1-Jul-14 Flashcards
Where do platelets come from?
Myeloid stem cells - CFU-Meg -> Platelet. Also erythrocyte, neutrophil and monocyte come from myeloid
When spun down which part of the PCV tube contains the leukocytes
Buffy coat
Why does stress cause a leukophillia?
Leucocytes washed off wall of BV
How to distinguish a plasma cell?
Eccentric nucleus. Abundant cytoplasm.
Normal ratio of circulating pool to marginated neutrophil pool?
Normally 1: 1 but in cats can be 1: 3 i.e. 3 x as many marginated cells as circulating
Half life of neutrophil
5 to 10 hours (very short)
What is a degenerative left shift?
Left shift= more immature neutrophils (i.e. more bands than segmented). Degenerate: Already left blood, fighting with bacteria therefore neutropenia and bands > segmented
what would a regenerative left shift be?
Left shift: but neutrophillia i.e. immune system is keeping up
What type of left shift is normal in cows/horses
Cows/Horses tend to start infections with neutropenia and bands > segmented therefore DEG LEFT SHIFT but this is because they don’t have a storage pool. Give antibio until regen
Why is a degen left shift more serious in dogs?
In dogs a degen left shift implies the immune system is behind as the storage pool has been used up and bands > segmented with a neutropenia. Give ANTIBIO
Right shift
Hypersegmentation
How to differentiate toxic change from degen left shift
Toxic change is ‘faulty’ neutrophils caused by accelerated production NO NEED FOR TOXINS
What species are neutrophils NORMALLY low?
Greyhounds NORMAL leukocyte levels are much lower i.e. 2 x 109 instead of 3 x 109
When neutrophils are below what amount are prophalactic antibiotics indicated?
<2x 10 e9/ L
How does the degree of differentiation help determine cause of neutrophillia?
Well differentiated–>look for underlying infec Poorly differentiated–> myeloid leukememai
Why does steroid induced neutrophillia have more highly segmented neutrophils?
Longer in circulation therefore more segmented
Normal nucleus of lymphocyte should be same size as …
Normal nucleus of lymphocyte should be same size of RBC.
How does longevitiy differ between t cells and b cells
can’t differentiate on microscopy but t cells long lived and b cells mostly short lived.
Endothelial cells are pro or anticoagulant?
Flattened endothelial cells are both pro and anti coagulant. Normally anticoagulant and inhibit platelet aggregation. Barrier to prevent subendothelial collagen (which is procoagu)
Where are Von Willebrand factors produced? Circulates bound to factor ____
Endotelial and formed in Weibel Palade. Also produced by platelets and MEGAKAROCYTES. Responsible for platelet adhesion to collagen. Circulates bound to factor 8
How long do platelets circulate for
5-9 days in most species.
Platelets are derived from cytoplasm of
Megakarocytes from bone marrow mediated by thrombopoeitin. Pale basophilic`
Why do we look at platelet and neutrophil numbers before erythrocytes whn suspecting bone marrow problem
Platelets produced from megakaryocytes in bone marrow. Circulate for 5-9 days c.f,. neutrophil half life 5-10 hours. RBC = 60-100 days therefore longer to notice change.
Platelet has what two receptos
1 for Von Willebrand factor 1 for Fibrinogen Both can have deficiencies
Primary haemostasis steps
- Damage to endothelium causes exposure of subendothelial collage 2. Von Willebrands factor is released from damaged endotelim 3. Platelet adhesion occurs 4. Platelets bind to collagen via 2 receptors
When referring to coagulation we are referring to ____
Secondary haemostasis Involving Tissue Factor and final step is Fibrinogen–>Fibrin
Extrinsic factor involves
Factor VII and Tissue Factor = Factor 10
Factor___ converts prothrombin to thrombin
Factor 5 converts prothrombin to thrombin which allows fibrinogen to be converted to fibrin.
Fibrinolysis is enzymatic breakdown of fibrin by ___
Plasmin which is derived from plasminogen in the plasma membrane of platelets.
Platelet count can be done on blood collected into EDTA tube. Which species is this unreliable?
Cats, sheep and goat and overlap between rbc/platelets. Cats= platelet clumping also very common. Do manual count
Which breed of dog should manuel platelet counts be done in?
Cavalier King Charles. INHERITED DISODER = LARGER PLATELETS therefore counted as rbc’s Appear thrombocytopenic as don’t need as many as larger.
< what reference interval = thrombocytopenia
t normally cause a decrease past this
Worry about spontaneous bleeding when platelet conc is <
< ~25 x 10 9/L
Buccal mucosal bleeding time =
Measures length of time for platelet plug to form, Evaluates primary haemostasis / platelet function. Blot blood until stops
What will happen to buccal mucosal time for coagulopathies
Coagulopathies = secondary haemostasis = fibrinogen therefore will not affect buccal mucosal time (only tests primary haemostasis/ primary function test)
Does the buccal mucosal test for thrombocytopenia
Does require some platelets but more a platelet FUNCTION test
Mechanisms of thrombocytopenia
Increased platelet destruction: IM (most common), Haemorrhage , DIC, Sequestrum (e.g. spleen) OR DECREASED PRODUCTION/ INFECTIOUS
Evans Syndrome
Concurrent immune mediated thrombocytioenia and anaemia. Thrombocyt= bleeding and have deficient blood cells as well!
During haemorage, numbers of platelet should not drop below
Should not be below 100 x 10 9 Difficult to distinguish between bleeding causing thrombocytopenia or thrombocytopenia causing bleeding
If platelet count is >100 x 10 9 but still low then likely cause is
If >100 x 10 9 platelets then bleeding/haemorrhage is likely causing the thrombocytopenia. If <100 x 10 9 then likely something else e.g,. DIC, Immune-mediated
4 infectious organisms that cause thrombocytopenia
- FeLV 2. BVD 3. Ehrilichia 4. Leismania 5. Babesia
Which breed of cows are predisposed to thrombocytopenia
Simmetals predisposed to bleeding
Causes of thrombocytosis
Physiological: epinephrine induced splenic contraction Reactive (most common) due to increased thrombopoeitin or IL6 (inflamm, haemorrhage, iron deficiency)
Why does Iron Deficiency cause thrombocytosis
Anaemia for a week duration = thrombocytosis. Due to cross link when getting more rbc’s from bone marrow also increases platelets.
Essential thrombocythermia
Myeloproliferative disorder - bone marrow problem / neoplasia
Von Willebrand factor exists in what 3 forms
Small, medium and large form. Where large form is the most efficient. Circulates bound to factor 8.
Von Willebrand disease clinical signs
mucosal bleeding, GI epistaxis, haematuria. Bleeding may be absent NO PETICHAIE Prolonged mucosal bleeding time without thrombocytopenia
Type 1 Von Willebrand disease
Most common (90% of cases) All 3 multimers present (small, medium, large) but in decreased concentration Seen in Dobermans Autosomal inhertiance so male/female affected equally
Type II Von Willebrand disease
Large multimers disproportionally decreased . Severe and uncommon. German shorthaired pointers. Autosomall
Type III Von Willebrand disease
Absence of all multimers. Die quickly Seen as puppy dogs
Tests for Von Willbrand disease collected into what tubes?
Collect blood into citrate or EDTA tube. If collected into citrate tube needs to be dilated 1:9 with blood. Seperate plasma immediately and ship with ice,
How will a) clotting and b) lipemia affect the Von Willebrand factor test
Citrate 1:9 ratio., Clot will decrease number of factors= false positive Lipaemia doesn;t affect.
50-70% vWF:Ag =
Carrier status likely to transmit to offspring. 70% = normal
Doberman in for elective ovariohysterctomy. Suspect vWd what preventative treatment can be given for type 1 vWd
Type 1: small, med, large multimers present in lower conc. Desmopressin can increase release of vWF from endothelial cells and be a prophalaysis during surgery. Intranasal prep
Important when testing blood for vWF
Minimise trauma when extracting due to activating platelets etc. 1:9 ratio citrate to blood. Centrifuge and remove plasma within 1 hour freeze if to be transported Analyse within 4 hours or freeze plasma
How to measure activated clotting time (ACT)
Tests intrinsic and common pathway 2ml whole blood into ACT tube containing diatomaceous earth. Incubate for 60 seconds at 37 degrees. Time to initial clot formation is ACT time. Will be prolonged by thrombocytopenia Less sensitive than PTT
Partial thromboplastin time (PTT) tests for…
Intrinsic and Common pathway of coagulation Incubate citrated plasma with excess phospholipid / contact activator and Calcium DON’T NEED PLATELETS LIKE YOU DO FOR ACT Measure time for formation of a clot
Difference between activated clotting time and partial thromboplastin time
ACT = less specific than PTT but ACT can be done NEXT TO PATIENT. PTT= Lab test and everything is provided in excess ACT relies of platelets and will be prolonged by thrombocytopenia.
Long PTT indicates
Problem in factors or intrinsic (XII, XI, IX, VIII) or common pathway (X,V, II) Requires a <30 % in a factor for a prolonged PTT. Not affected by thrombocytopenia (as providing the factors)
Test for EXTRINSIC and common pathway
Prothrombin time Incubate citrated plasma with tissue thromboplastin (=tissue factor) and citrate. Measure time for clot formation
Why will liver failure cause prolonged Prothrombin time
Liver produces clotting factors. Vit K deficinecy and factor VII deficiency will also cause increased prothrombin time Prothrombin time tests extrinsic and common pathway. Test citrted plasma with tissue thromboplastin (tissue factor) and citrate.
How to remember ACT, PTT,PT
A prolonged PTT but a normal PT would be indicitive of a problem where?
SEE TRIANGLE TO WORK OUT
Intrinsic pathway fault
Prolonged PT but normal PTT would be indicitive of problem where
Extrinsic pathway problem
Abnormal PTT and PT would indicate a problem where?
Common pathway
or Problem is intrinsic AND extrinsic pathway
OR Vit
FDP test is…
Use ____
Fibrin degration products. Use Serum
Latex agglutination test.
Useful test for DIC
Most common cause of vitamin K deficiency in a) dogs b) cattle
a) dogs: rodenticide toxicity
b) cattle: sweet clover ingestion
Vit K factors: 2, 7, 9, 10
all produced in liver
Which are the vit K dependent factors
II, VII, IX, X
Which vit K dependent factor has the shortest half life
Factor VII therefore rodenticide/ sweet clover poisoning will notice this decrease first.
As factor VII has the shortest half life, if caught early enough PT time will be increased first
AS FACTOR VII IS EXTRINSIC AND COMMON
then PTT as 2,7,9,10 influence all three pathways
Affect on platelet numbers and buccal muscosal bleeding time post rodenticide posioning
Rodenticide posioning = vit K deficiency therefore normal buccal mucosal time and platelet numbers (may have thrombocytopenia secondary to haemorrhage but unlikely to influence BMBT)
DIC haemostatic abnormalities
May be acute or chronic.
Cannot have DIC without thrombocytopenia
Prolonged PT/PTT
Elevated FDP’s
Decreased fibrinogen (as using it up)
Decreased antithrombin III
Want 3 or 4 of these for diag of DIC
Treatment of DIC
Stop coagulation
Heparin
Transfusion of whole blood/plasma
Difference between Echymosis and Petichiae
Echymosis >1cm
Petichia <1-2mm
Platelet defect likely i.e. platelet function
GOOD TEST FOR PLATELET FUNCTION = BUCCAL MUCOSAL BLEEDING TIME
Function of the FelV retrovirus
ssRNA to dsRNA integration into host DNA.
- destruction by immune response
- infection with virus protection
- transformation to neoplasia (LYMPHOMA!)
Core FeLV protein that is the basis for most diagnostic tests is
p27 - gag protein
May circulate in plasma or excreted in tears/saliva
Snap testing/ ELISA.
Anti p27 not effective as masked in capsid
Envelope protein of FeLV
P15E- Spike - immunosuppression
gp70 (knob) defines subgroup- A,B,C,
A= Only one cat to cat
B= endogenous
C= mutant form of A
Ab subgroup specific- important for vaccination!
Important of FeLV subgroup (how is it determined)
gp70 (knob) defines subgroup- A,B,C,
A= Only one cat to cat
B= endogenous
C= mutant form of A
Ab subgroup specific- important for vaccination!
Epidemiology of FeLV in UK Cats
1-2% in ‘healthy’ cats
20% in symptomatic cats
Pathogenesis of FeLV
Either effective immune response (p27 negative) can still lead to latent form which leads to latent virus in bone marrow, lymphoid tissue = malignancy
OR INEFFECTIVE IMMUNE RESPONSE = persistant viraemia
Define the terms ABORTIVE, REGRESSIVE and PROGRESSIVE with regard to FeLV infection
ABORTIVE: Effective immune response- virus cleared and p27 negative
REGRESSIVE: Transient viraemia –> Latent viraemia (bone marrow, lymphoid tissue) non replicating
PROGRESSIVE: Replication in marrow/lymphoid, p27 positive- PROGRESSES to persistant viraemia
Survival of FeLV outside body
Prodominantly saliva and nasal secretions
Also in milk, faeces and urine.
ONLY SURVIVES FEW HOURS OUTSIDE BODY due to ENVELOPE
sharing food bowls, mutual grooming
IN UTERO SPREAD
Clinical signs of FeLV
iNAPPETANCE, WEIGHT LOSS/WASTING, Poor coat condition, Lymphadenopathy, persistant fever,
pale mucos membranes, occular disease (FUNDIC EXAMS IMPORTANT= UVEITIS), gingivitis, stomatitis, abortion in queens, infections of skin
Pathogenesis of FeLV secondary infections
FeLV is IMMUNOSUPPRESSIVE.
bone marrow suppression, viral infection of haemopoeitic stem cells, anaemia- non regenerative, aplstic or regrenerative, thrombocytopenia
Why is anaemia common in FelV
bone marrow suppression, viral infection of haemopoeitic stem cells, anaemia- non regenerative, aplstic or regrenerative, thrombocytopenia
What type of neoplasm are FeLV (p27+VE) cats more likely to develop
LYMPHOMA (most often thymic and multicentric)
Expect it within 2 years
Tests for FeLV
Snap test ELISA for p27 protein is screening test for FeLV then qPCR for confirmation
A negative test snap test result indicates
(6 things)
- unexposed
- elimination of previous infeciton
- early infection (re test 9-12 weeks)
- latent infection
- localised infection
- false negative
Treatment of FeLV
Prevent secondary infections
Neuter if entire
Confine indoors?!
IF sick, treat secondary illness
Policy of FeLV vaccination
Test before vaccinate. If already p27 positive no point vaccinating.
If indoors cat little point
Prevalence of FIV in UK
Also retrovirus
Normal UK 3-5% (more than FeLV)
Sick 18%
MAINLY TRANSMITTED BY BITING
Difference in transmission of FeLV and FIV
FeLV: Mutual grooming
FIV: Aggressive (needs to be innoculated- saliva)
Some vertical transmission likely
5 phases of FIV
- Acute- transient mild illness days to weeks
- Asymptomatic carrier: can last up to 10 years.
- persistant lymphadenopathy: can persist for months
Mononuclear cells- neutropenia/lymphopenia
terminal phase
Which has a higher risk of lymphoma FIV or FeLV
FIV: 5 times more likely for LYMHOMA and SCC
FeLV: 60 times more likely (thymic/mediastinal)
Antibody test for FIV
P24 (c.f. FeLV = p27 gag protein!)
Interference with vaccination/ MDA
Most cats develop antibodies within 60 days
Test kittens from __ months of age onwards for antibodies for FIV
6 months.
Takes time to sero convert.
Cat takes 60 days to develop antibodies against p24 protein.
MDA can interfere with test.
IFA now recommended test
FIP causative agent
feline coronavirus infection is common, clinical disease is uncommon
FIP is a fatal disease of domestic and non-domestic cats
Feline coronavirus survival in environment
short lived (24 hr at room temp) but can survive 7 weeks if protected from heat, light and chemicals.
Replicate in cytoplasm
Occurs envelope from ER or Golgi
Majority of oro-nasal Feline Coronarvirus infection results in
Presence in normal cats
70% transient infection.
10% Persistant infection
5% FIP
FIP pathogenesis
Feline infectious peritonitis. Mutation of feline coronavirus,
Immune complex disease
- vasculitis, complement activation, excessive cytokine production
Endothelial cell retraction, increased vascular permeability (protein rich exudate)
How does the type of cell-mediated immune response influence the outcome of infection with feline cornoavirus
Strong response: protection
Partial response: Non-effusive disease (granulomatous disease- dry form)
Poor response: Effusive disease (wet form- protein rich exudate)
75% of FIP cases are the ____form characterised by __
75% FIP are effusive form characterised by protein rich exudate causing ascites, pleural effusion (= dyspnoea), and more rarely pericardial effusion.
Predelection sites for non-effusive FIP?
Eye (may present with uvevitis, brain/cns, kidney, liver and localised region of intestine)
What is the use of IFA and ELISA tests for cats infected with FCoV or FIPV
Positive titre indicates prior exposure to FCoV not necessarily presence of FIP. High titre may indicate granulomatous form
Vaccination for FIP
Intranasal
Wants strong cell-mediated immune response without strong antibody response
=Primusil
Only way to clinically diagnosis FIP
Histopath only way to diagnose FIP.
Non-effusive harder to diagnose
Other IFA/ elisa only tells you infection with feline coronavirus
Feline infectious anaemia treatment
Doxycycline i.e. a tetracycline susceptible. (NO CELL WALL)
Mycoplasma haemofelis = LARGE FORM, Candidatus Maycokplasma haemomuntum= SMALL FORM, Candidatus Mycoplasma turicensis.
ECTOPARASITE CONTROL!!
Pathogenesis of reoccurance of Mycoplasma
Mycoplasma caused IM haemolytic anaemia. Concurrent disease due to immunosuppresion; if recover from infection = chronic infection for long period of time
Reactivation and Recurrance possible.
Mycoplasma haemofelis is gram ___
Gram negative
Routes of transmission: Fleas, blood transfusion, female cats to neonates (in utero, nursing), fighting,
More common in young entire males, often latent hidden in spleen
Relavance of FeLV in pathogenesis of Mycoplasma
Disease more common in young male cats, concurrent illness (i.e. FeLV = acute disease, recovered cat may relapse with stress.
Changes in PCV for Mycoplasma
Rapid decrease in PCV as organisms in blood go to spleen.
PCV rises again as organisms disappear.
Some cats PCV continues to fall due to RBC destruction.
Test for Mycoplasma hemifelis
Positive Coombes test. Extravascular haemolysis by MACROPHAGES in liver, spleen, lungs and bone marrow.
Clinical signs of M. haemofelis.
ACUTE: lethargy, inappetence/anorexia, fever (39degrees-41), anaemia, splenomegaly and icterus (pre-hepatic)
CHRONIC: Normal or sub norm temp. icterus/splenomegaly less likely.
Type of anaemia for Mycoplasma haemofelis
regenerative anaemia, reticulocytosis.
Polychromasia
If v. acute may be pre regenerative (takes 2-3 days)
What is important to remember when giving Doxacycline
Doxacline is a tetracycline used for the treatment of Mycoplasma haemofelis (no cell wall)
It can cause gastric effects (muscosal irritation), abdo discomfort, vomiting, inappertence and oesophagitis and potential stricture formation THEREFORE MUST BE GIVEN WITH FOOD OR WATER
same for clindamycin (for cats)
Cats with type b blood will die if given
cats with type B blood will die if given blood transfusion with type A blood.
Cats with type A given Type B won’t die but will have tranfusion reaction. NOT EVEN ONCE!!!
Dogs can normally be given tranfusion once without problem.
Why might prednisalone be given to treat mycoplasma haemofelis
Along with doxacycline, immunosuppressive therapy (prednisalone) may inhibit erythrophagnocytosis (IMMUNE MEDIATED anaemia!)
With liver disease would expect an increase in ____ test first because…
With liver disease would see prolonged PT test first (same as rodenticide poisoning)
Factor 2,7,9 and 10 all activated by liver therefore affects common, instrinsic and extrinsic pathways.
Factor VII = shortest half life therefore PT first affected.
Mechanism by which Factors 2,7,9 and 10 are vit K dependent
Factors 2,7,9 and 10 are produced by liver.
Need to be activated by vit K depedent carboxylase which requires decreased VitK (via Vit K reductase)
This vit K reductase is inhibited by Coumarin like rodenticides
In event of rodenticide poisoning, Vit K needs to be supplemented. How is this given
NOT IV= ANAPHALAXIS
NOT IM= HAEMATOMA
GIVE ORALLY OR PARENTERALLY
Test for Fibrolysis
Latex aggluination test
Measure Fibrin Degration Products.
TESTS ON SERUM (c.f. PT, PTT, ACT= citrated plasma)
DIC = +++ FDPs but also with liver disease
Jugular vein thrombosis, liver disease, haemorrhage
