Ocular Manifestations of Scrub Typhus Induced Infection: A Comprehensive Review

Saptarshi Mukherjee, Senior Optometrist,

Centre for Sight, New Delhi, India

 

Abstract

Scrub typhus is a disease spread from animals to humans caused by the bacterium Orientia tsutsugamushi. It affects blood vessels throughout the body and can damage multiple organs. In severe cases, especially when the infection leads to bloodstream infection, ocular manifestations are becoming more common. These can affect both the anterior and posterior ocular structures. The disease causes damage to endothelial layer, leads to inflammation, and can result in microvascular thrombosis. Clinical manifestations range from conjunctival congestion and subconjunctival haemorrhage, to retinitis, retinal vasculitis, optic neuritis, and cranial nerve palsies. Early diagnosis and prompt treatment with the right antimicrobial therapy is very important to avoid permanent vision loss. This review summarises the current understanding of the pathophysiology, clinical presentation, diagnostic evaluation, and management of ocular manifestations associated with and without scrub typhus-induced septicaemia.

Introduction

Scrub typhus is a sudden illness that causes high fever and is caused by a bacteria called Orientia tsutsugamushi. It spreads when a person is bitten by infected chigger mites. This disease is common in a region known as the “tsutsugamushi triangle,” which includes parts of South and Southeast Asia, such as India, China, Japan, and the Western Pacific. It is now seen as a major cause of fever without a clear source and can lead to severe shock in tropical areas. ⁽¹⁾

The way the body reacts to scrub typhus mainly involves inflammation of blood vessels and the areas around them, caused when the bacteria invade the lining of blood vessels.
In severe cases, the infection can spread into the blood, leading to problems with multiple organs like the lungs, kidneys, liver, brain, and heart. ⁽²⁾ Eye involvement, which was not well known before, is now being studied more because it can threaten vision.

The eye can show several problems, such as redness of the eyelids, infection of the cornea, inflammation inside the eye, infection of the retina, swelling and inflammation of blood vessels in the retina, inflammation of the optic nerve, and weakness in certain nerves that control eye movement. ⁽³⁾

These eye issues are believed to happen because of damage to blood vessel walls, the body’s immune response, and injury to blood vessels caused by lack of blood flow.

Pathogenesis of Ocular Manifestations

The main way scrub typhus causes harm is by infecting blood vessel walls, which leads to widespread inflammation of blood vessels.

The bacteria infect the cells that line blood vessels and the cells that fight infection, causing blood vessels to leak and triggering the release of substances that cause inflammation. ⁽⁴⁾

Endothelial Injury and Vasculitis

Damage to blood vessel walls and inflammation can affect the retina and the part of the eye that supports it because these areas have a dense network of small blood vessels.
These changes can lead to fluid leakage, swelling, loss of blood flow, and bleeding in the retina. ⁽⁵⁾

Cytokine-Mediated Inflammation

High levels of inflammation factors, like tumour necrosis factor-alpha (TNF-α), interleukin-6, and interferon-gamma, can damage tissues and cause inflammation in the eyes that is related to the immune system. ⁽⁶⁾

Septic Microangiopathy

In severe cases, when the body has a serious infection in the blood, it can cause widespread clotting in small blood vessels.

This can block blood flow to the retina and the optic nerve, leading to conditions that damage vision like retinal disease and optic nerve damage.

Clinical Ocular Manifestations

Anterior Segment Manifestations

Conjunctival Congestion

Conjunctival injection is among the most frequently reported ocular findings in scrub typhus and reflects systemic vascular inflammation. ⁽⁷⁾

Subconjunctival Haemorrhage

Thrombocytopenia and capillary fragility may predispose patients to subconjunctival haemorrhage, particularly in severe septic cases.

Keratitis and Uveitis

Cases of superficial punctate keratitis and anterior uveitis have been reported secondary to immune-mediated inflammation. ⁽⁸⁾

Posterior Segment Manifestations ⁽⁹⁾

Retinitis

Retinitis is characterised by multifocal white retinal lesions associated with retinal oedema and haemorrhage. Patients commonly present with blurred vision, floaters, and scotomas.  ⁽¹⁰⁾

Retinal Vasculitis

Inflammatory retinal vascular sheathing and vascular occlusion may occur because of endothelial damage and perivasculitis.

Retinal Haemorrhage and Macular Oedema

Increased vascular permeability and coagulation abnormalities contribute to retinal haemorrhages and cystoid macular oedema. ⁽¹¹⁾

Optic Disc Oedema and Optic Neuritis

Optic nerve involvement may manifest as papillitis, optic neuritis, or ischemic optic neuropathy. Patients may experience decreased visual acuity, impaired colour vision, and visual field defects. ⁽¹²⁾

Neuro-Ophthalmic Manifestations

Neurological involvement in scrub typhus may lead to neuro-ophthalmic complications such as:

• Sixth cranial nerve palsy
• Oculomotor nerve palsy
• Papilledema
• Internuclear ophthalmoplegia

These findings are often associated with meningoencephalitis and severe systemic disease. ⁽¹³⁾

Diagnostic Evaluation

Early ophthalmic evaluation is essential in patients with severe scrub typhus.

Clinical Examination

Comprehensive ocular examination should include:

• Visual acuity assessment
• Slit-lamp examination
• Pupillary reflex assessment
• Dilated fundus examination
• Intraocular pressure measurement

Fundus Fluorescein Angiography

Fundus fluorescein angiography may reveal retinal vascular leakage, capillary non-perfusion, and vasculitic changes. ⁽¹⁴⁾

Optical Coherence Tomography

Optical Coherence Tomography assists in identifying macular oedema, retinal thickening, and subretinal fluid accumulation.

Laboratory Diagnosis

Definitive diagnosis of scrub typhus relies on:

• IgM enzyme-linked immunosorbent assay (ELISA)
• Indirect immunofluorescence assay
• Polymerase chain reaction (PCR)

Associated laboratory abnormalities may include thrombocytopenia, elevated liver enzymes, leukocytosis, and elevated inflammatory markers. ⁽¹⁵⁾

Management

Antimicrobial Therapy

Doxycycline remains the first-line treatment for scrub typhus. Early initiation of therapy significantly reduces systemic and ocular complications. ⁽¹⁶⁾

Alternative agents include:

• Azithromycin
• Rifampicin
• Chloramphenicol

Corticosteroid Therapy

Adjunctive corticosteroids may be considered in severe inflammatory ocular complications such as optic neuritis and retinal vasculitis after adequate antimicrobial coverage.

Supportive Care

Management of scrub typhus-induced septicaemia includes:

• Haemodynamic stabilisation
• Organ support
• Mechanical ventilation
• Correction of coagulopathy

Ophthalmic Follow-Up

Serial retinal examinations and imaging studies are recommended to monitor progression and response to treatment.

Prognosis

Visual prognosis is generally favourable with early diagnosis and prompt treatment. However, delayed therapy may result in irreversible retinal ischemia, optic atrophy, and permanent visual impairment. ⁽¹⁷⁾

Poor prognostic factors include:

• Severe septicaemia: When the infection becomes widespread, inflammatory mediators are released throughout the body, leading to reduced blood pressure and tissue perfusion, abnormal blood clotting with microvascular thrombosis, and decreased oxygen delivery to the retina and optic nerve. The infection may also spread to the eye through the bloodstream, resulting in more severe ocular involvement and potentially worsening visual prognosis.

As a result, severe septicaemia increases the likelihood of extensive ocular involvement and irreversible retinal injury.

• Multi-organ dysfunction syndrome
• Central nervous system (CNS) involvement: CNS involvement is an important poor prognostic sign because it suggests more extensive dissemination of the infection and indicates severe systemic disease. It may also involve the optic nerve or visual pathways, raise the risk of neurological complications. Visual loss may occur if the optic nerve or its blood supply is affected, addition with retinal pathology. Therefore, CNS involvement indicates a more widespread and severe infection and is generally associated with a poorer visual prognosis.
• Extensive retinal vasculitis
• Delayed antimicrobial therapy

Conclusion

Scrub typhus-induced septicaemia is associated with diverse ocular manifestations involving the anterior segment, retina, optic nerve, and neuro-ophthalmic pathways. The underlying pathogenesis is multifactorial, involving endothelial injury, vasculitis, inflammatory cytokine release, and septic microangiopathy. Early ophthalmic evaluation and timely antimicrobial therapy are critical to preventing vision-threatening complications. Increased awareness among clinicians is necessary to facilitate early diagnosis and multidisciplinary management.

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About the Author

 

Saptarshi completed his Bachelor of Optometry from the WBUT, West Bengal, and subsequently pursued a Fellowship at Dr. Shroff’s Charity Eye Hospital (SCEH), New Delhi, where he was awarded the Best Fellow distinction. He holds a Master of Optometry from VMU, Tamil Nadu, and has specialised training in Glaucoma.

He has authored several research publications and holds NIDA certification for clinical trials. His clinical and research interests include Diagnostic, Behavioural, Glaucoma and Neuro-Optometry. He currently serves as a Senior Optometrist at Centre for Sight, New Delhi, and is voluntarily involved as an educator and trainer in the field of Optometry. He also serves as Director of Advanced Studies (India) at Vision Science Academy, contributing to the advancement of education and research in vision sciences.