Malignant Catarrhal Fever

Question 1

what type of disease is MCF, and what causes it? where is it a problem? fatality?

Answer 1

 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

Question 2

how many viruses in the MCF group? How many associated with clinical disease?

Answer 2

 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

Question 3

**previousy the most important type of MCF, outside Africa, in cattle? what about in africa

Answer 3

• Outside Africa: Ovine herpesvirus type 2
  > now called ovine gammaherpesvirus 2
• In Africa: Wildebeest
  > Alcelaphine gammaherpesvirus 1 (prev. alcephine herpesvirus type 1)

Question 4

African MCF strain? what is a related one?

Answer 4

 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).

Question 5

Sheep-associated form of MCF, and its relative:

Answer 5

 (Syn: “American MCF”, “European MCF”) Ovine HerpesVirus-2 (OHV-2)
NOT yet isolated by conventional virology Antigenically related to AlHV-1

Question 6

epidemiology of African MCF? where can this virus be isolated from?

Answer 6

Wildebeest → cattle and other susceptible species (calving season)

• AHV-1 isolated from: asymptomatic wildebeests, from nasal and lacrimal secretions of wildebeest calves and fetus.

Question 7

Geographic Distribution of AHV-1 and OHV-2 ? carried by what?

Answer 7

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

Question 8

animal transmission of AHV-1 (cell-associated)
- how does it spread? by what animals?

Answer 8

 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

Question 9

MCF “Wildebeest-derived” Form
- outbreaks morbidity, mortality?

Answer 9

 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?

Question 10

OHV-2 transmission? what animals and how?

Answer 10

 All ages of sheep infectious
 Spread to cattle during lambing
 Lambs infected by 4 months
 Goat spread unknown

Question 11

MCF Sheep-associated” form
- outbreaks? mortality?

Answer 11

 Usually sporadic cases
 Outbreaks of MCF are rare
 High mortality rate (90-95%)

Question 12

MCF incubation period, pathophysiology

Answer 12

 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

Question 13

MCF clinical signs for peracute, acute, and mild forms

Answer 13

 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)

Question 14

MCF clinical pathology - WBC changes, joint fluid, CSF

Answer 14

 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

Question 15

MCF diagnosis

Answer 15

 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)

Question 16

can we isolate MCF virus?

Answer 16

Virus isolation: not practical
 Instability of cell-associated AHV-1
 OHV-2 does not replicate in cell culture

Question 17

clin path and serology tests for MCF? whiich are useful?

Answer 17

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

Question 18

MCF necropsy findings

Answer 18

 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

Question 19

MCF Prevention and Control

Answer 19

 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

Question 20

MCF in humans and human transmission?

Answer 20

 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

Question 21

Hemorrhagic Bowel Syndrome - occurence? incidence and mortality?

Answer 21

 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

Question 22

HBS - Hemorrhagic Bowel Syndrome other names? etiology?

Answer 22

 JHS: Jejunal hemorrage syndrome
 BBS: Bloody bowel syndrome
 Etiology (still in debate):
> Cl. perfringens
> Mycotoxins

Question 23

Clinical Signs of “HBS”? incubation?

Answer 23

 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

Question 24

HBS post mortem findings

Answer 24

 Severe segmental small intestinal inflammation
 Segmental hemorrhaging and clotting forming a functional plug
> Necrosis +/-
> Impaction

Question 25

HBS diagnosis?

Answer 25

 Surgery or PM:
> Appearance of characteristic lesions and clinical signs
 Isolation of Clostridium perfringens type A from the lesion site in high numbers. Overgrowth occurs fast.
 Fecal culture?

Question 26

HBS treatments? prognosis? treatment success rate?

Answer 26

 Prognosis is extremely poor
* Surgical intervention
 Some areas of segmental clots may be massaged out to resolve the case
 Intestinal resection & anastamosis is usually required to remove affected tissue
Success Rate ~ 5-10%

Question 27

rinderpast organism

Answer 27

 Family Paramyxoviridae
 Genus Morbillivirus
 Other members of the family include
 Peste des Petits Ruminants virus
 Measles virus
 Canine distemper virus
 Phocid distemper virus of sea mammals
 Relatively fragile virus

Question 28

rinderspest economic impact

Answer 28

 Destroys entire populations of cattle
 Leads to famine in cattle-dependent areas
 1982-1984 outbreak: $500 million
 $100 million spent annually on vaccination

Question 29

Rinderpest Eradication Massive Vaccination Program

Answer 29

basically eliminated disease (in middle east, north africa where it was found) from 1980-2007