Postweaning multisystemic wasting syndrome

Postweaning multisystemic wasting syndrome ("PMWS") is a porcine disease. This disease causes illness in piglets, with clinical signs including progressive loss of body condition, visibly enlarged lymph nodes, difficulty in breathing, and sometimes diarrhea, pale skin, and jaundice. PMWS has been reported from most pig-producing countries of the world at huge cost to agriculture. PMWS is caused by porcine circovirus type 2 (PCV2)^[1]

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PMWS & PCV2

PMWS is associated with infection of pigs by porcine circovirus type 2 (PCV2).^[1] However, the exact relationship between PCV2 infection and PMWS remains unclear. There is not a straightforward relationship between infection and disease. PCV2 has a near universal distribution – present in most pig herds. In contrast, PMWS is more sporadic in its distribution. Experimental induction of PMWS has not been achieved by PCV2 infection alone, using infectious DNA clones of the virus or a pure form of PCV2 derived from infectious DNA clones. Therefore it is assumed that PMWS is a multifactorial disease. PCV-2 is necessary but not sufficient for the development of PMWS. There is no significant correlation of the disease with virus sequence variation with affected and control pigs.

Symptoms

Both PMWS and PDNS (Porcine Dermatitis and Nephropathy Syndrome) are associated to PCV2.^[2] It seems that many pigs affected by the circovirus also tend to develop secondary bacterial infections, like Glässer disease (Haemophilus parasuis), Pulmonary Pasteurellosis, Colibacilosis and Salmonellosis and others.^[3] Dissected morbid pigs showed lesions in multiple organs, especially in lymphoid tissues, giving birth to the term "multisystemic".^[4]

"The distinguishing lesion caused by PCV2 is an inflammatory infiltration by histocite cells with variable intensity, located in the lymphoid organs, liver, kidney, and lung"^[5]

Wasting pigs is the most common sign of PMWS infection, increasing the mortality rate significantly.

Management practices to decrease severity of PMWS

François Madec, a French author, has written many recommendations on how reduce PMWS symptoms. They are mostly measures for disinfection, management, and hygiene, referred to as the "20 Madec Points" [Madec & Waddilove, 2002].

These measures have recently been expanded upon by Dr. David Barcellos, a professor at the Veterinary College in the Universidade Federal do Rio Grande do Sul, Rio Grande do Sul, Brazil. He presented these points at "1st Universidade Federal do Rio Grande do Sul Symposium about swine management, reproduction, and hygiene".

He divided his points by pig growth stage, and they can be loosely summarized as:

• keep the gutters clean
• increase feeder space
• use pens or small cages with solid dividers
• avoid mixing pigs from different origins
• improve the quality of air
• decrease maximum capacity, giving each pig more room
• separate sick animals as soon as possible, and treat them in a hospital pen. If they do not respond to antibiotics in three days, they should be culled
• control access of people and other animals
• reduce invironmental stress factors such as gases and air currents
• use immunizations and preventive medications for secondary agents commonly associated with PMWS

See also

• Animal viruses
• Porcine circovirus

References

• Grierson S.S., King D.P., Wellenberg G.J. & Banks M.; "Genome sequence analysis of 10 Dutch porcine circovirus type 2 (PCV-2) isolates from a PMWS case-control study." Res Vet Sci. 2004 Dec; 77(3):265-8).

Notes

1. ^ ^{a b} Mankertz P (2008). "Molecular Biology of Porcine Circoviruses", Animal Viruses: Molecular Biology. Caister Academic Press. ISBN 978-1-904455-22-6. 
2. ^ Barcellos & Pescador, 2003 and Segalés & Domingo, 2000
3. ^ David Barcellos, 2006
4. ^ Harding & Clark, 1997
5. ^ Sobestiansky et al., 2002