Swine Eimeriosis (coccidiosis)
LEVELS: Highly unlikely; No human illness; Already in the herd; Laboratory-dependent; Negligible; Negligible; Some; Available, or not needed
| Register id | eimeria_spp |
| Type | parasite |
| Scientific name | Eimeria |
| NCBI taxid | 5800 |
| Evidence | 1 document(s) |
| Assigned | 2026-09-04, against criteria version 093366e352a2 |
Overview
This is a genus-level entry covering the Eimeria coccidia of pigs, distinct from Cystoisospora suis which causes neonatal coccidiosis. Infection is common — surveys found 60-95% of pigs raised in lots or in the wild infected, and 82-95% of sows — but disease is not: reports of clinical coccidiosis in swine caused by Eimeria are rare, and inoculating pigs with large numbers of oocysts of E. debliecki, one of the commonest species, does not produce clinical disease. Where illness has been attributed to the genus it involves E. debliecki, E. scabra and E. spinosa in weaned pigs and sows. The circumstance that creates risk is a naive pig meeting a heavily contaminated environment, which is why age-segregated rearing and changes in housing have, if anything, increased the chance of an outbreak: breeding stock born and reared in confinement can meet the parasite for the first time as adults. The oocysts are easily distinguished from those of C. suis under the microscope. Control is sanitation and anticoccidials; no product is labelled for swine Eimeria in the US, and there is no vaccine. 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, not likely to cause infection in humans"
Basis. Section 60.1.3 makes no mention of human infection, and Eimeria species are not among the protozoa chapter 60 collects under "Other Protozoa of Minor Importance or Potentially Transmissible to Humans".
How this level was decided
INFERRED from the same structured silence. The swine Eimeria species are host-specific. 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, not likely to cause infection in humans"
Basis. No human disease is described in section 60.1.3.
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
Already in the herd: Present in most herds, or carried by pigs themselves, so there is no introduction event to prevent
Corrected by Eric from L4 Extraordinary biosecurity required. Reason: MOVED L4 -> L1, with cystoisospora_suis and on the same reading. He: "c3l1 - present on all herds in my view, rarely clinically apparent." The chapter supports it directly for this genus: Eimeria was found in 82% of sows on US farms WITH a history of coccidiosis and 95% of sows on farms WITHOUT one, and in 60-95% of pigs raised in lots or in the wild. Sows on ordinary US farms are carrying it either way, so there is no introduction event to prevent and level 2 would claim housing keeps out something already present. Note that the higher figure is from the farms with NO coccidiosis history, which is his point exactly: presence and clinical disease are different questions and C3 asks the first.
Basis. ch60 60.1.1: coccidia have "a one-host fecal-oral transmission cycle. An environmentally resistant stage (oocyst) is excreted in feces... Once the oocysts are sporulated, they are resistant to most disinfectants." 60.1.2.4: surveys found Eimeria infections "common (60-95%) in animals raised in lots or in the wild", and 82-95% of sows carried Eimeria. 60.1.3: "Clinical coccidiosis can occur in pigs of any age if naive when exposed to highly contaminated facilities."
How this level was decided
MOVED L3 -> L4 on 2026-09-01 by the five-level rework. Eimeria looks like the soil group and is not: prevalence is 60-95% in lot-raised and wild animals, but the chapter also says clinical coccidiosis "can occur in pigs of any age if naive when exposed to highly contaminated facilities" and that modern age-segregated rearing has increased the risk by leaving gilts naive until they enter a contaminated breeding herd. The contaminated place is the facility, not the paddock, and sporulated oocysts resist disinfectants. C3 now runs on the EFFORT REQUIRED TO EXCLUDE: L1 already in the herd, L2 housing alone keeps it out, L3 routine biosecurity keeps it out, L4 extraordinary biosecurity required, L5 exclusion may not be achievable. FLAGGED FOR ERIC, 2026-09-02, AND THE LEVEL IS HELD RATHER THAN MOVED, alongside cystoisospora_suis. Both sit at L4 on the oocyst reasoning -- sporulated oocysts resist disinfectants, so routine C&D does not close it -- which is about what happens once the agent is on the farm. His Cryptosporidium ruling of 2026-09-02 says C3 asks how it gets onto the farm, but he ruled that on Cryptosporidium and said explicitly that overruling a specific case is not a general rule, so this cell waits for him. THE EVIDENCE POINTS AT L1 RATHER THAN L2: the chapter reports Eimeria in 60-95% of pigs raised in lots or in the wild, and in 82% of sows on US farms with a coccidiosis history and 95% of sows on farms without one. Those are sows on US farms, so on the numbers this is already present in most herds, which is level 1. Level 2 would say housing keeps out something the sows are carrying already.
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
Basis. ch60 60.1.1 and Table 60.1: Eimeria oocysts have four sporocysts each with two sporozoites, against two sporocysts of four sporozoites for C. suis, and 60.1.3 states "Eimeria oocysts can be easily distinguished from C. suis". 60.1.3: "Reports of coccidiosis in swine caused by Eimeria species are rare." "Experimental studies have demonstrated that inoculation of large numbers of oocysts of E. debliecki, one of the most common coccidians of swine, does not cause clinical disease."
How this level was decided
Confirmation is routine faecal flotation and the oocysts are easily told from C. suis on morphology, so the test is not the difficulty. What rules out level 1 is that nothing points here clinically: clinical Eimeria coccidiosis is rare, the commonest species does not cause disease even at high dose, and diarrhoea in a weaned pig has a long differential. Not recognised clinically, locally confirmable. Level 2.
C5 Production cost
Financial impact on the infected farm's cost of production
Negligible: No measurable effect on cost of production
INFERRED — reasoned, not stated. The evidence implies this level rather than stating it. The reasoning is below.
Corrected by Eric from L2 Minor. Reason: "c5l1, this seems to almost be an incidental finding when it is identified, cases where it is associazted with clinical disease seem to be rare"
Basis. ch60 60.1.3: "Reports of coccidiosis in swine caused by Eimeria species are rare, but age-segregated rearing and changes in housing over the last few decades have increased the risk for outbreaks. Eimeria debliecki, E. scabra, and E. spinosa have been associated with clinical coccidiosis in weaned pigs and sows." "Clinical coccidiosis can occur in pigs of any age if naive when exposed to highly contaminated facilities. Coccidiosis can occur in breeding stock that are born and reared in confinement and then exposed as breeding stock."
How this level was decided
INFERRED -- no rate and no cost figure. Clinical disease is rare and the commonest species is non-pathogenic even experimentally, which caps this low. Against that the chapter records a mechanism by which modern practice has made it worse rather than better: rearing pigs in clean confinement leaves them naive, so gilts entering a contaminated breeding herd meet the parasite for the first time as adults. Small and occasional losses. Level 2.
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, no evidence to suggest diagnosis will affect markets"
Basis. Section 60.1.3 records no trade measure, movement control or consumer response.
How this level was decided
INFERRED. A non-zoonotic enteric coccidian, endemic and rarely clinical, has no route to pork supply or demand. Level 1.
C7 Treatment potential
Potential for treatment to improve outcomes
Some: Treatment exists but is inconsistent, requires extralabel use, or works only in some circumstances
CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.
Confirmed by Eric. CONFIRMED. "c7l2, extralabel treatment available if necessary"
Basis. ch60 60.1.2.6 notes that studies of anticoccidial activity "in weaned or finishing pigs are of no value in predicting the ability of these drugs to control disease in nursing pigs" -- which implies such activity is established in the older pigs that Eimeria affects. No product is named as labelled for Eimeria in swine in the US.
How this level was decided
INFERRED. The chapter treats anticoccidial efficacy in weaned and finishing pigs as a given while denying it transfers to neonatal C. suis, so treatment for this genus exists. Scored level 2 rather than 1 on the same basis as cystoisospora_suis: no US-labelled swine product is named, which under the standing note SCORING/treatment_potential is extralabel use. FLAGGED with that entry -- one answer from Eric on US anticoccidial labelling settles both.
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 clinical or market imperative for a vaccine"
Basis. No vaccine is described for swine Eimeria in ch60. Control is through sanitation and anticoccidials.
How this level was decided
INFERRED. No vaccine exists, and under the reworded criterion the question is whether one is warranted. Clinical Eimeria coccidiosis is rare in pigs and the commonest species causes no disease at all, so there is no unmet need to record. Level 1 on the second clause -- and deliberately a level below cystoisospora_suis, which is the same genus group but a disease the chapter calls the most important protozoal disease of swine.
Levels and evidence are generated from data/assignments/eimeria_spp.yml; the overview is authored in data/overviews/eimeria_spp.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.