BRUCELLOSIS IN DOGS
Canine brucellosis is an important zoonotic disease caused mainly by Brucella canis and occasionally by B. abortus, B. melitensis and B. suis. Brucella spp. are facultative intracellular pathogens, Gram-negative coccobacillus or short rod, oxidase, catalase, and urease positive. Brucella canis was first described in USA in 1966 where mass abortion in beagles breed of dogs was reported. In India, B. canis infection was reported for the first time in 1991. Clinical manifestations of brucellosis in dogs include epididymitis, testicular atrophy and sterility in male dogs, while the major symptom in females is abortion. Although dogs that have been spayed or neutered do not have reproductive signs, they occasionally develop other conditions such as ocular disease and discospondylitis. Transmission to humans especially pet owners may be through contact with the semen, urine, and/or aborted fetuses of infected animals. Brucellosis is a highly contagious bacterial disease that affects all dogs regardless of age or breed, although dogs who haven’t been spayed or neutered and are used for breeding are most at risk. It can also be passed on to humans.
Brucellosis causes, amongst other things, infections in the uterus of female dogs, and an infection in the testicles in male dogs, called epididymitis.
Transmission
- canis can be demonstrated in the aborted fetus, placenta, fetal fluids, milk, urine and semen of infected animals. The organism can persist in vaginal discharges for several weeks after an abortion and is shed in normal vaginal secretions, particularly during estrus. High concentrations of B. canis may be found in semen for weeks or months after infection and intermittent shedding of smaller quantities can occur for years. B. canis may also be excreted in saliva, nasal and ocular secretions and feces. In dogs, B. canis primarily enters the body by ingestion, through genital, oronasal and conjunctival mucosa or by contact with the aborted fetus and fetal membranes. Transmission through broken skin and through aerosols may also be possible. Most cases are thought to be acquired by venereal transmission. Chronically infected dogs can shed this organism despite being seronegative and blood culture negative. Puppies can be infected in utero, and may remain persistently infected even though they may appear normal. Blood transfusions and contaminated syringes are the other potential sources of infection.
How is brucellosis spread in dogs?
Canine brucellosis is spread through breeding and from contact with infected fluids. These fluids could be semen, vaginal discharge, birthing fluids and urine. The most common way a dog can pick up the infection is by licking urine or other bodily fluids, sniffing infected fluids, or mating with an infected dog. Other less common ways of spreading the disease are saliva, poop, milk and blood. Because canine brucellosis is easily spread, dogs who live closely together, such as in kennels and doggy daycare, have the highest risk of being infected.
Disease in animals:
- canis is only known to be important in dogs. B. canis can cause abortions and stillbirths in pregnant dogs. Most abortions occur late, particularly during the seventh to the ninth week of gestation. Abortions are usually followed by a mucoid, serosanguinous or grey-green vaginal discharge that persists for several weeks. Early embryonic deaths and resorption have been reported a few weeks after mating, and may be mistaken for failure to conceive. Sometimes live but weak pups are born which often die soon after birth. Other congenitally infected pups can be born normal and later develop brucellosis. Clinical signs occur during subsequent pregnancies in some dogs, but not in others. In males, epididymitis and scrotal edema are common in the acute stage. Other symptoms include unilateral or bilateral testicular atrophy in chronic infections, infertility in some males, orchitis and scrotal dermatitis self-trauma by licking. Other symptoms that are occasionally reported include lethargy or fatigue, exercise intolerance, decreased appetite, weight loss and behavioural abnormalities (loss of alertness, poor performance of tasks). However, most affected dogs do not appear seriously ill. Fever is rare and many infected dogs remain asymptomatic. Dogs with brucellosis may recover spontaneously, beginning a year after infection, but recovery is more common after two to three years, and some dogs remain chronically infected for years. Deaths are rare except in the foetus or newborn.
Disease in Humans:
Little information is available regarding the incubation period for brucellosis caused by B. canis in humans. The symptoms caused by other Brucella spp. usually appear within 2 weeks of exposure, but some cases have developed as late as 3 months. The virulence of B. canis for humans has been considered to be low, as few cases have been documented and most have been mild. Hence infections may go under reported and specific diagnostic tests are rarely performed for diagnosis of the disease. The expected clinical signs are based mainly on the syndromes caused by other species of Brucella. Some people infected with Brucella spp. remain asymptomatic. In symptomatic cases, brucellosis begins as an acute febrile illness with nonspecific flu-like signs such as fever, chills, headache, malaise, back pain, myalgia and generalized aches. Drenching sweats can occur, particularly at night. Some patients may also have lymphadenopathy, splenomegaly or hepatomegaly. Some patients with brucellosis recover spontaneously, while others develop persistent symptoms including fever, weakness and other nonspecific signs. Arthritis, spondylitis, chronic fatigue and epididymo-orchitis can be seen. Neurologic signs (including personality changes, meningitis, uveitis and optic neuritis), anemia, internal abscesses, nephritis, vasculitis, endocarditis and dermatitis have been reported with some species of Brucella. The mortality rate for brucellosis is low and can vary from less than 2% to 5%.
Diagnosis
Diagnosis in dogs can be made on the basis of reproductive conditions; however, some infected dogs are asymptomatic or have only nonspecific signs. Canine brucellosis is sometimes difficult to diagnose, hence, multiple techniques (e.g. culture, PCR and serology) are often used in combination. The rapid slide agglutination test (RSAT) and the tube agglutination test (TAT) are often used to detect antibodies to B. canis in dogs. Other serological like AGID, ELISA, an indirect fluorescent antibody test, complement fixation, a lateral flow immune-chromatographic assay and counter-immunoelectrophoresis can also be carried out. Definitive diagnosis can be achieved by isolation of B. canis from an animal. For isolation of the organism, samples from the genital tract (e.g., semen, vaginal discharges, placenta) are often more useful than blood, especially in animals with reproductive signs. B. canis may also be detected in milk, urine and aborted fetuses (gastric contents, liver, spleen), as well as in tissues such as the lymph nodes, spleen, prostate, epididymis, testis, uterus, liver and bone marrow, and clinically affected vertebrae or eyes. Molecular methods like conventional and Real time PCR can also be used for diagnosis.
Treatment, Prevention and Control:
No treatment is certain to eliminate B. canis. Even when this organism seems to have disappeared, it may persist in tissues such as lymph nodes, spleen, uterus and prostate. Relapse of the disease is possible, especially when an animal is stressed. Since canine brucellosis is usually introduced into a kennel by an infected dog or semen so dogs from infected kennels should not be sold or used for breeding. Newly purchase animals should be quarantined and tested before introduction. It has also been recommended that dogs be tested before allowing them to breed. In infected kennels, brucellosis can be controlled by sanitation and infection, housing the animals in individual cages and by isolation or removal of infected dogs. Neutering can be used as an additional control measure in treated animals, if they are intact. There is no vaccine for B. canis.
Compiled & Shared by- Team, LITD (Livestock Institute of Training & Development)
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