Brucellosis is a disease of the reproductive tract which may cause abortion in females, infection of the sexual organs in males, and infertility in both sexes. The causative agent of canine brucellosis is the bacteria, Brucella canis. Transmission between dogs occurs via mucous membranes, so the bacteria may enter the body through the nose, mouth, conjunctiva of the eye, and vagina and spreads from there to lymph nodes and the spleen. The majority of bacteria in infected dogs are secreted in semen and vaginal secretions, but bacteria may be present in milk, urine and saliva as well. Thus any bodily fluids can infect other dogs. There are also reports of sporadic brucellosis in dogs caused by B. abortus, B. suis and B. melitensis occur in dogs. They acquire infections primarily by eating contaminated material especially fetus, after birth and milk. It occurs most frequently in breeding kennels, though family pets may also become infected.
Canine Brucellosis is a very serious disease as the infected animal becomes unbreedable causing serious economic losses to canine breeders and it also act as carrier of infection. Additionally it poses a significant public health hazard since it is transmissible to humans especially those handling aborted fetuses. Humans may develop a serious liver impairment or arthritis.
Clinical conditions in Dogs
In bitches it causes abortion of litters, usually between 45-55 days after breeding, litters with some pups born dead or dying immediately after birth, and pups that die at the embryo stage and are reabsorbed. In some cases there may be decreased fertility rather than abortion. This may be due to resorption of fetuses early in their development
In male dogs inflammation of the epididymis, prostate and/or testicles (often leading to testicular atrophy), infertility because of abnormal sperm and poor sperm motility, and reluctance to breed due to pain caused by inflammation of the sex organs. The infertility due to infection of the testicles occurs as a result of anti-sperm antibodies developed as the body attempts to fight off the bacterial infection. Scrotal enlargement or infection of the skin over the scrotum may also be seen.
In both female and male dogs there may be infection of spinal discs (diskospondylitis) which can cause back pain and rear leg weakness or even paralysis. Eye inflammation may be seen in either sex . Some dogs may show non-specific signs of poor health, such as poor vigor. In rare cases the disease has caused damage to the kidneys and nervous system.
Infection in Dogs
The transmission of B. Canis occurs as a result of contact with vaginal secretions, fetuses and fetal membranes. Infected male may transmit the infection to bitches during coitus. The milk of infected bitches is another source of infection. Human cases on contact with bitches that had recently aborted had transmitted infection to humans.
There is no reliable treatment for Brucellosis. Brucella canis lives inside of the dog’s cells so it is difficult to reach the bacteria with antibiotics. Any attempt at treatment would require the use of multiple types of antibiotics. Various antibiotics such as doxycycline, minocycline and dihydrostreptomycin have been partially effective at causing a temporary reduction in the bacterial organisms after several weeks of treatment. A complete cure is unlikely. It is recommended that infected animals be castrated or spayed. All infected animals should be considered to be lifelong carriers of the disease, even if treated.
- Isolation of etiological agent from blood, vaginal discharge, milk and semen from fetal tissue and placenta.
- Plate agglutination and Standard tube agglutination test using B. canis antigen.
- AGID with antigen extracted from the cell wall of B. canis.
- A new test has been developed that uses a non mucoid M- variant of B. canis as the antigen in Tube agglutination after treating the sera with 2- mercapto ethanol.
- Zoha and Carmichael (1982) showed that immunodiffusion test using sonicated antigens and can detect infected animal for up to 6 months.
Prevention and Control
1.Kennels with active stud dogs should never breed a male to an untested female. All individuals used for breeding should be routinely tested prior to breeding.
- When possible, all incoming breeding dogs should be isolated for two weeks upon arrival at the kennel. At the end of two weeks, have the individual (male or female) tested by your veterinarian for brucellosis.
- All positive males and females should not be bred. Surgical spaying or neutering of these individuals is recommended. Various blood tests are available to screen breeding dogs (male and female) and identify those who are infected (carriers).
- Artificial Insemination (AI) can lessen the risk of Brucella transfer at breeding. While rare, transmission of Brucella canis to a bitch can occur during AI, especially if infected semen is used. However, AI will protect an infected female from transferring it to a noninfected male. Brucellosis infected bitches should not be bred, even with artificial insemination, due to the risk of contamination from vaginal discharge, milk, and puppies.
- If infection is suspected at any time, quaternary ammonium (like Roccal Rx) and iodophor (Betadine Rx) disinfectants can kill Brucella organisms in the kennel to limit spread of the disease.
- Brucellosis caused by B. canis in dog kennels can be controlled by repeated serological tests. No vaccination is available.
Human health hazards
People can become infected with Brucella canis. People should avoid contact with dead fetuses or the discharge from aborting dogs. Transmission has also occurred from contact with secretions from male dogs.
- Pedro N. Acha and Borris Szyfres. Zoonosis and communicable diseases common to man and animals. WHO Geneva. AITS publishers, INDIA; 2006
- Quinn, P.J., Carter, M.E., Markey, B.K. and Carter, G.R. Clinical Veterinary Microbiology. Wolfe publications, USA; 1999
- Zoha, S.J. and Carmichael, L.E. Seroogical response of dogs to cell wall and internal antigens of B.canis. Veterinary Microbiology;1982