Investigation on the frequency of Chlamydia sp. infections in tits (Paridae)

A total of 788 cloacal and pharyngeal swabs were taken from 399 free-living, clinically healthy tits. Ten nestlings were examined by cloacal swabs only. Additionally, six dead tits were necropsied and various organs were collected for testing. All swabs and organ samples were tested for Chlamydia Chlamydia sp. was detected by immunofluorescence with FITC-conjugated monoclonal antibodies after 90 h incubation on Buffalo-Green-Monkey (BGM) cell cultures at 37 degrees C. Fifty-four per cent of 399 tits examined were Chlamydia positive. Chlamydia was detected in 154 of 399 pharyngeal swabs (39%) and in 144 of 389 cloacal swabs (37%). Blue tits (Parus caeruleus) were most frequently Chlamydia positive (70%), followed by great tits (Pants major) with 53% and marsh tits (Parus palustris) with 38%. No significant relationship was established between Chlamydia detection and time of the year, age, sex or size of birds at the time of sampling. Tits examined two or three times were intermittent shedders. Four of the 10 tit nestlings (Parus major) examined were already Chlamydia positive at the age of 10 days. Chlamydia was detected in four of six necropsied tits. The necropsies showed that all of the positive tits were cachectic. The livers of three of the four positive tits were pathologically changed and splenomegaly was observed in two of the four. No CEF (chick embryo fibroblast)-pathogenic viruses and no bacteria were found in these animals. This indicates that chlamydiosis was the only cause of death. Two of the Chlamydia sp. isolates from the dead tits produced cytopathic effects (cpe) in BGM cell cultures. These cytopathic isolates may be more virulent than the isolates from healthy tits, which did not cause visible alterations in BGM cell cultures. The results of this study and the frequent shedding of Chlamydia in healthy tits prove that most tits intermittently shed Chlamydia sp. as latent carriers, but that lethal Chlamydia infections can also occur in tits.