Control of Coccidiosis due to Eimeria bovis and Eimeria zuernii in Calves with Toltrazuril under Field Conditions in Comparison with Diclazuril and Untreated Controls

Toltrazuril and diclazuril: comparative evaluation of anti-coccidial drugs using a murine model

Intestinal coccidiosis caused by Eimeria protozoan species is an economically important disease, especially in poultry and cattle. Anti-coccidial drugs commonly used for controlling coccidiosis are toltrazuril (TTZ) and diclazuril (DCZ). In this study, the efficacies of TTZ and DCZ were compared using a murine model, and the effect of these treatments on the induction of acquired resistance was evaluated. Male C57BL/6J mice were inoculated with 1,000 sporulated E. vermiformis oocytes and treated with TTZ or DCZ. The recommended TTZ dose for cattle (15 mg/kg) completely prevented oocyte excretion. But, mice required 5 mg/kg of DCZ, which is five times the recommended dose for cattle, to reduce oocyte excretion. In E. vermiformis re-infection, TTZ (15 mg/kg) and DCZ (5 mg/kg) treatments did not interfere with the development of acquired resistance. Bodyweight gain was significantly higher in the TTZ-treated group than in the control (untreated/infected) group and the DCZ-treated group, and no significant difference in bodyweight gain was observed between the TTZ-treated group and the healthy (uninfected/untreated) group. Analysis of T lymphocyte subsets in the spleen and mesenteric lymph nodes indicated that the relative populations of CD4+ and CD8+ T cells were reduced in the DCZ-treated and control (untreated/infected) groups, suggesting there was immunosuppression during the infection. However, no reductions in T cell populations were observed in the TTZ-treated group. The results indicated that an optimal anti-coccidial drug is one that can completely break the parasite life cycle in the host animal.

Efficiency of 5% toltrazuril in the metaphylactic treatment of coccidiosis in naturally infected and extensively reared beef calves

Eimeria spp. infection is one of the main diseases that affect young cattle in beef and dairy herds, leading to economic losses and compromising the performance and growth of animals. This study aimed to evaluate the effectiveness of different protocols of metaphylactic treatment with 5% toltrazuril (15 mg/kg) in naturally infected, extensively reared beef calves from birth to 1 year of age. We used 92 calves aged up to 2 weeks of life, initially divided into two experimental groups: treated and control. The animals were evaluated fortnightly with individual count of oocysts per gram of feces (OPG) tests until weaning; thereafter, they were again divided into four subgroups: I-treated at both birth and weaning; II-treated at birth but not treated at weaning; III-not treated at birth but treated at weaning; and IV-neither treated at birth nor at weaning (control). During the experimental period, the animals were evaluated for weight gain, excretion of oocysts, and presence of pathogenic species of Eimeria spp. In the first stage of the study, less oocysts were excreted in the treated group for up to 75 days and at 150 days of age (p < 0.05). In the final stage of the study, significant differences occur between groups I and II, I and IV, II and III, and III and IV (p = 0.3512), in the collection 20 days after treatment. Eimeria bovis was the most frequently identified species during the experimental period. Moreover, there was a positive correlation between the presence of diarrhea in the calves and the number of oocysts excreted, treated group (p = 0.0092) and untreated group (p = 0.2). There was no significant difference in weight gain of animals in any of the study periods (p > 0.05).

Pharmacokinetics and tissue residue of enrofloxacin in healthy, Eimeria-infected broiler chickens and those pre-treated with amprolium and toltrazuril

The pharmacokinetics of enrofloxacin was compared in healthy chickens, Eimeria infected chickens and in Eimeria infected chickens pre-treated with amprolium or toltrazuril following a single IV and oral administration at dose 10 mg/kg. The blood samples were taken after administration at different time intervals (5 min to 24 hours) to determine the pharmacokinetic parameters of enrofloxacin. The different concentrations of enrofloxacin were determined by using HPLC assay method. Serum concentrations versus time were analysed by a non-compartmental method. The results explored a significant decrease in serum concentrations of enrofloxacin at different time intervals and a significant change in pharmacokinetic profiles in Eimeria infected chickens compared with those values in healthy chickens whereas, amprolium improves these values. Toltrazuril leads to a significant decrease in enrofloxacin concentrations compared with infected non-treated chickens. Multiple-dose study revealed a longer withdrawal period of enrofloxacin in infected non-treated and infected chickens pre-treated with amprolium compared with the healthy group.

The resistance of Eimeria spp. to toltrazuril in black grouse (Lyrurus tetrix) kept in an aviary

The black grouse is a critically endangered species in Europe. Aviary breeding and re-introduction programs have contributed to the reinstatement of black grouse populations. Parasitic diseases can influence the species' behavior, choice of habitats, and survival rates. Protozoa of the genus Eimeria are the most prevalent parasites in black grouse. The aim of this study was to evaluate the effectiveness of toltrazuril (TOL) against Eimeria spp. in black grouse kept in an aviary. Eimeria spp. oocysts (mean OPG for all birds = 7,047.84; SD = 5,625.05) were detected in feces samples in a routine parasitological examination. Parasitic infections were treated with toltrazuril Baycox 2.5% (Bayer, Leverkusen, Germany) at 1 ml/1 l H2O administered per os with drinking water twice a day for 2 d, 12 h/24 h. High oocysts counts persisted upon the second parasitic examination. Therefore, the birds were divided into 3 groups in 3 existing aviaries. Toltrazuril was administered according to the same protocol, and its uptake with drinking water was monitored. A parasitological examination conducted 5 d later revealed the presence of parasites, and the TOL dose was increased to 3 ml/1 l H2O. When oocysts were detected in a successive exam, the TOL dose was further increased to 5 ml/1 l H2O. The increase in TOL dose did not eliminate parasites, therefore, the treatment was discontinued. The fecal egg count reduction test (FECRT) revealed that 1 ml of TOL reduced fecal oocysts counts (OPG) by 0.02%, the second application of the same TOL dose reduced OPG by 0%, 3 ml of TOL reduced OPG by 0%, and 5 ml of TOL reduced OPG by 65.7%. The applied doses of TOL did not induce significant differences in the fecal oocysts counts of any of the identified species of coccidia. The results indicate that the coccidia species infecting black grouse have natural resistance to TOL.

W A A V P guideline for evaluating the efficacy of anticoccidials in mammals (pigs, dogs, cattle, sheep)

This guideline is intended as an aid in the design, implementation and interpretation of studies for the assessment of drug efficacy against Eimeria in cattle and sheep, Cystoisospora in pigs and dogs, and Cryptosporidium in cattle. It deals with the most important aspects of how to conduct both experimental and field studies for dose determination, dose confirmation and assessment of field effectiveness. Also, guidance on the selection of animals, diagnostic techniques, statistical evaluation and methods for the preparation, maintenance and use of parasites is provided. The specific management conditions that may influence the course of natural infections and consequently determine treatment schemes are mentioned and suggestions for best practice in sampling and evaluation of data prior to conducting of efficacy studies are given. The guideline is also intended to assist investigators in carrying out specific studies, provide relevant information for registration authorities involved in the decision-making process, assist in the approval of anticoccidial drugs in the target species, and facilitate the world-wide adoption of standard procedures. Although currently not implemented, issues of drug resistance testing and alternative methods for drug testing are also discussed as future issues in drug testing against mammalian coccidia.

Comparative efficacy of diclazuril (Vecoxan®) and toltrazuril (Baycox bovis®) against natural infections of Eimeria bovis and Eimeria zuernii in French calves

A blinded, randomized, controlled, multi-centric field study was conducted on French dairy farms (n = 9) to evaluate the long term efficacy of metaphylactic, single oral treatments with either 1 mg/kg body weight (BW) of diclazuril (Vecoxan®), or 15 mg/kg BW of toltrazuril (Baycox®) against natural infections with Eimeria zuernii and/or Eimeria bovis, compared to untreated control animals. A total of 199 calves from nine commercial farms aged between 21 and 55 days old at the start of study were included and randomly allocated to one of three groups. Calves on all farms were observed for a period of 78 days post treatment, using both parasitological (oocyst excretion), and clinical parameters (faecal score and body weight). The assessment of efficacy was based on both control of oocyst excretion, and on the average daily weight gains throughout the study. During the whole study period, the mean number of days with diarrhoea (≥ 2) was similar (0.7 days) between treated groups. Excretion in the untreated group peaked at 21 days after treatment. In both the diclazuril and toltrazuril-treated groups, mean oocyst excretion decreased dramatically in the five days following treatment. Thereafter, particularly towards the end of the study period, oocyst counts and percentage levels of E. zuernii were highest in the toltrazuril-treated group. In pooled data from all trial sites, the average daily weight gain was significantly (p = 0.01) higher (+ 0.057 kg/day) in the diclazuril group when compared to the toltrazuril group, and the average body weight gain of the diclazuril treated group was 4.4 kg higher than the toltrazuril group. On eight of the nine trial sites, the average daily gain was greater in the diclazuril group than in the toltrazuril group. This study demonstrates that, over an extended observation period of 78 days, metaphylactic treatment with both diclazuril and toltrazuril reduces the impact of coccidiosis, but greater performance benefits based on average daily weight gains, were achieved following the use of diclazuril.

Buxtonellosis and coccidiosis of cattles in Northern Serbia

The study presents the results of a two-year research of protozoan infections of cattles from the Northern-Bačka district (Voјvodina, Serbia). The research was conducted on cow-farms and in private cattle-breeding households, with variuos levels of hygenie. The study included 224 specimens (71 calves, 48 hifers and 105 cows). 22.91% of examined heifers and 15.23% of cows were infected with the ciliate Buxtonella sulcata. The presence of coccidiosis was detected in 45.07% of the calves, 14.58% of the heifers and 6.67% of the cows. The clinical signs of diarrhoea were established in all of the specimens which had more than 1,500 cysts of B.sulcata in 1g of faeces. In the examined calves the number of oocysts was less than 1500 in 1g of faeces, so the coccidiosis did not influence the incidence of the diarrhoea. The results show the first diagnostic record of the ciliate B.sulcata of bovines in Serbia, and this finding contributes to the existing knowledge about the etiopathogenesis of protozoan disease of cattle in this area.

Effect on performance of weanling alpacas following treatments against gastro-intestinal parasites

Nematodes and coccidia are common parasites of alpacas (Vicugna pacos), and important causes of disease in this increasingly popular livestock species. Endoparasitic infestation is thought to increase at times of natural or imposed stress, and antiparasitic treatments are often administered, although to date there is little evidence regarding their effect. Thirty-one alpaca juvenilles (cria) were divided into four groups at weaning, and received either no treatment as a control (C), fenbendazole anthelmintic (FB), toltrazuril coccidiostat (T), or both treatments (FBT). Body weights and faecal egg/oocyst counts were recorded weekly for six weeks following treatment. Although the prophylactic treatments decreased faecal egg/oocyst counts of the target organisms in the short term, there was no significant difference in egg/oocyst output over the course of the trial from animals given wormer, coccidiostat or both treatments. The group receiving anthelmintic only showed a significant reduction in live weight gain (LWG), with no significant difference in LWG between the other groups. At the conclusion of the trial, 'wormed only' alpacas weighed 3.3% less than at weaning, losing an average 1.3 kg over six weeks, whereas average LWG in the control group was 2.5 kg. Antiparasitics transiently reduced egg/oocyst output but results suggest that further investigation is required on the action of anthelmintics administered to alpaca cria at weaning and their effect on animal health and welfare.

A novel serine/threonine protein phosphatase type 5 from second-generation merozoite of Eimeria tenella is associated with diclazuril-induced apoptosis

Screening the anticoccidial drug targets is very important for developing novel drugs and revealing the molecular basis of drug resistance in coccidia. Due to high effectivity and safety, diclazuril was used widely in the poultry industry. To assess the roles of the serine/threonine protein phosphatase type 5 of second-generation merozoites in Eimeria tenella (EtPP5) in the anticoccidial activity of diclazuril against chicken coccidiosis, EtPP5 was cloned using reverse transcriptase polymerase chain reaction and rapid amplification of cDNA ends. Ultrastructural changes in second-generation merozoites and mRNA expression level of EtPP5 were monitored by transmission electron microscopy (TEM) and quantitative real-time PCR, respectively. The results showed that the full length of the cloned EtPP5 cDNA (2,495 bp) encompassed a 1,647-bp open reading frame encoding a polypeptide of 548 residues with an estimated molecular mass of 60.82 kDa and a theoretical isoelectric point of 5.89. Molecular analysis of EtPP5 reveals the presence of a C-terminal phosphatase domain and an extended N-terminal tetratricopeptide repeat motif, a typical feature of protein phosphatases. The cDNA sequence has been submitted to the GenBank database with accession number JX987508. EtPP5 shared 89% homology with the published sequence of a PP5 ortholog of Toxoplasma gondii at the amino acid level (GenBank XP_002364442.1). TEM observed that diclazuril induced ultrastructural changes in second-generation merozoites. Quantitative real-time PCR analysis showed that compared with the control group, the level of EtPP5 mRNA expression was significantly downregulated by 51.4% by diclazuril treatment. The high similarity of EtPP5 to previously described PP5 of other organisms, as well as its downregulated expression and connection with apoptosis in the second-generation merozoites induced by diclazuril, suggests that it could act an important role in understanding the signaling mechanism underlining the diclazuril-induced merozoites apoptosis.

Receptor for activated C kinase ortholog of second-generation merozoite in Eimeria tenella: clone, characterization, and diclazuril-induced mRNA expression

The receptor for activated C kinase (RACK) cDNA of second-generation merozoites of Eimeria tenella was cloned using reverse transcriptase polymerase chain reaction and rapid amplification of cDNA ends, compared with other species, and then successfully expressed using the pET-28a vector in Escherichia coli BL21 (DE3) (EtRACK). Nucleotide sequence analysis revealed that the full length of the cloned cDNA (1,264 bp) encompassed a 957-bp open reading frame encoding a polypeptide of 318 residues with an estimated molecular mass of 34.94 kDa and a theoretical isoelectric point of 5.97. Molecular analysis of EtRACK reveals the presence of seven WD40 repeat motifs. EtRACK localizes to the cytoplasm and nucleus in second-generation merozoites of E. tenella. The cDNA sequence has been submitted to the GenBank Database with accession number JQ292804. EtRACK shared 98% homology with the published sequence of a RACK protein from Toxoplasma gondii at the amino acid level (GenBank XP_002370996.1). Recombinant protein expression was induced using 1 mM of isopropyl β-D-1-thiogalactopyranoside in vitro at 30 °C. Sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis showed that the 39.79-kDa fusion protein existed in unsolvable form. Quantitative real-time PCR analysis showed that compared with the control group, the level of EtRACK mRNA expression in the treatment group was downregulated by 81.3% by diclazuril treatment. The high similarity of EtRACK to previously described RACKs of other organisms, as well as its downregulated expression in second-generation merozoites induced by diclazuril, suggests that it could play a key role in the signaling event that precedes protein secretion and parasite invasion. Moreover, the downregulation of EtRACK mRNA expression also enriches studies on the mechanism of action of diclazuril on E. tenella.

Study of the comparative efficacy of toltrazuril and diclazuril against ovine coccidiosis in housed lambs

A blinded, controlled and randomised field study was conducted on a sheep farm with a known history of coccidiosis and a high prevalence mainly of the pathogenic coccidium Eimeria ovinoidalis. The efficacy of treatment with toltrazuril (Baycox 5% suspension) against natural infections with Eimeria crandallis and/or Eimeria ovinoidalis in housed lambs was investigated in comparison with diclazuril and untreated controls. Both drugs were administered either metaphylactically (i.e., in the prepatency of Eimeria spp.) or therapeutically (after onset of oocyst excretion). A total of 145 animals aged 1 to 5 days at the start of the study were included. Examination of faecal samples was performed every second day between days 13 and 49 of the study. The assessment of treatment efficacy was based mainly on total oocyst excretion and the number of E. crandallis and E. ovinoidalis oocysts (OPG) shed throughout the study. Oocyst excretion was reduced significantly in both groups treated with toltrazuril compared with the untreated control group and with both diclazuril-treated groups. The most prevalent and most severe diarrhoea was observed in the untreated control group. In this study, toltrazuril proved to be highly effective in controlling ovine coccidiosis both metaphylactically and therapeutically. The efficacy of toltrazuril was significantly higher than the efficacy of the control substance with regard to the duration and amount of oocyst excretion, both for the comparison of metaphylactic as well as therapeutic treatment.

Efficacy of toltrazuril (Baycox 5% suspension) in natural infections with pathogenic Eimeria spp. in housed lambs

A field study was conducted to evaluate the effect of a single oral treatment with 20 mg/kg body weight (BW) of toltrazuril (Baycox 5% suspension)--TOL--in comparison to a single oral treatment with 1 mg/kg BW of diclazuril (Vecoxan suspension orale, 2.5 mg/ml)--DIC--and an untreated control group (CTRL) on naturally acquired Eimeria infections in lambs. On a French sheep farm with a known history of coccidiosis, 75 housed lambs aged 10-14 days were randomised and allocated to one of three groups. During an observation period of 60 days after treatment, clinical (faecal consistency, BW) and parasitological parameters (oocyst excretion) were evaluated. Excretion in the negative control group started 3 days after treatment and peaked on the 31st day with a prevalence of 80%. Animals were predominantly infected with Eimeria ovinoidalis. Treatment with toltrazuril, but not with diclazuril, resulted in significantly reduced numbers of excreting animals. The number of excretion days and the average oocyst excretion decreased significantly in both the TOL and the DIC groups compared to the CTRL, with the TOL group showing significantly fewer excretion days and excretion intensities than the DIC group. Changes in the faecal consistency were moderate throughout the study and not significantly different between the groups. Daily weight gains were higher in the TOL group compared to the DIC and CTRL groups which did not differ. This study demonstrates the good efficacy of toltrazuril administered orally to lambs in the prepatent period in subclinical natural Eimeria infections in housed lambs.