What is the documented prevalence of Eurytrema spp. in livestock by country, and how does that correlate with human entomophagy practices?
Executive summary
Eurytrema spp. are pancreatic trematodes with a documented, patchy but global presence in ruminant livestock—reports span Asia, Europe, Russia and South America—with measured herd- or abattoir-level prevalences ranging from low single digits to nearly three-quarters in localized studies (for example, a mean bovine prevalence of 47.8% in central‑west Paraná, Brazil) [1]. Human infection appears exceptional and epidemiologically linked to eating raw or undercooked orthopteran insects that carry metacercariae, so regions with entomophagy report the few human cases while places without insect‑eating traditions have effectively no zoonotic transmission despite animal endemicity [2] [3].
1. The geographic snapshot: where Eurytrema shows up in livestock
Published and recent reports document Eurytrema spp. in domestic ruminants across multiple continents: China (including multiple provinces), Vietnam, Nepal, Bangladesh, Indonesia, Japan, the Philippines, Brazil and Argentina, and the genus is described as having a worldwide distribution that includes Europe and Oriental Russia as well [4] [1] [5] [6] [7]. Country‑level recent surveys emphasize local endemic foci rather than uniform national prevalence—for instance, the first detailed study in Argentina confirmed endemicity in central‑northern Misiones Province [6], and molecular identification studies have recovered Eurytrema from cattle and buffaloes in northern Vietnam bordering China [4].
2. Measured prevalence: highly variable, method‑dependent, often local
Prevalence estimates vary widely by study, host species and diagnostic method; a large abattoir study in Paraná, Brazil measured a mean bovine prevalence of 47.8% with monthly variation from about 27% to 73% [1], while other surveys report lower or more moderate rates in sheep or cattle (for example, E. pancreaticum found in 23.3% of examined sheep in one review) [8]. Diagnostic sensitivity matters: comparative coprological methods show substantial disagreement and indicate some techniques underdetect infections, so reported prevalences can be understated where less sensitive assays are used [9]. Several recent papers therefore stress that prevalence is best interpreted as local herd‑level burden rather than a single national figure [6] [4].
3. Biology that shapes distribution: snails, grasshoppers and livestock movement
The parasite’s terrestrial life cycle requires an obligate first intermediate (land snails such as Bradybaena similaris) and second intermediate (orthopteran insects like Conocephalus grasshoppers and some crickets), with ruminants as definitive hosts, a biology that both concentrates transmission in environments where these hosts overlap and makes long‑distance spread likely via livestock movements rather than direct human contact [4] [2] [7]. Authors have noted that cross‑border livestock trade and movement probably explain contiguous distributions from China into northern Vietnam [4].
4. Human risk and the role of entomophagy: a conditional link
Epidemiological and life‑cycle reappraisals converge on the transmission route for the occasional human case being the ingestion of raw or undercooked infected insects; several commentaries argue human eurytremiasis is effectively only a risk where entomophagy is practiced and is extremely unlikely in countries without that habit (Brazil cited as an example) [2] [3] [10]. While some reviews describe Eurytrema as a zoonotic concern, the weight of the life‑cycle evidence and case reports links human infection to cultural insect consumption in parts of Asia, making the correlation strong but narrowly conditional rather than generalizable to all countries with livestock infections [11] [2].
5. Gaps, competing interpretations and implications for surveillance
Existing literature documents many local hotspots but lacks a standardized, up‑to‑date global prevalence atlas—reported rates are confounded by diagnostic method, host species sampled and geographic focus, and some authors emphasize veterinary production impacts while others raise public‑health alarms based on a handful of human case reports [1] [9] [3]. The pragmatic interpretation supported by lifecycle and epidemiologic reviews is that Eurytrema is a veterinary parasite of broad but focal distribution and that human cases are exceptional and epidemiologically tied to entomophagy; however, definitive country‑by‑country prevalence maps and harmonized surveillance are missing from the cited literature, limiting precise correlation analyses [4] [6] [2].