Evaluation of Paromomycin Treatment for Cryptosporidium serpentis Infection in Eastern Indigo Snakes (Drymarchon couperi)

Abstract

Thirty-four eastern indigo snakes ( Drymarchon couperi ) naturally infected with Cryptosporidium serpentis were randomly divided into two groups. The first group received 360 mg/kg paromomycin twice weekly in a food item for six weeks, while the second group received the food item with no treatment. Cloacal swabs were collected every two months for six months to measure C. serpentis shedding by quantitative polymerase chain reaction testing (qPCR). Snakes that were qPCR negative after six 6 months were immunosuppressed with a single dose of 4 mg/kg dexamethasone sodium-phosphate SC. These snakes were then screened by qPCR for an additional 6 months as described above. Snakes that were qPCR negative after one year of serial sampling were then re-evaluated for C. serpentis via gastric biopsy for histological and qPCR analyses. The paromomycin-treated group were significantly (p=0.008) more likely to test qPCR negative (8/17; 47%, 95% Confidence Interval [CI]: 23.2-70.7) than the control snakes (1/17; 5.8%, 95% CI: 0.01-16.9) prior to immunosuppression. However, there was no significant difference (p=0.5) in C. serpentis status following immunosuppression as only 2/17 (11.7%, 95% CI: 0.01-26.9) paromomycin-treated snakes were qPCR negative six months after immunosuppression compared to 1/17 (5.8%, 95% CI: 95% CI: 0.01-16.9) control snakes. These findings suggest that 360 mg/kg paromomycin twice weekly for six weeks in a food item is ineffective in eliminating C. serpentis in naturally infected D. couperi .

Open Label, Multi-Arm Randomized Clinical Evaluation of Clofazimine and Curcumin Treatments for Cryptosporidium serpentis Infection in Eastern Indigo Snakes (Drymarchon couperi)

“…Low-grade stressors in this case may include lack of thermal gradient and UV lighting and limited exercise. Although not demonstrated in this study, EIS infected with C. serpentis have been shown to clear the infection with no medical intervention (Bogan et al, 2021(Bogan et al, , 2022a. Future studies that measure corticosterone concentrations in captive and wild EIS may be helpful to characterize stress levels in this species, and further investigation into immune system support and its role in reptile cryptosporidiosis is warranted.…”

“…Several EIS had received previous treatments for SGC as part of investigational treatment studies. Study 1 was conducted 2 yr prior to the onset of the current study and had evaluated 360 mg/kg paromomycin PO twice weekly for 6 wk (Bogan et al, 2021). Study 2 was conducted 1 yr prior to the onset of the current study and evaluated 20 mg/kg nitazoxanide, 10 mg/kg azithromycin, and 5 mg/kg rifabutin PO twice weekly for 6 wk (Bogan et al, 2022a) Treatment: Clofazimine capsules (100 mg, Hansperan® 100, Abbott Healthcare Pvt., Ltd., Bhiwandi, India) were dissolved into 100% corn oil (Mazola® Corn Oil, ACH Food Companies, Inc., Memphis, TN, USA) to a concentration of 4 mg/ml.…”

“…All three treatment options were administered through a 12 F rubber gavage tube twice a week for 6 wk. The dosing frequency of twice weekly was chosen to align with the feeding schedule as well as mimic previously published SGC treatment schedules (Rivas et al, 2018;Bogan et al, 2021Bogan et al, , 2022a.…”

“…Many antiprotozoal drugs have been found to be ineffective in controlling cryptosporidial infections in mammals and reptiles (Fayer and Unger, 1986;Graczyk et al, 1996Graczyk et al, , 1998Graczyk et al, , 1999Graczyk et al, , 2000Klingenberg, 1996;Cranfield et al, 1999;Biron, 2008;Rossignol, 2010). Although paromomycin is an aminoglycocide antibiotic that has been proposed as an effective treatment for cryptosporidiosis (Rivas et al, 2018), a controlled trial of paromomycin in EIS naturally infected with C. serpentis has demonstrated that it only decreased C. serpentis shedding and did not eliminate the parasite (Bogan et al, 2021). Nitazoxanide is the only FDAapproved drug for cryptosporidiosis treatment in humans, and combining this drug with azithromycin and rifabutin has been shown to be more efficacious than using nitazoxanide alone (Giacometti et al, 2000).…”

Cryptosporidium serpentis Surveillance in Free-Ranging Snakes to Inform a Reintroduction Strategy for the Eastern Indigo Snake (Drymarchon couperi)

“…All collected samples were submitted for C. serpentis -specific probe hybridization quantitative PCR analysis to the University of Florida's Zoological Medicine and Wildlife Disease Laboratory. Analyses were performed following Bogan et al (2021).…”