Respiratory Infections: Horses

– Streptococcus equi subsp equi

– Streptococcus equi ssp. zooepidemicus

– Streptococcus dysgalactiae ssp. equisimilis

What are three Streptococcus spp. that can infect the respiratory tract of horses

cocci that attract neutrophils (and something else?)

What is meant by a "pyogenic cocci"

Streptococcus spp.

You see these chains on cytology - what gram positive organism is it?

mucous membranes

What is the habitat of Streptococcus spp.?

antibodies - detecting the cell wall polysaccharide

What is the Serologic Classification scheme (Lancefield Grouping) of Strep. spp. based on?

Group C

What is the Streptococcus spp. classification of the Strep. spp. that infect horses?

S. equi ssp. equi

Which of the Streptococcus spp. is an obligate pathogen?

S. dysgalactiae ssp. equisimilis

S. equi ssp. zooepidemicus

Which two Streptococcus spp. are opportunistic pathogens and are part of the horse's normal micrbiota?

S. equi ssp. zooepidemicus

What Strep. spp. is common in wound infections?

Capsule - inhibits phagocytosis

M Protein - inhibits phagocytosis & adhesin

Toxins - Streptolysins (cytotoxic) Pyrogenic Exotoxins (superantigens)

The virulence factors of Strep. spp include a capsule, M protein, and toxins.

what do each of these factors allow the bacteria to do?

obligate

Streptococcus equi ssp. equi is an ____________ pathogen.

infected animalsshed up to 6 weeks after clinical signs

carriers (Guttural Pouch)

What is the source of Streptococcus equi ssp. equi?

highly contagious!

How contagious is Streptococcus equi ssp. equi?

Streptococcus equi ssp. equi

What obligate pathogen is the inciting agent of this abscessed lymph node?

Fever

Severe Inflammation

Abscesses

Lymph Nodes most affected

What does Streptococcus equi ssp. equi cause in its host?

Oral/Nasal Entry --> Replication in tonsils --> Spread to regional lymph nodes --> Inflammation: Neutrophils, Abscess formation, and Abscesses rupture

Describe the pathogenesis of Streptococcus equi ssp. equi

Streptococcus equi ssp. equi

What is the etiological agent of Equine Strangles?

Disseminated Abscesses

What is "Bastard Strangles"?

PCR on nasal swabs

Culture

How do we diagnose Strangles?

Supportive care

Antibiotics can prolong course of disease

Antibiotics typically only if difficulty breathing

How do we treat Strangles?

NAH fam

Are antibiotics warranted to treat Strangles?

Vaccines - attenuated, intranasal

How do we prevent Strangles?

upper respiratory tract

reproductive tract

mucous membrane

Streptococcus equi ssp. zooepidemicus and Streptococcus dysgalactiae ssp. equisimilis are commensal organisms of what parts of the horse?

Equine Pneumonia

Navel Infection

Uterine Infection

Wound Infection (in many species)

Streptococcus equi ssp. zooepidemicus and Streptococcus dysgalactiae ssp. equisimilis can cause what four infections/disease?

proper husbandry and sanitation

How can we prevent Streptococcus equi ssp. zooepidemicus and Streptococcus dysgalactiae ssp. equisimilis infections?

Culture

Susceptible to desiccation

How can we diagnose Streptococcus equi ssp. zooepidemicus and Streptococcus dysgalactiae ssp. equisimilis infections?

Antimicrobials

resistance is uncommon

How do we treat Streptococcus equi ssp. zooepidemicus and Streptococcus dysgalactiae ssp. equisimilis infections?

nope - it's uncommon

Is there much reported antimicrobial resistance to antimicrobials used to treat Streptococcus equi ssp. zooepidemicus and Streptococcus dysgalactiae ssp. equisimilis infections?

yes - less host-restricted than other Streptococci

canine, human cases reported

Does Streptococcus equi ssp. zooepidemicus have zoonotic potential?

positive

Rhodococcus equi is a gram __________ facultative anaerobe.

Virulence plasmid

Rhodococcus equi must contain what in order to cause disease?

• Soil

• Feces of adult animals

What is the source of Rhodococcus equi ?

Found in soil, feces of adult horses

Foals exposed in the first few days of life (from mom or in soil)

Direct contact

How is Rhodococcus equi transmitted?

a virulence plasmid

A certain Rhodococcus equi organism must have what in order to be virulent? (you best believe Dr. L is gonna ask about this)

• vapA positive strains are endemic on some farms

What are risk factors for Rhodococcus equi infections?

Can be, most human cases come from environmental sources

Is Rhodococcus equi zoonotic?

granulomatous

Rhodococcus equi causes _____________ inflammation of the lung; disseminated infections can occur

• Mares may shed organism and can be a source for foals • Thought that adults passively carry organism

How can Rhodococcus equi be shed?

Bacteria carrying virulence plasmid are inhaled and phagocytosed by alveolar macrophages --> these bacteria express virulence associated proteins like VapA (virulence associated protein A), a surface lipoprotein --> proteins allow bacteria to survive inside macrophages and other phagocytic cells --> bacteria can spread hematogenously to other sites in the body.

Describe the pathogenesis of Rhodococcus equi

alveolar

Concerning the pathogenesis of Rhodococcus equi: Bacteria carrying virulence plasmid are inhaled and phagocytosed by _________ macrophages

allows bacteria to survive inside macrophages and other phagocytic cells

Concerning the pathogenesis of Rhodococcus equi: bacteria express virulence associated proteins like VapA (virulence associated protein A), a surface lipoprotein, which will allow them to do what?

• Tachypnea

• Increased respiratory effort

• Tachycardia

• Coughing

• +/- mucopurulent nasal discharge

What are typical clinical signs of Rhodococcus equi infection?

typically occurs in foals 3 weeks of age to 6 months of age

Signs typically developing before 4 months of age.

Rhodococcus equi typically infects and causes disease in what aged animals?

• History - is it an endemic farm?

• Physical exam: Auscultation - crackles and wheezing, Fever

• Radiology/Ultrasound of the lungs

• Culture: BAL/TTW

How do we diagnose Rhodococcus equi infections?

Bronchoalveolar lavage/Trans tracheal wash

What are two methods of collecting a sample for culture of Rhodococcus equi ?

Rhodococcus equi

The lesions seen in this lung, are typical of what gram positive infectious agent?

- Supportive care

- Antibiotics

How do we treat Rhodococcus equi infections?

- Early recognition and intervention

- especially on endemic farms

• Hyperimmuneplasma

• Active Screening

How can we prevent Rhodococcus equi infections?

nah fam

Is vaccination available as a preventative measure for Rhodococcus equi infections?

- Temperature monitoring

- Visual inspection of foals,

- Monitoring clinical signs of pneumonia or extrapulmonary disorders

- Thoracic imaging using either radiography or ultrasonography.

What are four parts of active screening for Rhodococcus equi infections in foals?

- Immunocompromised people are at risk

• Particularly those with HIV or other diseases that affect CD4+/CD8+ T cell ratios.

Does Rhodococcus equi have zoonotic potential?