Overview of human leptospirosis

Human leptospirosis can be a difficult infection to describe, as the
symptoms can vary dramatically between patients. Some symptoms are
extremely common, but only a small number of patients will experience
the severe life-threatening illness known as Weil’s disease. The
severity of the infection depends on the age and general health of the
patient, plus the serovar (strain) of bacteria involved and the number
of bacteria that entered the patient’s body.

The infection is usually systemic (affecting the whole body) and causes
a sudden fever. In mild cases it lasts a few days, following a pattern
similar to flu but often in two phases – a period of illness lasting a
few days, then a slight recovery, then a second period of illness. In
mild cases the second phase lasts a short time and the patient recovers,
but in severe types the illness develops and progresses rapidly, leading
to organ failure and often death if not treated with intervention and
support.

Incubation time

From the time you were infected with the bacteria, there is a period
where it has to reproduce enough to cause illness – called the
‘incubation time’. With human leptospirosis this is typically 3 to 21
days, with most patients developing illness after about 3 to 14 days. It
does not usually take more than 28 days, but in rare cases very long
incubation periods have been reported. It generally cannot show illness
in less than 24 hours unless the volume of bacteria taken into the
bloodstream was massively larger than normal.

First stage

Leptospirosis starts suddenly, with a severe headache, redness in the
eyes, muscle pains, fatigue and nausea and a fever of 39°C (102°F) or
above. There is sometimes a red non-blanching pinprick rash on the skin,
similar to that seen in meningitis. Young children can be tired or
distressed and may show an aversion to bright light. The severe headache
is almost always present and can be incapacitating. Nausea may or may
not cause vomiting. Muscle pains can be extreme and are often
particularly bad in the calf and back areas – muscles will be sore to
move and to touch. A rapid pulse is also common in the first few days.

The skin rash develops in the first one or two days and often the skin
is warm and pink just beforehand, with the patient complaining of
feeling warm. Rashes can occur anywhere but in some cases are confined
to local regions of skin such as the front of the legs. Sometimes they
will be itchy, but rashes are only seen in about 30% of all cases so the
lack of any rash is not too significant.

Psychological changes are often seen, with patients feeling depressed,
confused, aggressive and sometimes psychotic – with schizophrenia and
hallucinations, personality changes and violence.

This phase lasts between three and five days, then the patient
(temporarily) recovers. During this phase the bacteria are active in the
patient’s bloodstream (so it is sometimes called the septecaemic phase)
and so can be detected by lab tests.

Second stage

In many mild cases this doesn’t happen at all, but where the infection
is more severe, the patient enters a second phase of illness after a few
days of apprent recovery. The initial symptoms and fever return,
accompanied with chest and abdominal pain, some renal problems and
psychological changes. Increased symptoms of meningitis are often seen
with neck stiffness and vomiting, but in most mild cases the patient
will not suffer kidney or liver failure and will eventually recover.
There may be a sore throat and dry cough, with a litle blood. With
treatment, mild cases will recover within a few weeks.

During this second phase the bacteria are only really active in the
tissues of the patient, and so can be difficult to find in the
bloodstream, making lab tests a problem. This second phase is usually
called the ’tissue’ or ‘immune’ phase.

Severe infections

In cases of particularly virulent serovars or patients with poor health,
the infection follows a different pattern and the patient develops very
rapid and severe symptoms from the start, without much of a remission.
Symptoms are the same as for the mild type but more pronounced, and
multiple organs are damaged – liver and kidney failure can occur within
10 days, leading to jaundice and death if not treated. Hemorrhages are
common (including bleeding from the mouth, eyes and other mucous
membranes), plus infection of the heart and significant internal
bleeding. Dialysis is the most important intervention and the patient
will require antibiotics and hospital admission in order to stand a
chance of survival. Death, when it occurs, is usually due to heart,
liver or respiratory failure. Severe infections are often called
‘icteric’ because of the presence of jaundice, and these are the only
cases that can really be called Weil’s disease.

Recovery

Patients with mild infections recover quite quickly, so are usually
feeling OK after a few weeks, but they can suffer from fatigue and
depression for a while and may be at risk from persistent infection.
Patients with the more severe infections can take several weeks to
recover, as removing the bacteria is not the problem – they will have
caused damage to the body’s tissues that take time to heal. Although
some patients can die, with medical treatment the chances of survival
are good – though patients that have had a severe illness may suffer
long-term symptoms due to organ damage that cannot completely heal.
Psychological changes (mood swings, depression, psychoses) are common
for a few months following recovery.
Immunity

Patients that survive infection will develop some immunity, but only to
the serovar that infected them and some closely-related ones. They can
still be infected by other strains, and the immunity lasts no more than
ten years in humans. There is a very small possibility of auto-immune
reactions to the bacteria if patients are reinfected again, but the main
concern of patients is that they can suffer from medium-term symptoms
due to persistent infection which are almost impossible to treat.

Causes of infection – guide for the public

Human infection is always caused by exposure to the bacteria that have
been shed by an infected animal, and in 90% of cases it will be their
urine (although infection direct from blood is also possible). Direct
transfer, where the urine comes into contact with the patient and enters
their bloodstream, is very rare except in accidental exposure when
handling infected animals, and the usual route is via water that is
subsequently drink, or used for recreation such as swimming.

The bacteria have to physcially enter your bloodstream in order to cause
an infection, and as they cannot easily penetrate dry undamaged skin,
they can only enter at certain locations – injuries where the skin is
broken are the obvious places, but mucous membranes lining the airway,
mouth, lungs and female sexual organs are also potential routes – so
breathing in or swallowing bacteria is a risk, and leptospirosis can
sometimes be spread via sexual intercourse.

Dry unbroken skin is a perfect barrier against the bacteria, but cuts
and scrapes need only be tiny for the bacteria to find an entry point.
There is also a suggestion that the bacteria can pass through very
waterlogged skin (such as when skin is immersed in water for a long
time), as the cellular structure of the skin changes slightly. This is
still only a theory and we have no cases on file.

The bacteria are not generally airborne, so the only risks for breathing
in the infection are where water droplets are being created – such as
pressure-washing work or in the spray chambers of some air conditioning
plant. Being “generally close” to an infected person or animal will not
cause an infection!

It’s important to realize that the bacteria are incredibly small, and so
even a pinhead sized drop of water can carry millions of them. In theory
it only takes one to cause illness, but in reality your body’s immune
system will attack them to a certain extent and so the chances of
illness increase as the volume that enters the body (the ‘innoculum’)
increases.
What are the chances of catching this infection from my local
river/pond/cess pit?

Obviously this depends on two things – if the water is infected with the
bacteria, and if you and said bacteria get in close enough contact!

On average in the developed world (Europe, mainland USA, etc.) about 20%
of feral rats carry strains of leptospira that could cause illness in
humans. This of course varies locally – in your area you may have 100%
rat carriers, or 0% – it just depends on the social lives of the rats in
question. It’s therefore sensible to assume that on average 10% of all
freshwater sites are infectious, with more probability for sites which
stand good chances of hosting rats nearby (urban ponds, slow-moving
rivers and canals, lakes near farm buildings, etc.) and less of a risk
for non-rodent-friendly sites such as rapid flowing highland streams or
very large estuaries and river deltas. Obviously any site with a high
water throughput (such as a river) is less of a risk than stagnant
water, as rodent urine will be diluted by the flow. Any water treated
with chlorine or UV-sterilisation will be totally safe. This means that
swimming pools, and many municipal water fountains and architectural
features, are usually of no risk in terms of leptospirosis.

The chances that being exposed to contaminated water would lead to
infection depends on what you do in the water. To become infected you
must actually allow water to enter your body, though that could be as
simple as through an open cut, or by licking a finger. Swimming is the
highest risk activity as there is no way to prevent some ingestion and
skin contact, though other activities such as fishing, waterskiing,
sailing and kayaking can also present risk. Remember that the bacteria
cannot survive in saltwater so there is no possible risk from swimming
in the sea, or in tidal regions of rivers where the water is briny.

In general in the developed world people are wary of open water sites
from general cleanliness viewpoints, and would not drink from a lake
without a very good reason. The chances of infection are therefore quite
low, but these statistics hide the fact that in many cases the infection
is mild, and goes unreported. Despite only a few thousand cases being
reported in the developed world each year, there will be many times more
cases which are simply written off as a cold or stomach bug – we
estimate the total number of cases in the developed world could be up to
100,000 per year.

In developing countries the risks are greater, as rat populations are
more widespread and water use is different. The quantity of untreated
water used for washing, bathing and drinking is far higher, and the
association between hygiene risks and open water is rarely made.
Education in developing countries is the only solution to this issue, as
the bacteria and the rats are there to stay.

Treatment of human leptospirosis – guide for the public

Treatment for acute illness in humans is in two parts – an antibiotic to
control the bacteria and general support of the patient’s internal
organs so they maintain their ability to recover while the bacteria are
removed.

Antibiotics

Leptospirosis can be treated by a wide range of antibiotics, and medical
staff will select the best based on availability, the patient’s age and
any other medications they may be taking. In mild cases the medication
will be given by mouth adn the patient can stay at home, but in severe
infections the antibiotics are often given directly into the bloodstream
via a drip (IV) and so require them to remain in hospital. This is also
important to allow them to be monitored as the infection progresses.

In many cases, penicillin is used – but if the patient is allergic then
a number of alternatives are available as well. It is very important to
take antibiotics as prescribed – do not miss any doses and take all the
doses even if you feel that you’ve recovered. Stopping a course of
antibiotics before the end can lead to resistant bacteria taking hold
and causing very severe illness. The dose of antibiotic will be
calculated based on the patient’s age and body mass, and medical staff
do not need to know the exact strain of leptospira involved before
beginning treatment – indeed it should be started before test results
are returned if the patient has a high probability of being infected.

Other medications

Often patients will have severe headaches, fever and nausea in the first
week or two, and these can be controlled by normal non-prescription
medicines. In some cases medical staff may prescribe additional programs
of medication to help with liver or kidney function, or to support
deficiencies in diet.
Hospital care

In severe infections the patient will be admitted to hospital, and may
need to be intensively supported for a few weeks. Patients can require
dialysis, fluids and painkillers plus help with their breathing. In very
rare cases patients can become psychologically disturbed and may need
sedation for their own safety. The infection is not particularly
contagious and so patients are not usually isolated and can receive
visitors as their condition permits.
General recovery

Recovery can take a while, and a lot of patients find they suffer from
fatigue and depression for a few months after recovery, requiring
support. Maintaining a healthy diet with all the proper vitamins and
minerals is very important during recovery, and patients that feel
fatigued should rest as much as they need to – fighting it off and
continuing to work can make recovery a lot slower.