Red Blood Cell Characteristics in Texel Sheep: Implications for Anemia Diagnosis in Haemonchus contortus infection.
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Abstract: Parasitic infections are the main cause of losses in sheep production, especially due to the occurrence of severe anemia. Therefore, its accurate and rapid identification is crucial for handling the clinical infection. The aim of this study was to compare different methods to detect anemia in White Dorper (DO), Texel (TX) and Santa Inês (SI) sheep breeds. 151 lambs (42 DO, 44 TX and 65 SI) were raised in an endemic area for H. contortus infection. The lambs were monitored for faecal egg counts (FEC) and packed cell volume (PCV) from 63 to 189 days of age. At 105 and 189 days of age, complete hemogram was assessed. The criteria for anthelminthic treatment (AHT) were PCV ≤ 24% and FEC ≥ 10,000, or PCV ≤ 22%, and for anemic status were PCV < 24% or red blood cell counts (RBC) < 8 million/mm3. The correlation between PCV by microhematocrit and complete hemogram (Ht) was 0.85. However, PCV and Ht were 0.88 and 0.95 correlated to RBC. 56 lambs were considered anemics based on RBC, but 12 (7 TX – 58.3%) and 9 (6 TX – 66.7%) presented globular volume >24% by Ht and PCV, respectively. Among these divergent measurements, we observed 2 TX with 25% and 30% PCV at D105, but 21% (criteria for AHT) at D126. TX animals presented corpuscular volume means (VCM) and hemoglobin concentration means (CHM) higher (p<0.001), but concentration of corpuscular hemoglobin mean (CHCM) lower (p<0.001), compared to SI and DO breeds. To our knowledge this is the first report pointing out for differences in erythrocyte sizes among sheep breeds. Since TX present higher VCM compared to the other breeds, the identification of anemic animals through globular volume, as PCV or Ht, may fail, and consequently some animals requiring AHT may be missed. Therefore, the cut-point of globular volume for this breed may require a review, aiming to avoid death due to parasitic infections.
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Glóbulo Vermelho, Ovelha, Diagnostico, Anemia Infecciosa, Haemonchus Contortus, Erythrocytes, Lambs, Anemia (fern), Hemoglobin, Parasitoses, Blood cell counts