Four shed-lambing operations in western Colorado were monitored during the 1984 spring lambing season to determine the causes and rates of perinatal lamb mortality. The number of lambing ewes per flock ranged from 513 to 1,712, and lambing percentages ranged from 131 to 180%. Overall perinatal lamb mortality ranged from 8.2 to 12.2%. Most lamb deaths occurred during parturition or within 24 hours after parturition. More than 85% of all lamb deaths were in lambs born to ewes having 2 or more lambs. The leading causes of lamb death were starvation, dystocia, stillbirth (unknown cause), and infectious diseases. A wheel model was used to categorize factors causing lamb deaths into 4 groups: physical, social, host, and biological, and to present data on perinatal lamb mortality in a simple visual model. In all flocks, social and biological factors resulted in most of the lamb deaths. On the basis of our findings, we suggest that interventions designed to improve ewe-lamb bonding and to reduce infectious agents and the incidence of prolonged parturition may reduce lamb mortality.

Pilus-mediated adherence is a virulence attribute of Moraxella bovis. Several pilus types have been shown to exist among strains of this bacterium, but correlation between pilus type and specific field cases of the disease has not been done. During the summer of 1987, an epizootic of infectious bovine keratoconjunctivitis was reported in 7 Iowa counties. Eight isolates of M bovis were secured from 12 episodes studied. All 8 of the isolates were nearly homogeneous in biochemical properties and had the same plasmid biotype. Pilus typing performed by immunofluorescence and immunogold electron microscopy identified a single new pilus type among 5 of the 8 isolates. This pilus type was identified in field cases that developed within a narrow time frame and over large distances. The implication of these findings is that infectious bovine keratoconjunctivitis epizootics may be associated with emergence of a novel pilus type, and that rapid dissemination over wide distances can occur, presumably by transportation of carrier cattle.

Immunoglobulin reactions to Salmonella dublin in serum and milk from 4 groups of lactating cows were measured by an indirect ELISA. The groups consisted of (1) cows that were natural carriers of S dublin in the mammary gland, (2) experimentally infected cows that did not become carriers, (3) cows inoculated with a commercial S dublin bacterin, and (4) cows used as S dublin-negative controls. Milk and serum samples were obtained at monthly intervals. Models for predicting carrier status were developed by use of stepwise logistic regression. Independent variables consisted of serum and milk IgG and IgM titers to S dublin lipopolysaccharide and a ratio of IgG to IgM. The utility of a single sample vs multiple samples obtained at 1-month or 2-month intervals was tested by comparison of goodness-of-fit X2 P values for 8 models predicting carrier status. Immunoglobulin reactions specific to S dublin were a significant predictor of carrier status (P < 0.001). Serum IgG titers specific for S dublin were the most important variable for predicting carrier status. Two serum IgG titers to S dublin obtained 2 months apart was a better predictor of carrier status than measurement of the IgG:IgM ratio from a single serum sample. Immunoglobulin recognizing S dublin epitopes also were detected in milk samples. In milk, performing 2 ELISA 60 days apart to determine IgG and IgM reactions to S dublin appeared to be useful for the prediction of carrier status, but was not as accurate as models for serum immunoglobulin reactions.

This study evaluated the epizootiological characteristics of equine coital exanthema (ECE) in South Korea. A PCR test was used to determine the equine herpesvirus 3 (EHV-3) release period, excretion by suckling foals, morbidity rate, effect on fertility, and onset of breeding partner after treatment. The morbidity rate of ECE based on clinical symptoms was 8.3% (2/24) for stallions and 10.8% (45/416) for mares, and 29 of 45 (64.4%) animals were positive on the PCR test. Ten (22%) broodmares had symptoms before breeding, while 26 (58%) had symptoms after breeding. Nine (20%) mares had uncertain coverage periods and occurrence times. Suckling foals had no clinical findings and EHV-3 was not detected in their nostrils, although it was detected on teasers. No lesions were observed in the clitoral fossa on broodmares, although EHV-3 was detected by PCR. The period of EHV-3 emission was 22~23, 18~19, 6, and 58 days in stallions, broodmares, teasers, and mares with a mixed E. coli-like infection, respectively. ECE had no negative effects on the breeding capability of stallions and no symptoms were observed in broodmares after recovering from ECE.

Porcine reproductive and respiratory syndrome (PRRS) is the most economically important viral infectious disease in pig populations worldwide. This study was conducted to better understand the epidemic and dynamics of PRRS virus (PRRSV) on each farm and to evaluate the risk of PRRSV infection in Korea. Interviews with pig farmers were carried out to obtain PRRS vaccination programmes in 60 pig farms throughout Korea. Blood samples were also collected from the 59 pig farms to investigate outbreak patterns of each farm. Vaccination against PRRS was performed in 16.7% farms for breeding pigs and 8.3% of farm for nursery pigs. According to the seroepidemiological analysis, 56 (94.9%) out of 59 farms were considered to be affected by PRRSV infection. The results revealed that 68.9% of sows tested were seroconverted and interestingly, gilt herds had the highest seropositive rate (73%), suggesting that gilts may play a key role in PRRSV transmission in sow herds. Among the PRRS-affected piglet herds, 33 (55.9%), 14 (23.7%) and 6 (10.2%) farms were initially infected with PRRSV during the weaning, suckling and nursery period, respectively. It seems likely, therefore, that PRRSV infection predominantly occurs around the weaning period in piglet herds. Based on antibody seroprevalence levels in both sow and piglet groups, we were able to classify patterns of PRRSV infection per farm unit into 4 categories; category 1 (stable sow groups and non-infected piglet groups), category 2 (unstable sow groups and non-infected piglet groups), category 3 (stable sow groups and infected piglet groups), and category 4 (unstable sow groups and infected piglet groups). Our data suggested that 43 (72.9%) farms were analysed to belong to category 4, which is considered to be at high-risk for PRRS outbreak. Taken together, our information from this study will provide insight into the establishment of an effective control strategy for PRRS on the field.