LOUPING ILL

~Also called infectious encophalomyelitis of sheep

~occurs in Scottland,England, Ireland, Czechoslovakia, and Soviet

Union

~it similar to spring-summer encephalitis, which afflicts man

Name~ from peculiar leaping gait of ataxic animals

~inocuble by intracerebral injection

Sheep ~ primarily infected (cattle, swine, dog, horses can be affected

also)

Clinical Signs ~ nervous signs and died of severe

meningocephalomyelitis

~ isolation of the virus is through the brain

Antibodies ~ found in wild red deer (tangential host)

Character of the disease

6-18 days ~incubation time in sheep

Signs ~ dullness and high temperature (107oF or more)

-virus present in the blood

Character of the disease

~improvement is temporary and nervous system may involved

Nervous signs ~ muscular incoordination, tremors, cerebellar

ataxia, and paralysis

Character of the disease

Acute cases ~ death occurs

Chronic cases ~ paralysis

Human poliomyelitis ~ disease resembles and begins as a

generalized infection

Character of the disease

Acute cases ~ death occurs

Chronic cases ~ paralysis

Human poliomyelitis ~ disease resembles and begins as a

generalized infection

Character of the disease

Virus isolation ~ brain, cervical spinal cord

~ serum samples from horses contain hemagglutinating,

complement-fixing, precipitating, and neutralizing antibodies

Character of the disease

Microscopic lesions ~ typical viral encephalomyelitis and meningitis

~can have degeneration of neurons (Pukinje cells)

~no typical gross lesions

Character of the disease

Intracerebral inoculation of brain virus ~ produce in sheep, cattle, swine, mice,

hamster, and monkeys

Rabbits and guinea pig – resistant

Monkeys and mice – can be readily infected by instilling the virus in their nostrils

Character of the disease

Deer = had viremia and produce antibodies

Horses = susceptible to the disease and have viremia (cause:nymphs of

castor bean tick Ixodes ricinus)

Properties of the virus

~has properties of a flavivirus with infectious RNA (spherical)

Hemagluttination-inhibition test ~ crossing occurs with other flavivirus

Freezing and glycerol – agent is preserved

Properties of the virus

Saline and broth ~ the virus deteriorates (dilute and acid

suspensions)

Complement fixation test ~ antibodies are transient; limited value in diagnosis

Cultivation

Minced chick medium, cultures of pig kidney, and embryonated eggs = used

in obtaining artificial culture

Epizootiology

Monkeys and humans ~ Contract infection by inhaling infective droplets

Sheep ~ bloodsucking arthropods (transmission)

Principal transmitter~ Ixodes ricinus

Epizootiology

Larval tick ~ feeding on sheep

Early summer ~ prevalent period

Midsummer ~ subsides

Early fall ~ reappears

*based on tick activity

Epizootiology

Maintenance of the disease ~ based on sheep (amplifier host)

Immunity

Natural / artificial injection ~ results in solid, enduring immunity

Vaccine consists of formalinized nerve tissue ~ effective protection for young

lambs

Diagnosis

Clinical signs ~ difficult to distinguish

~inoculating and intracerebrally with nerve tissue

serological test ~ to make a definitive diagnosis

Prevention and Control

1.By immunizing all newborn lambs of nerve tissue vaccines shortly after

weaning

2.Remove all castor bean ticks in flocks

3. Injecting of vaccines

Prevention and Control

Toxoplasma gondii ~ infection in sheep will suppress immunizing effect of a

single injection of virus vaccine

Disease in Human

~ occurred in 3 laboratory workers

~ illness was influenzal in nature

~ Virus was not recovered in patients, but neutralizing agents appeared in

their serums

Disease in Human

~ Shepherds in infected flocks can be affected

~ the disease is diphasic (febrile illness of short duration)

~ become delirious and was comatose

Disease in Human

~virus was isolated by inoculation of mice (intracerebrally and

intramuscularly) with cerbrospinal fluid

~ neutralizing antibodies appears on the blood.

Disease in Human

~ recovered almost but with mild symptoms of ataxia

LOUPING ILL