The potential threat at the dining table: Taenia saginata

Abstract

Taeniasis, a foodborne parasitic disease, is characterized by infection via Cysticercus bovis in raw or undercooked beef and is traditionally prevalent in regions and populations with dietary habits favoring raw or undercooked beef consumption. Here, we reported four cases of Taenia saginata infection identified in Hunan Province, a non-endemic region for T. saginata in 2023 and 2025. Morphological analysis of gravid proglottids was performed using an improved potassium permanganate staining protocol, and species identity was confirmed by PCR and sequencing. All patients had consumed raw or undercooked beef in mid-to-high-end restaurants, including healthcare workers. Notably, household clustering was observed. This report highlights the necessity of enhancing dietary safety education, reinforcing parasitic inspection of meat, and warning the public about the health risks of consuming raw or undercooked beef.

1. Introduction

Taenia saginata, also known as the beef tapeworm, has humans as its sole definitive host and primarily relies on bovids as intermediate hosts. Infection typically occurs through undercooked beef, often with mild or no symptoms (Webb and Cabada, 2017; Tembo and Craig, 2015). The primary route of T. saginata transmission is the consumption of raw or insufficiently cooked infected beef containing cysticercus bovis. Severe cases may cause abdominal discomfort, digestive issues, and intestinal obstruction.

Taeniasis is distributed worldwide, with its prevalence influenced by geographical environment, climatic conditions, dietary habits, cultural customs, and other factors (Braae et al., 2018; Saratsis et al., 2019; Torgerson et al., 2019). Globally, an estimated 60–70 million people are infected with T. saginata. According to the China third national survey on the prevalence of human parasitic diseases, the national tapeworm infection rate stands at 0.36%, with Tibet having the highest rate at 9.25%, followed by Sichuan at 0.48%; while Hunan Province has a rate of only 0.01% (Yang and Tian, 2019; Ying-dan et al., 2020). This indicates that Hunan is not a primary endemic area for tapeworm infection. With socioeconomic development, contemporary patterns of T. saginata transmission may be linked to consumers' preference for raw/undercooked beef, alongside modern cold-chain logistics that distribute meat (Dbouk et al., 2021). Consequently, infections were being reported in urban centers. The study reported four confirmed cases of T. saginata infection in Hunan Province (2023–2025) and underscores the importance of public dietary health education and the monitoring of foodborne pathways.

2. Case presentation

2.1. Patient profile

Case 1

A 56-year-old man from Hunan had consumed beef hotpot multiple times. He experienced chronic constipation and an unintentional 6-kg weight loss from January to June 2023, when he first observed milky-white proglottids in his stool. Self-treatment with albendazole was followed by recurrence in November, leading to hospitalization. Stool examination confirmed tapeworm eggs. Deworming with pumpkin seeds and betel nuts resulted in expulsion of an intact ~193 cm adult worm (Fig. 1A) and its scolex (Fig. 1D).

Case 2

A 31-year-old man from Changsha had also consumed beef hotpot repeatedly in 2023. He presented in December 2023 after noticing proglottids in his stool but had no other symptoms. The same deworming regimen (with Case 1) successfully expelled tapeworm segments (Fig. 1E).

Case 3

A 39-year-old female healthcare worker consumed raw beef sashimi in November 2024. In January 2025, she developed vomiting and abdominal pain, initially diagnosed as gastroenteritis. Readmitted in March 2025, the results of routine blood tests indicate significant peripheral blood eosinophilia at 18.5% (reference range: 0.4–8%). Following praziquantel treatment, partial proglottids were expelled 12 h later (Fig. 1B), but no scolex was recovered.

Case 4

A male healthcare worker shared the same raw beef sashimi meal as Case 3. He reported intermittent nausea and diarrhea starting January 2025 and was admitted in March. Laboratory findings revealed severe peripheral blood eosinophilia at 33.8% (reference range: 0.4–8%). After praziquantel administration, partial segments were expelled 24 h later (Fig. 1C), with no scolex recovered.

Fig. 1.

Morphological identification of T. saginata. (A) The complete T. saginata. Expelled from Case 1 (approx. 193 cm). (B) A partial T. saginata expelled from Case 3 (approx. 134 cm). (C) A partial T. saginata expelled from Case 4 (approx. 230 cm). (D) The scolex (E) Gravid proglottid. (F) T. saginata eggs.

2.2. Clinical diagnosis

2.2.1. Treatment

Following the initial clinical assessment, the four cases received deworming treatment using two different therapeutic approaches. In Case 1, Case 2, a traditional Chinese medicine treatment methods of pumpkin seeds and betel nuts was administered (Li et al., 2012; Zhang et al., 2019). Patients followed a light diet the preceding day. The next morning, after fasting, they consumed 150 g of raw pumpkin seeds orally. Forty minutes later, they ingested 200 mL of a betel nut decoction (120 g of betel nuts boiled in 1000 mL of water). Thirty minutes thereafter, 250 mL of mannitol was administered orally as a purgative, followed 30 min later by 500 mL of normal saline to stimulate gastrointestinal motility. Patients were encouraged to perform moderate physical activity to aid parasite expulsion. In Case 3, Case 4, both patients received oral praziquantel at a dosage of 20 mg/kg, three times daily. Partial tapeworm segments were expelled within 12–24 h post-administration. Follow-up confirmed no further parasite expulsion and resolution of symptoms, indicating effective treatment.

2.2.2. Morphological examination

Stool specimens were collected from all patients. Eggs were concentrated using the washing sedimentation method and examined by microscopy. In Case 1, a complete T. saginata strobila (~193 cm) was recovered (Fig. 1A). The parasite was thick, opaque, and ribbon-like. Its quadrate scolex featured four suckers and lacked a rostellum or hooklets, consistent with morphological characteristics of T. saginata (Fig. 1D). Partial strobilae from Case 2, Case 3, Case 4 measured approximately 150 cm, 134 cm (Fig. 1B), and 230 cm (Fig. 1C). No scolex was recovered from Case 2; thus, gravid proglottids were pressed between slides, dehydrated through ethanol, treated with halotrichite, and washed. Specimens were stained using potassium permanganate (5 min) and differentiated with acetic acid (2 min). Microscopy revealed neatly arranged uterine branches (~25 per side), falling within the 15–30 range diagnostic for T.saginata (Fig. 1E). Brownish-yellow eggs contained oncospheres displaying three hooklet pairs (Fig. 1F), further confirming the diagnosis.

2.2.3. Molecular identification

To validate species identity, genomic DNA was extracted from proglottids. The mitochondrial cox1 was amplified, yielding a ~ 480 bp product. (Liu et al., 2025) The PCR protocol included initial denaturation (94 °C, 5 min), 35 cycles (94/60/72 °C for 30 s), and final extension (72 °C, 5 min). Amplicons(GenBank: PZ151410) were sequenced and aligned via NCBI BLAST. Maximum-likelihood phylogenetic tree (bootstrap = 1000) based on the cox1 gene. After midpoint rooting, Taenia asiatica and T. saginata formed distinct lineages. The isolate PZ151410 was clustered within the T. saginata clade, and was most closely related to OR143747 (T.S-Vietnam), then grouped with MN044594 (T.S-Qinghai) and MN337881 (T.S-Slovakia) into a small subclade (Fig. 2). These results confirmed the pathogen as T. saginata.

Fig. 2.

The phylogenetic tree constructed based on T. saginata cox1 sequences.

According to the WHO diagnostic criteria, confirmation is achieved by the detection of T. saginata eggs or proglottids in faecal samples collected over multiple days (World Health Organization, 2022). On this basis, the four cases can be diagnosed as taeniasis caused by T. saginata.

3. Discussion

Th dietary habits of consuming raw or undercooked beef significantly elevates the risk of T. saginata infection. Patients in this study had consumed raw or undercooked beef in mid-to-high-end restaurants, including healthcare workers. In recent years, there has been a growing public preference for fresh-tasting food, which has boosted the popularity of beef hotpot and beef sashimi. Beef hotpot often involves thin slices cooked briefly in hot broth, which may not fully inactivate T. saginata cysticerci. Beef sashimi consists of uncooked beef, presenting an even higher risk of infection. These dietary practices greatly increase the risk of infection.

A major factor contributing to these infections, which is often ignored, was the common belief that traditional condiments—specifically alcohol, vinegar, or mustard—effectively sterilize raw meat. Contrary to the common belief that these additives provide a “chemical cooking” effect, C. bovis (the larval stage) showed shows a strong survival ability in response to this mild intervention. Common condiments such as wine and vinegar cannot effectively kill parasites (Zhang Ke et al., 2018; Shin et al., 2004). This practice further reduces the exposure time to lethal temperatures, thereby elevating the risk of infection. The pumpkin seeds and betel nuts deworming method is more conducive to the complete expulsion of the worm body. During deworming, locating the scolex is crucial to prevent future recurrence. Species identification was performed by morphological examination of uterine branches in gravid proglottids or PCR (Eom et al., 2020). Although morphological identification is cost-effective and suitable for rapid screening, it has limited sensitivity and subjectivity. Molecular methods such as PCR offer higher sensitivity and specificity (González et al., 2000). In this study, we combined morphological and molecular biological methods for diagnosis. Specifically, the phylogenetic tree based on the cox1 marker showed that PZ151410 consistently clustered within the T. saginata lineage, confirming its classification as T. saginata.

Prevention depends on source management and education. Future strategies must strengthen meat inspection to intercept infected cattle before they enter the market and raising public awareness of this disease. Clinicians should also integrate detailed dietary history inquiries to identify potential foodborne exposure, ensuring timely diagnosis and treatment.

This study has several limitations. First, it is based on four T. saginata cases from a single region, and the relatively small sample size limits the representativeness of the observed clinical and epidemiological features. Second, despite accurate molecular identification of the parasite, we did not conduct detailed traceability of the contaminated beef, which prevents clarification of the infection sources and transmission chains. Third, only the mitochondrial cox1 gene was employed for molecular identification and phylogenetic analysis. This locus exhibits low resolution for fine-scale phylogeographic differentiation, and the length of the amplified fragment may further constrain its capacity to discriminate intraspecific genetic variation. Future research should expand the sample size, conduct multi-center studies, perform systematic beef source traceability, follow up patients long-term and analyze risk factors to provide more comprehensive evidence for the clinical management and prevention of T. saginata infection.

CRediT authorship contribution statement

Yaqi Zhu: Writing – original draft, Investigation, Data curation. Zhuolin Li: Writing – original draft, Methodology, Data curation. Ni Zhang: Software. Xinglv Wang: Data curation. Xingxing Zheng: Conceptualization. Xiaolei Long: Conceptualization. Pengfei Cai: Writing – review & editing. Hong You: Writing – review & editing. Shuaiqin Huang: Data curation. Bin Tian: Data curation. Mao Zheng: Writing – review & editing. Xiang Wu: Writing – review & editing, Funding acquisition, Data curation, Conceptualization.

Ethical approval

Informed consent was obtained from all patients.

Funding

This study was supported by the National Key Research and Development Program of China (No. 2022YFC2304001 to X W), National Natural Science Foundation of China (No. 32370197 to X W). Open Research Project of the Regional Collaboration Centre for Schistosomiasis Control Technology in Lake Regions for the Year 2025–2026 (No. 20251001 to X W); Health Research Project of Hunan Provincial Health Commission (No. 20255023 to M Z); Hunan Provincial Natural Science Foundation (No. 2023JJ60290 to XL L); Scientific Research Plan of Hunan Provincial Health Commission (No. D202301056666 to XL L).

Declaration of competing interest

The authors declare no competing interests.

Data availability

The sequence is available in the NCBI database under accession PZ151410.