Collection And Transportation Of Specimens For Poultry Disease Diagnosis

Introduction:

The quality of interaction between clinicians and microbiologists has an enormous influence on the effectiveness of the laboratory service. An accurate diagnosis is based on the interpretation of both clinical and laboratory data. Investigation of disease is solely dependent on the quality and appropriateness of the specimens collected. The diagnosis depends on the skill and care with which the clinicians select, collect and transport the specimen to the laboratory. Clinical history, including the tentative diagnosis, should always accompany the specimen. If available, a detailed post-mortem report must also be sent. These set of information will help the microbiologist to select the most appropriate procedure and to furnish a meaningful interpretation of the results.

Specimens need to be collected for establishing a disease diagnosis or monitoring of vaccine response or surveillance. The knowledge of the pathogenesis of the infectious disease is the most important factor for determining the most suitable specimen. The samples need to be appropriate, and adequate in number and amount to provide a statistically valid result. Samples must be taken with care, to avoid undue stress or damage to the bird or danger to the operator. Careful consideration must be given to the collection, containment, and storage of the specimens, including biosafety measures to prevent spillage to the environment or exposure of other birds and humans.

Strict sterile precautions must be observed while collecting and handling materials for isolation. The chance of isolating a microbe depends critically on the knowledge, care, and attention of the veterinarian collecting the specimen. Specimens taken as a last resort after failed antibiotic therapy are invariably a waste of effort in case of bacterial disease. Having obtained suitable material, it must be carefully packaged, labeled, and transmitted to the laboratory by the fastest practicable method. Relevant shipping regulations must be followed. If material is sent to a laboratory of another country, the laboratory must be consulted in advance about its willingness to receive the material. All samples must be accompanied by a written note indicating the origin of the material, the relevant history, and the tests required.

General guidelines for the collection of specimens

Laboratory results are directly dependent on the mode of collection, preservation, and shipment of the specimen. Therefore, the samples are to be collected and handled in a manner that permits a high rate of recovery of the microorganisms present.

• Collect specimens from live sick or recently dead birds. Just prior to death and shortly thereafter, a number of intestinal bacteria may invade the host tissues. Some of the potential pathogens are difficult to assess when tissues have been invaded. Hence, for best results, fresh tissues must be collected as soon as feasible.
• Collect samples as aseptically as possible to avoid cross-contamination.
• Collect samples from affected sites as soon as the appearance of clinical signs. This is very important in the case of viral infections as the shedding of the virus is more pronounced during the early phase of infection. This holds true for enteric bacterial infection also.

• It is better to collect samples from clinical cases and in-contact birds. The later may shed large numbers of microorganisms.

• While investigating diseases of unknown cause, collect multiple different specimens that represent the different stages of the disease progression (e.g. the pre-clinical, early clinical, active clinical, chronically affected and convalescent phases).
• Collect samples from edge of the lesions and include some normal tissue. Microbial replication is more active at lesion’s edge.
• Collect specimens before treatment. Samples taken from treated birds are of little value.
• If the specimens are not collected in time and/or before the start of treatment, the same should be intimated to the laboratory so that the laboratory can opt for other molecular tests than isolation work.
• Specimen should be relevant to the suspected disease. If not, a wide range of tissues should be sent in order to avoid failure of isolation of significant organisms.
• Obtain a tentative diagnosis. If not, collect specimens for several disciplines such as bacteriological, mycological, virological, and pathological examination.
• Specimen on the dry swabs is liable to desiccation and hence more amounts of samples should be taken and sent to the laboratory as soon as possible. If needed, they can be sent in commercial swabs containing transport medium.
• Discuss the unexpected result with the laboratory.
• If a sample shows negative, it may not be considered due to intermittent shedding. Thus repeated sampling may yield actual results.

• The presence of commesal might not be considered unless pathogenic factors of such isolate are revealed.
• Submit a detailed history of the case along with samples.
• The samples in water-tight, screw-capped jars clearly indicating the tissue enclosed, animal identification and the date of collection are preferable.
• Send the samples at 4^oC and not frozen, if delay in transportation is expected.

Transportation of clinical materials

Specimens should always be placed in the plastic biohazard transport bag attached to the request form and the bag should be sealed. Multiple specimens should be transported in impervious transport containers (green transport bags) and should not be carried by hand or in plastic or paper bags. Specimens must not be sent in standard envelopes via the internal post.

Specimen packaging

It is the responsibility of all persons sending samples to the laboratory to adhere to national and international regulations ensuring that specimens sent to the laboratory do not present a risk to anyone coming in contact with them during transportation or on receipt in the laboratory.

Packaging Clinical materials:

• The packaging must be of good quality, and strong enough to withstand the shocks and loadings normally encountered during carriage.
• The packaging must consist of at least three components:

• A leakproof primary receptacle e.g. blood collection tube, MSU container;
• A secondary sealable package to enclose and protect the primary container(s), e.g. plastic specimen bag.
• Outer package: the secondary package is placed in an outer transport container with suitable cushioning that protects it and its contents from external influences such as physical damage and water while in transit.

Few points about antibacterial sensitivity test (ABST):

1.    First of all, it has to be clear that the outbreak must be due to bacteria alone. Or else it will lead to obfuscating result, as commensal bacteria/opportunistic pathogen might intercept.

2. The specimen such as heart blood swab shall have to be obtained from birds that have died not before three hours in order to prevent contaminating microbes.

3. It is not guaranteed that the bacterial growth obtained for performing ABST is always pure and the growth may even comprise the causative bacteria. In such cases, the outcome of the treatment based on ABST may not result in fruitful end.

4. It is pertinent to isolate the causative bacteria and then perform ABST, although this process may be time-consuming.

5. Bacteria such as streptococci or Avibacterium paragallinarum does not grow in the media used in regular ABST.

6. Despite taking all the care mentioned in the above points, there is a possibility of in vitro and in vivo differences which may lead to ineffective therapy.

7. Based upon the experience, a clinician must decide the correct choice of antibiotics when more than one antibiotic are found to be sensitive or intermediate sensitive in ABST.

Conclusion:

It can be concluded that the collection and despatch of specimens with correct labeling determine the efficiency of the laboratory data. The rapidity in collection and despatch of the specimens to the willing laboratory with good expertise is another factor that decides fruitful laboratory output. Moreover, it is mandatory to follow the Nation’s guidelines in the despatch of the specimens.