Spotted Fevers & Typhus Fever in Tamil Nadu (Commentary‪)‬

Rickettsia and Orientia represent the genera of causative microorganisms of some of the most covert reemerging diseases of the present times. These genera are morphologically and biochemically similar to other Gram-negative bacteria. The fastidious bacterial organisms are obligate intracellular parasites. Although rickettsial species are arthropod-associated bacteria, they are also frequently capable of infecting vertebrates, including humans, usually as accidental hosts. The genus Rickettsia is classically separated into the typhus group (TG) and the spotted fever group (SFG) based on the presence of distinct group lipopolysaccharide (LPS) antigens. The typhus group includes two human pathogens, R. prowazekii and R. typhi. SFG contains more than 30 diverse genotypes, which cause at least 13 different diseases or pathological syndromes in humans. Orientia tsutsugamushi is the aetiological agent of scrub typhus, also known as tsutsugamushi disease. It is a single species that comprises of many antigenic and genotypic variants (1). Looking back, we find examples of rickettsial diseases killed more people than the actual war (2). Rickettsial diseases are widely distributed throughout the world and many recent reports suggest to their continued presence in several parts of the Indian subcontinent, particularly that of scrub typhus (3-8). Rickettsial diseases are generally incapacitating notoriously difficult to diagnose, and untreated cases can have fatality rates as high as 30-35 per cent. Thus, the reported historical numbers of cases of infections with rickettsiae are probably not very accurate and are known to be severely underreported. When diagnosed properly, they are often easily treated but, lack of definitive diagnostic tools and the hazards of handling these microorganisms aggravate the difficulties of diagnosis and treatment.