Hemolymphatic System Flashcards
What horses have the highest PCV?
athletic horses that need increased oxygen delivery to muscle and vital organs
- Thoroughbred
- Standardbred
- American Quarterhorse
- Arabian
- Percheron
What is mean corpuscular volume? What are 2 causes of an increase? Decrease?
RBC size - (PCV x 10)/RBC
- INCREASED: regenerative anemia, older horses
- DECREASED: iron deficiency anemia
What is mean corpuscular hemoglobin (concentration)? What can cause an increase and decrease?
measurement of the average amount of hemoglobin in each red blood cell
- INCREASED: intravascular hemolysus
- DECREASED: iron deficiency anemia
What are 3 unique components of equine RBCs on a blood smear?
- Rouleaux formation
- Howell-Jolly bodies - DNA-containing inclusions found after erythrocyte maturation
- Heinz bodies
What are the 3 most pathogenic equine blood types?
- Aa
- Ca
- Qa
What do the group systems and antigenic factors of equine blood types indicate?
specific gene encoding for the RBC surface antigen
different alleles within each blood group that encode for antigen factors
What is the direct Coombs test?
detects the presence of antibodies against red blood cells by washing patient’s RBC with an anti-immunoglobulin antibody (Coombs reagent)
- diagnoses immune-mediated hemolytic anemia
What is an indirect Coombs test?
detects the presence of antibodies against red blood cells by incubating recipient serum with normal RBCs of known antigenicity (compatible blood group) and monitoring for gross agglutination - equine polyvalent Coombs reagent is then used to enhance detection of any reactivity
What is required to evaluate regenerative or non-regenerative anemia?
bone marrow aspirate from the sternum
Erythrocytosis:
What are 3 causes of relative erythrocytosis in horses?
high concentration of red blood cells due to low amounts of plasma in relation to the number of red blood cells
- dehydration (hemoconcentration)
- endotoxemia (hemoconcentration)
- splenic contraction (excitement/stress)
What is primary erythrocytosis?
polycythemia vera - myeloproliferative disease resulting from the autonomous clonal expansion of hematopoietic progenitor cells
- normal PaO2 and normal/decreased EPO
What is secondary appropriate erythrocytosis? 3 causes?
increased RBC due to compensatory response of EPO production in cases of hypoxia
- chronic pulmonary disease
- right-to-left cardiovascular shunting
- high altitude
What is secondary inappropriate erythrocytosis? 2 causes?
increased RBC due to increased EPO secretion without the presence of hypoxia
- EPO-secreting neoplasms
- renal pathology causing local hypoxia
What are the 2 most common causes of anemia?
- blood loss - trauma, sx, ecto/endoparasites, GI bleeds, immune-mediated thrombocytopenia
- hemolysis - neonatal isoerythrolysis, red maple leaf toxicosis, EIA
(+ non-regenerative - inflammatory disease, chronic abscessation, chronic pneumonia/pleuritis, lymphoma)
What is indicative of anemia? How does this affect TP and bilirubin? How is anemia characterized?
decreased PCV and HCT
- low TP indicative of blood loss
- high bilirubin indicative of hemolysis
erythropoietic failure - BM aspiration, biopsy, serum iron and TIBC, renal function, EPO, serum copper. B12, and folate, GI absorption, chronic inflammation
What blood cell is not present in the horse?
reticulocytes - RBCs mature in the BM, upon regeneration there will be larger RBCs observed (macrocytes)
What are common causes of external and internal blood loss in horses?
EXTERNAL = wound, trauma
INTERNAL = GI/respiratory/GU hemorrhage, EIPH, guttural pouch mycosis, ruptures uterine artery
How is blood loss diagnosed? Internal specifically?
clinical signs and lab tests, like coagulation testing and platelet counts
- ultrasound
- rectal palpation
- thoracocentesis
- abdominocentesis
What is the normal blood volume in horses?
8% of BW
500 kg horse —> 0.08 x 500 = 40 L
How does attitude, HR, and BP change with blood loss?
- < 15% = normal, 30-40, normal
- 15-30% = anxiety, 40-60, normal
- 30-40% = anxiety or depression, 60-80, decreased
- > 40% = obtundation, > 80, very decreased
What are the 3 steps to blood loss treatment?
- stop bleeding - easy if external with compression, clamps, and tourniquets
- treat hypovolemic shock
- blood transfusion
How is hypovolemic shock treated in horses with blood loss?
- crystalloids (20 mL/kg bolus)
- hypertonic 7.2% NaCl (2-4 mL/kg)
In what 2 ways is the necessity for a blood transfusion determined?
- PCV - <20% acute blood loss or <12% over 24 hours
- lactate - leukocytes within closed body cavities consume glucose and produce lactate
What 4 additional treatments may be necessary in horses with blood loss?
- aminocaproic acid
- Yunnan Baiyao
- oxygen
- naloxone
What is required for donors in blood transfusions?
blood typed and tested negative for Aa and Qa antibodies and antigens
- BEST = large, quiet STB or AQH gelding with no exposure to blood products and is UTD on vaccines and Coggins tests
How are major and minor crossmatches performed? What reactions would lead to blood rejection?
- MAJOR = washed donor RBCs + recipient serum
- MINOR = washed recipient RBCs + donor serum
agglutination or hemolysis
What are the 4 steps to blood donor collection? How often can they donate?
- prepare donor with proper diet, hydration, and restrain
- place a 10 or 14 g catheter in the direction of the bloodstream
- collect 8-10 L and use within 24 hours
- replace with crystalloids
every 3 weeks
How are blood transfusions given to their recipient? How should the patient be monitored? When is treatment stopped?
filtered administration set (changed every 4 hours) slowly for 15 mins, then fast
PE, TPR every 2 mins for 30 mins then 15 mins
if there is a reaction - give Banamine, steroids, and Phenylephrine
What are blood smear signs of intravascular and extravascular hemolysis in horses?
INTRAVASCULAR = in circulation release of Hb causes the production of schistocytes
EXTRAVASCULAR = phagocytosis in spleen/liver causes the production of spherocytes
(usually a combination of both)
In what 3 ways are RBCs affected by red maple lead toxicosis? What is it an example of?
- Heinz body formation
- hemolysis - pink plasma
- methemoglobinemia
oxidative stress anemia
What are the most common causes of horses coming into contact with red maple leaves?
- recent storms blew in branches
- neighbor trimmed trees
- most common in late summer to early fall in Middle and Eastern USA
What are some plant, drug, endogenous, and envenomation causes of oxidative stress on RBCs?
- PLANT = wilted red maple leaves, wild onion/garlic, pistachio leaves
- DRUGS = phenothiazine
- ENDOGENOUS = inflammation, neoplasia, metabolic disease
- ENVENOMATION = snakes, bees
What is the etiology of red maple leaf toxicosis?
ingestion of wilted red maple (Acer rubrum), silver maple (Acer saccharinum) or sugar maple (Acer saccharum) leaves rich in gallic acid that is metabolized into pyrogallol, which damages RBCs
What are the 3 most common clinical signs associated with red maple leaf toxicosis?
- depression and increased TPR
- icteric or cyanotic/chocolate brown mucus membranes
- hemoglobinuria (brownish discoloration), bilirubinuria
What are 4 other clincial signs associated with red maple leaf toxicosis?
- colic
- renal insufficiency (overwhelmed by methemoglobin)
- laminitis
- peracute death
What are 4 aspects of blood work indicative of red maple leaf toxicosis?
- PCV decreases rapidly and reaches <14%, increased MCV and MCHC
- Heinz bodies on new methylene blue stain
- increased bilirubin (indirect)
- methemoglobin levels >3% of total hemoglobin
What immediate treatments are necessary for horses with red maple leaf toxicosis? What are some others?
eliminate access, activated charcoal, fluid therapy
- blood transfusion
- vitamin C
- laxatives (mineral oil, magnesium sulfate)
- IM vitamin E and selenium
- acetylcysteine
- analgesics
- IN oxygen at high rates
What are the 3 most common causes of infectious hemolytic anemia?
- EIA
- prioplasmosis
- anaplasmosis
Infectious hemolytic anemia:
What is the distribution of EIA like? What are 4 aspects of its pathology?
worldwide —> annually perform Coggins
- macrophage infection
- pro-inflammatory state
- anemia and thrombocytopenia
- splenomegaly, hepatomegaly
What causes EIA? What are 2 modes of transmission? Incubation?
Retrovirus (lentivirus) —> lifelong carrier = natural reservoir
- FLIES - mechanical carrier, especially horse and deer flies and defense behavior
- iatrogenic: re-using needles
15-45 days
What are 3 important risk factors for the spread of EIA?
- climate and flies (number, species)
- population density of horses and viremia
- unregulated horse races (Bush Track)
What are the 3 most common acute signs of EIA? Chronic?
fever, depression, thrombocytopenia
- increased TPR
- anemia, jaundice, petechia
- hemorrhage
- edema
- muscle atrophy
What is non-apparent EIA?
carrier status of nonclinical horses = increased risk to others (regular Coggins tests!)
How often should tests be done for EIA? What tests are used?
annually —> REPORTABLE
- Coggins test (AGID)
- ELISA (faster)
What are the most common fates of horses with EIA? How can infection be avoided?
lifelong quarantine or euthanasia
- require proof of negative Coggins test at time of purchase
- only participate in events that require documentation
- practice good fly control
- use sterile needles and syringes
- disinfect surgical and dental equipment
- separate horses with fevers, reduced feed intake, and/or lethargy
What is the distribution of equine viral arteritis like? What are 4 aspects of its pathology?
worldwide —> economic, rare outbreaks
- respiratory
- panvasculitis = edema, congestion, hemorrhage
- abortion at 2-10 months
- persistent infection of stallions (testosterone, ampulla)
What is the primary reservoir of equine viral arteritis? What causes this? Incubation period?
carrier stallions
Alpha aterivirus equi (ssRNA) - Bucyrus strain
2 days to 2 weeks
What are 3 modes of transmission of equine viral arteritis? What are 2 important risk factors?
- respiratory, abortion
- venereal (natural, AI)
- indirect
close contact and breeding
What horses are most likely to become symptomatic with equine viral arteritis? What are some signs?
(usually asymptomatic) —> young, old, debilitated
- fever, depression, anorexia, edema
- conjunctivitis, photophobia, periorbital edema
- rhinitis, urticaria, hives
- abortion, stillbirth
- petechia, icterus
- short-term subfertility in stallions due to increased testicular temperature
What syndrome can be (rarely) caused by EVA?
fatal respiratory, or pneumoenteric syndrome
How is EVA most commonly diagnosed? What is indicative in stallions?
- PCR of NP swabs or EDTA blood
- IHC of tissue
- viral isolation
- serology
titer > 1:4 seropositive in sperm-rich fraction of semen compared to seronegative mares (expected conversion in 28 days if +)
How is EVA treated? How is infection prevented?
- NSAIDs
- diuretics
- rest, nursing
MLV vaccination in stallions and non-pregnant mares and breeding management (identify carriers, test semen, select breeding)
What is the distribution of piroplasmosis like? What is the etiology? Incubation?
USA —> test for Ab on import (endemic in the rest of the world)
protozoa —> Babesia caballi and Theileria equi/haneyi (2 weeks!)
What are the 3 modes of transmission of piroplasmosis? What are 2 risk factors?
- TICKS - Rhipicephalus, Dermacentor, Hyalomma
- iatrogenic
- vertical
geographical area (travel) or tick populations in the area
What is the most common type of piroplasmosis in the States? What are some signs?
ACUTE
- fever
- jaundice, anemia, petechiae
- increased TPR
- hemoglobinuria, bilirubinuria
- digestive and respiratory signs
How is piroplasmosis diagnosed? What is treatment like in the US?
serologic competitive ELISA and/or complement fixation test, indirect fluorescent antibody tests
based on USDA-APHIS research - lifetime quarantine, euthanasia
What is the etiology of anaplasmosis? What cells are affected? How is it transmitted?
Anaplasma phagocytophilium - equine granulocytic anaplasmosis (neutrophils)
TICKS - Ixodes
What are 3 important risk factors associated with anaplasmosis? How long is incubation?
- geographic area
- seasons - Fall, Spring
- tick infestation
1-3 weeks
What are the most common clinical signs of anaplasmosis in horses < 1 year, 1-3 years, and adult/geriatric?
< 1 year = fever
1-3 years = fever, depression, edema, ataxia
adult/geriatric = fever, anorexia, depression, limb edema, petechiae, icterus, reluctance to move
What is seen on clinical pathology in cases of anaplasmosis?
- leukopenia
- thrombocytopenia
- anemia
- cytoplasmic inclusions in PMN
How is anaplasmosis diagnosed?
- PCR
- 4DX Snap (IDEXX)
What is treatment for anaplasmosis like? What medications can be used?
SUPPORTIVE
+ Oxytetracycline 7 mg/kg/day IV for 8 days
+ oral Doxycycline or Minocycline
Tick-borne diseases:
