What is the recommended test kit for diagnosing infections in animals?

Recommended Test Kits for Diagnosing Animal Infections

Culture remains the gold standard for diagnosing infections in animals to avoid the limitations inherent in other testing methods. 1

Primary Diagnostic Approach

Culture-Based Testing (First-Line Recommendation)

Use culture as the primary diagnostic method, particularly for bacterial and chlamydial infections, as it avoids the significant limitations associated with antibody and antigen detection tests. 1

• For avian chlamydiosis (Chlamydia psittaci): Collect serial specimens for 3-5 consecutive days and pool them before culturing to reduce laboratory costs, since infected birds may not shed the organism daily 1
• Optimal specimens for culture: Liver and spleen tissue samples from necropsy provide the highest yield for organism isolation 1

When Culture is Not Feasible: Combination Testing Strategy

A single testing method is inadequate due to the diversity of immune responses across animal species—always use a combination of antibody- and antigen-detection methods when testing individual animals. 1

Specific Test Kit Recommendations by Method

Antibody Detection Tests

Direct Complement Fixation (CF):

• More sensitive than agglutination methods for detecting antibodies 1
• Critical limitation: False-negative results occur in small psittacine birds (budgerigars, young African grey parrots, lovebirds) 1
• High titers persist after treatment, complicating interpretation of subsequent tests 1
• Modified direct CF offers superior sensitivity compared to standard direct CF 1

Elementary-Body Agglutination (EBA):

• Commercially available and detects early infection 1
• Diagnostic thresholds: Titers >10 in budgerigars, cockatiels, and lovebirds; titers >20 in larger birds indicate recent infection 1
• Elevated titers persist after treatment completion 1

Antigen Detection Tests

ELISA Test Kits (e.g., QuickView®):

• Provide rapid results without requiring live, viable organisms 1
• Major limitation: Exact sensitivity and specificity for identifying C. psittaci are unknown 1
• False-positive results occur from cross-reacting antigens 1
• False-negative results occur with insufficient antigen present 1
• Critical interpretation rule: If a bird has a positive ELISA result but is clinically healthy, verify the bird is shedding antigen through organism isolation 1
• When a clinically ill bird has a negative ELISA result, you cannot exclude disease without further testing (culture, serology, or PCR). 1

For canine parvovirus (CPV) and canine distemper virus (CDV):

• Point-of-care ELISA test kits demonstrate high accuracy under field conditions: CPV sensitivity 92.3%, specificity 93.5%; CDV sensitivity 75.7%, specificity 91.8% 2
• CDV sensitivity improves to 94.0% when performed under laboratory conditions with an optical density meter 2

Immunofluorescent Antibody Tests (IFA):

• Use monoclonal or polyclonal antibodies with fluorescein-staining techniques and fluorescent microscopy 1
• Have similar advantages and disadvantages as ELISA 1

Molecular Testing (PCR)

Polymerase Chain Reaction (PCR):

• Promises high sensitivity and specificity for detecting target DNA sequences in specimens (choanal and cloacal swabs, blood) 1
• Critical caveat: Results from tests that have not been validated can be difficult to interpret 1
• For feline immunodeficiency virus (FIV): PCR sensitivity is 92% and specificity is 99% for detecting viral and proviral nucleic acid 3

Species-Specific Test Kit Performance

Feline Immunodeficiency Virus (FIV)

Use lateral flow immunochromatography test kits (Witness FeLV/FIV or Anigen Rapid FIV/FeLV) rather than lateral flow ELISA kits for FIV-vaccinated cats. 3, 4

• Witness and Anigen Rapid kits: 100% sensitivity, 98-100% specificity, and can accurately distinguish FIV-vaccinated from FIV-infected cats 3, 4
• Avoid SNAP FIV/FeLV Combo: Cannot determine if antibodies are from vaccination, natural infection, or both 3

Common Pitfalls to Avoid

Serologic Testing Interpretation:

• A positive serologic result only indicates past infection at some point, not necessarily active infection 1
• False-negative results occur in birds with acute infection sampled before seroconversion 1
• Antimicrobial treatment diminishes antibody response 1
• Confirmation requires: A >4-fold increase in titer of paired samples OR a combination of titer and antigen identification 1

Test Kit Validation:

• Never assume all commercial testing laboratories offer fully validated assays 5
• USDA licensure of test kits does not guarantee accurate answers to all serological questions 5
• Verify that testing laboratories or test kits are performing adequately before relying on results 5
• Interpret all test results within the context of their predictive values and pre-test probability of disease 5

Clinical Context:

• Compare serologic results with white blood cell counts and liver-enzyme activities when testing individual birds 1
• Consider signs of disease and flock/aviary history when interpreting results 1
• Always evaluate non-culture test results in conjunction with clinical findings 1