wk9 bacterial pathogens affecting hemolymphatic system

What is the lymphatic system?

• Part of the immune system and complementary to the circulatory system

  • includes lymph, lymph nodes, spleen, and other lymphatic tissues.

What is the liver's role relative to the lymphatic system?

The liver filters lymph but is not part of the lymphatic system.

How do infections of lymph nodes commonly present?

Infections often present as abscesses.

What types of infections do bacteria tend to cause in the hemolymphatic system?

Bacteria tend to cause pyogenic (purulent/neutrophilic) and/or necrotizing infections.

Why is it important to culture abscesses?

To differentiate causes that cannot be identified based solely on clinical signs and appearance

Why is it important to differentiate contagious vs non-contagious infections?

Different management strategies are required for contagious and non-contagious infections.

What are the Gram stain and oxygen requirements of Streptococcus equi subsp. equi and Streptococcus equi subsp. zooepidemicus?

gram positive Coccus, facultative anaerobe.

What are the Gram stain and oxygen requirements of Corynebacterium pseudotuberculosis and Trueperella pyogenes?

gram positive bacillus, facultative anaerobe.

What are the Gram stain and oxygen requirements of Fusobacterium necrophorum?

gram negative bacillus, obligate anaerobe.

What are the Gram stain and oxygen requirements of Clostridium (Tyzzerella) piliforme?

gram positive bacillus, obligate anaerobe.

What are characteristics of Streptococcus spp.?

• commensal bacteria

  • transmission via direct contact/fomites, ingestion, inhalation

• pyogenic infections of a wide variety of body sites in a wide variety of species

What disease does Streptococcus equi subsp. equi cause and in what species?

Strangles in horses.

What are the clinical signs of strangles?

• Fever, mucoid to mucopurulent nasal discharge

• lymphadenopathy (with or without abscessation and drainage) → difficulty swallowing and/or breathing.

What are important epidemiologic features of Streptococcus equi subsp. equi?

• Carrier horses are a source of infection

• highly contagious

• reportable disease in some states

• shedding for >6 weeks after recovery

• zoonotic

What is metastatic strangles?

• Hematogenous/lymphatic spread of bacteria beyond the upper respiratory tract

• abscess formation throughout the body at lymph node sites

  • abdomen > thorax

  • brain abscesses (rare)

What is purpura hemorrhagica?

• A type III hypersensitivity reaction causing severe necrotizing vasculitis.

  • Complexes of antibody-antigen get lodged into basement membranes of blood vessels → activates the complement system → attracts neutrophils to the body site

What system is activated in purpura hemorrhagica?

complement system

What type of vasculitis occurs in purpura hemorrhagica?

severe necrotizing vasculitis

clinical signs of Purpura Hemorrhagica

• edema of limbs, abdomen, mucous membranes

• skin sloughing

• secondary infections

What are sequelae of strangles?

Chronic carriers → source of infection for other horses

What are chondroids?

hardened purulent material in the guttural pouch; source of bacteria that the horse can continue to shed

Where is Streptococcus equi subsp. zooepidemicus found?

upper resp tract of horses

What bacteria is Streptococcus equi subsp. zooepidemicus normally?

commensal

What infections can Streptococcus equi subsp. zooepidemicus cause?

• Opportunistic infections of the respiratory, urogenital tract; abscesses in multiple body sites

• not typically contagious

What disease can Streptococcus equi subsp. zooepidemicus cause in dogs?

• hemorrhagic pneumonia

• contagious in kennel/shelter settings

How is Streptococcus diagnosed by culture?

Culture of abscess material or guttural pouch fluid or tissues

-nasal swabs or discharge

T/F: Streptococcus equi is not a normal flora

true

What molecular test is used for Streptococcus?

• PCR

  • Sample types: nasopharyngeal or guttural pouch
    swabs/fluids, tissues, unclotted blood (EDTA tube)

How is Streptococcus equi subsp. equi prevented?

• Vaccination with a live vaccine, not recommended during outbreaks.

• biosecurity (quarantine)

• hygiene

  • prevent fomite transmission

  • prevent environmental contamination

• supportive care

What antibiotic is used in severe cases of Streptococcus equi?

penicillin

What antibiotics are beta hemolytic strep susceptible to?

beta-lactam antibiotics

What does Corynebacterium pseudotuberculosis cause in animals?

• Causes pyogenic infections in multiple species

  • small ruminants

  • horses

  • cattle

  • humans

How is Corynebacterium pseudotuberculosis transmitted?

• direct contact/fomites (insects can act as mechanical vectors), ingestion (milk), inhalation

• contagious

What are features of external caseous lymphadenitis?

• More common in goats

• lymphadenopathy, submandibular abscesses which may burst or drain

What are features of internal caseous lymphadenitis?

• More common in sheep

• abscesses in tissues (including lungs and liver) clinical signs depend on body site

What syndrome occurs in sheep with caseous lymphadenitis?

thin ewe syndrome

What are zoonotic features of caseous lymphadenitis?

occupational exposure, raw milk consumption are risk factors

What are features of pigeon fever in horses?

• Abscess formation in pectoral muscles

• painful nodules/ulcers/draining tracts on limbs that follow the lymphatic chain (direct inoculation after skin trauma)

What are features of pigeon fever in cattle?

• Ulcerative lymphangitis is most common presentation

• Internal form of disease is rare

What is the gold standard for diagnosing Corynebacterium pseudotuberculosis?

• Culture

  • abscess material in sterile container, abscess capsule, milk > swabs

  • slower-growing

  • no interpretations for AST

What serology tests are used for Corynebacterium pseudotuberculosis?

• ELISA or SHI

  • serum or clotted blood

  • useful for herd screening

  • false positives/negatives

What causes false positives in serology for Corynebacterium pseudotuberculosis?

Vaccination or maternal antibody.

What causes false negatives in serology for Corynebacterium pseudotuberculosis?

Early infection or poor immune response.

What prevention is recommended for Corynebacterium pseudotuberculosis?

quarantine and test new animals

What species is the Corynebacterium pseudotuberculosis vaccine labeled for, and what species is it used off-label for?

• Labeled: sheep

• Off-label: goats

C. pseudotuberculosis treatment

• lance and drain abscesses

  • beware of environmental contamination

• surgical removal (horses)

What are important features of Trueperella pyogenes?

• Gram positive bacillus

• facultative anaerobe

• usually a secondary invader causing pyogenic infections.

Where is Trueperella pyogenes normally found?

urogenital, GI, resp tract

what does trueperella pyogenes usually cause

pyogenic infection/abscesses formation in multiple animal species

-non-contagious

What cattle infection occurs due to Trueperella pyogenes?

• Liver abscesses – grain diet decreases rumen pH
  (rumen acidosis); bacteria cross damaged rumen wall,
  enter circulation (in blood/lymph), and are showered
  throughout the liver

• summer mastitis - in dry cows, can be transmitted by flies

• sporadic abortion

What small ruminant infection occurs due to Trueperella pyogenes?

• abscess-forming

• important rule-out for CL (caseous lymphadenitis)

• sporadic infections, not contagious

Fusobacterium necrophorum characteristics

• obligate anaerobe

• commensal of ruminant GI tract; fecal-oral ingestion

what disease does Fusobacterium necrophorum cause in cattle

• liver abscesses; not detected til slaughter

• foot rot: inoculation into skin around hooves

  • major cause of lameness

What type of bacteria is Clostridium (tyzzerella) piliforme?

• spore-forming

• obligate intracellular

• fecal-oral route

What is Tyzzer's disease?

• Hepatic necrosis with possible gastrointestinal or heart lesions

• rodents, rabbits, wildlife, horses

• asymptomatic

How are liver abscesses diagnosed?

• Culture of abscess material, must request anaerobic culture for Fusobacterium.

• PCR for Clostriudium piliforme

  • tissues

• histopathology, immunohistochemistry

  • useful for C. piliforme

  • tissues

How are liver abscesses treated?

Drainage, supportive care, antimicrobial therapy.

What does PCR detect in Streptococcus equi subsp. equi?

The M protein

-useful in detecting carrier animal