There's a nice description of the multi-volume publication by Cambridge University Library, Rare Books, http://www.lib.cam.ac.uk/deptserv/rarebooks/gesner.html, with references for further reading.
So the question is, when did the guinea pig first make appearances in books, fact or fiction, for children?
It's fascinating tracing the appearances of guinea pigs in nineteenth century story books in the United Kingdom and the United States.
I've collected a couple of miniature, instructive books, about beasts (1844) and pets (late 1860s), which include a page or so on the guinea pig with an accompanying picture.
Thomas Nelson published in Edinburgh, 1844, Stories of Natural History : Beasts, and included on pages 107-111, The Guinea pig. (Note: Page 10 is blank)
In the mid to late 1860s, Leavitt & Allen, New York published The Boy and his pony, and Other Stories, and included on page 4, The Guinea pig.
The earliest fiction story (c.1840s) I know about to-date, which features a guinea pig, is Chapter IV, The Guinea-pig, from:
Mamma's stories | about | the old dolls ; distinctions ; | the half-crown ; guinea-pig ; mother's return ; | new doll ; cautions ; transgression and penitence ; | nursing ; the visit ; children's wishes ; |conclusion. | Embellished with plates. | London : | T.H. Munday. | 9, Fore Street, Cripplegate. Printed by J. May, Cannon Street, Dover.
A contemporary inscription on the front free endpaper includes a date for 1843.
