With the closure of government veterinary laboratories and reduced carcass submission rates year-on-year, there is an opportunity for veterinary practices to offer an in-house, local farmer-focused postmortem service (Norquay et al, 2020). While performing necropsies at a fallen stock collection centre is possible, the facilities there are rarely ideal and as such limit the extent of the postmortem examination possible. In addition to servicing a client need, and contributing to farm health plans, veterinary practice postmortem examinations can contribute to national animal health passive or enhanced passive surveillance (although this requires a formalised infrastructure). Postmortem examinations performed by veterinary practitioners are towards the top of the surveillance pyramid.
A recent study of the reasons why farmers do not bring carcasses to a veterinary diagnostic laboratory concluded that cost is not the primary factor (McFarland et al, 2020). The farmer's veterinary practitioner, type of incident, logistical issues, herd size and distance from the laboratory were the primary factors.
The main benefits of an in-house postmortem service to clients should be convenience, rapid reporting and dealing with the practice which was possibly already involved in the herd or flock problem. There are, however, drawbacks with inexperienced practitioners; subtle, but significant pathology may be missed and unnecessary costs may be incurred by the farmer if samples are sent for further testing when not warranted. It is for these reasons that continuing professional development (CPD) on gross pathology should be encouraged for general practitioners to be able to provide a high quality postmortem examination, with appropriate testing.
Carcass submission
Clients should be able to deliver carcasses along with an appropriate history/submission form, directly to the postmortem facility without bringing them through the practice building/s. Carcasses (and placentae) should be transported in a container that prevents contamination of the environment and is also predator-proof. Double bagging in a sturdy, cable–tied plastic bag (not bin bags), or containment in a plastic box is recommended (Figure 1). All carcasses, including aborted fetuses, should be identified by an ear tag. Although there is no official requirement to identify beef calves until 28 days old in the UK, farmers should be encouraged to identify these in a similar manner. Carcasses that are severely autolysed (as a result of death in utero or prolonged death-to submission interval) or predated are discouraged as they are not likely to yield useful diagnostic information for the client. For out of office hours' submissions, a secure drop box should be provided at the postmortem room entrance beside a footbath. The cost of single or multiple postmortems, without ancillary testing, should be advised to the client in advance of carcass submission.
Postmortem facility
The setting up of a postmortem examination facility should be very achievable in most rural veterinary practices, with minimal effort and cost. The work generated from such a facility and the knock-on work from future investigations, herd health work and calls because of improved diagnostic rates should more than cover the service costings.
Postmortem examinations should be performed in an area that is easily washed down and disinfected, and ideally in a separate area/building from the practice office (Figure 2). Space in general practice is often limited so the use of a dual-purpose room, perhaps for examination of live farm animals, may also be suitable provided strict biosecurity is adhered to. It is essential that there is direct access to the facility through an external door, to prevent cross-contamination of other practice facilities (Figure 3). Consideration of the external environment should also be given to avoid contamination with potentially zoonotic and infectious material. Washing and disinfection facilities should be made available to all vehicles delivering and collecting carcasses. Care should be taken with effluent from clean ups, which may potentially contaminate public sewars. Solid traps may be required for drainage systems.
Equipment
The majority of equipment required to set up a postmortem facility should already be present in a veterinary practice, with only a small amount of equipment required to be purchased. All equipment used in the postmortem room should only be used here, not else-where. A list of essential and useful equipment is shown in Box 1.
Box 1.Equipment needed in a postmortem facility (items possibly need to purchase in bold)
- Knives
- Knife sharpening kit/steel (Figure 4)
- Scissors
- Saw/loppers/secateurs
- Forceps (large, rat tooth)
- Vice (with modified jaws) (Figure 5)
- Centrifuge
- Dictaphone
- Organ trays/cutting boards
- Camera
- Measuring tape/ruler
- Weighing scale
- Biowaste bins
- Paper towel dispenser
- Storage for gowns, masks, sample containers, swabs, etc
- Hazardous chemical storage box
- Safety goggles/face shield
- Blow torch
- Fridge-freezer
- Skip for carcass storage pre-disposal
Postmortem table
While postmortem examinations can be performed on the floor, ideally they should be done on a washable table with good drainage via a central hole or open sides. For permanent postmortem facilities to conform to the Manual Handling Operations Regulations 1992, an adjustable-height table (Figure 6) or one that prevents poor posture would need to be purchased (Health and Safety Executive, 1992). Where several individuals may be performing postmortem examinations, a variable height table is recommended.
Hoist
There are various types of hoist available, ranging from pulley systems to electric hoists, some of which can incorporate a weighing scale (Figure 7). In rural veterinary practices, work in isolation is a common occurrence, and although installation of a hoist is not essential it greatly facilitates single person postmortems. A hoist can both aid in lifting of larger carcasses on to the table and suspension of the carcass for disposal into a plastic bag/container after completion of the postmortem examination. Additionally, in compliance with Manual Handling Operations Regulations (1992), employers are required to reduce and control the risks from manual handling. All lifting equipment is required to be fit for purpose and properly inspected according to the Lifting Operations Lifting Equipment Regulations 1998 (Health and Safety Executive, 1998).
Weighing scales
A weighing scale (walk-on or incorporated in the hoist) for carcasses should be within the postmortem facility itself, provided that it is water-resistant. In an ideal situation, the weighing scale should be part of the lifting aid. An additional smaller, bench-top, scale may be used to weigh organs, for example the thyroid gland. Note, all scales need to be calibrated at least annually.
Consumables
A list of consumables is shown in Box 2. Almost all of these items will already be available in the practice. Similar to the equipment, consumables for the postmortem room should not be shared with other practice activities to prevent potential cross-contamination.
Box 2.Consumables needed in a postmortem facility
- Scalpel blades (or better, disposable scalpels)
- Needles and needle holders
- Sharps containers
- Specimen containers (e.g. Universal 30 ml and larger 200 ml, sterile, screw-top bio-bottles, whirl-pak bags and vaccutainers)
- Buffered neutral formalin (10%)
- Swabs (e.g. Amies charcoal, flocked nylon, dry cotton)
- Gowns, gloves, masks
- Hand sanitizer
- Paper towels
- Disinfectant
- Bio-waste bags
- Laboratory submission forms
- Padded envelopes
Health and safety
Before moving a carcass, any indication of a notifiable disease or the need for an anthrax smear should be confirmed. Appropriate personal protective equipment (PPE) such as disposable gloves, cut-resistant gloves, gowns, masks and safety goggles, waterproof trousers and steel-toe-cap wellington boots should be worn at all times in the postmortem room and should be disinfected (or disposed of) at the end of each postmortem examination and not worn elsewhere. Particular care should be taken to ensure that potentially infectious or zoonotic material is handled in a safe manner, especially where there are pregnant women on site (Box 3). Care should be taken both in using (e.g. knives — cut proof gloves should be worn) and disposing (e.g. scalpels) of sharps. Hazardous chemicals need to be stored in an appropriate safe box.
Box 3.Zoonotic microbes potentially contractible from postmortem submissions (carcasses, placentae, fluids)
- Brucella abortus
- Campylobacter foetus spp.
- Chlamydia abortus
- Coxiella burnetti
- Cryptosporidium parvum
- Escherichia coli (VTEC)
- Leptospira spp.
- Listeria monocytogenes
- Salmonella spp.
- Toxoplasma gondii
Health and safety signage should be prominent in the postmortem room. A hand washing facility should be available in or near the postmortem room. Correct procedures need to be adopted when lifting heavy carcasses to avoid back injuries — use of a hoist is highly recommended. Working alone in the post-mortem facility is inadvisable given the risk of injury. Formal risk assessments should be conducted in all veterinary postmortem facilities and relevant legislation adhered to. Seeking advice from local government postmortem facilities should be considered and appropriate standard operating procedures should be followed.
The postmortem examination
Postmortem examinations are not considered an urgent call. However, the longer an animal is dead, the lower its diagnostic value. Postmortem examinations should be performed within 48 hours of death, sooner in hot weather, and should follow a standard protocol (Mee, 2016). The knowledge and experience of the veterinary surgeon conducting the postmortem exmination is critical to the quality of the outcome. Depending on pre-existing knowledge and experience, consultation with Animal and Plant Health Agency (APHA)/Scottish Agricultural College (SAC) regional laboratories/private laboratories is highly recommended for those performing postmortem examinations, in particular where they encounter unusual findings. Multiple practitioner postmortem examinations for a herd/flock problem are preferable to an individual laboratory postmortem. With an in-house facility a complete postmortem examination can be conducted quickly yielding much more information than an on-farm ‘key hole/stitch up’ postmortem.
Recording of findings
It is useful to have a method of recording gross findings while the examination is performed (‘say what you see’). The recording method will depend on personal preference with mobile phone, dictaphone or white board being suitable methods. In future apps may facilitate direct-to-tablet information capture (e.g. PathPal developed by vHive at the University of Surrey). The use of a high-quality camera such as available on a mobile phone, is beneficial to record any significant or unusual findings. These images can then be used for reporting to the farmer, and also for referral for specialist advice (remote digital necropsy). If photography is an interest, a photography studio light box is worth investing in to improve the quality of the images collected. Ideally, a one-page pro-forma report format which includes practice logo, client details, animal ID, clinical history, gross postmortem examination findings, photos, lab findings and diagnosis should be used both for reporting to farmers (for their records), for looking back on previous postmortem examinations and for auditing results. Consideration should be given to creating a database of all postmortem examinations done, and all diagnoses made, but this must be user-friendly if it is to work.
Sample collection
Testing of microbiology samples can be expensive, samples may be contaminated and results may not change the course of action, except where an infection is suspected. Hence, supplementary testing should only be conducted when it is likely to add significantly to the postmortem examination outcome.
Samples for microbiology should be collected once the carcass is opened to reduce contamination from spilled body fluids. To reduce contamination when collecting abomasal fluid samples, the serosa may be briefly seared (using a heated spatula or scalpel blade), flamed (using a blow torch) or disinfected (using an alcohol or antiseptic swab/moist wipe) (Figure 8). Swabs for polymerase chain reaction (PCR) testing should have non-wooden (lignin) stems (e.g. plastic, metal). All non-carcass-side testing and associated costs should be agreed with clients in advance of sample submission to external laboratories.
Washing down
It is essential that a hosepipe, brush and buckets are available within the room for washing down and disinfecting the table after each postmortem examination and the floor after all examinations. Drainage requirements will depend on local rules. A broad-spectrum, fast-acting, low-hazard disinfectant should be used on equipment and surfaces.
Sample storage and postage
Sample storage
Correct sample handling and storage play an important role in achieving high diagnostic rates. Failure to store microbiology samples correctly or submission delay may result in overgrowth of non-pathogenic bacteria (e.g. Proteus spp.), which obscure the growth of significant bacteria. The handling and storage of samples is dependent on the sample matrix and the laboratory testing planned. All tissue and fluid samples should be stored in a leak-proof container.
Samples for microbiological culture (e.g. abomasal fluid, organ samples, swabs) should be stored at 4°C in a temperature-monitored practice refrigerator. This should be easily achievable in rural practices, without the need to purchase expensive equipment.
Tissues (e.g. the spleen for bovine viral diarrhoea virus), fluids or swabs for PCR testing should be stored at −20°C.
Samples for histopathology should be stored in formalin at room temperature at a ratio of 1:10 tissue: formalin. Tissue samples do not need to exceed the volume of a histopathology cassette (3.5 x 2.5 x 0.5 cm); this facilitates rapid fixation and processing. However, brains should be stored whole for a minimum of 2 weeks before postage (with formalin removed) in large (>200 ml) screwtop pots to ensure they are fully fixed.
Samples for serology (e.g. fetal fluid/blood) can be stored at room temperature if they are to be posted that/next day or in a freezer if stored over a weekend or holiday period (e.g. Christmas).
Sample postage
An appropriate laboratory should be used for submission. Stored brains should be removed from the formalin and posted whole in a large pot. Other fixed tissues can be posted along with fresh tissue in 100 ml leak-proof sample pots. All pots should be fully sealed with insulation tape to prevent leakage during postage.
Samples should only be posted on days of the week that ensure next day delivery at the laboratory. Samples collected on Thursday afternoons, Fridays, Saturdays and Sundays should be stored until transportation to the laboratory on the Monday. Samples should be posted according to the IATA Dangerous Goods Regulations (DGR, 53rd Edition, 2012: https://www.iata.org/en/publications/store/infectious-substances-shipping-guidelines/?_ga=2.54456171.296413643.1623152619-652442612.1623152619).
All samples should be accompanied by a standard laboratory submission form, case history and findings of the postmortem examination. For smaller specimens (e.g. from aborted fetuses), a purpose-designed sample transport cardboard box can be used for postage (Figure 9).
Carcass and waste disposal
Carcasses/placentae should be disposed of according to local regulations. In most cases, this will involve collection by fallen stock companies or disposal by incineration. Hence, this biological material will need to be securely stored on the premises until collection. Suitable storage facilities include chest freezers or leak-proof/scavenger-proof outdoor containers, which can be easily cleaned and disinfected. In some circumstances, open carcasses collected from a veterinary practice may be considered as clinical waste and should be disposed of accordingly.
Filled sharps and clinical waste biobags need to be disposed of separately according to regulations.
Reporting results
Ideally, farmers should be provided with (preliminary) results within 24–48 hours of carcass submission (rapid turn around time is one of the main advantages of an in-house postmortem service) and advised if laboratory results are outstanding, particularly where multiple stock losses have occurred. As with government laboratory postmortem examinations, a final written report should also be provided.
Conclusion
Setting up a postmortem examination service in a farm animal practice is feasible with even limited buildings and equipment. But initial investment in good quality facilities will pay off in the long term in the quality and ease of performing the work and in enhancing further client engagement.
KEY POINTS
- A postmortem examination service should be an integral part of a herd or flock health plan.
- An in-house postmortem room offers convenient facilities for both veterinary practitioners and client.
- Veterinary practitioners performing postmortem examinations need to both acquire and maintain this expertise.
- Carcasses/placentae need to be transported to the facility in a biosecure container.
- The postmortem examination room needs to be easily washed down.
- Good knives and a knife sharpening kit are essential.
- An adjustable-height postmortem table is recommended.
- A hoist greatly facilitates one person postmortem work.
- Health and safety needs to be considered.
- Samples should be stored at the appropriate temperature.
- Leak-proof containers are essential when posting samples.