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Auranofin has also shown efficacy when it comes to Cryptosporidium. A California based city animals services department reported results using drug provided by SubriMed inc, the company that holds the exclusive license for this use. Their drug Zoafin, (1mg Auranofin) was used to treat canines infected with Giardia and Cryptosporidium.

All canine subjects tested positive and were symptomatic, they were treated with Zoafin (Auranofin) for 5 days.

The retest performed in all protozoal cases were required to be antigen tests as the immune antibody titer will take a number of weeks to return to normal, rendering an antibody retest inconclusive. In the case of cryptosporidium oocysts maybe excreted for weeks after the treatment. The measure for successful treatment is an asymptomatic case, as an antigen test is not recommended to be performed until 2 months after the cessation of treatment.

In this report, 15 dogs were all positive for cryptosporidiosis, five of which also tested positive for giardiasis. They ranged from 27 to 98 lbs, from 9m to 6 years and were male and female. After 5 days of treatment as described, 4 of the 5 giardiasis cases tested negative and all 5 cases were asymptomatic, after treatment and all the cryptosporidium cases were asymptomatic. After treatment with Zoafin (1mg Auranofin) one case was positive for giardiasis after one week, however this case was also asymptomatic. Repeat antigen tests are normally required day 10, however, repeat test results were not available to allow for oocyst or giardial cyst excretion to conclude. No side effects were reported.

In a report made by another independent shelter organization in Arizona, in which free drug was provided by the company, one feline and 12 canines tested positive for giardiasis and were treated with daily dose of Zoafin(Auranofin). 10 cases were negative after treatment (day 5) and at retest (day 10)  all 12 cases were negative.

This indicates that some animals take longer to excrete the cysts than others so be prepared to antigen retest at 7 and 10 plus days. No side effects were reported.

Auranofin has the benefit of treating both the cyst and the trophozoite. Currently used nitronidazoles do not. However, a protocol of treating all the animals in the home, washing the animals and cleaning their environment is recommended  as the viable cysts dispersed before treatment have the potential to reinfect the animal.

Invitro testing supports this low dose approach. Auranofin EC50 concentration is 10 fold less than metronidazole when treating protozoa, and 16 fold lower in treating gram positives when compared to vancomycincin and methicillin, gram positive organisms including those resistant to vancomycinin and methicillin including MR S Aureus, E caecum, E faecalis, S.pneumoniae, S. agalactiae, C. difficilie, T denticola. (Antibacterial activity and mechanism of action of auranofin against multi-drug resistant bacterial pathogens Shankar Thangamani1, Haroon Mohammad1, Mostafa F. N. Abushahba1,2, Tiago J. P. Sobreira3, Victoria E. Hedrick3, Lake N. Paul3 & Mohamed N. Seleem1 )

The low dose, low absorption and short duration of treatment results in a safe drug profile.

Other parasites with in-vitro efficacy data in the literature include: Tritrichonomas, Cryptosporidium, Entamoeba histolytica, Toxoplasma gone, Trypanisoma brucei, Leishmania infants, Schistomiasis

So what about safety?

If you look up Auranofin in the formulary it shows some side effects -it is important to note that these results were gained by doses 40 fold higher than required to treat giardiasis and for 87 days vs 5 days  in this case. So at these doses and duration of treatment it is considered safe,

Contraindications.

In humans: Contraindicated in patients with a gold allergy, and not recommended during pregnancy or severe hepatic or renal insufficiency. The only reported drug interaction is a single patient with elevated phenytoin blood levels. The complications listed in the package insert for long term (> 1 yr) auranofin therapy include dermatologic: rash in 26%; gastrointestinal: loose stools (42%), abdominal pain (14%), nausea (10%); hematologic: anemia, leucopenia, thrombocytopenia in up to 3%; hepatic: elevated liver enzymes: 2%; mucous membranes: stomatitis (13%); renal: proteinuria (1%).

Avoid if using: Penicillamine Phenytoin

Dosing: Contact subriMed for details of our successful three day program.

The results so far have been encouraging and Auranofin to treat giardiasis received the Innovation Waiver from the FDA Center for Veterinary Medicine (CVM) 2019 & 2020, a 2 year process in which safety and efficacy data in model species was provided. An INAD application is expected shortly and this would make this drug the only approved drug for companion animals for the treatment of Giardiasis on the market, as all the currently used drugs are “off label” for this purpose.