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Ponazuril, a novel antiprotozoal drug in the class of triazine, has shown a promising application on apicomplexan infections in poultry and livestock. However, the effect and mechanism of action of ponazuril against Eimeria tenella (E. tenella) are unclear. The efficacy against E. tenella was initially studied by administering different doses of ponazuril in drinking water. The treated stage and site of ponazuril on E. tenella were observed through ultrastructural and histopathological analyses. Chicks were orally treated with a dose of 15 mg/kg body weight of ponazuril at different endogenous stages of E. tenella post-infection. According to the clinical study, the values of anticoccidial indices (ACI) were 157.0, 162.3, 196.9, 194.5, and 190.9, respectively, when the ponazuril was administered in drinking water at doses of 5, 10, 20, 40, and 50 mg/L for two consecutive days after infection. Among them, the 20 mg/L ponazuril group showed the best anticoccidial effect, which was superior to that of the toltrazuril treatment group, with an ACI value of 191.7. Histological analysis indicated that ponazuril effectively relieved cecal lesions, and decreased the number of merozoites. Transmission electron micrographs (TEM) observed that merozoites became irregular in shape, and some apparent protrusions of the outer membrane were presented especially the second-generation merozoites. Additionally, abnormalities in the development of WFBI and WFBII in the macrogametocyte were observed, which may affect the formation of the ovule wall. Moreover, merozoites in the treated group showed uneven and marginalized chromatin and mitochondrial swelling. These results suggested ponazuril is a potential anticoccidial drug, providing information on the mechanism of anticoccidial effects.

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Ponazuril is a triazine anticoccidial drug which is the main metabolite of toltrazuril in animals, it has excellent activity against many protozoa, including Cystoisospora suis, and has broad application prospects in the control of swine coccidiosis. To evaluate the pharmacokinetic and excretion characteristics of ponazuril, 12 healthy piglets aged 10-14 days were divided into 2 groups for pharmacokinetic studies, which were given 20 mg/kg body weight ponazuril orally and intravenously, respectively. And 6 other piglets were housed individually in metabolic cages and given the same oral dose of ponazuril. After administration, the concentration of ponazuril in plasma, fecal, and urine samples collected was determined using high-performance liquid chromatography (HPLC). The plasma concentration profiles of ponazuril obtained after intravenous and oral administration were analyzed simultaneously by the nonlinear mixed-effects (NLME) model. Following the results, the pharmacokinetics of ponazuril exhibited a Michaelis-Menten elimination with Michaelis-Menten constant Km and maximum metabolic rate Vm of 10.8 µg/mL and 0.083 mg/kg/h. The apparent volume of distribution was calculated to be 735 mL/kg, and the final estimated oral bioavailability was 81%. Besides, cumulatively 86.42 ± 2.96% of ponazuril was recovered from feces and 0.31% ± 0.08% from urine during 0-1,020 h after oral administration. These findings indicated a good oral absorption of ponazuril in piglets with nonlinear disposition and slow excretion largely via feces, implying sustained drug concentration in vivo and long-lasting anticoccidial effects.

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Cats and kittens in animal shelters and catteries regularly suffer from severe gastrointestinal coccidiosis, which can be fatal, and there are no drugs labeled for feline coccidiosis in the United States. Ponazuril, a triazine-class drug, is increasingly used at a dose of 50 mg/kg/d, orally, for three to five days in shelter environments for coccidiosis. A single oral dose of ponazuril paste 15% (Marquis® ; Merial) at 50 mg/kg was administered to six healthy adult cats. Sample analysis was completed via high-performance liquid chromatography. Plasma concentrations peaked at 7.49 ± 2.06 µg/ml at 14.67 ± 7.45 hr post-administration. This study shows that ponazuril achieved a plasma concentration that inhibits growth of similar organisms after a single oral dose in cats. Further studies are necessary to optimize dosing for the treatment of clinical coccidiosis in cats.

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BACKGROUND: The pharmacokinetics of ponazuril have been determined in several species; however, there is very little information on the stability of the drug after storage for long periods of time. This study was undertaken to determine the stability of ponazuril in plasma samples stored at -80 °C, which is the temperature most commonly used in the author's laboratory. METHOD: Spiked plasma samples (0.3, 7.5, and 15 µg/mL) were stored at -80 °C for three months. Analysis occurred on the first day and then once a week for the following twelve weeks. The drug was extracted using a chloroform extraction and separated by high performance liquid chromatography using ultraviolet detection. RESULTS: There was no loss of drug for any concentration for the first four weeks of storage. There was an average loss of less than 5% from day 35 through day 70 and an average loss of 6% on day 77 and 84. The data suggest that ponazuril is stable for 4 weeks when stored at -80 °C and undergoes minimal loss in the remaining 8 weeks.

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The goal of this investigation was to establish a reliable technique for the quantitation of ponazuril in limited sample volumes. Samples were extracted with chloroform and separation was achieved with a Symmetry RP18 column. Ultraviolet absorption was measured at 254 nm. A combination of 0.1% formic acid and acetonitrile (50:50) was used as the mobile phase. The calibration curve was linear from 0.1-25 µg/mL, with a lower limit of quantification of 0.1 µg/mL with a 100 µL sample. The precision and accuracy were well within the range set by the Food and Drug Administration and the recovery was over 95%. This technique was used to analyze ponazuril samples and found to be appropriate for pharmacokinetic studies.

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Coccidial disease is significant in tortoises; Testudines intranuclear coccidiosis (TINC), caused by an unnamed coccidia, causes high mortality in diverse tortoise species. There is a lack of information on anticoccidial drugs in tortoises. The drug ponazuril has demonstrated efficacy in treating mammals infected with similar coccidial disease. Previous empirical use of ponazuril in TINC cases suggests that it may be an effective treatment. In this study, 20 mg/kg of ponazuril was orally administered to tortoises with the goal of achieving blood concentrations known to be effective for anticoccidial therapy in mammals. Ponazuril was measured in tortoise plasma, and noncompartmental analyses of pharmacokinetic parameters were attempted. Ponazuril in these tortoises did not achieve the desired concentrations known to be effective for anticoccidial treatment in mammals. Tortoises showed prolonged oral absorption, and despite sampling for 168 hr (1 wk), a terminal elimination rate constant and half-life were not able to be determined. Additional studies are needed to fully characterize ponazuril pharmacokinetics in red-footed tortoises. The optimal dose for treating TINC remains to be determined.

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The intranuclear coccidian parasite of Testudines (TINC) is an emerging pathogen of tortoises. Three captive red-footed tortoises ( Chelonoidis carbonaria) from an isolated collection presented with multiple acute, nonspecific clinical signs. One tortoise died and was diagnosed with intranuclear coccidiosis on histopathology with confirmation by quantitative polymerase chain reaction (qPCR). In addition to tissues where TINC has been previously described, coccidia were identified in the pineal gland, choroid plexus, and testicular Sertoli cells. The two remaining tortoises survived after treatment with oral ponazuril (20 mg/kg every 48 hr for 56 days) and remained asymptomatic, although not cleared of infection, for 21 months, as the number of coccidian gene copies detected by qPCR was reduced in one tortoise. This report extends the known host range of this parasite to continental South American tortoises, describes new sites of infection by histopathology, and has management implications for this disease.

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Coccidiosis is an important disease of young goats leading to weight loss, diarrhea, and death. In the USA, both ionophores and decoquinate are labeled for prevention of coccidia in goats. However, there are no drugs approved for treatment of clinical cases of coccidiosis in this species. Amprolium is labeled for treatment of coccidiosis in calves while ponazuril, a metabolite of toltrazuril, is labeled for treatment of equine protozoal myeloencephalitis. In this study, 150 young goats housed on concrete lots had fecal samples collected and McMaster fecal oocyst per gram counts performed at 0, 7, 14, and 21 days post-processing. Goats were randomly assigned to receive either amprolium (50mg/kg once a day for 5 days by mouth) or ponazuril (10mg/kg by mouth once) if they had fecal oocyst counts >5,000 per gram. Fecal samples were obtained and oocyst counts performed at days 7, 14, 21, and 28 after the cessation of treatment. Goats were weighed on days 0 and 21 post-processing. Seven goats were enrolled into the amprolium group and 8 into the ponazuril group. Both treatments resulted in decreased oocyst counts post-treatment compared to before treatment. There was no significant difference between fecal coccidian oocyst counts between goats in each group. There was no significant difference in body weight between goats in each group. This study showed that both amprolium and ponazuril were effective in decreasing fecal coccidia oocyst counts in this group of goats. Use of both drugs is currently extra-label in the USA.

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A group of seven, zoo-kept, male black-tailed prairie dogs (Cynomys ludovicianus) were examined as part of their quarantine health evaluation. Microscopic fecal examination demonstrated that all animals were passing oocysts of Eimeria spp. All prairie dogs were treated individually with ponazuril (30 mg/kg p.o.) administered in two treatments 48 hr apart. Three weekly pooled fecal samples following treatment were negative, suggesting clearing of the infection. No adverse clinical signs were noted. Most of the reported anti-coccidian treatments in rodents describe prolonged treatment protocols or administration of treatment in the water, which can result in unnecessary stress and handling or ineffective and uncontrolled level of drug administration, respectively. This is the first report of this treatment protocol in a rodent species, suggesting it is efficacious, easy to administer, and safe when treating similar infections in prairie dogs.

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Cystoisospora (synonym Isospora) spp. infections are common in dogs and cats worldwide, especially in crowded or unsanitary environments. Ponazuril (toltrazuril sulfone) is a widely used oral treatment, but protocols that will produce oocyst excretion below the detection limit in shelter-housed animals have not been determined. The aim of this study was to determine the efficacy of ponazuril paste at each of three dosages (dosage 1, 50mg/kg q24 h for 3 days, dogs n=14, cats n=16; dosage 2, 50mg/kg as a single dose, dogs n=13, cats n=25; or dosage 3, 20mg/kg as a single dose, dogs n=16, cats n=23) in shelter-housed dogs (n=43) and cats (n=64) with confirmed coccidiosis. Fecal oocyst counts and identification and fecal consistency scoring was performed pre-treatment (Day 1) and again at Day 3-4 and Day 8. There were higher proportions of animals with oocyst excretion below the detection limit at both Day 3-4 and Day 8 in the dosage 1 group (dogs 92.9%, cats 87.5%) than in the other two groups (dosage 2, dogs 76.9%, cats 80.0%; dosage 3, dogs 68.8%, cats 47.8%). Animals with high fecal oocyst counts at Day 1 were significantly more likely to be infected at Day 3-4 (dogs, P<0.001; cats, P=0.013). Fecal consistency score at Day 3-4 was not significantly related to infection status (dogs, P=0.898; cats, P=0.136). Further studies are warranted to investigate a ponazuril protocol that can safely reduce fecal oocyst burdens in infected dogs and cats to levels below the detection limit. Environmental decontamination is also important to reduce the likelihood of re-infection.

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