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Infectious Lecture 4th Year 3-1-2017 Dr.Osamah Muwafk

GLANDERS :

ETIOLOGY:

1. Burkholderia (Pseudomonas) mallei

EPIDEMIOLOGY

1. Glanders is restricted geographically to Eastern Europe, Asia

Minor, Asia, and North Africa

2. It was more widespread but has been eradicated from most

countries

3.  Horses, mules, and donkeys are the species usually affected
4.  Humans are susceptible and the infection is usually fatal
5.  B. mallei is an obligate parasite and is readily destroyed by

light, heat, and the usual disinfectants

6. Infected animals or carriers that have made an apparent

recovery from the disease are the important sources of
infection

7. Chronic nodular lung lesions, which have ruptured into the

bronchi, infest upper airway passages and nasal or oral
secretions

8. Spread to other animals occurs mostly by ingestion
9. the cutaneous form appears to arise through contamination of

skin abrasions

10.

Horses tend to develop the chronic form, mules and

donkeys the acute form

11.

The disease is more likely when animals are in a

stressed state

12.

Zoonotic implications: infection may gain access

through skin abrasions to produce granulomatous disease and

Infectious Lecture 4th Year 3-1-2017 Dr.Osamah Muwafk

pyemia or from inhalation of infectious material and the case
fatality is high

PATHOGENESIS:

1. Invasion occurs mostly through the intestinal wall
2. A septicemia (acute form) or bacteremia (chronic form) is set

3. Localization always occurs in the lungs but the skin and nasal

mucosa are also common sites

4. Other viscera may become the site of the typical nodules
5. Deaths in typical cases are caused by anoxic anoxia

CLINICAL FINDINGS:

A. Acute disease

1.  There is a high fever
2.  cough, and nasal discharge
3.  rapidly spreading ulcers appearing on the nasal mucosa
4.  nodules on the skin of the lower limbs or abdomen
5.  Death due to septicemia occurs in a few days

B. Chronic disease

  Three major manifestations are described:
  1. Pulmonary
  2. Skin
  3. Nasal, although the chronic nasal and skin forms
      commonly occur together

A. Pulmonary form of disease:

manifests as a chronic pneumonia with cough, frequent
epistaxis, and labored respiration

B. Nasal form of disease:

Infectious Lecture 4th Year 3-1-2017 Dr.Osamah Muwafk

1) Lesions appear on the lower parts of the turbinates and

the cartilaginous nasal septum

2) They commence as nodules (1 cm in diameter), which

ulcerate and may become confluent

3) In the early stages there is a serous nasal discharge

which may be unilateral and which later becomes
purulent and blood stained

4) Enlargement of the submaxillary lymph nodes is a

common accompaniment

5) On healing, the ulcers are replaced by a characteristic

stellate scar

C. The skin form

1) is characterized by the appearance of

subcutaneous nodules (1-2 cm in diameter)

2) which soon ulcerate and discharge pus of the

color and consistency of dark honey

3) Thickened fibrous lymph vessels radiate from

the lesions and connect one to the other

D. Animals affected with the chronic form are usually ill

for several months

CLINICAL PATHOLOGY:

1) Mallein test
2) The complement fixation test on serum
3) Demonstration of the organism

NECROPSY FINDINGS:

1) In the acute form there are multiple petechial hemorrhages

throughout the body and a severe catarrhal

Infectious Lecture 4th Year 3-1-2017 Dr.Osamah Muwafk

bronchopneumonia with enlargement of the bronchial lymph
nodes

2) chronic form, the lesions in the lungs take the form of miliary

nodules, Ulcers are present on the mucosa of the upper
respiratory tract, Nodules and ulcers may be present in the
skin and subcutis of the limbs

DIFFERENTIAL DIAGNOSIS:

1) Epizootic lymphangitis
2) Ulcerative lymphangitis
3) Sporotrichosis
4) Melioidosis
5) Other causes of pneumonia

TREATMENT:

1. Sodium sulfadiazine has been highly effective
2. Treatment for a period of 20 d was necessary to effect 100%

recovery

CONTROL:

1.  Complete quarantine of affected premises is necessary
2.  Clinical cases should be destroyed
3.  remainder subjected to the mallein test at intervals of 3 weeks

until all reactors have been removed

4. A vigorous disinfection program for food and water troughs

and premises generally should be instituted to prevent spread
while eradication is being carried out

5. Restriction of the movement of horses should be instituted

and the mallein test carried out in horses which may have had
contact with the infected group

Infectious Lecture 4th Year 3-1-2017 Dr.Osamah Muwafk

EPIZOOTIC LYMPHANGITIS

(PSEU DOGLANDERS, EQUINE BLASTOMYCOSIS, EQUINE
HISTOPLASMOSIS)

ETIOLOGY

1. A fungus, Histoplasma capsulatum var. farciminosum, a

dimorphic

2. Fungal soil saprophyte

EPI DEM IOLOGY:

1. Occurs as outbreaks in horses, donkeys and mules
2. Recorded in parts of Iran, Asia, India, Northern Africa, and

the Mediterranean littoral

3. Most outbreaks occur in autumn and winter
4. Occur if large numbers of horses are gathered together for

military or other purposes

5. Transmission of the fungal spores by direct contact or on

bedding, grooming utensils, horse blankets

6. Biting flies may play a role in the transmission of the disease
7. Infection is reported in humans

PATHOGENESIS

1.  After gaining entry through wounds
2.  the fungus invades subcutaneous tissue
3.  sets up a local granuloma or ulcer
4.  spreads along the lymphatic vessels
5.  inoculation of the organism into the eye by biting flies lead to

the ocular form of the disease

CLI NICAL FINDINGS

Infectious Lecture 4th Year 3-1-2017 Dr.Osamah Muwafk

1. primarily an ulcerating, suppurative, pyogranulomatous

dermatitis

2. lymphangitis
3. An ocular form of the disease is characterized by an

ulcerating conjunctivitis

4. In the cutaneous form

a) an indolent ulcer develops at the portal of entry
b) making its appearance several weeks to 3 months

after infection occurs

c) A spreading dermatitis and lymphangitis
d) evident as corded lymphatics with intermittent

nodules, develops

e) Nodules rupture, discharging a thick creamy pus
f) Local lymph nodes also enlarge and can rupture
g) Thickening of the skin in the area and general

swelling of the whole limb are common

h) The lesions are quite painless
i) The lesions usually develop on the limbs, particularly

about the hocks

5. Ocular involvement is manifested by keratitis and

conjunctivitis

6. The disease is chronic, persisting for 3-12 months
7. Spontaneous recovery occurs and immunity is solid

CLINICAL PATHOLOGY:

1. Gram-positive, yeast-like cells, with a characteristic double-

walled capsule, are easily found in discharges

2. The organisms are located both extracellularly and

intracellularly in giant cells and macrophages

NECROPSY FIN DINGS:

Infectious Lecture 4th Year 3-1-2017 Dr.Osamah Muwafk

1. Lesions are usually confined to the skin, subcutaneous

tissues, and lymph vessels and nodes

DIFFER ENTIAL DIAGNOSIS:

2. Glanders (Burkholderia mallei)
3. Ulcerative lymphangitis (Corynbacterium

pseudotuberculosis)

4. Sporotrichosis (Sporothrix schenckil)
5. Histoplasmosis (Histoplasma capsulatum)

TREATM ENT:

6. Sodium iodide is administered as a 10% solution at a dose of

1 mL per 5 kg intravenously once weekly for 4 weeks

7. Or Amphotericin is administered at a dose of 0.2 mg/kg body

weight every 48 hours for 3 treatments

STRANGLES (EQUINE DISTEM PER)

ETIOLOGY

1. Streptococcus equi subsp. equi (S. equi)
2. is a Gram-positive coccobacillus

EPIDEMIOLOGY

1. Strangles occurs in horses, donkeys, and mules worldwide.
2. Outbreaks are seen in breeding farms and in polo and racing

stables, when the infection is introduced by new arrivals

3. Strangles can affect horses of any age
4. although morbidity rate is usually greater in younger horses

such as foals and weanlings

5. The case-fatality rate without treatment is about 9%

Infectious Lecture 4th Year 3-1-2017 Dr.Osamah Muwafk

6. Transmission from infected horses, either directly or by

fomites

Importance:

1. Strangles is one of the most important diseases of horses in

developed countries,

2. because of the deaths
3. because of the disruption of the management of commercial

horse establishments

4. the time necessary to treat affected horses

PATHOGENESIS:

1. M proteins are associated with S. equi adhesion to oral, nasal,

and pharyngeal tissues

2. Bacteria lodge in the pharyngeal and tonsillar lymphoid

tissues where they multiply rapidly

3. Bacteremia may occur
4. Swelling and abscessation of these lymph nods due to

migration of neutrophils into these lymph nodes

5. Death is usually due to pneumonia caused by aspiration of

infected material or asphyxiation secondary to upper airway
swelling

6. Metastatic infection of the heart valves, brain, eyes, joints,

and tendon sheaths or other vital organs may occur and cause
a chronic illness and eventual death

CLINICAL FINDINGS:

C. Acute disease

1. After an incubation period of 1-3 weeks

Infectious Lecture 4th Year 3-1-2017 Dr.Osamah Muwafk

2. Suddenly develops with complete anorexia, epression,

fever (39.5-40.soC, 103-105°F)

3. mucopurulent nasal discharge
4. Abscessation of submandibular and retropharyngeal

lymph nodes

5. severe pharyngitis and laryngitis
6. Lymphadenopathy becomes apparent as the

submandibular lymph nodes enlarge and palpation
elicits a painful response

7. Swelled lymph nod may rupture to discharge thick,

cream-yellow pus

8. Swelling of the retropharyngeal lymph nodes may

cause obstruction of the oro- and nasopharynx with
subsequent respiratory distress and dysphagia

9. Purpura hemorrhagica can occur as a sequela to S.

equi infection

CLINICAL PATHOLOGY

1.  Leukocytosis with a neutrophilia
2.  Hyperfibrinogenemia
3.  Hyperproteinemia

DIFFERENTIAL DIAGNOSIS:

Causes of pneumonia as in the table :

Infectious Lecture 4th Year 3-1-2017 Dr.Osamah Muwafk

TREATMENT

1. Treatment for S. equi infection depends on the stage of the

disease

2.  The specific treatment of choice is penicillin
3.  procaine penicillin G (22000 IV/kg IM every 12 h)
4.  or potassium or sodium penicillin G(22000 IU/kg IV every 6

5. or Tetracycline (6.6 mg/kg IV every 12-24 h)
6. or sulfonamide-trimethoprim combinations (15-30 mg/kg

orally or intravenously every12 h)

Infectious Lecture 4th Year 3-1-2017 Dr.Osamah Muwafk

7. administration of nonsteroidal anti-inflammatory drugs

(NSAIDs) to reduce swelling and provide pain relief

8. application of hot poultices to encourage rupture of abscesses
9. provision of intravenous hydration in animals unable to drink

10. wound care

U LCERATIVE LYMPHANGITIS OF HORSES

ETIOLOGY:

1. Corynebacterium pseudotuberculosis causes the classical

disease

2. It is a soil-borne organism that gains access to tissue through

wounds or insect bites

3. Transmission by direct contact between infected and

uninfected animals

4. by mechanical transmission by houseflies or other diptera

PATHOGENESIS

1.  Infection of skin wounds
2.  Invasion of lymphatic vessels
3.  Development of abscesses along their course
4.  Generalized lymph node involve mentis unusual
5.  The organism possesses a cytotoxic surface lipid coat that

appears to facilitate intracellular survival and abscess
formation

6. Produces a phospholipase exotoxin that increases vascular

permeability and has an inhibitory effect on phagocytes

Infectious Lecture 4th Year 3-1-2017 Dr.Osamah Muwafk

CLINICAL FINDINGS:

1. Initial wound infection
2. Swelling and pain of the pastern, often sufficient to

cause severe lameness

3. Nodules develop in the subcutaneous tissue,

particularly around the fetlock

4. Infection of lymphatic vessels and the development of

abscesses along their course

5. Spread to other subcutaneous sites on all parts of the

body

6. These may enlarge to 5-7 cm in diameter and rupture

to discharge a creamy green pus

7. The resulting ulcer has ragged edges and a necrotic

base

8. Lymphatics draining the area become enlarged and

hard and secondary ulcers may develop along them

9. Lesions heal in 1-2 weeks

10. Fresh crops may occur and cause persistence of the

disease for up to 12 months

DIFFERENTIAL DIAGNOSIS:

1.  Epizootic lymphangitis
2.  Glanders
3.  Sporotrichosis
4.  Rhodococcus equi

TREATMENT:

1. Aminoglycoside group
2. but systemic treatment of infected animals does not affect the

recovery period

Infectious Lecture 4th Year 3-1-2017 Dr.Osamah Muwafk

3. Local treatment of ulcers is the usual and most effective

procedure