Inoculation of Porcine Foetuses with Different PCV2 Genotypes http://www.pcvd.org/documents/PCVD_newsletter_June_2008.pdf This report in the June 2008 issue of the newsletter from the EU PCVD Consortium describes the clinical outcome of PCV2 infections in foetuses.

PCV2 may cause mummification and abortion in PCV2-negative swine herds recently primary infected with PCV2. Prompted by recent field observations of PMWS that PCV2 genotype 1 might be more pathogenic than genotype 2, this study looked at the clinical outcome of PCV2 infections in foetuses.

The foetuses of two conventional sows were inoculated by laparatomy at 55 days of gestation with 104.3 TCID50 of PCV2 in the peritoneal and amniotic cavities. In the first sow 2 foetuses were injected with genotype 2 strain Stoon-1010 (isolated from a case of PMWS) and one with genotype 2 strain 1121 (isolated from a case of reproductive failure). In the second sow, 2 foetuses were injected with genotype 1 strain 48285 (isolated from a case of PMWS), one with genotype 1 strain 1147 (isolated from a case of PDNS) and one with genotype 2 strain 1121 (isolated from a case of reproductive failure).

The sows were euthanized 21 days post inoculation. PCV2-inoculated and noninoculated foetuses were examined for gross lesions and for the presence of PCV2 and of PCV2-specific antibodies. Six out of 7 PCV2-inoculated foetuses were oedematous and had distended abdomens.

Haemorrhages and congestion in internal organs and liver enlargement were also observed.

The 1147-inoculated foetus had a normal appearance but liver enlargement, lung oedema and generalised lymph node enlargement were observed. High PCV2 titres (> 10^4.5 TCID₅₀ / g tissue) were found in all 7 inoculated foetuses, especially in the heart, liver and spleen and high numbers of PCV2-infected cells (>1,000 infected cells per 10mm² tissue) were observed in the heart.

A low anti-PCV2 antibody titre was found in the 1121-inoculated foetus from the second sow. In the 6 other foetuses, no antibody response was observed. Indications that PCV2 may spread to non-inoculated foetuses were not found.

It was concluded that different PCV2 strains replicate to similar high titres in different foetal organs and induce comparable gross pathological lesions. In this way, it was demonstrated that the clinical outcome of a PCV2 infection at 55 days of gestation is independent of the genotype and the clinical origin of the PCV2 strain.

October 2008

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