Diagnosis of spotted fever groupRickettsiainfections: the Asian perspective

Abstract

Spotted fever group rickettsiae (SFG) are a neglected group of bacteria, belonging to the genus Rickettsia, that represent a large number of new and emerging infectious diseases with a worldwide distribution. The diseases are zoonotic and are transmitted by arthropod vectors, mainly ticks, fleas and mites, to hosts such as wild animals. Domesticated animals and humans are accidental hosts. In Asia, local people in endemic areas as well as travellers to these regions are at high risk of infection. In this review we compare SFG molecular and serological diagnostic methods and discuss their limitations. While there is a large range of molecular diagnostics and serological assays, both approaches have limitations and a positive result is dependent on the timing of sample collection. There is an increasing need for less expensive and easy-to-use diagnostic tests. However, despite many tests being available, their lack of suitability for use in resource-limited regions is of concern, as many require technical expertise, expensive equipment and reagents. In addition, many existing diagnostic tests still require rigorous validation in the regions and populations where these tests may be used, in particular to establish coherent and worthwhile cut-offs. It is likely that the best strategy is to use a real-time quantitative polymerase chain reaction (qPCR) and immunofluorescence assay in tandem. If the specimen is collected early enough in the infection there will be no antibodies but there will be a greater chance of a PCR positive result. Conversely, when there are detectable antibodies it is less likely that there will be a positive PCR result. It is therefore extremely important that a complete medical history is provided especially the number of days of fever prior to sample collection. More effort is required to develop and validate SFG diagnostics and those of other rickettsial infections.

Serological evidence indicates widespread distribution of rickettsioses in Myanmar

“…A potential limitation of our study could be cross-reactivity between TG and SFG antibodies (La Scola and Raoult, 1997;Robinson et al, 2019). However, in our study we found that only three participants were seropositive for both TG and SFG, indicating that cross-reactivity between different rickettsial groups with IFA was unlikely.…”

Rickettsia africae an Agent of African Tick Bite Fever in Ticks Collected from Domestic Animals in Eastern Cape, South Africa

“…Spotted fever group rickettsiae (SFGR) are emerging infectious diseases with global distribution that are caused by bacteria of the genus Rickettsia. These zoonotic diseases are transmitted by ticks' vectors among wild and domestic animals [21]. Domestic animals and humans are accidental dead end hosts.…”

Molecular detection of Rickettsia in fleas from micromammals in Chile

“…These sequences are closely related to R. hoogstraalii, R. asembonensis and R. felis, all of which are members of the spotted fever group rickettsiae (SFG) [28,29,38]. The SFG consists of > 30 species that can be found worldwide, most of them with pathogenic effects on humans [44]. Our analysis showed a close relationship with R. hoogstraalii, a widely distributed bacterium that is still unknown for its pathogenicity in humans.…”