Development of a pregnant guinea pig model to test the virulence of Campylobacter fetus subsp. venerealis

Bovine genital campylobacteriosis (BGC), caused by Campylobacter fetus subsp. venerealis (Cfv), is associated with production losses in the Australian meat and dairy industry. The objective of this pilot study was to develop a reliable guinea pig model for BGC abortion to facilitate future studies of Cfv pathogenicity, abortion mechanism and vaccine efficacy. Five groups (A-E) of 5 guinea pigs (1 control per group) at 42 days of gestation were inoculated with laboratory isolates of Cfv via intra-peritoneal (IP) injection. Groups A, B, C, D and E were injected with five different isolates; Q41 at 8.4 x 107 cfu/ml, 258 at 1 x 108 cfu/ml, 540 at 1 x 108 cfu/ml, 540 at 1.2 x 104 cfu/ml and 540 at 3.3 x 107 cfu/ml respectively. Tissues from dams and aborted foetuses were examined using culture and histology. The study was approved by the University of Queensland Animal Ethics Committee. Group B had an abortion rate of 100% and groups C and E had abortion rates of 75% within a time period of 19 – 168 hours while Group A produced no abortions within 7 days of IP injection. The occurrence of Cfv isolated from peritoneum, uterus horns, placental sites, amniotic fluid and foetal stomach content varied. One dam in Group D aborted one foetus. No control animals aborted and Cfv was not isolated in Group D and the controls. Histology results showed tissue changes associated with placentitis, suggesting that Cfv induces inflammation, placental detachment and abortion. Strain virulence variation appears to be present. Intra-peritoneal administration of Cfv to pregnant guinea pigs is a promising small animal model for investigation of BGC abortion