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Infectious disease(brucella)
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- 2. Brucellosis o Brucellosis isa 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. Definition:-
- 3. Brucellosis tends tobe an occupational disease, with farmers, animal handlers, abattoir workers, veterinarians, and laboratory personnel at greatest risk. In humans, disease is mainly caused by B melitensis, B abortus, B suis, and occasionally by B canis. B melitensis has been associated with more aggressive and acute presentations, and worldwide is the most common species to infect humans. B abortus is usually associated with mild to moderate disease, and rarely causes complications outside the musculoskeletal system. B suis has been associated with focal abscesses.
- 4. Epidemiology Brucellosis occurs worldwide;major endemic areas include countries of the Mediterranean basin, Arabian Gulf, the Indian subcontinent, and parts of Mexico, Central and South America Human Infection. melitensis is the species that infects humans most frequently. The incubation period ranges from a few days to a few months. The disease is manifested as fever accompanied by a wide array of other symptoms.
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- 6. Pathogenesis o Ingestion: • Rawmilk & 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.
- 7. Pathogenesis o Animal tissuesand 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.
- 8. Pathogenesis o Intracellular parasitism:brucellae have a particular tendency to persist intracellularly, notably in the reticuloendothelial system.
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- 10. Clinical features o Incubationperiod: 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
- 11. Clinical features o Nonspecific symptoms: sweating, anorexia, constipation, rigor and weakness. o Depression. o Osteoarticular complications e.g. arthritis, osteomyelitis.
- 12. Clinical features o Splenomegaly,lymphadenopathy and hepatomegaly. o Orchitis and epididymitis. o A septicemic disease, abortion can occur.
- 13. Clinical features o Classification:Acute (< 1 year) and Chronic (>1 year). o Low case fatality rate mostly due to infective endocarditis.
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- 15. Diagnosis 1- Clinical features. 2-Serology: brucella agglutinins in the blood. 3- Blood or tissue culture. 4- Polymerase Chain Reaction (PCR).
- 16. Diagnosis in Humans oSerology: 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.
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- 18. Diagnosis in Humans oFalse positive: cross reactivity with antibodies of F. tularensis,, E. coli and V. cholerae. o False negative: in prozone phenomenon.
- 19. Diagnosis in Humans oProzone 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.
- 20. 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
- 21. Diagnosis in Humans oCulture 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.
- 22. o PCR isa rapid and accurate method for diagnosis of Brucella species. o CBC: Non specific, (leucopenia, lymphocytosis, anemia). Moderate elevation of ESR. Diagnosis in Humans
- 23. Treatment, Prognosis and Prevention& Control
- 24. Treatment of Choice oCombination 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.
- 25. Prognosis o This diseaseis easily curable with a low risk of relapse or chronicity. o About 5% of treated cases relapse • Failure to complete the treatment regimen
- 26. Prevention and Control oEducation 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.
- 27. Prevention and Control oImmunize 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.