Seroepidemiology of Mycoplasma hyopneumoniae in pigs from farrow-to-finish farms.

A prospective study was carried out on three intensive farrow-to-finish farms. The aims were to estimate the incidence of Mycoplasma hyopneumoniae infection, to determine when pigs become infected and the pattern of transmission of infection and to verify the relationship between seroconversion and clinical signs. One batch of pigs per farm was followed from farrowing-to-slaughter. Blood samples were taken at 10, 27, 70, 94, 125 and 147 days of age, from 44, 48 and 44 pigs per farm. Colostrum and blood samples were also taken from the sows. Animals were checked clinically once a week and coughing rates were recorded. Antibodies against M. hyopneumoniae were detected by a blocking ELISA. At 27, 70 and 94 days of age most pigs on the three farms were seronegative, suggesting that no circulation of M. hyopneumoniae occurred during the growing period. Thereafter, a high proportion of pigs seroconverted, indicating that infection occurred soon after the transfer of the animals to the finishing houses. Differences were detected between farms in the incidence of seroconversion. Seropositive pigs were widely distributed among the finishing pens, suggesting that in addition to direct contact, other methods of transmission, such as indirect or airborne transmission, may have been important. Coughing started at around the same time as seroconversion. The results showed that the critical period for the transmission of M. hyopneumoniae is around the beginning of the finishing period, when pigs have low concentrations of antibodies against the agent.

Monitoring antibodies to Mycoplasma hyopneumoniae in sow colostrum--a tool to document freedom of infection.

In a survey in Finland in 1995, 14,919 colostral whey samples from 530 farrowing herds were analysed by a monoclonal blocking-ELISA to detect antibodies to Mycoplasma hyopneumoniae (M. hyopneumoniae). Antibodies were detected in 274 (1.8%) samples and in 42 herds (7.9%). The median prevalence of sows with antibodies in seropositive herds was 28.2% (range, 2.7-100%). According to clinical and pathological follow-up in finishing herds in 1996, all of the farrowing herds which were seronegative in 1995, were truly non-infected with M. hyopneumoniae. In acutely infected herds, samples collected earlier than 2 h after farrowing were 3 times more likely to contain antibodies than samples collected 2-12 h after farrowing (odds ratio, 3.0; 95% CI, 1.4-6.6). Repeated freezing or spoilage of the colostrum samples did not cause biologically relevant problems for the ELISA. Antibodies to M. hyopneumoniae were shown to persist up to 3 years in some sows. As a conclusion, colostrum samples were very sensitive samples for the screening of herds for M. hyopneumoniae infection and possibly also for a regular surveillance.

The prevalence of Mycoplasma hyopneumoniae in pig herds in western Finland based on the demonstration of antibodies in colostrum by ELISA.

Swine enzootic pneumonia causes heavy economical losses in fattening herds. The aim of this study was to get an estimate of the prevalence of Mycoplasma hyopneumoniae in the province of Vaasa in Western Finland. There were 112 farrowing herds randomly chosen for a survey. Farmers were asked to milk colostrum samples from every sow. Owners of 22 herds did not send enough samples for a herd diagnosis. Altogether 1773 samples (mean 18.1 samples/herd) were analysed in an indirect ELISA for antibodies to Mycoplasma hyopneumoniae. Thirty-five herds were concluded to be infected with Mycoplasma hyopneumoniae. In these herds the mean prevalence of samples with antibodies was 16.3% (range 2.3%-70.0%, median 8.6%). The infected herds were significantly larger than the rest of the herds (no. of sows 27.0 vs. 18.4 respectively). The true prevalence of Mycoplasma hyopneumoniae infection in the province of Vaasa was estimated to be somewhat lower than the apparent prevalence of 39%. The application of colostrum serology is discussed.

Seroepidemiology of mycoplasmal pneumonia of swine in Japan as surveyed by an enzyme-linked immunosorbent assay.

Antibodies to Mycoplasma hyopneumoniae were surveyed by enzyme-linked immunosorbent assay (ELISA) on serum, colostrum and milk samples collected from sows and on sera of growing/finishing pigs in Japan. Only one of 196 specific-pathogen-free sows induced a low ELISA value, while 72% of 411 sows from conventional herds were seropositive. A seropositive rate in the conventional sows gradually decreased with an increase in farrowing frequency or with age. In 3267 growing/finishing pigs ranging in age from one to six months, a seropositive rate increased remarkably from the age of 4 months onwards, reaching the maximum at the age of 6 months. A survey conducted on 42 conventional farms revealed that the highest seroconversion occurred when pigs were 4 months of age. The level of maternal antibodies was proportional to that of the dam's colostral antibodies. After maternal antibodies waned, active immunity in newborn piglets from dams with high colostral antibodies appeared earlier and higher than that in piglets from dams with low colostral antibodies. In 950 slaughter pigs, there was a correlation between seropositiveness and the presence of pneumonic lesions, but the ELISA value did not correlate with the degree of the lesions. Pigs that were raised under unfavorable environmental conditions developed pneumonic lesions more frequently than pigs rearing under better conditions, regardless of their immune status. These results suggested that M. hyopneumoniae and some secondary respiratory pathogens may have been involved in the development of these pneumonias.