This page is based on a description from Belinda G. Lehmkuhle of Loba as played in Central America, which is a version of Contract Rummy.
Eduardo Valcarcel writes that in Argentina a similar game called Carioca is played. The differences between Carioca and Central American Loba are described at the end of this page. There is also a somewhat different game called Loba which is played in Argentina. This is described on a separate page.
Central American Loba requires two ordinary 52 card decks plus 4 jokers, making 108 cards in all. It is usually played with from 2 to 4 players, but can be played with as many as 5.
9-
9-9 is a valid Trio.
4-5-6-7 - like a Straight Flush in Poker, but with four cards, not five. The ace can be counted high or low, at the player's choice - so 
J-Q-K-A and A-2-3-4 are both valid escaleras. Ace cannot be both high and low at once, so K-A-2-3 is not valid.
Loba is a series of six rounds. In each round, the players strive to get rid of all their cards, and when one any player manages this, the round is over. The other players receive a penalty based on adding up the point values of the cards left in their hands. The player with the fewest points at the end of the six rounds is the overall winner.
The first dealer is chosen at random. The deal and play are counter-clockwise, so the next round will be dealt by the player to the right of the dealer for the current round.
Each player is dealt eleven cards. The next card is placed face up on the table, to start the discard pile, and the remaining stock of undealt cards is placed face down beside it. This is the draw pile.
Play begins with the player to the right of the dealer, and players take turns in counter-clockwise order. A player's turn consists of three parts:
The object is to get rid of all the cards from your hand, and this can only be achieved by putting down cards (sometimes called melding). In order to be allowed to put down any cards at all you must first collect in your hand the combination required for the round being played. This is called the contract, and it becomes more difficult on each successive round. The contracts are:
Round 1 - dos (two) trios (6 cards)
Round 2 - un (one) escalera, un trio (7 cards)
Round 3 - dos escaleras (8 cards)
Round 4 - tres (three) trios (9 cards)
Round 5 - dos trios un escalera (10 cards)
Round 6 - dos escaleras un trio (11 cards)
When a player has the complete combination of cards required for that round, he may put them down, face up on the table, in front of himself. Note that he is not required to put down as soon as he is able to do so - he can wait until a later turn if he wishes. Also, he must have the complete set of cards before he can put down. For example, in the first round, he may not put down just one trio - he must put down two at once. When putting down the combination required for the round, the player may not put down any additional cards with them on this turn - the set must be exactly as determined by the round. Extra cards can be added in later turns.
In all but the very last round, after a player has put down his initial contract, the play continues as usual to the right. (In the final round however, the first player to put down gets rid of all of the cards in his hand, thus ending that round.)
Once a player has put down the initial contract for the round, he is allowed in subsequent turns to put down cards from his hand to extend any trios or escaleras which are already on the table - his own or other people's. A trio can be extended by playing further cards of the same rank, and an escalera can be extended by adding cards to either end of the sequence. An ace can count as high or low, but not both at once. It is theoretically possible to have a sequence with aces at both ends: A-2-3-4-5-6-7-8-9-10-J-Q-K-A, the first ace being low and the second high.
For example, if a trio of 4-4-4 is on the table, a player may add one or more fours to that stack. Or, if someone has put down the escalera 3-4-5-6, he may add either a 2 or a 7 to the escalera.
A player who has put down his initial contract for the round is not allowed to put down any new trios or escaleras on subsequent turns. After the initial contract, further cards can only be put down by adding to existing trios and escaleras. He may add as many such cards as he wishes on his turn, but is not forced to play cards just because they fit. Remember, in each turn he still must begin by drawing one new card from either pile and end his turn by discarding a card.
Once any player has gotten rid of all his cards, the round is ended. Each of the other players must add up the values of all the cards remaining in their hands. Each player's total is his score for that hand, and is added to his previous cumulative score.
Jokers are wild! However, you may only use one Joker per escalera or trio in putting down your initial contract. That is, in round two, you could put down Joker-4-5-6 and Joker-7-7, but, you cannot put down Joker-Joker-5-6 and 7-7-7. In later play (that is after putting down the inital contract), you may put down as many Jokers on a single escalera or trio as you want.
A Joker at the end of an escalera may be changed in value. That is, if the escalera has Joker-4-5-6, you could tuck a 3 between the Joker and the 4, making the Joker take on a value of 2, or you could add a real 2, leaving the joker to represent the 3.
You may not change the value of a Joker that is in the middle of an escalera. That is, if the escalera is 3-Joker-5-6, you cannot tuck a card in; as that joker is not on the end of the escalera, you cannot change its value. Also you cannot move a joker from one end of an escalera to the other; if a player puts down 9-10-J-Joker, you cannot add a 7, counting the Joker as a 8, because the Joker was originally played at the top end of the sequence. It would, however, be legal to add a 8, a Q or a K
Players may agree before the game begins that the jokers will be worth 50 points rather than 25.
Players may agree to value the jacks, queens, kings and aces at ten points each; this makes the count faster.
The game Carioca played in Argentina is similar to Central American Loba. The main difference is that Carioca has seven rounds instead of six. The contract in the seventh round is three escaleras. As you need twelve cards for three escaleras, for that round each player is dealt twelve cards. In this last round the first player to put down must get rid of all their cards.
A Joker included in any place within an escalera may be replaced and moved to another place in the same escalera. For example, in an escalera made up of 2-3-Joker-5, the Joker may be replaced by a 4 and moved to either end.
Another difference is the points assigned to the cards. In Carioca jokers are valued at 50 points, aces are worth 20 and jacks, queens and kings are 10. The rest of the cards are worth their face value in points.
Carioca is also played in Chile. Alonso Tapia tells me of the following two variations played there: