Effect of maternal vaccination on the susceptibility of growing pigs to leptospiral infection.

Serum samples were collected from 30 piglets, derived from 17 litters, whose dams had been vaccinated against leptospirosis. Microscopic agglutination test (MAT) titres against Leptospira interrogans serovar pomona varied greatly from pig to pig; there was less variation among littermates. Titres declined between 4 and 10 weeks of age, with an uncorrected half-life of 15.5 days, consistent with IgG being the main antibody class involved. Twelve pigs, 4 derived from unvaccinated sows and 8 from sows vaccinated against leptospirosis, were challenged intravenously at 8 weeks of age with leptospires of serovar pomona. Colostrum-derived antibody protected 4 out of 8 pigs, and in 1 of the remaining 4 the serological response was reduced. Three of the protected pigs showed reduced serological responses and in the fourth the response was strong, but delayed. All of the pigs derived from unvaccinated sows developed leptospiraemia and leptospiruria and showed strong serological responses. Protection by colostrum-derived antibody bore an inexact relationship to MAT titre, but a titre of 16 appeared to be sufficient for protection.

The prevalence of F107 fimbriae and their association with Shiga-like toxin II in Escherichia coli strains from weaned Australian pigs.

A total of 480 haemolytic Escherichia coli (HEC) strains from weaned pigs were tested using an oligonucleotide probe to determine the prevalence of F107 fimbriae in Australia. Of these, 62% were positive. F107 was detected in serogroups O141, O138, O8, O45, O139, O157 and O98 but not in O149 nor O147. 81% of E. coli strains not producing other fimbriae (K88, 987P, K99 or F41) were positive for F107; 5% of strains with K88 fimbriae also had F107. Serological investigation of the expression of F107 fimbriae indicated that serogroups O141, O138, O8, O45 and O157 produced variant F107ac. Variant F107ab was found on O139 strains only. The F107 fimbrial subunits of both variants had a molecular weight of approximately 16 kDa. A total of 350 of the HEC strains were tested to determine the prevalence of the Shiga-like toxin II (SLT II) gene. 29.0% of these strains were positive. SLT II was detected in serogroups O141, O138, O149, O98, O45, O8 and O157 but not in O139. 25% of these strains were positive for both F107 and SLT II.

Risk factors for gastric ulcers in Australian pigs at slaughter.

The stomachs of pigs (n=15,741) originating from 136 herds from the Australian states of Queensland, Western Australia, Victoria and New South Wales were examined at slaughter for the presence of oesophago-gastric ulcers (OGUs). Stomachs were categorised as being normal, hyperkeratotic, eroded, ulcerated, or having strictures. A questionnaire was distributed to piggery owners to identify factors associated with an above-average herd prevalence of OGU. Thirty percent of all pigs examined had OGU (median within-herd prevalence of 17%). The median within-herd prevalence in Victoria (53%) was significantly higher than in Western Australia (30%) or Queensland (7%). The prevalence of OGU in culled breeding animals was significantly higher than in porkers or baconers from the same herds. There was no difference between the prevalence of OGU in male and female pigs sampled from the same Western Australian herds. The relationship between OGU and herd and pig risk factors was assessed by random effects logistic-regression analysis. Herds with a high prevalence of OGU were more likely to feed ad libitum (OR=13.7), use automated feeding systems (OR=7.8), feed a pelleted ration (OR=384) and get water from a dam rather than from a bore or river (OR=3.8). Furthermore, for every change in the ration formulation for finisher pigs, the risk of OGU increased 1.5 times.

Prevalence of enteroviral and parvoviral antibodies in pig sera.

Surveys of serum antibodies to enterovirus serotype 8 and parvovirus were conducted in pigs three to 21 weeks old using the virus neutralisation (VN), enzyme-linked immunosorbent assay (ELISA) and haemagglutination inhibition tests. Antibody levels to enterovirus were at their lowest at four to eight weeks old, increased at 14 to 16 weeks to high levels which were maintained until 21 weeks. Specific immunoglobulin G (IgG) values measured by ELISA paralleled VN values and were similar in two separate farm surveys. Measurement of immunoglobulin M (IgM) levels indicated that enterovirus infection occurred about four weeks old. Sera obtained from a large number of geographically separated farms, from abattoir-bled animals and from colostrum-deprived piglets raised for 33 weeks from birth in an isolated environment were tested by VN. Results revealed that porcine enterovirus serotype 8 is spread widely throughout northern Victorian piggeries and high antibody levels prevail. In contrast to the enterovirus antibody results, parvovirus antibody levels measured in piglets declined from high levels at three to four weeks to undetectable levels from 13 weeks old.

Studies on preweaning piglet diarrhoea.

The aim of this study was to determine the cause and risk factors involved in preweaning piglet diarrhoea. Faecal samples from 2380 diarrhoeic piglets, 5 to 30 days of age, were examined for enteropathogens. Isospora suis oocysts were detected in 53.8% of samples, Escherichia coli in 18.2% and rotavirus in 16.9%. I suis had the widest distribution, being present on 70.9% of 151 piggeries. The onset of diarrhoea occurred mainly between 7 and 14 days (77.5%), peaking at 10 days. Records of 4086 litters from two intensive piggeries were analysed and showed no seasonal variation or effect of sow parity on the incidence of piglet diarrhoea. I suis was the most common enteropathogen associated with diarrhoea in piglets from 5 days of age until weaning.

The use of toltrazuril for the prevention of coccidiosis in piglets before weaning.

To determine the efficacy of toltrazuril as a prophylactic treatment for coccidiosis in piglets caused by Isospora suis (I suis), a single 1.0 mL dose of toltrazuril was administered orally to 1056 piglets between 3 and 6 days of age, in 5 piggeries. Prophylactic treatment of piglets reduced the occurrence of coccidiosis in litters from 71% to 22%. The number of antibacterial treatments given and the number of piglets affected per litter were also significantly reduced, resulting in some improvement in growth rates to weaning. The severity of diarrhoea was significantly reduced, as was the amount of oocyst excretion. The number of days that piglets excreted oocysts in the faeces was reduced from 4.9 days to 2.5 days. The detection of I suis in piglets with diarrhoea was reduced from 84% in the untreated piglets to 6% in the piglets given the prophylactic treatment.

Causes of preweaning mortality on a large intensive piggery.

Causes of preweaning mortality were examined on a large intensive piggery. Diagnosis was made using comprehensive clinical histories combined with post-mortem data. Two thousand four hundred and twenty-six piglets were born in 238 litters. Pre-parturient and parturient losses were 2.9% and 5.4% of the total numbers of piglets born. Birth to weaning mortality was 11.3%. Among piglets born alive, overlaying was the most frequent cause of death (2.1%), followed by deaths due to diarrhoea (1.7%), anaemia (1.2%), savaging (1.1%) and losses of small weak piglets (0.9%). Most deaths, including stillbirths, were associated with below average birth weight, and two-thirds of all deaths of liveborn pigs occurred within 4 days of birth. Increased litter size resulted in decreased birth weights, an increased percentage of stillborn piglets and mummified foetuses, but duration of parturition was not affected. Stillborn piglets were born late in the litter and after a longer interval between pigs born (interpig interval). Over 70% of deaths due to overlay were in previously healthy piglets, but some were associated with illness of the sow (18%) or both sow and piglet (3%). Savaging was confined mainly to first parity sows and was responsible for 20% of all deaths in these litters. Sixty-two per cent of all piglets with a birth weight of less than 800g were stillborn or died before weaning compared with 18.7% mortality for all piglets. Anaemia in piglets was considered to be due to umbilical haemorrhage. Anaemic piglets had a 36% mortality to weaning compared with 10% for non-anaemic piglets.(ABSTRACT TRUNCATED AT 250 WORDS)

Pathogenicity of Vietnamese enterotoxigenic Escherichia coli strains in colostrum-deprived one-day-old piglets.

Preweaning colibacillosis is a major cause of economic loss to the swine industry in Vietnam. The aim of this study was to examine the enteropathogenicity of representative enterotoxigenic Escherichia coli (ETEC) strains obtained during an earlier epidemiologic survey conducted in five provinces in North Vietnam. This included isolates belonging to serotype O8 that produced heat-stable and heat-labile enterotoxins but did not produce any of the recognized fimbriae (F4, F5, F6, F41, F18). In vitro hemagglutination (unique mannose-resistant hemagglutination activity with guinea pig, sheep, human, and chicken red blood cells at 37 degrees C, but not at 18 degrees C) and enterocyte brush border attachment assays suggested that the F- ETEC strains produced an unidentified colonization factor that promoted adherence to the intestinal epithelium. Colostrum-deprived 1-day-old piglets challenged with an F- strain (1-2 x 10(9) bacteria) developed acute watery diarrhea within 4 hours of inoculation and suffered up to 20% weight loss, with comparable severity to piglets challenged with conventional F4 and F5 strains. At necropsy, viable counts and histopathologic examination of intestinal sections demonstrated colonization of the duodenum, jejunum, and ileum by F4-positive strains. In comparison, the F- and F5-positive strains attached exclusively to the ileum. Transmission electron micrographs of negatively stained F- cells grown at 37 degrees C demonstrated the presence of fimbriae. These results confirm the presence of a potentially new pathogenic ETEC fimbrial type in piggeries in Vietnam, with a unique hemagglutination property and attachment characteristics similar to ETEC bearing F5 fimbriae.