Week 8

• Spirochetes

  • Gram-negative but stain poorly - Use darkfield microscopy or silver stains
  • Some grow in liquid media
  • Most require specialized media
  • Sensitive to dessication
  • Motile - Endoflagella in perplasm (number of flagella varies with genus), Move with corkscrew or flexing motion
• Borrellia

  • Grow slowly in specialized media
  • Transmitted by arthopod vectors
  • Maintained in 2 year enzootic life cycle - Involves ixodid ticks and mammals, deer and white footed mouse are common mammals involved that don't get infected, but serve as host for tick breeding and spatial distribution
  • Can cause disease in birds, mammal species, and humans
• Lyme borreliosis

  • Borrelia burgdorferi sensu stricto causes Lyme disease in North America
  • Reported in humans, horses, cattle, sheep
• Lyme Borreliosis Pathogenesis

  1. Outer surface protein (OSP) A: Adherence by borreliae to gut of the tick

  2. OSP C: Unregulated when feeding, protect borreliae in tick saliva and early stages of disease on host

  3. OSP F: Expressed in latter stages on disease on host

  4. Multiply in highest numbers in the skin

  5. Disseminate by bloodstream

  6. Unclear if disease is caused by active infection or host immune response
• Lyme disease in humans

  reportable and the most common vector borne bacterial disease in the US

  Antibiotic responsive

  Geographically limited

  Clinical syndrome vary depending upon infecting genotype, age, immune status
• Lyme disease clinical signs in humans

  • Flu-like illness
  • Trademark skin rash
  • Brain invasion
  • Nerve invasion (can cause permanent nerve damage)
  • Heart invasion
  • Joint invasion (can cause arthritis)
• Antibody titer does not predict illness
• Clinical signs in horses

  • Fever
  • Stiffness
  • Lameness in more than one limb
  • Muscle tenderness
  • Lethargy
  • Behavioral changes
  • Recurrent uveitis (possible)
• Co-infections with Anaplasma phagocytophilus complicate diagnosis from clinical sign perspective
• Lyme disease diagnosis

  1. Exposure to tick in endemic area & clinical signs

  2. Spirochetes present in low numbers in specimens

  3. SNAP test and C6 quantitative

  4. Large number of apparently asymptomatic dogs and horses are seropositive

  5. Quantitative ELISA and western blot

  6. Rising antibody titers to Borrelia burgdorferi

  7. Culture is confirmatory but slow

  8. PCR not useful

  9. Multiplex ELISA for dogs and horses
• Multiplex ELISA for dogs and horses

  • Vaccination = OSPA+
  • Early infection = OSPC+
  • Intermediate infection = OSPC+/OSPF+
  • Late infection = OSPF+
• Lyme disease treatment

  1. Dogs: Acute - Amoxicillin, Oxytetracycline; Chronic - Prolonged or repeated courses of treatment

  2. Horses: Tetracyclines better than doxycycline
• Lyme disease prevention

  1. Prevent tick infestation & prompt removal of attached tick

  2. Provision of early antimicrobial treatment after known Ixodes exposure

  3. Vaccines for dogs (don't prevent infection, reduce clinical signs, usually based on OspA)

  4. Vaccines for horses (recombinant OspA in ponies)

  5. Tick vaccination (mRNA vaccine administered to guinea pigs, turned tick bites red and inflamed, ticks fed poorly & fell of early, often failed to transmit Lyme-causing bacterium)
• Brachyspira

  • Colonize intestine
  • Cause disease in mammals and humans
• Brachyspira hyodysenteriae

  Causes swine dysentery
• Transmission of Brachyspira hyodysenteriae

  1. Fecal oral

  2. Asymptomatic carriers

  3. Rodents amplify disease

  4. Mechanical vectors
• Pathogenesis of Brachyspira hyodysenteriae

  1. Motility in mucus is an essential virulence factor

  2. Protease may be involved in disruption of colonic mucosa
• Clinical signs of swine dysentery

  • Bloody diarrhea
  • Dehydration
  • Weight loss
  • Emaciation
  • Large amounts of mucus in feces
• Diagnosis of swine dysentery

  1. Direct staining and observation in clinical specimens

  2. Fecal samples

  3. Tissues stained with Giemsa or silver staining

  4. Anaerobic culture

  5. PCR
• Treatment, control, and prevention of swine dysentery

  1. Antibiotic in drinking water

  2. Improved hygiene

  3. Alterations of diet

  4. Slaughter

  5. Through cleaning and disinfection of premises

  6. Rodent control

  7. Bacterin vaccines (controversial)
• Leptospira

  Reportable

  Zoonotic

  Endemic in tropical humid conditions

  Occupations disease (dairy and pig farmers, veterinarians)

  Increasing importance in those who partake in water sports

  Resemble febrile illnesses (dengue, malaria, influenza)

  Highly motile helical bacterial with hook shaped ends
• Leptospira cross absorption of rabbit antisera against defined serovars

  Used to determine serovar of an isolate
• Leptospira serovars with antigens in common

  Belong to same serogroup
• Classification of Leptospira

  Based on DNA and serum reactions<|>Same serovar different leptospira species<|>Same species different serovars
• Serological classificationof Leptospira

  Clinically important

  Particular serovars associated with specific host animals (maintenance host, incidental host)

  Cross-immunity between serovars minimal
• Pathogenicity of Leptospira

  1. Surface proteins and motility allow invasion of tissue

  2. Invade through moist softened skin or intact mucous membranes

  3. Chemotaxis to hemoglobin related to initiation of infection

  4. Spread throughout the body via blood stream

  5. Hemolysin damages red cell membranes

  6. Cause hepatocellular injury in acute infections

  7. Colonize renal tubules, uterus, eye, or meninges

  8. Eliminated by urine

  9. Cause bacteremic phase with petechial hemorrhages, acute and chronic inflammation of liver and kidneys
• Diseases caused by Leptospira in livestock

  • Hepatitis
  • Nephritis
  • Placentitis
  • Abortion
  • Mastitis
  • Local infection of genital tract leading to infertility
• Diseases caused by Leptospira in humans

  • Flu-like disease
  • Complications from renal, pulmonary, hepatic, CNS disease
• Diagnosis of Leptospirosis

  1. Clinical signs and exposure to contaminated urine suggest acute leptospirosis

  2. Dark Field microscopy for organism detection in urine (low sensitivity)

  3. Culture requires special media and may take several weeks

  4. Blood isolation in early days, urine isolation 2 weeks after infection

  5. Fluorescent antibody for leptospires in tissues

  6. PCR on blood, urine, and tissue samples

  7. Microscopic agglutination test is gold standard (titers 1:400 or above, four-fold rise in paired samples)

  8. Difficult to distinguish vaccinated, acutely infected, and recovered animals

  9. ELISA for Leptospira borgpetersenii serovar Hardjo in cattle and sheep
• Spirochetes

  commensals

  zoonotic infections

  agents of systemic or intestinal infections

  serological methods used for epidemiological investigations and clinical diagnosis

  classified on basis of genetic relatedness
• Campylobacter spp.

  Slender, curved, gram negative rods with polar flagella
• Campylobacter spp.

  • Extracellular pathogens
  • Motile, microaerophilic
  • Grow optimally at 25C
  • C. jejuni 5 days at 42C
  • Grow on MacConkey agar
  • Most species difficult to isolate
  • Need enhanced growth on enriched media
• Campylobacter spp.

  Commensals of intestinal tracts; sometimes reproductive tracts

  Opportunistic pathogens
• Campylobacter spp. cause diarrhea, infertility or abortion
• Campylobacter spp. survive under moist conditions, some strains tolerate cold, and remain viable in feces, milk, water, vaginal discharge, and poultry litter
• Smears stained with dilute carbol fuchsin for 4 minutes


  Stains more intensely than gram
• Bovine genital campylobacteriosis

  (Campylobacter fetus subsp. venerealis)
• Transmission of bovine genital campylobacteriosis

  1. Coitus from asymptomatic carrier bulls

  2. May remain infected indefinitely in prepuce

  3. ⅓ infected cows become carriers

  4. Persists in the vagina
• Bovine genital campylobacteriosis can cause endometritis, salpingitis, temporary infertility with early embryonic death, return to estrus at irregular periods, and sporadic abortion
• Natural immunity to bovine genital campylobacteriosis

  Lasts up to 4 years

  IgA from vagina limits spread

  IgG from uterus opsonize pathogens