Production diseases in smallholder pig systems in rural Lao PDR.

Pigs in Lao People's Democratic Republic are important for income and food security, particularly in rural households. The majority of pigs are reared in smallholder systems, which may challenge the implementation of any disease control strategies. To investigate risk factors for pig production diseases in such farming systems in the country a serological survey was conducted during 2011. A total of 647 pigs were sampled, accounting for 294 households in Luang Prabang and 353 in Savannakhet province representing upland and lowland, respectively. The results demonstrated that pigs in Lao PDR had antibodies against erysipelas (45.2%), CSF (11.2%), PRRS (8.6%), FMD O (17.2%) and FMD Asia 1, (3.5%). Differences in the housing systems influenced disease risk, for example, penned pigs had reduced odds of FMD and CSF, compared to those in scavenger systems. Pigs owned by farms using a sanaam (a communal area where pigs are kept for some time of the year) had 3.93 (95% confidence interval (CI): 1.09-14.7) times the odds of having pigs seropositive for FMD. Farms on which sudden piglet deaths had been experienced were more likely to have pigs seropositive for FMD O and erysipelas. These diseases constrain the development of village farming and the wider livestock industry due to their impact on productivity and trade. Vaccination coverage for FMD and CSF was low and there was a lack of national funding for livestock disease control at the time of the study. Further investigation into sustainable low-cost control strategies for these pathogens is warranted.

Comparison of inoculation regimes for the experimental production of swine erysipelas arthritis. I. Clinical, pathological and bacteriological findings.

The arthritic form of swine erysipelas was induced in pigs by multiple intravenous inoculation of 2 strains of Erysipelothrix rhusiopathiae. The strains differed significantly in their arthritogenicity but not in the number of cases of lameness induced. The use of 3 intravenous inoculations instead of 5 did not significantly affect the outcome. In a second trial, the more arthritogenic strain was injected in ten-fold dilutions from 5 x 10(9) to 5 x 10(4) organisms. Pigs receiving the lower doses showed high variability in their arthritic responses that precluded sensitive analysis of the dose effects on the number of arthritic and infected joints. However, slaughter weights showed a significant negative correlation with dose. Mean slaughter weights in treatment groups varied by 14.6 kg per pig, an average weight loss of 3 kg per pig for each ten-fold rise in dose of the highly virulent strain, and significantly correlated with the number of arthritic and infected joints. Culture of homogenised synovial membrane through selective horse meat-serum broth containing kanamycin, neomycin and vancomycin identified 66% and 59% more infected joints than primary blood agar culture of synovial fluid or synovial membrane homogenate, respectively.

[The pathogenesis of erysipelas arthritis]. / Die Pathogenese der Rotlaufarthritis.

Experimental chronic erysipelas polyarthritis in rat, induced by living erysipelas bacteria, histologically can be divided into four different phases. In the phase of population bacteria are distributed diffusely within the whole joint but accumulate in the transitional zones and entheses by multiplication within the ground substance of cartilage. In the phase of acute destruction a severe inflammation of all joint tissues predominates. Bacterial antigen is eliminated by a pannus tissue destroying the cartilaginous structures. In the following phase a diffuse dystrophy of articular cartilage dominates. The reason for this process is not clear; within the cartilage bacterial antigen can seldom be demonstrated, but it accumulates intracellularly in the periphery of the joints (e.g. dense connective tissue, muscles). In the chronic phase we find a lymphoplasmacytic infiltration of the subsynovium, a lining cell hyperplasia, and pannus formation arising from the epiphyseal bone marrow cavity. The relation between chronic inflammation and destruction in the central and antigen persistence in the outer parts of the joints is a matter of current investigation.