A critical review of anisakidosis cases occurring globally

Abstract

A review was conducted to identify the most common causative agents of anisakidosis, the methods used for identification of the causative agents, and to summarize the sources of infection, and patients' demographics. A total of 762 cases (409 articles, inclusive of all languages) were found between 1965 and 2022. The age range was 7 months to 85 years old. Out of the 34 countries, Japan, Spain, and South Korea stood out with the highest number of published human cases of anisakidosis, respectively. This raises the question: Why are there few to no reports of anisakidosis cases in other countries, such as Indonesia and Vietnam, where seafood consumption is notably high? Other than the gastrointestinal tract, parasites were frequently found in internal organs such as liver, spleen, pancreas, lung, hiatal and epigastric hernia, and tonsils. There are also reports of the worm being excreted through the nose, rectum, and mouth. Symptoms included sore throat, tumor, bleeding, gastric/epigastric/abdominal/substernal/lower back/testicular pain, nausea, anorexia, vomiting, diarrhea, constipation, intestinal obstruction, intussusception, blood in feces, hematochezia, anemia, and respiratory arrest. These appeared either immediately or up to 2 months after consuming raw/undercooked seafood and lasting up to 10 years. Anisakidosis commonly mimicked symptoms of cancer, pancreatitis, type I/II Kounis syndrome, intussusception, Crohn's disease, ovarian cysts, intestinal endometriosis, epigastralgia, gastritis, gastroesophageal reflux disease, hernia, intestinal obstruction, peritonitis, and appendicitis. In these cases, it was only after surgery that it was found these symptoms/conditions were caused by anisakids. A range of not only mainly marine but also freshwater fish/shellfish were reported as source of infection. There were several reports of infection with >1 nematode (up to >200), more than one species of anisakids in the same patient, and the presence of L4/adult nematodes. The severity of symptoms did not relate to the number of parasites. The number of anisakidosis cases is grossly underestimated globally. Using erroneous taxonomic terms, assumptions, and identifying the parasite as Anisakis (based solely on the Y-shaped lateral cord in crossed section of the parasite) are still common. The Y-shaped lateral cord is not unique to Anisakis spp. Acquiring a history of ingesting raw/undercooked fish/seafood can be a clue to the diagnosis of the condition. This review emphasizes the following key points: insufficient awareness of fish parasites among medical professionals, seafood handlers, and policy makers; limited availability of effective diagnostic methodologies; and inadequate clinical information for optimizing the management of anisakidosis in numerous regions worldwide.

Keywords: Anisakiasis; Anisakidosis; Anisakiosis; Foodborne parasites; Misdiagnosis; Nematoda; Seafood safety.

Fig. 1

The literature search through this study

Fig. 2

Diagrams summarizing the demographic data found in the present study. A Number of reports of anisakidosis cases in different years. B Number of reported of anisakidosis cases in different age ranges. C Percentage of females and males found to be infected with anisakid nematodes during the study period. D and E Number and distribution of anisakidosis cases in different countries. The country in which the disease was diagnosed was considered the place of the occurrence of anisakidosis, including a case of a Japanese man visiting the USA and travelers who recently returned from Brazil and Portugal

Fig. 3

Diagrams summarizing the data found in the present study. In panel A, transient includes reports of the live parasite exiting human body. This included when it was reported in the sputum, feces, diaper, nose, and mouth and one case where the worm was reported to exit from the skin around neck; extra gastrointestinal includes mesentery, liver, spleen, pancreas, lung, lymph nodes, scrotum, uterus, ovary, glands around anus, found in dialysis affluent, found in a nodule on the large omentum and amyand, hiatal and epigastric hernia; one case of polyarthritis caused by anisakid nematode was also placed under gastrointestinal; and oropharynx includes larynx, tonsil, tongue, and throat. Appendicitis cases were considered under small intestine. Mixed organ infection included stomach and colon (n = 1), stomach and small intestine (n = 8), stomach and colon (n = 3), and stomach and esophagus (n = 1). Panel B shows the number of anisakid larvae found in infected people. Panel C shows the frequency of various developmental stages of anisakid larvae found in infected people. In panel D, anisakids includes reports as anisakids, Anisakidae, Anisakine type, Anisakis like larva, and two cases where authors were not sure between Anisakis or Pseudoterranova and Pseudoterranova or Contracecum. Anisakis sp. includes reports in which parasite referred as Anisakis sp., and Anisakis; A. simplex includes reports of A. simplex, A. simplex sensu lato, and A. simplex sensu stricto; Pseudoterranova decipiens includes Phocanema decipiens, Pseudoterranova decipiens sensu stricto, and Pseudoterranova decipiens sensu lato