Bacterial Diseases of Wildlife

1
Bacterial Diseases of Wildlife

• Tularemia
• Brucellosis
• Lyme borreliosis
• Anthrax
• Bovine Tuberculosis

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Tularemia aka rabbit fever

• Basic Micro
• Francisella tularensis
• Gram negative
• Phylum Proteobacteria Class Gamma
  
• Obligate aerobic
• Non-spore-forming
• 4 known subspecies
• Type A more virulent N. America
• Type B less virulent - Europe

In liver cells
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Animal Clinical Signs
Lagomorphs very susceptible Depression, anorexia, ataxia, roughened coat, tendency to huddle, weakness, fever, ulcers, abscesses at site of infection, swelling of regional lymph nodes, sudden death caused by septicemia.
Rodents very susceptible Depression, anorexia, ataxia, roughened coat, tendency to huddle.
Sheep - susceptible Sudden onset of fever, lethargy, anorexia, stiffness, reduced mobility, signs of septicemia, depression, dysnpnea, diarrhea, lag behind rest of the herd, coughing, pollakiuria, abortions, carry heads high when walking, weak or rapid pulse, frequent urination, death.
Dogs fairly resistant Low fever, mucopurulent ocular and nasal discharge, abscesses at site of infection, axillary and inguinal vesiculopapular rash, loss of appetite, listlessness, lymphadenopathy, anorexia.
Humans Fever, localized skin or mucous membrane ulceration, regional lymphadenopathy, and, occasionally, pneumonia.
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Tularemia

• Pathogenic features
• Pili (attachment to host tissue)
• Capsule (protects against complement)
• Facultative intracellular (cytoplasm of host
  macrophages)
• AcpA acid phosphatase, inhibits respiratory
  burst (avoid destruction by phagocytes)
• Siderophore (small molecules that bind iron, then
  taken up by bacterium)
• 30 kb pathogenicity island iglC (escape), pdpD,
  pdpA - unknown

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Tularemia

• Transmission and Epidemiology
• Can persist for long periods of time in moist
  environs (water, mud, decaying animal carcasses).
• Reservoirs
• Natural - small and medium-sized mammals
• North America leporidae, castoridae, muridae,
  sciuridae
• Natural - Acanthamoeba
• Incidental - humans, other mammalian species,
  some species of birds, fish, and amphibians.
• Vectors
• Hard ticks primary vector of Type A -
  transovarian
• Biting flies
• Mosquitoes

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Tularemia

• Pathology
• Infection dose,10 cells
• To regional lymph nodes
• Engulfed by macrophages
• Escape from phagosome into cytoplasm within 3-4
  hours

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Lymph nodes show well-defined zones of necrosis,
predominantly in the outer cortex.
100X
400X
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Tularemia

• Pathology
• Hematogenic dissemination to liver, spleen, lungs

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The most common pulmonary histologic finding is
suppurative pneumonia with areas of necrosis and
hemorrhage.
10
Sections of liver showed rounded microabscesses.
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Tularemia

• Pathology
• Typical lesions are pale white to gray, often
  slightly raised necrotic foci, ranging in size
  from pin-point to a few millimeters in diameter.
• Impairment of organ functions (liver, spleen,
  lungs)
• Death in susceptible 2-10 days

12
Brucellosis aka Malta fever, Bangs disease,
undulant fever

• Basic Micro
• Brucella
• B. abortus (cattle)
• B. melitensis (goats)
• B. suis (swine)
• B. ovis (sheep)
• B. canis (dogs)
• Gram negative
• Phylum Proteobacteria
  Class alpha
• Aerobe
• Non-spore-forming

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Animal Clinical Signs
Domestic, feral, wild Abortion, retained placenta, enlarged testicles, pendulous scrotum
Humans Acute febrile disease - fever 38-40C. Unusually severe limb and back pain, sweating and fatigue are marked. On physical examination, splenomegaly may be the only finding. Untreated, symptoms may continue for 2 - 4 weeks.
Persistent disease - arthritis, often sacroiliitis, and spondylitis (in about 10 of cases), CNS effects including meningitis (in about 5).
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Brucellosis

• Pathogenic features
• Lacks classical virulence factors
• Facultative intracellular in monocyte-macrophages
• Cell-wall polysacc protects cell from phagosome
  and inhibits apoptosis
• Escapes phagosome, replicates in ER
• Enterobactin (iron chelator)
• Stimulates polyclonal B cell activation

entering a macrophage
massive proliferation in macrophage
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Brucellosis

• Transmission and Epidemiology
• Transmitted via ingestion of contaminated feed,
  licking infected fetus, calf, placenta also
  conjunctival, inhalation
• Reservoirs
• various wild, feral and (particularly) domestic
  animals. In ruminants, enormous numbers of
  bacteria are shed widely from infected products
  of conception, whether aborted or born at term.
  Brucellae frequently invade the mammary gland of
  infected ruminants.
• Individuals are infected for life, and herds are
  chronically infected

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Brucellosis

• Pathology
• Invades from point of entry
• Bacteremia entry into phagocytes
• Initial localization in regional lymph nodes and
  spleen.
• Invasion of reproductive organs
• Severe inflammation of the placenta prevents
  oxygen and nutrient delivery to fetus and removal
  of waste products ? fetal death
• Alternately hormonal dysregulation results in
  premature delivery.

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Lyme

• Most prevalent tick-borne disease of humans in US
  20,000/yr
• Basic Micro
• Borrelia burgdorferi
• Gram negative
• Spirochete

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Lyme

• Pathogenic features
• Erp outer membrane lipoproteins (protect from
  complement-mediated killing)
• One of the few pathogens that does not require
  iron.
• Different genes expressed in tick vs mammal.

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Lyme

• Transmission and Epidemiology
• Natural reservoir white-footed mouse
• Vector ticks in the genus Ixodes

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Lyme
21
Lyme

• Pathology
• Deposited in skin by ticks during feeding
• Replicate in dermis for 1wk
• Disseminate to distant cutaneous sites, organs,
  joints
• Localized inflammatory response triggered by
  surface antigens w/ unusual prod. of interleukin
  and interferon

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Anthrax

• One of oldest diseases known account in the
  book of Exodus
• Basic Micro
• Bacillus anthracis
• Gram positive
• Phylum Firmicutes Class
  Bacilli
• Obligate aerobe
• Spore-forming

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Anthrax

• Pathogenic features
• Capsule
• Toxin complex consisting of
• Cell-receptor binding protein called protective
  antigen
• Two separate toxins
• Edema factor (EF)
• Lethal factor (LF)
• Toxin complex works to
• prevent apoptosis
• increase capillary permeability
• reduce blood clotting

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Anthrax

• Symptoms that may appear immediately before death
  are high temperatures, bloody discharge, and
  swelling in the neck and shoulder areas.
• Carcasses dark blood, not clotting. Bloody
  serous discharges from nose, etc.

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Anthrax

• Transmission and Epidemiology
• Persistence depends on extreme virulence, death
  of the host, and survival of highly resistant
  spores in the environment for prolonged periods.
• Infects a wide range of homeothermic species
  (body temp is critical).
• Carcasses of dead
  
  animals attract
  
  scavengers that free
  
  vegetative cells and
  
  disperse them over a wide area.
• Herbivores are much
  more
  susceptible than
  carnivores but
  
  carnivores and
  
  scavengers are
  carriers
  of spores,
  transmitted in feces.

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Anthrax

• Complicated life cycle
• Vegetative B. anthracis require aerobic and high
  nutrient conditions.
• When host dies, tissues become anaerobic.
• B. anthracis are held in stasis, unable to
  replicate or sporulate
• Anaerobic bacteria
  from GI, esp.
  
  Clostridium spp.
  decompose carcass.
• Carcass is opened
  and vegetative
  
  B. anthracis dispersed.

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Anthrax

• Complicated life cycle.
• In the environment, low nutrient conditions and
  dehydration stimulate sporulation.
• Spores resistant to extremes of temp., UV,
  desiccation, chemicals
• Epidemics tend to occur in moist lowland areas
  where soil is high in organic content, in dry
  summer months following period of heavy rain or
  floods role of water.

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Anthrax

• Pathology
• 3 routes of entry
• Gastrointestinal across intact mucous membranes
  or defects in epithelium of oropharynx or GI
• Cutaneous spores enter through cuts and
  abrasions
• Inhalational spores inhaled to alveoli of lungs
• Spores germinate into vegetative cells
• Carried to lymph nodes

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Anthrax

• Pathology
• Cross into bloodstream and disseminate via
  circulation
• Terminal blood concentration greater than 107
  CFU/mL.
• Produce toxins
• Edema
• Shock
• Acute renal failure
• Terminal anoxia
• Death

In bovine blood
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Bovine tuberculosis

• Mycobacterium bovis is the causative agent of
  tuberculosis in a range of animal species and
  man, with worldwide annual losses to agriculture
  of 3 billion.
• Basic Micro
• Mycobacterium bovis
• Gram positive, rods
• Acid-fast
• Phylum Acintobacter
• Aerobic

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Bovine TB

• Pathogenic features
• Intracellular in macrophages
• Prevent phagosome-lysosome fusion

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Bovine TB

• Transmission and Epidemiology

• M. bovis can be transmitted by the inhalation of
  aerosols, by ingestion, or through breaks in the
  skin. The importance of these routes varies
  between species.
• Bovine tuberculosis is usually maintained in
  cattle populations, but a few other species can
  become reservoir hosts. Most species are
  considered to be spillover hosts.

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Bovine TB

• Transmission and Epidemiology

• Natural, primary host cattle
• Maintenance hosts - brushtailed opossums (and
  possibly ferrets) in New Zealand, badgers in the
  United Kingdom and Ireland, bison and elk in
  Canada, and kudu and African buffalo in southern
  Africa. White-tail deer in MI and MN.
• Spillover - sheep, goats, horses, pigs, dogs,
  cats, ferrets, camels, llamas, many species of
  wild ruminants including deer and elk elephants,
  rhinoceroses, foxes, coyotes, mink, primates,
  opossums, otters, seals, sea lions, hares,
  raccoons, bears, warthogs, large cats (including
  lions, tigers, leopards, cheetahs and lynx) and
  several species of rodents.
• Most mammals may be susceptible.

34
Bovine TB

• Transmission and Epidemiology

• Cattle shed M. bovis in respiratory secretions,
  feces and milk, and sometimes in the urine,
  vaginal secretions or semen. Large numbers of
  organisms may be shed in the late stages of
  infection.
• Some animals become infected when they ingest the
  organism this route may be particularly
  important in calves that nurse from infected cow.

35
Bovine TB

• The symptoms of bovine tuberculosis usually take
  months to develop in cattle. Infections can also
  remain dormant for years and reactivate during
  periods of stress or in old age.
• Similarly, severe disease can develop in some
  deer within a few months of infection, while
  other deer do not become symptomatic for years.

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Bovine TB

• Symptoms
• Tuberculosis is a chronic, progressive disease
  that can cause gradual debilitation and is
  manifest as emaciation, depression, and
  intolerance to exercise.
• Because infection often involves the lungs,
  coughing, nasal discharges, and difficulty
  breathing can occur in severe cases.
• In some instances, superficial lymph nodes in the
  neck will develop large abscesses that may
  rupture and drain through the skin.

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Bovine TB

• Pathology
• tiny droplets containing 1-3 bacteria reach the
  alveoli (10-200 droplets)
• phagocytized by un-activated alveolar macrophages
• M. bovis survive
• impair normal phagocyte functions
• multiply
• young phagocytes are actively recruited but dont
  kill

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Bovine TB

• Pathology
• local infection
• spread via lymphatics to regional nodes
• then thru blood to any other organ
• spread to CNS, spongy bone, liver, kidney,
  genitals
• host immune response usually kills infected
  macrophages and halts infection

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Bovine TB

• Pathology
• At necropsy, tuberculosis lesions are variable in
  appearance and size.
• Subclinically infected animals may have one or a
  few small necrotic nodules that usually are
  associated with the lymph nodes of the head and
  neck or the lungs.

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Bovine TB

• Pathology
• More severely infected cervids can have multiple
  pea-sized nodules or large cheesy or pus-filled
  masses in the same areas. The classical tubercle,
  which is firm, white or pale yellow, and gritty
  when cut, does occur in cervids, but many M.
  bovis lesions in these animals are filled with
  pus.
• In cervids, tuberculous lesions are most often
  seen in the lymph nodes of the head and neck or
  in lung tissue however, lesions can occur
  throughout the chest cavity, under the skin of
  the chest, and in the abdominal cavity as well.