Sneezing in weaned pigs due to non-infectious causesa case report

Background
Sneezing is induced by chemical, mechanical or allergen factors, either of infectious or non-infectious origin. We present a diagnostic protocol and the findings in a field case of recurrent extensive sneezing in weaned pigs on a 400 sow head farrow-to-finish farm.Material and MethodsA cohort study was conducted to determine the incidence of disease and the course of clinical signs. Every week sneezing and other signs in each room were assessed. In addition, 4 representative pigs were submitted for post mortem investigations and PCR testing. Furthermore, nasal swabs of 60 pigs were submitted for PCR on SIV. Finally, environmental and biosecurity risk factors were assessed.
Results
Prevalence of sneezing increased from 2% in 3wk old piglets to 80% in 6 wk old pigs. Epiphora was observed in sneezing pigs, but already present in 80% of pigs at 4wks. Nasal discharge was of serous nature at 4wk and purulent in pigs from 5 wk onwards.Post mortem investigations returned no gross abnormalities, but a multifocal mild subacute histiocytic interstitial pneumonia and a multifocal acute mild purulent and eosinophilic rhinitis was found on histology. PCR tests for PCV2, PRRSv and SIV on lung tissue were negative. ISH for Pneumocystis spp was negative as well. 1/60 nasal swabs for SIV tested positive. Assessment of environmental risk factors returned a low biosecurity score, aerial NH3 of 30 ppm at 4 weeks of age and high dust levels.Discussion & conclusionBased on the absence of infectious agents tested for and the presence of an eosinophilic inflammation, it was concluded that an allergic reaction was the primary cause of sneezing and purulent rhinitis was considered as a secondary bacterial infection. High dust levels, climatic errors and poor biosecurity were the likely cause of the allergic reaction. Dust levels nor exact dust composition were measured, but are recommended in future cases.