Comparison of Pneumocystis nucleic acid and antibody profiles in two Austrian pig herds

Pneumocystis belongs to the opportunistic fungi and is of high clinical relevance in immunocompromised patients who may develop severe interstitial pneumonia. Pneumocystis carinii f. sp. suis can frequently be detected in pigs co-infected with other respiratory pathogens. The occurrence of Pneumocystis on farm level has not yet been investigated. For this reason, the aim of the present study was the evaluation of Pneumocystis nucleic acid and antibody profiles in two Austrian pig farms.

Bronchoalveolar lavage fluid (BALF) and serum samples of pigs from different age classes (suckling piglets 1st week of life (S1), suckling piglets 3rd week (S2), weaning piglets 2nd month (W1), weaning piglets 3rd month (W2), fattening pigs 4th month (F), and sows (SOW)) of two Austrian farrow-to-finish farms with respiratory disorders were collected. On farm A, 45 BALF samples (S1: 8, S2: 7, W1: 8, W2: 8, F: 14), and on farm B, 47 BALF samples (S1: 8, S2: 8, W1: 8, W2: 8, F: 15) were taken. On each farm, 63 serum samples were collected (S1: 8, S2: 8, W1: 8, W2: 8, F: 15, SOW: 16). BALF samples were analyzed by qPCR, antibody titres against Pneumocystis were determined by XpressBio Pneumocystis carinii swine ELISA (Express Biotech International, Frederick, MD, USA).

On farm A, 5 of 8 suckling piglets in the 1st week of life were positive and had a mean Pneumocystis burden of 10⁷ copies/ml BALF. In the groups S2 and W1, all pigs were positive and the concentration increased to 10⁹ copies/ml BALF on average. In group W2, only one pig was positive and the Pneumocystis concentration decreased to 10⁶ copies/ml BALF. In group F, the fungus could not be detected anymore. Farm B showed a different profile. The pigs were negative until the 3rd month of life. In group W2, 4 of 8 pigs and in group F, 8 of 15 pigs were positive, both groups with a mean burden of 107 copies/ml BALF. Antibodies against Pneumocystis were present in sows, as maternal antibodies in suckling piglets and as immunological reaction after infection.

The results clearly show that the Pneumocystis profiles can vary between farms. Pneumocystis is an opportunistic fungus and its proliferation is obligatory related to immunosuppression. In the present study, other respiratory pathogens were not analyzed, but we assume that proliferation is triggered by co-infections. Suckling piglets are probably more susceptible to an infection, can be infected very early in life and show higher burdens but, nevertheless, Pneumocystis can also contribute to respiratory disorders in older pigs.

Disclosure of Interest: None Declared.