This scoping review aimed to systematically identify the risk factors and clinical management practices associated with anisakidosis, with the goal of informing better diagnostic awareness and patient care. Our findings show a consistent increase in reported anisakidosis cases since 2000, with a notable decline during the COVID-19 pandemic period (2020–2023) [27]. However, with the easing of pandemic-related restrictions and the global resurgence in raw seafood consumption, incidence is expected to rise again [28]. These projections highlight the ongoing need for vigilance and preparedness in addressing this parasitic disease.

Historically, over 90% of anisakidosis cases were believed to occur in Japan [18]. While Japan still reports the highest number of cases globally, significant numbers have also emerged in Italy, Korea, and Spain. Moreover, countries where the disease had not previously been reported, such as Colombia, Poland, and South Korea, have recently documented new cases [23, 29, 30]. This expanding distribution can be attributed to multiple factors, including the global popularity of Japanese cuisine featuring raw or undercooked seafood [28] and the shifting distribution of anisakid nematodes due to climate change [31].

Our findings, consistent with previous global reviews [2], confirm that the highest incidence of anisakidosis is concentrated in Japan, Italy, and Korea. Interestingly, several countries within the same regions, such as Turkey, Greece, China, Taiwan, Vietnam, Thailand, and the Philippines, report surprisingly low case numbers despite documented evidence of anisakid-infected fish in local waters [32]. This disparity suggests a high likelihood of underdiagnosis or misdiagnosis in these regions. Limited clinical awareness, lack of routine diagnostic testing, and variable access to healthcare services may all contribute to underreporting. Notably, countries like Japan, Korea, Italy, and Spain benefit from universal healthcare systems, potentially facilitating diagnosis and reporting. In contrast, many Southeast Asian nations lack such infrastructure, which may result in reduced healthcare-seeking behaviour and, subsequently, fewer diagnosed cases [33]. Overall, this review reinforces that individuals in East Asia and the Mediterranean are currently at higher risk of anisakidosis.

Patient Characteristics

The analysis revealed distinct demographic patterns. A higher incidence was observed among males and in the 40–59 age group [19, 34,35,36,37]. These trends may reflect behavioural factors such as more frequent consumption of raw seafood, often in social settings involving alcohol—an association supported by previous studies [2]. However, our ability to explore these links in depth was limited by incomplete social history data across the included studies. Future research should prioritise the systematic collection of social and behavioural data to better understand the drivers of infection risk. Nonetheless, the current findings suggest that targeted health messaging and preventive strategies should focus on middle-aged populations, particularly men, who appear to represent a high-risk demographic for Anisakis infection.

Symptoms and Physical Examination Findings Associated with Anisakidosis

Anisakidosis presents with a wide spectrum of clinical symptoms, many of which mimic other abdominal pathologies such as bowel obstruction, intussusception, appendicitis, diverticulitis, and malignancy [12]. Commonly reported symptoms include abdominal tenderness and nausea or vomiting, which frequently prompt further investigation.

Notably, symptoms typically associated with bowel obstruction and gastrointestinal cancers, such as obstipation, abdominal distention, haematochezia, weight loss, and constipation, were less commonly reported in anisakidosis cases. Most patients presented with zero to two symptoms, suggesting a predominantly localised response. This is likely due to the tendency of anisakid larvae to embed within the gastric mucosa, triggering symptoms confined to the upper gastrointestinal tract, such as localised pain and nausea [17].

Abdominal tenderness emerged as the most frequently reported physical examination finding. Among specific patterns, epigastric tenderness was commonly noted, followed by rebound tenderness [38,39,40]. These findings may reflect the anatomical site of larval penetration, as epigastric tenderness is often associated with gastric anisakidosis [38,39,40]. However, epigastric discomfort has also been reported in patients with intestinal or peritoneal anisakidosis, suggesting that symptom localisation alone may not be diagnostic [41, 42]. Unfortunately, the number of studies documenting detailed physical examination findings remains limited. Further research is needed to elucidate the diagnostic value of physical signs in identifying the site and severity of anisakid infection.

Although symptoms often appear within the first 24 h of ingesting infected seafood [39], delayed presentation is common. Many patients sought medical care days or even weeks after symptom onset [43, 44], and in rare cases, several months later [45]. These findings underscore the importance of obtaining a thorough dietary history, even if seafood consumption occurred well before the onset of clinical symptoms.

Seafood Consumption Associated with Anisakidosis

The consumption of raw or undercooked fish is a well-established risk factor for anisakidosis [1, 3, 15, 17]. Among the various seafood types implicated, anchovies and mackerel were most frequently associated with infection. Anchovies are particularly popular in Mediterranean countries such as Italy and Spain, where they are often consumed marinated or lightly processed [46]. In contrast, mackerel, eel, and squid are dietary staples in several Asian countries, including Japan and Korea, where dishes such as sushi and sashimi are widely consumed [4, 47].

The regional variation in anisakidosis prevalence appears to reflect cultural dietary preferences. For example, although anchovies are favoured in countries like Spain, France, and Italy, and mackerel and squid are more commonly eaten in Japan and Korea, reported cases are comparatively lower in neighbouring countries such as Portugal and China. This discrepancy may be due to differences in food preparation practices, such as thorough cooking or freezing of seafood prior to consumption, or to underreporting and limited clinical recognition of the disease [2].

These findings underscore the importance of maintaining vigilance regarding the zoonotic risks posed by raw or undercooked seafood. Enhanced awareness of culturally specific consumption habits and local culinary practices can support more accurate surveillance and prevention efforts, especially in regions where the disease may be underdiagnosed.

Investigation

The most commonly reported diagnostic tools used by clinicians to investigate anisakidosis were endoscopy, blood tests, Anisakis-specific serology, and computed tomography (CT) scans. While specific blood test types were not always detailed, the serological data suggest frequent use of full blood count (FBC), electrolytes, urea and creatinine (EUC), liver function tests (LFT), and C-reactive protein (CRP). Among these, positive Anisakis serology was the most frequently reported finding, followed by leucocytosis and elevated CRP. However, these latter markers are nonspecific indicators of inflammation and do not offer high diagnostic specificity for anisakidosis [48, 49] and are not the best serological findings for patients with anisakidosis.

CT imaging findings in anisakidosis cases commonly included bowel wall thickening, ascites, and bowel dilation—features that are consistent with gastrointestinal inflammation or obstruction. These findings, particularly when observed in the small and large intestines, align with previous retrospective cohort studies [37]. While CT alone is not definitive, it can be a valuable adjunct when combined with serological testing, particularly for detecting intestinal anisakidosis where endoscopic access may be limited.

Together, these findings support the clinical utility of combining serological tests with imaging techniques to enhance diagnostic accuracy, especially in cases of suspected extra-gastric or delayed-onset anisakidosis.

Diagnosis and Treatment Methods

Gastric anisakidosis was the most frequently reported form of the disease, consistent with findings from retrospective cohort studies comparing gastric and intestinal presentations [36]. This predominance may reflect the biology of the parasite, as Anisakis larvae often embed in the gastric mucosa shortly after ingestion [3]. However, it is also likely that allergic anisakidosis remains underreported due to limited clinical documentation and inconsistent recognition in case reports. Furthermore, our review excluded studies requiring patient recruitment, which may have inadvertently omitted cases of allergic anisakidosis that are more likely to be captured in prospective or clinical cohort studies.

Endoscopy emerged as the most widely used method for both diagnosing and treating anisakidosis. Numerous studies have demonstrated that prompt endoscopic removal of the parasite can effectively resolve symptoms in patients with gastric infection [12, 36]. In cases where the parasite has migrated further along the gastrointestinal tract, colonoscopy has proven effective for managing colonic anisakidosis [44].

Diagnosis of intestinal anisakidosis remains particularly challenging, as the deeper location often precludes direct endoscopic access. In such cases, CT imaging plays a critical role in guiding treatment decisions. Depending on the severity and localisation of the infection, patients may be managed conservatively or may require surgical intervention, especially in cases involving bowel obstruction, perforation, or mass-like lesions. A tailored, case-specific approach that integrates clinical presentation with imaging and serological findings is essential for effective management of anisakidosis across its varied presentations.

Causative Agents and Identification

Anisakis simplex was identified as the most commonly reported species associated with human anisakidosis. Other species, including Anisakis pegreffii and Pseudoterranova decipiens, were also documented, though less frequently. This variation in species prevalence may reflect differences in their capacity to cause human infection. In Japan, where anisakidosis is most prevalent, most cases are attributed to Anisakis simplex, which is widespread in the Pacific Ocean [49]. By contrast, A. pegreffii is more commonly found in mackerel caught in the Kyushu region [49]. Experimental studies have demonstrated that A. simplex migrates up to 100 times faster than A. pegreffii in agar, and has a 63% higher tissue penetration rate, which may explain its higher infectivity and clinical prominence [49]. Nevertheless, both species pose a risk to consumers of raw or undercooked seafood and require continued monitoring through surveillance programs.

While many studies relied on morphological and histopathological methods for species identification, only a limited number employed molecular techniques such as PCR [50,51,52]. Morphological identification, although useful, often lacks the resolution needed to distinguish closely related species—especially in larval stages, leading to frequent default identification as A. simplex [53]. Accurate species-level identification is critical for elucidating the epidemiology of anisakidosis and understanding the varying risks posed by different anisakid species. As such, clinicians and researchers should prioritise the use of molecular diagnostic tools to confirm species identity and improve disease tracking and patient management.

As the literature search concluded in December 2023, studies published after this date were not included. This may have resulted in the omission of more recent data, particularly from 2024 to 2025, and highlights the need for future updates as the literature continues to expand.