Applicator of a treatment for an animal, comprising - a chamber including the treatment; - means movable in the chamber to eject the treatment; - actuating means to actuate the movable means; - a control module coupled to the chamber outside thereof, including *a processor, *a sensor unit, designed to measure a length of movement of the movable means in the chamber, when the movable means are actuated through the actuating means before releasing, and *wireless communication means configured to transmit to an external device information concerning or suitable for determining a quantity of said treatment ejected outside the chamber, wherein the treatment is a liquid, and the applicator includes a needle characterised in that: - the applicator further includes a needle guard (18, 19), - the needle guard (18, 19) surrounds the needle to prevent contacts of the needle at rest and is retractable from the needle to allow insertion of the needle in the animal's body under a pressure applied on the needle guard (18, 19) for moving the needle guard (18, 19) to an operative position having a predetermined distance from the position at rest; - the control module includes a needle guard sensor unit adapted to measure a movement of the needle guard (18, 19) with respect to the needle, - the wireless communication means are configured to transmit to the external device information concerning or suitable for determining if the operative position is reached, - the control module is further configured to: - detect a first time (Tb) when the needle guard (18, 19) starts reaching said operative position and a second time (Te) when the needle guard (18, 19) starts moving back to the position at rest, - compare the duration of injection in the operative position, which is the difference between said second time (Te) and said first time (Tb), with the duration of the ejection of fluid outside the chamber, which is the time for moving the movable means for said length, and determine that the treatment has been applied correctly. - a chamber including the treatment; - means movable in the chamber to eject the treatment; - actuating means to actuate the movable means; - a control module coupled to the chamber outside thereof, including *a processor, *a sensor unit, designed to measure a length of movement of the movable means in the chamber, when the movable means are actuated through the actuating means before releasing, and *wireless communication means configured to transmit to an external device information concerning or suitable for determining a quantity of said treatment ejected outside the chamber, wherein the treatment is a liquid, and the applicator includes a needle characterised in that: *a processor, *a sensor unit, designed to measure a length of movement of the movable means in the chamber, when the movable means are actuated through the actuating means before releasing, and *wireless communication means configured to transmit to an external device information concerning or suitable for determining a quantity of said treatment ejected outside the chamber, - the applicator further includes a needle guard (18, 19), - the needle guard (18, 19) surrounds the needle to prevent contacts of the needle at rest and is retractable from the needle to allow insertion of the needle in the animal's body under a pressure applied on the needle guard (18, 19) for moving the needle guard (18, 19) to an operative position having a predetermined distance from the position at rest; - the control module includes a needle guard sensor unit adapted to measure a movement of the needle guard (18, 19) with respect to the needle, - the wireless communication means are configured to transmit to the external device information concerning or suitable for determining if the operative position is reached, - the control module is further configured to: - detect a first time (Tb) when the needle guard (18, 19) starts reaching said operative position and a second time (Te) when the needle guard (18, 19) starts moving back to the position at rest, - compare the duration of injection in the operative position, which is the difference between said second time (Te) and said first time (Tb), with the duration of the ejection of fluid outside the chamber, which is the time for moving the movable means for said length, and determine that the treatment has been applied correctly. - detect a first time (Tb) when the needle guard (18, 19) starts reaching said operative position and a second time (Te) when the needle guard (18, 19) starts moving back to the position at rest, - compare the duration of injection in the operative position, which is the difference between said second time (Te) and said first time (Tb), with the duration of the ejection of fluid outside the chamber, which is the time for moving the movable means for said length, and determine that the treatment has been applied correctly.