Evaluation of optimum conditions for decoquinate nanoliposomes and their anticoccidial efficacy against diclazuril-resistant Eimeria tenella infections in broilers.

Decoquinate (DQ) is used for prophylaxis against coccidian infections within the digestive tract of chickens, but DQ is extremely insoluble in water. Hence, improving the water solubility of DQ is extremely important. First, decoquinate nanoliposomes (DQNLs) were prepared by the thin-film dispersion-ultrasonic method. The preparation conditions of DQNLs were optimized using the orthogonal test. The optimal preparation conditions of DQNLs were: a ratio of egg-yolk lecithin:drug (w/w) of 10:1, ratio of egg-yolk lecithin:cholesterol (w/w) of 5:1, rotary-evaporation temperature of 50 ℃, and ultrasound duration of 15 min. The encapsulation efficiency of DQNLs prepared under these conditions reached 99.24 % and drug loading was 5.67 %. The characterization of optimized DQNLs was also done. Transmission electron microscopy of DQNLs showed that they had the characteristic structure of liposomes. The mean particle size was 115.6 nm. The polydispersity index was 0.175. The zeta potential was -39.1 mV. The stability of DQNLs was high upon storage at 4 ℃. In vivo studies demonstrated that the lower dose (5 mg/L) of DQNLs in drinking water obtained the similar anticoccidial efficacy to that of 40 mg/kg DQ in feed against diclazuril-resistance Eimeria tenella isolate. The in vitro inhibitory effect of DQNLs on the sporulation of Eimeria tenella oocysts was dose-dependent. Therefore, the anticoccidial efficacy of DQ was enhanced significantly after being encapsulated into nanoliposomes.

The history of decoquinate in the control of coccidial infections in ruminants.

Decoquinate is a quinolone derivative that has been used for over 20 years in the control of coccidiosis in domestic ruminants. Decoquinate treats coccidiosis in lambs and calves and prevents coccidiosis in lambs when administered in feed at a dosage of 1 mg decoquinate/kg bodyweight (b.w.) daily for at least 28 days. It prevents coccidiosis in calves and aids in the prevention of coccidiosis in lambs when administered in calf and ewe feed, respectively, at a dosage of 0.5 mg/kg b.w. daily for at least 28 days. Decoquinate also aids in the prevention of abortions and perinatal losses owing to toxoplasmosis by medication of ewe feed at a dosage of 2 mg/kg b.w. daily, fed continuously for 14 weeks prior to lambing. Several field studies have reported reductions in cryptosporidial oocyst shedding. Decoquinate acts early in the life cycle of Eimeria on sporozoites, released from ingested oocysts, and on first-generation meronts, arresting development and release of merozoites and thus preventing further damage to the intestines owing to the gametocyte stages. Production benefits associated with the use of decoquinate are due mainly to its action as a coccidiostat rather than any effects on diet utilization or ruminal fermentation.

Use of coccidiostat in mineral salt and study on ovine eimeriosis.

Coccidiosis is a serious obstacle to sheep production, which is becoming a limiting factor, especially with regard to lamb production. However, there are few studies on this parasite in the State of Rio Grande do Norte. The aim of this study was to evaluate the action of decoquinate, added to mineral salt, for controlling Eimeria infection in lambs, and to identify which species are infecting sheep in the eastern region of the state. This study was carried out from August 2009 to January 2010, and used 76 animals. These were divided into two treatment groups: one with common mineral salt, and the other with mineral salt enriched with 6% micronized decoquinate. Fecal samples and body weight measurements were taken every 14 days for parasitological diagnosis, weight gain follow-up and quantitative analysis. The study showed that there was a significant difference in OPG only at the 7th collection, but no significant difference in weight gain. The Eimeria species found were E. ahsata. E. crandallis. E. granulosa. E. intrincata. E. ovina. E. faurei. E. ovinoidalis. E. pallida and E. parva. It was concluded that addition of decoquinate to mineral salt gave rise to lower oocyst elimination, thus favoring eimeriosis control in sheep.

Use of coccidiostat in mineral salt and study on ovine eimeriosis / Uso de coccidiostático no sal mineral e estudo da eimeriose ovina

Coccidiosis is a serious obstacle to sheep production, which is becoming a limiting factor, especially with regard to lamb production. However, there are few studies on this parasite in the State of Rio Grande do Norte. The aim of this study was to evaluate the action of decoquinate, added to mineral salt, for controlling Eimeria infection in lambs, and to identify which species are infecting sheep in the eastern region of the state. This study was carried out from August 2009 to January 2010, and used 76 animals. These were divided into two treatment groups: one with common mineral salt, and the other with mineral salt enriched with 6% micronized decoquinate. Fecal samples and body weight measurements were taken every 14 days for parasitological diagnosis, weight gain follow-up and quantitative analysis. The study showed that there was a significant difference in OPG only at the 7th collection, but no significant difference in weight gain. The Eimeria species found were E. ahsata. E. crandallis. E. granulosa. E. intrincata. E. ovina. E. faurei. E. ovinoidalis. E. pallida and E. parva. It was concluded that addition of decoquinate to mineral salt gave rise to lower oocyst elimination, thus favoring eimeriosis control in sheep.

A coccidiose constitui-se num sério obstáculo à ovinocultura, a qual vem se tornando um fator limitante para a exploração, especialmente para a produção de cordeiros precoces. Porém, poucos são os estudos com esse parasito no Estado do Rio Grande do Norte. O objetivo deste trabalho foi avaliar a ação do decoquinato, adicionado ao sal mineral, no controle da infecção causada por parasitas do gênero Eimeria em cordeiros, e identificar quais as espécies infectam ovinos na região leste Potiguar. O trabalho foi desenvolvido entre agosto de 2009 e janeiro de 2010, e foram usados 76 animais, distribuídos em dois tratamentos, um com sal mineral comum e o outro com sal mineral enriquecido com decoquinato a 6% micronizado. Amostras fecais e pesagens dos animais foram feitas a cada 14 dias para o diagnóstico parasitológico, acompanhamento do ganho de peso ponderal e análise quantitativa. O estudo evidenciou que houve diferença significativa na redução do OoPG apenas na 7º semana de experimento, mas não houve diferenças significativas para ganho de peso dos animais. As espécies encontradas foram E. ahsata. E. crandallis. E. granulosa. E. intrincata. E. ovina. E. faurei. E. ovinoidalis. E. pallida . E. parva. Conclui-se que a adição de decoquinato ao sal mineral propiciou uma menor eliminação de oocistos favorecendo o controle da eimeriose ovina.

Ovine toxoplasmosis: transmission, clinical outcome and control.

Toxoplasma gondii is a significant cause of abortion in sheep. Infection is picked up from the environment and if initiated during pregnancy may cause fetal mortality. Infected sheep remain persistently infected with tissue cysts in brain and muscle (meat), and are also immune and would not be expected to abort again. The live tachyzoite vaccine (Toxovax) protects against abortion and this allows the suggestion that it may also reduce or prevent tissue cyst development in muscle. If this were so it raises the question of whether the vaccine could be used to make meat safer for human consumption.

Field study of the efficacy of halofuginone and decoquinate in the treatment of cryptosporidiosis in veal calves.

Ninety, seven- to 10-day-old calves were allocated to three groups of 30 and treated daily for seven days with either 100 microg/kg halofuginone hydrobromide or 2.5 mg/kg decoquinate orally or left untreated as controls. The levels of diarrhoea and dehydration were monitored daily for 28 days from the first day of treatment (day 0) and samples of faeces were collected on days 0, 7, 14, 21 and 28, to quantify the excretion of Cryptosporidium parvum oocysts. The calves were weighed on days 3 and 28. The treatments had no effect on the levels of diarrhoea or dehydration, the proportions of diarrhoeic calves or the proportions of calves shedding oocysts. However, unlike decoquinate, halofuginone significantly reduced the excretion of oocysts on day 7 (P<0.0001), and decoquinate increased the average daily weight gain of the calves (P=0.049).

Tracing the emergence of drug-resistance in coccidia (Eimeria spp.) of commercial broiler flocks medicated with decoquinate for the first time in the United Kingdom.

Decoquinate is a quinolone coccidiostat introduced during 1967 as an in-feed prophylactic for broiler chickens. Despite early drug-resistance problems and its age, the drug is still used commercially worldwide. Decoquinate here serves as a valuable model in a field study that addresses the dynamics and economic impact of the development of coccidial resistance to potent synthetic anticoccidial drugs. The results of this unique, hitherto unpublished, study on the initial emergence of resistance of avian coccidia (Eimeria spp.) to a new drug in the field may be of strategic value in the continued use of decoquinate or the introduction of new drugs. The commercial performance of the first 3-5 crops of broilers to be medicated with decoquinate on each of six farms was monitored during 14 months in 1968-1969, supplemented by assessments of the species, population dynamics and decoquinate-resistance of coccidia isolated from each farm. During the rearing of each flock in a single shed on each farm, oocysts were counted in fresh faecal samples collected on three occasions, and the species were identified by their morphology if possible, supported if necessary by the biological characteristics of infections in chickens. E. acervulina was the most common species, followed by E. mitis, E. maxima, E. tenella and E. praecox. E. brunetti occurred rarely, and E. necatrix was not found. Decoquinate-resistance was evident in several species during the rearing of the first decoquinate-medicated crop on each farm, although clinical coccidiosis did not occur. It was concluded that inherently resistant mutants of E. acervulina, E. brunetti, E. maxima, E. tenella, and probably also E. mitis and E. praecox, were selected from field populations by 6 weeks during their first exposure to decoquinate. During up to four more subsequent crops, cycling of resistant parasites stimulated host immunity, which had no obvious adverse impact on commercial performance. There was no apparent seasonal effect. A hypothesis is proposed to explain the sudden and rapid emergence of quinolone-resistance in the coccidia, and why bird health was not thereby compromised in these circumstances.

Efficacy of selected oral chemotherapeutants against Ichthyophthirius multifiliis (Ciliophora: Ophyroglenidae) infecting rainbow trout Oncorhynchus mykiss.

The chemotherapeutic efficacy of 6 in-feed compounds against Ichthyophthirius multifiliis Fouquet, 1876 was assessed using experimental infections of rainbow trout Oncorhynchus mykiss (Walbaum) fingerlings. Trial doses of 104 ppm amprolium hydrochloride or 65 ppm clopidol fed to fish for 10 d prior to infection significantly reduced the number of trophonts establishing in trout fingerlings by 62.0 and 35.2% respectively. In-feed treatments of infected trout with either 63 or 75 ppm amprolium hydrochloride, 92 ppm clopidol, or 38, 43 or 47 ppm salinomycin sodium for 10 d also significantly reduced the number of surviving trophonts by 77.6 and 32.2% for amprolium, 20.1% for clopidol and 80.2, 71.9 and 93.3% respectively for salinomycin sodium.

Treatment of dogs infected with Hepatozoon americanum: 53 cases (1989-1998).

OBJECTIVE: To determine clinical and pathologic findings before and after short-term (group 1) and long-term (group 2) treatment in dogs with Hepatozoon americanum infection. DESIGN: Retrospective study. ANIMALS: 53 dogs with H. americanum infection. PROCEDURE: Medical records of dogs that were treated for hepatozoonosis diagnosed on the basis of meront or merozoite stages in skeletal muscle were reviewed. RESULTS: Circulating gametocytes of H. americanum were identified in 12 of 53 dogs. Dogs were treated with various drugs, including toltrazuril, trimethoprim-sulfadiazine, clindamycin, pyrimethamine, and decoquinate. Mean WBC counts prior to treatment were 85,700 and 75,200 cells/microl in groups 1 and 2, respectively, and 1 month after initiation of treatment were 12,600 and 14,600 cells/microl, respectively. Initial response to treatment was excellent in all dogs. Twenty-three of 26 dogs in group 1 relapsed at least once and died within 2 years; mean (+/- SD) survival time was 12.6+/-2.2 months. Twenty-two of 27 group-2 dogs survived; 11 dogs had no clinical signs and were still receiving decoquinate (mean duration of treatment, 21 months), 11 dogs had no clinical signs after treatment for 14 months (range, 3 to 33 months; mean survival time, 39 months [range, 26 to 53 months]), 2 dogs were lost to follow-up, and 3 dogs were euthanatized because of severe disease. CONCLUSIONS AND CLINICAL RELEVANCE: Although no treatment effectively eliminated the tissue stages of H. americanum, treatment with trimethoprim-sulfadiazine, clindamycin, and pyrimethamine followed by long-term administration of decoquinate resulted in extended survival times and excellent quality of life.

Evaluation of decoquinate to treat experimental cryptosporidiosis in kids.

The purpose of this trial was to evaluate the effects of decoquinate at 2.5 mg/kg/day for 21 days to prevent an experimental cryptosporidiosis in kids. Twenty 1-day-old male kids (French Alpin), fed initially goat colostrum heated 1 h at 56 degrees C and fed twice daily with nonmedicated milk replacer, were assigned into 2 groups. Kids of both groups were orally inoculated with 10(6) Cryptosporidium parvum (D0 = inoculation day). Group A kids were kept as nonmedicated controls and group B kids were orally medicated with 2.5 mg/kg/day of decoquinate (Deccox L. Rhône Poulenc Animal Nutrition) for 21 days from D-3 to D17. The studied criteria were body weight gain, oocyst shedding and specific anti-C. parvum immune response. In group A, the inoculation was not followed by mortality; but only by diarrhea and high oocyst shedding. Decoquinate reduced the severity of cryptosporidiosis in group B kids. The treatment prevented episodes of diarrhea and weight gain decrease for the D0-D7 and D0-D14 disease periods but did not allow a better final weight gain. The oocyst shedding was decreased in number and in duration. This parasitic development has induced a specific anti-C. parvum immune response. This drug is well-tolerated by animals and may be recommended in the prevention of ruminant cryptosporidiosis, a disease which has very limited treatment options.

The mode of action of anticoccidial quinolones (6-decyloxy-4-hydroxyquinoline-3-carboxylates) in chickens.

The anticoccidial mode of action of quinolones (6-decyloxy-4-hydroxyquinoline-3-carboxylates) against Eimeria tenella and E. acervulina in chickens has been investigated, using decoquinate and M&B 15,584 as examples. The well known static effect on sporozoites of relatively high continuous drug concentrations in the food masked other components of the mode of action, newly described here. Lower concentrations of quinolones allowed sporozoites to continue their development. First-stage schizonts were susceptible to a secondary cidal effect, although later schizonts seemed to be rather refractory. Furthermore, the sporulation of oocysts produced by E. tenella that completed its life cycle in the presence of suboptimal concentrations of quinolones was inhibited: this probably reflects a drug effect on gametocytes. Quinolones were absorbed rapidly from the chicken intestine, probably in less than 1 h. Drug withdrawal experiments showed that quinolones persisted in chicken tissues at active concentrations for up to 48 h. Despite their static effect on sporozoites, they may nevertheless be expected to exert a therapeutic effect against drug-sensitive coccidia in interrupted regimes that allow the later cidal effect to come into play. This allows immunity to coccidiosis to develop in the presence of drug. These new results, with the previously available data have been combined in an updated account of the anticoccidial mode of action of quinolones in the chicken.

Efficacy of lasalocid and decoquinate against coccidiosis in naturally infected dairy calves.

A 56-d growth study compared the effects of lasalocid and decoquinate, or a combination of the two, on rate of gain and control of naturally occurring coccidiosis in weaned Holstein calves. Sixty-four calves (mean BW of 188 kg; age 16 wk) were blocked by BW and degree of oocyst shedding and assigned randomly to one of four treatments with 4 calves per pen and 4 pens per treatment. Treatment groups included an unmedicated control group, lasalocid at 1 mg/kg of BW, decoquinate at .5 mg/kg of BW, or lasalocid plus decoquinate. For the combination treatment, decoquinate was fed at the recommended rate for 28 d, followed by lasalocid for the remaining 28 d of the study. Diets were based on dry-rolled corn and haylage and were fed once daily for ad libitum feed consumption. Calves were weighed weekly, and feces were collected for quantitation of oocyst shedding. Oocyst shedding was low, and clinical coccidiosis was not observed. However, unmedicated calves shed oocysts at a higher rate than medicated calves. Small differences were found among treatments on overall rate of gain and gain efficiency. There was little advantage in gain or performance when calves with subclinical coccidiosis were medicated with anticoccidial agents.

In vivo expression of in vitro anticoccidial activity.

Large-scale screening has led to the identification of several experimental compounds that have very potent intrinsic activity against coccidia, but the lack of translation to in vivo efficacy has been a major hurdle in developing such leads into effective new drugs. We developed methods to explore the impact of oral availability and appropriate distribution in tissue, both of which are potentially important factors in the expression of activity in vivo. For the compounds that we examined, neither oral absorption nor distribution to the site of infection appeared to be the critical barrier to in vivo expression of intrinsic anticoccidial activity. Elucidation of the nature of additional factors that might be involved could assist greatly in the identification of useful new anticoccidial agents.

Evaluation of decoquinate or lasalocid against coccidiosis from natural exposure in neonatal dairy calves.

Forty-one Holstein and Brown Swiss calves were raised as herd replacements under conditions in which they were allowed natural exposure to sporulated coccidial oocysts at a very early age. Two compounds previously shown to have anticoccidial efficacies, decoquinate and lasalocid, were used for this study. Calves were assigned randomly at birth to one of the treatments: decoquinate (approximately .5 mg/kg of BW) or lasalocid (approximately 1.0 mg/kg of BW) or to remain as unmedicated controls through 16 or 24 wk of age. Counts of fecal oocysts were reduced in the calves fed decoquinate for wk 4 to 8 and for both treated groups for wk 9 to 24. Calves fed decoquinate had increased BW, heart girth, and height at withers during wk 5 to 8. Both treated groups had higher gains than untreated calves during wk 12 to 16 with the decoquinate group larger than the lasalocid group. Feeding an anticoccidial compound to newborn calves reduced severity of coccidiosis when early natural exposure occurred.

Influence of decoquinate fed to neonatal dairy calves on early and conventional weaning systems.

Forty-four Holstein calves were assigned randomly to treatments in a 2 x 2 factorial arrangement of weaning age (4 or 7 wk) and coccidiostat (treatment or control). The objective of this study was to compare the effectiveness of a coccidiostat, decoquinate, on health parameters and growth of neonatal dairy calves on early and conventional weaning systems. Calves weaned at 4 wk had greater intakes of grain in wk 5 to 7 than did calves weaned at 7 wk. Differences in intakes between weaning groups were not apparent from wk 8 to 24. Fecal coccidia oocyst counts were not affected by age at weaning but were affected by coccidiostat feeding at the rate of .5 mg/kg BW/d offered from 3 d of age and throughout the trial. No effects due to age at weaning or coccidiostat treatment were found in plasma glucose, urea N, and minerals (Ca, P, Na, Cl, K, Mg). Growth parameters were significantly increased in treated animals. Total BW was increased (wk 9 to 24) in treated over control calves (127.3 versus 118.5 kg). Height at withers was also increased in treated calves (95.0 vs. 92.8 cm). Coccidiosis treatment increased growth of dairy calves from 9 to 24 wk, but no interactions were found between coccidiosis treatment and age at weaning.

Effects of inoculations with Eimeria zuernii on young calves treated with decoquinate or narasin with or without dexamethasone.

Sixteen 7-week-old Holstein male calves were inoculated with sporulated oocysts of Eimeria zuernii. Four calves (controls) were euthanatized and necropsied at 14 and 20 days after inoculation (DAI). Two calves were treated with 20 mg of dexamethasone (IM) on 13, 14, and 15 DAI and euthanatized and necropsied 17 DAI and 2 calves were given similar treatments and necropsied 20 DAI. The 8 other calves were euthanatized and necropsied 20 DAI. Two were started on the anticoccidial drug decoquinate in feed 13 DAI; 2 others were given decoquinate on the same schedule plus dexamethasone on 13,14, and 15 DAI. Two calves were given the antibiotic narasin in feed beginning 13 DAI and 2 calves were given parasin on the same schedule plus dexamethasone on 13,14, and 15 DAI. All calves, except 2 controls necropsied 14 DAI and 4 calves given decoquinate, discharged moderate-to-large numbers of oocysts in feces and had moderate-to-serve changes in fecal consistency. Histologic examinations revealed large numbers of endogenous stages in tissues of calves treated or not treated with dexamethasone. Few endogenous stages were observed in tissues from calves that were given decoquinate or decoquinate plus dexamethasone. Calves given narasin or narasin plus dexamethasone had moderate-to-large numbers of endogenous stages in the tissues.

Evaluation of lasalocid and decoquinate against coccidiosis resulting from natural exposure in weaned dairy calves.

Eighteen female Holstein calves, raised as natural herd additions under conditions typical of a well-managed midwestern United States dairy farm, were used in a natural-exposure study to determine the anticoccidial efficacies of lasalocid and decoquinate. Calves were allotted to 6 treatment blocks of 3 calves each as they were weaned. Within each block, calves were randomly assigned to be given either lasalocid or decoquinate or to remain as a nonmedicated control. Calves were given medication for 90 days and remained separated from other calves for 120 days. Adjusted weight gains were consistently greater in calves that were given medication; however, differences were not statistically significant. Fecal specimens were obtained from calves at weekly intervals during the study. Overall, oocyst shedding was low. During the medication period, quantitative mean fecal shedding of oocysts was reduced eightfold in calves given decoquinate and four-fold in calves given lasalocid, as compared with nonmedicated control calves. During the period following the medication period, calves that had been controls shed fewer oocysts than did calves that had previously been given medication. A pairwise comparison of the proportion of specimens that were oocyst-positive was made to assess qualitative oocyst shedding among treatment groups. During the medication period, qualitative oocyst shedding (all species, Eimeria bovis, E zuernii, species other than E bovis and E zuernii) was greater in controls than in either lasalocid-or decoquinate-treated groups. Like-wise, lasalocid-medicated calves shed oocysts more frequently than did the decoquinate-medicated group. After medication, qualitative findings were reversed. Little diarrhea was noticed in treatment or control calves during the study.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of intermittent and continuous administration of decoquinate on bovine coccidiosis in male calves.

Male Holstein calves were each inoculated with 350,000 sporulated oocysts of Eimeria bovis. Two calves were given decoquinate (0.5 mg/kg of body weight) continuously in dry feed for 29 days, and 2 calves each were given 0.5, 1, or 1.5 mg of decoquinate/kg on an every 2nd-or 3rd-day schedule for 29 days. Calves given decoquinate continuously did not discharge oocysts but had slightly loose feces. In general, the number of oocysts discharged increased and fecal consistency decreased as the time between feeding of medicated feed increased. Calves given 0.5 or 1.5 mg of decoquinate/kg every 3rd day discharged more oocysts and had more diarrhea than did calves given 1 mg of decoquinate/kg every 3rd day. At postinoculation day 29, calves were euthanatized. At necropsy, intestinal tissues of calves given decoquinate were mostly normal. Apparently, reduced infections along with the elapsed time were sufficient to resolve most intestinal lesions caused by the coccidia. Decoquinate was most effective when fed continuously at 0.5 mg/kg. However, when fed at 1 or 1.5 mg of decoquinate/kg every 2nd day or 1.5 mg of decoquinate/kg every 3rd day, oocyst production was reduced and clinical coccidiosis was prevented.