Brucellosis

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Brucellosis

• (Malta fever, undulant fever)

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• Definition
• Brucellosis is a bacterial zoonosis transmitted
  directly or indirectly to humans from infected
  animals
• It is caused by the Brucella group of organisms,
  which are small, non motile, Gram-negative rods.
• Its distribution is worldwide apart from the few
  countries where it has been eradicated from the
  animal reservoir.

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• Although Marsten described the disease first in
  1863, it is known after Bruce who described it in
  1886 and discovered B. melitensis. Later on,
  other species were discovered.

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• PATHOLOGY
• Causative agents
• Brucella group of organisms, which are small, non
  motile, Gram-negative rods.
• Species of Brucella group of organisms
• B. abortus is distributed   Worldwide, except for
  Japan and Northern Europe , and its Host are
  Cattle.

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• 2-B. melitensis is distributed in Mediterranean
  region and Middle East , and its Host are Goats,
  sheep, camel.
• 3-B. suis is distributed in Far East, USA and its
  Host are Pigs.
• The organisms usually gain entry into the human
  body via the mouth less frequently they may
  enter via the respiratory tract, genital tract or
  abraded skin.
• The bacilli travel in the lymphatics and infect
  lymph nodes.

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• This is followed by haematogenous spread with
  ultimate localization in the reticulo-endothelial
  system.
• Spread is usually by the ingestion of raw milk
  from infected cattle or goats, although
  occupational exposure(abbatoir workers, meat
  inspectors)is also common.
• Person-to-person transmission is rare.

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Clinical features

• The incubation period of acute brucellosis is 1-3
  weeks.
• The onset is insidious, with malaise, headache,
  weakness, generalized myalgia and night sweats.
• The fever pattern is classically undulant,
  although continuous and intermittent patterns are
  also seen.
• Lymphadenopathy, hepatosplenomegaly and spinal
  tenderness, sacro-iliitis (20-30) may be
  present arthritis, osteomyelitis,
  epididymo-orchitis (up to 40),
  meningoencephalitis and endocarditis have all
  been described.

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• Untreated brucellosis can give rise to chronic
  infection, lasting a year or more.
• This is characterized by easy fatiguability,
  myalgia, and occasional bouts of fever and
  depression.
• Splenomegaly is usually present.
• Occasionally infection can lead to localized
  brucellosis. Bones and joints, spleen,
  endocardium, lungs, urinary tract and nervous
  system may be involved.
• Systemic symptoms occur in less than one-third.

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complications
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• Although several diseases have a similar
  symptomatology, prolonged pyrexia with a history
  of contact with animals or animal products and
  without any specific diagnosis should arouse a
  suspicion of brucellosis.

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• Diagnosis
• Blood (or bone marrow) cultures are positive
  during the acute phase of illness in 50 of
  patients (higher in B. melitensis), but prolonged
  culture is needed.
• In chronic disease serological tests are of
  greater value. The brucella agglutination test,
  which demonstrates a four fold or greater rise in
  titre (gt 1 in 160) over a 4-week period, is
  highly suggestive of brucellosis.

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• Non-agglutinating IgG and IgA molecules can block
  the agglutinating reaction (prozone phenomenon)
  and the test should be carried out to a high
  dilution to avoid this.
• An elevated serum IgG level is evidence of
  current or recent infection a negative test
  excludes chronic brucellosis.
• In localized brucellosis antibody titres are
  low, and diagnosis is usually established by
  culturing the organisms from the involved site.

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• PCR for detection of Brucella in blood gives a
  rapid diagnosis, and along with measurement of
  IgG or IgM antibodies by ELISA, are highly
  sensitive and specific.
• Management and prevention
• Brucellosis is treated with a combination of
  doxycycline 200 mg daily and rifampicin 600-900
  mg daily for 6 weeks, the relapse/failure rate is
  10.

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• Alternatively, tetracycline can be combined with
  streptomycin, which is usually given for only the
  first 2 weeks of treatment. Relapse follows such
  treatment in 510 of patients
• Prevention and control involve careful attention
  to hygiene when handling infected animals,
  vaccination with the eradication of infection in
  animals, and pasteurization of milk.
• No vaccine is available for use in humans.

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Salmonellosis

• Enteric (typhoid) fever

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• Bacteria of the genus Salmonella (Gram-negative,
  motile, non lactose fermenting bacilli) are
  highly adapted for growth in both humans and
  animals and cause a wide spectrum of disease.
• The growth of serotypes S. Typhi and S.
  Paratyphi is restricted to human hosts, in whom
  these organisms cause enteric (typhoid) fever.
• More than 200 serotypes are pathogenic to humans,
  in whom they often cause gastroenteritis and can
  be associated with localized infections and/or
  bacteremia.

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• AETIOPATHOGENESIS
• Humans are the only reservoir of S. typhi.
  Organisms therefore originate from patients with
  typhoid, or from convalescent or chronic carriers
  excreting organisms in their stools.
• Human hands, flies, or insects then transfer
  these organisms to food or drink. Since S. typhi
  survive freezing and drying, infection can also
  occur through ice or canned food. Shellfish from
  polluted waters may transmit the disease.

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• Typhoid bacilli traversing the small intestine
  produce little epithelial cell damage, but gain
  access to the blood stream from intestinal
  lymphatics and Peyers patches.
• Bacilli are engulfed by reticulo-endothelial
  cells, but some multiply intra cellularly and
  then re-enter the blood stream to produce
  bacteraemia.
• Multiplication of organisms also takes place
  regularly in the gall bladder.

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CLINICAL FEATURES

• The incubation period averages 10 to 14 days.
• The onset of the disease is insidious, with
  headache, malaise, anorexia and fever.
• The fever is intermittent, sometimes increasing
  in a step-like manner to reach a peak towards the
  end of the first week. There after it plateaus
  and remains mildly remittent (38C to 40C) for
  two to three weeks.
• Accompanying chills are common but frank rigors
  are rare.

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• Headache is present and often disabling.
• Some cases progresses to mental dullness and
  delirium.
• Other symptoms in the early phase of the disease
  are dry cough and occasionally sore throat.
• Abdominal discomfort with mild bloating and
  constipation also occurs, but gives way during
  the second week to diarrhoea with pea soup
  stools.
• The spleen is usually palpable by the end of the
  first week.

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• The liver is mildly enlarged and tender and mild
  jaundice may be present.
• Acute renal failure and disseminated
  intravascular coagulation(DIC) are rare
  complications. The typical rash of typhoid
  develops in the second week "Rose spots" are
  macules which occur in small crops on the chest
  and abdomen they blanch on pressure and last for
  just 2-3 days.
• In the absence of complications, after 3-4 weeks
  the fever of typhoid disappears.

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Complications of typhoid
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• After clinical recovery 5-10 of patients will
  continue to excrete S. typhi for several months
  these are termed convalescent carriers.
• Between 1 and 4 will continue to carry the
  organism for more than one year this is chronic
  carriers.
• The usual site of carriage is the gall bladder,
  and chronic carriage is associated with the
  presence of gallstones.
• However, in parts of the Middle East and Africa
  where urinary schistosomiasis is prevalent,
  chronic carriage of S. typhi in the urinary
  bladder is also common.

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• Diagnosis
• Blood culture is the investigation of choice. In
  the first week of disease 70 to 90 of patients
  are culture-positive, but only 30 to 40 in the
  third week.
• Occasionally only bone marrow cultures may be
  positive, when antibiotics have been given.
  However all this depends on good laboratory
  facilities.
• Other clues to diagnosis are leucopenia of 2000
  to 4000/cumm and platelet count of under
  100,000/cumm.

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• Positive yields from stool and urine cultures
  increase with time and in stool is 70 by the end
  of the third week.
• The Widal test requires the demonstration of a
  four-fold rise in serum agglutinins against the
  somatic (O) antigen of the bacillus. Titres
  against the flagellar (H) antigen are less
  specific.
• Early antimicrobial therapy may alter the
  immunologic response.

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• Management
• Increasing antibiotic resistance is seen in
  isolates of S. typhi, especially in the Indian
  subcontinent.
• Chloramphenicol, co-trimoxazole and amoxicillin
  may all still be effective in some cases, but
  quinolones (e.g. ciprofloxacin 500 mg twice
  daily) are now the treatment of choice, although
  increased resistance to these agents is being
  seen in such cases azithromycin may be effective.

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• The patient's temperature may remain elevated for
  several days after starting antibiotics, and this
  alone is not a sign of treatment failure.
• Prolonged antibiotic therapy may eliminate the
  carrier state, but in the presence of gall
  bladder disease it is rarely effective.
• Cholecystectomy is not usually justified on
  clinical or public health grounds.

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Prevention

• good environmental sanitation and above all a
  ready supply of clean piped water.
• Immunization with two doses of traditional TAB
  vaccine affords limited protection for up to one
  year and is associated with local pain and fever.
• A live oral vaccine has been introduced which in
  three spaced doses provides protection for
  several years, but it requires refrigeration and
  a cold chain.
• By contrast the new injectable Vi polysaccharide
  vaccine is effective for about three years in a
  single dose.