The emergence of Brucella canis as a public health threat in Europe: what we know and what we need to learn

Abstract

The zoonotic bacteria, Brucella canis, is becoming the leading cause of canine brucellosis in Europe. In dogs, it causes reproductive problems as well as non-specific lameness or discospondilitis. In humans, B. canis can be origin of chronic debilitating conditions characteristic to its genus such as undulant fever, splenomegaly, and lymphadenopathy. Although B. canis shows some pathogenic characteristics similar to B. abortus and B. melitensis, it lacks surface O-polysaccharide, like nonzoonotic B. ovis. This review shows that host-B. canis interactions are still poorly understood, with many knowledge and capability gaps, causing relatively poor sensitivity and specificity of existing diagnostic tools. Currently, there is no vaccine for this rough Brucella species. Besides, antimicrobial therapy does not guarantee bacterial elimination, and infection relapses are frequently reported, increasing the risks of antibiotic resistance development. B. canis has been detected in dogs in almost all European countries which increased human exposure, but currently there is no systematic surveillance. Moreover, B. canis caused brucellosis is not included in Animal Health Law, and therefore there is no legal framework to tackle this emerging infectious disease. To map out the diagnostic strategies, identify risks for human infections and propose management scheme for infected pet and kennel dogs, we present current understanding of canine B. canis caused brucellosis, outline major knowledge gaps and propose future steps. To address and highlight challenges veterinary and public health services encounter in Europe, we developed two B. canis infection scenarios: of a single household pet and of a kennel dog in larger group.

Keywords: Brucella canis emergence; Brucellosis; Europe; diagnostics; outbreak management protocols; public health risks; therapy; transmission.

Figure 1.

Currently known B. canis transmission routes for human infections. It has been proven that humans can be infected by B. canis through direct contact with bodily discharges of infected dogs, their bodily discharges or through accidental laboratory exposure. Other possible sources of infection could be contact with wild canids. In the same time, the survival of B. canis in the environment has not been tested (although it has been shown that other members of the Brucella genus can survive in the environment for up to eight months under favourable conditions), and this cannot be excluded as possible source for human infection. Proven sources of human infection are linked by full line arrows, while possible sources are presented by dotted line arrows.

Figure 2.

Overview of the diagnostic management scheme evaluated in this study for B. canis infection in individual dog and/or kennel. In the case of a confirmed B. canis infection in individual dog or kennel, the following workflow aims to provide proper bio-risk and public health management. After all biosecurity measures have been put in place to avoid the spread of infection, a detailed epidemiological investigation must be carried out to identify exposed persons, animals or facilities with which need to be surveyed.