Head lice / louse
The head louse (Pediculus humanus capitis) is an obligate ectoparasite of humans that causes head lice infestation (pediculosis capitis).[1]
Head lice are wingless insects spending their entire lives on the human scalp and feeding exclusively on human blood.[1] Humans are the only known hosts of this specific parasite, while chimpanzees host a closely related species, Pediculus schaeffi. Other species of lice infest most orders of mammals and all orders of birds,[1] as well as other parts of the human body.
Lice differ from other hematophagic ectoparasites such as fleas in spending their entire lifecycle on a host.[2] Head lice cannot fly, and their short, stumpy legs render them incapable of jumping, or even walking efficiently on flat surfaces.[2]
The non-disease-carrying head louse differs from the related disease-carrying body louse (Pediculus humanus humanus) in preferring to attach eggs to scalp hair rather than to clothing. The two subspecies are morphologically almost identical, but do not normally interbreed, although they will do so in laboratory conditions. From genetic studies, they are thought to have diverged as subspecies about 30,000–110,000 years ago, when many humans began to wear a significant amount of clothing.[3][4] A much more distantly related species of hair-clinging louse, the pubic or crab louse (Pthirus pubis), also infests humans. It is visually different from the other two species and is much closer in appearance to the lice which infest other primates.[5] Lice infestation of any part of the body is known as pediculosis.[6]
Head lice (especially in children) have been, and still are, subject to various eradication campaigns. Unlike body lice, head lice are not the vectors of any known diseases. Except for rare secondary infections that result from scratching at bites, head lice are harmless, and they have been regarded by some as essentially a cosmetic rather than a medical problem. Head lice infestations might be beneficial in helping to foster a natural immune response against lice which helps humans in defense against the far more dangerous body louse, which is capable of transmission of dangerous diseases.[7]
Waco
Waco (/ˈweɪkoʊ/ way-koh) is a city which is the county seat of McLennan County, Texas, United States.[3] It is situated along the Brazos River and I-35, halfway between Dallas and Austin. The city had a 2010 population of 124,805, making it the 22nd-most populous city in the state.[4] The US Census 2015 population estimate is 132,356.[5] The Waco Metropolitan Statistical Area consists of McLennan and Falls Counties, which had a 2010 population of 234,906.[6] Falls County was added to the Waco MSA in 2013. The US Census 2016 population estimate for the Waco MSA is 265,207.[7]
Indigenous peoples occupied areas along the river for thousands of years. In historic times, the area of present-day Waco was occupied by the Wichita Indian tribe known as the “Waco” (Spanish: Hueco or Huaco).
In 1824, Thomas M. Duke was sent to explore the area after the Waco people tried to defend themselves and their lands from settlers. His report to Stephen F. Austin, described the Waco village:
After further violence due to settler incursion, Austin halted an attempt to destroy their village in retaliation. In 1825, he made a treaty with them. The Waco were eventually pushed out of the region, settling north near present-day Fort Worth. In 1872, they were forced onto a reservation in Oklahoma with other Wichita tribes. In 1902, the Waco received allotments of land and became official US citizens. Neil McLennan settled in an area near the South Bosque River in 1838.[8] Jacob De Cordovabought McLennan’s property[9] and hired a former Texas Ranger and surveyor named George B. Erath to inspect the area.[10]In 1849, Erath designed the first block of the city. Property owners wanted to name the city Lamartine, but Erath convinced them to name the area Waco Village, after the Indians who had lived there.[11] In March 1849, Shapley Ross built the first house in Waco, a double-log cabin, on a bluff overlooking the springs. His daughter Kate was the first settler child to be born in Waco.[12]