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]
Altoona
Altoona is a city in south central Pennsylvania Blair County, Pennsylvania, United States. It is the principal city of the Altoona Metropolitan Statistical Area (MSA). The population was 46,320 at the time of the 2010 Census, making it the eleventh most populous city in Pennsylvania. The Altoona MSA includes all of Blair County and was recorded as having a population of 127,089 at the 2010 Census,[6] around 100,000 of whom live within a 5-mile (8.0 km) radius of the Altoona city center according to U.S. Census ZIP Code population data. This includes the adjacent boroughs of Hollidaysburg and Duncansville, adjacent townships of Logan, Allegheny, Blair, Frankstown, Antis, and Tyrone, as well as nearby boroughs of Bellwood and Newry.
Having grown around the railroad industry,[7] the city is currently working to recover from industrial decline and urban decentralization experienced in recent decades. The city is home to the Altoona Curve baseball team of the Double A Eastern League, which is the affiliate of the Major League Baseball team Pittsburgh Pirates. It also houses the 75-plus-year-old Altoona Symphony Orchestra,[8] under the direction of Teresa Cheung. Prominent landmarks include the Horseshoe Curve, the Railroaders Memorial Museum, the Juniata Shops of the Altoona Works, the Mishler Theatre, the Cathedral of the Blessed Sacrament, and the Jaffa Shrine Center.