Postweaning syndrome in pigs

SIR, - Porcine multisystemic wasting syndrome (PMWS) was initially identified and reported in pig herds in Canada a decade ago (Harding 1996); since then, it has been described worldwide, including Argentina, Brazil and Mexico in Latin America (Trujano and others 2001, Zanella and others 2002, Sarradell and others 2002). Porcine circovirus type 2 (PCV-2) is considered the infectious cause of this disease (Ellis and others 1998, Allan and Ellis 2000, Segalés and others 2004), and its detection within the characteristic lymphoid lesions of PMWS constitutes the basis for the diagnosis of the disease (Segalés and others 2004). This letter reports the existence of PMWS in pigs in Venezuela.

A clinical condition, characterised by pigs with growth retardation, enlargement of superficial inguinal lymph nodes, dyspnoea, skin pallor and diarrhoea, was detected in three 500- to 800-sow, farrowto- finish farms, located in Aragua and Carabobo states in northern Venezuela. Twelve eight- to 12-week-old pigs were selected (three to five pigs from each farm) and examined postmortem. Postmortem examination revealed enlargement of the inguinal, mesenteric and mediastinal lymph nodes, and non-collapsible lungs. Lung, lymph node, intestine, spleen, liver and kidney samples were fixed in 10 per cent buffered formalin, and processed by conventional histological methods. The same samples were used in an in situ hybridisation (ISH) technique to detect PCV-2 (Rosell and others 1999). A PCR method to detect PCV-  was applied in one of the animals and further sequencing of the PCR product was performed.

Lymphoid organs such as lymph nodes, spleen and Peyer´s patches showed loss of follicle architecture, intense lymphoid cell depletion (91 per cent), severe histiocytic infiltration (83 per cent), presence of  multinucleate giant cells (75 per cent) andbasophilic cytoplasmic inclusions in histiocytic cells (41 per cent), as described in PMWS. Eleven of 12 (91 per cent) of the animals had interstitial pneumonia.Moderate to high amounts of PCV-2 were found in the lymphoid tissues. The case tested by PCR also yielded a positive result, and the sequence of the PCR product revealed over 98 per cent nucleotide homology with France and China PCV-2 strains.

The diagnosis of PMWS in these pigs was based on clinical signs, microscopic lesions and the results of ISH detection, thus fulfilling the case definition accepted for the disease (Segalés and others 2004). Therefore, this is the first description of PMWS in Venezuela and, because the prevalence is not known, further studies are needed to characterise the extent and importance of PMWS in the country. 

ALLAN, G. & ELLIS, J. (2000) Porcine circovirus: a review. Journal of Veterinary Diagnostic Investigation 12, 3-14

ELLIS, J.,HASSARD, L., CLARK, E., HARDING, J., ALLAN, G.,WILLSON, P.,STUKALLE, J.,MARTIN, K.,MCNEILLY, F.,MEEHAN,B.,TODD,D. & HAINES, D. (1998) Isolation of circovirus from lesions of pigs with postweaning multisystemic wasting syndrome. Canadian Veterinary Journal 39, 44-51 

HARDING, J. C. (1996) Postweaning multisystemic wasting syndrome (PMWS): preliminary epidemiology and clinical presentation. First Proceedings of the Western Canadian Association of Swine Practitioners. Saskatoon, Canada, October 18 to 19, 1996. p 21 

ROSELL, C., SEGALÉS, J., PLANA-DURAN, J., BALASCH, M., RODRIGUEZ-ARRIOJA, G. M., KENNEDY, S., ALLAN, G. M., MCNEILLY, F., LATIMER, K. S. & DOMINGO, M. (1999) Pathological, inmunohistochemical and in situ hybridization studies of natural cases of PMWS in pigs. Journal of Comparative Pathology 120, 59- 8

SARRADELL, J., PÉREZ, A., ANDRADA, M., RODRÍGUEZ, F., FERNÁNDEZ,A. & SEGALÉS, J. (2002) PMWS in Argentina. Veterinary Record 150, 323 

SEGALÉS, J., ROSELL, C. & DOMINGO, M. (2004) Pathological findings associated with naturally acquired porcine circovirus type 2 associated disease.Veterinary Microbiology 98, 137-149 

TRUJANO, M., IGLESIAS, G., SEGALÉS, J. & PALACIOS, J. (2001) PCV-2 from emaciated pigs in Mexico. Veterinary Record 148, 792 

ZANELLA, J. R. C., ZANELLA, E. L. & MORÉS, N. (2002) Postweaning multisystemic wasting syndrome in Brazil caused by porcine circovirus type 2. Proceedings of the 17th IPVS Congress. Vol 2. Hamburg, Germany, June 27 to July 1, 2004. p 422