Case Report - (2021) Volume 9, Issue 7
Hymenolepis diminuta is a zoonotic cestode infrequently found in humans, with less than 1600 cases reported worldwide. Infection is acquired by accidental ingestion of arthropods containing the larval stage of the parasite in their body cavity. We present two clinical cases of pediatric patients attending the “Prof. Dr. Juan P. Garrahan” Pediatric Hospital, in whose coproparasitological examinations were found Hymenolepis diminuta eggs. Due to the rare finding and little knowledge of its epidemiology, the report of this infection becomes of great interest.
Enteroparasite; Hymenolepis diminuta; Pediatric patients
Hymenolepis diminuta is an unusual enteroparasite, with less than 1600 cases reported worldwide [1]. The infection is diagnosed more frequently in the pediatric population [2]. Rodents are the main definitive hosts and natural reservoir for the parasite and in rare instances it can infect humans by accidental ingestion of infected insects. Coprophilic arthropods act as intermediate hosts, acquiring the infection by ingesting infective eggs. The larval stage of the parasite (cysticercoid) develops inside the body cavity of the intermediate host within 15 to 20 days. The cycle fulfills when the definitive host eats infected arthropods. Cysticercoids are released in the small intestine, where they attach into the intestinal mucosa and mature into the adult worm. Finally, embrionated eggs are eliminated in feces. Grains and cereals contaminated with infected insects represent the main source of infection for humans. The worm burden is generally low, and the infection is often asymptomatic or oligosymptomatic, with non-specific abdominal symptoms. Eosinophilia and anemia have also been registered. The diagnosis is based on the recovery and identification of the characteristic eggs in stool examination [3].
We report two cases of Hymenolepis diminuta infection in pediatric patients from Buenos Aires, Argentina, who attended to the Epidemiology and Infectology Service of the "Prof. Dr. Juan P. Garrahan" Pediatric Hospital.
Patient 1. An 8-year-girl, consulted for presenting abdominal pain that worsened after ingestion, weight loss and nausea during the last three months. The patient was always afebrile, with preserved catharsis and normal diuresis. An abdominal ultrasound was performed, which showed no abnormalities. The only finding within the routine analysis was in the stool samples from the parasitological examination that revealed few H. diminuta eggs. Monodose of praziquantel was prescribed. A second coproparasitologic examination carried out 20 days after, demonstrated the absence of parasitic structures. The patient reported improvement in symptoms, without vomiting, presenting occasional epigastric pain and weight gained.
Patient 2. A 2 year and 4 months old boy, came for follow-up due to low weight for over a year. He had a history of peripheral eosinophilia and infection with intestinal parasites (Taenia spp and Enterobius vermicularis) and Toxocara spp. Among the studies requested at this center, an abdominal ultrasound without abnormalities was reported; positive serological results for Toxocara sp. and peripheral eosinophilia were confirmed with an eosinophil count of 6.09 × 103/mm3. In single and serial fecal samples, a regular amount of Hymenolepis diminuta eggs, Giardia duodenalis cysts, Dientamoeba fragilis trophozoites and Blastocystis spp were observed. Two cycles of mebendazol and one cycle of metronidazol were prescribed as antiparasitic treatment for the patient and his family. Patient follow-up was discontinued in this instance.
The fecal samples for the parasitological examinations were collected in buffered formalin (SAF) and concentrated with the Ritchie method. The eggs of H. diminuta were brownish and spherical with an approximate measure of 70 μm in diameter. They presented a thick outer membrane, a thin inner membrane, and three pairs of hooklets but no polar filaments within the oncosphere (Figure 1). The described morphology allowed the identification of H. diminuta eggs and the parasitological diagnosis.
Figure 1: A: H. diminuta egg measuring 70,241 µm in diameter, found in stool examination of Patient 1 (× 400 magnification). B: Double external membrane, absence of polar filaments within the oncosphere and three pairs of hooklets can be appreciated in this H. diminuta egg recovered from the coproparasitological examination of Patient 2 (× 400 magnifications).
We described two cases of H. diminuta parasitosis, a rare human infection. Prevalence in countries that reported human infection around the world varies from 0,002 to 8,222% [4-6]. In Latin America, epidemiological studies refer prevalence data ranging from 0.5% to 4% [7,8]. In the “Prof. Dr. Juan P. Garrahan” Pediatric Hospital we have reported the prevalence of intestinal parasites in fecal samples from patients attended during the year 2019, with a 0.05% result for Hymenolepis diminuta [9].
The intensity level of the infection is related to the number of adult worms in the intestines. In humans, the worm burden is frequently low, and the infection is usually asymptomatic, although it may present mild symptoms, such as the case of patient number 1. It may cause moderate peripheral eosinophilia in 6 to 20% of cases. A causal relationship between clinical aspects of patient number 2 and Hymenolepis diminuta infection cannot be established, due to coinfection with other parasites in this patient.
The diagnosis of H. diminuta infections in humans most often is performed by finding eggs in fecal samples, and rarely by the presence of the adult worm or its proglottids in fecal specimens, which require an experienced and trained observer to identify these parasite structures. The absence of polar filaments, the bigger size and the brownish color are specific features of Hymenolepis diminuta eggs that allow their recognition and differentiate them from Hymenolepis nana eggs that appear more frequently in parasitological examinations.
The drug of choice for the treatment of Hymenolepis diminuta infection is praziquantel in single dose. In patient number 1 clinical improvement was achieved with coproparasitological examination with no detected H. diminuta eggs after the completion of the treatment [10-12].
H. diminuta infection has been related with basic services deficiencies and close contact with rodents. Individuals who are particularly vulnerable to this infection include children, rural areas inhabitants, and people living under overcrowding conditions and with poor sanitary facilities. It would be of great importance, in terms of prevention measures, to eradicate rodents and arthropods from housing and shops, where they can become in contact with food. There are over 20 species of insects susceptible to infection, such as rodent’s fleas, moths, flour weevils, cockroaches and various beetles. The accidental ingestion of cereals or grains contaminated with infected insects is usually the source of human infection.
Due to the low worldwide incidence of H. diminuta infection, and the unawareness of its epidemiology, it has become of great interest to report this parasitosis.
Citation: Ferioli S, Perazzo JM, Louzao EAC, Paulin P (2021) Infection by Hymenolepis diminuta in Pediatric Patients from Gran Buenos Aires, Argentina. Gen Med (Los Angeles). 9:349.
Received: 07-Jul-2021 Published: 29-Jul-2021, DOI: 10.35248/2327-5146.21.9.349
Copyright: © 2021 Ferioli S, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
