Locally acquired infection with Dibothriocephalus nihonkaiense (=Diphyllobothrium nihonkaiense) in France: the importance of molecular diagnosis.

Diphyllobothriasis is a parasitic fish-borne disease caused by tapeworms of the genus Dibothriocephalus (=Diphyllobothrium). The majority of reported cases are attributed to D. latum, based on morphological identification of eggs or proglottids. However, numerous reports in recent years suggested that other Dibothriocephalus species could be involved in human infections, mainly after consumption of salmonid fish. Among these, D. nihonkaiense has been predominantly reported from Eastern Asia and probably underestimated in the rest of the world. We report here a clinical case of D. nihonkaiense in a French patient (without history of travel abroad) after consumption of salmon. Suspected on morphological characteristics, the final identification of D. nihonkaiense was performed using molecular methods by sequencing nad1, cox1, and 5.8S rRNA (containing ITS1 and 2) genes sequences. The patient was successfully treated by a single dose of praziquantel. Reports of diphyllobothriasis due to D. nihonkaiense are rare outside Asia, but worldwide demand of seafood could lead to the globalization of cases and reflect the need to monitor the distribution of Dibothriocephalus species. Thus, clinical parasitologists should be aware of this risk and able to raise the possibility of infections by non-endemic Dibothriocephalus species in order to use the proper molecular tools.

Diphyllobothriasis in a U.S. Military Aviator.

BACKGROUND: Diphyllobothriasis is estimated to afflict 10-20 million people worldwide; however, this is the first case reported in a United States military aviator. Among the largest parasites of humans, the "fish tapeworm" grows from 2-15 m in length, can live >20 yr in the intestines, and is contracted through consumption of uncooked, unfrozen freshwater or anadromous fish species. CASE REPORT: A 32-yr-old male F-22 pilot presented with mild stomach cramping, bloating, nausea, and intermittent loose stools. Symptoms were relieved with bismuth subsalicylate until several days later when the patient, during otherwise normal bowel movements, extracted multiple broken segments of tapeworm. Although physically asymptomatic, he was psychologically disturbed. Based on the large number of ova with characteristic shape, size, color, and operculum, coupled with the flattened body, yellowish coloration, and rectangular proglottids with centrally located "rosette" uteri, he was diagnosed with diphyllobothriasis (likely D. latum or D. nihonkaiense). Successful treatment with a single oral dose of praziquantel (>10 mg · kg-1) was confirmed by negative stool examination over 60 d posttreatment. He likely contracted the parasite from ingesting salmon sushi or sashimi while previously stationed in Japan. DISCUSSION: Despite only mild physical symptoms, the pilot's psychological distress and distraction from knowing about the meters-long tapeworm was significant. Prompt treatment was paramount to resumption of military operations. Aviators should be educated and encouraged to eat only well-cooked or previously frozen fish, especially when indulging in cultural cuisine.Kasteler SD. Diphyllobothriasis in a U.S. military aviator. Aerosp Med Hum Perform. 2018; 89(5):473-477.

Four Human Cases of Diphyllobothrium nihonkaiense (Eucestoda: Diphyllobothriidae) in China with a Brief Review of Chinese Cases.

We described 4 human infection cases of zoonotic fish-tapeworm, Diphyllobothrium nihonkaiense, identified with morphological and molecular characters and briefly reviewed Chinese cases in consideration of it as an emerging parasitic disease in China. The scolex and mature and gravid proglottids of some cases were seen, a rosette-shaped uterus was observed in the middle of the mature and gravid proglottids, and the diphyllobothriid eggs were yellowish-brown in color and displayed a small knob or abopercular protuberance on the opposite end of a lid-like opening. The average size of the eggs was recorded as 62-67×42-45 µm. The parasitic materials gathered from 4 human cases were morphologically identified as belonging to the genera Diphyllobothrium and Adenocephalus. The phylogenetic analysis based on the nucleotide sequences of cytochrome c oxidase subunit 1 gene of the etiologic agents confirmed that the 4 cases were D. nihonkaiense infection. The finding of 4 additional D. nihonkaiense cases suggests that D. nihonkaiense might be a major causative species of human diphyllobothriasis in China. A combined morphological and molecular analysis is the main method to confirm D. nihonkaiense infection.

Eggs as a Suitable Tool for Species Diagnosis of Causative Agents of Human Diphyllobothriosis (Cestoda).

BACKGROUND: Tapeworms of the order Diphyllobothriidea are parasites of tetrapods and several species may infect man and cause neglected human disease called diphyllobothriosis. Identification of human-infecting diphyllobothriid cestodes is difficult because of their morphological uniformity, which concerns also their eggs in stool samples. METHODS: In the present study, we analysed by far the largest dataset of more than 2,000 eggs of 8 species of diphyllobothriid cestodes that may infect humans, including the most frequent human parasites Diphyllobothrium latum, D. nihonkaiense and Adenocephalus pacificus (syn. Diphyllobothrium pacificum). Size (length, width and length/width ratio) and the surface of the egg shell from naturally and experimentally infected hosts were studied using light and scanning electron microscopy. RESULTS: A high degree of intraspecific and host-related size variability has been detected, but combination of morphometrical and ultrastructural data made it possible to distinguish all of the studied species, including otherwise quite similar eggs of the 3 most common species infecting man, i.e. D. latum, D. nihonkaiense and D. dendriticum. The surface of all marine species is covered by numerous deep pits with species-specific density, whereas the surface of freshwater species is smooth or with isolated shallow hollows or wrinkles.

Diphyllobothrium nihonkaiense infections in a family.

Diphyllobothrium latum and Diphyllobothrium nihonkaiense are morphologically similar to each other, and only genetic method can differentiate clearly between the 2 species. A strobila of diphyllobothriid tapeworm discharged from a 7-year-old boy was analyzed to identify the species by mitochondrial cytochrome c oxidase subunit 1 (cox1) gene sequencing. He and his family (total 4 persons) ate slices of 3 kinds of raw fish 16 days before visiting our outpatient clinic. All family members complained of abdominal pain and watery diarrhea. They all expelled tapeworm strobilae in their stools. They were treated with a single oral dose of praziquantel and then complained of no more symptoms. The cox1 gene sequencing of the strobila from the boy revealed 99.9% (687/688 bp) similarity with D. nihonkaiense and only 93.2% (641/688 bp) similarity with D. latum. Thus, we assigned this tapeworm as D. nihonkaiense. This is the first report of D. nihonkaiense infection in a family in Korea, and this report includes the 8th pediatric case in Korea. The current report is meaningful because D. nihonkaiense infection within a family is rare.

Two human cases of Diphyllobothrium nihonkaiense infection in Korea.

Diphyllobothrium latum and Diphyllobothrium nihonkaiense are the 2 reported main causes of human diphyllobothriasis in the Republic of Korea. However, the differentiation of these 2 species based on morphologic features alone is difficult. The authors used nucleotide sequencing of the mitochondrial cytochrome c oxidase subunit 1 (cox1) gene to diagnose Diphyllobothrium spp. Two patients visited the emergency room at Kyungpook National University Hospital on 3 April and 12 April 2013, respectively, with fragments of parasites found while defecating. The parasites were identified as Diphyllobothrium spp. based on morphologic characteristics, and subsequent cox1 gene sequencing showed 99.9% similarity (1,478/1,480 bp) with D. nihonkaiense. Our findings support the hypothesis that D. nihonkaiense is a dominant species in Korea.

Imported diphyllobothriasis in Switzerland: molecular methods to define a clinical case of Diphyllobothrium infection as Diphyllobothrium dendriticum, August 2010.

Following a first clinical case of infection by Diphyllobothrium dendriticum in Switzerland in 2006, we report a second case in the country. The species was identified by molecular methods. In the Swiss, French and Italian subalpine regions, human diphyllobothriasis has seen a comeback since the late 1980's, and Diphyllobothrium latum is usually considered the causative agent of the disease. In addition, several locally acquired and imported clinical infections due to allochthonous Diphyllobothrium species have been documented in the last years. Due to the colonisation potential of these parasites and their probably underestimated presence in the human population, there is a need for discriminating them at the medical laboratory level. Because the morphological characters are very similar among the different taxa, a correct identification requires the use of molecular methods. Molecular identification would improve diagnosis and help monitor the distribution of Diphyllobothrium species in Europe.

Four human cases of Diphyllobothrium latum infection.

Diphyllobothrium latum infections in 4 young Korean men detected from 2008 to 2012 are presented. Three were diagnosed based on spontaneously discharged strobila of the adult worm in their feces, and 1 case was diagnosed by finding the worm at colonoscopy examination in a local clinic. The morphologic characteristics of the gravid proglottid and eggs were consistent with D. latum. All patients were treated with praziquantel 15 mg/kg, and follow-up stool examinations were done at 2 months after the medication. The main clinical complaints were intermittent gastrointestinal troubles such as indigestion, abdominal distension, and spontaneous discharge of tapeworm's segments in their feces. The most probable source of infection was the flesh of salmon or trout according to a patient's past history. These are the 45th to 48th recorded cases diagnosed by the adult worm in the Republic of Korea since 1971.

Importancia de la difilobotriosis humana para el turismo / Significance of human diphyllobothriasis for tourism

La difilobotriosis es una infección parasitaria causada por cestodos del género Diphyllobothrium, cuyos adultos se desarrollan tanto en mamíferos como en aves. El hombre es también hospedero definitivo y los estadios juveniles se establecen en copépodos y peces teleósteos. En las zonas lacustres del sur argentino existen condiciones ecológicas propicias para la instalación de esta endemia. Durante el período 2002-2006 se atendieron en el Hospital de Enfermedades Infecciosas Francisco J. Muñiz de la Ciudad de Buenos Aires (Argentina) 6 casos con difilobotriosis humana, a los cuales se les realizo el diagnóstico epidemiológico, clínico y de laboratorio. Se efectuó el tratamiento antiparasitario específico y el seguimiento correspondiente postratamiento. Todos los casos evolucionaron favorablemente. La importancia de esta publicación reside en alertar a los agentes que trabajan en salud sobre la presencia de esta patología emergente en zonas patagónicas andinas y en pacientes que consumen pescado crudo o poco cocido, provenientes de esa zona. Se destaca la posibilidad de adquirir esta infección íctica por el consumo de ciertos platos de origen oriental, como el sushi y el sashimi, en otras zonas no endémicas.

Difilobotriosis humana: Un caso en área no endémica de la Argentina / Human diphyllobothriosis: A case in a non-endemic area of Argentina

La difilobotriosis es una parasitosis intestinal causada por la infección de cestodos del genero Diphyllobothrium. En la Argentina, la Patagonia Andina es considerada una zona endémica para esta parasitosis. La infección por Diphyllobothrium latum no ha sido previamente notificada en la provincia de Mendoza; en este trabajo comunicamos un caso de esta parasitosis que fue confirmada por el análisis de las características morfológicas de los huevos eliminados con la materia fecal de un paciente infectado. Se destaca la necesidad de información y capacitación de los profesionales de la salud en el diagnóstico y tratamiento de parasitosis no endémicas.

Diphyllobothriosis is an intestinal parasitosis caused by cestodes infection of the genus Diphyllobothrium. In Argentina, the Andean Patagonia is considered an endemic area for this parasitosis. Diphyllobothrium latum infection has not been previously reported in the province of Mendoza, Argentina. We are now reporting then the first case. Diphyllobothriosis was confirmed by examination of morphologic characteristics of the eggs eliminated in the patients' feces. These results suggest the requirement of a more specific training of health workers in the diagnosis and treatment of non endemic parasitosis. We want to emphasize the need of health workers' education on diagnosis and treatment of endemic and non-endemic parasitosis.