Model Answer
0 min readIntroduction
Accurate and timely laboratory diagnosis is paramount in controlling and eradicating animal diseases. Rabies, a viral neurotropic disease, Theileriosis, a tick-borne protozoal disease, and Newcastle Disease (ND), a highly contagious avian disease, pose significant threats to both animal and human health. Effective diagnosis hinges on appropriate sample collection techniques, which directly impact the reliability of subsequent laboratory confirmation. This response will detail the essential steps involved in collecting laboratory material for confirmation of these three diseases, emphasizing the critical factors that influence diagnostic accuracy.
Rabies Diagnosis: Sample Collection
Rabies is a fatal viral disease affecting mammals. Post-mortem diagnosis is crucial for public health surveillance and confirmation.
- Sample Types: Brain tissue (preferred), spinal cord, peripheral nerve.
- Collection Technique: Ideally collected within 24 hours post-mortem. If delayed, samples should be frozen. A small piece (approximately 1 cm3) is sufficient.
- Storage: Samples should be preserved in 10% formalin solution for transportation. Freezing is acceptable if formalin is unavailable.
- Considerations: Autolysis (tissue breakdown) significantly impacts diagnostic sensitivity. Prompt preservation is essential.
Theileriosis Diagnosis: Sample Collection
Theileriosis is a tick-borne protozoal disease affecting livestock, particularly cattle. Early and accurate diagnosis enables prompt treatment and control measures.
- Sample Types: Peripheral blood (EDTA-anticoagulated), bone marrow (aspirate), lymph node aspirate.
- Collection Technique: Blood collection should be performed as early as possible after suspicion. Bone marrow aspirates are more sensitive than blood smears.
- Storage: Blood samples should be refrigerated if not processed immediately. Bone marrow should be sent fresh to the laboratory.
- Considerations: Parasite density can vary depending on the stage of infection and host immune response. Multiple samples from different sites may be necessary.
Newcastle Disease (ND) Diagnosis: Sample Collection
Newcastle Disease is a highly contagious viral disease affecting birds. Rapid diagnosis is essential to prevent widespread outbreaks.
- Sample Types: Chorioallantoic membrane (CAM) from embryonated eggs (for virus isolation), tracheal/cloacal swabs, kidney/brain tissue (for PCR).
- Collection Technique: Swabs should be collected from the choana, trachea, and cloaca. Tissue samples should be collected from birds showing clinical signs. CAM inoculation is crucial for virus isolation.
- Storage: Swabs should be placed in viral transport medium (VTM) and refrigerated. Tissue samples should be frozen.
- Considerations: Viral shedding varies with disease severity and age of the bird. Proper biosecurity measures are essential during sample collection to prevent further spread.
Summary Table: Sample Collection for Diagnostic Confirmation
| Disease | Sample Type | Collection Timing | Storage | Key Considerations |
|---|---|---|---|---|
| Rabies | Brain tissue | Within 24 hours post-mortem | 10% Formalin or Frozen | Prevent Autolysis |
| Theileriosis | Peripheral Blood | Early after suspicion | Refrigerated | Parasite Density Variation |
| Newcastle Disease | Tracheal/Cloacal Swab | During active shedding | Viral Transport Medium | Biosecurity Measures |
Laboratory Confirmation Techniques (Brief Overview)
Collected samples undergo various laboratory tests for confirmation:
- Rabies: Direct fluorescent antibody test (FAT), Reverse transcription PCR (RT-PCR).
- Theileriosis: Giemsa staining of blood smears, PCR.
- Newcastle Disease: Virus isolation in embryonated eggs, RT-PCR, ELISA.
Conclusion
In conclusion, the accurate collection and preservation of laboratory material are foundational to confirming rabies, theileriosis, and Newcastle Disease. Adherence to established protocols, considering factors like timing, storage, and potential pitfalls, is critical for obtaining reliable diagnostic results. Continued investment in laboratory infrastructure, training of personnel, and improved biosecurity measures are essential for effective disease control and prevention in both animal and human populations.
Answer Length
This is a comprehensive model answer for learning purposes and may exceed the word limit. In the exam, always adhere to the prescribed word count.