This is all I have, right now.
http://www.raising-rabbits.com/rabbit-syphilis.html
http://www.scribd.com/doc/72228408/Rabbit-Diseases
"Rabbit Syphilis, Vent disease
Diagnosis is confirmed by Darkfieldexaminationof scrapings from the lesions for the presence of the spirochete Treponemaparaluis-cuniculiTreatment Treponematosiscan be treatedsuccessfully with three injections of Benzathinepenicillin with procaine penicillin G, 84,000IU/kg given IM at 7-day intervals.All animals from an infected colony must betreated to eradicate the diseaseThere are NO public health hazards associatedwith the disease.
"
__________ Sun Sep 16, 2012 1:21 pm __________
from the 1st link
"Transmission of vent disease in the vast majority of cases is through breeding. However it is possible to contract the disease through normal contact."
"In a few rabbits with vent disease, the still-infectious rabbit becomes asymptomatic. The outward lesions heal, yet the spirochete is still lurking in the bloodstream. If you breed a rabbit and the other animal comes down with rabbit syphilis, treat both animals."
"Kits and Rabbit Syphilis:
Do not breed infected rabbits. Besides the danger of spreading this infection throughout the herd, the kits themselves become infected by the infected does at kindling.
It is very dangerous to treat infected bunnies with penicillin - the bacterial balance in their intestines is still tenuous; a dose of antibiotics could very easily trigger a fatal diarrhea. If at all possible, it is safest to postpone treatment of youngsters until much closer to adulthood."
Is there anyway they could have been bit, while on pasture or an urine burn?