DOI: https://doi.org/10.21203/rs.3.rs-2036838/v1
Hymenolepis diminuta is a cosmopolitan parasite of rats and mice which is very rare in humans but has been reported from various areas of the world. We report a human case of Hymenolepis diminuta pulmonary infection in Giangsu Province, China and it has never been reported in patient’s Lung before. In the process of the diagnosis, NGS technology helps a lot. The infection was treated with albendazole and showed clinical and parasitological cure.
The zoonotic cestode Hymenolepis diminuta (H. diminuta) is primarily a rat tapeworm, found in the small intestine of rodents, which are the definitive hosts(1-3). H. diminuta infection in humans is rare, even in developing countries, typically occurring in isolated cases, such as case reports describing a single affected individual(1, 4). Human infection with H. diminuta most often occurs from accidental ingestion of stored-grain beetles(5) . Adult worms attach themselves to the mucosa of the small intestine of human, and it passes eggs in the stool of patient(6). H. diminuta infection is reported to be more common among children than adults(7). Infection is mainly asymptomatic, though rarely symptoms, such as itching, abdominal pain, and mild diarrhea, have been reported(6). The patient in our case is a 49 years old man and begins his illness by cough and asthma. To the best of our knowledge, this is the first documented case that the H. diminuta infection found primarily in human lung all over the world.
In May 2022, a 49-year-old male presented to our hospital (Suqian Hospital of Nanjing Drum Tower Hospital Group) with a history of repeating cough, expectoration, and asthma in recent months. In particular, some thin strips like noodles can be found in his sputum (Figure 1). On examination, the patient weighed 75kg and was 174cm in height, no abdominal pain, no vomiting, and no loss of appetite. Digestive system, cardiovascular, and central nervous systems were found to be normal. No other family member had similar complaints.
Chest CT shows lung shadows (Figure 2A), we considered the possibility of some kind of pathogen infection. We extracted the alveolar lavage fluid and did not find some conventional infection, then we did high-throughput sequencing, also known as Next-generation sequencing technology (NGS). The NGS result is Hymenolepis diminuta infection (Figure 3). Then, from the patient’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 4).
The tablet albendazole was prescribed of 400mg per day for 7days(5). The patient tolerated the medication well without any adverse drug reactions. Following drug therapy, after 15 days two consecutive stool and sputum samples were received and subjected to microscopic examination. Both were found to be negative for ova and cysts. Chest CT shows no shadows in the lung (Figure 2B).
H. diminuta has a ubiquitous distribution worldwide, however, it is rarely found in humans(8). The definitive host as well as natural reservoirs of H. diminuta are rodents, i.e., rats and mice(9). Children and adults from poor socioeconomic group are more prone to infection because of unhygienic practices(10). The demonstration of H. diminuta eggs in the stool is the essential diagnostic tool. Most of the time this condition may be asymptomatic; however, vague abdominal pain and extraintestinal manifestations such as pruritus, irritation, and eosinophilia may be present(11). Given that most cases of H. diminuta infection have been reported in children, it is most likely that children acquire the infection through the ingestion of insects, whereas infection in adults probably occurs via the incidental ingestion of food contami-nated with infected insects or the willing ingestion of edible insects, either as part of traditional practices or due to the increased demand for new food sources or exotic dishes. Further studies are needed to identify risk factors for human hymenolepiasis caused by H. diminuta(7).
Here, we have reported an uncommonly encountered parasite H. diminuta especially in a prime-age man. There are few cases of human infections have been reported from china. It was the first report of human pulmonary infection of H. diminuta, based on our knowledge. Majority of the cases are asymptomatic, and the prevalence of infection in the community may be underestimated. Our case begins illness by cough and asthma. This case atypically presented as respiratory symptom and, as far as we know, respiratory symptom has never been reported as a clinical feature of symptomatic H. diminuta infection. Therefore, more effort should be put into improving our knowledge of the epidemiology and transmission routes of this uncommon human infection(12).
What’s more, we make a definite diagnosis for this case by extracting the alveolar lavage fluid through NGS. Due to the atypically present：age, area, and other atypical factors. We do not associate the case with parasitization. But NGS technology helps us make a definite diagnosis rapidly, with no delay and avoid misdiagnoses. It suggests that new technology can often surprise you in a big way.
Ethical Approval
The enrolled patient has been explained in detail about the study and signed informed consent.
Competing interests
The authors declare no conflict of interest.
Authors' contributions
Jingjie Liu and Kang Tian wrote the main manuscript text and Jingjie Liu,Kang Tian and Wangyuan Sun prepared figures. All authors reviewed the manuscript.
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