Seroepidemiology of scrub typhus among patients with acute febrile illness attending tertiary care hospital, Chitwan, Nepal.

Thesis Report.

ABSTRACT:
Background :Scrub typhus is an acute febrile illness caused by Orientia tsutsugamushi, transmitted to humans by the bites of the larva of Trombiculid mites. Orientia tsutsugamushi is an obligate intracellular gram-negative bacterium, that has a large number of serotypes. Human being are the accidental hosts for the pathogen. Scrub typhus infection is one of the major global public health problem. It is becoming wide increasing prevalence and also reported as an outbreak after the earthquake in Nepal.

Objectives:The study was aimed to determine the seroprevalence of Scrub typhus among febrile patients attending Chitwan Medical College Teaching Hospital (CMC-TH), Chitwan, Nepal.

Materials and Methods: A hospital based prospective study was conducted on patients with suspected Scrub typhus cases in CMC-TH from 1st July 2016 to 30th June 2017. After taking informed consent, blood samples were collected from acute febrile illness patients. The antibody detection for Scrub typhus was done by Enzyme Linked Immunosorbent Assay (ELISA) and Weil-Felix test. ELISA was a qualitative test for the detection of Immunogolobulin M (IgM) antibodies to Orientia tsutsugamushi from the serum sample.

Results: Among 1797 enrolled individuals, 524 (29.2%) were found to be infected cases of Scrub typhus, comprising of 314 (60.0%) females and 210 (40.0%) males. In relationship to age group, the distribution of Scrub typhus infected cases were found to be maximum (37.2%) between 51-60 years of age group, while minimum cases were found in > 70 years of age group. The study showed that, the high prevalence was noted in farmers (37.8%). Likewise, seasonal variation showed that the majority (57.7%) of the infected individuals were found in the month of July. Fever, was the most common (100%) clinical features seen in the study. Other clinical presentations were found in a descending order like anorexia (64.7%), headache (54.6%), abdominal pain (19.8%), vomiting (19.3%), lymphadenopathy (16.6%), jaundice (9.4%), eschar (6.5%) and seizures (6.1%). Similarly, the laboratory parameters In Scrub typhus positive cases (46.9%) presented lower level of haemoglobin, (23.5%) patients showed leucocytosis, (73.7%) patients showed thrombocytopenia. Likewise, the activity of transaminase, enzymes, Alanine Transminase (ALT) and Aspartate Transaminase (AST) were also found to be increased in majority (7.00 and 76.1%) of infected cases respectively. Considering ELISA as a reference techinique, the sensitivity and specificity of Well-Felix test was 42.8% and 86.4% respectively in the study.

Conclusion: The study concluded that, there was high prevalence rate of (29.2%) Scrub typhus among acute febrile illnesses. So, more sustain and control. Eschar was an important clue to diagnosis of Scrub typhus. However, it was less common (6.5%) features in Scrub typhus infection. The present study shows Well-Felix (OS-K strain) test is a satisfactory method where the, sensitivity and specificity was 42.8% and 86.4% respectively. Rapid Well-Felix test and specific diagnostic methods using ELISA can be carried out timely for early diagnosis of Scrub typhus in patients with acute febrile illness in developing countries like Nepal.