Porcine Cryptosporidiosis
LEVELS: Rarely occurs; Moderate; Housing alone keeps it out; Laboratory-dependent; Negligible; Negligible; Little; Available, or not needed
| Register id | cryptosporidium_spp |
| Type | parasite |
| Scientific name | Cryptosporidium |
| NCBI taxid | 5806 |
| Evidence | 3 document(s) |
| Assigned | 2026-09-04, against criteria version 093366e352a2 |
Overview
Cryptosporidium is a coccidian parasite of the intestinal lining found in pigs of all ages worldwide. Most infections in pigs involve the pig-adapted species Cryptosporidium suis and C. scrofarum rather than the C. parvum that causes severe disease in calves, and the pig-adapted species produce milder illness. Whether they produce any illness at all in the field is genuinely doubtful: an Ohio farm study found no association between infection and diarrhoea, and the wider literature reports experimental infection causing diarrhoea and gut damage but no diarrhoeal outbreaks in naturally infected animals. The clearest evidence of harm comes from co- infection — with rotavirus present, C. suis killed piglets that otherwise had only mild signs. The organism is very difficult to exclude: oocysts are infectious the moment they are passed, are shed in enormous numbers, survive months, and resist most disinfectants — the same Ohio study found it on a modern farm with wire and mesh floors where the pigs had minimal contact with their own faeces. Recovery of oocysts from pig faeces is unreliable, and identifying which species is present requires PCR and sequencing. No drug or vaccine is proven effective in swine, so control is entirely management. Sporadic human cases of the pig-adapted species are recorded, but the risk pigs pose to people is regarded as limited.
C1 Zoonotic potential
Likelihood of transmission from pigs to humans
Rarely occurs: Human infection from pigs is plausible but has only rarely been reported, and specific control points are not commonly implemented to prevent transmission to humans
CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.
Confirmed by Eric. CONFIRMED. "c1l2, agree with assessment"
Basis. ch60 60.4.4: "Regarding zoonotic potential, Cr. parvum is not highly prevalent in pigs, and although sporadic cases of Cr. suis and Cr. scrofarum have been reported in humans, the risk that pigs pose as a source for human infections is apparently limited." 60.4: "the most frequently found species in naturally infected pigs are porcine-specific species, Cr. suis and Cr. scrofarum." 60.4.3: "Pigs can harbor multiple species, including Cr. parvum, which are infectious to humans."
How this level was decided
RE-READ AND HELD AT L2 2026-09-04 AGAINST THE REWORDED LABELS. ch60 60.4.4: "sporadic cases of Cr. suis and Cr. scrofarum have been reported in humans" -- those are the PIG-ADAPTED species turning up in people, which is attribution to a pig source, rarely reported.
PREVIOUS ANSWER, kept because the evidence behind it has not changed, only the level boundary: Human infection with the pig-adapted species has been reported, so this is not level 1 -- but the chapter calls those cases sporadic and judges the risk pigs pose as limited, and the broadly zoonotic Cr. parvum is uncommon in pigs. Nothing in pork production is directed at preventing cryptosporidial transmission. Plausible, rarely reported, no control point: both clauses of level 2.
C2 Zoonotic impact
Severity of human illness caused by the agent
Moderate: Clinically important illness is common and may require medical treatment or hospitalization, but death or permanent disability is uncommon
CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.
Confirmed by Eric. CONFIRMED. "c2l3, agree with assessment" EARLIER RULING, 2026-09-01, kept because a re- confirmation does not erase the reasoning it rests on: CONFIRMED. "c2l3, well known to cause significant disease in humans"
Basis. Neither ch60 60.4 nor the CFSPH factsheet describes the clinical course of human cryptosporidiosis. The factsheet records clinical cases across many host species and notes that rodent-adapted species are occasionally found in pig faeces without infection.
How this level was decided
INFERRED -- the folder establishes that human infection occurs but does not characterise it. Human cryptosporidiosis is a profuse watery diarrhoea that commonly brings people to medical attention and can be prolonged and life-threatening in the immunocompromised, for whom no reliably effective drug exists. Clinically important illness commonly requiring treatment, with death or permanent disability uncommon in the immunocompetent, is level 3.
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
Corrected by Eric from L4 Extraordinary biosecurity required. Reason: MOVED L4 -> L2, AND HE REAFFIRMED IT AFTER BEING SHOWN THE EVIDENCE AGAINST IT. On the sheet he wrote "c3l2, same rationale as for giardia". The Xiao 1994 survey is the one place the two organisms separate -- on the modern farm with woven wire and mesh floors, Giardia was 1 of 30 weanlings and Cryptosporidium was 8 of 30 -- so the cell was held and put to him rather than written. HIS RULING, 2026-09-02, AND IT IS A RULE ABOUT THE CRITERION RATHER THAN ABOUT THIS CELL: "getting them off soil will effectively keep both agents out of farms, the criteria is mainly about excluding from farm, not the ability of the agent to persist/recycle once inside. The ohio is old, is on old facilities, and doesn't give much farm history. I'm confident both are excluded by L2." See the standing note at SCORING/introduction_risk, which this amends.
Basis. ch60: pigs on farm acquire the pig-adapted species, oocysts are infectious the moment they are passed, and "disinfection of the environment is difficult because oocysts are numerous, can remain infectious for months, and are resistant to most disinfectants". xiao_1994_crypto_giardia_ohio_farms.md supplies the direct test, and it is the reason this paper belongs in this folder as well as Giardia's. The same two Ohio farms, the same samples, the same assay. On FARM 1 -- modern facilities, elevated deck farrowing crates with woven wire floors, mesh-floored weaner pens, "minimal contact with their excrement" -- Cryptosporidium was still found in 8 OF 30 WEANLINGS, while Giardia was found in 1. On Farm 2, with porous concrete and outdoor lot access, it was in 7 of 24 litters and 6 of 32 weanlings. The authors read the difference between farms as a delay rather than an exclusion: "On the farm with better hygiene (Farm 1), Cryptosporidium infection occurred only in weanling piglets, while on the more poorly managed farm (Farm 2), Cryptosporidium infection was found in both nursing piglets and weanlings."
How this level was decided
Level 4, and the new paper is the closest thing to a controlled comparison this criterion gets. The standing note on introduction_risk carves Cryptosporidium out of the level 2 soil group on the ground that its cycle runs inside the building and survives routine cleaning and disinfection; this survey tests that claim on an actual modern farm and confirms it. Wire and mesh floors, which took Giardia to essentially zero on the same farm, left more than a quarter of the weanlings shedding Cryptosporidium oocysts. So housing alone does not keep it out, which rules out level 2; routine cleaning and disinfection do not either, because the oocysts resist the disinfectants, which rules out level 3. What is left is level 4: exclusion would need measures beyond the routine and may still fail. THE GIARDIA COMPARISON IS THE POINT -- these two organisms look alike on paper, were sampled together, and separate cleanly.
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 at level 2 on the 2026-09-02 re-read. He wrote "c3l2" against this cell, repeating the answer he had given to C3 immediately above; the cell is C4 and is on level 2, and the text is "agree with assessment", so it is read as c4l2.
Basis. ch60 60.4.3: "Microscopy, fecal antigen enzyme-linked immunosorbent assay, and PCR, with or without the recovery and concentration of oocysts, have been used. However, recovery of oocysts from pig feces has been problematic, with consistently lower recovery than from feces of other animals." "Because most oocysts of Cryptosporidium species are nearly spherical, range in size from 4.5 to 5.5 um in diameter, and have no distinguishing features, microscopy can be used only to determine the presence of oocysts. Definitive identification of species and genotypes requires the use of molecular techniques such as PCR followed by sequencing."
How this level was decided
Detecting Cryptosporidium is local laboratory work -- microscopy after flotation, or a faecal antigen ELISA -- and the registered entry is the genus, so that is the diagnosis this cell scores. Level 2. NOTE: species identification does require PCR and sequencing, which is reference or research work, and the chapter says that is what settles whether a given infection matters for human risk. If Eric reads the entry as requiring species-level identification to be diagnosed at all, this is level 3.
C5 Production cost
Financial impact on the infected farm's cost of production
Negligible: No measurable effect on cost of production
Corrected by Eric from L2 Minor. Reason: "c5l1, agree with assessment and my reason above" EARLIER RULING, 2026-09-01, kept because a re-confirmation does not erase the reasoning it rests on: "c5l1, I don't think we have a lot of evidence the agent causes disease in pigs"
Basis. ch60: the pig-adapted Cryptosporidium suis produces milder disease than the cattle species used in the severe experimental infections, and infection often produces no signs. The coinfection finding is what raises it above nothing: with rotavirus present, Cr. suis killed piglets that otherwise had only mild signs. xiao_1994_crypto_giardia_ohio_farms.md looked for the association in the field and did not find one: "In our study, no association between the occurrence of diarrhea and Cryptosporidium or Giardia infection was found." The authors summarise the wider literature the same way -- experimental infection of piglets caused diarrhoea and pathological change, "but NO DIARRHEAL OUTBREAKS WERE REPORTED IN NATURALLY INFECTED ANIMALS. In one study, 26% of Cryptosporidium-infected pigs had diarrhea, but most of them had other primary diarrheagenic agents." Two nursing piglets and one weanling in the Ohio survey had severe (4+) infections; most animals sampled had no diarrhoea.
How this level was decided
Level 2, upgraded from INFERRED to supported, and FLAGGED FOR ERIC AS A LEVEL 1 OR 2 JUDGMENT now that there is field evidence to argue from. The case for level 1 is that this is now the same shape of examined negative that puts Giardia at level 1: a US field survey looked for an association with diarrhoea and found none, no natural outbreak has ever been reported, and where infected pigs did scour, most had another primary agent. The case for holding level 2 is the coinfection mechanism, which a prevalence survey cannot see -- Cr. suis is not the primary agent but it worsens the outcome when rotavirus is also present, and unlike Giardia it is not excluded by modern housing, so most US weaners meet it. Level 2 is held on that mechanism, and the difference from Giardia is real rather than an inconsistency: Giardia has no coinfection finding of that kind.
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, agree with assessment and my reason above" EARLIER RULING, 2026-09-01, kept because a re-confirmation does not erase the reasoning it rests on: CONFIRMED. "c6l1, old agent and pigs rarely if ever seem to be the source for human infection, there is little evidence that diagnosis would have an imnpct on markets"
Basis. Section 60.4 records no trade measure, movement control or consumer response. Cryptosporidium "has been found in pigs of all ages worldwide" and porcine cryptosporidiosis "has been reported to occur worldwide".
How this level was decided
INFERRED. An agent found in pigs of all ages worldwide, with no regulatory status and a human risk the chapter calls limited, 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
INFERRED — reasoned, not stated. The evidence implies this level rather than stating it. The reasoning is below.
Corrected by Eric from L2 Some. Reason: "c7l1, agree with assessment and my reason above" EARLIER RULING, 2026-09-01, kept because a re-confirmation does not erase the reasoning it rests on: "c7l1, does not cause significant, if any, diseaese in pigs so no imperative to treat it"
Basis. ch60 60.4.5 states it flatly: "No drugs or vaccines are proven effective for treating Cryptosporidium in swine. Therefore, management measures to control the spread of Cryptosporidium in farms are critical."
How this level was decided
INFERRED. No effective drug exists in any species -- cryptosporidiosis is notoriously refractory to treatment, which is why it remains dangerous in immunocompromised people. Scored level 2 rather than 3 because the pig disease is mild and often absent, so the size of the opportunity is modest: the second clause of level 1 nearly holds but not quite, since the coinfection deaths show there is some outcome to improve. FLAGGED as a judgment between 1 and 2.
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, agree with assessment" EARLIER RULING, 2026-09-01, kept because a re- confirmation does not erase the reasoning it rests on: CONFIRMED. "c8l1, no clinical or market imperative to develop a vaccine"
Basis. ch60 60.4.5: "No drugs or vaccines are proven effective for treating Cryptosporidium in swine."
How this level was decided
INFERRED. No vaccine exists, and under the reworded criterion the question is whether one is warranted. The pig disease is mild, often subclinical, and the human risk from pigs is described as limited, so there is no unmet need to record. Level 1 on the second clause.
Levels and evidence are generated from data/assignments/cryptosporidium_spp.yml; the overview is authored in data/overviews/cryptosporidium_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.