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DETAILED HAEMATOLOGY / BIOCHEMISTRY - Editorial Comment

Editorial Comment (Editorial Overview Text Replicated on Overall Species page - Loxodonta cyclotis - Forest Elephant)

HAEMATOLOGY:

BIOCHEMISTRY:

(References are available in detailed literature reports below)

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Haematology

Source Information SUMMARY:

Red blood cells:

  • The red blood cells are large, 9.5 - 9.6 Ám diameter. (B453.4.w4)
  • Elephant red blood cells are large, anucleate, biconcave disks (diameter about 9.1 Ám, maximum depth about 2.0 Ám) which, due to their large size, often appear as target cells on air-dried blood films. The red blood cell count is relatively low, consistent with the large size of the individual red blood cells (MCV 112-130 fl). (B463.1.w1)
  • Elephant red blood cells have a mean diameter of more than 9 Ám, MCV 81-160 femtolitres and a haemoglobin concentration of 7.4 - 15.8 pg. Due to the large cell size, the red blood cell count is relatively low. (B455.w8)
  • Cell counts are 3.2 - 3.8 rbc/mL, 9.5 - 12.0 x10│ wbc/mL and 450 x 10│ platelets per mL. (B453.4.w4)
  • Red blood cell diameter in elephants is 9.25 Ám. (B451.7.w7)
  • Haemoglobin of elephants has a high oxygen affinity, slightly higher in the African than in the Asian elephant. Increasing carbon dioxide causes only a slight release of oxygen by elephant haemoglobin. (B451.7.w7)
  • Oxygen affinity in Asian elephants is higher than in African elephants. (B450.14.w14)
  • Elephants have the largest erythrocytes of any mammal, mean diameter 8.8-10.6 Ám and an associated low total red blood cell count. (B461.185.w185)
  • Elephants have a high erythrocyte sedimentation rate, faster than that of other mammals studied; (B461.185.w185, J402.65.w1, J46.185.w1) for African elephants, 34.6 mm/hour (unweighted mean of results of several studies; range of means 21-61.5 mm/hr). (J402.65.w1); 61.5+/- 48.8 (mean +/- SD; range 0-159.0) mm/hr. (J46.185.w1)
  • Elephant red blood cells have a high resistance to osmotic lysis at low saline concentrations, (B455.w8, J46.185.w1, J402.65.w1) which may be related to the large size of the cells (J46.185.w1) and may be important to prevent cell lysis when an elephant drinks a large amount of water due to thirst or dehydration. (B455.w8)
  • Rouleaux formation occurs readily in elephant blood. (B455.w8, J2.24.w4, J402.65.w1)

Blood clotting:

Leucocytes

  • Bilobed mononuclear leucocytes found in elephants are classified as monocytes, based on their cytochemical staining reactions; trilobed cells are seen also. The numbers of these cells are increased in juvenile elephants compared with adults, and in elephants with inflammatory disease. (B463.3.w3, J2.24.w4)
  • Note: the bilobed cells have been classified as lymphocytes in some studies, making comparisons of differential white cell counts between studies difficult. (B455.w8, B461.185.w185)
  • Neutrophils seen in Leishman-stained blood smears have reddish cytoplasmic granules and may therefore be described as heterophils rather than neutrophils. (B455.w8, J2.24.w4)
  • Basophils are present in elephants, but in low numbers. (J1.11.w9, J402.65.w1, B455.w8)

Variations with age, sex and physiological status:

  • A study of young African elephants aged four to eight years old (21 females, 10 males) found that there were no significant (P<0.05) variations in haematological parameters with age (over this age range) or sex. (J2.16.w3)
  • In a study of African elephants in Uganda, calves aged one to five years had significantly higher rbc count, leucocyte count, MCH and MCV. (J46.185.w1)
  • No male-female differences were noted in a study of African elephants in Uganda. (J46.185.w1)
  • In one study, female African elephants had higher total white blood cell counts than males; no other differences associated with age or sex were noted in any haematological parameters. (J1.11.w9)
  • Pregnant elephants may have a lowered total red blood cell count and haematocrit and an increased erythrocyte sedimentation rate. (B461.185.w185)

Variations with season:

  • There may be seasonal variations in haematology, such as higher red blood cell counts and haemoglobin in the dry season than in the wet season; this may be due to dehydration during the dry season. (B451.7.w7, B461.185.w185, J46.185.w1)

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Biochemistry

Source Information SUMMARY:

General:

  • Elephant blood biochemistry is generally similar to that of other large herbivores. (J402.65.w1)
  • A study of elephants shot in Uganda, found that sodium levels were lower and potassium levels higher in the wet season versus the dry season; serum cortisol was variable and triglyceride levels varied between areas. (J400.62.w1)
    • Sodium 135.4 +/- 4.3 mmol/L (mean +/- SD) in the wet season (12 males, 43 females, ages 0 to 49 years) and 137.2 +/- 6.2 (22 males, 55 females, ages 2-60 years) in the dry season. (J400.62.w1)
    • Potassium 6.42 +/- 0.86 mmol/L (mean +/- SD) (nine males, 40 females, ages 1-49 years) in the wet season and 6.08 +/- 0.83 (15 males, 41 females, ages 2-60 years) in the dry season. (J400.62.w1)
    • Cortisol varied from 66 - 825 nmol/L, mean 315 +/- 182 nmol/L (mean +/-SD). (J400.62.w1)
    • Triglyceride levels (0.59 +/- 0.29 mmol/L, mean +/- SD, n=61) did not vary with sex, age or season but values from one park region were significantly lower than values from other park regions. (J400.62.w1)
  • A study of young elephants ages four to eight years old found that serum chloride increased with age, from 8.3.2 +/- 3.0 mEq/L, (mean +/- SD) in those of four years of age to 91.8 +/- 8.3 in those of eight years old, while BUN (blood urea nitrogen) decreased with age over this age range, from 9.2 +/- 1.9 mg/dl in four-year-olds to 7.3 +/- 2.1 mg/dl in eight-year-olds. (J2.16.w3)
  • A study of free-ranging elephants in Zimbabwe found that during the dry season, BUN was significantly increased (P<0.001, possibly due to protein catabolism), creatinine was significantly decreased (P<0.001), total protein and albumin were both decreased (P<0.001), calcium was decreased (P<0.001), magnesium was decreased (P<0.02), phosphorus was increased (P<0.001) and ALT was decreased (P<0.02). (J2.24.w3)

Variations with age, sex and physiological status:

Variations with season:

  • In the dry season, African elephants have been noted to have reduced BUN, increased bilirubin, increased creatinine, increased sodium, reduced potassium, increased amylase. (J402.65.w1)
  • In the dry season, African elephants have been noted to have higher creatinine, sodium, globulins and T3 uptake, and lower blood urea nitrogen (BUN), potassium, phosphorus, albumin and thyroxine. (B455.w8)
  • There may be both seasonal and geographical area effects of blood calcium levels. (J402.65.w1)

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Authors & Referees

Authors Debra Bourne (V.w5)
Referee Susan K. Mikota DVM (V.w72)

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