Comparison of experimental models for Streptococcus suis infection of conventional pigs.
Four different experimental models for Streptococcus suis-induced disease were compared to find a model that closely mimics naturally occurring disease in conventional pigs. Fourteen, 2-week old pigs free of S. suis type 2 were used in 2 experiments. In experiment 1, 3 pigs were inoculated intravenously (IV) and 3 pigs intranasally (IN) with S. suis. Two out of 3 of the IV-inoculated pigs exhibited signs of severe central nervous system disease (CNS) and were euthanized. Streptococcus suis type 2 was isolated from whole blood, joints, and serosal surfaces of both pigs. No clinical signs and no growth of S. suis were detected in the IN-inoculated pigs. In experiment 2, 4 pigs were inoculated IV and another 4 were inoculated IN with the same isolate as in experiment 1. One hour before inoculation the IN-inoculated pigs were given 5 mL of 1% acetic acid intranasally (IN-AA). All the IV-inoculated pigs showed CNS disease and lameness, and 2 of the pigs became severely affected and were euthanized. All the IN-AA inoculated pigs exhibited roughened hair coats and 2 pigs developed severe CNS disease and were euthanized. Streptococcus suis was isolated from the joints and blood of 3 pigs in the IV-inoculated group. Streptococcus suis was isolated from blood of 2 pigs, meninges of 3 pigs, and joints of 1 pig in the IN-AA inoculated group. Natural exposure to S. suis most likely occurs by the intranasal route. The IN-AA model should serve as a good model for S. suis-induced disease, because the natural route of exposure is intranasal and the IN-AA model was effective in inducing disease that mimics what is observed in the field.
Pallarés
Francisco J
FJ
Veterinary Diagnostic Laboratory, Department of Veterinary Microbiology and Preventive Medicine, College of Veterinary Medicine, Iowa State University, Ames, Iowa 50011, USA.
Halbur
Patrick G
PG
Schmitt
Cameron S
CS
Roth
James A
JA
Opriessnig
Tanja
T
Thomas
Peter J
PJ
Kinyon
Joann M
JM
Murphy
Dee
D
Frank
Dagmar E
DE
Hoffman
Lorraine J
LJ
D000281:Administration, Intranasal; D000818:Animals; D001927:Brain Diseases / Q000382:microbiology / Q000473:pathology / Q000662:veterinary*; D004195:Disease Models, Animal; D007275:Injections, Intravenous / Q000662:veterinary; D007794:Lameness, Animal / Q000382:microbiology; D011897:Random Allocation; D013047:Specific Pathogen-Free Organisms; D013290:Streptococcal Infections / Q000382:microbiology / Q000473:pathology / Q000635:transmission / Q000662:veterinary*; D017011:Streptococcus suis / Q000472:pathogenicity*; D013552:Swine; D013553:Swine Diseases / Q000382:microbiology* / Q000473:pathology / Q000635:transmission