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]
Laredo
Laredo (/ləˈreɪdoʊ/ lə-ray-doh; Spanish: [laˈɾeðo]) is the county seat of Webb County, Texas, United States, located on the north bank of the Rio Grande in South Texas, across from Nuevo Laredo, Tamaulipas, Mexico. According to the 2010 census, the city population was 236,091, making it the tenth-most populous city in the state of Texas and third-most populated on the Mexico–United States border, after San Diego, California, and El Paso, Texas.[5] Its metropolitan area is the 178th-largest in the U.S. and includes all of Webb County, with a population of 250,304.[5] Laredo is also part of the cross-border Laredo-Nuevo Laredo Metropolitan Area with an estimated population of 636,516.[6]
Because Laredo is 95.6 percent Hispanic and Latino, it is one of the least ethnically diverse cities in the United States. When economic diversity, household diversity and social class diversity, are considered, Laredo is rated the 19th least diverse city overall out of the 313 largest cities in the nation.[7]
Laredo’s economy is based on international trade with Mexico. Most major transportation companies have a facility in Laredo. The city’s location on the southern end of I-35 close to the manufacturers in northern Mexico promotes its vital role in trade between the two nations. Laredo International Airport is within the Laredo city limits, while the Quetzalcoatl International Airport is nearby in Nuevo Laredo on the Mexican side.