What is histoplasmosis?
Histoplasmosis is a human infection that occurs with the inhalation of fungi of the type Histoplasma capsulatum .
Locations with large concentrations of birds and bats are favorable to the disease, as fungi are present in the feces of these animals and are mainly deposited in the soil, caves, hollow tree trunks, chicken coops and house linings.
If there are favorable conditions, such as temperature, humidity and the presence of nitrogen, fungi can survive up to 4 months on the soil and surfaces.
The infection is classified as a zoophilic mycosis , as it is triggered by fungi found in animals.
When the person breathes close to the infected environments, the microorganism is inhaled and infects the human body. But despite being acquired through the respiratory tract, the disease is not transmissible between humans.
When inhaled, the fungus reaches the pulmonary alveolus and reaches the bloodstream, being disseminated through the circulation, which allows the infection to reach several organs, such as the liver, spleen and bone marrow.
However, it is the immune response – and its ability to fight infection – that will determine the onset of symptoms and how severe the disease will be.
In most cases, the infection is mild or subclinical. This means that the condition has no symptoms and tends to improve without the need for drug treatment, being classified as asymptomatic.
The degree or manifestation of symptoms depends on how long the person has been exposed to the infected environment, as well as compromises of the immune system.
That is, in general, inhaled fungi are effectively fought by the healthy immune system or result in milder symptoms, constituting an acute lung infection .
If the exposure is prolonged or the person has low immunity, the disease can manifest itself as a chronic lung infection . In addition, if the infection reaches other organs, it is called a disseminated infection .
But if the disease manifests itself in a chronic or widespread way, there is involvement of other organs, weight loss, chronic coughs, breathing difficulties and, if left untreated, can lead to death.
Most cases do not require treatment, as the healthy organism is able to attack and destroy the infectious agent.
Histoplasmosis is listed in ICD10 under the code B39, with subclassifications of:
- B39.0 Acute pulmonary histoplasmose due to Histoplasma capsulatum ;
- B39.1 Chronic pulmonary histoplasmosis due to Histoplasma capsulatum ;
- B39.2 Pulmonary histoplasmosis, not specified by Histoplasma capsulatum ;
- B39.3 Histoplasmosis disseminated by Histoplasma capsulatum ;
- B39.4 Histoplasmosis, unspecified by Histoplasma capsulatum ;
- B39.9 Histoplasmosis, unspecified .
The AIDS today is an aggravating factor for the infected patient, due to the high commitment of the body.
According to a review study published by Revista da Sociedade Brasileira de Medicina Tropical, until the 1980s, before the knowledge about acquired immunodeficiency syndrome was deepened, cases of histoplasmosis were hardly identified.
At the time, diagnoses occurred only in patients with lymphoma, other neoplasms and in some kidney transplant recipients, due to the weakened immune system.
In the 1980s and 1990s, hundreds of cases were identified in AIDS patients, especially those of the disseminated type, causing the infection to gain great clinical relevance.
Infections occur when external agents invade the body and cause reactions. They can be caused by several microorganisms, such as bacteria, viruses, parasites and fungi.
The symptoms most associated with infections involve fever, pain, pus formation, coughing, weakness, gastrointestinal dysfunction and fatigue .
To treat an infection, it is necessary to identify the cause, as the methods and medications vary according to the infectious agent.
What are fungi?
Fungi are microorganisms that can have a single cell, called yeasts, or cell groups, such as mushrooms.
So we already know that not all fungi cause disease or infection. In fact, some of them are naturally found in the human body, such as in the intestine, mouth, skin and vagina.
However, there are also those microorganisms that pose health risks.
There are pathogenic fungi, which infect the organism regardless of the person’s immunological conditions, and others called opportunists, which trigger reactions only in fragile organisms.
The importance of fungi
Despite being generally associated with diseases and infections, fungi play an important role in the environment and are present even in human food.
Fungi play a decomposing action, assisting in the processing of organic materials, such as wood, clothing and food. In addition, fungi can be edible and compose various recipes.
Generally, the food product most associated with fungi is the mushroom, a food that is greatly appreciated by the world.
But there are other products much more frequent in the diet that involve the action of microorganisms, such as breads and some alcoholic beverages. Especially homemade breads use yeast, which are popularly called biological yeasts.
Organic or fresh yeasts Saccharomyces cerevisiae stimulate fermentation and dough growth. Fungi consume the sugar present and release carbon dioxide and alcohol.
The result of this interaction is fluffy bread. This is because the carbon dioxide released in the process and causes micro bubbles to form in the dough.
Those little minutes in which you leave your dough resting are necessary for these microbubbles to form, make the dough rise and, after baking, soften the bread.
In alcoholic beverages like beer and wine, fungi ferment the main ingredient of each drink. In wine, it is grapes and in beer it is barley that undergoes fermentation.
In addition, fungi are used in the manufacture of drugs capable of fighting bacteria, for example, penicillin.
Diseases caused by fungi
But you probably still associate fungi with disease, so we must not forget that, despite participating in some tasty dishes, fungi can be very harmful to the body. Among the most common diseases are:
- Onychomycosis (nail infection);
- Fungal sinusitis;
- Fungal meningitis;
When the person inhales the air, several suspended substances are inhaled, whether they are perceived or not.
Bacteria, fungi and plants produce dozens of tiny particles and release them into the environment. These particles, called spores, can be compared to seeds, as they serve to generate new microorganisms.
It is estimated that a person inhales between 200 and 2,000 spores a day.
Although it sounds alarming, fungi that are suspended in the air usually only pose health risks if the organism is weakened, according to data from a survey conducted by the Faculty of Medicine of the Federal University of Rio de Janeiro.
Even if the complications caused by fungal infections often have high degrees of complication and can even cause death, this occurs most of the time if the person has an immune deficiency.
So there needs to be a high and intense exposure of the person to the fungus. Generally, histoplasmosis is prevalent in locations with bird and bat droppings, which means that chicken coops and caves can be places of greatest infestation.
Rural workers, ecotourists and chicken farmers are more prone to the disease because they spend more time in direct contact with risky environments.
When inhaling contaminated air, the spores enter the airways and go through an incubation period of 1 to 3 weeks.
This period refers to the entry of the infectious microorganism into the host (in this case, the human body) until the onset of symptoms or clinical manifestations.
That is, after inhaling the fungus, the symptoms can take up to 3 weeks to manifest.
Briefly, the infective agent enters the respiratory tract and is transported to the alveoli. A phagocytosis occurs, that is, the microorganisms are isolated by a process of cellular encapsulation to later be digested or eliminated by the macographs of the alveolar cells.
In approximately 3 weeks there is an increase in the immune response in the healthy organism that prevents the spread of contaminated macographs.
However, in patients with low immunity, it is possible for the fungus to spread to other organs through blood or lymphatic pathways, especially when there is a diagnosis of AIDS or chemotherapy treatments.
The infection is generally divided into 3 categories, which are acute, chronic and disseminated. Approximately 80% of diagnosed cases refer to an acute infectious condition, which may or may not present symptoms.
In general, the condition of patients evolves asymptomatically or with mild symptoms, with no need for drug treatments.
Acute lung infection
Cases of acute infection can present symptomatic manifestations of varying degrees, including the absence of any symptoms.
Generally, when there are signs of this type of infection, they are mild and resemble flu and pneumonia, with frequent coughing, fever and headaches.
Through radiological examinations, it is possible to identify masses infiltrated into the lungs, which may present on only one side or on both.
In some cases, patients with high sensitivity may develop knotty erythema (skin lesions), conjunctivitis and pleurisy (inflammation of the lung membranes).
Between 1 and 3 months the signs and injuries tend to improve, but calcifications usually remain in the lungs and outside them.
Chronic lung infection
Initially, the main manifestations involve coughing, mucus sputum, chest pain, fever, weight loss and lack of appetite.
The acute type of the disease occurs more frequently in people over 40 years old, prevailing in males. In general, other factors that favor infection are identified, such as the presence of chronic obstructive pulmonary disease, tumors and lymphomas.
These diseases usually cause abnormal air spaces in the lungs. Allowing the infection to settle more easily, aggravating the initial condition.
The condition tends to affect the upper part (upper lobes) of the lung. X-ray and chest tomography exams indicate the presence of infiltrations, occurring more frequently in the right lung, due to the anatomical ease.
The infectious type is fatal in 80% of untreated cases.
Whether symptoms are present or not, yeast infection can spread throughout the body, especially to organs such as the liver, spleen, lymph nodes, bone marrow, in addition to the adrenal glands.
Disseminated infection occurs mainly in immunocompromised patients, especially in cases of HIV positive. Manifestation is considered the most serious form, as fungi proliferate intensively inside and outside the lungs.
When it affects other systems of the body, the infection can mainly affect the liver, spleen, intestines, mucous membranes, skin, oropharynx and adrenal glands.
In this case, there is an increase in the size of some affected organs, skin lesions, in addition to the primary manifestations of the infection (fever, headaches, weight loss and malaise).
Histoplasmosis is caused by inhaling the fungus Histoplasma capsulatum . The time of exposure to fungi and the conditions of the immune system are decisive for the evolution of the disease.
Therefore, people who spend a long time in caves, chicken coops, caves or regions infested with bat and bird droppings are more likely to inhale the fungus.
No. Although the disease is acquired through the respiratory tract, through inhalation of the fungus, it is not transmissible through saliva, contact or airways (when the sick patient sneezes, for example).
In addition to not being transmissible through the airways, the disease cannot be acquired through direct contact with animals.
The infection is, in most cases, fought by the immune system, without causing complications or even showing symptoms.
However, two conditions can determine the degree of involvement of the organism: exposure to the fungus (inhalation time and quantity) and the patient’s immune status.
As for exposure to Histoplasma capsulatum , people who develop activities such as construction, demolition, ecological tourism, camping and activities related to agriculture and poultry need informational measures on the risks of contracting the disease.
In addition, even if the inhalation period is short, if the concentration of fungi in the inhaled air is high, the infection can develop more aggressively.
Therefore, spending a few minutes inside a cave can result in contamination. In addition, other factors that aggravate contamination are:
- Breathe very close to the stool;
- Inhaling high amounts of fungi: the exposure may be short, but the concentration of fungi is high or the time that the person breathed the contaminated air was large;
- Have skin lesions and come into contact with contaminated feces or surfaces.
With regard to immunological conditions, patients who have undergone organ transplants, undergo chemotherapy or corticosteroid treatments are more sensitive to chronic or disseminated infection.
Conditions such as HIV positive, old age, children under 2 years old, severe immunity deficiencies and leukemia are risk factors and can favor the progression of the infection.
Patients with lung disorders, such as pulmonary emphysema , who use corticosteroids, TNF inhibitors (to treat rheumatoid arthritis) or medications to prevent transplant rejection are more likely to have the chronic type of infection.
When symptoms are present, the infection can be confused with flu and pneumonia due to the presence of symptoms such as headache , cough, respiratory changes, pallor and fatigue, which can manifest up to 17 days after exposure to the fungus and remain for approximately 10 days.
In the acute phase, signs such as:
- Persistent cough;
- Accentuated pallor;
- Increased superficial lymph nodes;
- Mental confusion;
- Enlarged spleen and liver.
When the infection spreads, hypotension , shock and severe respiratory problems can occur , with high risks to life.
Ulcers in the esophagus, stomach, small intestine and colon manifest in a small percentage of those diagnosed. Uncommon, but still reported, are lesions in the spleen and liver that, in most cases, result in the patient’s death.
One of the consequences of the infection is damage to vision. Called ocular histoplasmosis, the condition is quite rare and is characterized by the formation of spots inside the eyes.
They occur because there is an improper formation of blood vessels near the retina, causing neovascularization, that is, the formation of new blood vessels.
Initially, the appearance of these vessels may not impair vision. But the trend is that after the infection is fought, about 1 year later, this proliferation of the vessels impairs vision.
Eye changes can be noticed only years later, with visual distortions, such as blurs, lines and undulations in the field of view.
As new vessels are fragile, they can rupture and cause eye bleeds. In this case, the risks of loss of vision are greater and it is essential that patients with a history of ocular histoplasmosis maintain eye care.
When they occur, the surface of the skin presents wounds and changes, which may involve pus, redness, blisters or ulcerations at the edge of the wound.
Cutaneous manifestations are uncommon, occurring in approximately 10% of patients. Most are HIV positive or there are signs and symptoms that the fungus has secondary infection in the body.
That is, the contamination was directly through the skin, usually through existing wounds.
Some studied cases indicate that the patient already had an injury, crack or bruise, which favored the infection through the skin as well.
In order to make the diagnosis, it is necessary to identify the presence of the infectious agent through clinical analyzes.
The clinical diagnosis is made with the analysis of blood, sputum or tissue samples by biopsies.
However, identifying histoplasmosis is not always simple, as the tests can present false negatives due to the recurrent confusion of the fungus with other agents.
This means that the appearance and behavior of the fungus in the body are quite similar with other agents, such as tuberculosis. This can result in several late or mistaken diagnoses.
When suspecting the disease, the doctor may order histological, mycological, immunological and radiological exams. For this, it is possible to collect blood, urine, secretions or even perform biopsies of skin lesions (if any) or liver, for example.
Immunological tests are, in general, more efficient to determine the presence of the infection when compared to the detection of antibodies (reagent test).
When infected, the fungus spreads through body fluids, such as blood, urine and sputum, which are tissues analyzed by the method.
The test known as ELISA (Enzyme Linked Immunono Sorbent Assay), stimulates the enzymatic action of the tissue. That is, specific substances are applied for each investigated disease.
From the presentation or behavior of antibodies in the tissue, it is possible to diagnose infections.
The test shows good results even for patients with HIV who have the widespread form of histoplasmosis, but do not produce antibodies.
That is, when performing tests, the organism is not able to react properly to the test, giving a false negative.
In patients with disseminated histoplasmosis, the test can still be used to monitor the treatment and check the body’s responses.
Detecting the presence of the fungus through organic secretions is not always efficient for diagnosis.
This is because the fungus is only identified and isolated based on visual observation (there is no substance capable of identifying it). The problem is that the structure of the fungi has very small dimensions, which makes diagnosis difficult only by the mycological method.
Usually, blood and urine samples are investigated, but when the biopsy is performed, the tissues are also referred for investigation.
However, review studies indicate that approximately 60% of patients with chronic infection are diagnosed by this method. Among patients with acute infection, the rate drops to 15%.
Another factor that makes diagnosis by the culture method difficult, is due to the late or insufficient growth of the fungus. That is, it can take up to 12 weeks for the infection to spread enough to be identified in the test.
For this type of test, urine, sputum and blood samples (which consist of less invasive tests) or biopsies (which are more invasive) can be collected.
Samples of organs such as lung, lymph nodes, liver, spleen and bone marrow are collected to check for the presence of agents (granulomas).
That is, in this method, invasive tissue collections are used.
As the structure of the fungus Histoplasma capsulatum is very similar to other agents, the interpretation of the results can be difficult.
However, the test allows to identify massive formations or granulomas in patients with compromised immunity.
To confirm or rule out the diagnosis, differential diagnosis tests are usually carried out (in short, reactive substances are tested to differentiate the fungus from other diseases)
The method has been less used for the diagnosis of some diseases, including histoplasmosis, due to the incorrect interpretation of the results. It is possible that the appearance of protrusions is caused by a hypersensitivity to the tested product.
In addition, the test may give an inaccurate result, because during the incubation period, the organism may not react to the antigen.
Although radiographic examinations are not specifically developed to diagnose histoplasmosis, they allow the presence of nodules, masses or undue formations in the lungs.
The imaging tests indicated may be computed tomography and magnetic resonance imaging.
In acute pulmonary infection, these formations can be isolated or diffuse, that is, the exams can point out mass formations in the organ. They can still be unique (isolated) or spread across the lung.
The images are most significant for the chronic type of the disease. As soon as there is greater involvement of the lungs, it is very similar to tuberculosis.
The results indicate whether there are infections (infiltrations) in the upper parts of the lung, normally the foreign masses are hardened (signs of fibrosis) and aggravate respiratory problems.
Symptoms and results can be confused with other diseases, such as:
- Tuberculosis (attacks the lungs);
- Aspergillosis (disease that affects the lungs);
- Epitheliomas (tumors of the internal or external tissues);
- Cutaneous leishmaniasis;
- Leukoplakia (white patches on mucous membranes, such as gums and vagina);
- Lichen planus (immune deficiency that attacks the skin).
To rule out the aforementioned diseases, the doctor may request that various tissues and body substances be analyzed, such as urine, blood and liver tissues, for example.
Through collections of urine, blood or secretions (such as phlegm), the laboratory can isolate the fungus from fluids or tissues.
In addition, more invasive tests, such as organ biopsies, may be ordered.
A blood sample is collected. The procedure used is the traditional one, with a puncture (collection) being made through a vein usually in the arm, as it is the most accessible.
But other locations can be used to perform the collection.
The procedure does not present great risks, besides pain or bruises in the place.
It usually does not require fasting.
Some laboratories may request that the test be done with the first urine of the day, but not everyone adopts the measure.
The test is non-invasive, requiring a small sample of the liquid to be taken for analysis.
The examination requires a tissue sample to be collected or taken. Several organs can be indicated by the doctor, such as liver, spleen, intestine, skin or, specifically, any lesion of skin or mucosa.
Intradermal reaction for histoplasmosis
Despite being a method used to compose the diagnosis, the intradermal reaction should not be used in isolation.
This is due to the high possibility of false negative, since the test is not able to verify the presence of the fungus in the incubation phase, that is, in the initial stages of infection.
To perform the test, a dosage of the Histoplasma capsulatum antigen , about 0.1mL , is administered .
Antigens are substances that are external to the body and cause the immune system to react.
To carry out some tests and develop vaccines, the researchers weaken or inactivate the agents that cause the disease.
Contrary to what many people think, vaccines do not cause disease, but they can cause reactions in the body. That is why some people feel the flu after taking the flu vaccine, the symptoms are similar, but it is just the immune response creating resistance to the disease.
Upon entering the body, the antigen promotes the action of the immune system, attacking that foreign body. As the method is intradermal (between the skin), there is the formation of millimeter protrusions in the skin layer.
When there are bumps or changes in the predefined layer for analysis, it means that the patient is infected or has had the disease before.
If the result is non-reactor, that is, negative, it means that the organism has never had contact with the Histoplasma capsulatum antigen . Which indicates that he does not have the disease or does not have enough defense cells to fight the external agent.
Generally, laboratories assume that reactions up to 10mm in diameter are considered non-reactive.
If the result is reactive, that is, positive, it means that the organism recognizes the agent and, therefore, the patient has or has had the disease.
-Yeah . In general, the organism itself will attack and eliminate the fungus that causes the infection, leading to a cure without the need for medication.
For patients without serious diseases of the immune system, the complete disappearance of symptoms (clinical cure) occurs within 6 months after starting treatment or making the diagnosis.
In patients with immunological deficiency, with widespread or chronic infection, it is necessary to ensure that treatment is started early, as the condition may progress to death.
Most cases do not need treatment, as the infection is fought by the immune system.
Asymptomatic patients or those with a mild manifestation of acute infection may only need rest, if indicated by the doctor.
When symptoms appear more aggressively, with breathing difficulties or progression of the infection, drug intervention is necessary.
For patients with chronic infection, treatment can be extended for up to 24 months and there is a recurrence of up to 15% of cases after completing the medication.
Studies indicate the effectiveness of the administration of itraconazole in patients with severely weakened immune systems, such as in the presence of AIDS, being more indicated than ketoconazole.
Use must be maintained over the long term. For 12 months the initial dosage must be maintained and then the dose reduction starts indefinitely, until the doctor verifies the possibility of discontinuing the use.
Treatment consists of using oral or, in more severe cases, injectable medications. The doctor may prescribe antifungals and pain medications.
The remedies usually prescribed are:
- Ketoconazole ;
- Amphotericin B ;
- Itraconazole ;
In patients diagnosed with acute infection, drug treatment is recommended when symptoms do not subside after 3 weeks or there is a high impairment of lung functions or other body systems.
Medications can also be administered to reduce swollen lymph nodes or joint pain and pain (head and muscle).
If there are rheumatological manifestations, anti-inflammatory drugs associated with prednisone may be prescribed to relieve symptoms.
NEVER self-medicate or stop using a medication without first consulting a doctor. Only he will be able to tell which medication, dosage and duration of treatment is the most suitable for his specific case. The information contained in this website is only intended to inform, not in any way intended to replace the guidance of a specialist or serve as a recommendation for any type of treatment. Always follow the instructions on the package insert and, if symptoms persist, seek medical or pharmaceutical advice.
The prognosis is quite favorable in most cases. In general, there is no need to use medications or symptoms.
However, in chronic patients, histoplasmosis can result in severe complications, leading up to 50% of patients to death if the correct treatment is not performed.
Even if the patient starts treatment, due to severe pulmonary impairment, about 28% of patients undergoing medical care lose their lives due to the disease.
In general, immune conditions and treatment (when necessary) determine the prognosis.
In patients with severe immunity problems, the evolution of histoplasmosis is rapid and aggressive, resulting in death in 80% of cases.
Histoplasmosis can cause complications when left untreated, especially for groups at risk.
Respiratory distress syndrome
There may be severe pulmonary impairment, causing the organ to accumulate fluids and hinder the exchange of air. The damage to the lung results in the reduction of oxygen levels in the blood, causing insufficient oxygenation to the body.
The heart can be compromised, causing difficulty in pumping blood properly.
The infection can affect the adrenal glands, which are responsible for the production of different hormones. With the change in the hormonal quantity, the organ and tissue functions of the organism can be compromised;
The meningitis is a serious condition which occurs when the membranes of the brain and spinal cord are infected.
It is important to check the locations that promote the proliferation of fungi, such as caves and chicken coops, avoiding direct and prolonged exposure to these environments.
For workers who need to be exposed to the environment, such as bird breeders, explorers or masons, it is recommended to spray the surfaces with water, to prevent the particles from spreading in the air.
It is also necessary to wear protective masks and protect wounds or injuries.
In 2015, the Rio de Janeiro Department of Health answered at least 200 calls due to bat infestation.
At the time, it was found that about 43 species of the animal were circulating in the regions of Rio de Janeiro and 3 of them were fed on blood, and could transmit various diseases.
Although most bats eat fruits and insects, in Rio de Janeiro alone, more than 20 people are bitten each year.
In addition to the direct attack, the transmission of diseases, including histoplasmosis, becomes a worrying factor. Because there is a higher concentration of animal feces, favoring the pulmonary infection to occur.
Can I be infected again?
When inhaling the fungus, the body creates antibodies, becoming resistant to new infections. However, it is possible for symptoms to return after stopping medication.
That is, as long as the fungus is not completely treated and eliminated, the manifestations can occur again, but it does not mean that there was a new infection.
Can pigeons transmit histoplasmosis?
According to the Center for Disease Control and Prevention (CDC), pigeons are not infected with the fungus. But they can carry H. capsulatum on the wings, beaks or legs, spreading the agent around the environment.
In addition, places with concentrations of pigeon droppings can be conducive to the growth of the fungus on surfaces and soils. Thus, when loaded on the animals’ bodies, the fungi can be transmitted to the surfaces and soil, being accommodated in the feces.
What are the endemic regions of histoplasmosis?
Despite occurring all over the world, some regions have higher occurrences of the infection, mainly in North America, Central America and South America.
In Brazil, Fortaleza (CE), Rio Grande do Sul (RS), Rio de Janeiro (RJ), Uberaba (MG) and Uberlândia (MG) were regions that showed major manifestations of the disease until 2010.
Histoplasmosis in animals
Histoplasmosis can also affect animals such as horses, oxen, cats, dogs and pigs. In cats, the disease usually manifests itself in those who are less than 4 years old.
In other animals, no prevalence of age or sex is identified.
The treatments and symptoms are very similar to those in humans. But the risks to the animal’s life are less.
Fungi are present in the body, suspended in the air or deposited on surfaces.
Although, at first, fungi are associated only with diseases, they perform several functions necessary for the body and the environment, such as the decomposition of substances.
When fungi invade the body, the immune system responds by attacking the foreign agent and defending the body.
Some factors can make the defense ineffective, such as the type of infection or the immune condition. In this case, treatment with medications is necessary and helps to reduce the damage and symptoms to the body.
Histoplasmosis generally does not pose a serious risk to the patient, and is effectively combated by antibodies. However, the severity of the symptoms and the type of involvement depend on the exposure to the fungus and on the patient’s condition (which your pet can too).
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