Clinical characteristics and seasonal patterns of nasal leech infestation: A retrospective case series

Abstract

BACKGROUND

Nasal leech infestation is an uncommon but clinically important cause of unilateral epistaxis, particularly in rural and endemic regions. Because symptoms may be nonspecific and leech saliva contains anticoagulant and anesthetic substances, diagnosis may be delayed.

AIM

To retrospectively analyze the clinical characteristics, environmental exposure history, seasonal distribution, management strategies, and immediate outcomes of patients with nasal leech infestation, with the aim of improving clinical awareness, early diagnosis, and timely treatment of this uncommon cause of unilateral epistaxis in rural and endemic regions.

METHODS

We conducted a retrospective single-center case series of patients diagnosed with nasal leech infestation at the otorhinolaryngology outpatient clinic of our hospital between April 1, 2021 and April 1, 2026. Demographic characteristics, environmental exposure history, clinical presentation, seasonal distribution of presentations, management, and immediate outcomes were retrospectively analyzed.

RESULTS

A total of 38 patients were included. Of these, 25 patients were aged ≤ 14 years. All patients lived in mountainous or peri-mountainous rural areas and had a history of exposure to untreated natural water sources or humid outdoor environments. Presentations clustered in summer and early autumn, especially in August and September. The most common symptom was unilateral epistaxis, followed by direct visualization of a leech and nasal foreign body sensation. All leeches were removed during the initial outpatient visit under anterior rhinoscopy or nasal endoscopic guidance using forceps, following topical anesthesia. No patient required general anesthesia, blood transfusion, or hospital admission.

CONCLUSION

Nasal leech infestation should be considered in patients with persistent unilateral epistaxis, especially in endemic rural areas and in patients with recent freshwater exposure. Careful endoscopic examination facilitates diagnosis and immediate removal. Further prospective studies are needed to evaluate long-term outcomes and optimal removal techniques.

Key Words: Nasal leech infestation; Epistaxis; Live foreign body; Seasonal distribution; Nasal endoscopy

Core Tip: Nasal leech infestation is a rare but important cause of persistent unilateral epistaxis, particularly in children living in rural mountainous regions with freshwater exposure, as found in this retrospective case series. In addition, cases tended to cluster during summer and early autumn. Nasal endoscopy enabled accurate diagnosis and complete removal in all cases without general anesthesia, transfusion, or hospitalization. Therefore, maintaining clinical suspicion of nasal leech infestation and performing prompt endoscopic evaluation may prevent significant bleeding and other complications.

INTRODUCTION

Most leeches are hematophagous parasites that inhabit freshwater and humid terrestrial environments[1]. Human infestation typically occurs following exposure to contaminated water sources. Leech infestation involving the nasal cavity, nasopharynx, oropharynx, larynx, and even the lower airway is a rare but clinically significant condition encountered in otolaryngology practice[2-6]. Among the reported sites, the nasal cavity is most frequently affected. Patients commonly present with unilateral epistaxis, nasal obstruction, or foreign body sensation[7-10]. However, diagnosis may be delayed due to the nonspecific nature of symptoms and the biological properties of leech saliva. Leeches secrete hirudin and other bioactive substances with anticoagulant, vasodilatory, and anesthetic effects, which can result in painless but persistent bleeding[1]. Consequently, leech infestation may be overlooked in the differential diagnosis of recurrent unilateral epistaxis, especially in non-endemic settings.

The existing literature on nasal leech infestation consists of isolated case reports or small case series, with limited systematic analysis of demographic information, clinical characteristics, and seasonal patterns. By integrating evidence from the literature with clinical experience, a comprehensive evaluation of patient presentation and environmental exposure can be conducted to improve early recognition and management.

Therefore, the present retrospective study aims to analyze the clinical features, seasonal variation, and management outcomes of patients diagnosed with nasal leech infestation at our institution. By summarizing our clinical experience, we seek to enhance awareness of this rare entity and facilitate timely diagnosis and appropriate treatment in otolaryngologic practice.

MATERIALS AND METHODS

Study design and patient selection

This retrospective single-center case series was conducted at the otorhinolaryngology outpatient clinic of People’s Hospital of Mabian Yi Autonomous County between April 1, 2021 and April 1, 2026. Patients were identified through the outpatient electronic medical record system and nasal endoscopy records. Patients were included if a live leech in the nasal cavity was confirmed by anterior rhinoscopy or nasal endoscopy and if sufficient clinical information was available for analysis. Any patients with uncertain diagnoses, duplicate records, non-nasal leech infestation, or insufficient documentation were excluded.

Demographic characteristics and other data such as residence, ethnicity, presenting symptoms, symptom duration, exposure history, laterality, attachment site, removal method, need for anesthesia or hospitalization, immediate complications, and available follow-up information were retrospectively extracted from medical records. The exposure categories included drinking untreated pond or stream water, swimming or washing the face in ponds or streams, and passing through humid bushes or grassy areas. These categories were not mutually exclusive, and each patient could report more than one exposure.

This study was approved by the Ethics Committee of People’s Hospital of Mabian Yi Autonomous County (EC-2026-06). After removal, nasal endoscopy was repeated to confirm complete extraction and to inspect both nasal cavities and the nasopharynx for additional parasites, mucosal injuries, or active bleeding. No patient developed post-removal bleeding requiring further endoscopic or surgical intervention.

Statistical analysis

Descriptive statistical analysis was performed using SPSS 27.0. Categorical variables are presented as counts and percentages. Continuous variables were assessed descriptively and are reported as mean ± SD and median with interquartile range when distributions were skewed. No inferential comparison was performed due to the descriptive nature and small sample size of this case series.

RESULTS

Institutional case series

Demographic characteristics: A total of 38 patients were included in this study, comprising 21 males (55.3%) and 17 females (44.7%). The patients’ ages ranged from 1 to 79 years, with a mean age of 23.87 ± 26.3 years and a median age of 7.0 years (interquartile range, 54 years).

The majority of patients were ≤ 14 years old (n = 25, 65.8%) (Figure 1). Ethnically, 28 patients (73.7%) belonged to the Yi minority group, while 10 patients (26.3%) were of Han ethnicity. All patients resided in mountainous or peri-mountainous rural areas and had a history of exposure to untreated natural water sources (e.g., streams and ponds) and humid shrub environments. Retrospective analysis of medical histories revealed that 15 patients (39.5%) reported passing through humid bushes or grassy areas, 21 (55.3%) habitually drank untreated pond or stream water, and 24 (63.2%) reported swimming or washing their faces in ponds or streams.

Figure 1 Age distribution of patients with nasal leech infestation. Bar chart illustrating the age distribution of 38 patients diagnosed with nasal leech infestation. The majority of cases occurred in children aged ≤ 14 years (n = 25), followed by adults aged 15-59 years (n = 7) and elderly patients aged ≥ 60 years (n = 6). The findings indicate a predominance of cases in the pediatric population.

Course of illness and seasonal characteristics: The clinical course was predominantly acute, ranging from 1 day to 60 days, with a mean duration of 8.66 ± 11.56 days and a median duration of 5.0 days (interquartile range, 8 days). Cases showed seasonal clustering of clinical presentations in summer and early autumn, particularly in August and September (Figure 2).

Figure 2 Seasonal distribution of nasal leech infestation cases (2021-2026). Monthly case counts of patients presenting with nasal leech infestation during the study period. Presentations clustered in summer and early autumn, particularly in August and September.

Clinical presentation: All 38 cases involved nasal leech infestation (Figure 3). Epistaxis was the most common presenting symptom (n = 18, 47.4%), followed by visualization of a leech within the nasal cavity (n = 16, 42.1%) and a sensation of a nasal foreign body (n = 8, 21.1%). Most infestations were unilateral (n = 36, 94.7%), with a slight predominance on the left side (n = 20, 52.6%).

Figure 3 Live leeches identified in the nasal cavity under nasal endoscopy. These images show the live leeches in different locations within the nasal cavity under nasal endoscopy. A: At the anteroinferior end of the middle turbinate; B: In the common nasal meatus; C: In Little’s area; D: In the middle meatus.

Management: A small amount of 1% dicaine gel (H13021217) was applied directly to the visible sucker of the leech under anterior rhinoscopic or endoscopic visualization. The usual amount was approximately 0.5-1.0 mL, corresponding to an estimated dose of 5-10 mg of tetracaine hydrochloride (10 mg/mL). The amount used was minimized according to the visible size and location of the leech and was not calculated according to a formal age- or weight-based dosing protocol. No immediate adverse reaction attributable to topical dicaine was documented in this case series.

After application, the leech was promptly extracted using ethmoid forceps or hemostatic forceps. Forceps with insufficient gripping strength at the tip, such as bayonet forceps, were avoided. After removal, nasal endoscopy was performed to confirm complete extraction and exclude the possibility of residual attachment or additional parasites. Particular caution was taken in children to avoid excessive dosing of topical anesthetic. Patients with known hypersensitivity to the anesthetic agent or significant cardiopulmonary instability were considered contraindicated for routine topical application.

All extraction procedures were performed by otorhinolaryngology specialists in the outpatient clinic. No systemic sedation or general anesthesia was used. All leeches were successfully removed under nasal endoscopic guidance using forceps in outpatients. No patients required general anesthesia, blood transfusion, or hospital admission.

DISCUSSION

In the present study, we analyzed the clinical features of patients diagnosed with nasal leech infestation. The predominant form of presentation was unilateral epistaxis, although a subset of patients reported foreign body sensation or directly witnessed a moving organism within the nasal cavity. Endoscopic examination confirmed live leeches in all cases, which were attached to regions within the nasal cavity. Endoscopic removal was successful in all patients, and no major perioperative complications were encountered.

The majority of previously published studies of nasal leech infestation are single case reports or small case series. In this retrospective study, we found that children and adolescents aged ≤ 14 years constituted the primary affected population. This finding is consistent with studies by Chen et al[10] and Montazeri et al[11], which also reported that pediatric patients made up most cases. Higher incidence among children and adolescents may be associated with behavioral factors, as they are more likely to swim or play in natural water sources and engage in outdoor activities in bushy or grassy areas. However, whether this reflects a general epidemiological pattern or a regional exposure-related phenomenon remains uncertain. Children may undergo more frequent contact with untreated freshwater sources during swimming, washing, or outdoor play, but individual exposure frequency was not systematically measured in this retrospective study.

All affected individuals reported prior exposure to environments conducive to leech habitation, including ponds, streams, moist vegetation, and grassy areas. Leeches are known to inhabit freshwater and humid terrestrial ecosystems, and their locomotion and host-seeking activity is strongly influenced by environmental temperature and moisture[1]. Experimental and ecological data suggest that leeches exhibit increased activity within a temperature range of approximately 20-40 °C, with peak activity around 30-35 °C[12]. In our region, ambient temperatures during December, January, and February frequently decline to ≤ 5 °C, during which no cases of infestation were observed. This seasonal distribution may reflect both diminished leech activity at lower temperatures and reduced human exposure to natural water sources during colder months. Conversely, as environmental temperatures rise, enhanced leech movement and feeding behavior may increase the probability of human infestation. The observed seasonal fluctuation in case incidence appears consistent with the known physiological and behavioral characteristics of leeches. This pattern may be related to increased environmental activity of leeches and greater human freshwater exposure during warmer months; however, because the population at risk, exposure frequency, and meteorological variables were not systematically measured, this study cannot determine seasonal incidence or establish a causal relationship with temperature. In addition, poor drinking water hygiene may be an important contributing factor to leech infestation. Therefore, in leech-endemic mountainous regions, educating the public to avoid drinking untreated stream or pond water and to avoid unprotected exposure to swamps, bushes, grassy areas, streams, and ponds is an important measure for preventing leech infestation.

Recurrent unilateral epistaxis was the most common presenting symptom among patients. During feeding, leeches secrete hirudin, a potent thrombin inhibitor, in addition to vasodilatory and anesthetic substances[1]. Hirudin disrupts the coagulation cascade and prevents clot formation, resulting in persistent or intermittent bleeding even after partial detachment. The anesthetic properties of leech saliva may delay symptom recognition and diagnosis by reducing local discomfort. However, epistaxis was not the only clinical manifestation of leech infestation. In this case series, several patients sought medical attention after experiencing a crawling sensation or observing the leech protruding from the anterior naris, rather than due to significant hemorrhage. These findings underscore the importance of maintaining a high index of suspicion in patients presenting with unexplained unilateral epistaxis, particularly when there is a history of freshwater exposure. In some previously reported cases, patients had no significant discomfort, and nasal leech infestation was discovered only through endoscopic evaluation after they developed severe anemia[13]. It is true that persistent unilateral epistaxis has a broad differential diagnosis, which can include nasal foreign bodies, traumatic mucosal injuries, rhinosinusitis, septal lesions, vascular malformations or hemangioma, benign or malignant tumors, and coagulation disorders. Nasal leech infestation should be considered when epistaxis occurs in patients from endemic rural areas, particularly when accompanied by recent exposure to untreated freshwater, foreign body sensation, intermittent bleeding, or visualization of a moving organism. Therefore, careful nasal endoscopy is critical for diagnosis.

There are many methods of leech removal, including concentrated saline, turpentine oil, caine-type anesthetics, and even electrocautery[14,15]. One reported technique involves grasping the leech with hemostatic forceps for a few seconds until it detaches spontaneously[3]. The “attraction method”, in which a basin of clean water is placed in front of the nostril to lure the leech out, is also frequently mentioned[16,17]. From the researchers’ experience, it is generally recommended to immediately spray lidocaine or dicaine gel onto its body upon visualization. This rapidly inactivates the leech and facilitates safe removal while avoiding forceful traction, which may leave mouthparts such as the teeth and jaw of the anterior sucker embedded in the mucosa and lead to secondary infection and continuous bleeding from the site[12]. After removal, a thorough endoscopic examination should be performed to inspect both nasal cavities, including all meatuses and the nasopharynx. In one previously managed case, after successfully removing one leech from the right common nasal meatus, routine nasal endoscopy revealed another leech in the middle meatus of the same side.

This case series primarily reports infestations of the nasal cavity. Based on the literature review conducted by the researchers, leeches may attach to various anatomical sites, including the nasal cavity, nasopharynx, oropharynx, hypopharynx, larynx, trachea, esophagus, and vulvar region[18-20]. In addition to the nasal and nasopharyngeal infestations reported and reviewed in our study, leeches have also been described as attaching to the glottis, causing respiratory distress; to the pharynx, resulting in recurrent hemoptysis and foreign body sensation; and to the main airway, where they were initially suspected to be tumors[6,19-21].

Taken together, our findings reinforce the fact that leech infestation, although rare, should be included in the differential diagnosis of persistent unilateral epistaxis in endemic or rural settings. Early recognition and prompt endoscopic removal can prevent complications such as significant blood loss, airway compromise, or secondary infection[13,22]. The value of the present study lies in summarizing a relatively large single-center series of nasal leech infestations in a mountainous endemic region, with emphasis on exposure history, seasonal clustering of presentations, clinical manifestations, and immediate outpatient management outcomes.

Limitations

This study has several limitations. Because this retrospective case series was based on final diagnostic records rather than prospective screening of a defined population at risk, selection bias and incomplete case ascertainment cannot be fully excluded; the findings may not be fully generalizable to other geographic or clinical settings. Furthermore, because data were extracted from outpatient medical records rather than collected using a standardized prospective protocol, some clinically relevant variables were unavailable or incompletely recorded. These included standardized bleeding severity, baseline hemoglobin level, comorbidities, exact diagnostic delay before presentation, formal misdiagnosis history, precise attachment site, leech species, and complete follow-up information. Because many patients came from remote mountainous villages with limited transportation and communication access, systematic long-term follow-up was not feasible in routine clinical practice. Therefore, this case series mainly describes the clinical features and immediate management outcomes at the initial visit. As a result, the formal misdiagnosis rate, diagnostic delay, rebleeding rate, recurrence, wound healing status, and any delayed complications could not be reliably assessed. Furthermore, the relatively small sample size restricted our ability to perform multivariate analysis or meaningful subgroup comparisons based on age, exposure category, or anatomical attachment site. Future prospective multicenter studies with larger cohorts, standardized data collection, and systematic follow-up are necessary to validate our findings. Additional studies could also help to clarify epidemiological patterns and identify factors associated with diagnostic delay, difficulty in removal, and clinical outcomes in nasal leech infestation.

CONCLUSION

This retrospective single-center case series suggests that nasal leech infestation, although uncommon, should be considered in the differential diagnosis of persistent unilateral epistaxis. In particular, patients from rural mountainous areas with recent exposure to untreated freshwater or humid outdoor environments may be at risk. In this series, most patients were children, and presentations clustered in summer and early autumn; however, these findings should be interpreted as descriptive observations, rather than evidence of seasonal incidence or causal risk factors.

Careful nasal endoscopy is essential for diagnosis and to exclude the possibility of additional parasites after removal. In the present series, immediate outpatient removal under endoscopic guidance after topical anesthesia was achieved in all included patients. Further prospective studies with standardized follow-up are necessary to assess delayed complications or recurrence, as well as optimal removal techniques.