Assessment of knowledge and detection of post weaning multisystemic wasting syndrome in pigs in selected Districts of Uganda

Abstract

Postweaning multisystemic wasting syndrome (PMWS) is a globally emergent epizootic disease of swine. The disease caused by Porcine Circovirus type 2 (PCV2) was first detected and described in Western Canada and has since spread to all the major pig producing countries of the world including Europe, the Americas and Asia. The occurrence of the disease in Uganda has been reported but the exact magnitude (distribution and severity) is not known. The disease has had significant economic, public health, and animal health effects on the pork industry in terms of reducing the number of pigs at slaughter, reduced feed conversion rate, increased costs for management and medication of sick pigs, and costs of treating secondary diseases following PMWS-associated immunosuppression. The immunosuppresseion may also cause increased carcass contamination by food-borne pathogens arising from potentially increased prevalence of infection on-farm and increased shedding at slaughter. This study was therefore carried to assess the knowledge of farmers on PMWS and detect the presence of PCV2 in pigs in districts around Kampala which form the largest number of pigs in the country and also serve as breeding stock for other regions. A total of 131 farmers and 12 key informants were interviewed with 3 focus group discussions conducted. Four hundred inguinal lymph node samples were collected in addition to lymph node and other visceral organs from 20 emaciated pigs with typical clinical signs reported or observed. The samples were examined with standard Hematoxylin and Eosin, Immunohistochemistry and Polymerase Chain Reaction techniques to detect lesions, antigens and genetic materials specific to PCV2. The results obtained were analyzed and descriptive statistics generated. Out of the 131 respondents, none of them ever knew about PMWS as well as field veterinarians. Eighty one percent of the farmers kept pigs under intensive system of management with the majority (77.1%) raising their own replacement stock while 99.2% of the farmers mixed piglets weaned from different sows with most farmers (63.4%) reporting that more than 70% of piglets survive up to breeding or market age. Fifty seven percent of the farmers reported that their piglets died when emaciated and that the disease could persist for more than 4 months with signs of PMWS. Most observed lesions on lymph node from abattoir were hemorrhage (11.8%) and necrosis (2.8%). From field cases, all the animals were emaciated with some form of diarrhea. The main lesion was severe lymphoid depletion with histiocytic and macrophage infiltration, shortening of intestinal villi, pneumonia and nephritis. Twenty five percent of the field cases tested positive on PCR and IHC. The PCR amplicon band was approximately 480bp and the sequences generated from the PCR products were at least 98% homologous to 100 sequences submitted on the gene bank though with slight variability among them in nucleotide alignment. From this study, it’s clear that there is knowledge gap on PMWS among farmers and veterinary practitioners in Uganda at present though the virus exists with similar genetic identity as of elsewhere. Further studies like seroprevalence and case-control studies on field cases should be carried out to understand the disease severity on a wider scale so as to institute appropriate control measures.