A short page by design: the primary sources, the dated history of the dosing recommendation, and a one-page summary you can print for a consult. Written to be checked, not to be trusted.
1. The twice-daily recommendation was withdrawn in 2014. LeVine, Gookin, Papich and Davidson published a letter withdrawing 30–50 mg/kg q12h after pharmacokinetic work showed a ~10.5 h half-life and near-complete oral bioavailability, with drug still detectable at 48 h. Consumer-facing material still prints the superseded regimen.
2. The revised once-daily dose has never been efficacy-tested. The 2014 letter said so explicitly. It follows from pharmacokinetics and clinical impression, not from a treatment trial.
3. Colonic flush is no longer the preferred collection method. The 2017 review and the guidance built on it favored it; Hedgespeth, Stauffer and Gookin (2020, n = 1,717) found fecal loop samples 2.04× more likely to be PCR-positive than flush samples, with no significant difference between voided and flush. The authors described the earlier recommendation as having rested on anecdote.
| Year | Recommendation | Source |
|---|---|---|
| 2006 | 30–50 mg/kg PO q12h × 14 d; 10 mg/kg failed | Gookin et al., JVIM 20:536–543 |
| 2010 | 35–45 mg/kg BID reported in a small case series | Gookin et al., JVIM 24:1003–1007 (resistance) |
| 2011 | — PK: F ≈ 99.6%, t½ ≈ 10.5 h, detectable at 48 h | LeVine et al., JFMS 13:244–250 |
| 2013 | Delayed-release guar gum 30 mg/kg q24h: 84% clearance, no adverse events; not commercially available | Papich et al., JVPT 36:399–407 |
| 2014 | 30 mg/kg PO q24h × 14 d; q12h withdrawn | LeVine et al., JFMS 16:198 |
| 2017 | Consensus position restated in the state-of-the-art review | Gookin, Hanrahan & Levy, JFMS 19:261–274 |
| 2024 | Auranofin: lethal in vitro, ineffective in naturally infected cats | Gookin et al., Vet Parasitol |
| Method | Sensitivity | Notes |
|---|---|---|
| Direct smear | ≈14% | Fresh, unrefrigerated. Easily confused with Giardia and P. hominis. |
| Culture, modified Diamond's | ≈26% | Method-dependent. |
| InPouch TF | ≈56–59% | The validated commercial system. |
| PCR | ≈94% | Fecal loop > colonic flush ≥ voided. Litter inhibits the reaction. |
| Colonic wash PCR | Higher in older guidance | Now demoted relative to loop sampling (2020, n=1,717). |
The Tritrichomonas Diagnostic Laboratory at North Carolina State University runs PCR for this organism. It does not consult with owners; referring veterinarians may contact Dr. Gookin directly. Several commercial reference laboratories also offer the assay.
All 34 publications from the Gookin laboratory are indexed on the research page, grouped by the question each one answers, with first-authorship marked. The external literature is mapped around it, including the 2013 species proposal (Walden et al., Parasitol Res).
A lay-audience translation layer maintained alongside the primary literature, intended to reduce the number of consultations that begin with "the tests were normal for months." It carries no advertising for prescription products, and its evidence ratings are independent of its affiliate links. If something here is wrong, the corrections log is public and the fix is dated.
A fecal loop sample, from a cat that is currently passing loose stool, kept free of litter. In 1,717 cats, loop samples were 2.04× more likely to be PCR-positive than colonic flush samples, with no significant difference between voided and flush. The 2017 review's preference for flushing rested, by the authors' own later description, on anecdote.
30 mg/kg PO q24h for 14 days. Twice-daily dosing at 30–50 mg/kg was withdrawn in 2014 after PK work showed near-complete bioavailability, a ~10.5 h half-life, drug still detectable at 48 h, and predicted accumulation — with neurotoxicity as the risk. The revised regimen was never efficacy-tested, which the letter stated explicitly.
Warn the owner in advance and in writing: tremors, ataxia, head tremor, agitation, nystagmus, hyperesthesia. Signs begin at least three days in and usually resolve one to four weeks after cessation. Instruct discontinuation at the first sign rather than completion of the course — continuation after signs appear is what turns a reversible toxicity into a serious one.
No agreed interval exists, and the widely used four-week retest cannot support a statement about clearance: relapse has been observed up to 20 weeks post-treatment. A negative is a point-in-time result on an assay of roughly 94% sensitivity. If the answer matters — before rehoming into a multi-cat home, say — test later, and say what was tested and when.
First confirm failure by testing rather than by persistence of diarrhea — some cats with recurrent diarrhea after treatment no longer carry the organism, and the diarrhea has another cause. Then work the differential in order: formulation (compounded product, capsule vs liquid, pigeon powder), dose and compliance, reinfection from an untested cat, then resistance. In the authors' experience, escalating dose or duration in a genuinely resistant cat does not eradicate and increases toxicity risk.
Unresolved. Treating only symptomatic cats risks leaving carriers; treating all exposes healthy cats to a narrow-margin drug. The review notes it is a common misconception that only cats with diarrhea are infected, and that reinfection from a presumed-clear cat can never be ruled out. Confining treated cats until outcome is assessed is the mitigation both approaches rely on.
With checks. The literature names an "impotent formulation" — the 10% pigeon powder — as a cause of failure, and notes that capsules, solutions, suspensions and medicated treats may have significantly different absorption profiles. Pure drug compounded into gelatin capsules is the recommended form. Raw material for compounding has itself been subject to supplier recalls.
The most promising result in the literature is unglamorous and unavailable: a colon-targeted guar-gum formulation achieved 84% clearance with no adverse events at 30 mg/kg q24h, and is not commercially available or readily compoundable. Auranofin failed in vivo in 2024. No other agent has demonstrated eradication. Open questions →
