80. Rift Valley fever and Nairobi sheep disease.

Question 1

Rift Valley Fever & Nairobi Sheep Disease: Virus family

Answer 1

Bunyaviridae

Question 2

Rift Valley Fever: Summary

Answer 2

• Rift Valley Fever Virus (RVFV)
• RNA Virus
• Vector: Mosquito; Sandfly

Question 3

Rift Valley Fever: Epizootiology

Answer 3

ZOONOTIC DISEASE

• Endemic in tropical Africa; Outbreaks in 5-20 year cycles
• Long intervals between outbreaks - Developement of a susceptible animal population
• Other locations: Saudi Arabia & Yemen

Question 4

Rift Valley Fever: Vertebrate host

Answer 4

Ru.; Ho.

Question 5

Rift Valley Fever: Transmission

Answer 5

• Vector
• Non-vectorial:
  
  • Direct/Airborne
  • Tissues & body fluids
  • Aborted foetuses
  • Slaughtering & dissections

Question 6

Rift Valley Fever: Susceptibility

Answer 6

• 100% Mortality: Ru.; Puppies; Kittens
• Severe disease, abortion & death: Ov.; Bo.; Cap.; Ho.
• Severe disease & Abortion: Monkey; camel; rat; squirrel
• Infection & viraemia: Eq.; Ca.; Fe.; monkey
• Resistant: Rabbit, Sus.; Av.

Question 7

Rift Valley Fever: CSx (Ov. & Cap.)

Answer 7

• Subclinical infection
• 5-100% abortion rate
• Sudden death
• Diarrhoea; icterus; mucopurulent nasal discharge
• Young:
  
  • Fever; depression; anorexia
  • Death in 2 days; <1week old (90% lethality)

Question 8

Rift Valley Fever: CSx (Bo.)

Answer 8

• Fever, weakness, anorexia, salivation, diarrhoea, icterus
• Abortion
• Calf: High lethality

Question 9

Rift Valley Fever: CSx (Ho.)

Answer 9

1% mortality

• Sub-clinical/influenza-like disease
• Retinopathy
• Haemorrhagic fever
• Encephalitis

Question 10

Rift Valley Fever: Pathology

Answer 10

• Necrotic hepatitis; Enlarged, yellow fragile liver
• Petechiae on viscera & mucosa
• Haemorrhagic enteritis in the L. intestine

Question 11

Rift Valley Fever: Dx

Answer 11

• Virus isolation; RT-PCR
• Serology: ELISA

Question 12

Rift Valley Fever: Tx (Ho.)

Answer 12

• Symptomatic & supportive therapy
• Providing coagulation factors
• Ribavirin: Possible positive effect

Question 13

Rift Valley Fever: Prevention & control

Answer 13

• Inactivated vaccination of susceptible Ru. → Annual booster
• Maternal Ig detection
• Arthropod control; PPE
• Quarantine; Serological investigation

Question 14

Nairobi Sheep disease: Virus Familiy

Answer 14

Bunyaviridae

Question 15

Nairobi Sheep disease: Epizootiology

Answer 15

ZOONOTIC DISEASE

• Middle & East Africa
• Affecting Ov.

“You will fail if you don’t know this disease in the exam!”

Question 16

Nairobi Sheep disease: Transmission

Answer 16

Tick-borne transmission

Ticks can carry the virus for years

Question 17

Nairobi Sheep disease: Incubation & CSx

Answer 17

4-15 day incubation period

• Fever; Dyspnoea; Depression; Nasal discharge; Enteritis
• Abortion; Oedema of the genital organs
• Shock; Death (70-90%)

Question 18

Nairobi Sheep Disease: Pathology

Answer 18

• Haemorrhagic gastroenteritis; Haemorrhages in the heart
• Hepatomegaly; Nephromegally; Splenomegaly
• Full gall bladder; Hyperaemic genital organs

Question 19

Nairobi Sheep disease: Dx

Answer 19

• Occurance; Epizootiology
• CSx & Pathology
• Direct virus detection: Isolation; IF; AGID (Agar-gel immunodiffusion)
• Indirect virus detection: VN

Question 20

Nairobi Sheep Disease: Prevention

Answer 20

• Tick control
• Vaccination in endemic areas
• Attenuated, residual virulence; Reversion risk

Question 21

Nairobi Sheep Disease: CSx (Ho.)

Answer 21

• Mild fever
• General symptoms