Three mosquitoes collected near Sarasota, Florida, have tested positive for malaria amid an unusual cluster of locally acquired cases. It is the first time in two decades that US mosquitoes have tested positive for malaria in connection with US-based cases.
Four cases have been confirmed in Florida so far, all close to each other, health officials reported Monday. The Sarasota Herald-Tribune reported Wednesday that officials are investigating a possible fifth case.
While efforts to contain the outbreak are underway, officials have been capturing and testing local mosquitoes. In a statement to CBS News, the Sarasota County Mosquito Management Services manager said the three positive bugs were among more than 100 sent to the Centers for Disease Control and Prevention for testing.
Meanwhile, efforts to stamp out the flare-up include door-to-door efforts to inform residents of the cases, as well as spraying insecticides from trucks and planes.
The mosquitoes that transmit the malaria parasite are from the Anopheles sex. There are several types of it Anopheles mosquitoes in the US, which have been found in at least 32 states.
In this case the Anopheles species caught spreading the parasite is a type of night biter – usually not active during the day or evening, like some others Anopheles kind. The species also tends to concentrate and breed around freshwater marshes. So says Christopher Lesser, the director of the Manatee County Mosquito Control District, who spoke to the Herald-Tribune. (Manatee County, just north of Sarasota, is also responding to the cases).
The cluster of locally acquired malaria cases around Sarasota — as well as an unrelated case in Texas — marks the first time the parasite is known to have spread in the US since 2003, when there was a cluster of cases in Palm Beach, Florida. In that outbreak, no captured mosquitoes were found to be positive for malaria.
However, an investigation surrounding a cluster of locally acquired cases in Loudon County, Virginia, revealed malaria-positive mosquitoes in 2002. It was the first time since 1957 that US mosquitoes linked to locally acquired cases tested positive for a malaria parasite.
In a national health alert on Monday, the CDC urged clinicians to look for malaria cases in people without travel-related risks, particularly in areas near the cases in Florida and Texas. The clusters highlight the potential for reintroduction and re-emergence in the US given global travel and climate change. But the CDC notes that overall, the “risk of locally acquired malaria remains extremely low in the United States.”