Leptospirosis in Children
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Direct answer
Leptospirosis is a zoonotic infection caused by pathogenic Leptospira species, acquired through contact with water or soil contaminated with animal urine, mostly from rats. The illness is typically biphasic, with an initial septicaemic phase followed by an immune phase that may cause aseptic meningitis. Conjunctival suffusion is a characteristic early sign, and intravenous penicillin is the treatment of choice for severe disease.
What you must remember
- Organism: pathogenic Leptospira species, with Leptospira interrogans the most important in clinical practice.
- Transmission: contact with contaminated water, mud or soil, with skin abrasions and mucous membranes as entry points.
- Biphasic illness: a septicaemic phase with fever, headache and myalgia, then a brief remission, then an immune phase.
- Conjunctival suffusion: congested conjunctiva without discharge, a classic early sign that is not purulent conjunctivitis.
- Calf tenderness: marked muscle tenderness in the calves is a useful clinical clue.
- Weil disease: severe icteric leptospirosis with jaundice, acute kidney injury and haemorrhage.
- Diagnosis: blood culture or PCR in the first week, with the microscopic agglutination test as the reference serological test.
- Treatment: penicillin for severe disease, doxycycline for mild cases, and ceftriaxone as an alternative.
Two phases, two different investigations
The same infection looks different in its first week and in its second, so the right test depends on the day of illness. The table separates the phases so the investigation can be timed correctly. Sampling to the right phase avoids most false negatives in this disease.
| Feature | Septicaemic phase | Immune phase |
|---|---|---|
| Timing | First few days, usually within the first week | Starts after a brief remission |
| Main features | Fever, myalgia, conjunctival suffusion | Aseptic meningitis, uveitis, renal involvement |
| Site of organism | Blood and CSF | Urine, with leptospiruria |
| Best test | Blood culture or PCR | Urine culture, MAT and IgM ELISA |
A child with fever, calf tenderness and red eyes after flood-water exposure should prompt a blood sample in the first week. Antibodies rise later, so a patient seen in the second week needs serology even if an early test was negative. Urine culture becomes useful later, because leptospires are shed in urine during the immune phase. Treatment should start on clinical suspicion rather than waiting for confirmation.
Where the exam tries to catch you
Questions on this topic test the sign, the phases and the drug of choice.
- Trap: confusing conjunctival suffusion with purulent conjunctivitis Correct: suffusion is congested conjunctiva without discharge, a clue to leptospirosis.
- Trap: stopping the workup after a negative early serology Correct: antibodies may be absent in the first week, so serology should be repeated in the second week.
- Trap: choosing doxycycline as the only option for severe Weil disease Correct: penicillin is the treatment of choice for severe disease, while doxycycline suits mild cases.
- Trap: attributing the meningitis of the second phase to a separate infection Correct: aseptic meningitis in the immune phase is characteristic of leptospirosis.
Frequently asked questions
What is the characteristic clinical sign of leptospirosis in children?
Conjunctival suffusion is the characteristic clinical sign of leptospirosis in children. It describes congested conjunctiva without discharge, which is seen early in the illness. Calf muscle tenderness and high fever with myalgia add to the picture.
What is Weil disease and why is it serious?
Weil disease is the severe icteric form of leptospirosis, most often caused by Leptospira interrogans serovar icterohaemorrhagiae. It causes jaundice, acute kidney injury and haemorrhage, and it carries a higher fatality than mild leptospirosis. Early penicillin and intensive supportive care are essential in Weil disease.
What is the treatment of choice for severe leptospirosis in children?
Intravenous penicillin is the treatment of choice for severe leptospirosis in children. Doxycycline is used for mild disease in older children, while amoxicillin or azithromycin may be chosen in young children. Ceftriaxone is a recognised option for severe disease in some settings.
What is the biphasic course of leptospirosis?
The biphasic course of leptospirosis begins with a septicaemic phase of fever, headache and myalgia. It is followed by a brief remission, then an immune phase that may cause aseptic meningitis or renal involvement. Recognising the two phases helps in timing the investigations.
Which test confirms leptospirosis, and when should it be sent?
Blood culture or PCR is most useful in the first week of illness, while the microscopic agglutination test is the reference serological test. Serology can be negative early, so a repeat sample is needed in the second week. IgM ELISA is a widely used screening option in practice.