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1358 Leptospira Diagnostic Tests Leukocyte Function Tests

Leptospira Diagnostic Tests
VetBooks.ir Definition Drug Effects

cine (≤1 : 400).
Leptospirosis is a zoonotic disease caused by usually much lower by 3-6 months postvac- Antibiotic therapy may cause a blunt rise in
pathogenic serovars of Leptospira interrogans, a • Positive ELISA or IgM LFA: exposure to serologic titer and cause negative PCR and
motile, spiral-shaped bacterium (spirochete). Leptospira spp. or vaccination (<6 months culture results.
Multiple serovars cause clinical disease. interference postvaccination for IgM LFA
and > 1 year for ELISA). Specimen Collection and Handling
Physiology • Positive PCR: supportive of infection MAT: 2 mL of serum (red top tube). Stable
• Organisms penetrate abraded skin and/ 5 days at 2°C-8°C or longer if frozen. ELISA
or mucous membranes, replicate in the Next Diagnostic Steps to Consider or IgM LFA: 1 mL of serum (red top tube).
bloodstream, and rapidly disseminate to if Levels Are High Stable 7 days at 2°C-8°C. PCR/RT-PCR: 2 mL
multiple organs, most importantly liver and • Treat if signs suggest active disease. Consider EDTA whole blood (lavender top tube) and
kidney (allows shedding in urine). Organisms PCR/RT-PCR (urine, blood, cerebrospinal 2 mL urine in sterile container. Stable 10 days
replicate in the renal tubular epithelium, fluid, aqueous humor, or tissue); direct at 2°C-8°C or longer if frozen. For in-clinic
causing chronic tubulointerstitial nephritis fluorescent antibody testing on tissue tests, follow manufacturer’s directions.
and a persistent carrier state if untreated. (kidney, liver) collected before antibiotic
See p. 583. administration. Relative Cost: $ (ELISA and IgM LFA);
• Serovars included in vaccines: canicola, • Darkfield microscopy or culture (blood, $$ (MAT)
icterohaemorrhagiae, grippotyphosa, and urine) is technically difficult and not widely
pomona. available. Pearls
• The diagnosis can be missed if relevant
Reference Interval Causes of Abnormally Low Levels serovars are excluded from serologic testing,
• Microscopic agglutination test (MAT): Serologic tests: early infection, antibiotic because there is no consistent serologic
reported as titer values; panel of serovars treatment, infecting serovar not included in cross-reactivity from one serovar to another.
varies among laboratories. test. Negative PCR/RT-PCR due to insufficient Serovars currently recommended for testing:
• Rapid IgM immunochromatographic lateral nucleic acid, chronic carrier state, antibiotic canicola, pomona, grippotyphosa, bratislava,
flow assay (IgM LFA), ELISA for antibody treatment, or occurrence of new strains/serovars icterohaemorrhagiae, hardjo, and autumnalis.
and PCR/RT-PCR: positive or negative • It may be useful to evaluate urine PCR and
result Next Diagnostic Steps to Consider serologic tests concurrently. Vaccination
if Levels Are Low interferes with IgM LFA test for shorter
Causes of Abnormally High Levels Repeat IgM LFA in 3-7 days or MAT titer or period of time (most are negative by 12-16
• MAT: active disease suggested by a fourfold ELISA in 1-2 weeks. PCR can detect infection weeks postvaccination) than ELISA or MAT
rise (paired serum samples 2-4 weeks apart). earlier than MAT or ELISA. (several months to ≥1 year).
A single titer of ≥ 1 : 800 in a nonvaccinated
dog, or dog vaccinated > 6 months prior, is Important Interspecies Differences AUTHOR: Patty J. Ewing, DVM, MS, DACVP
EDITOR: Lois Roth-Johnson, DVM, PhD, DACVP
also suggestive of infection. Vaccine-induced Cats are less susceptible than dogs to clinical
titers may be as high as 1 : 3200, but are disease, but may have positive titers.

Leukocyte Function Tests

Definition • Monocytes are tested for ability to phago- Specimen Collection and Handling
Tests of the in vitro ability of neutrophils, cytose particles and for cellular markers. The laboratory performing tests should be
monocytes, and lymphocytes to perform specific • Lymphocyte tests include proliferative contacted for specific sample collection and
functions unique to that cell type. These tests response to specific mitogens (i.e., lym- shipment handling; many function tests must
are not routinely available. For several tests, phocyte blastogenesis), expression of B- and be performed on freshly isolated cells.
the specific leukocyte must be freshly isolated T-cell receptors and other markers, and
from blood and tested within hours. quantitation of serum antibodies. Relative Cost: $$-$$$

Physiology Causes of Abnormally Low Levels Pearls
• Neutrophil function tests include measuring Though both congenital and acquired causes Animals with suspected congenital immuno-
response to chemotactic stimuli, oxidative of leukocyte dysfunction exist, these tests are deficiency states (e.g., pups or kittens with
burst and release of oxidative metabolites, most often performed in young dogs or cats recurrent infections) are best evaluated in a
phagocytosis and killing of bacteria, and with suspected congenital immunodeficiency referral setting.
expression of adhesion and activation cell (e.g., canine leukocyte adhesion defect, severe
markers (e.g., CD18). See p. 1260. combined immunodeficiency), or in a research AUTHOR: Stephen D. Gaunt, DVM, PhD, DACVP
EDITOR: Lois Roth-Johnson, DVM, PhD, DACVP
setting.

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