CDC Bottle Bioassays for Detection of Insecticide Resistance in Culex Pipiens, Aedes Albopictus, and Aedes Koreicus Collected on US Army Garrisons, Republic of Korea.

Mosquito-borne pathogens are a threat to US troops stationed in the Republic of Korea (ROK). Insecticide resistance has been reported in mosquito vectors in the ROK, highlighting the need for a sustained ROK-wide resistance surveillance program. To address this need from April 2022 until October 2022, larvae and pupae of Aedes albopictus, Ae. koreicus, and Culex pipiens were collected from US Army Garrison (USAG) Daegu (Camps Carroll and Henry), USAG Yongsan-Casey (Camp Casey), and USAG Humphreys (Camp Humphreys) and screened for resistance to insecticides using the Centers for Disease Control and Prevention (CDC) bottle bioassay. No resistance to deltamethrin or chlorpyrifos was detected in Ae. albopictus populations, but one population showed possible resistance to permethrin. Aedes koreicus populations were found to be resistant to etofenprox and permethrin with possible resistance to deltamethrin but were susceptible to chlorpyrifos. Culex pipiens populations were found to be resistant to chlorpyrifos, permethrin, and deltamethrin. Screening using CDC bottle bioassays will continue, and efforts will be made to determine the operational impact of the assay results on military installation mosquito control programs.

High Infection Rates for Adult Macaques after Intravaginal or Intrarectal Inoculation with Zika Virus.

Unprotected sexual intercourse between persons residing in or traveling from regions with Zika virus transmission is a risk factor for infection. To model risk for infection after sexual intercourse, we inoculated rhesus and cynomolgus macaques with Zika virus by intravaginal or intrarectal routes. In macaques inoculated intravaginally, we detected viremia and virus RNA in 50% of macaques, followed by seroconversion. In macaques inoculated intrarectally, we detected viremia, virus RNA, or both, in 100% of both species, followed by seroconversion. The magnitude and duration of infectious virus in the blood of macaques suggest humans infected with Zika virus through sexual transmission will likely generate viremias sufficient to infect competent mosquito vectors. Our results indicate that transmission of Zika virus by sexual intercourse might serve as a virus maintenance mechanism in the absence of mosquito-to-human transmission and could increase the probability of establishment and spread of Zika virus in regions where this virus is not present.

Disease Risk & Landscape Attributes of Tick-Borne Borrelia Pathogens in the San Francisco Bay Area, California.

Habitat heterogeneity influences pathogen ecology by affecting vector abundance and the reservoir host communities. We investigated spatial patterns of disease risk for two human pathogens in the Borrelia genus-B. burgdorferi and B. miyamotoi-that are transmitted by the western black-legged tick, Ixodes pacificus. We collected ticks (349 nymphs, 273 adults) at 20 sites in the San Francisco Bay Area, California, USA. Tick abundance, pathogen prevalence and density of infected nymphs varied widely across sites and habitat type, though nymphal western black-legged ticks were more frequently found, and were more abundant in coast live oak forest and desert/semi-desert scrub (dominated by California sagebrush) habitats. We observed Borrelia infections in ticks at all sites where we able to collect >10 ticks. The recently recognized human pathogen, B. miyamotoi, was observed at a higher prevalence (13/349 nymphs = 3.7%, 95% CI = 2.0-6.3; 5/273 adults = 1.8%, 95% CI = 0.6-4.2) than recent studies from nearby locations (Alameda County, east of the San Francisco Bay), demonstrating that tick-borne disease risk and ecology can vary substantially at small geographic scales, with consequences for public health and disease diagnosis.