Lecture 2 Flashcards
(29 cards)
What is tick fever in australia
Tick transmitted disease of cattle caused by either
- B.bovis
- B. bigemia
- A. marginale
Why is B.bovis so important
Causes 80% of outbreaks and even higer % of death
VERY PATHOGENIC
Where are B.Bovis outbreaks most likely
Bos taurus cattle
How do animals get infected with Babesia
Female ticks get infected after feeding on a parasitemic host. Then the infection is transmitted by next generation of ticks
- Larvae for B.bovis
- Nymph and adults for B.bigemia
Where do transovarial transmission need to get
Salivary glands -> divide and change to sporozoites -> babesia leave
Generatio time of babesia
8 hours
When can your see parasitemia
- B.bovis - 6-12 day
- B.bigemia: 12-18 days
Susceptibity of babsia depends on
- Age - under 9 monts develop mild or inapparent signs
- Breed - bos indicus more resistance
- Condition of host
- Immunity - recovery is followed by strong resistance
What is the source of infection of babsia
- Infected animals
- Ticks
- Single tick can transmit
How do ticks get infected with babsia
Tick bite
Where is outbreak of babsia frequent
- Animlas 1-3 years
- Animlas introduced in endemic areas
- South QLD: most cases in autumn
- North QLD: most cases winter or spring
What is endemic stability
The presence of infection with babsia and their vectors in a cattle population without measurable economic losses or clinical disease
What does pathogenisi depend on wih B. bovis
- Species
- Strain
- Condition of host
What does B.Bovis cause
- Hypotensive shock syndrome
- Blocking of capillaries by RBC
- Stasis
- Hypotension
- Extravation of plasma fluid
- Activation of the coagulation system -> increased fibrin concentration that adhere to RBC -> RBC becomes sticky
- Local proliferation of the parasites -> increased local parasitemia
- Sequestration
- Ridges develop on the surface of infected RBC
- Changes in the structure of RBC
- Increased viscosity
- Decreased deformability
- Stasis
- Hamolysis
- Cause increased osmotic ability causing damage to the blood cells
- Infected blood cells increase
- Damages organs
- Intravascular haemolysis -> free hamoglobin released from rbc is excreted in urine -> haemoglobinuria
- Phagocytosis of infected/damaged rbc in liver and spleen -> enlargement of these organs
- Cause increased osmotic ability causing damage to the blood cells
- The imune response tin the pathogenesis of the disease
Importance of immune response
- Species specific
- Immunity develops 3-4 weeks after vaccination
- Most animals recover from disease will have a strong and long immunity
- Babesa persist in blood for wile
- Maternal Ab in calves protects them for 2 mntsh
- Calves are protected up to 9 montsh
- Primary infections depends on macrophages and Nk cells
- Persistent infections depend on CD$+ cells and antbodies
What is the significance of increased adherence and sequestration?
- Immune evasion
- The parasites invade cells in vicinity
- In the brain -> cerebral babesiosis
- In the lungs -> sequestration of RBC and neutrophils -> increased permeability -> oedema -> death
Clinical signs of B.Bovis
- Appear 6-12 days after begin to feed
- Fever
- Inappetence, depression, weakness, muscle tremor
- Death within one week of fever
- Anaemia, haemoglobinuria, jaundice
- Diarrhoea
- Cerebral babesiosos: hyperaesthesia, agression, coma, convulsion, paralysis
Pathogenesis of B.bigemia
Entirely related to the intravascular haemolysis
RBC count reduced
Increased levels of hemoglobin in serum
Proteinuria
Pathology of babesia bovis
- Acute infection most organs are swollen and congested, prolonged causes may show anaemia and jaundice
- Blood is thin
- The spleen is enlarged with dark red pulp
- The liver is enlarged and brown/yello, the gall bladder contains large amounts of thick granular bile
- Kidneys congested and enlarged
- The lungs may be haemorrhagic with odema
- In cerebral babesiosis the grey matter in the brain has a characteristic pink colour
- Capillaries int he brain are dilated and filled with closely packed rbc, most which are parasitized
How to diagnose babsia
- History
- Clinical signs
- Thin and thick blood dilms stained by Giemsa - capillaries from tail and ear becasue there is a high chnage of finding the infection here
- Serology: ELISIA, IFAT
- PCR
Diagnosis in animals with a PM
- Pathology
- Histopathology
- Films from peripheral and general circulation and impression smears from cerebral cortex, spleen, liver, kidney and bone marrow
Treatment of Babsia
- Imidocarb dipropionate (Imizol, Imidox)
- 1.2mg/kg - treatment
- 3mg/kg - prevention
- D not give to lactating dairy cows
- Remove animals from infeted area and treat for ticks
