**2.4. Diagnosis of scrub typhus**

study, eschar was mostly found in the inguinal region. Different pattern of eschar distribution found in males and females due to the differences in skin folds, clothing and pressure points created by garments. The eschar not only has immense diagnostic relevance but is also impor-

Neurological involvement is often a prominent clinical manifestation of scrub typhus. However, they are still an unclear entity. Meningitis or meningoencephalitis can occur in upto one-fifth of affected patients. In the authors study, meningoencephalitis was found in 13.2% of scrub typhus patients [6]. The various neurological manifestations of scrub typhus [5] are

Meningitis has features of headache, vomiting, fever, neck stiffness, along with cerebrospinal fluid (CSF) pleocytosis. Altered sensorium and fever with CSF pleocytosis are features of enceph-

Neurological manifestations in scrub typhus does not occur in isolation but are accompanied by systemic features like jaundice, breathlessness, cough, renal impairment and in some cases, with multi-organ dysfunction. In the authors study [6] neurological manifestations were associated with lymphadenopathy (46.15%), jaundice (53.85%), pulmonary oedema (23.08%), oliguria (15.38%), hepatomegaly (38.46%) and splenomegaly (7.69%). Multi-organ dysfunction

The most common symptom of scrub typhus is fever. The fever is usually mild and accompanied by myalgia. In the authors study the mean duration of fever was 5.61 days, prior to

Headache is a common symptom in scrub typhus (46–77%). A severe holocranial headache almost invariably occurs and thereby helps in identifying suspected cases. Headache occurs

tant prognostically. Absence of an eschar is a risk factor for mortality [2].

64 Meningoencephalitis - Disease Which Requires Optimal Approach in Emergency Manner

alitis. Altered sensorium with fever but normal CSF is found in encephalopathy.

was found in 15.38% patients of scrub typhus with neurological manifestation.

as given in (**Table 1**).

meningoencephalitis presentation.

**Direct involvement** 1. Meningitis

2. Meningoencephalitis

3. Encephalitis 4. Encephalopathy

**Immune mediated** 1. Optic neuritis 2. Myelitis

4. Neuropathy

3. Acute-disseminated encephalomyelitis

**Table 1.** Neurological involvement in scrub typhus.

5. Seizure 6. Stroke

This is aided by serological tests in appropriate clinical setting.

Microimmunofluorescence is considered the test of choice. However, lack of fluorescent microscopes makes it difficult for most hospitals.

Latex agglutination, indirect haemagglutination, immunoperoxidase assay, ELISA and polymerase chain reaction (PCR) are also available. The nested PCR is more sensitive than the serological tests.

PCR can be used to detect rickettsial DNA in both blood and eschar samples. The PCR is targeted at the gene encoding the major 56-kDa antigen and/or 47-kDa surface antigen gene. The results are best within first week for blood samples.

ELISA (IgG and IgM) technique, particularly immunoglobulin M (IgM), capture assays are probably the most sensitive test available for rickettsial diagnosis. In cases of infection with *O. tsutsugamushi*, a significant IgM antibody titre is observed at the end of the first week, whereas IgG antibodies appear at the end of the second week.

Weil Felix test: the sharing of the antigen between rickettsia and proteus is the basis of this heterophile antibody test. Though this test lacks high sensitivity and specificity, it is inexpensive. The test should be carried out after 5–7 days of onset of fever.

However, due to the antigenic diversity of the pathogen, a battery of tests may be required for the diagnosis [1].

CSF analysis in scrub typhus meningoencephalitis reveals mild-to-moderate elevation in protein, low-to-normal glucose and mild degree of lymphocytic pleocytosis. By using nested PCR, the genotypes invading the central nervous system (CNS) may be identified. By this, it was suggested that the Karp and Boryong genotypes possibly invade the CNS more than other types [4]. In the author's study, tuberculous meningitis remained the close differential diagnosis of scrub typhus meningitis due to similar CSF findings [6]. However, CSF adenosine deaminase (ADA) may be helpful, as it is elevated >10 in tuberculous meningitis, unlike scrub typhus meningitis.

Neurological involvement in scrub typhus is usually associated with a normal MRI and nonspecific EEG slowing. Often MRI of brain in scrub typhus may reveal features of ischemic changes due to vasculitis or parainfectious demyelination [5].
