Wednesday, September 30, 2015

Super-strains of lice spread to 25 states: Are they in yours?

As students head back to school, they'll increasingly be bringing home some very unwanted guests: head lice. Lice, long the bane of parents and kids across the country, are becoming a much worse problem: Strains of the pesky parasites that are resistant to most over-the-counter treatments have now been found in at least 25 states. 

The spread of an ultra-strain of lice means you'll need to use a higher dose of chemical to kill them.    

Lice — and other insects — are increasingly becoming resistant to pyrethroids, the active ingredients in most OTC concoctions, according to Kyong Yoon, an assistant professor at Southern Illinois University—Edwardsvillle. Yoon was part of the research team that initially discovered the new ultra-resistant strains. 

In a new study, Yoon and his colleagues decided to find out how widespread these resistant strains were.
"We collected 109 lice populations and 104 had high levels of gene mutations," Yoon reported at the annual meeting of the American Chemical Society in August.   MORE

Researchers are finding that head lice that are becoming resistant to OTC treatments. Red states: 100 percent of the tested lice were resistant. Orange states: 50 to 90 percent of lice were resistant. Yellow states: 1 percent to 49 percent were resistant. Blue states: Data hasn't been analyzed yet. White states haven't been tested.

Tuesday, September 29, 2015

Head Lice

From: Center for Disease Control and Prevention - CDC


Causal Agent:

Pediculus humanus capitis, the head louse, is an insect of the order Psocodea and is an ectoparasite whose only host are humans. The louse feeds on blood several times daily and resides close to the scalp to maintain its body temperature.

Life Cycle:

Pictoral representation of the life cycle of a head louse.
The life cycle of the head louse has three stages: egg, nymph, and adult.
Eggs: Nits are head lice eggs. They are hard to see and are often confused for dandruff or hair spray droplets. Nits are laid by the adult female and are cemented at the base of the hair shaft nearest the scalp The number 1. They are 0.8 mm by 0.3 mm, oval and usually yellow to white. Nits take about 1 week to hatch (range 6 to 9 days). Viable eggs are usually located within 6 mm of the scalp.
Nymphs: The egg hatches to release a nymph The number 2. The nit shell then becomes a more visible dull yellow and remains attached to the hair shaft. The nymph looks like an adult head louse, but is about the size of a pinhead. Nymphs mature after three molts (The number 3, The number 4) and become adults about 7 days after hatching.
Adults: The adult louse is about the size of a sesame seed, has 6 legs (each with claws), and is tan to grayish-white The number 5. In persons with dark hair, the adult louse will appear darker. Females are usually larger than males and can lay up to 8 nits per day. Adult lice can live up to 30 days on a person’s head. To live, adult lice need to feed on blood several times daily. Without blood meals, the louse will die within 1 to 2 days off the host.  MORE

In Lice, Clues to Human Origin and Attire

From:  NY Times 

Published: March 8, 2007
One of the more embarrassing mysteries of human evolution is that people are host to no fewer than three kinds of louse while most species have just one.   
 One of the more embarrassing mysteries of human evolution is that people are host to no fewer than three kinds of louse while most species have just one.
Even bleaker for the human reputation, the pubic louse, which gets its dates and residence-swapping opportunities when its hosts are locked in intimate embrace, does not seem to be a true native of the human body. Its closest relative is the gorilla louse. (Don’t even think about it.)

Louse specialists now seem at last to have solved the question of how people came by their superabundance of fellow travelers. And in doing so they have shed light on the two major turning points in the history of fashion: when people lost their body hair, and when they first made clothing.  MORE

Lice Shed Light on Ancient History of Americas

From:  Live Science 

by Charles Q. Choi, Live Science Contributor   |   February 12, 2008 05:46am ET

A Chiribaya mummy from Peru showing intact hair that is still braided. Lice from the hair of such mummies is shedding light on the migration patterns of America’s earliest humans.
Credit: Dr. Sonia Guillen.

Head lice from 1,000-year-old mummies in Peru are shedding light on the spread of humans and diseases to the Americas.

These new findings suggest, for example, that Columbus did not bring these parasites to the New World — although Vikings might have, scientists added.

"It's kind of quirky that a parasite we love to hate can actually inform us how we traveled around the globe," said researcher David Reed of the Florida Museum of Natural History in Gainesville.MORE

Of lice and men: An itchy history