Index case of porcine epidemic diarrhea in Canada

Murray Hazlett, Davor Ojkic, Jim Fairles

On January 22, 2014, 4 2-5-day-old pigs were submitted from a 500-sow farrow-to-finish herd in southwestern Ontario, with a presenting complaint of acute scours.

The pigs were stained with watery yellow feces.  Postmortem findings revealed milk in stomachs, and large amounts of watery yellow fluid in small intestine and colon (Figure 1).  Histology, bacteriology and virology were performed, the virology including a multiplex PCR test for porcine coronaviruses (porcine respiratory coronavirus (PRCV), TGEV and PEDV), as well as PCR testing for porcine rotaviruses A, B, and C.

All submitted colon samples were strongly positive on PCR testing for PEDV genome products.  Bacteriology and other virology PCR tests did not reveal any other pathogens.

Histology was done on the gastrointestinal tract, and significant lesions were confined to the small intestines, where all 4 pigs had moderate to marked atrophy and fusion of intestinal villi (Figure 2).  Immunohistochemistry for TGEV was negative.  Atrophic enteritis is a non-specific lesion that is commonly associated with enteritis due to TGEV and rotaviruses (and now PEDV).

Surveillance work and the development of the porcine coronavirus multiplex real-time PCR test has been funded by the Ontario Ministry of Agriculture and Food because of concerns of the virus crossing from the USA into Canada and the need to detect its presence rapidly for control purposes.  The test checks for (1) porcine coronaviruses (this primer will find TGEV and PRCV), (2) TGEV specifically, and (3) PEDV specifically.  We have been performing this test since August 2013, and as of the end of February 2014 had tested about 2,000 specimens. We had, as of February 14, identified 14 other premises that are infected with PEDV.

Biosecurity is paramount in controlling the of spread of this organism.  Please do not send neonatal pigs in for workups, we are very concerned about spread of the organism from the laboratory.  Instead, please send only swabs – swabs with virus transport medium can be obtained from the lab.  Please see our lab update note on our website for additional instructions – ahl.uoguelph.ca.   

Watery yellow intestinal content in piglet with PED.

Marked atrophy and fusion of intestinal villi in piglet with PED.

Figure 1.  Watery yellow intestinal content in piglet with PED.

Figure 2.  Marked atrophy and fusion of intestinal villi in piglet with PED.

Tracheitis in pigs  

Murray Hazlett, Durda Slavic

We receive occasional mail-in submissions of tracheitis in pigs (Figures 1, 2), or it is found at autopsy, often in association with other lesions.  Traditionally, it has been suggested that influenza A virus (“swine influenza virus”, SIV) may be associated with this lesion, and SIV has been demonstrated in some reports.  In 7 recent submissions, 4 were tested for SIV via immunohistochemistry or PCR, with no positive SIV results.  Bacteriology revealed Streptococcus suis and Pasteurella multocida in 2 each of 4 cases, with Streptococcus porcinus, Trueperella pyogenes, Bordetella bronchiseptica and Streptococcus equisimilis also isolated.  Silver stains for CAR bacilli (cilia-associated respiratory bacillus) were negative in the 1 submission tested.  Tracheitis was always associated with some degree 

Ulceration and formation of a fibrin plug in the trachea of a pig.

Histology of Fig 1.

Figure 1. Ulceration and formation of a fibrin plug in the trachea of a pig.

Figure 2. Histology of Fig 1.

Bacterial abortions associated with Actinomyces hyovaginalis and Staphylococcus chromogenes

Murray Hazlett, Durda Slavic, Mike DeGroot, Beverly McEwen

A 75-sow herd had an increase in the number of sows not in pig over the previous 2 months.  Two sows aborted, and no sows were off feed.  The sows were group housed with a clean-up boar.  Aborted fetuses were submitted on 2 occasions for a diagnostic workup.

The fetuses were moderately to markedly autolyzed, and accompanied by placenta.  Crown-rump lengths ranged from 11 to 24 cm.  Microscopically in both, there was moderate to severe placentitis and variable pneumonia.  Bacteria were commonly seen in both tissues.  Large numbers of Actinomyces hyovaginalis were isolated from the 2 samples cultured from the first submission (stomach content), and moderate to large numbers of Staphylococcus chromogenes was isolated from lung, stomach and placenta of the second submission.  Testing for PRRSV, PCV-2, porcine parvovirus and mycotoxins was negative.  Low titers to several Leptospira spp. serovars were present in the abdominal fluid of one of the abortion samples.

It is uncommon to see placentitis in swine cases submitted for autopsy (Figures 1 & 2).  This, as well as the negative results for other tests, makes bacterial abortion the most likely diagnosis here.  These bacterial pathogens may have been spread by the boar, or it may be that the free-housing resulted in more fighting, and allowed for nose to vaginal transmission between pigs.

We have recovered A. hyovaginalis from other submissions from sows with vaginal discharges, along with other organisms.  The organism is relatively slow growing and may be easily overgrown by other vaginal flora on culture plates, so unless present in relatively pure culture, it may be missed.  S. chromogenes is similar to Staphylococcus hyicus, and is also capable of producing exfoliative toxin.

Subsequent swabbing of 14 sows did not result in isolation of any additional A. hyovaginalis, however S. chromogenes was recovered from 1 sow.  Other pathogens isolated included Streptococcus suis and Staphylococcus hyicus.  When samples were collected, bite marks were noted on vulvas of several dry sows.   

Neutrophils and fibrin over the maternal surface of the placenta (Actinomyces hyovaginalis).

Figure 1.  Neutrophils and fibrin over the maternal surface of the placenta (Actinomyces hyovaginalis).