Invasive Australian Mosquito Found in Portland

A single Aedes notoscriptus mosquito was discovered during routine mosquito monitoring at the Bybee Lake Pumphouse near Kelley Point Park in North Portland on August 25.

The mosquito was identified by a county ecologist due to its distinct head markings, which differ from local species. Confirmation came from a laboratory in Los Angeles.

County health officials highlighted the mosquito's ability to carry several vector-borne diseases, including West Nile virus and chikungunya, which are already present in the United States.

The species is also known to transmit yellow fever, Ross River virus, Barmah Forest virus, Japanese encephalitis virus, and Rift Valley fever virus—none of which are currently found in the U.S. It is the main carrier of dog heartworm in Australia.

Since the discovery, the Multnomah County team has conducted additional mosquito trapping in the area but has not found more Aedes notoscriptus mosquitoes. Officials note the species has a limited flight range and plan to focus surveillance within a half-mile radius.

The Aedes notoscriptus was first detected in Los Angeles in 2014 and has since become established there. This is not the first invasive mosquito found in Multnomah County, as Aedes japonicus was detected in 2006 and has since become established.