MVSc

The magnitude of the prevalence of ahlamydial infections in the livestock in Kerala was assessed by screening the smears of various clinical materials after staining, isolation using chicken ebbryos and guinea pigs and serologically by passive haemagglutination test.
The results obtained were discussed correlating to the managemental practises in the organised herds and agroclimatic conditions.
A total of 71 biosample comprising 17 bovine abortion materials, 15 bull semen, 6 seminal vesicular secretion, one synovial fluid from a calf, 5 caprine abortion material, 15 carpine pneumonic lungs, 5 samples from perinatal mortality in kids, 4 ovine lung tissue and one conjunctival washings from a buffalo were utilised for screening the smears stained by Gimenez, Macchiavellos, modified Ziehi – Neelsen and Giemsa’s methods and for isolation purpose.
On screening the stained smears, one bovine abortion material, two bull semen, one caprine abortion material and three caprine pneumonic lesions were found positive for developmental forms of chlamydiae which could be discerned intra and extracytoplasmically. The overall prevalence rate by this method was 9.9% and species wise prevalence rates were 7.3% among cattle and 16% among goats.
Attempts for isolation resulted in the recovery of chlamydiae from two of 17 bovine abortion materials, four or 15 bull semen and two of 15 caprine pneumonic lungs. The overall prevalence based on isolation rate was 11.3% and species wise prevalence rates were 14.6% and 8% respectively for cattle and goats.
A total of 169 serum samples consisting of 92 from cattle, 67 from goats and 10 from sheep were screened serologically. Of these 21 from cattle, 13 from goats and one from sheep were found positive showing titres of 1:16 and above. The overall seroprevalence rate was found to be 20.7 % and species wise rates were 22.8%, 19.4% and 10% for cattle, goat and sheep.
On comparison the seropositivity rate was found greater than the cultural positivity rate and the rate of positive cases detected by stained smear examination of clinical materials was the least.
Among bovines the prevalence was found greater in the hill tracts than in the plains.
The mortality pattern and the extent of mobidity due to chlamydial infection were also studied by inoculating 6 – 7 day old chicken embroys and mice of two age group using strains that had undergone passages in chicken embryo two times and six times. In the case of chicken embryos it was observed that with increase in number of passage the pathogenicity of the strains got reduced, the time of mortality shifted from early death (within 3 – 7 days) to late death (beyond 8 days) and the double passaged strains caused greater mortality.
The lesions and tissue changes in the dead chicken ambryos were developmental retardation, haemorrhages, necrotic lesions in the liver, intense congestion of the yolk sac membrane which invariably contained unabsorbed watery yolk.
In the case of mice, younger age group (3 – 4 weeks) suffered greater mortality than older group (6 – 8 weeks). The lesions were mainly extensive pneumonia, congestion of the visceral organs and a yellowish fibrinous exudate on the peritoneal surface.
Latent or inapparent infection could be noted in some mice infected with the isolates and in some of the guinea pigs inoculated with the clinical materials which were, later on, proved positive for chlamydia. The animals on autopsy, revealed low degree of pneumonia.
The electron microscopic studies of three isolates revealed structures analogous to the chlamydial developmental forms.
The identity of the isolates was confirmed by fluorescent antibody staining technique and test of sensitivity to sulphadiazine. Following fluorescent antibody staining (FAT) two distinct developmental forms of the organism could be identified. The intracellular location of this agent could also be identified in the peritoneal macrophages following FAT, which revealed two district types of fluorescencing inclusions – type one as dense groupings of granular bodies at the polar region and type two as diffused polar fluorescence. None of the isolates was sensitive to sulphadiazine indicating that the isolates are Chlamydia psittaci.