Diarrhea in Late Finishers Caused by PCV2 Infection - A Case Report

This report describes the differential diagnose of acute diarrhoea with increased mortality in a case of late finishing pigs. In the last 3-4 batches pigs showed bloody mucoid diarrhea late in finishing after the first pigs had been marked for slaughter, resulting in a preliminary diagnosis of porcine haemorrhagic enteropathy (PHE). After acute onset of clinical signs, affected pigs usually died within 24 hours, despite systemic treatment with Tylosin or Tiamulin.

The study farm is a finishing farm with a total of 4.500 places distributed over 3 sites. Piglets were vaccinated against Mycoplasma hyopneumoniae and porcine intestinal adenomatosis on the farm of origin. The live Ileitis vaccine was administered one to three weeks after placement into the nursery, applied orally via drinking bowls. Six fecal samples were taken and investigated by PCR for Lawsonia (L.) intracellularis and Brachyspira hyodysenteriae. Post-mortem examination (PME) was performed on two affected pigs and formalin-fixed samples of the small intestines were investigated histopathologically, immunhistologically (L. intracellularis) and by in situ hybridization (PCV2).

Bloody content was present in small and large intestine. Macroscopically gastric ulcers were not found. PCR for Brachyspira spp. was negative, PCR for L. intracellularis was positive on 3/6 fecal samples. Histopathology revealed a moderate, diffuse, lympho-histiocytic and plasmacytic enteritis with eosinophilic granulocytes. Immunohistochemistry failed to detect L. intracellularis. In contrast, PCV2 was found either in cells of mucosa-associated immune follicles or in infiltrating histiocytic cells of the lamina propria. Therefore, PCV2 was suspected to be the cause of the enteric disorder. PCV2 vaccination at weaning was implemented as routine measure, mixed with a single dose of Mycoplasma vaccine using the same adjuvant. The previous clinical signs disappeared immediately once the first vaccinated pigs reached late finishing. The performance results of four non-vaccinated batches during the clinical outbreak compared to four vaccinated batches are summarized in Table 1.

Clinical signs and detection of L. intracellularis antigen in feces are not sufficient to confirm PHE in late finishing. Histopathological investigation is an essential step towards a reliable diagnosis. Even in the absence of typical clinical signs suggestive of PCVD (wasting, respiratory symptoms, PDNS) PCV2 infection has to be considered as differential diagnosis. This case report demonstrates that PCV2 infection can cause severe haemorrhagic enteritis in late finishing associated with increased mortality.

Disclosure of Interest: None Declared.