Volume 53, Issue 4
  • ISSN: 0002-9637
  • E-ISSN: 1476-1645



Twenty-two Costa Rican dairy herds were actively monitored for vesicular diseases between November 1991 and March 1992, in anticipation of the annual dry season occurrence of vesicular stomatitis (VS). Thirty-nine confirmed cases of VS were concentrated on nine farms, resulting in an average herd incidence rate of 11.1% of mature cattle for the affected farms, or 2.6% for all farms. Affected cattle were generally older (average age = 5.4 years), with seven-year-old cows having the highest age-specific incidence rate (6.5%). The New Jersey serotype of VS was diagnosed for all but four cases, primarily manifesting as teat vesicles. Cases had high acute and convalescent antibody titers for both major VS serotypes, New Jersey and Indiana, with significant titer increases after clinical disease. Screening and multiple variable regression analyses of 140 cow, farm, and ecologic variables revealed that clinical disease was significantly associated with cows being in lactation, and with higher acute antibody titers to serotype Indiana, but not with any predisposing diseases. Significant farm factors were the presence of poultry and a longer calving interval on the farm, but not higher rates of other diseases. According to a prior epidemiologic hypothesis, two ecologic factors were forced to be included into the farm model: the reported presence of sand flies, and a higher proportion of the farm being in forest land, with subsequent stepwise regression. The resulting model containing only the two forced variables was significant ( < 0.003) and correctly classified 78% of farms into the correct group, as compared with 79% for the final stepwise model. Study results suggested that the occurrence of clinical VS on a farm was more likely related to ecologically dependent vector transmission to older lactating animals, rather than to predisposing diseases that may immunocompromise affected animals. This was the first prospective case-control study aimed at finding host and ecologic risk factors associated with an outbreak of clinical VS.


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