Is one required to wash his hands after touching insects and non-Kosher animals?
Background: Certain actions that are performed cause a spirit of impurity to reside onto the hands and hence requires one to [immediately] wash his hands afterwards with water in order to get rid of the impurity. Amongst these actions, the Poskim list that one who touches lice is required to wash his hands one time [immediately] afterwards in order to get rid of the impure spirit. The question is thus raised as to whether this ruling is limited to lice, or applies to any non-Kosher animal or creature.
The debate: From the fact the above Poskim list specifically the touching of lice to require the washing of hands, and do not generalize this to all non-Kosher animals or creatures, implies that in truth there is no requirement to wash hands after touching any other animal or creature, and indeed, so is the ruling of some Poskim that handwashing with water is not required after touching any animal or creature other than lice. So is likewise implied from the ruling of Admur in which he explicitly states that one who touches a non-kosher animal or creature in the middle of prayer is not required to wash his hands. Nonetheless, there are Poskim who rule that just as one is required to wash his hands if he touched a gentile or a Jewish heretic so too, he is required to wash his hands after touching any non-Kosher animal or creature, in order to remove the evil spirt that resides.
The final practice: Practically, although some Poskim conclude to be stringent, the widespread custom is to be lenient in this matter [both regarding one who touches non-Kosher animals and gentiles], and those who choose to be stringent are to be even more stringent to wash hands after touching a gentile or apostate Jew. [However, to be stringent regarding non-Kosher animals and creatures, but not regarding a gentile is seemingly baseless.] In any event, some Poskim conclude that those who touch a gnat [or other non-Kosher animals and creatures] are to clean their hands in other ways, even though water is not required to be used.
 Seder Hayom; Magen Avraham 4:18; Elya Raba 4:12; Peri Megadim 4:18; Kaf Hachaim 4:63; M”B 4:38; Omitted by Admur. Vetzaruch Iyun.
The reason: In order to immediately remove the spirit of impurity from one’s hands and not delay it. [Poskim ibid]
 See Admur Kama 4:18; Michaber 4:18; Beis Yosef 4:18; Abudarham p. 369 in name of Tashbeitz; Kol Bo 23; Mordechai Brachos Remez 194; Orchos Chaim Hilchos Netilas Yadayim 10
 Admur Kama 4:18; 97:3; Michaber 4:18
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]
 This applies even if he did not kill the lice and merely touched it. [Admur 97:3; See Kaf Hachaim 4:84] See Ashel Avraham Butchach that even looking at lice with intent of discarding requires washing.
 The reason: As the impure spirit resides on the hands upon touching lice. [Admur 97:3]
 So rule regarding a Parush [gnat] and the same would apply to all other creatures: Shaareiy Teshuvah 4:12; Artzos Hachaim Hameir La’aretz 83; M”B 4:45
 The reason: As the main reason that washing is required upon touching lice is because they are created from sweat, and sweat carries the evil spirit. This is not relevant to any other creature, including gnats. [Poskim ibid]
 Admur 97:3 in parentheses, as understood by Kaf Hachaim 4:81 to be in negation of those Achronim [brought next] who require hand washing for other creatures
Analysis on opinion of Admur: Admur in 97:3 rules in parentheses that one is not required to wash hands during Davening if one touched an impure animal. However, it can be rightfully argued that there Admur was not discussing whether doing so causes an evil spirit to reside on one’s hands and rather simply if it prohibits Torah learning and prayer, as he himself differentiates in that Halacha between lice found in an area with sweat and those found in another area, as well as he differentiates there between washing with water to get rid of the evil spirit and rubbing on earth to clean so one can Daven. Thus, no definite proof of Admur’s opinion can be brought from this Halacha. [See Piskeiy Teshuvos 4 footnote 256]
 Yifei Laleiv 1:24; Kaf Hachaim 4:81
 Lev Chaim 2:6; Ruach Chaim 2; Yifei Laleiv 1:24; Kaf Hachaim 4:81
The reason: As they are considered like dead even when they are alive. [Poskim ibid]
 Kaf Hachaim ibid concludes to be stringent like the Yifei Laleiv, despite the implied ruling of Admur ibid
 Shaareiy Teshuvah 4:12; Artzos Hachaim Hameir La’aretz 83; M”B 4:45
Opinion of Admur: From Admur 97:3 it is implied that even a mere cleaning without water is not necessary.