Seroepidemiological study of outdoor recreationists' exposure to spotted fever group Rickettsia in Western Australia

Leptospira spp. and Rickettsia spp. as pathogens with zoonotic potential causing acute undifferentiated febrile illness in a central-eastern region of Peru

OBJETIVE

this study was to determine the relationship between acute febrile illness and bacterial pathogens with zoonotic potential that cause emerging and re-emerging diseases in a central-eastern region of Peru.

RESULTS

Out of the 279 samples analyzed, 23 (8.2%) tested positive for infection by Rickettsia spp., while a total of 15 (5.4%) tested positive for Leptospira spp. Women had a higher frequency of infection by Rickettsia spp., with 13 cases (53.3%), while men had a higher frequency of infection by Leptospira spp., with 10 cases (66.7%). The most frequently reported general symptom was headache, with 100.0% (n = 23) of patients with Rickettsia (+) and 86.7% (n = 13) of patients with Leptospira (+) experiencing it. Arthralgia was the second most frequent symptom, reported by 95.6% (n = 22) and 60% (n = 9) of patients with Rickettsia (+) and Leptospira (+), respectively. Myalgia was reported by 91.3% (n = 21) and 66.7% (n = 10) of patients with Rickettsia (+) and Leptospira (+), respectively. Retroocular pain, low back pain, and skin rash were also present, but less frequently. Among the positives, no manifestation of bleeding was recorded, although only one positive case for Leptospira spp. presented a decrease in the number of platelets.

Serological Evidence of Exposure to Spotted Fever Group and Typhus Group Rickettsiae in Australian Wildlife Rehabilitators

Rickettsioses are arthropod-borne zoonotic diseases, several of which occur in Australia. This study aimed to assess the exposure levels and risk factors for Rickettsia spp. among Australian wildlife rehabilitators (AWRs) using serology, PCR and a questionnaire. Antibody titres against Spotted Fever Group (SFG), Typhus Group (TG) and Scrub Typhus Group (STG) antigens were determined using an immunofluorescence assay. PCR targeting the gltA gene was performed on DNA extracts from whole blood and serum. Logistic regression was used to identify risk factors associated with seropositivity. Of the 27 (22.1%; 27/122) seropositive participants all were seropositive for SFG, with 5/27 (4.1%) also positive for TG. Of the 27 positive sera, 14.8% (4/27) were further classified as exposure to R. australis, 3.7% (1/27) to R. honei, 3.7% (1/27) to R. felis and 77.8% (21/27) were classified as ‘indeterminate’—most of which (85.7%; 18/21) were indeterminate R. australis/R. honei exposures. Rickettsia DNA was not detected in whole blood or serum. Rehabilitators were more likely to be seropositive if more than one household member rehabilitated wildlife, were older than 50 years or had occupational animal contact. These findings suggest that AWRs are at increased risk of contracting Rickettsia-related illnesses, however the source of the increased seropositivity remains unclear.

A Concise Review of the Epidemiology and Diagnostics of Rickettsioses: Rickettsia and Orientia spp

Rickettsioses are globally distributed and caused by the family Rickettsiaceae, which comprise a diverse and expanding list of organisms. These include two genera, Rickettsia and Orientia Serology has been traditionally the mainstay of diagnosis, although this has been limited by cross-reactions among closely related members and diminished sensitivity/utility in the acute phase of illness. Other techniques, such as nucleic acid amplification tests using blood specimens or tissue swabs/biopsy specimens, sequencing, and mass spectrometry, have emerged in recent years for both pathogen and vector identification. This paper provides a concise review of the rickettsioses and the traditional and newer technologies available for their diagnosis.

Tick-borne infectious diseases in Australia

Tick bites in Australia can lead to a variety of illnesses in patients. These include infection, allergies, paralysis, autoimmune disease, post-infection fatigue and Australian multisystem disorder. Rickettsial (Rickettsia spp.) infections (Queensland tick typhus, Flinders Island spotted fever and Australian spotted fever) and Q fever (Coxiella burnetii) are the only systemic bacterial infections that are known to be transmitted by tick bites in Australia. Three species of local ticks transmit bacterial infection following a tick bite: the paralysis tick (Ixodes holocyclus) is endemic on the east coast of Australia and causes Queensland tick typhus due to R. australis and Q fever due to C. burnetii; the ornate kangaroo tick (Amblyomma triguttatum) occurs throughout much of northern, central and western Australia and causes Q fever; and the southern reptile tick (Bothriocroton hydrosauri) is found mainly in south-eastern Australia and causes Flinders Island spotted fever due to R. honei. Much about Australian ticks and the medical outcomes following tick bites remains unknown. Further research is required to increase understanding of these areas.

New Foci of Spotted Fever Group Rickettsiae Including Rickettsia honei in Western Australia

We describe the first reported case of spotted fever group rickettsiosis in Western Australia, and two cases of probable Rickettsia honei from a new geographic focus. These findings highlight the need to raise awareness of ricksettsial infection among local clinicians as well as those treating visitors to this region, important for outdoor recreation.

Rickettsia Detected in the Reptile Tick Bothriocroton hydrosauri from the Lizard Tiliqua rugosa in South Australia

Rickettsiosis is a potentially fatal tick borne disease. It is caused by the obligate intracellular bacteria Rickettsia, which is transferred to humans through salivary excretions of ticks during the biting process. Globally, the incidence of tick-borne diseases is increasing; as such, there is a need for a greater understanding of tick-host interactions to create more informed risk management strategies. Flinders Island spotted fever rickettsioses has been identified throughout Australia (Tasmania, South Australia, Queensland and Torres Strait Islands) with possible identifications in Thailand, Sri Lanka and Italy. Flinders Island spotted fever is thought to be spread through tick bites and the reptile tick Bothriocroton hydrosauri has been implicated as a vector in this transmission. This study used qPCR to assay Bothriocroton hydrosauri ticks collected from Tiliqua rugosa (sleepy lizard) hosts on mainland South Australia near where spotted fever cases have been identified. We report that, although we discovered Rickettsia in all tick samples, it was not Rickettsia honei. This study is the first to use PCR to positively identify Rickettsia from South Australian Bothriocroton hydrosauri ticks collected from Tiliqua rugosa (sleepy lizard) hosts. These findings suggest that B. hydrosauri may be a vector of multiple Rickettsia spp. Also as all 41 tested B. hydrosauri ticks were positive for Rickettsia this indicates an extremely high prevalence within the studied area in South Australia.

Distribution of rickettsioses in Oceania: past patterns and implications for the future

Rickettsioses present a threat to human health worldwide, but relatively little is known on their epidemiology and ecology in Oceania. These bacteria are the cause of potentially fatal febrile illnesses in humans (categorized into scrub typhus, typhus group and spotted fever group rickettsioses). They are transmitted by arthropod vectors such as ticks, mites, fleas and lice, which are associated with vertebrate host animals including rodents and companion animals. We conducted a search in the scientific and grey literature of Rickettsia spp. and Orientia tsutsugamushi within the Oceania region. Human case reports, human serosurveys and PCR-based testing of vectors and host animals reviewed here highlight the widespread distribution of these pathogens in the region, with the majority of human serological and vector surveys reporting positive results. These findings suggest that rickettsioses may have a significantly higher burden of disease in Oceania than is currently appreciated due to diagnostic challenges. Furthermore, consideration of the ecology and risk factors for rickettsioses reported for Oceania suggests that their importance as a cause of undifferentiated acute febrile illness may grow in the future: environmental and social changes driven by predicted climate change and population growth have the potential to lead to the emergence of rickettsioses as a significant public health problem in Oceania.