Brucella canis: A Canine and Human Health Concern

Brucella canis is a type of bacteria that can cause serious health problems in dogs and even humans.

This zoonotic pathogen is primarily found in dogs, particularly those that are in close contact with other canines.

Brucella canis was first identified in 1954, and since then, it has been recognized as a significant public health concern.

The bacteria can be transmitted through direct contact with infected dogs, their saliva, or their birth products.

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Brucella canis is a bacterium that affects dogs, causing a range of symptoms from mild to severe.

It's primarily spread through contact with infected dogs' saliva, urine, or feces.

Brucella canis is a zoonotic organism, which means it can be transmitted from animals to humans. B. canis is oxidase, catalase, and urease positive and non-motile.

To identify B. canis, serology and PCR are used. Unlike Haemophilus, B. canis does not require added X (hemin) and V (nicotinamide adenine dinucleotide) factors in cultures.

B. canis colonies can be seen after 48 hours and have a convex shape, typically circular in shape. They are usually 0.5-1.0 mm in diameter. Mucoid variants like B. canis have a sticky, glue-like texture and can be white, yellowish white, or even brown in color.

Key Identification Characteristics:

B. canis is a zoonotic organism, meaning it can be transmitted from animals to humans. It's oxidase, catalase, and urease positive, and non-motile.

B. canis resembles Haemophilus in many ways, but it doesn't require added X (hemin) and V (nicotinamide adenine dinucleotide) factors in cultures.

B. canis is not acid-fast, but it retains its color when exposed to weak acids, resulting in a distinctive red color when stained with Macchiavello's stain.

B. canis is always found in a non-smooth or mucoid form, which has highly hydrophobic LPS embedded in its outer membrane.

This unique characteristic makes B. canis soluble in phenol-hexane-chlorophorm, unlike smooth forms of Brucella which are soluble in phenol-water.

Colonies of B. canis can start to appear after 48 hours, and they tend to be 0.5-1.0 mm in diameter with a convex shape and circular appearance.

Mucoid variants of B. canis have a sticky, glue-like texture and can display a range of colors, including white, yellowish white, and brown.

Here are some key characteristics of B. canis colonies:

Brucella canis is primarily found in domestic dogs. In fact, the host range of this bacterium is mainly domestic dogs.

Evidence of infections in wild canines has also been reported, specifically in foxes and coyotes. This suggests that the bacterium can infect a range of canine hosts beyond just domestic dogs.

It's worth noting that B. canis is a zoonotic organism, meaning it can be transmitted to humans. While rare, human infections can occur, especially in individuals who are immunocompromised or work closely with the bacteria, such as dog breeders and laboratory workers.

The disease caused by Brucella canis is characterized by epididymitis and orchitis in male dogs, and endometritis, placentitis, and abortions in females.

In males, Brucella canis infection can lead to infertility due to the development of an antibody against spermatozoa, which may be followed by inflammation of the testes.

Brucella canis infection can also cause diskospondylitis, an infection of the spinal plates or vertebrae, which is often spotted in the animal's reproductive organs.

Brucella canis are non-motile bacteria, meaning they can't move on their own and need assistance to move. This is because they lack flagella.

Brucella canis have a unique shape, described as coccobacilli, or short rods with slightly rounded ends and slightly outward curving sides.

They are also non-encapsulated and non-spore forming bacteria that replicate in the endoplasmic reticulum (ER) of their host cells.

Brucella canis are Gram-negative bacteria that thrive in a specific temperature range, between 20 °C and 40 °C, with an optimal growth temperature of 37 °C.

Their growth is also pH-dependent, with an optimal range of pH 6.6 to 7.4, making them neutrophilic in nature.

Brucella canis form non-hemolytic, non-pigmented convex colonies on blood agar culture media.

Their outer cell membrane is composed of a unique mix of fatty acids, including myristic, palmitic, and stearic acids in large quantities.

Cis-vaccenic and arachidonic acids are found in medium amounts, while C17 and C19 cyclopropane fatty acids are present in very limited amounts.

The absence of hydroxy fatty acids in their outer cell membrane contributes to their hydrophobic interactions and greater cell stability.

The lipids in the phospholipid portion of B. canis are mainly cis-vaccenic cyclopropane, with small amounts of lactobaccilic acid.

This composition differs from other Brucella species, which typically have lactobaccilic acid as the main component.

B. canis has two distinct circular chromosomes that contain shared portions due to horizontal gene transfer.

The first chromosome is larger than the second, with an average of 2243 genes on chromosome 1 and 1229 on chromosome 2.

Chromosome 2 is much smaller than chromosome 1 and was derived from a plasmid.

Both chromosomes contain essential genes necessary for survival, with these genes split evenly between the two.

B. canis is thought to be a variant of B. suis Biovar 1 based on genomic similarities between the two.

The genomic structure of both B. canis and B. suis Biovar 1 cannot be distinguished from each other, as they both demonstrate similar sizes within the two circular chromosomes present.

B. canis is thought to be a stable R mutant of B. suis Biovar 1.

Brucella canis is a disease that affects dogs, and its pathogenicity is quite unique. The disease is characterized by epididymitis and orchitis in male dogs.

In females, it can cause endometritis, placentitis, and abortions. These symptoms can be devastating for dog owners, especially if they're not aware of the disease.

Infertility is a common issue in both male and female dogs infected with Brucella canis. Males may develop an antibody against their spermatozoa, which can lead to inflammation of the testes.

This inflammation can cause the animal to become sterile. The disease can also cause diskospondylitis, an infection of the spinal plates or vertebrae.

Here's a summary of the symptoms in both genders:

It's worth noting that while Brucella canis is still relatively uncommon, its symptoms can have a significant impact on dog owners.

Brucella canis has a distinct timecourse that's essential to understand when dealing with this bacteria. Organisms shed for 4-6 weeks following abortion in females.

This bacteria can persist in infected males for a much longer period, typically between 7-60 weeks. The prolonged bacteremia of 1-2 years not uncommon in non-genital form of disease is a significant factor to consider.

Pups may be bacteremic for at least 2 months after birth, making them a potential source of human infection and a means of maintaining the bacteria in the canine population.

Here's a breakdown of the timecourse for Brucella canis:

Brucella canis is a significant concern in various parts of the world. The geographic incidence of Brucella canis varies greatly.

One of the areas with a notable increase in incidence is the southernmost states of the USA. This region, along with Mexico, Central and South America, The People's Republic of China, and Japan, have seen a rise in reported cases.

Canada and Europe have also reported sporadic cases.