Collection and submission of diagnostic specimens

1. Collection and submission of diagnostic specimens

2. Before you start! • A complete case history, including tentative diagnosis, should be submitted to the lab with the specimens before lab investigation is undertaken.

3. General guidelines • Specimens should be taken from living, or recently dead animals. • It is useful to collect samples from intact animals. • Samples should be obtained from the edge of the lesion and include some normal tissue. • It is important to collect samples as aseptically as possible. • Specimens should always be collected before the administration of any form of treatment. • It is always better to collect various range of samples. • Samples must be sent individually in water-tight bags (or containers). • Make the sample properly marked. Indicate the tissue enclosed, animal species, date (and time) of collection. Also indicate the discipline the sample is going to; i.e. microbiology lab. • If transportation to the lab is delayed, samples should be kept at 4˚C.

4. Most commonly submitted samples • Abortion cases • Mastatic milk samples • Abscesses • Specimens for anaerobic cultures • Urine samples • Skin lesions • Blood cultures

5. Abortion cases • A whole foetus should be submitted if possible. If not possible, abomasal contents, liver, lung, and a sample from any gross lesion should be submitted. • A piece of obviously affected placenta that includes at least two cotyledons. • Uterine discharge. • Serum from the dam for serological tests. • A piece of placenta in 10% formalin for histopathology.

6. Mastatic milk samples • Samples from treated animals are of no use. • Wipe the teats vigorously using 70% ethanol in cotton wool, paying special attention to teat sphincters, starting from the two furthest teats. • The first squirt of milk from each teat should be discarded. • The milk should be first collected from the two near teats first. Why?!

7. Abscesses • If possible, 3 ml of pus should be collected, together with scrapings from the wall of the abscess. • Pus from recently formed abscesses will yield the best bacterial culture.

8. Specimens for anaerobic cultures • Obligate anaerobes do NOT live more than 20 minutes at the presence of oxygen. • Specimens from animals that have been dead for more than 4 hours are not suitable for bacteriology. • Bone marrow is good specimen to collect, because it is the last tissue to be invaded by contaminants. • To do so, a piece of rib is stripped of the periosteum could be submitted to the lab. • Other acceptable samples includes blocks of tissues (4 cm3), placed in sterile closed containers. • For liquid exudates, the sample can be collected in a disposable syringe. • In case enterotoxaemia is suspected, 20 ml of ileal contents should be submitted. If no sterile container is around, a piece of ileum with its content, tied from both side is acceptable.

9. Urine samples • For bacteriological procedures, the preferred methods of collection are cytocentesis by catheter or mid-stream urine sample. • Clinical bacteriuria is indicated by the presence of 105 bacteria per ml of urine. • Between 104 and 105 per ml is suggestive of infection. • Less than 104 per ml is not significant.

10. Skin lesions • If intact pustules or vesicles are present, the surface should be disinfected with 70% ethanol, allowed to dry, and material aspirated with a sterile syringe. • In cases where ringworm is suspected, hair should be plucked from the lesion and the edge scraped with blunt scalpel blade until blood begins to ooze. • Plucked hair, skin scrapings, including the scalpel blade, and any scab material that is present should be submitted to the lab.

11. Blood samples • Strict aseptic precautions should be taken. • The area over the venepuncture must be shaved, cleaned with a detergent, allowed to dry, and disinfected with 70% ethanol, and left for 30 seconds. • As bacteraemia can be intermittent, it is advised to take more than one sample within 24 hours. • The blood should be added aseptically to one of the special commercial blood culture bottles.

12. Interpretation of diagnostic results Points to be considered:

13. The disposal of clinical wastes • Place culture wastes in an autoclavable bag, followed by autoclaving. • Enclose clinical wastes in a strong leak-proof plastic bag for incineration. • The least satisfactory option is to soak the waste in a suitable disinfectant for at least 48 hours before the contents can be safely discarded.