Abstract
Brucellosis in swine is caused by Brucella suis, a bacterial infection of nearly worldwide distribution. Brucella suis is also transmissible to humans, dogs and cattle and is considered a reemerging disease of public health concern. To date, there is no effective vaccine for swine. This prompted us to investigate the potential use of the commercially available vaccine for cattle or the live attenuated vaccine candidate S19ΔvjbR. As the first step, we sought to study the safety of the vaccine candidates when administered in pregnant sows, since one of the major drawbacks associated with vaccination using Live Attenuated Vaccines (LAV) is the induction of abortions when administered in pregnant animals. Fifteen pregnant gilts at mid-gestation were divided into four groups and subsequently vaccinated subcutaneously using different formulations containing 2.0 ± 0.508 × 109 CFU of either S19 or S19ΔvjbR. Vaccination in pregnant animals with the vaccine candidates did not induce abortion, stillbirths or a reduction in litter size. Multiple tissues in the gilts and piglets were examined at the time of delivery to assess bacterial colonization and histopathological changes. There was no evidence of vaccine persistence in the gilts or bacterial colonization in the fetuses. Altogether, these data suggest that both vaccine candidates are safe for use in pregnant swine. Analysis of the humoral responses, specifically anti-Brucella IgG levels measured in serum, demonstrated a robust response induced by either vaccine, but of shorter duration (4–6 weeks post-inoculation) compared to that observed in cattle or experimentally infected mice. Such a transient humoral response may prove to be beneficial in cases where the vaccine is used in eradication campaigns and in the differentiation of vaccinated from infected animals. This study provides evidence to support future efficacy studies of both vaccine candidates in swine.
Highlights
Brucellosis is a zoonosis caused by Brucella spp. of nearly worldwide distribution
Among the 12 identified species classified based on preferential host specificity, 3 are highly pathogenic for their preferred host species [Brucella melitensis, Brucella abortus and Brucella suis], as well as humans, and are all associated with significant economic losses in different parts of the world [1]
One of the main drawbacks associated with vaccination using Live Attenuated Vaccine candidates (LAV) is the induction of abortion in pregnant animals [10,11]
Summary
Among the 12 identified species classified based on preferential host specificity, 3 are highly pathogenic for their preferred host species [Brucella melitensis (sheep and goat), Brucella abortus (cattle) and Brucella suis (swine)], as well as humans, and are all associated with significant economic losses in different parts of the world [1]. Brucellosis in humans is acquired by direct contact with infected animal tissues or consumption of unpasteurized milk products. It is considered a debilitating disease with undulant fever as a major symptom, frequently accompanied by fatigue, sweats,. Infection usually leads to major economic losses, with a significant negative impact [1]
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