Lecture 12: Infections of the Nervous System 3

H. parasuis and H. somni shape

coccobacillary (short rods) and may form short filaments

H. parasuis and H. somni do not grow on

MacConkey agar

what do H. parasuis and Avibacterium paragellinarum require?

growth factor V (NAD)

what is the optimal growth for H. parasuis and H. somni to occur?

5 to 10% CO2 on chocolate agar

most organisms of H. parasuis and H. somni form

small, transparent dewdrop-like colonies after incubation of 48 hours

H. somni does not require

growth factors X and V

what is typical of the Haemophilus species?

satellitism around a V factor-producing bacterium

H. somni characteristics

• no growth factor

• catalase negative

• oxidase positive

H. parasuis characteristics

• growth factor V

• catalase positive

• oxidase negative

disease of H. somni and H. parasuis occurs

opportunistically due to predisposing factors

virulence factors of H. somni

• endotoxin

• phase variation of its lipo-oligosaccharide and evasion of immune host

• production of transferrin-binding proteins and immunoglobulin-binding proteins

lipo-oligosaccharide is involved in

induction of apoptosis of endothelial cells and leukocytes

what do immunoglobulin-binding proteins do?

bind the Fc portion of IgG2 and responsible for resistance of complement-mediated killing in serum

H. somni will produce an exopolysaccharide and filamentous haemagglutinin proteins involved in

biofilm formation

diagnostic procedures of H. somni

• clinical specimens should be frozen in dry ice and delivered to lab within 24 hours

• use either chocolate agar or blood agar inoculated with a streak of S. aureus

identification criteria for H. somni

• small, dew-drop like colonies after 1-2 days

• enhancement of growth by CO2

• requirement of X and V growth factors

• biochemical growth profile

H. somni in cattle will cause

septicemia, thrombotic meningoencephalitis, bronchopneumonia, etc

H. somni in sheep will cause

epididymitis in young rams, vulvitis, mastitis, and reduced repro performance in ewes

H. parasuis in pigs will cause

Glasser’s disease

what is H. somni a part of?

normal bacterial flora of male and female bovine genital tracts

what contributes to infections of H. somni?

environmental stress factors

clinical signs of infection caused by H. somni in cattle

• septicemia

• thrombotic meningoencephalitis (TME) → encountered in young cattle recently introduced to feedlots

• some animals may be found dead or found with fever, depression, blindness, lameness, ataxia

• sudden death due to myocarditis

• arthritis

H. somni is commonly isolated from the

enzootic calf pneumonia complex

diagnosis of infection caused by H. somni in cattle

• severe neurological signs in young feedlot cattle

• multiple foci of hemorrhagic necrosis

• confirmation of disease from CSF

treatment of H. somni in cattle

• isolation of affected animals

• oxytetracycline used for therapy

• penicillin

healthy sheep may carry ovine strains of H. somni in

prepuce or vagina

what does H. somni cause in young rams?

epididymitis

what does H. somni cause in ewes?

vulvitis, mastitis, and reduced reproductive performance

what can H. somni cause in lambs?

meningitis

Glasser’s disease is caused by

Glaesserella (Haemophilus) parasuis

Glasser’s disease manifests as

polyserositis and leptomeningitis

H. parasuis is part of normal flora of

upper respiratory tract of pigs

how do piglets acquire H. parasuis?

infection by direct contact or aerosols from sows shortly after birth

clinical signs of Glasser’s disease

• incubation period of 1-5 days

• clinical signs develop 2-7 days after exposure

• anorexia

• pyrexia

• lameness, recumbency, convulsions

• cyanosis and thickening of the pinna

diagnosis of Glasser’s disease

• isolation and identification of G. parasuis from joint fluid, heart blood, post-mortem tissues of a recently dead pig are confirmatory

• post-mortem includes polyserositis, polyarthritis, and meningitis

treatment and control of Glasser’s disease

• antimicrobial drugs like tetracycline, penicillin, and potentiated sulfonamides

• eliminate stress factors

what is the causative agent of cryptococcosis?

Cryptococcus neoformans, which is a capsulated yeast

the causative agent of cryptococcosis is NOT a

dimorphic fungus

disease of cryptococcosis is more common in

cats

what is the reservoir of cryptococcosis?

soil especially associated with pigeon excreta

clinical signs of cryptococcosis in cats

• sneezing, labored breathing, nasal discharge

• hard, nodular skin swellings, most often over the bridge of the nose

• distortion of the nasal cavity as a result of bone invasion

• neurologic abnormalities

• eye disorders

Cryptococcus neoformans remains in the yeast form in both

environment and host

yeast form of Cryptococcus neoformans

• inhalation of unencapsulated yeast cells from the environment

• capsulation of yeast in vivo

• nasal mucosa is site of most primary infections

treatment of cryptococcus

• surgical intervention, cryotherapy

• antifungals

what is the zoonotic potential of cryptococcus?

extremely low but immunocompromised individuals at risk