51. Louping ill and tick-borne encephalitis (Zoon.).

Question 1

Background virus info?

Answer 1

• Enveloped, icosahedral symmetry, +ssRNA viruses
• Flavivirus, Pestivirus (most resistant) and Hepacivirus genus
• Flavivirus genus
• More than 53 sp., most of them are exotic
• Tick-transmitted/mosquito-transmitted/non-arbovirus groups ʹ biological vectors, possible nonvectorial transmission (air-borne, PO)
• Weak resistance (65oC 30oC detergents disinfectants)
• Euryxen, MANY ZOONOTIC
• Fever & rash ʹ encephalitis/meningitis ʹ haemorrhage
• Antigenicity
• Strong antigens
• Serological cross reactions!
• Sometimes cross protection
• Lifelong IMMUNITY

Question 2

Tick Borne encephalitis Occurrence and Epidemiology?

Answer 2

Tick-borne encephalitis

• ZOONOTIC
• A human febrile illness with meningio-encepahlomyelitis in certain cases, animals usually asymptomatic

Occurrence:

• Central-European & Far-Eastern lineages,
• Endemic in Central Europe
• focal infections

Epidemiology

• Principle vector: Ixodes ricinus (Siberia: Ixodes persulcatus)
• Biological vector, transovarial transmission
• Susceptibility: human, domesticated & wild mammals, birds
• Natural cycle: rodents, small mammals, (birds) ʹ ticks
• Infection of humans, domesticated animals
• Tick bite ʹ seasonal
• Consumption of raw milk (goat!)

Question 3

Pathogenesis and Clinical signs of Louping ill?

Answer 3

Pathogenesis:

• Bite/PO
• local multiplication
• viraemia
• visceral organs(CNS)

Clinical signs:

• Incubation: 1- 2 weeks
• In animals usually, in humans frequently subclinical infections
• 1st fever + influenza-like disease
• 7-10 days after: 2nd fever, CNS signs
• Headache, restlessness, neck stiffness, weak limbs, paralysis
• Usually complete recovery, but permanent lesions may also remain
• Rarely in foals, dogs, goat clinical signs occur: depression, ataxia, convulsions, tremor

Question 4

Tick Borne encephalitis diagnosis, differential diagnosis and prevention, control?

Answer 4

Diagnosis

• Direct: isolation (suckling mouse brain), RT-PCR, HA
• Indirect: IF, ELISA, HAI, VN (PRNT)

Differential diagnosis:

1. entero-,
2. toga-,
3. flavi-,
4. herpesviruses,
5. bacterial meningitis

Prevention, control

• Prevention from tick-bite
• Inactivated vaccine (2x + 1x + in 3-4 years)

Question 5

Louping ill Occurrence and epizootiology?

Answer 5

Louping ill

• Zoonotic
• Febrile illness with meningo-encephalomyelitis in SHEEP & rarely in other animals

Occurrence:

• British-isles,
• Scandinavia

Epizootiology

• Principle vector: Ixodes ricinus
• seasonal outbreaks
• Susceptibility: sheep, domesticated & wild mammals, humans

Question 6

Clinical signs and histopathology of louping ill?

Answer 6

Clinical signs

• Incubation: 1- 3 weeks: biphasic fever
• Depression, salivation, trembling, convulsions, ticks
• Virus shed in milk: infects young!
• Ataxia (louping ill), coma, death
• Frequent permanent lesions after recovery

Histopathology:

• lymphocytic encephalitis,
• neuron necrosis,
• glia-proliferation

Question 7

Diagnosis and differential diagnosis of tick borne encephalitis?

Answer 7

Diagnosis

• Epizootiology, case history, clinical signs, histopathology
• Isolation, RT-PCR
• Serology: HAI, VN, ELISA

Differential diagnosis

1. Listeriosis: histopathology, bacteriology tests
2. Rabies: occurrence, course, laboratory
3. Scrapie: occurrence, course, no fever, laboratory

Question 8

Prevention and public health considerations of louping ill?

Answer 8

Prevention:

• inactivated vaccine is available in endemic countries

Public health considerations

• Human infection is rare
• Tick-bite, air-borne, PO
• Fever, meningoencephalitis