US mosquito season opens in May. Vector-control labs surveil for WNV, EEE, Zika, Dengue, and Chikungunya by trapping female mosquitoes, pooling them by species and location, homogenizing each pool, extracting RNA, and amplifying with LAMP isothermal NAAT at 65°C. The workflow runs in ~30 minutes on a portable Genie instrument — no thermocycler required — and feeds positive-pool data into CDC MosquitoNET / ArboNET to trigger local spray response.
Key Facts
- WNV is the leading cause of mosquito-borne human disease in the continental US; ~1 in 5 infections cause febrile illness, ~1 in 150 cause severe neuroinvasive disease.
- EEE has the highest case-fatality rate (~30%) of US arboviruses; Culex / Culiseta are the vectors in freshwater swamps.
- Zika, Dengue, Chikungunya are transmitted by Aedes aegypti / albopictus, established along the Gulf Coast and in US territories.
- LAMP runs at one temperature (~65°C) for ~30 minutes — vs. ~2 hours for real-time RT-PCR — on a portable instrument.
- Pool size is 1–50 mosquitoes of a single species, sex, date, and trap location; results reported as minimum infection rate (MIR) per 1,000.
- CDC MosquitoNET ingests pool data nationally and feeds ArboNET human-case maps that drive spray decisions.
Why May Matters
Adult Culex populations emerge from overwintering as soon as nighttime temperatures climb past about 50°F. By late May, the first WNV-positive pools start to appear across the southern tier — Texas, Louisiana, Arizona, California, Florida — and a few weeks later they appear in the Midwest. Catching the first positive pool of the season is the single most actionable signal a vector-control district produces all year: it sets the timing for larvicide treatments, adulticide spray rounds, and public-health press releases. A district that misses the early signal spends the rest of the summer reacting.
The Five Viruses on the Watch List
US arboviral surveillance focuses on five named viruses, all of which are nationally notifiable conditions:
- West Nile Virus (WNV) — the dominant arbovirus by case volume. Culex pipiens, Culex tarsalis, and Culex quinquefasciatus are the primary vectors. About 1 in 5 infected people develop febrile illness; about 1 in 150 develop neuroinvasive disease that can be fatal. No vaccine and no specific antiviral exist.
- Eastern Equine Encephalitis (EEE) — rare but lethal. Case-fatality rate is roughly 30%, and survivors frequently have permanent neurologic sequelae. The enzootic cycle is Culiseta melanura in freshwater hardwood swamps, with bridge vectors (Aedes, Coquillettidia) carrying the virus to humans and horses.
- Zika virus — an Aedes-borne flavivirus that became a public-health emergency during the 2015–2017 outbreak because of congenital Zika syndrome. Vector surveillance remains active in Florida, Texas, Puerto Rico, and along the Gulf Coast.
- Dengue — locally acquired transmission has been documented in Florida, Texas, Hawaii, Arizona, and California. Aedes aegypti is the primary vector.
- Chikungunya — mostly imported, but locally acquired clusters have occurred in Florida and Texas. Shares the Aedes vector pool with Zika and Dengue, so a single trap haul can be tested for all three.
The Surveillance Workflow: Pool → Homogenize → LAMP
A modern vector-control lab runs this loop nightly during peak season:
- Trap. CDC gravid traps (for Culex) and BG-Sentinel traps (for Aedes) run overnight at fixed sites and at outbreak-response sites. Trap counts feed mosquito-abundance maps independently of the molecular result.
- Sort and pool. Mosquitoes are knocked down on a chill table, sorted by species and sex, and grouped into pools of 1–50 individuals with shared species, sex, date, and trap location. Only females transmit virus, so males are counted but generally not pooled.
- Homogenize. The Mosquito Collection Kit provides matched pool tubes, stainless-steel grinding beads, and viral transport medium. A bead-beater runs ~60–90 seconds per pool; a quick clarifying spin pellets the chitin debris.
- Extract. Magnetic-bead extraction with Pro-Mag scales to dozens of pools at a time. For low-throughput sites, silica-column extraction with Pro-Spin handles a handful of pools per run.
- Amplify. The RNA template goes into a Pro-AmpRT mastermix and runs on a Genie III or Genie HT (see Optigene) at 65°C. Fluorescence onset and the anneal-derivative peak together call the result — positive, negative, or invalid — in ~30 minutes.
- Report. Positive pools are entered into CDC MosquitoNET with species, GPS, trap type, date, and MIR. The data feeds ArboNET, the human-disease arm, where surveillance epidemiologists watch for the first mosquito-to-human bridge.
Why Isothermal NAAT Suits Field Vector Labs
Real-time RT-PCR is the gold-standard reference method, but it has a poor fit for field vector control. Thermocyclers are heavy, expensive, and require stable line power; the typical assay takes ~2 hours; and the instrument footprint is wrong for a regional district office that does mosquito sorting, identification, and testing in the same room.
LAMP changes the calculus. A single 65°C incubation runs to call in ~30 minutes; the Genie III is hand-carry-portable and battery-tolerant; and the assay is robust to the inhibitors that mosquito-homogenate matrices throw at PCR. Pro-AmpRT WNV has been characterized at a sensitivity limit around 3.1 log10 PFU/mL on mosquito pools, with 100% specificity and approximately 98% positive correlation versus reference RT-PCR. Same-day results from the same room where the mosquitoes are sorted means a district can act on a positive pool the morning it is confirmed, not three days later.
"The window between the first positive pool and the first human case is the only place vector control has leverage. Anything that compresses lab turnaround buys back days of spray-response lead time."
Integration with CDC MosquitoNET
MosquitoNET is the CDC's national electronic surveillance backbone for mosquito trap counts and pool test results. State and local vector programs upload species identification, pool size, trap metadata, GPS, and test result; the platform calculates MIR and vector index by week and county and pushes the aggregated layer into ArboNET. ArboNET is where human-case data, equine cases, and dead-bird surveillance are layered on top — producing the weekly arboviral activity maps the CDC publishes every Tuesday from June through October.
A vector-control district running same-day LAMP can post a positive pool to MosquitoNET the same evening it is collected. That visibility, multiplied across ~600 vector-control entities nationally, is the difference between a coordinated national response and a patchwork of surprises.
Reagent & Equipment Stack
The full Pro-Lab molecular stack for a vector-surveillance bench is small and self-contained:
- Mosquito Collection Kit — pool tubes, beads, transport medium.
- Pro-Mag magnetic-bead RNA extraction (high throughput) or Pro-Spin silica columns (low throughput).
- Pro-AmpRT WNV isothermal LAMP assay — the validated WNV pool test.
- Optigene Genie III / Genie HT — portable isothermal fluorometer with anneal-derivative calling.
Frequently Asked Questions
Which mosquito-borne viruses do US vector labs surveil for?
The primary US arboviral targets are West Nile Virus (WNV), Eastern Equine Encephalitis (EEE), St. Louis Encephalitis, La Crosse, Zika, Dengue, and Chikungunya. WNV is by far the most common cause of mosquito-borne human disease in the continental US; EEE has the highest case-fatality rate. Zika, Dengue, and Chikungunya are tracked primarily along the Gulf Coast and in territories where Aedes aegypti is established.
Why use LAMP instead of RT-PCR for mosquito surveillance?
LAMP runs at a single temperature (~65°C) and finishes in roughly 30 minutes, versus ~2 hours for real-time RT-PCR. The instrument is small, field-deployable, and tolerant of common PCR inhibitors found in mosquito homogenate. Pro-AmpRT WNV has demonstrated 100% specificity and approximately 98% positive correlation with reference RT-PCR on mosquito pools.
How many mosquitoes go into one pool?
CDC-recommended pool sizes are 1–50 mosquitoes of a single species, sex, collection date, and trap location. Most state labs pool at 25–50. The pool result is reported as a minimum infection rate (MIR) per 1,000 mosquitoes tested.
What is CDC MosquitoNET?
MosquitoNET is the CDC's national electronic surveillance system for mosquito trap and pool testing data. Vector districts and state public-health labs upload species counts and pool results; the platform feeds ArboNET human-case maps and drives weekly arboviral activity reporting.
Can the same workflow detect Zika, Dengue, and Chikungunya?
Yes — collect, homogenize, extract, and amplify is virus-agnostic. Only the LAMP primer set changes. Pro-AmpRT WNV is the validated kit for West Nile; equivalent isothermal assays for Zika, Dengue, and Chikungunya can be run on the same Genie III / HT platform with the appropriate primer mix.
For more information about the arbovirus surveillance stack, contact info@pro-lab.us or visit the Mosquito Collection Kit and Pro-AmpRT WNV product pages.