One who touches lice is required to wash his hands one time [immediately] afterwards. [This applies even if one only touched it with his pinky.]
Removing lice from ones clothing: One who checks his clothing for lice is required to wash his hands one time [immediately] afterwards even if he did not find any lice.
Checking hair for lice:
One who checks someone’s hair for lice is required to wash his hands one time [immediately] afterwards even if he did not find any lice.
Must one wash his hands if he removed lice using a cloth?
Is one to wash his hands after touching other insects and impure animals?
Some Poskim rule one is to wash his hands if he touched an impure animal. Others rule it is not necessary to wash hands after touching an impure animal.
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 Kama 4/18
 This applies even if he did not kill the lice and merely touched it. [See Kaf Hachaim 4/84] See Ashel Avraham Butchach that even looking at lice with intent of discarding requires washing.
 The Reason: The impure spirit resides on the hands upon touching lice. [Admur 97/3]
Other Opinions: Some Poskim rule that touching lice does not bring an impure spirit and hence does not require washing with water. Rather the hand requires cleaning in any fashion in order to be allowed to learn Torah. [See Machatzis Hashekel 4/17; Nivei Shalom 4/12; Machazik Bracha brought in Shaareiy Teshuvah 4/12; Soles Belula 4/14 in name of Makor Chaim; Ben Ish Chaiy Toldos 17] Admur however rules that it causes impurity, and hence he rules only washing with water helps. So also rules Kisei Eliyahu ibid; Yifei Laleiv 4/18 in name of Mor Uketzia; Peri Megadim 4 M”Z 14; and so is implied from many Poskim. [brought in Kaf Hachaim 4/60]
 Ketzos Hashulchan 2/11; Kaf Hachaim 4/64 in name of Peri Megadim
 Kaf Hachaim 4/83
 Admur 97/3
 Yifei Laleiv 1/24; Lev Chaim 2/6; Ruach Chaim 2; Kaf Hachaim 4/81
 Shaareiy Teshuvah 4/12; M”B 4/45; Admur 97/3 regarding that one is not required to wash hands before Davening if one touched an impure animal, however it can be rightfully argued that there Admur was not discussing whether doing so resides an evil spirit and hence no proof can be brought. [See also Piskeiy Teshuvos 4 footnote 256]
Must one clean his hands in other ways? Shaareiy Teshuvah and M”B ibid rule one is to clean the hands in other ways. However from Admur ibid it is implied that this too is not necessary.