Brucellosis, a zoonotic bacterial infection caused by various Brucella species, affects a wide range of animals, including dogs (canines), cattle (bovines), and sheep (ovines). This disease is characterized by reproductive problems like abortions and infertility, posing a significant public health risk due to its potential to spread from animals to humans.
Causative Agent
- Canine Brucellosis: Primarily caused by Brucella canis.
- Bovine Brucellosis: Mainly caused by Brucella abortus.
- Ovine Brucellosis: Primarily caused by Brucella melitensis, with Brucella ovis playing a less common role.
How Does it Spread?
Brucella spp. are facultative intracellular pathogens, meaning they can survive both inside and outside host cells. They invade host cells, particularly macrophages (immune cells), and replicate within them. These bacteria cleverly evade the immune system by preventing the fusion of compartments that would normally destroy them.
Transmission Routes
- Canines: Direct contact with infected animals, contaminated environments, ingestion of contaminated materials, venereal transmission, or artificial insemination.
- Bovines: Typically through ingestion of contaminated feed, water, or fetal membranes. Infected materials can also spread the bacteria via mucous membranes or skin abrasions.
- Ovines: Similar to bovines, transmission occurs through ingestion of contaminated materials and close contact with infected animals, especially during lambing or abortions.
Clinical Signs
- Canines:
- Late-gestation abortions
- Infertility in both males and females
- Inflammation of the testicles and epididymis (males)
- Diskospondylitis (inflammation of the intervertebral discs), causing spinal pain and neurological signs
- Bovines:
- Late-term abortions
- Retained placenta (afterbirth)
- Birth of weak calves
- Inflammation of the testicles and epididymis (males)
- Hygromas (fluid-filled sacs) on the knee joints
- Ovines:
- Abortions, typically in the last trimester
- Birth of weak or stillborn lambs
- Inflammation of the testicles and epididymis (males), primarily due to B. ovis infection
- Mastitis (inflammation of the mammary gland) and arthritis (joint inflammation) in some cases
Diagnosis
Diagnosis involves a combination of clinical signs, blood tests, and isolating the bacteria.
Blood Tests:
- Rose Bengal Test: A rapid screening test.
- Complement Fixation Test (CFT): Confirms the presence of brucellosis.
- ELISA (Enzyme-Linked Immunosorbent Assay): Used for confirmation and to track the spread of the disease.
- PCR (Polymerase Chain Reaction): A rapid and specific method for identifying Brucella spp.
Bacterial Isolation:
Blood cultures or tissues from aborted fetuses can be used to isolate the bacteria. Culturing on special media followed by biochemical testing confirms the presence of Brucella spp.
Treatment
Treating brucellosis in animals is challenging due to the bacteria's location within cells and the tendency for chronic infection. The main approach includes:
- Antibiotic Therapy: Combinations of tetracyclines (e.g., doxycycline) and aminoglycosides (e.g., streptomycin) are often used. Extended treatment is necessary to prevent relapses.
- Supportive Care: Managing reproductive problems and complications arising from the disease.
- Isolation: Infected animals must be isolated to prevent spreading the disease.
Control and Prevention
Effective control and prevention strategies include:
- Vaccination:
- Bovines: RB51 vaccine for cattle.
- Ovines: Rev-1 vaccine for sheep.
- Canines: No effective vaccine is currently available.
- Hygiene and Sanitation:
- Proper disposal of aborted materials and carcasses.
- Regular disinfection of premises.
- Use of personal protective equipment (PPE) by handlers.
- Biosecurity Measures:
- Quarantine and testing of new animals before introducing them to the herd/flock.
- Regular testing and surveillance programs.
- Control of animal movement and transport.
- Public Health Measures:
- Education and awareness programs for farmers, veterinarians, and the public.
- Prompt reporting of cases to veterinary and public health authorities.
Brucellosis remains a significant disease in canines, bovines, and ovines, impacting animal health and the economy. Diagnosis relies on a combination of tests