Chlamydial infection in cattle: The burden of proof?

Seroprevalence studies on animal chlamydiosis amongst ruminants in five states of India

BACKGROUND AND AIM

Animal chlamydiosis, caused by different chlamydial species, is characterized by clinical or subclinical disease manifestations in cattle, buffalo, ovine, caprine and wild animal species. Animal chlamydiosis often remains underdiagnosed or undiagnosed, and its status in many parts of India is still unknown. Hence, the present study was conducted to determine the seroprevalence of animal chlamydiosis amongst ruminant livestock species of five states of India.

MATERIALS AND METHODS

Totally, 2127 randomly selected serum samples collected from ruminant livestock species viz. cattle (n=430), buffaloes (n=429), sheep (906) and goats (n=362), were tested by agar gel precipitation test for chlamydiosis between 2002 and 2011. Precipitating antigen was prepared from locally isolated strain of Chlamydia psittaci after treatment with sodium deoxycholate.

RESULTS

The chlamydial seroprevalence detected amongst ruminants in five states of India was: Himachal Pradesh: Cattle-10.90%, sheep-10.60% and goats- 22.46%; Punjab: Cattle-1.45%; Andhra Pradesh: Cattle-2.80%, buffaloes-0.93%, sheep-8.90% and goats-9.46%; Maharashtra: goats-8.33%; Jammu and Kashmir: sheep-12.50%. The mean seroprevalence values of each animal species are: Cattle-4.65%, buffaloes-0.93%, sheep-9.82% and goats-19.33%.

CONCLUSION

The results indicate the endemic nature of animal chlamydiosis across five states in India. Hence, it requires further extensive studies in other parts of India also using chlamydial species-specific diagnostics to ascertain overall countrywide prevalence of the disease. The zoonotic nature of the chlamydiae of ruminant origin further adds significance to such prevalence studies.

Dose-dependent effects of Chlamydia psittaci infection on pulmonary gas exchange, innate immunity and acute-phase reaction in a bovine respiratory model

The respiratory pathogen Chlamydia psittaci naturally occurs in bovine herds and was recently shown to impair calf health in a dose-dependent manner. The aim of this study was to determine whether the functional consequences and immunological reactions of infection were dose related by quantifying the consequences of acute respiratory chlamydial infection on respiratory signs, disturbances of pulmonary gas exchange, response of the innate immune system, and acute-phase reaction. Fourteen calves were challenged intrabronchially with different C. psittaci doses (from 10(6) to 10(9)inclusion-forming units (ifu) per animal). Ten controls received either UV-inactivated chlamydiae or cell culture medium. Compared to the controls, all animals challenged with live C. psittaci developed hypoxaemia linked to reduced haemoglobin oxygen saturation, increased alveolar-arterial oxygen partial pressure difference (A-aO2) and pulmonary shunt, with symptoms following a dose-dependent pattern. Increases in lipopolysaccharide-binding protein (LBP) and leukocytes were also dose-dependent and accompanied by a regenerative left shift in neutrophil granulocytes. With the exception of LBP, which reflected the load of chlamydial cell components in the host, pathophysiological reactions were only detected in calves challenged with viable chlamydiae. These results indicate that the pathophysiological consequences of respiratory C. psittaci infections are strongly dependent on the challenge dose of chlamydiae. For further studies, challenge doses between 10(6) and 10(8)ifu/calf are recommended.