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General Principles & Sample Management
General Principles & Sample Management
• Antemortem Diagnosis: Primarily involves detecting immature parasite stages in feces, urine, saliva-sputum, or blood.
• Antemortem Diagnosis: Primarily involves detecting immature parasite stages in feces, urine, saliva-sputum, or blood.
• Small Animal Sample Collection:
• Small Animal Sample Collection:
◦ Must be as fresh as possible; dog owners should submit samples immediately after deposit.
◦ Must be as fresh as possible; dog owners should submit samples immediately after deposit.
◦ Litter boxes should be cleaned to ensure fresh cat samples.
◦ Litter boxes should be cleaned to ensure fresh cat samples.
◦ Unsuitable Samples: Those exposed to soil/grass (invaded by free-living nematodes) or kept at room temperature for >6 hours (eggs hatch, trophozoites degrade).
◦ Unsuitable Samples: Those exposed to soil/grass (invaded by free-living nematodes) or kept at room temperature for >6 hours (eggs hatch, trophozoites degrade).
• Storage: Refrigerate at 40 C if submission is delayed >2 hours.
• Storage: Refrigerate at 40 C if submission is delayed >2 hours.
• Rule-Out Protocol: A single negative result is insufficient due to sporadic shedding; three samples should be examined over 7–10 days.
• Rule-Out Protocol: A single negative result is insufficient due to sporadic shedding; three samples should be examined over 7–10 days.
• False Positives: Occur due to coprophagia (dogs) or hunting (ingesting prey parasites), leading to transit of eggs/larvae through the GI tract without actual infection.
• False Positives: Occur due to coprophagia (dogs) or hunting (ingesting prey parasites), leading to transit of eggs/larvae through the GI tract without actual infection.
Small Animal Fecal Examination Methods
Small Animal Fecal Examination Methods
• Simple Flotation:
• Simple Flotation:
◦ Uses high-specific-gravity (1.18–1.33) salt or sugar solutions in commercial kits.
◦ Uses high-specific-gravity (1.18–1.33) salt or sugar solutions in commercial kits.
◦ Parasites float to the surface and attach to a coverslip over 5–10 minutes.
◦ Parasites float to the surface and attach to a coverslip over 5–10 minutes.
• Centrifugal Flotation:
• Centrifugal Flotation:
◦ Superior to simple flotation for detecting most parasites, especially whipworm or capillarid eggs.
◦ Superior to simple flotation for detecting most parasites, especially whipworm or capillarid eggs.
◦ Best Practice: Centrifugation with zinc sulfate (ZnSO4) is the best option for Giardia duodenalis cysts.
◦ Best Practice: Centrifugation with zinc sulfate (ZnSO4) is the best option for Giardia duodenalis cysts.
• Direct Smear:
• Direct Smear:
◦ Inexpensive; a tiny speck of feces is mixed with saline.
◦ Inexpensive; a tiny speck of feces is mixed with saline.
◦ Method of Choice: Detecting protozoal trophozoites (G. duodenalis, T. blagburni); requires very fresh feces (within 20 minutes).
◦ Method of Choice: Detecting protozoal trophozoites (G. duodenalis, T. blagburni); requires very fresh feces (within 20 minutes).
◦ Limitation: High rate of false negatives due to small sample size.
◦ Limitation: High rate of false negatives due to small sample size.
• Simple Sedimentation:
• Simple Sedimentation:
◦ Method of Choice: Operculate eggs of trematodes (flukes) and pseudophyllidean cestodes (tapeworms).
◦ Method of Choice: Operculate eggs of trematodes (flukes) and pseudophyllidean cestodes (tapeworms).
◦ Specific Protocol: Use saline instead of water for Heterobilharzia americana to prevent eggs from hatching.
◦ Specific Protocol: Use saline instead of water for Heterobilharzia americana to prevent eggs from hatching.
• Baermann Examination:
• Baermann Examination:
◦ Method of Choice: Detecting active nematode larvae (lungworms and Strongyloides stercoralis).
◦ Method of Choice: Detecting active nematode larvae (lungworms and Strongyloides stercoralis).
◦ Uses a funnel with hot tap water; larvae swim out of the fecal sling into the tubing.
◦ Uses a funnel with hot tap water; larvae swim out of the fecal sling into the tubing.
◦ Exception: Does not reliably detect Filaroides hirthi or Oslerus osleri (larvae lack motility).
◦ Exception: Does not reliably detect Filaroides hirthi or Oslerus osleri (larvae lack motility).
• Immunological (ELISA):
• Immunological (ELISA):
◦ Commercially available for G. duodenalis; more sensitive than a single centrifugal flotation.
◦ Commercially available for G. duodenalis; more sensitive than a single centrifugal flotation.
◦ Limitation: Stays positive post-treatment; unsuitable for post-treatment monitoring or re-entry into day care.
◦ Limitation: Stays positive post-treatment; unsuitable for post-treatment monitoring or re-entry into day care.
Other Small Animal Diagnostics:
Other Small Animal Diagnostics:
• Urine: Used to detect eggs of Pearsonema plica (Capillaria plica), Pearsonema feliscati, and Dioctophyme renale.
• Urine: Used to detect eggs of Pearsonema plica (Capillaria plica), Pearsonema feliscati, and Dioctophyme renale.
• Saliva-Sputum/Lavage: Recommended for F. hirthi and O. osleri using transtracheal wash or bronchoalveolar lavage.
• Saliva-Sputum/Lavage: Recommended for F. hirthi and O. osleri using transtracheal wash or bronchoalveolar lavage.
• Blood (Heartworm - D. immitis):
• Blood (Heartworm - D. immitis):
◦ Standard Protocol: Combination of Antigen detection (detects adult females) and Microfilaria testing.
◦ Standard Protocol: Combination of Antigen detection (detects adult females) and Microfilaria testing.
◦ Antigen Limitations: False negatives occur if tested <7 months post-exposure or if antigen is sequestered in antibody-antigen complexes.
◦ Antigen Limitations: False negatives occur if tested <7 months post-exposure or if antigen is sequestered in antibody-antigen complexes.
◦ Microfilaria Tests: Modified Knott's (can differentiate D. immitis from nonpathogenic A. reconditum) and the Filter test.
◦ Microfilaria Tests: Modified Knott's (can differentiate D. immitis from nonpathogenic A. reconditum) and the Filter test.
◦ Species Note: Cats require antigen + antibody testing; microfilaria tests are not recommended for cats.
◦ Species Note: Cats require antigen + antibody testing; microfilaria tests are not recommended for cats.
• Blood (Protozoa): Babesia spp, Cytauxzoon felis, and Hepatozoon canis detected via Giemsa-stained blood smears (acute phase) or molecular methods (chronic phase).
• Blood (Protozoa): Babesia spp, Cytauxzoon felis, and Hepatozoon canis detected via Giemsa-stained blood smears (acute phase) or molecular methods (chronic phase).
Horse and Production Animal Diagnosis
Horse and Production Animal Diagnosis
• Sample Collection: Preferably collected from the rectum.
• Sample Collection: Preferably collected from the rectum.
• Herd Testing: Collect from a minimum of 10 animals; samples can be combined into a single composite herd sample.
• Herd Testing: Collect from a minimum of 10 animals; samples can be combined into a single composite herd sample.
• Quantitative Fecal Egg Counts (FEC): Cornerstone for detecting anthelmintic resistance.
• Quantitative Fecal Egg Counts (FEC): Cornerstone for detecting anthelmintic resistance.
◦ Cornell-Wisconsin: Most sensitive; used for low expected counts (adult cattle/camelids).
◦ Cornell-Wisconsin: Most sensitive; used for low expected counts (adult cattle/camelids).
◦ McMaster/Mini-FLOTAC: Recommended for high counts (>100 EPG); McMaster uses a gridded chamber to estimate EPG.
◦ McMaster/Mini-FLOTAC: Recommended for high counts (>100 EPG); McMaster uses a gridded chamber to estimate EPG.
• Treatment Thresholds:
• Treatment Thresholds:
◦ Horses: ≥250 EPG.
◦ Horses: ≥250 EPG.
◦ Sheep/Goats: >5,000 EPG.
◦ Sheep/Goats: >5,000 EPG.
◦ Cattle: >50 reflects moderate infection; >500 reflects heavy burden.
◦ Cattle: >50 reflects moderate infection; >500 reflects heavy burden.
• Fluke Quantification: Requires quantitative fecal sedimentation using soapy water.
• Fluke Quantification: Requires quantitative fecal sedimentation using soapy water.
Morphological Identification Tools:
Morphological Identification Tools:
• Ocular Micrometer: A critical, inexpensive scale fitted into the microscope eyepiece to measure parasite size, allowing for accurate characterization.
• Ocular Micrometer: A critical, inexpensive scale fitted into the microscope eyepiece to measure parasite size, allowing for accurate characterization.
• Expertise: Morphological identification is a subjective, acquired skill requiring high levels of training and experience.
• Expertise: Morphological identification is a subjective, acquired skill requiring high levels of training and experience.
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