7 pdf - د. اسامة

Infectious Lecture 4th Year 20-12-2016 Dr.Osamah Muwafk

Diseases associated with Listeria species :

1. Listeria Monocytogenes
2. L. ivanovii

(previously classified as L. Monocytogenes serotype 5) is
only mildly pathogenic and is an occasional cause of abortion
in sheep and cattle.

3. Listeria innocua

is occasionally associated with encephalitis in ruminants

ETIOLOGY

1. L. Monocytogenes

a) widespread in nature
b) survival and growth in a wide variety of environments
c) the organism
d) can grow and reproduce at temperatures between -

0.4°C and 45°C

e) It can grow between pH 4.5 and 9.6

Epidemiology:

1. occurrence, probably associated with seasonal feeding of

Silage

2. occurs mainly in the northern and southern latitudes
3. is much less common in tropical and subtropical than in

temperate climates

4. In ruminants it also produces syndromes of septicemia,

encephalitis, abortion, spinal myelitis, ophthalmitis/uveitis,
gastroenteritis, and mastitis

5. Source of infection :

a) It is truly ubiquitous in the environment

Infectious Lecture 4th Year 20-12-2016 Dr.Osamah Muwafk

b) can be commonly isolated from animal feces, human

feces, farm slurry, sewerage sludge, soil, farm water
troughs, surface water, plants, animal feeds and the
walls, floors, drains, etc. of farms and other
environments

6. Transmission by ingestion of contaminated material
7. Host management risk factors

a) Poor nutritional state
b) Sudden changes of weather to very cold and wet
c) The stress of late pregnancy and parturition
d) Transport
e) Long periods of flooding with resulting poor access to

pasture.

8. Zoonotic implications:

In humans, listeriosis may occur as a sporadic disease or as
a food-borne outbreak to produce septicemic disease,
meningoencephalitis, abortion and infection in other organs

PATHOGENESIS:

1.  ingestion of the organism
2.  penetration of the mucosa of the intestine
3.  survive and grow in macrophages and monocytes
4.  Bacterial superoxide dismutase protects against the

bactericidal activity of the respiratory burst of the phagocyte

5. listeriolysin O disrupts lysosomal membranes' allowing the

organism to grow in the cytoplasm

6. In pregnant animals:

a) invasion of the placenta and fetus cause edema and

necrosis of the placenta leads to abortion

Infectious Lecture 4th Year 20-12-2016 Dr.Osamah Muwafk

b) Infection late in pregnancy results in stillbirths or the

delivery of young that rapidly develop a fatal
septicemia

c) Maternal metritis

7. Encephalitis:

a) occurs as an acute inflammation of the brainstem and is

usually unilateral

b) The portal of entry is by ascending infection of the

trigeminal or other cranial nerves

c) following loss of the integrity of the buccal mucosa

resulting from trauma, the shedding of deciduous or
permanent teeth or from periodontitis

8. Spinal myelitis:

possibly results from ascending infection in the sensory
nerves of the skin following dermatitis from prolonged
wetting of the fleece

9. Mastitis

CLINICAL FINDINGS:

1. Listerial encephalitis

a) Fever 40°C
b) incoordination,
c) head deviation sometimes with head tilt
d) walking in circles
e) unilateral facial hypalgesia and facial paralysis

2. abortion

a) are recorded in cattle but occur more commonly in

sheep and in goats

b) In sheep and goats abortions occur from the 12th

week of pregnancy onwards,

Infectious Lecture 4th Year 20-12-2016 Dr.Osamah Muwafk

c) the afterbirth is usually retained
d) and there is a bloodstained vaginal discharge for

several days

3. Acute septicemia in newborn lambs and calves
4. In calves 3-7 days old, Corneal opacity is accompanied by

dyspnea, nystagmus, and mild Opisthotonos, Death
follows in about 12 hours

5. Infection in the udder

may involve a single quarter or both quarters; it is
chronic and poorly responsive to treatment

6. In Spinal myelitis

a) fever
b) ataxia with initial knuckling of the hindlimbs
c) progressing to hind limb weakness and paralysis

7. In Ophthalmitis and iritis

a) there is swelling of the iris
b) constriction of the pupil
c) white focal lesions are evident on the internal surface

of the cornea

d) a floccular material in the anterior chamber
e) One or both eyes are affected

CLINICAL PATHOLOGY

The organism can be cultivated from vaginal secretions for up
to 2 weeks after abortion

NECROPSY FINDINGS

a) Typically there are no distinctive gross changes associated

with listerial encephalitis.

Infectious Lecture 4th Year 20-12-2016 Dr.Osamah Muwafk

b) Visceral lesions occur as multiple foci of necrosis in the

liver, spleen, and myocardium in the septicemic form and
in aborted fetuses

c) Sheep with enteritis show ulcerative abomasitis and some

also have typhlocolitis at necropsy

DIFFERENTIAL DIAGNOSIS

1. Encephalitis:

a) Pregnancy toxemia in sheep
b) Nervous ketosis in cattle
c) Rabies
d) Gid
e) Polioencephalomalacia
f) Middle ear disease
g) Scrapie

2. Abortion:

causes of abortion in Sheep
causes of abortion in Cattle

3. Gastroenteritis:

a) Salmonellosis:

4. Uveitis:

a) Contagious ophthalmia

TREATMENT:

1. The recovery rate depends largely on the time that treatment

is started after the onset of clinical signs

2. The intravenous injection of chlortetracycline (10 mglkg BW

per day for 5 d) is reasonably effective in
meningoencephalitis of cattle but less so in sheep

Infectious Lecture 4th Year 20-12-2016 Dr.Osamah Muwafk

3. Penicillin at a dosage of 44 000 IU/kg BW given

intramuscularly daily for 7 days, and in many cases for 10-14
days, can also be used

4. Dehydration, acid-base imbalances and electrolyte

disturbances must also be corrected

5. Cases of spinal myelitis are poorly responsive to treatment.
6. Treatment of listerial iritis is with systemic antibiotics in the

early stages coupled with subpalpebral corticosteroid and
atropine to dilate the pupil.

CONTROL

1. Control is difficult because of the ubiquitous occurrence of

the organism,

2. Silage removed from the clamp should be fed as soon as

possible

3. A live attenuated vaccine

ANTHRAX

ETIOLOGY

1.  Bacillus anthracis
2.  is the specific cause of the disease
3.  pathogenic strains have plasmid-encoded virulent factors:

a) a polyD-glutamic capsule, which aids in resistance to

phagocytosis encoded by virulence plasmid pX02

b) a tripartite toxin comprised of edema (factor D)
c) lethal (factorII) antigen
d) protective antigen (factor III) encoded by plasmid pX0

Infectious Lecture 4th Year 20-12-2016 Dr.Osamah Muwafk

EPIDEMIOLOGY

1. It is often restricted to particular areas, the so-called 'anthrax

belts', where it is enzootic

2. In tropical and subtropical climates with high annual

rainfalls, the infection persists in the soil

so that frequent,

serious outbreaks of anthrax are commonly encountered.

3. In temperate, cool climates only sporadic outbreaks occurs
4. Source of the infection are

a) soil
b) from fodder grown on infected soil
c) contaminated bone meal or protein concentrates,
d) infected excreta, blood, or other discharges from

infected animals

5. Infection gains entrance to the body by ingestion, inhalation,

or through the skin

6. The disease occurs in all vertebrates
7. most common in cattle and sheep and less frequent in goats

and horses

8. relatively resistant pigs, dogs, and cats
9. outbreaks occur after a major climate change
10.

When material containing anthrax bacilli is exposed to

the air, spores are formed that protract the infectivity of the
environment for very long periods

11.

zoonotic potential :

a) Anthrax has been an important cause of fatal human

illness in most parts of the world

b) Cutaneous anthrax has occurred in veterinarians

following postmortem examination of anthrax carcasses

Infectious Lecture 4th Year 20-12-2016 Dr.Osamah Muwafk

PATHOGENESIS

1. ingestion of the spores
2. infection may occur through the intact mucous membrane

(through defects in the epithelium around erupting teeth, or
through scratches from tough, fibrous food materials).

3. The organisms are resistant to phagocytosis, in part due to the

presence of the poly-o-glutamic acid capsule

4. proliferate in regional draining lymph nodes
5. subsequently passing via the lymphatic vessels into the

bloodstream

6. septicemia, with massive invasion of all body tissues, follows
7. B anthracis produces a lethal toxin that causes edema and

tissue damage

8. death resulting from shock and acute renal failure and

terminal anoxia.

CLINICAL FINDINGS

Cattle and sheep

A. The peracute form:
1. is most common at the beginning of an outbreak
2. The animals are usually found dead without premonitory

signs

3. the course being probably only 1-2 hours
4. fever, muscle tremor, dyspnea, and congestion of the

mucosae may be observed.

5. The animal soon collapses, and dies after terminal

convulsions.

6. After death, discharges of blood from the nostrils, mouth,

anus, and vulva are common

Infectious Lecture 4th Year 20-12-2016 Dr.Osamah Muwafk

B. The acute form

1. Severe depression and listlessness are usually observed

first

2.  The body temperature is high, up to 42°C (107°F)
3.  the respiration rapid and deep
4.  the mucosae congested and hemorrhagic
5.  the heart rate much increased
6.  No food is taken and ruminal stasis is evident
7.  diarrhea and dysentery.
8.  Local edema of the tongue and edematous
9.  lesions in the region of the throat, sternum, perineum,

and flanks may occur

Horses

A. When infection is by ingestion:

there is septicemia with enteritis and colic.

B. When infection is by insect transmission:

a. hot, painful, edematous, subcutaneous swellings
b. appear about the throat, lower neck, floor of the thorax

and abdomen, prepuce, and mammary gland

CLINICAL PATHOLOGY:

1. peripheral blood or local edema fluid should be collected by

needle puncture

2. microscopic examination, of a clearly defined metachromatic

capsule on square-ended bacilli (often in chains) in a blood
smear stained with aged polychrome methylene blue

Infectious Lecture 4th Year 20-12-2016 Dr.Osamah Muwafk

NECROPSY FINDINGS

If there is a good reason to suspect the existence of anthrax the
carcass should not be opened

DIFFERENTIAL DIAGNOSIS

1.  Lightning strike
2.  Peracute blackleg
3.  Malignant edema
4.  Bacillary hemoglobinuria
5.  Hypomagnesemic tetany

TREATMENT

1. Penicillin (20000 IU/kg BW twice daily) has had

considerable vogue

2. streptomycin (8-10g/d in two doses intramuscularly for

cattle) is much more effective

3. Oxytetracycline (5 mg/kg BW per day) parenterally

CONTROL

1. placing of the farm in quarantine
2. Infected carcasses should not be opened but immediately

burned in situ or buried, together with bedding and soil
contaminated by discharges

3. vaccination of survivors

Infectious Lecture 4th Year 20-12-2016 Dr.Osamah Muwafk

INFECTIOUS FOOT ROT IN SHEEP

ETIOLOGY

1. Dichelobacter (Bacteroides) nodosus
2. F. necrophorum aids D. nodosus in the invasion of the foot

and contributes in the inflammatory reaction.

EPIDEMIOLOGY

1. Foot rot of sheep is common in all countries where there are

large numbers of sheep

2. Sheep are the species principally affected but goats are also

susceptible

3. The source of infection is the discharge from the active or

chronic infected feet

4. The organism does not survive in the environment for more

than a few days

5. Conditions of wetness and warmth favor persistence of the

bacteria in pasture and increase susceptibility of the feet to
injury and dermatitis

PATHOGENESIS

1. Maceration of the interdigital skin from prolonged wet

conditions underfoot allows infection with F. necrophorum.

2. This initial local dermatitis at the skin and the skin-horn

junction may progress no further

3. hyperkeratosis facilitates infection by D. nodosus.
4. The preliminary dermatitis has been named 'ovine interdigital

dermatitis' and is also called 'foot scald'

Infectious Lecture 4th Year 20-12-2016 Dr.Osamah Muwafk

CLINICAL FINDINGS

1.  a sudden onset of lameness
2.  more than one foot is affected
3.  affected sheep may graze on their knees
4.  swelling and moistness of the skin of the interdigital cleft
5.  There is destruction of the epidermal matrix beneath the hard

horn, which is subsequently separated from the underlying
tissues

6. There is a distinctive, foul-smelling exudate

Differential diagnosis

1.  Foot abscess
2.  Contagious ovine digital dermatitis (Shelly toe)
3.  Suppurative cellulitis
4.  Contagious echyma
5.  Bluetongue
6.  Foot and mouth disease
7.  Ulcerative dermatosis
8.  Strawberry foot rot
9.  Laminitis

10. Lameness associated with Erysipelothrix insidiosa

TREATMENT

1. Extensive paring of affected feet
2. Local applications include:

a. chloramphenicol (10% tincture in methylated spirits

or propylene glycol), oxytetracycline (5 % tincture in
methylated spirits), cetyltrimethyl ammonium
bromide or cetrimide (20% alcoholic tincture), zinc
sulfate (10% solution), copper sulfate (10% solution)

Infectious Lecture 4th Year 20-12-2016 Dr.Osamah Muwafk

and dichlorophen as a 10% solution in either
diacetone alcohol or ethyl alcohol.

3. Systemic antibiotic include:

a. Penicillin/streptomycin, Erythromycin, Long-acting

oxytetracycline, Lincomycin/spectinomycin