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Brucella and brucellosis


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Brucella and brucellosis

  1. 1. Brucellosis Muayad Aghali Merza Infectious Diseases Specialist School of Medicine 26st November 2014
  2. 2. Objectives Students should be able to: • Define brucellosis. • Describe the causative organism. • Describe pathogenesis and clinical features of the disease. • Mention diagnostic methods of brucellosis. • State treatment of brucellosis. • Describe prevention and control of the disease.
  3. 3. Definition
  4. 4. Brucellosis o Brucellosis is a zoonosis primarily of domestic animals, causing a chronic debilitating septicemic disease leading to abortion. o The disease is prevalent worldwide and is particularly common in the Mediterranean and Middle Eastern countries, and in parts of Africa and South America.
  5. 5. Other Names of Human Brucellosis o Malta Fever, Undulant Fever, Mediterranean Fever, Gastric Fever. o The causal Brucella species are named after Sir David Bruce, who discovered the cause of one form of the disease while serving in Malta in 1887.
  6. 6. The Organism
  7. 7. Brucella spp. o Gram negative, intracellular coccobacilli bacteria. o Non-motile, non-capsulated, non-spore forming.
  8. 8. Brucella spp. o Environmental persistence. • Temperature, pH, humidity. • Frozen and aborted materials. o Multiple species.
  9. 9. Species Main animal host Human Pathogen Pathoge- nicity B. abortus cattle yes Moderate B. melitensis goats, sheep yes Highest B. suis pigs yes High B. canis dogs yes Moderate Main Causative Species of Human Brucellosis
  10. 10. Antigenic Structure and Classification o A and M antigens are common to 3 mains Brucella spp. o B. melitensis has the highest concentration of M antigen and causes the most serious infections. o The difference between species is related to the amount of the two main antigen:
  11. 11. • B. abortus : A:M=20:1 • B. melitensis: A:M=1:20 • B. suis : A:M=2:1 Antigenic Structure and Classification AA MM AA MM MMAA
  12. 12. Pathogenesis
  13. 13. Pathogenesis o Ingestion: • Raw milk & unpasteurized dairy products. • Rarely through undercooked meat. o Inhalation: o Inoculation: o Person-to-person transmission is very rare. of placental or uterine discharges, blood and urine.
  14. 14. Pathogenesis o Animal tissues and products, such as placenta, uterus and milk, that are rich in erythritol (a growth factor for brucellae) can be heavily contaminated and highly infectious. o Spread in the body occurs via lymphatics, replication within lymph nodes, and then wide hematogenous spread to organs and tissues.
  15. 15. Pathogenesis o Intracellular parasitism: brucellae have a particular tendency to persist intracellularly, notably in the reticuloendothelial system.
  16. 16. Who is at Risk? o Occupational Disease: • Cattle ranchers/dairy farmers. • Veterinarians. • Abattoir workers. • Meat inspectors. • Lab workers. o Hunters. o Travelers. o Consumers of unpasteurized dairy products.
  17. 17. Clinical features
  18. 18. Clinical features o Incubation period: 1-3 weeks, occasionally several months. o Can affect any organ or organ system. o Fever may be intermittent or undulant. Fever, often persists for months or years. Undulant fever 39.5 37.0
  19. 19. Clinical features o Non specific symptoms: sweating, anorexia, constipation, rigor and weakness. o Depression. o Osteoarticular complications e.g. arthritis, osteomyelitis.
  20. 20. Clinical features o Splenomegaly, lymphadenopathy and hepatomegaly. o Orchitis and epididymitis. o A septicemic disease, abortion can occur.
  21. 21. Clinical features o Classification: Acute (< 1 year) and Chronic (>1 year). o Low case fatality rate mostly due to infective endocarditis.
  22. 22. Diagnosis
  23. 23. Diagnosis 1- Clinical features. 2- Serology: brucella agglutinins in the blood. 3- Blood or tissue culture. 4- Polymerase Chain Reaction (PCR).
  24. 24. Diagnosis in Humans o Serology: brucella agglutination test. • Four-fold or greater rise in titer. • Samples 2 weeks apart. o BAT detects antibody to B. abortus, B. melitensis and B. suis but NOT to B. canis. o Therefore, specific serologic tests for B. Canis must be requested. o Rose Bengal Test is useful for screening.
  25. 25. Positive agglutination Negative agglutination
  26. 26. Diagnosis in Humans o False positive: cross reactivity with antibodies of F. tularensis,, E. coli and V. cholerae. o False negative: in prozone phenomenon.
  27. 27. Diagnosis in Humans o Prozone phenomenon may occur secondarily to hyperantigenemia, which might result in a false-negative results. o High levels of antigen may prevent the formation of antigen-antibody complexes. o To solve this problem, routine dilution of the serum beyond 1:320 would help to prevent such a problem.
  28. 28. o 2-ME-test (mercaptoethanol): more specific, positive in chronic Brucellosis. o ELISA test: • High IgM in acute infection. • High IgG in chronic infection. Diagnosis in Humans
  29. 29. Diagnosis in Humans o Culture of blood, bone marrow and tissue fluids. • Blood culture: +ve in about 50 -70% of cases. • Bone marrow culture is the standard criterion, since the reticuloendothelial system holds a high concentration of the organism. Sensitivity 80-90%. • Blood or bone cultures should be incubated for at least 6 weeks.
  30. 30. o PCR is a rapid and accurate method for diagnosis of Brucella species. o CBC: Non specific, (leucopenia, lymphocytosis, anemia). Moderate elevation of ESR. Diagnosis in Humans
  31. 31. Treatment, Prognosis and Prevention & Control
  32. 32. Treatment of Choice o Combination therapy has the best efficacy. • Doxycycline for six weeks in combination with streptomycin for 2-3 weeks or rifampicin for 6 weeks. o CNS cases treat 6-9 months. • Same for endocarditis cases plus surgical replacement of valves.
  33. 33. Prognosis o This disease is easily curable with a low risk of relapse or chronicity. o About 5% of treated cases relapse • Failure to complete the treatment regimen
  34. 34. Prevention and Control o Education about risk of transmission. • Farmer, veterinarian, abattoir worker, butcher, etc. o Wear proper attire if dealing with infected animals/tissues. • Gloves, masks, goggles. o Avoid consumption of raw dairy products.
  35. 35. Prevention and Control o Immunize animals in areas of high prevalence. • Effective attenuated live bacterial vaccines exist against B. abortus (strain 19) and B. melitesis (Rev-I), but as yet none exists for B. suis or B. canis. o No human vaccine.
  36. 36. Questions?