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Porcine Quick Guides

Quick Guides to sample selection for diagnosis of common conditions

The following ‘Quick Guides’ have been prepared to assist you in sample selection when a particular system is affected.  You may wish to provide copies to your technicians and keep copies at strategic locations for reference.

Porcine Abortion

Specimens to submit: Entire fetuses with placenta, minimally contaminated, fresh/chilled are preferred specimens. Do NOT freeze. Send 4-6 representative fresh fetuses and all mummified fetuses. Alternatively, remove the following tissues from 3 fetuses per litter:

Thoracic fluid 0.25 - 1 ml per aborted pig, may pool within litter for PRRS virus, PCV2

Brain

1/2 brain, fresh/chilled and formalin-fixed

Heart

1/2 of organ fresh/chilled, 1/2 cm slice formalin-fixed

Kidney

Fresh/chilled, formalin-fixed (1/2 cm slices)

Liver

Fresh/chilled (1/3 of organ), formalin-fixed(1/2 cm slice)

Lung

Fresh/chilled (1 entire lung), plus formalin-fixed (1/2 cm slice)

Stomach contents 1-3 ml in sterile syringe or tube, fresh/chilled

Placenta

Fresh/chilled and several pieces formalin-fixed

Umbilicus

Formalin-fixed, several 1/2 cm slices

Sow serum Optional, see notes on abortion serology. 1-3 ml from affected sows

SAMPLING TECHNIQUES

  1. Do NOT freeze tissue.
  2. Submit placenta whenever possible
  3. Thorough investigation of abortion should include serology. Submit dam's sera. Retain 1/2 of sample frozen.

AGENTS DETECTED BY ROUTINE EXAMINATION

Bacteria

Arcanobacterium pyogenes, Bacillus spp., Brucella spp., E. coli, Erysipelothrix, Salmonella spp., Streptococcus spp., etc

Viruses

PRRSV, PCV2, PRV, parvovirus (see comments)

AGENTS REQUIRING SPECIAL TESTS (BY REQUEST)

Leptospira

If leptospirosis is suspected, extra effort should be made to deliver freshly aborted, chilled fetuses directly to the lab for PCR or FA tests which are performed on kidney or IHC. Serology on sow sera is probably the most reliable method for diagnosing leptospirosis.

PRRS virus

PRRS virus is not present on all aborted fetuses.  Virus isolation is not routinely conducted but PCR on pooled tissues or thoracic fluids is routine. Histopath may occasionally demonstrate lesions suggestive of PRRS virus in umbilical cords, lungs, heart or other tissues. Preferred samples are lung or serum from weakborn littermates or from pigs that develop pneumonia shortly after birth. PCR on serum from sick sows is often valuable. A serologic survey of the sow herd may be useful, but may be difficult to interpret in PRRS-endemic or vaccinated herds.

Toxicosis

Carbon monoxide (heart blood in EDTA; clotted heart blood or thoracic fluid as second choice).

COMMENTS

  • Parvovirus and PCV2 usually do not cause abortion but may be present in mummified fetuses.
  • Mummified fetuses may harbor parvovirus, PCV2 or PRRSV. Lungs and hearts from mummified fetuses are useful for detection of these viruses by PCR. Fetal serology may aid in the diagnosis of porcine parvovirus, PCV2, Leptospira and PRRSV. 
  • See abortion serology notes

 

Porcine Central Nervous System Disorders

Specimens to submit: One or more acutely affected live pigs. Alternatively, tissues from field necropsy should include:

Brain (including brain stem)

Swab of brain stem and base of cerebellum (for bacterial culture)

1/2 brain divided longitudinally, fresh/chilled

1/2 brain, formalin-fixed

Intestine

Optional, edema disease.

One 10-15 cm slice of ileum and jejunum, fresh/chilled

Several 1/2 cm slices of ileum, formalin-fixed

Spinal cord

Optional, locomotor problems.

Entire carcass or vertebral column, fresh/chilled

Dissected cord, fresh/chilled

Cross-sections (1/2 cm slices) of cord from 4-5 levels, formalin-fixed

Spleen

Fresh/chilled and formalin-fixed

Tonsil

Fresh/chilled and formalin-fixed

SAMPLING TECHNIQUES

  1. Entire head can be submitted. Chill before shipment if possible.
  2. Do NOT freeze fresh brain or head.
  3. Fresh half of brain should be packed carefully to avoid crushing.
  4. Fixed half of brain should be incised transversely (not longitudinally) into the ventricle to aid in fixation if brain is large.
  5. CSF can be collected prior to removing the skull. When a bacterial meningitis is suspected, CSF is an excellent sample as there is less opportunity for contamination compared to most methods of opening the skull.

AGENTS DETECTED BY ROUTINE EXAMINATION

Bacteria

Streptococcus suis, Haemophilus parasuis, Arcanobacterium pyogenes, E. coli (intestine, edema disease)

Viruses

Pseudorabies virus, PRRS virus, PCV2

Non-infectious

Water deprivation/sodium toxicity

AGENTS REQUIRING SPECIAL TESTS (BY REQUEST)

Toxicosis

Selenium (liver and spinal cord - lumbar intumescence, fresh/chilled)

Organophosphate (whole blood in EDTA, brain, stomach contents, fresh/chilled)

Viruses

Rabies (FA on brain); other viruses (e.g. HEV, porcine Teschovirus, paramyxovirus, herpesviruses detected by (PCR or VI on fresh/chilled brain)

COMMENTS

  • Cerebellum and brain stem are affected by most infectious causes of CNS disease and should always be included in submitted samples.
  • Many toxic causes of CNS disease do not induce lesions in the brain and must be diagnosed by analysis of other tissues. For most toxicoses, submission of stomach contents, liver, kidney, feed, water, and whole blood (in EDTA), as well as brain, would include the tissues necessary for diagnosis.
  • Spinal cord is essential for diagnosis of causes of posterior pareses or paralysis.

 

 Porcine Enteritis - Nursing Pigs

Specimens to submit: The best specimens are acutely-ill (<24 hours) live untreated pig(s). Alternatively, necropsy of euthanized pig(s) with intestines collected in formalin within 10 minutes of death.

Colon/cecum contents

2-10 ml fresh/chilled

Colon and cecum

Entire organ, fresh/chilled

Several 1 cm pieces, formalin-fixed

Ileum

10-15 cm segments, fresh/chilled

Three 1 cm pieces, formalin-fixed

Jejunum

10-15 cm segments, fresh/chilled

Three 1 cm pieces, formalin-fixed

Lesions

10-15 cm segments, fresh/chilled

Several 1 cm pieces, formalin-fixed

Samples removed at necropsy in the field are better than a whole dead pig submitted to the lab.

SAMPLING TECHNIQUES

  1. Samples must be taken as soon after death as possible (within minutes).
  2. Intestines do not need to be tied off at the ends.
  3. Flush intestinal segments for histopathologic examination with formalin and drop in fixative. Or, gently open ends of 1/2" segments with a scissors or forceps to expose mucosa as immersed.
  4. Pool all formalin-fixed tissues from each pig in one bag; individual pigs can be pooled or kept separate as desired. Package fresh intestines separately from other tissues and each pig in a separate bag. Chill fresh tissues before mailing. Do NOT freeze.
  5. Do not send whole, dead pigs (intestines autolyze quickly).

AGENTS DETECTED BY ROUTINE EXAMINATION

Bacteria

Clostridium difficile, Clostridium perfringens, E. coli, Enterococcus duransSalmonella spp.

Parasites

Cryptosporidia, Isospora (coccidia)

Viruses

Rotavirus, PED virus, TGE virus, PRRSV

comments

  • Accurate diagnosis of diarrhea in suckling piglets usually requires submission of tissues.
  • Feces from acutely affected pigs are useful for detection of epidemic agents such as TGEV or PEDV by PCR. Results of tests on feces only (both positive and negative) may not be completely definitive and must be evaluated with consideration of clinical signs.  Samples (10-20 ml) should be taken on the first day of diarrhea.
  • Accurate diagnosis of endemic agents requires both the detection of the offending agent(s) as well as the presence of compatible histologic lesions. 
  • Brachyspira hyodysenteriae can occasionally be isolated from feces (swabs are even less reliable).  
  • Wet mounts of intestinal impression smears or fecal flotation may be of value for quick in-house detection of  Isospora.
  • In cases where mesocolonic edema is prominent, Clostridium difficile is a differential and the entire colon or colon contents should be submitted for a C. difficile toxin ELISA.  
  • In cases of necrotic enteritis, submit both necrotic and adjacent non-necrotic segments, fresh and fixed.

 

Porcine Enteritis - Weaned Pigs

Specimens to submit: The best specimen is an acutely-ill (<24 hours) live untreated pig(s). Alternatively, tissues may be removed from euthanized pigs.

Colon and cecum

Several 10 cm sections, fresh/chilled

Several 1 cm pieces, formalin-fixed

Feces/colon content

2-10 ml fluid contents, fresh/chilled

Ileum

10-15 cm segment, fresh/chilled

Three 1 cm pieces, formalin-fixed

Jejunum

10-15 cm segment, fresh/chilled

Three 1 cm pieces, formalin-fixed

Lesions

10-15 cm segment, fresh/chilled

Several 1 cm pieces, formalin-fixed

Samples removed at necropsy in the field are often better than a whole, dead pig submitted to the lab.

SAMPLING TECHNIQUES

  • Samples must be taken as soon after death as possible (within minutes).
  • Intestines do not need to be tied off at the ends.
  • Flush intestinal segments for histopathologic examination with formalin and drop in fixative. Or, gently open ends of 1/2" segments with a scissors or forceps to expose mucosa as immersed.
  • Pool all formalin-fixed tissues from each pig in one bag; individual pigs can be pooled or kept separate as desired. Package fresh intestines separately from other tissues and each pig in a separate bag. Chill fresh tissues before mailing. Do NOT freeze.
  • Do not send whole, dead pigs (intestines autolyze quickly).

AGENTS DETECTED BY ROUTINE EXAMINATION

Bacteria

E. coli, Salmonella spp., Clostridium perfringens, Enterococcus durans, Brachyspira spp. Lawsonia intracellularis

Parasites

Coccidia, roundworms, whipworms

Viruses

Rotavirus, TGE virus, PED virus, PRRSV, PCV2

COMMENTS

  • Feces can be used to detect TGEV and PEDV by PCR and is diagnostic when expected negative. 
  • Detection of endemic agents from feces does not provide a definitive diagnosis. Detection of Lawsonia or rotaviruses detected by PCR or Salmonella or hemolytic E. coli detected by culture or parasite ova/oocysts detected by fecal flotation should be interpreted in context of clinical signs. Histopathology on tissues for compatible pathologic lesions is required for definitive diagnosis. Fecal samples (10-20 ml) should be taken on the first day of diarrhea. Call the laboratory to discuss the value of feces for diagnosis or monitoring for specific pathogens of interest.   
  • Colitis associated with Brachyspira hyodyseneteriae and Brachyspira pilosicoli should be confirmed by culture and histopathology for a definitive diagnosis. 
  • Porcine Proliferative Enteritis associated with Lawsonia intracellularis can be confirmed by IHC or PCR. 
  • Ill-defined conditions such as dietary hypersensitivity or nonspecific colitis may be implied but cannot be confirmed by routine diagnostic investigations. 
  • In cases of necrotic enteritis submit both necrotic and adjacent non-necrotic segments, fresh and fixed.

 

Porcine Multisystemic Disease Investigations

Specimens to submit: The best specimen is a live untreated pig(s). Alternatively, tissues should include:

Brain

1/2 Fresh and 1/2 formalin-fixed

Turbinate

Turbinate swab (chilled) and turbinate in formalin

Colon and Cecum

Entire organ, fresh chilled

Several 1 cm pieces, formalin fixed

Heart

Fresh/chilled and formalin-fixed/swabs of fibrin if present

Intestine

Two 10-15 cm slices of ileum and two jejunum, fresh/chilled

Several (6-10) 1/2 cm slices ileum and jejunum, formalin fixed

Kidney

Fresh/chilled and formalin-fixed

Liver

Fresh/chilled and formalin-fixed

Lung

Entire lung (one side) or generous portion of lung containing the lesions and adjacent unaffected lung, fresh/chilled

4-6 thin slices (1 cm) through affected and adjacent unaffected lung, formalin-fixed

Joint swabs/synovium

Swabs chilled; synovium fresh/chilled and in formalin

Lymphoid tissues

Spleen, tonsil, and lymph nodes

Fresh/chilled and formalin-fixed

Spinal cord

Entire carcass or vertebral column, fresh/chilled, or

Dissected cord, fresh/chilled

Cross-sections (1/2 cm slices) of cord from 4-5 levels, formalin-fixed

Whole blood

Chilled; useful for clin path, PCR, serology chemistry

sampling techniques

  1. Fresh tissues should be chilled before shipping. Do NOT freeze.
  2. Pool all formalin-fixed tissues from each pig in one bag; individual pigs can be pooled or kept separate as desired. Package fresh intestines separately from other tissues and keep each pig in a separate bag.

agents detected by routine examination

Bacteria

Pasteurella multocida, Streptococcus suis, Actinobacillus pleuropneumoniae, Actinobacillus suis, Arcanobacterium pyogenes, Bordetella bronchiseptica, Haemophilus parasuis, Erysipelothrix, Salmonella spp., E. coli, Clostridium perfingens type A and C, Enterococcus durans, Lawsonia intracellularis, Brachyspira (Serpulina) spp.

Parasites

Coccidia, Cryptosporidia, round worms, whip worms

Viruses

PRRS virus, PCV2, SIV, cytomegalovirus/inclusion body rhinitis (only if turbinates are submitted), PRV, PED virus, rotavirus, TGE virus, Teschovirus, and more.

Mycoplasma

Mycoplasma hyopneumoniae/hyorhinis/hyosynoviae by FA, IHC, PCR.

Non-infectious

Water deprivation, toxicities, deficiencies

comments

PRRS virus is often best isolated from lung lavage fluids. The lung can be lavaged (with cell culture growth media or Lactated Ringers Solution) and the fluid submitted or the lavage can be done at the lab if at least one half of the lung is submitted without holes or slices in it.

 

Porcine Pneumonia / Rhinitis

Specimens to submit: Live acutely affected pig(s). Alternatively, tissues should include:

Brain

1/2 fresh, and 1/2 formalin-fixed

Lung

Entire lung (one side) or generous portion of lesion and adjacent unaffected lung, fresh/chilled

4 to 6 thin slices (1 cm) through affected and adjacent unaffected lung, formalin-fixed. At least 3-4 cross sections through anteroventral lung are recommended

Nasal swab

Swab of deep airway, chilled (Dacron-tipped, slightly moistened, for bacterial and viral cultures)

Snout or turbinate

Turbinate scroll from one side removed at junction with midline

septum, formalin-fixed

Tonsil

1/2 fresh, and 1/2 formalin-fixed

sampling techniques

  1. Fresh tissue should be chilled before shipping. Do NOT freeze.
  2. Do not submit fresh samples in glycerin (glycerin has not proven to be of value and prevents freezing of sections for FA tests).
  3. Samples for virus detection need to be taken at the onset of respiratory signs.
  4. Nasal swab preservation: swabs must be kept moist and cool before and during shipment.
  5. Fixed turbinate must be submitted to confirm the presence of porcine cytomegalovirus (inclusion body rhinitis)

agents detected by routine examination

Bacteria

Pasteurella multocida, Streptococcus suis, Salmonella choleraesuis, Actinobacillus pleuropneumoniae, Actinobacillus suis, Arcanobacterium pyogenes, Bordetella bronchiseptica, Haemophilus parasuis

Viruses

PRRS virus, PCV2, SIV, PRCV, cytomegalovirus/inclusion body rhinitis (if turbinates are submitted for histopath)

Mycoplasma

Mycoplasma hyopneumoniae

agents requiring special tests (by request)

Viruses

Isolation, sequencing

comments

  • Cultures for Mycoplasma hyopneumoniae can be done on fresh/chilled lung, but are not routine because of the difficulty of recovering these fragile organisms in the presence of heavy contamination or concurrent bacterial or other mycoplasmal infection.
  • Porcine respiratory coronavirus is more readily detected from nasal swabs than lung tissues. High serum antibody titers to TGE virus in herds with no evidence of TGE diarrhea also may suggest the presence of PRCV. A differential ELISA serology test is available through the VDL.
  • PCR is used on nasal swabs, oral fluids or lung tissues for detection of SIV with subtyping to determine hemagglutinin (H) and neuraminidase (N) subtypes routine. 
  • PRRSV is often best isolated from lung lavagel samples or serum. The lung can be lavaged (with cell culture growth media or Lactated Ringers Solution) and the fluid submitted. Lung lavages can be done at the lab if at least one half of the lung is submitted without holes of slices.
  • PRRS sequencing has higher success rate from specimens with lower cycle threshold values.