). aoHGE was detected in 23.5% of 119 rodent spleens examined. Biopsy results indicated that 78 (65.5%) of the 119 rodents were positive for B. burgdorferi, whereas 22 (78.5%) of the 28 animals that harbored aoHGE were also infected with B. burgdorferi. In 14 of 25 I. spinipalpis tick pools, aoHGE was detected by amplifying both the 16s rRNA and p44 gene of aoHGE. The ability of I. spinipalpis to transmit aoHGE was examined in C3H/HeJ mice. aoHGE was detected in their blood 5 days after I. spinipalpis infestation. This study confirms that both B. burgdorferi and aoHGE can be transmitted by I. spinipalpis ticks and that there is a high incidence of coinfection in rodents, predominantly Peromyscus maniculatus and N. mexicana, that inhabit the foothills of northern Colorado.

Control of immature Ixodes scapularis (Acari: Ixodidae) on rodent reservoirs of Borrelia burgdorferi in a residential community of southeastern Connecticut

Abstract A 3-yr community-based study was conducted on residential properties on Mason’s Island, Mystic, CT, to determine the efficacy of a rodent-targeted acaricide (fipronil) to control immature Ixodes scapularis (Say) on Peromyscus leucopus. Results indicated that modified commercial bait boxes were effective as an acaricide delivery method for reducing nymphal and larval tick infestations on white-footed mice by 68 and 84%, respectively. Passive application of fipronil significantly reduced the infection rate of Borrelia burgdorferi among white-footed mice by 53%. Moreover, the abundance of questing I. scapularis adults on treated properties was reduced by 77% and fewer were infected with spirochetes (31%) compared with untreated sites (47%) after 3 yr of treatment. Likewise, the abundance of host-seeking nymphs was significantly reduced on treated properties by >50%. Finally, infection rates in flagged nymphal ticks for both B. burgdorferi and Anaplasma phagocytophilum were reduced by 67 and 64%, respectively, after only 2 yr of treatment. Results from this 3-yr trial indicate that the use of fipronil passively applied to reservoir animals by bait boxes is an environmentally acceptable means to control ticks, interrupt the natural disease transmission cycle, and reduce the risk of Lyme disease for residents of treated properties.

Assessing the prevention effectiveness of local Lyme disease control.

The effectiveness of any public health intervention is determined by its theoretical efficacy and by the level of engagement of the target population. A computer simulation model and basic epidemiologic concepts were used to estimate the effectiveness of interventions for preventing Lyme disease in a hypothetical community. The process for estimating numbers of Lyme disease cases prevented by each intervention is described. This assessment compares the effectiveness of alternative community-based prevention strategies, illuminates the limitations and distributive effects of interventions, and helps clarify available prevention options for community residents.

Infection of Ixodes scapularis (Acari: Ixodidae) with Borrelia burgdorferi Using a New Artificial Feeding Technique

Abstract To study interactions between Ixodes scapularis (Say) and Borrelia burgdorferi, an artificial feeding system was refined to allow controlled manipulation of single variables. The feeding system uses a mouse skin mounted on a water-jacketed glass membrane feeder. I. scapularis were infected using either BSK-H-cultured B. burgdorferi spirochetes or a B. burgdorferi-infected mouse skin as the source of spirochetes. Sixty-six percent of nymphs successfully fed to repletion using the artificial feeding systems with at least 75% of nymphs becoming infected with B. burgdorferi. Strain B31 B. burgdorferi spirochetes from passages 2–17 were equally infectious to nymphal ticks. At concentrations of one spirochete per microliter, 12% of nymphs acquired infection and 14 and 100 spirochetes per microliter resulted in 50 and 100% infection rates, respectively. Eighty-nine percent of nymphs fed by artificial feeding molted to the adult stage. When subsequently fed as adults, these I. scapularis successfully transmitted infectious B. burgdorferi spirochetes to mice.