Red Stomach Worm
LEVELS: Highly unlikely; No human illness; Housing alone keeps it out; Laboratory-dependent; Minor; Negligible; Little; Available, or not needed
| Register id | hyostrongylus_rubidus |
| Type | parasite |
| Scientific name | Hyostrongylus rubidus |
| NCBI taxid | 108470 |
| Evidence | 1 document(s) |
| Assigned | 2026-09-04, against criteria version 093366e352a2 |
Overview
Hyostrongylus rubidus, the red stomach worm, lives in the glands of the pig's stomach. Its life cycle is direct and requires pasture — eggs pass in faeces, develop to infective larvae in about a week, then migrate onto grass to be eaten — so hyostrongylosis is a disease of pastured pigs and moderately common where pigs go outdoors. Some larvae shut down in the gastric glands in a dormant state and resume later. The worms suck small amounts of blood, producing catarrhal gastritis and mucosal erosion, and they may contribute to gastric ulceration; those changes in the stomach lining can cost feed conversion and weight gain. Beyond that, the reference chapter is candid that little is known about the parasite's pathogenicity. Diagnosis is not straightforward because the eggs resemble those of Oesophagostomum and Globocephalus and separating them requires careful measurement and larval culture. Avermectins, fenbendazole and dichlorvos are all effective. No human infection is described.
C1 Zoonotic potential
Likelihood of transmission from pigs to humans
Highly unlikely: Human infection with the agent has never been reported, or has been reported but is not attributed to pig or pork exposure
CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.
Confirmed by Eric. CONFIRMED. "c1l1, no evidence of human infection"
Basis. Section 61.2.2.1 covers Hyostrongylus in full and makes no mention of human infection. The chapter names the human angle wherever one exists and states its absence explicitly for Globocephalus.
How this level was decided
INFERRED from the same structured silence as the other non-zoonotic helminths in this batch. Level 1.
C2 Zoonotic impact
Severity of human illness caused by the agent
No human illness: Agent does not cause illness in people
CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.
Confirmed by Eric. CONFIRMED. "c2l1, no evidence of human infection"
Basis. No human disease is described in 61.2.2.1.
How this level was decided
INFERRED. C2 scores level 1 whenever the agent does not cause disease in people.
C3 Herd introduction risk
Effort required to keep the agent out of the herd
Housing alone keeps it out: Raising pigs indoors and off soil breaks the cycle, so no ongoing biosecurity program is needed and only outdoor herds stay exposed
Basis. ch61 61.2.2.1: "Eggs are passed in the feces and develop into infective larvae in about 7 days. The larvae migrate away from feces and onto grass, where they are subsequently ingested by swine. Thus, the life cycle is direct, and hyostrongylosis is a disease of pastured swine." "Some larvae may remain in the gastric glands in a state of hypobiosis."
How this level was decided
MOVED L3 -> L2 on 2026-09-01. A direct life cycle onto pasture the pigs themselves contaminated, and pasture is the operative word: this is a parasite of outdoor and lot-raised pigs. Scored under the 2026-09-01 C3 rework: level 2 is where the farm's own housing decision closes the route permanently, and an outdoor herd's exposure is a consequence of that production choice rather than a property of the agent. Eric: "accept being an outdoor herd itself is the biosecurity failure/risk, not the agent per se, and covers things like most gut parasites." Level 3 is reserved for routes no housing system blocks. NOTE: hypobiosis in the gastric glands means an infected pig carries the parasite into a clean unit, which is a level 2 introduction route rather than an argument against level 2 -- incoming stock is exactly what routine biosecurity screens. CONFIRMED AT L2 by the five-level rework later the same day. The four-level L2 had held two different amounts of work -- this case, where housing alone does it, and agents like progressive atrophic rhinitis that need a running biosecurity program and are equally excludable from an outdoor herd. Eric spotted it: the qualifier "but outdoor herds may still be exposed" is true here and false there. Those agents moved up to the new L3 and this one stayed, on a level that now says only what is true of it.
C4 Detection difficulty
Difficulty of recognizing and confirming infection
Laboratory-dependent: The presentation does not point to this disease specifically, but local or regional laboratories can confirm it with a validated assay once it is suspected
CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.
Confirmed by Eric. CONFIRMED. "l2, straightforward to diagnose"
Basis. ch61 61.2.2.1: "These strongyle eggs resemble those of Oesophagostomum and Globocephalus; their differentiation requires careful measurement of eggs and harvest of infective ensheathed L3 larvae from incubated fecal cultures." "little is known about the pathogenicity of this parasite."
How this level was decided
The same limitation as Oesophagostomum, stated in the same terms: a strongyle egg on flotation does not identify the genus, and separating the three requires egg measurement and larval culture. Nothing in the clinical picture points here either. Level 2.
C5 Production cost
Financial impact on the infected farm's cost of production
Minor: Small and generally short-lived losses with little effect on overall cost of production
CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.
Confirmed by Eric. CONFIRMED. "c5l2, easy and inexpensive to control in settings where exposure may occur"
Basis. ch61 61.2.2.1: "Although H. rubidus is reported from many areas of the world, little is known about the pathogenicity of this parasite. They suck a small amount of blood, leading to catarrhal gastritis and potential mucosal erosion. H. rubidus may be a factor in the pathogenesis of gastric ulceration, and these changes in the gastric mucosa can impact feed conversion and weight gains." 61.2.2: "One, Hyostrongylus, is moderately common."
How this level was decided
INFERRED. The chapter hedges throughout -- little is known, may be a factor, potential erosion -- while naming a plausible route to real cost through gastric ulceration and feed conversion. Moderately common, blood-feeding, and pasture-dependent. Small losses rather than a measurable increase in cost of production. Level 2. NOTE: the standing note SCORING/production_cost_impact would push this to level 1 for a fully confined herd, since this is explicitly a disease of pastured swine, and the chapter warns that outdoor production is resurging. Held at 2 because the parasite is moderately common where pigs are on soil and the hypobiotic reservoir survives moves.
C6 Market impact
Duration of material disruption to pork and pig markets
Negligible: Little or no material disruption to supply or demand when disease occurs on one or more farms
CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.
Confirmed by Eric. CONFIRMED. "c6l1, old disease, diagnosis will not trigger any effect on the market"
Basis. Section 61.2.2.1 records no trade measure, movement control or consumer response.
How this level was decided
INFERRED. A non-zoonotic gastric nematode of pastured pigs has no route to pork supply or demand. Level 1.
C7 Treatment potential
Potential for treatment to improve outcomes
Little: Effective pathogen-directed treatment is available and works, or animals recover acceptably without it
Basis. ch61 61.7.2.1: avermectins "control A. suum (adults and fourth stage larvae), Hyostrongylus rubidus (adults and fourth stage larvae)". 61.7.2.2: "Fenbendazole products are labeled for the treatment of A. suum, Metastrongylus, Oesophagostomum, Hyostrongylus, Stephanurus, and Trichuris in the United States." 61.7.2.6: dichlorvos has "good efficacy against Ascaris, Oesophagostomum, Trichuris, and Hyostrongylus".
How this level was decided
Three effective options across three drug classes, one of them explicitly US-labelled and covering fourth stage larvae as well as adults. Effective treatment is available and works. Level 1.
C8 Vaccine availability
Availability of effective vaccines or bacterins
Available, or not needed: Effective vaccines are widely available in the US or secured for national outbreak response, or the disease does not clinically or economically justify vaccinating
CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.
Confirmed by Eric. CONFIRMED. "c8l1, no market imperative to develop a vaccine"
Basis. No vaccine for Hyostrongylus is described in ch61. Control is by housing, sanitation and anthelmintics.
How this level was decided
INFERRED. No vaccine exists and none is warranted for a parasite of uncertain pathogenicity that three labelled drug classes remove and that slatted housing prevents. Level 1 on the second clause.
Levels and evidence are generated from data/assignments/hyostrongylus_rubidus.yml; the overview is authored in data/overviews/hyostrongylus_rubidus.md. Do not hand-edit this page — corrections go in data/assignments/CORRECTIONS.yml.
Quoted material marked Basis is from Zimmerman JJ, Karriker LA, Ramirez A, Schwartz KJ, Stevenson GW, Zhang J, eds. Diseases of Swine, 12th edition. Hoboken: Wiley Blackwell, 2025 — except where another source is named in the quotation itself.