Hymenolepis diminuta infection in a school-going child: A rare case report

Abstract

Hymenolepis diminuta (H. diminuta) is a common parasite of rats and mice. It is very rare among humans. The life cycle of this parasite is completed in two hosts. Human beings are accidentally infected due to ingestion of infected fleas. Most of the time human infections are asymptomatic. We report a case of Hymenolepis diminuta infection in a school-going 10-year-old girl from a coastal village in south Tamil Nadu. Demonstration of H. diminuta eggs in the stool is the important diagnostic tool. Absence of polar filaments confirms the Hymenolepis diminuta. Praziquantal is the drug of choice.

Implications for Practice:

1. What is known about this subject?

   Children are accidental hosts of Hymenolepis diminuta. It is very rare among human beings. We found only a few cases reported from countries like Australia, the United States, Italy, Spain, Jamaica, Thailand, and Indonesia.

2. What new information is offered in this study?

   Though it is very rare among humans, our hope is that our study will act as an important stimulus to initiate more community studies like this in the future, especially in a developing country like India.

3. What are the implications for research, policy, or practice?

   Because of its rare incidence, this case of H. diminuta has implications for public health. As a preventive measure, eating contaminated grains and cereals needs to be avoided. With proper inspection of grains, cereals, and rodent control measures, along with proper sanitation and personal hygiene, these parasitic infections can be prevented without morbidity.

Background

Hymenolepis diminuta (H. diminuta) is primarily a rodent parasite called rat tapeworm. Though it is present worldwide, very few cases have been reported and only from specific countries.^1,2 Hymenolepis diminuta infestation is most common among children.³ Most reported cases were asymptomatic. Common symptoms were mild diarrhea, abdominal pain, and vague gastrointestinal manifestations. Diagnosis is usually made by demonstration of eggs in the feces by microscopy.^{1, 2,3}

Case details

A 10-year-old female presented to our clinic with a history of intermittent abdominal pain with loss of appetite. On examination, the child weighed 25kg and was 134cm in height, with mild pallor but no icterus. Her abdomen was soft with no organomegaly. Cardiovascular, respiratory, and central nervous systems were found to be normal. Her routine blood investigations were within normal limits except for eosinophilia, which is seen in parasitic infestations.

From the child’s stool sample, we identified a spherical, thick-shelled, yellow coloured egg measuring 70μm in diameter, with six central hooklets without any polar filaments (Figure 1). We asked for two consecutive stool samples after a week. These stool samples also showed similar morphology of eggs. Thus, we finally diagnosed the child with Hymenolepis diminuta infestation. The absence of polar filaments is an important finding that differentiates this parasitic egg from Hymenolepis nana egg, which measures 30–45μm in diameter, with four to eight polar filaments emanating from little knobs at either end of the embryophore.²

Figure 1. Hymenolepis diminuta egg from a school-going child’s stool sample (under 40X magnification).

All the stool samples were processed by formal-ether concentration method by Ritchie.^1,2 Samples were screened by both saline and iodine wet-mount preparations in a systematic manner.

The tablet Cysticide (Praziquantal) was prescribed. The patient tolerated the medication well without any adverse drug reactions. Following drug therapy, after 15 days two consecutive stool samples were received and subjected to microscopic examination. Both were found to be negative for ova and cysts. Screening for the siblings was also performed; these also showed no ova and no cysts. Health education regarding proper personal hygiene and sanitation was given to the family members as a preventive measure.

Discussion

Hymenolepis diminuta is rare in humans. It is more prevalent worldwide among rodents.⁴ Humans, usually children, are accidental hosts by ingestion of an infected intermediate host. Countries such as Australia, the United States, Spain, Italy, Malaysia, Thailand, Jamaica, and Indonesia have reported cases of H. diminuta infection.^{5– 10}Reports from different populations have shown an incidence of 0.001–5.5 per cent H. diminuta parasitism.^11,12 In a study by Chandler with 10,000 stool samples, 23 cases were reported.¹³ Aside from those cases, only a few cases in India have been documented.^4,13–16 Foods such as grains and cereals contaminated with infected insects are the chief sources of infection.² Live beetle ingestion in Southeast Asia, especially in China, is an interesting mode of transmission of H. diminuta. In our case there was strong evidence of rats and insects dwelling around the residential area, therefore the source could have been the rats defecating at the larval stage.

Cockroaches, beetles, various species of fleas, and other arthropods are the intermediate hosts. Rats and mice act as the most common definitive hosts. The definitive hosts get infected by ingesting the intermediate hosts with cysticercoids, and thus adult worms develop in the small intestines of the definitive host where eggs are laid. Eggs are infective to man. The adult worm measures about 20–60cm in length. The scolex has four suckers and an unarmed rostellum. The strobila contains 800 to 1,000 proglottids. Mature proglottids contain an ovary at the centre and one testis on each side. The demonstration of H. diminuta eggs in the stool is the primary diagnostic tool.^1–3 Most of the time this condition may be asymptomatic, but vague abdominal pain, extra intestinal manifestations like pruritus, irritation, and eosinophilia may be present.¹⁷ This child only had eosinophilia. Praziquantal is the drug of choice (15–25mg/kg single dose preferably in the morning). This is much simpler compared to five days treatment needed with niclosamide for eradication of Hymenolepis species parasitic infection.

Conclusion

We report this rare case of Hymenolepis diminuta infection due to its rare incidence in humans and its relevance to public health. As a preventive measure, eating contaminated grains and cereals needs to be avoided. With proper inspection of grains, cereals, and rodent control measures, along with proper sanitation and personal hygiene, these parasitic infections can be prevented without morbidity.