Infectious Lecture 4th Year 6-12-2016 Dr.Osamah Muwafk
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WINTER DYSENTERY IN CATTLE
Etiology and epidemiology:
1. Bovine coronavius (BCV) which is a member of family
Coronaviridae, order Nidovirales
2. occurs primarily in mature dairy cattle
3. has been reported in many countries
4. The morbidity rate may be as high as 30-50%
5. The case-fatality rate is less than 1 %.
6. Feces from clinical cases or clinically normal carriers are the
source of infection
7. contamination of feed or drinking water is the method of
spread
PATHOGENESIS
1. The disease is a mild enteritis affecting the small intestine.
2. The virus also has a tropism for the respiratory tract and has
been associated with respiratory disease in adult cattle and
pneumonia in calves.
CLINICAL FINDINGS
1. incubation period 3-7 d
2. explosive outbreak of diarrhea.
3. A fever (39.5-40.ºC)
4. marked fall in milk yield
5. The feces are liquid and homogeneous without much odor,
and with no mucous or epithelial shreds; the color is dark
green to almost black
6. In most animals the course is short and the feces return to
normal consistency in 2-3 d.
Infectious Lecture 4th Year 6-12-2016 Dr.Osamah Muwafk
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CLINICAL PATHOLOGY
1. The laboratory diagnosis is dependent on detection of the
virus in feces and serology.
DIFFERENTIAL DIAGNOSIS
2. BVD/MD
3. Coccidiosis
4. Enteric salmonellosis
5. Johne's disease
6. Respiratory tract infections
TREATMENT
1. affected cattle usually respond spontaneously in 24-36 h.
2. Occasionally dehydration will become severe and is best
treated with fluids and balanced electrolytes as indicated.
Diseases associated with Moraxella and Haemophilus species
INFECTIOUS KERATITIS OF CATTLE (PINKEYE, BLIGHT)
Etiology and Epidemiology
1. Moraxella bovis is the primary infectious agent.
2. Pili and hemolysin are the main virulence factors.
3. Solar radiation, flies, and dust have been shown to have an
enhancing effect
4. Cattle of all ages are susceptible.
5. Carrier cattle is the Source of infection
6. transmission by mediate contagion and by flies.
7. More common in summer and autumn months.
8. Usually multiple cases in a herd
Infectious Lecture 4th Year 6-12-2016 Dr.Osamah Muwafk
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PATHOGENESIS
1. Attachment of M. bovis to the corneal epithelium is mediated
by the presence of pilus antigens
2. corneal erosions
3. focal loss of corneal epithelium
4. degeneration of keratocytes
5. invasion of the corneal stroma with fibrillary destruction
6. An inflammatory reaction occurs several days postinfection
Clinical findings:
1. An incubation period of 2-3 days
2. Injection of the corneal vessels and edema of the conjunctiva
are the early signs
3. One or both eyes may be affected
4. Conjunctivitis
5. lacrimation
6. blepharospasm
7. photophobia
8. central corneal opacity
9. complete recovery occurring after a total course of 3-5 weeks
Diagnostic confirmation:
- Culture
DIFFERENTIAL DIAGNOSIS
1. Traumatic conjunctivitis
2. Pasteurella multocida
3. mycoplasma bovis
4. Listeria monocytogenes iritis
5. Infectious bovine rhinotracheitis
Infectious Lecture 4th Year 6-12-2016 Dr.Osamah Muwafk
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6. Bovine malignant catarrh
7. Thelaziasis
8. Chlamydial keratoconjunctivitis
Treatment:
1. Self-limiting disease
2. Topical antibiotics
The administration of an oil based formulation containing
375 mg of benzathine cloxacillin has been found to be
effective in therapy
3. Sub conjunctival penicillin,
4. parenteral oxytetracyclines
5. Protection of eye from sunlight
6. Fly control
HAEMOPHILUS SEPTICEMIA OF CATTLE (HISTOPHILUS
SOMNI OR HAEMOPHILUS SOMNUS DISEASE COMPLEX)
Etiology and Epidemiology
1. Histophilus somni (formerly Haemophilus somnus)
2. High prevalence of infection in cattle population
3. Young growing cattle and those 6-1 2 months of age are
4. most commonly affected, nursing beef calves less commonly.
5. meningoencephalitis
was
most
common
lesion
but
pleuropneumonia and myocarditis now common.
6. Several virulence attributes of organism may account for
different forms of disease.
7. Organism resides in respiratory and reproductive tract of both
females and males
Infectious Lecture 4th Year 6-12-2016 Dr.Osamah Muwafk
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PATHOGENESIS
1. H. somni first establishes it self in the host by colonizing the
surface of the mucous membranes
2. Some strains of the organism are able to invade the
circulatory system and cause septicemia
3. localization in many tissues and organs, causing a vasculitis
4. Multifocal areas of hemorrhagic necrosis occur throughout
the brain
5. Localization in synovia results in polysynovitis
CLINICAL FINDINGS
1. The
typical
nervous
form
of
the
disease
are
Meningoencephalitis
2. Some affected animals may be found dead
3. cattle may be found in lateral or sternal recumbency and may
or
4. may not be able to stand
5. The temperature is usually increased up to 41-42°C
6. the disease was called the 'sleeper syndrome' because the
eyes were partially closed
7. rapidly fatal in 8-12 hours if not treated
8. The ocular lesions consist of foci of retinal hemorrhages and
accumulations of exudate that appear like 'cotton tufts
9. Otitis in feedlot cattle has also been attributed to the
organism
10.
The synovitis is characterized by distension of the joint
capsules
11.
Laryngitis, tracheitis, pleuritis, and pneumonia can
occur alone or in combination with the acute neurological
form of the disease
Infectious Lecture 4th Year 6-12-2016 Dr.Osamah Muwafk
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12.
In the myocardial form of the disease, affected animals
may be found dead without any previous illness
NECROPSY FINDINGS
1. The characteristic lesions of the nervous form are
hemorrhagic infarcts in any part of the brain and spinal cord.
2. These are usually multiple and vary in color from bright red
to brown and in diameter from 0.5-3 cm.
3. There may be petechiation and edema of the synovial
membranes of joints
DIFFERENTIAL DIAGNOSIS
1. Polioencephalomalacia
2. Listeria meningoencephalitis
3. Hypovitaminosis A
4. Pneumonia and pleuritis