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The Itchy History Of Head Lice And Bacterial Pathogens

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As with every year, the fall and winter seasons are marked with the arrival of a number of different health issues. For most, colds and flu are at the top of the list. But another pathogen also seems to thrive at this time of year. Though it is officially known as Pediculus humanus capitis, most people know it simply as the head louse.

Lice are an unfortunate part of human existence. These small ectoparasites find their way into the hair and then make a home where they can eat, grow, and reproduce. They are common worldwide and as any parent knows, symptoms are frustrating and treatment is arduous and at times ineffective.

The torment of the louse is not a modern problem. These creatures have been infecting humans for millennia. They have been found in mummies ranging back thousands of years and some studies suggest these creatures have been bugging around since the dawn of evolution.

Although the itchiness that comes with infection may seem bad enough, lice also pose another threat. Much like humans, they also have a microbial population living in and on their bodies. Some of these species are known to be pathogens of humans, including the potentially lethal louse-borne fever and the plague. How these bacteria ended up in these pests has been a mystery. No one knows if these species have always been in lice or if this is another example of evolution over time.

For an international group of researchers, the best option to find that answer was to look back to a different time when medicine wasn't as robust as it is today. They decided to take a historical look at lice infections with the hope of finding evidence to link the louse with infectious diseases.

For this study, the team went back to the Roman period, about 2,000 years ago. They examined louse combs from those periods and managed to find both lice and eggs. Though the creatures were not alive, they were intact meaning genetic analysis could be performed. The group then isolated the genetic material and then attempted to identify the type of lice as well as the presence of any human pathogens. When the results came back, several surprises were in store.

The first was the nature of the lice discovered. The team expected the lice to be ancestors of current Mediterranean versions. Some were but not all. The genetic analyses also revealed some of the bugs apparently originated from America.

Considering this region had yet to be discovered by Europeans, the finding was indeed suspicious. For the authors, there was a relatively easy explanation. America had been originally populated by Asians who had traversed from Russia. These people most likely brought the lice with them to the new world.

The second surprise was the nature of the pathogens isolated. The team hoped to find the causes of louse-borne fever, plague, and others. However, they were not detected. Only one species showed up, Acinetobacter baumannii. This bacterium is best known for causing pneumonia but can also find its way into the bloodstream - such as from lice bites - and eventually cause a potentially lethal condition known as bacteremia.

The results of the study may not have been as expected but they do impact how we see lice and health. These pests have adapted over time to incorporate pathogens as they became introduced into humans. As we suffered, the creatures evolved, making them an even greater threat to our health as a vector of infectious disease.

Granted, in recent times, the risk for lethal pathogens through lice has not been overly concerning. By killing the pests, we remove the threat. Yet, the rise in resistance to insecticides suggests people may end up suffering for longer periods of time thereby increasing the chances for pathogens to end up in the blood.

This study also highlights the need for lice prevention. Thankfully, we are awash in information from governments and organizations working to help us stay safe. For anyone who has a fear of these pests - for example, parents - the best way to approach this infection is to pay attention to the guidelines, keep an eye on your children, and be sure to report any sign of the insects.

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