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20 Cards in this Set

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Describe the morphological characteristics of Strep.
Gram positive cocci, catalase negative, fastidious. Genus has many species but few are pathogenic.
What catergories are Strep species grouped into?
Alpha, beta and gamma depending on the degree of haemolysis. Alpha is partial, beta is total and gamma is non-haemolytic.
What is the other classification scheme for Strep?
Lancefield classification based on cell wall antigens. Has the disadvantage of many vet species fit into more than one class, or none at all.
What are the virulence factors for Strep?
Molecules on the surface which inhibit phagocytosis, molecules which act as molecular glue, mimicry (able to produce products antigenically similar to host) and Ag disguise (the ability to recognise host antigens as protective and utilise them)
Where does Strep produce infection?
Skin and mucous membranes.
What type of pathogen is Strep?
Opportunist (generally very few primary pathogens)
What are some common diseases caused by Strep in humans?
Strep throat, scarlet fever, acute rheumatic fever.
What other type of infection is Strep notorious for causing?
Nosocomial
What is the Strep species 'strangles' is caused by?
S. equi sub species equi
What are the Strep species causing mastitis?
S. uberis, S. agalactiae and S. dysgalactiae.
What animals will get strangles?
Weanling horses.
Is it contagious?
Yes, very.
Describe the disease seen in strangles.
Severe URT infection and suppurative lymphadenitis.
What is the method of transmission?
Oronasal infection with pus/respiratory droplets from an infected animal.
What other effects would occur after acute infection?
Neutrophilia and fever.
What is the incidence/mortality of strangles?
High incidence, low mortality.
However some farms may see this as a continual problem.
Describe the clinical signs of the disease.
Fever, depression, URT infection. Progressing some days later to hot, painful lymphadenitis which suppurates. May lead to compression of airways
Describe the three characteristic complications to recovery of strangles.
Bastard strangles = haematogenous spread of the bacteria to internal organs, leading to abscessation/pneumonia.

Purpura haemorrhagica = immune complex vasculitis (type III hypersensitivity rxn).

Chronic guttural pouch empyema = convalescent harbouring of the bacteria.
What would be the treatment for purpura haemorrhagica and why?
Corticosteroids because its an immune mediated condition.
What is the incubation time for strangles?
3-14 days.