Imported Acute Histoplasmosis With Rheumatologic Manifestations in Spanish Travelers

Histoplasmosis is an infection that occurs when conidia of the dimorphic fungus Histoplasma capsulatum var capsulatum are inhaled into the lungs. It is the most common systemic mycosis diagnosed among European travelers returning from endemic areas of Central and South America, ^1–3 and in recent years, a growing number of cases, both isolated and in clusters, have been detected in nonendemic areas such as Europe. ^4–7 This rise in apparent cases of histoplasmosis is thought to be a result of increased international travel, especially tourism, cooperation, and trade. However, heightened awareness of the clinical manifestations and epidemiology of histoplasmosis by health care practitioners in these countries may have also played a part in increasing diagnosis. Published data have undoubtedly underestimated the true magnitude of this travel‐related mycosis (as well as other geographically restricted endemic mycoses such as coccidiomycosis, paracoccidioidomycosis, and penicilliosis), and many cases, especially those asymptomatic or presenting as a mild nondescript febrile illness, often go undiagnosed.

Most cases of imported histoplasmosis are known to occur in small clusters with a common source of infection. Usually, the individuals affected in these outbreaks have a history of participation in leisure and work activities, which involve heavy exposure to bat or bird droppings (mostly cavers and volunteers with recent involvement in cleaning tasks or rehabilitation of old buildings). ^8–12

More than 95% of immunocompetent people remain asymptomatic following low‐inoculum infection with H capsulatum. ² In the few symptomatic cases which occur, clinical presentation includes a self‐limited benign pulmonary illness with fever, malaise, dry cough, and chest pain. Disseminated severe disease is only observed in those individuals with a high degree of prior exposure to guano or impaired cellular immunity. ^6,13,14

Here, we describe an outbreak of acute histoplasmosis with unusual clinical manifestations among four previously healthy Spanish travelers who had previously vacationed in Ecuador. None of the patients had engaged in any of the activities commonly considered as being of high risk for acquiring histoplasmosis. The diagnosis was based on several different techniques, including skin testing, serology, and a real‐time polymerase chain reaction (PCR)‐based assay.

Material and methods

Serology

Detection of precipitating antibodies against H capsulatum in patient sera was done by an immunodiffusion (ID) test according to manufacturer’s recommendations (ID Fungal Antibody System; Immuno‐Mycologics Inc, Norman, OK, USA).

PCR assay

Primers and probes were designed on the basis of targeting the nucleotide sequence of the Standard Transcribed Spacer (ITS1) recombinant DNA region of this species. Forward primer was 5′‐CCA‐CCCTTGTCTACC‐3′ (primer Hcits1‐1) and the reverse primer was 5′‐GGAACCAAGAGATCCGT‐3′ (primer Hcits1‐2). The amplified fragment was 182 bp in length. The probes were marked by fluorescence resonance energy transfer technology being HC1‐Fluos 5′‐GTCGGTGAACGATTGGCGT‐3′‐LCFluorescein and HC1‐Red 5′‐LCRED640‐GAGCATGAGAGCGATAA‐TAATCCAGT‐3′ (Tib Molbiol, Berlin, Germany) (Roche). PCR reactions were performed in the LightCycler 2.0 System (Roche). The kit LightCycler Fast Start DNA Master Hybridization Probes (Roche) was used as described by the manufacturer. DNA extraction from sera was done using the NucleoSpinBlood Kit (Macherey‐Nalgen, Cultek, Madrid, Spain). A total of 200 mL of each serum was used for the extraction of DNA following the manufacturer’s instructions. Experiments were repeated three times on three separate days.

Outbreak description

In August 30, 2005, four Spanish female travelers returning from a 1‐month trip to Ecuador presented at the Outpatient Department of our Tropical Medicine Unit with a history of acute febrile illness, an array of skin lesions compatible with erythema nodosum, and arthralgia. They had been vacationing from July to August 2005 in the Andean highlands near Otavalo, Ecuador, where they had worked as volunteers in rural communities aiding in both agricultural and domestic chores. Throughout their stay, they had slept at the peasants’ homes and mentioned having had occasional contact with hens as well as other domestic animals. However, they did not visit caves or recall direct exposure to bird guano. Within 2 weeks of their return, they had each separately consulted their general practitioner, complaining of dysthermia, asthenia, painful skin nodules in the legs, and moderate pain in the joints. This clinical picture began in Ecuador approximately 1 week prior to their return to Spain. One of the subjects had also presented with dry cough and chest pain and had been subsequently hospitalized after a chest X‐ray showed signs of pneumonia. In all four patients, a history of high fever and chills beginning the previous weeks had been present, and two of the subjects still had persistent febricula at the time of their first visit to our clinic. When they were seen in our clinic, they all appeared to be in good clinical condition and, apart from the aforementioned febricula, their constants were normal. In three patients, we observed several painful erythemato‐violaceous skin lesions particularly located on the limbs, which were clinically consistent with erythema nodosum. All of them complained of spontaneous pain in the joints (especially knees, ankles, and elbows) and in two, there were clinical symptoms of patellar enthesitis at the tibial tuberosity. However, in neither case was there any evidence of frank arthritis. Laboratory abnormalities were modest and included mild elevations in the erythrocyte sedimentation rate and C‐reactive protein. All other biochemical and hematological parameters were normal. Chest radiography showed no lung infiltrates or hilar–mediastinal lymphadenopathy except in one patient who developed a segmentary condensation in the left upper lobe and base as well as slightly enlarged left hilar nodes. Histoplasmin skin tests and serology (ID) were performed and gave positive results in all four patients. One case also gave a positive result after DNA detection by real‐time PCR (Table 1). In accordance with recommended treatment guidelines, antifungal therapy was not indicated and the patients were thus treated symptomatically. ¹⁵ Although the four patients suffered fatigue and mild arthralgia for several weeks, recovery was otherwise uneventful. The erythema nodosum lesions promptly resolved after completion of a short course of treatment with nonsteroidal antiinflammatory agents.

Table 1

Clinical, radiological, analytical features and diagnostic results

Patient	Fever	Cough	Malaise	Arthralgia	Erythema nodosum	Lung infiltrates	ESR/CRP	IDRH	ID	PCR
1	+	+	+	+	+	+	90/5.6	+	+	+
2	+	+	+	+	+	−	18/1.5	+	+	−
3	+	−	+	+	+	−	25/2.1	+	+	−
4	+	−	+/−	+	−	−	12/1.2	+	+	−

ESR = erythrocyte sedimentation rate; CRP = C‐reactive protein; IDRH = intradermal reaction with histoplasmin; ID = immunodiffusion; PCR = polymerase chain reaction.

Conclusions

Due to historical and cultural bonds, histoplasmosis‐endemic Latin America has always constituted a major tourist destination for Spanish travelers, and histoplasmosis has traditionally been considered as a “travel‐related disease.” However, in spite of this, many physicians in nonendemic countries such as Spain continue to be unacquainted with the epidemiology, clinical features, and diagnostic tests of histoplasmosis. This explains why this disease is rarely considered in the differential diagnosis of fever of unknown origin after tropical exposure. Yet, this fungal disease accounts for a significant amount of cases of nonspecific flulike illness among returning travelers, but its inconsistent clinical manifestations often hinder a straightforward diagnosis. Thus, a high degree of suspicion and epidemiological reasoning on the part of the physician is required to consider histoplasmosis in differential diagnosis.

In this rather disheartening context, the outbreak described in this report fittingly illustrates four points: (1) rheumatologic manifestations (and most notably erythema nodosum) in patients with a recent history of travel should always alert the clinician of the possibility of histoplasmosis. (2) The classical epidemiological setting of a well‐recognized and obvious exposure to bird or bat guano may not necessarily be present in the patient’s history. (3) The frequent presentation of imported histoplasmosis in clusters of cases reinforces the need to screen for histoplasmosis in all traveling partners of a proven case irregardless of clinical manifestations. (4) Skin testing by intradermal reaction with histoplasmin (IDRH) plays a useful role in the prompt diagnosis of histoplasmosis in previously nonexposed European travelers.

1. With respect to rheumatologic manifestations, well described in epidemics involving American residents, ¹⁷ these manifestations are thought to represent a systemic inflammatory reaction to the primary pulmonary infection. Typically, these patients have rapidly additive arthritis or arthralgia, which tends to be symmetric. Knees, ankles, wrists, and small joints of the hand are the most common sites affected. Some also develop erythema nodosum, a condition occasionally constituting the sole presenting rheumatologic complaint. For unknown reasons that may be related to genetic differences in the fungal strains, erythema nodosum, uncommon in US patients with autochthonous histoplasmosis, is more frequently seen in patients from Latin America. ^16–18 Also interestingly, women are known to be more prone to suffer from rheumatologic complications. ^17,18

2. All these features were present in the patients of our report. Thus, we strongly suggest that all travelers returning from endemic countries (especially if they are female and have visited Latin America) who present with a febrile illness accompanied with rheumatologic manifestations such as arthralgia and/or erythema nodosum be screened for histoplasmosis. In the context of a compatible epidemiological and geographic history, this clinical association of signs and symptoms should also prompt the search for other endemic mycoses such as coccidioidomycosis.

3. Well‐recognized epidemiological risk factors for infection by H capsulatum include activities, which often entail heavy exposure to guano from bats or birds such as speleology, ^8–10 contact with chicken coops, and sleeping or working in poorly ventilated mines or old buildings. ¹² However, not all cases of travel‐related histoplasmosis are associated with clear exposures. In fact, a previous report showed cases where sleeping outdoors was the only statistically significant risk factor detected in a series of 69 IDRH‐positive Spanish travelers returning from their first trip to Latin America. ⁴ Thus, it seems clear that inadvertent inhalation of conidia may occur at a great variety of locations, making the classical epidemiological setting of a traveler’s exposure to guano very helpful but not indispensable for suspicion of histoplasmosis. In our outbreak, none of the patients had engaged in any of the activities commonly considered as being of high risk for acquiring histoplasmosis.

4. Most histoplasmosis cases are asymptomatic and may go unnoticed unless a cluster is suspected. Outbreaks of histoplasmosis among travelers include patients developing illnesses with a broad spectrum of clinical findings, ranging from those asymptomatic (the vast majority) to those experiencing a severe progressive disseminated disease (mainly the elderly, people with chronic lung disease, and the immunocompromised). However, the most characteristic (classical) presentation involves a febrile respiratory illness with high‐grade fever, chills, headache, nonproductive cough, chest pain, and fatigue occurring 1 to 3 weeks after exposure, with chest radiographs often revealing diffuse reticulonodular infiltrates and mediastinal lymphadenopathy. This more easily recognizable form of the disease can serve as sentinel for outbreak events, allowing for the detection of other less clinically expressive or even silent cases. Only one of the four patients reported here developed a moderate respiratory illness with clinical features matching those aforementioned, her chest X‐ray showing segmentary condensations and enlarged hilar nodes typical of histoplasmosis. In our case, diagnosis of the remaining three cases was made easier by this “sentinel patient.”

5. It has been said that while histoplasmin skin testing remains helpful in epidemiologic studies and for evaluation of immunity, it is rarely useful diagnostically. ¹⁹ Although considered highly sensitive, background positivity rates of 50% to 80% in endemic areas limit the use of this information for diagnostic purposes. ¹⁹ Skin test reactivity may persist positive long after recovery from the symptomatic disease, making determination of the significance of positive results confusing. Also, skin tests may be falsely negative in up to 20% of patients with chronic pulmonary disease and over 50% with disseminated histoplasmosis, compromising their use for diagnosis. ¹⁹ Another drawback often noted by its detractors is that skin tests may boost antibody titers, further complicating interpretation of serologic tests. ²⁰ However, this conclusion does not necessarily apply to countries such as ours, in which the disease, although occasionally found, is not present endemically. In this setting, skin testing constitutes a very helpful tool for the prompt diagnosis of histoplasmosis. ⁵ Histoplasmosis is not easy to diagnose.

The definitive diagnostic method for this mycosis is the growth of H capsulatum from tissues or body fluids. However, the sensitivities of cultures are variable depending on patients, clinical presentation, and sample. In addition, the fungus may take as long as 12 weeks to grow in vitro. Serologic tests play an important role in the diagnosis of several forms of the disease, but 2 to 6 weeks are required for appearance of antibodies, and they are negative in up to 40% of patients, especially those with acquired immunodeficiency syndrome. ²¹ Complement fixing, ID, and latex agglutination are the more widely used antibody‐testing techniques. In most patients, titers decline to low or undetectable levels over a 2‐ to 5‐year period, and thus, background seropositivity is not a major limitation for serologic testing, even in endemic countries such as the United States. This holds especially true for patients from European countries in which histoplasmosis is nonendemic and for those who refer no previous history of extensive traveling in the Americas.

In our case, results of the serologic tests (ID) were positive in the four patients. Other diagnostic tools have been developed with the goal of generating an early and more reliable diagnosis. Antigen detection in urine and/or serum is a very useful method in the case of patients with disseminated histoplasmosis and is also considered to be of use in monitoring the effect of treatment. However, the sensitivity of this test is variable, and cross‐reactions with other endemic mycoses have been observed. ²² In addition, this test is not readily accessible outside the United States. PCR‐based detection methods have been also described for detecting H capsulatum, the majority of which use conventional PCR, targeted to multicopy or unicopy genes. The sensitivity of these molecular techniques varies among the different assays described, and little data on testing clinical samples has been reported. ²³ In the present report, DNA detection in blood through real‐time PCR was positive in one of the patients.

The International Health Center receives economical support from Red de Investigación de Centros de Enfermedades Tropicales.

Declaration of Interests

The authors state that they have no conflicts of interest.

This paper has been presented at the 12th SEIMC (Spanish Society of Infectious Diseases and Clinical Microbiology) Congress, Valencia, on May 10, 2006, to May 13, 2006, and at the 5th SEMTSI (Spanish Society of Tropical Medicine and International Health) Congress, Tenerife, on May 24, 2006 to May 26, 2006.