179. Canine ehrlichiosis, disease of horses and cattle caused by Anaplasma phagocytophilum, Potomac horse fever. Flashcards
Canine ehrlichosis aetiology and occurrence?
Canine ehrlichiosis
- E. canis: canine monocytic ehrlichiosis
- Occurrence: Mediterranean countries; warm climate: Africa, Middle-East, South East Asia, USA
• Aetiology:
- E. canis, narrow host range (dogs)
Epidemiology and pathogenesis of Canine ehrlichosis?
Epidemiology
- Brown dog tick (Rhipicephalus sanguineus) – maintenance host
- Dogs carry for 1-2 years
- German Sheppard is most susceptible
Pathogenesis
- Infection (blood sucking by ticks, iatrogenic) → Septicaemia
- Damage of endothelial (haemorrhages, oedema) & lymphoid cells (immunosuppression) & BM
Clinical signs and Pathology of canine ehrlichosis?
Clinical signs
- Local dog breeds: some have protective immunity, persistent subclinical infection - shedding
- Imported animals: fever, anorexia, haemorrhages (oral and nasal cavity), oedema,
- lymphadenopathy, thrombocytopenia, leukopaenia, anaemia, vasculitis, nervous signs
Pathology:
- anaemia; haemorrhages on the MM;
- oedema (legs, belly);
- enlargement of LNs
Diagnosis, treatment and prevention of Canine ehrlichosis?
• Diagnosis
- Epidemiology – clinical signs – PM lesions
- Detection of the agent: staining, PCR, IF, isolation
- Detection of antibodies: iIF, ELISA, immunoblot
- Treatment: tetracyclines
- Prevention: repellents, removal of ticks, no vaccine
E. chaffensis?
E. chaffensis:
- human monocytic ehrlichiosis (dog, other)
- Human and canine monocytic ehrlichiosis
- Only fever and trombocytopenia in dogs
- Flu-like clinical signs in humans
E. ewingii?
E. ewingii:
- human and canine granulocytic ehrlichiosis
- Human and canine granulocytic ehrlichiosis
- Similar, but milder clinical signs than monocytic ehrlichiosis
Diseases caused by Anaplasma species?
Diseases caused by Anaplasma species
Species
- A. marginale (A. centrale): anaplasmosis of cattle
- A. ovis: anaplasmosis of small ruminants
- A. phagocytophilum: ruminants, horse (cause different diseases in different animals)
- A. bovis: similar to heartwater
- A. platys: dog oedema
Aetiology of anaplasma?
Aetiology
- Intra cellular (can replicate on the surface of RBCs)
- Replication
- Species replicating in lymphoid cells: A. phagocytophilum, A. bovis
▪ Culture: neutrophilic granulocytes, myeloid cells
• Species replicating in red blood cells: A. marginale, A. centrale, A. ovis
▪ Cannot be cultured
• Species replicating on thrombocytes: A. platys
Epidemiology?
Epidemiology
- Infection: blood sucking arthropods, iatrogen (surgery)
- Arthropods: true vectors – ticks (agent replicates), other blood sucking arthropods –
- mechanical transmission only
- Maintaining hosts: ticks – wild living ruminants (cycle); wild living ruminants can be asymptomatic
Pathogenesis of anaplasma species?
Pathogenesis
- Infection → septicaemia
- Haemopoietic cells, RBCs, lymphoid cells
- Replication in RBCs: macrophages phagocyte infected RBCs → anaemia
- Replication in lymphoid/endothelial cells: immunosuppression, haemorrhage, oedema
- Long carriage (after healing), poor immunity
- Can appear again
Diseases caused by A.Phagocytophilum?
Diseases caused by A. phagocytophilum
- Focal infection: small rodents, wild living animals; ticks vector
- Replication in endothelial and lymphoid cells
- Tick borne fever of ruminants (pasture fever)
Occurrence:
- Great Britain,
- Scandinavian countries,
- Central Europe
Aetiology:
- Anaplasma phagocytophilum (E. phagocytophila)
Epidemiology:
▪ Spring- early summer, pasture
▪ Vector: ticks (seasonality)
▪ Sheep, goat, cattle
▪ Immunosuppression, secondary infections
Pathogenesis,
- clinical signs: septicaemia, mild fever, depression, abortion, decreased milk
- production, long carriage
Diagnosis
- Epidemiology – clinical signs – laboratory examination
- Microscopic examination
Treatment, prevention:
- tetracyclines,
- tick control,
- no vaccines
Equine granulocytic anaplasmosis/ehrlichosis?
Equine granulocytic anaplasmosis/ehrlichiosis
- Occurrence: USA, Switzerland, Sweden, Great Britain, Israel
- Aetiology: Anaplasma phagocytophilum (E. equi)
- Epidemiology: vector - ticks (Ixodes pacificus); horse, dog, llama, rodents
- Pathogenesis:
- Replication in the vacuoles of granulocytes (neutrophil, eosinophil)
- Vasculitis (small vessels, capillaries): thrombus formation
- Clinical signs:
- Below 1 year of age: mild fever, oedema, jaundice, ataxia
- Above 1 year (more severe): fever, depression, ataxia, oedema, vasculitis (myocarditis)
- Diagnosis
- Detection of the agent: staining, IF, PCR
- Serology: IF, ELISA
- Treatment: tetracycline (carriers)
- Prevention: control of ticks
Canine granulocytic anaplasmosis- A. Phagocytophilum?
•Canine granulocytic anaplasmosis - A. phagocytophilum
- Replication in granulocytes
- Fever, neurological signs (brain oedema)
Canine thrombocytic anaplasmosis – A. platys + A.phagocytophilium?
Canine thrombocytic anaplasmosis – A. platys
- Replication in thrombocytes
- Fever, haemorrhages, enlargement of LNs
- Human thrombocytic anaplasmosis - A. phagocytophilum
- Asymptomatic or mild flu-liked signs
Diseases caused by Neorickettsia?
Diseases caused by Neorickettsia
- Vector: flukes; Wide host range
- Replication in monocytes, macrophages
- N. risticii: Potomac horse fever
- Occurrence: USA, Canada, France, Netherlands - pastures, near rivers
- Aetiology: Neorickettsia risticii (E. risticii), replication mainly in monocytes
- Epidemiology:
- Spring -summer- early autumn
- Mortality: 5-30%
- Vector is a fluke (intermediate hosts: snail, flies) - infected flies transmit the infection
- Faeces of infected horses contains the bacterium also
- Pathogenesis
- Infection: flies, faeces
- Replication in gut enterocytes, monocytes, macrophages
- Blood, septicaemia
- Clinical signs: fever, colic, diarrhoea, abortion (months later), laminitis
- PM lesions: acute colitis, LI enteritis, ulcers, necrosis
- Diagnosis
- Epidemiology – clinical signs – PM lesions
- Detection of the bacterium: microscopy, PCR
- Detection of the antibodies: ELISA, CFT
- Treatment, prevention: tetracycline, fluid therapy, inactivated vaccine (US) - poor efficacy
