92. Equine infectious anaemia.

Question 1

Occurrence?

Answer 1

Occurrence

• Worldwide, frequency different
• Wet area (swamp fever)
• River valleys

Question 2

Etiology?

Answer 2

Etiology

• Lentivirus genus
• Antigens
• p26 group specific, diagnostics
• p90 binding, variability
• Can be cultured
• Relative good resistance
• Dried 7 months
• pH 3-12 stabile
• Disinfectants

• Horse, mule, donkey, zebra

Question 3

Epidemiology?

Answer 3

Epidemiology

• Source of infection: blood of diseased animals
• Transmission: arthropod, iatrogenic
• Maintaining infection
• Infected animals
• Persistent infection, lifelong carriage
• Shed in discharge (no major epidemiological role)
• Introduction with infected animals
• Arthropods
• Horsefly, deer fly, other blood sucking flies (mosquito)
• Mechanical vector
• Depends on phase of pathogenesis in horse (viraemia)
• Transmission within short distance
• Painful puncture, horse driven away

• Infects foetus (rare)

- Abortion

• Infected foal will be born

Question 4

Pathogenesis?

Answer 4

Pathogenesis

1. Infection: arthropods
2. Viraemia
   - Monocytes, macrophages, lymphoreticular tissues
   - Liver, spleen, bone marrow, lymph nodes
3. Anaemia
   - Damage of bone marrow
   - Haemagglutination by virus, immune complexes ➝ haemolysis
   - Macrophages phagocyte red blood cells
4. Immune reaction
   - Virus titre decreased, carriage
   - New variant, new wave
5. Number of lymphocytes decreased, immune suppression
6. Immune response: 3-6 weeks

Question 5

Clinical signs?

Answer 5

Clinical signs

• Incubation: 1-4 weeks (maximum 3 months)
• Acute
• 41-42℃ fever, depression, tottering, weakness, tiredness
• Abortion
• Mucous membranes: blood stasis, haemorrhages (sublingual)
• Oedema
• Death or becomes asymptomatic after 3-5 days

• Subacute, chronic

• 1-3 months (6-12 months) after febrile waves
• Weight loss, weakness, decreased performance
• Oedema, anaemia

• Asymptomatic

Question 6

Pathology?

Answer 6

Pathology

• Acute

• Haemorrhages under serous membranes
• Oedema
• Spleen hyperaemic, liver dystrophy, flaccid heart
• Enlarged lymph nodes

• Subacute

• Spleen: slightly enlarged, purple-red, granular
• Liver: enlarged, nutmeg pattern
• Kidney: glomerulonephritis

Question 7

Diagnosis?

Answer 7

Diagnosis

• Epidemiology, clinical signs, pathology, histology
• Clinical laboratory examinations
• Anaemia
• Thrombocytopenia
• Hypergammaglobulinemia
• Increased activity of liver enzymes
• Antibody detection ➝ p26, AGP (Coggins test): official, ELISA, immune blot
• Agent detection
• Virus detection ➝ PCR
• Virus isolation

Question 8

Prevention and control?

Answer 8

Prevention, Control

• No treatment, incurable
• Notifiable
• Diseased animals: killing
• Suspected animals

‣ Isolation, movement restriction

‣ Repeated diagnostic examinations

• Regular serological examination ➝ yearly in sport horses, every 3 years for other horses
• Prevention of iatrogenic infections, insect control
• Control of import
• No vaccine