Epidemiologic evaluation of pulmonary paragonimiasis in Japan using a Japanese nationwide administrative database.

BACKGROUND: Paragonimiasis is a parasitic disease primarily contracted through consumption of undercooked freshwater crustaceans or wild boar meat. Large-scale nationwide epidemiological data on paragonimiasis are lacking. In this study, we aimed to investigate the nationwide epidemiology of hospitalized patients with paragonimiasis in Japan using a comprehensive nationwide Japanese administrative database. METHODS: We evaluated the Japanese Diagnosis Procedure Combination (DPC) data of patients diagnosed with pulmonary paragonimiasis between April 1, 2012 and March 30, 2020. The patients' address and information, including age, sex, treatment (medication: praziquantel; surgery: open thoracotomy or intracranial mass extirpation), Japan coma scale, comorbidities, and length of hospital stay, were extracted. RESULTS: Of the 49.6 million hospitalized patients, data were extracted on 73 patients with paragonimiasis, of whom 36 were male and 37 were female. The mean age was 49.7 years and the mean length of stay was 12.5 days. The most frequent comorbidity was pleural effusion (31.5 %), followed by pneumothorax (13.7 %). The sites of ectopic paragonimiasis in organs other than the lung included the liver (5.5 %), skin (4.1 %), and brain (2.7 %). Geographically, most patients were from the Kyushu region (54.8 %), followed by the Kanto region (22.0 %). Fukuoka Prefecture had the highest number of patients (22.0 %) by prefecture. During the study period, an average of 9.1 patients/year were hospitalized with lung paragonimiasis in Japan. CONCLUSION: Paragonimiasis has not completely disappeared in Japan; thus, physicians should be aware of paragonimiasis in the Kyushu region, especially in the Fukuoka Prefecture.

Clinical Characteristics of Human Pulmonary Dirofilariasis in Japan: An Uncommon Differential Diagnosis of a Solitary Pulmonary Nodule.

Human pulmonary dirofilariasis (HPD) is a zoonotic disease caused by Dirofilaria immitis. Most HPD cases are asymptomatic and are either detected during annual health checkups or incidentally identified during the investigation of other diseases, particularly primary or metastatic pulmonary lung cancers. However, the frequency and clinical features of Japanese patients with HPD remain unclear. We analyzed data from the Japanese Medical Abstract Society database and identified 69 cases between 1978 and 2022. The incidence of HPD increased until the 2000s but declined markedly in the 2010s. The incidence is higher in the southwestern region and lower in the northeastern region of Japan. Health checkups are the primary diagnostic opportunities. The Chugoku and Shikoku regions have had high incidence rates per population. The diagnosis of HPD using a noninvasive procedure is typically difficult because of the absence of specific clinical symptoms, and approximately 70% of the cases are detected using video-assisted thoracoscopic surgery. Climate change may increase the incidence of HPD in the northeastern region of Japan, and travel to countries with poor vector control may be a risk factor for HPD transmission. Physicians should consider this parasitic infectious disease when examining patients presenting with solitary lung nodules.

A note on the relationship between fecal larval excretion and Protostrongylus rufescens lungworm burden in sheep.

The examination of feces for stages of parasitic helminths is the most widely used methodology for the intravital diagnosis in domestic animals of patent endoparasitism including pulmonary nematode infections. Although there is only little information on the relationship of lungworm larval excretion and corresponding parasite burdens, fecal larval counts are used as indirect measure ("biomarker") for the intensity of infection, for instance in anthelmintic efficacy studies. To assess the relationship between fecal larval and Protostrongylus rufescens parasite counts in sheep, log-transformed data of 14 naturally infected animals were analyzed. The larval excretion of the sheep was monitored in approximately weekly intervals over 6 weeks before lungworm recovery. Analyses were performed on the larval counts (at a single time point or counts averaged over several consecutive time points) relating to parasite counts. Fecal larval counts and the P. rufescens nematode burden (range, 17 to 406) were significantly and strongly correlated (p < 0.05 for all analyses; Spearman's r > 0.6) with the number of larvae excreted increasing with increasing lungworm burden. Subsequently performed regression analysis demonstrated a statistically significant strong linear relationship between P. rufescens worm and fecal larval counts (p < 0.01 for all analyses; R2, range 0.5094 to 0.8150). Analyses based on larval counts averaged over two or more consecutive time points resulted in higher Spearman's r and R2 compared with analyses based on single time point larval counts. Despite of some variability, the analyses indicate that fecal larval counts can be regarded as a useful measure of the P. rufescens burden in sheep.

Schistosomes in the Lung: Immunobiology and Opportunity.

Schistosome infection is a major cause of global morbidity, particularly in sub-Saharan Africa. However, there is no effective vaccine for this major neglected tropical disease, and re-infection routinely occurs after chemotherapeutic treatment. Following invasion through the skin, larval schistosomula enter the circulatory system and migrate through the lung before maturing to adulthood in the mesenteric or urogenital vasculature. Eggs released from adult worms can become trapped in various tissues, with resultant inflammatory responses leading to hepato-splenic, intestinal, or urogenital disease - processes that have been extensively studied in recent years. In contrast, although lung pathology can occur in both the acute and chronic phases of schistosomiasis, the mechanisms underlying pulmonary disease are particularly poorly understood. In chronic infection, egg-mediated fibrosis and vascular destruction can lead to the formation of portosystemic shunts through which eggs can embolise to the lungs, where they can trigger granulomatous disease. Acute schistosomiasis, or Katayama syndrome, which is primarily evident in non-endemic individuals, occurs during pulmonary larval migration, maturation, and initial egg-production, often involving fever and a cough with an accompanying immune cell infiltrate into the lung. Importantly, lung migrating larvae are not just a cause of inflammation and pathology but are a key target for future vaccine design. However, vaccine efforts are hindered by a limited understanding of what constitutes a protective immune response to larvae. In this review, we explore the current understanding of pulmonary immune responses and inflammatory pathology in schistosomiasis, highlighting important unanswered questions and areas for future research.

The effect of pasture molluscicide on small lungworm infections and the productivity of grazing lambs.

The aim of this study was to assess the effect of pasture molluscicide treatment on the prevalence and severity of small lungworm infections, and the productivity of lambs grazing improved pastures in southeastern Australia. A randomised control field trial of 260 Merino-cross lambs was conducted on a commercially managed farm in South Australia with a history of high small lungworm prevalence. Separate groups of lambs rotationally grazed irrigated lucerne paddocks treated with iron chelate molluscicide or untreated control paddocks. Lambs were monitored every 2-6 weeks from weaning until slaughter with liveweight, lungworm and gastrointestinal nematode infection status measured. At slaughter indicators of small lungworm infection via inspection and carcass characteristics were assessed. The density of the intermediate host snail and lucerne pasture availability were also measured. There was a higher population of adult Prietocella barbara molluscs in the Control paddocks compared to the Treatment paddocks after molluscicide had been applied and prior to grazing commencing (206 vs. 14 snails/m2, respectively; P = 0.03; 95 % CI 8, 528). However, the overall mollusc density was similar between Control and Treatment. The prevalence of small lungworm infections was quite low during the trial (0-13 %), in both Control and Treatment lambs, except at day 94 when 48 % of 28 Control lambs were positive compared to none of 27 Treatment lambs (P < 0.001; 95 % CI 30, 66). A similar proportion of Treatment and Control lambs had evidence of small lungworm infection lesions at slaughter (both 67.8 %). Control lambs grew slightly faster than Treatment lambs, with an average daily gain of 202 (± 3 SEM) g/head/day for Control and 190 (± 4 SEM) for Treatment (P < 0.001) during the 112-day trial. Despite historic evidence of very high prevalence of lungworm infection in this region of southeastern Australia, iron chelate molluscicide treatment prior to lambs grazing the pasture had no demonstrable effect on the prevalence and severity of small lungworm infections, nor the productivity of lambs grazing these pastures. This study indicates that for a commercial sheep farm, additional molluscicide treatments of pastures after they are established, for the prevention of small lungworm infection, may not be warranted. Furthermore, requirements for more precisely monitoring snails are discussed.

Risk factors for lungworm-associated milk yield losses in grazing dairy cattle.

Dictyocaulus viviparus, the causative agent of bovine parasitic bronchitis, is an important parasite of dairy cattle. Infections can lead to substantial economic losses, due to mortality, reduced weight gain and milk production and treatment costs. There have been relatively few studies investigating herd management risk factors for infections with D. viviparus and lungworm-associated production losses. The aims of this study were (1) to assess the impact of (sub)clinical lungworm infections on productivity in dairy cows and, (2) to identify or confirm risk factors, related to herd management, for infections in grazing dairy cattle. Using a recombinant Major Sperm Protein (MSP)-based ELISA, the presence of D. viviparus antibodies in bulk tank milk (BTM) samples was evaluated on 717 and 634 farms at two-week intervals during two grazing seasons (2018 and 2019). Associations between milk antibody levels and production data (mean milk yield in kg/cow/day, percentage of fat and protein) were assessed, as well as associations with putative risk factors in the herd management, gathered through a questionnaire survey. In both years, there was a substantial, but non-significant, difference in the annual mean milk yield on farms with at least one BTM sample above the cut-off of 0.41 ODR, compared with the mean milk yield on farms that stayed under this threshold on each sampling day (-0.17 and -0.70 kg milk/cow/day in 2018 and 2019, respectively). In 2019, this association was stronger, and significant, when the cut-off was exceeded in at least two consecutive BTM samples (-1.74 kg milk/cow/day). BTM results were also significantly negatively associated with the closest milk production data during the two-weekly BTM sampling intervals in 2019. A single or two consecutive positive tests were used in the risk factor analysis as a proxy for lungworm-associated milk yield losses. Purchase of new animals (Odds Ratio (OR) = 2.68) and the proportion of the first grazing season covered by preventive anthelmintic treatment (OR up to 3.88, depending on proportion) were positively associated with lungworm-associated milk yield losses, while mowing at least 50 % of the pastures (OR = 0.57) was negatively associated with lungworm-associated milk yield losses. Our results suggest that the ELISA holds promise to identify herds with significant production losses due to lungworm infections, under the condition that BTM sampling is done repeatedly during the grazing season. Based on the confirmed risk factors, adjustments of the farm management could perhaps mitigate these losses.

Analysis of the misdiagnosis of 8 adult cases of paragonimiasis with lung masses as the main manifestation in Xishuangbanna, Yunnan.

OBJECTIVE: To summarize the clinical characteristics of adult cases of paragonimiasis with lung masses as the main manifestation in Xishuangbanna, Yunnan Province, analyze the causes of misdiagnosis, and improve the levels of clinical diagnosis and treatment. METHOD: We conducted a retrospective analysis of the clinical data and diagnosis and treatment of 8 adult cases of paragonimiasis with lung masses as the main manifestation that were diagnosed in the Oncology Department of People's hospital of Xishuangbanna Dai Autonomous Prefecture from July 2014 to July 2019. RESULT: All 8 patients were from epidemic paragonimiasis areas and had a confirmed history of consuming uncooked freshwater crabs. The clinical manifestations were mainly fever, dry cough, and chest pain. The disease durations were long, and peripheral blood eosinophil counts were elevated. The cases had been misdiagnosed as pneumonia or pulmonary tuberculosis. After years of anti-inflammatory or anti-tuberculosis treatment, the symptoms had not improved significantly. Patients eventually sought treatment from the oncology department for hemoptysis. Chest computed tomography showed patchy consolidation in the lungs, with nodules, lung masses, and enlarged mediastinal lymph nodes. CONCLUSION: Paragonimiasis is a food-borne parasitic disease. Early clinical manifestations and auxiliary examination results are nonspecific. The parasite most often invades the lungs, and the resulting disease is often misdiagnosed as pneumonia, pulmonary tuberculosis, or lung cancer (Acta Trop 199: 05074, 2019). To avoid misdiagnosis, clinicians should inquire, in detail, about residence history and history of unclean food and exposure to infected water and make an early diagnosis based on the inquired information and imaging examination results. For patients who have been diagnosed with pneumonia or pulmonary tuberculosis and whose symptoms do not improve significantly after anti-inflammatory or anti-tuberculosis treatments, their epidemiological history should be traced to further conduct differential diagnosis and avoid misdiagnosis.

Revisiting the Schistosoma japonicum life cycle transcriptome for new insights into lung schistosomula development.

Schistosome parasites are complex trematode blood flukes responsible for the disease schistosomiasis; a global health concern prevalent in many tropical and sub-tropical countries. While established transcriptomic databases are accessed ad hoc to facilitate studies characterising specific genes or gene families, a more comprehensive systematic updating of gene annotation and survey of the literature to aid in annotation and context is rarely addressed. We have reanalysed an online transcriptomic dataset originally published in 2009, where seven life cycle stages of Schistosoma japonicum were examined. Using the online pathway analysis tool Reactome, we have revisited key data from the original study. A key focus of this study was to improve the interpretation of the gene expression profile of the developmental lung-stage schistosomula, since it is one of the principle targets for worm elimination. Highly enriched transcripts, associated with lung schistosomula, were related to a number of important biological pathways including host immune evasion, energy metabolism and parasitic development. Revisiting large transcriptomic databases should be considered in the context of substantial new literature. This approach could aid in the improved understanding of the molecular basis of parasite biology. This may lead to the identification of new targets for diagnosis and therapies for schistosomes, and other helminths.

Toxoplasma gondii isolated from a Brazilian patient with rare pulmonary toxoplasmosis has a novel genotype and is closely related to Amazonian isolates.

Pulmonary toxoplasmosis is rare in immunocompetent patients. Herein, a Toxoplasma gondii strain isolated in Brazil from an immunocompetent patient who had severe pulmonary involvement was biologically and molecularly characterized for the first time. The TgHumIMTBr1 isolate was bioassayed in mice showing a virulent phenotype. Restriction fragment length polymorphism (RFLP) genotyping using 11 markers [SAG1, SAG2 (5´3´SAG2 and alt. SAG2), SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, Apico and CS3] revealed a new non-archetypal genotype assigned as #312. Genotyping using ROP18/ROP5 markers exhibited the virulent combination of alleles 4 and 1. Microsatellite analysis using 15 markers (TUB2, W35, TgM-A, B18, B17, M33, IV.1, X1.1, N60, N82, AA, N61, N83, M48 and M102) revealed an atypical genotype with three unique alleles and a rare combination of alleles 246 (W35) and 203 (TgM-A) that is typical of the Amazon region. Non-archetypal genotypes with unique alleles may function in the occurrence of severe toxoplasmosis in immunocompetent patients in Brazil. Attempts to isolate or molecularly detect T. gondii for further genotyping studies would contribute to the understanding of causes related to the severity of toxoplasmosis in immunocompetent patients.

An outbreak of Paragonimus westermani infection among Cambodian technical intern trainees in Japan, exhibiting various extrapulmonary lesions.

We encountered an outbreak of paragonimiasis among Cambodian technical intern trainees (TITs) at a food-processing factory in Fukuoka, Japan. The patients were 20-28 years old, seven females and two males, who had been in Japan for one to four years. All of them had consumed raw or undercooked Japanese mitten crab they purchased at a local grocery store near their training place. CT images showed multiple lesions not only in the lungs but in the extrapulmonary organs as well, such as subcutaneous tissues, abdominal muscles, and mesentery, in most of the patients. Their medical records indicated that all of them acquired infection in Japan, not in Cambodia. Diagnosis was made serologically and the patients were treated with praziquantel successfully. Foreign workers and TITs are increasing in Japan so rapidly, that food borne-infections, including paragonimiasis, should be considered in people from developing countries who have exotic dietary habits.

A retrospective clinical analysis of pediatric paragonimiasis in a Chinese children's hospital from 2011 to 2019.

Diagnosis of pediatric paragonimiasis is difficult because of its non-specific clinical manifestations. We retrospectively reviewed the records of pediatric paragonimiasis in Children's Hospital of Fudan University from January 2011 to May 2019. The confirmed diagnosis of paragonimiasis was based on positive anti-parasite serological tests from the local Center for Disease Control (CDC). A total of 11 patients (mean age: 7.7 ± 3.1, male-female ratio: 7:4) diagnosed as paragonimiasis were included. 81.8% were from endemic areas such as Sichuan and Yunnan, and 36% had a clear history of raw crab or crayfish consumption. The characteristic clinical features of pediatric paragonimiasis were eosinophilia (100%), pleural effusion (81.8%), hepatomegaly (54.5%), ascites (54.5%), and subcutaneous nodules (45.5%). Misdiagnosed with other diseases including tuberculosis (18.2%), pneumonia (9.1%), intracranial space-occupying lesions (9.1%) and brain abcess (9.1%) led to rehospitalization and prolonged hospitalization. For treatment, a 3-day course of 150 mg/kg praziquantel (PZQ) didn't show ideal treatment effectivity and 63.6% needed more than one course of PZQ, while triclabendazole in a total dose of 10 mg/kg had a better efficacy to stubborn manifestations. This study indicated that pediatric paragonimiasis was often misdiagnosed, and the treatment with a 3-day course of 150 mg/kg PZQ had a high rate of failure.

Host Immunity and Inflammation to Pulmonary Helminth Infections.

Helminths, including nematodes, cestodes and trematodes, are complex parasitic organisms that infect at least one billion people globally living in extreme poverty. Helminthic infections are associated with severe morbidity particularly in young children who often harbor the highest burden of disease. While each helminth species completes a distinct life cycle within the host, several helminths incite significant lung disease. This impact on the lungs occurs either directly from larval migration and host immune activation or indirectly from a systemic inflammatory immune response. The impact of helminths on the pulmonary immune response involves a sophisticated orchestration and activation of the host innate and adaptive immune cells. The consequences of activating pulmonary host immune responses are variable with several helminthic infections leading to severe, pulmonary compromise while others providing immune tolerance and protection against the development of pulmonary diseases. Further delineation of the convoluted interface between helminth infection and the pulmonary host immune responses is critical to the development of novel therapeutics that are critically needed to prevent the significant global morbidity caused by these parasites.

Clinical crenosomosis in a black bear (Ursus americanus).

An orphaned black bear (Ursus americanus) cub, estimated to be 9 months-of-age was presented to a wildlife rehabilitation facility in December of 2016. The cub was afebrile, under-weight (6.8 kg) and had a cough condition. Centrifugal sugar fecal flotation examination failed to detect any gastrointestinal helminth or protozoan parasites, but revealed the presence of first-stage nematode larvae (L1). Large numbers of L1 (>8000 L1/g) identified as Crenosoma sp. based on morphology were recovered using the Baermann technique. Three species (Crenosoma petrowi, Crenosoma potos, Crenosoma vulpis) have been reported from black bears. Based on larval length measurements (range = 253-277 µm; mean = 263 µm; n = 8), the L1 were tentatively identified as C. petrowi. Further molecular characterization using Polymerase Chain Reaction (PCR) and DNA sequencing of the small subunit (SSU) RNA gene and two regions of the large subunit (LSU) rRNA gene did not match any submissions in GenBank, but were most similar to Crenosoma mephiditis. There is a paucity of molecular data for members of the genus Crenosoma, with only information for Crenosoma vulpis (red fox), C. mephitidis (skunks), Crenosoma striatum (hedgehog) and Crenosoma sp. (red panda) in GenBank. Molecular analysis eliminates C. vulpis as a possibility in this case but due to the lack of submissions in GenBank, the identification of the L1 as C. petrowi based on length measurements could not be confirmed. Receiving in total, three separate courses of treatment with fenbendazole (50 mg/kg, oral, once a day for 3 days), fecal larval shedding ceased and clinical signs resolved. The black bear cub was released into the wild in June 2017. This is the first report of clinical chronic respiratory disease due to Crenosoma sp. infection in a black bear.

Aetiological agents for pulmonary exacerbations in children with cystic fibrosis: An observational study from a tertiary care centre in northern India.

Background & objectives: Pulmonary disease is the main cause of morbidity and mortality in cystic fibrosis (CF). The infection occurs with a unique spectrum of bacterial pathogens that are usually acquired in an age-dependent fashion. The objective of this study was to find out the aetiological agents in respiratory specimens from children with CF during pulmonary exacerbation and relate with demographic variables. Methods: In this observational study, airway secretions from children (n=104) with CF presenting with pulmonary exacerbations were collected and tested for bacteria, fungi, mycobacteria and viral pathogens using appropriate laboratory techniques. The frequencies of isolation of various organisms were calculated and associated with various demographic profiles. Results: Bacteria were isolated in 37 (35.5%) and viral RNA in 27 (29.3%) children. Pseudomonas was the most common bacteria grown in 31 (29.8%) followed by Burkholderia cepacia complex (Bcc) in three (2.8%) patients. Among viruses, Rhinovirus was the most common, identified in 16 (17.4%) samples followed by coronavirus in four (4.3%). Fungi and mycobacteria were isolated from 23 (22.1%) and four (3.8%) children, respectively. Aspergillus flavus was the most common fungus isolated in 13 (12.5%) children. Interpretation & conclusions: Pseudomonas was the most common organism isolated during exacerbation. Non-tuberculous mycobacteria were not isolated, whereas infection with Bcc and Mycobacterium tuberculosis was observed, which could probably have a role in CF morbidity. Polymicrobial infections were associated with severe exacerbations.

Surgery for Pulmonary Parenchymatous Schistosomiasis (Bilharziomas): A 20-Year Single-Centre Experience.

BACKGROUND: Pulmonary schistosomiasis may complicate urinary or intestinal infestations. Pulmonary pathology is either in the acute or chronic form. The chronic form of the disease may result in granuloma formation. This study presents 20 years of experience in surgical management of pulmonary bilharziomas. METHODS: A retrospective review was undertaken of 17 consecutive patients who had surgery for lung bilharziomas from 1996-2016. Demographics, clinical presentation, underlying lung disease, investigations performed, operative procedure, and outcome were retrieved and reviewed. RESULTS: All patients were males, with ages ranging from 22-52 years (median 33 years). Haemoptysis was the main presentation (53%). Coexisting lung tuberculosis was present in five (29.4%) patients. Indications for surgery were solitary shadows in 12 (70.6%) patients and persistent tuberculous cavities in five (29.4%) patients. Segmentectomy was performed in one (5.9%) patient, lingulectomy in one (5.9%) patient, lobectomy in 14 (82.3%) patients, and bi-lobectomy in one (5.9%) patient. The histologic nature of the infestation was: bilharzial ova with extensive granulomatous reaction and suppuration in eight cases (47%); both tuberculosis and bilharzial ova within a granulomatous tissue reaction in five cases (29.4%); and bilharzial ova within malignant tissue in four cases (23.6%). There was no operative mortality. One (1) patient (5.9%) developed postoperative bronchopleural fistula after left upper lobectomy; surgical repair of the fistula and omental flap buttress was needed after failure of conservative management. CONCLUSION: Pulmonary schistosomiasis is not an uncommon infestation and occurs more frequently in patients with underlying tuberculosis. It may predispose to granulomatous parenchymatous lung masses or even malignancy, which necessitate surgical intervention with a good outcome. However, predisposition of pulmonary schistosomiasis for the development of bronchogenic carcinoma warrants further studies.

Lungworm (Crenosoma goblei) Infection in Unweaned Free-Ranging Raccoons (Procyon lotor) in Washington State, USA.

Larval parasites morphologically identified as Crenosoma goblei were found in orphaned raccoons (Procyon lotor) admitted to a wildlife rehabilitation center in Washington State, US. Partial 18S rRNA and cytochrome oxidase I gene sequences were most similar to other Crenosoma spp. Although commonly reported in free-ranging raccoons throughout much of the central and eastern US, this finding extends the range of C. goblei into the Pacific Northwest of North America. Fecal samples taken within 48 h of admission were positive for larvae in 70% (21/30) of individuals and in all five group samples taken from an additional 14 raccoons. Typically, Crenosoma spp. use an intermediate host, but the unweaned status of all the raccoons in this report suggests a potential direct, possibly vertical, route of transmission. Serial fecal analysis of pooled samples collected over several subsequent months demonstrated spontaneous resolution of larval shedding. Adult worms and gross evidence of pneumonia were detected in the lungs of several juvenile raccoons at necropsy, and verminous pneumonia was confirmed histologically in the single case submitted. Clinical signs directly attributable to verminous pneumonia were not seen in most actively shedding raccoons, suggesting that subclinical disease among juveniles may be common.

Transmission and Predictors of Burden of Lungworms of the Striped Dolphin (Stenella coeruleoalba) in the Western Mediterranean.

Pseudaliid lungworms infect the lungs and sinuses of cetaceans. Information on the life cycle and epidemiology of pseudaliids is very scarce and mostly concerns species that infect coastal or inshore cetaceans. Available evidence indicates that some pseudaliids are vertically transmitted to the host, whereas others are acquired via infected prey. We documented pseudaliid infections in an oceanic cetacean, the striped dolphin (Stenella coeruleoalba) in the western Mediterranean, and investigated the possibilities of vertical vs. horizontal transmission and the potential influence of host body size, sex, and season on infection levels. We found two species of lungworm in 87 dolphins that stranded along the Spanish Mediterranean coast between 1987 and 2018. One or two larvae of Stenurus ovatus were found in three adult dolphins. Larger numbers of larvae and adults of Skrjabinalius guevarai were collected in 51 dolphins, including unweaned calves. These observations suggested that Skrjabinalius guevarai could be vertically transmitted. The abundance of Skrjabinalius guevarai increased significantly with host size, which suggested that it could be trophically transmitted, as well, with larger hosts consuming more infected prey. Infection levels peaked in spring, outside of the calving season, which is likely a reflection of a seasonal shift in dolphin diet. In summary, results indicate that Skrjabinalius guevarai was capable of both vertical and horizontal transmission, but future research should be directed at clarifying the potential mechanics behind transmission and intermediate hosts.