Seroprevalence of rickettsial infections and Q fever in Bhutan

<div><p>Background</p><p>With few studies conducted to date, very little is known about the epidemiology of rickettsioses in Bhutan. Due to two previous outbreaks and increasing clinical cases, scrub typhus is better recognized than other rickettsial infections and Q fever.</p><p>Methodology</p><p>A descriptive cross-sectional serosurvey was conducted from January to March 2015 in eight districts of Bhutan. Participants were 864 healthy individuals from an urban (30%) and a rural (70%) sampling unit in each of the eight districts. Serum samples were tested by microimmunofluorescence assay for rickettsial antibodies at the Australian Rickettsial Reference Laboratory.</p><p>Results</p><p>Of the 864 participants, 345 (39.9%) were males and the mean age of participants was 41.1 (range 13–98) years. An overall seroprevalence of 49% against rickettsioses was detected. Seroprevalence was highest against scrub typhus group (STG) (22.6%) followed by spotted fever group (SFG) rickettsia (15.7%), Q fever (QF) (6.9%) and typhus group (TG) rickettsia (3.5%). Evidence of exposure to multiple agents was also noted; the commonest being dual exposure to STG and SFG at 5%. A person’s likelihood of exposure to STG and SFG rickettsia significantly increased with age and farmers were twice as likely to have evidence of STG exposure as other occupations. Trongsa district appeared to be a hotspot for STG exposure while Punakha district had the lowest STG exposure risk. Zhemgang had the lowest exposure risk to SFG rickettsia compared to other districts. People living at altitudes above 2000 meters were relatively protected from STG infections but this was not observed for SFG, TG or QF exposure.</p><p>Conclusion</p><p>This seroprevalence study highlights the endemicity of STG and SFG rickettsia in Bhutan. The high seroprevalence warrants appropriate public health interventions, such as diagnostic improvements and clinical treatment guidelines. Future studies should focus on vector profiles, geospatial, bio-social and environmental risk assessment and preventive and control strategies.</p></div

Participants distribution by gender, occupation and location in different age groups (N = 864).

<p>Participants distribution by gender, occupation and location in different age groups (N = 864).</p

Baseline correlation of seropositivity with different variables.

<p>Baseline correlation of seropositivity with different variables.</p

Epidemiological factors associated with seropositivity to Scrub typhus group (STG) rickettsioses in Bhutan.

<p>Epidemiological factors associated with seropositivity to Scrub typhus group (STG) rickettsioses in Bhutan.</p

Overall seroprevalence of rickettsial infections in Bhutan.

<p>(STG, Scrub Typhus Group; SFG, Spotted Fever Group; TG, Typhus Group; QF, Q Fever).</p

Prevalence of rickettsial seropositivity in different districts of Bhutan.

<p>(U, Urban; R, Rural; T, Total).</p

Additional file 1 of Gaps and inconsistencies in the current knowledge and implementation of biosafety and biosecurity practices for rickettsial pathogens

Supplementary Material 1. Detailed pathogen biosafety evidence for Rickettsia spp. and Orientia spp

Under skilda fanor : berättelse från 1788-90 års krig

Additional file 2. Univariable assessment of the effect of risk factors on seroconversion against C. burnetii in goats

An O-Specific Polysaccharide/Tetanus Toxoid Conjugate Vaccine Induces Protection in Guinea Pigs against Virulent Challenge with Coxiella burnetii

Q fever is caused by the bacterium Coxiella burnetii and is spread to humans from infected animals especially goats, sheep and cattle, predominantly when giving birth. There is an effective human vaccine (Q-VAX) against Q fever, and although Q fever is a worldwide problem, the vaccine is only used in Australia due to difficulties associated with its use and the risk of adverse reactions. The desire to protect humans, particularly farmers and abattoir workers, from Q fever prompted the development of a new safe and effective human vaccine without all the difficulties associated with the current vaccine. Candidate vaccines were prepared using purified O-specific polysaccharide (OSP) extracted from the lipopolysaccharide of virulent (phase 1) C. burnetii, strain Nine Mile, which was then conjugated to a tetanus toxoid (TT) carrier protein. Two vaccines were prepared using OSP from C. burnetii grown in embryonated eggs (vaccine A) and axenic media (vaccine B). Vaccines with or without alum adjuvant were used to vaccinate guinea pigs, which were later challenged by intranasal inoculation with virulent C. burnetii. Both vaccines protected guinea pigs from fever and loss of weight post challenge. Post-mortem samples of the spleen, liver and kidney of vaccinated guinea pigs contained substantially less C. burnetii DNA as measured by PCR than those of the unvaccinated control animals. This study demonstrated that a C. burnetii OSP-TT conjugate vaccine is capable of inducing protection against virulent C. burnetii in guinea pigs. Additionally, OSP derived from C. burnetii grown in axenic media compared to OSP from embryonated eggs is equivalent in terms of providing a protective immune response