We examined more than 2,800 human and animal sera for antibodies to four serogroups of Legionella pneumophila by using the microagglutination test. Antibody titers of ≥1:64 were considered positive. The occurrence of positive equine sera (31.4%) was significantly higher than the occurrence of positive sera in cattle (5.1%), swine (2.9%), sheep (1.9%), dogs (1.9%), goats (0.5%), wildlife (0%), and humans (0.4%). The highest titer measured in horses was 1:512. The occurrence of positive sera in horses was related directly to age. In horses ≤1,2 to 3, 4 to 7, 8 to 12, and ≥13 years old,the percentages of positive sera were 0, 10.1, 30.3, 4.9 and 58.1%, respectively. When we compared age-specific serogroup-specific rates in horses from Colorado and Pennsylvania, we found differences. With horses 8 to 12 and ≥13 years old, there was a significantly higher (P<0.05) occurrence of sera that reacted to serogroups II and III in horses from Pennsylvania. Of 242 positive sera, 43.8% reacted to a single serogroup (serogroup III or I most commonly), and 56.2% reacted to multiple serogroups (serogroups II and III or serogroups I, II, and III most commonly). A high percentage of seropositive horses suggested that horses are commonly infected with L. pneumophila or related organisms, and the age-specific rates of occurrence indicate that infection was related directly to duration of exposure. A definitive demonstration of equinine infection will depend on isolation of the agent and repetition of this serological study with antigens obtained from organisms isolated from horses.
|Number of pages||7|
|Journal||Journal of Clinical Microbiology|
|Publication status||Published - 1982 Jan 1|
All Science Journal Classification (ASJC) codes
- Microbiology (medical)