Malignant Catarrhal Fever Flashcards
(29 cards)
what type of disease is MCF, and what causes it? where is it a problem? fatality?
MCF is a severe lympho- proliferative disease caused by a group of herpesviruses collectively referred to as malignant catarrhal fever viruses.
Highly fatal disease of: Cattle, deer, bison, buffalo, and other ruminants
Major problem in zoos
how many viruses in the MCF group? How many associated with clinical disease?
Ten genetically and antigenically related viruses have been identified and constitute the group of MCF viruses.
Six of these viruses are associated with clinical disease, and the remaining four viruses have not yet been associated with disease
**previousy the most important type of MCF, outside Africa, in cattle? what about in africa
- Outside Africa: Ovine herpesvirus type 2
> now called ovine gammaherpesvirus 2 - In Africa: Wildebeest
> Alcelaphine gammaherpesvirus 1 (prev. alcephine herpesvirus type 1)
African MCF strain? what is a related one?
Alcelaphine herpesvirus type 1 (wildebeest-associated γ- herpesvirus)
Not imortant probably:
Alcelaphine herpesvirus type 2 is a closely related γ- herpesvirus from other species of African antelope (Hartebeest).
Sheep-associated form of MCF, and its relative:
(Syn: “American MCF”, “European MCF”) Ovine HerpesVirus-2 (OHV-2)
NOT yet isolated by conventional virology Antigenically related to AlHV-1
epidemiology of African MCF? where can this virus be isolated from?
Wildebeest → cattle and other susceptible species (calving season)
- AHV-1 isolated from: asymptomatic wildebeests, from nasal and lacrimal secretions of wildebeest calves and fetus.
Geographic Distribution of AHV-1 and OHV-2 ? carried by what?
AHV-1 primarily in Africa
Carried by wildebeest, hartebeest, topi
Also in zoologic and wild animal parks
OHV-2 worldwide
Carried by domestic and wild sheep and goats
Positive bison have been found in U.S. and Canada
> often misdiagnosed in bison
animal transmission of AHV-1 (cell-associated)
- how does it spread? by what animals?
Rarely transmitted
Stress induces shedding cell-free virus
> Nasal secretions via aerosol
> Contaminate feed, water
> Arthropods
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Neonatal wildebeests 4 days to 4 months
> Shed in lacrimal, nasal secretions, feces
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Same species horizontal transmission is rare (i.e. cow-to-cow)
> Dead end hosts
MCF “Wildebeest-derived” Form
- outbreaks morbidity, mortality?
Outbreaks of WD-MCF occur in Africa
7% morbidity; up to 100% mortality
Outbreaks of WD-MCF have occurred in Oklahoma City
and San Diego zoos
Threat to the North American cattle industry?
OHV-2 transmission? what animals and how?
All ages of sheep infectious
Spread to cattle during lambing
Lambs infected by 4 months
Goat spread unknown
MCF Sheep-associated” form
- outbreaks? mortality?
Usually sporadic cases
Outbreaks of MCF are rare
High mortality rate (90-95%)
MCF incubation period, pathophysiology
Incubation 3-10 weeks (but as long as 150 days)
Lymphoid hyperplasia
> Atypical proliferation of sinusoidal cells
> Cerebro-meningeal changes due to vasculitis (encephalitis)
Widespread vascular epithelial and mesothelial lesions
> Morphologically associated with lymphoid cells
Synovitis (tibio-tarsal join)
> lymphoid vasculitis
MCF clinical signs for peracute, acute, and mild forms
Peracute to mild form: wide variety of clinical signs
Peracute:
> 1-3 days. Fever, dyspnea, and acute gastroenteritis,
> Some cases no signs are seen (acute deaths)
Acute:
> 3-7 days, high mortality rate
Mild form:
> mild fever, mild erosions on oral and nasal mucosae, persistent bilateral ocular leukomata (white eye)
MCF clinical pathology - WBC changes, joint fluid, CSF
Leukopenia due to neutropenia (inconsistent)
Leukocytosis occur in later stages
Joint fluid: Cloudy, increased protein and mononuclear cells
CSF: increased protein and WBC count mainly due to mononuclear cells
MCF diagnosis
History of exposure
Clinical signs
Gross and histological lesions
Virus isolation (nasal swabs, blood, spleen, lymph nodes). Do not freeze them.
Cytopathic effect on thyroid cell cultures (4-20 days post infections)
Laboratory Tests
> Histopathology
> PCR (blood or tissue)
> Serology (IF)
can we isolate MCF virus?
Virus isolation: not practical
Instability of cell-associated AHV-1
OHV-2 does not replicate in cell culture
clin path and serology tests for MCF? whiich are useful?
Virus isolation: not practical
Instability of cell-associated AHV-1
OHV-2 does not replicate in cell culture
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Virus neutralization
Serologic test:
AHV-1 antibodies in wildebeest
Immunofluorescence in ruminants
OHV-2 antibodies in sheep, cattle using IF
CI-ELISA for screening
ELISA, complement fixation, virus neutralization
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PCR
MCF necropsy findings
Nasal mucosa: hyperemic to hemorrhagic
Oral mucosa: necrotic papilla, large areas of necrosis and ulceration
Esophagus: Focal ulceration
Forestomachs and intestines:
> Thickened, edematous, ulceration and hemorrhage
Lymphadenopathy
MCF Prevention and Control
Separate infected and carrier animals from susceptible species
> Sheep and goats are carriers
Avoid exposing cattle, bison, deer during
parturition
Zoological parks:
> Introduce seronegative animals only
No vaccine available
MCF in humans and human transmission?
MCF has not been documented as causing disease in humans
Caution at lambing time
> Equipment used could spread infection to susceptible animals
Virus quickly inactivated by sunlight
> Minimizes risk of fomite spread
Hemorrhagic Bowel Syndrome - occurence? incidence and mortality?
Sporadic in occurrence
A typical case incidence rate is 2-3%, with some farms experiencing an outbreak form
Mortality may approach 85-100% of cases due to peracute nature
HBS - Hemorrhagic Bowel Syndrome other names? etiology?
JHS: Jejunal hemorrage syndrome
BBS: Bloody bowel syndrome
Etiology (still in debate):
> Cl. perfringens
> Mycotoxins
Clinical Signs of “HBS”? incubation?
Short incubation period – hours rather than days
Severe sweats
Bruxism (teeth grinding)
Sternal recumbency
Lethargy (extreme depression)
Enophthalmia (sunken eyes)
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Slight bloating may be evident
Pale mucous membranes
Fluid “slosh” in lower right abdomen
Distended gut loops per rectal palpation
SUDDEN DEATH
HBS post mortem findings
Severe segmental small intestinal inflammation
Segmental hemorrhaging and clotting forming a functional plug
> Necrosis +/-
> Impaction
