Influenza A virus infection in pigs from Mozambique

Abstract

Swine  influenza  (SI)  is  an  acute  and  highly  contagious  disease  of  the  respiratory tract of pigs caused by swine influenza A virus (SIA). The disease causes economic losses in swine production and is of great public importance for its zoonotic potential. The aims of the present  study  were  to  report SIA infection  in  pigs  from  Mozambique  and  characterize  the anatomopathological  and  immunohistochemical  features  of  associated  lung  lesions.  Lungs from  457  slaughtered  pigs  were  subjected  to  gross  evaluation  and 38  (8.3%)  lungs  with cranioventral  consolidation  were  collected  from  a slaughterhouse  in  Matola  City,  Southern Mozambique. Consolidation areas in each lung lobe  were classified in 4 grades according to the lesion extension. Samples with consolidated lung tissue were examined for histopathology and  immunohistochemistry  for  the  presence  of  SIA,  Porcine  circovirus  type  2  (PCV2)  and Mycoplasma  hyopneumoniae  antigens.  The  lungs  had  multifocal  to  coalescing  areas  of consolidation observed most frequently in the craniallobes. The lesions involved mainly one or three  pulmonary  lobes  and  grade  1  and  2  lesions  were  the  most  frequent.  The  main histopathological  findings  were  necrotizing  bronchiolitis  (23/38),  alveolar  neutrophil infiltration (24/38), type II pneumocytes hyperplasia (26/38), peribronchiolar lymphoid tissue hyperplasia  (28/38)  and  interstitial  mononuclear  cells  infiltrate  (29/38). SIA  antigen  was detected by immunohistochemistryin 84.3% (32/38) of lung samples and all lung samples were negative  for  PCV2  and Mycoplasma  hyopneumoniaantigense. Pigs  that  presented  a  positive result on IHQ were from Matutuine district (5/32), Moamba district (2/32), Namaacha district (21/32), Boane district (3/32) and Matola city (1/32). These results demonstrate that SIA is a cause of pneumonia in pigs in Mozambique