Haptoglobin and fibrinogen concentrations and leukocyte counts in the clinical investigation of caseous lymphadenitis in sheep

• Published in: Veterinary clinical pathology Vol. 40; no. 4; pp. 496 - 503
• Main Authors: Bastos, Bruno L., Meyer, Roberto, Guimarães, José E., Ayres, Maria C., Guedes, Maria T., Moura-Costa, Lilia F., de Burghgrave, Uiara S., Sena, Ludmilla, Azevedo, Vasco, Portela, Ricardo W.
• Format: Journal Article
• Language: English
• Published: United States Blackwell Publishing Ltd 01-12-2011; Wiley Subscription Services, Inc
• Subjects: Acute phase proteins; Animals; Antibodies, Bacterial - blood; Antigens, Bacterial - metabolism; Biomarkers - analysis; Brazil - epidemiology; C orynebacterium pseudotuberculosis; Carcasses; Cattle; Corynebacterium Infections - diagnosis; Corynebacterium Infections - epidemiology; Corynebacterium Infections - microbiology; Corynebacterium Infections - veterinary; Corynebacterium pseudotuberculosis; Corynebacterium pseudotuberculosis - immunology; Disease Progression; Female; Fibrinogen; Fibrinogen - analysis; Haptoglobins - analysis; Leukocyte Count - veterinary; Leukocytes - cytology; leukogram; Lymphadenitis - diagnosis; Lymphadenitis - epidemiology; Lymphadenitis - microbiology; Lymphadenitis - veterinary; monocytes; Physical growth; Sheep; Sheep Diseases - diagnosis; Sheep Diseases - epidemiology; Sheep Diseases - microbiology; Veterinary medicine; Brazil
• ISSN: 0275-6382; 1939-165X
• DOI: 10.1111/j.1939-165X.2011.00355.x

Background
Corynebacterium pseudotuberculosis is the etiologic agent of caseous lymphadenitis (CLA), a disease that affects small ruminants and is responsible for economic losses, including condemnation of carcasses and damaged hides.
Objective
The goal of this study was to determine if serum haptoglobin and plasma fibrinogen concentrations and peripheral blood leukocyte counts are biologic markers of CLA in sheep.
Methods
Blood from 38 clinically healthy Santa‐Inês ewes selected and segregated from a commercial flock of 2500 sheep in an area endemic for C. pseudotuberculosis was collected every 30 days for 6 months. An indirect ELISA was used to detect IgM and IgG antibodies against C. pseudotuberculosis. Serum haptoglobin concentration was measured using a hemoglobin‐binding assay and plasma fibrinogen concentration by refractometry following heat precipitation. Total leukocyte counts were determined using a hemocytometer, and differential leukocyte counts were performed on smears of peripheral blood.
Results
Twenty‐one sheep were seropositive at the start of the study; 15 became seropositive during the study. Only 2 sheep were seronegative at the conclusion of the study. Haptoglobin and fibrinogen concentrations and WBC counts were not significantly different for seropositive and seronegative animals. Nine sheep, 5 that were seropositive positive at the start and 4 that became seropositive during the study period, developed abscesses in peripheral lymph nodes. There were 15 animals that became seropositive during the study, and their values did not differ significantly among the 3 phases – seronegative, acute (IgM+/IgG±), and chronic (IgM−/IgG+) – of infection. However, 11 of these sheep did not develop peripheral abscesses and had significantly higher haptoglobin concentrations and lower monocyte counts during the acute phase of the disease than did the 4 sheep that later developed abscesses.
Conclusion
Serum haptoglobin concentration and monocyte counts may be potential markers for progression of CLA in sheep.