Preweaning mortality in pigs. 7. Polyarthritis

The incidence and causes of polyarthritis in sucking pigs were studied in herds with 2,936 litters during a 2-year period. Among pigs more than 3 days old, the average morbidity rate was 3.3 per cent and the mortality rate amounted to 1.5 per cent (Table I). Among herds the morbidity ranged from 0.9 to 7.0 per cent and the mortality due to polyarthritis from 0.5 to 2.8 per cent. The incidences of polyarthritis were higher in the progeny of gilts than in the progeny of sows of other age groups (Table II). No consistens correlation between litter size at birth and the mortality rate due to polyarthritis was found (Table III). Cases of polyarthritis were observed in 17.8 per cent of the examined litters. Death due to polyarthritis occurred in 10.8 per cent of the litters (Table I); 67.3 per cent of the fatal cases occurred sporadically with only one pig lost per litter (Table IV). The mortality due to polyarthritis appeared to be higher in male pigs (Table V). An analysis of some possible contributory factors showed that the frequency of polyarthritis was adversely affected by new introduction of female breeding stock, clipping of the canine teeth and tail docking in the new-born, and by occurrence of skin diseases in individual piglets (Table VI, IX & XII). No obvious relation was found with such factors as: season of the year, sow's health condition, herd size (Table I), or hygiene level in the individual herds (Table VIII). Death due to polyarthritis occurred most frequently in pigs 2--4 weeks of age (Table X). The pathological lesions, which varied according to the duration of the inflammation and to the aetiology, are described. Arthritis was most frequently observed in the larger limb joints, although every joint may be affected (Table XI). In the majority of the cases a meningoencephalitis was present. A survey of other concomitant, complicating or possible predisposing lesions are presented (Table XII). The bacteriological examination of joints and other organs Table XIII) showed that haemolytic streptococci by far dominated as causative organism. Staphylococci species and E. coli were isolated from affected joints in 6.4 per cent and 4.3 per cent of the pigs, respectively. C. pyogenes and E. rhusiopathiae were rarely encountered in these sucking pigs with polyarthritis. Aspects of the epidemiology and pathogenesis are discussed in regard of minimizing the losses due to polyarthritis/meningitis in sucking pigs.