Persistent human leptospirosis - guide for the public

Persistent infection is a situation where the patient has recovered from an acute illness, but shows some long-term health effects caused by the bacteria remaining in isolated areas of the body, long after the immune system has removed them from the bloodstream and general tissues. It is different from a carrier state as the patient is not infectious to others, but persistent human leptospirosis (PHL) is far more common than previously thought.

These long-term issues are not only a factor of leptospirosis - other infections from bacteria in the same order, such as Lyme disease, often show health problems for several years after recovery.

Symptoms of PHL

Symptoms vary a great deal between patients, with some being almost incapacitated and others noticing nothing. The reported symptoms are listed below, with the most common first:-

Depression, from mild personality changes to quite severe clinical disorders and suicides.
Fatigue, often quite pronounced and debilitating
Headaches, resembling migraines but not always particularly severe.
Eye pain, with or without any inflammation, sometimes with vision disturbances.
Psychological changes, including mood swings, short tempers, rarely OCD.
PIEM, parainfectious encephalomyelitis, is seen in quite a few cases. This is damage to the nervous system and manifests in different ways, so patients can show symptoms of meningitis, epilepsy, balance problems, muscle weakness and vision disturbance. It can mimic the symptoms of multiple sclerosis.

Causes of PHL

There are two reasons for ill health following a bacterial infection:-

Tissue damage

During the acute illness, bacteria cause damage to tissues in the patient's body, by a combination of toxins and damage to the blood supply. This can lead to long-term changes in the function of internal organs but is not directly related to the bacteria, only to the damage they cause. Reduction in function of the liver and kidneys is one such outcome, but where the tissue damage is not too severe the body will heal over time.

Bacterial residency

In the body there are certain places, called immunologically privileged sites (IPSs) where the immune system is not very active, and bacteria can survive long after they have been killed in the rest of the body. These sites are usually places without a direct blood supply, such as the fluids within the eyeball and the structures of the brain and nervous system. In the rest of the body, the patient's immune system reacts to leptospires and creates antibodies that will ensure they are killed within a few days, however in IPSs the supply of these antibodies, and the white blood cells that do the killing, are reduced. Bacteria can 'hide' in these sites but are kept trapped by the active immune system, so the symptoms tend to be concentrated on the same organs. We have very little direct evidence for the time bacteria can survive in this way, but it is certainly several months or years.

While they are present, leptospires in IPSs have two effects - they still leak toxins into the tissues, albeit at a quite low level, and this can cause slight inflammation or reduction in tissue viabililty. More importantly they can continually trigger the immune system at the border of the IPS, and the immune response to this constant prodding of white blood cells can be more severe than is required - in some cases it will cause an autoimmune response where the body's immune system starts to attack 'self'. It's common for patients with PHL to show unexpected severe symptoms when exposed to leptospires a second time, as the autoimmune response is activated. It's particularly true in the eyes and is the cause of recurrent symptoms in horses.

Treatment

There is no working treatment for PHL at this time which has shown itself to be effective on every patient - research conducted in recent years has shown promise in developing an immunological treatment program, however in the majority of cases supportive care is given. Maintaining a healthy diet with full nutritional balance is very important, and symptoms can be treated in isolation (with painkillers, etc.) but in many cases a repeat program of antibiotics has been able to increase the speed of recovery. The difficulty is that medication will only act on the persistent bacteria, and so any long-term tissue damage caused by the infection will need to heal at a natural rate - this can take several years and in severe infections there can be some permanent damage to tissues. Patients suffering poor helth after a leptospirosis infection should always discuss the issue of PHL with their physician, if necessary via a referral to a specialist in infectious and autoimmune disease. The symptoms are expected to reduce over time even without treatment, and so in many patients with only minor reduction in health it can simply be a waiting game.

The Leptospirosis Information Center