Anticoccidial drugs of the livestock industry

Coccidiosis is a parasitic disease of a wide variety of animals caused by coccidian protozoa. The coccidia are responsible for major economic losses of the livestock industry. For example, the annual cost due to coccidiosis to the global poultry industry has been estimated to exceed US$ 3 billion annually. Currently available drugs for the control of this disease are either polyether ionophorous antibiotics that are derived from fermentation products, or synthetic compounds, produced by chemical synthesis. Unfortunately, no new drugs in either category have been approved for use for decades. Resistance has been documented for all those of the drugs currently employed and therefore the discovery of novel drugs with unique modes of action is imperative if chemotherapy is to remain the principal means to control this disease. This chapter aims to give an overview of the efficacy and mode of action of the current compounds used to control coccidiosis in livestock and provides a brief outlook of research needs for the future.

Method development for the analysis of ionophore antimicrobials in dairy manure to assess removal within a membrane-based treatment system

Ionophore antimicrobials are heavily used in the livestock industries, both for preventing animal infection by coccidia protozoa and for increasing feed efficiency. Ionophores are excreted mostly unmetabolized and are released into the environment when manure is land-applied to fertilize croplands. Here, an analytical method was optimized to study the occurrences of five ionophore residues (monensin, lasalocid, maduramycin, salinomycin, and narasin) in dairy manure after solid-liquid separation and further treatment of the liquid manure by a membrane-based treatment system. Ionophore residues from the separated solid manure (dewatered manure) and suspended solids of manure slurry samples were extracted using ultrasonication with methanol, followed by sample clean-up using solid phase extraction (SPE) and subsequent analysis via liquid chromatography-tandem mass spectrometry (LC-MS/MS). The use of an ethyl acetate and methanol (1:1 v:v) mixture as an SPE eluent resulted in higher recoveries and lower method quantitation limits (MQL), when compared to using methanol. Overall recoveries from separated solid manure ranged from 73 to 134%. Liquid manure fractions were diluted with Nanopure™ water and cleaned up using SPE, where recoveries ranged from 51 to 100%. The developed extraction and LC-MS/MS methods were applied to analyze dairy manure samples subjected to an advanced manure treatment process involving a membrane-based filtration step (reverse osmosis). Monensin and lasalocid were detected at higher concentrations in the suspended solid fractions (4.40-420 ng/g for lasalocid and 85-1950 ng/g for monensin) compared to the liquid fractions (<MQL - 132 ng/mL for monensin). Monensin residues remained in liquid manure treated with reverse osmosis where residual concentrations were reduced to near 8 ng/mL.

Molecular Characterization of Coccidia Associated with an Epizootic in Green Sea Turtles (Chelonia mydas) in South East Queensland, Australia

In the spring of 2014, mass mortalities among wild green sea turtles occurred off the coast of south-east Queensland, Australia. The suspected causative agent was Caryospora cheloniae, an eimeriid coccidian implicated in previous epizootics. Necropsies were undertaken on a subset of 11 dead turtles, with subsequent histopathology and molecular analyses. All turtles returned positive PCR results for coccidial infection in various tissues; these included the brain, gastrointestinal tract, lung, kidney and thyroid. Granulomatous encephalitis was consistently observed, as well as enteritis and, less frequently, thyroiditis and nephritis. Sequencing and phylogenetic analyses indicated the presence of two distinct coccidian genotypes, presumably separate species—one associated with the brain, gastrointestinal tract and lung, and the second with the thyroid and kidney. Maximum likelihood and Bayesian inference analyses placed the first genotype closest to the lankesterellid genus Schellackia, rather than in the Eimeriidae, while the second was paraphyletic to the eimeriids. Presence of coccidial stages in extra-intestinal tissues of the primary host raises questions about the potential presence of intermediate or paratenic hosts within the life cycles, as well as their current placement relative to the genus Caryospora. This study represents the first genetic characterization of this emerging disease agent in green sea turtles, an endangered species, and has relevance for life-cycle elucidation and future development of diagnostics.

Disinfection efficacy of sodium dichloroisocyanurate (NADCC) against common food-borne intestinal protozoa

The present study was conducted to investigate the efficacy of sodium dichloroisocyanurate (NaDCC) on the infective stages of common food-borne intestinal protozoa; Entamoeba histolytica (E. histolytica), Giardia lamblia (G. lamblia), Cryptosporidium, Cyclospora and Microsporidia; beside its effect on raw green vegetables and fruits. Parasites, isolated from stool of patients with diarrhea or dysentery, were exposed to NaDCC solution (1g/l) for one and two hours. Disinfection effect of NaDCC was assessed by in-vitro viability, using trypan blue stain, and infectivity bioassay in laboratory animals as indicated by fecal and intestinal parasitic counts. Raw vegetables and fruits were dipped in NaDCC solution in the same concentration and exposure time as used for treatment of the parasites. Results revealed statistically significant reductions in viability and infectivity of all examined parasites indicating their susceptibility to NaDCC. Relative variations in susceptibility were revealed; E. histolytica and G. lamblia were most susceptible (100% reduction) followed by Microsporidia then Cryptospridium and Cyclospora. NaDCC did not affect the consistency, color, taste or flavor of raw green vegetables and fruits. The proved efficacy of NaDCC, in cheap and convenient dry tablet form, makes it a promising tool in decontaminating raw vegetables and fruits from food-borne protozoan parasites at household and restaurant levels as well as in catering and fresh produce industry. It is also recommended for disinfection of food preparation surfaces and equipment.

Dietary betaine affect duodenal histology of broilers challenged with a mixed coccidial infection

The purpose of this research was to investigate effect of dietary betaine on intestinal morphology after an experimental coccidiosis. Hence a total of 189 male and female broiler chicks were randomly assigned to 9 floor cages. Chicks were fed a basal diet supplemented with 0, 0.6 or 1.2 g kg(-1) betaine. All birds were inoculated orally with Eimeria oocysts on day 28. Duodenal morphology parameters and lesions were scored by microscopic observation on intestine samples which were taken at day 42 of age. Adding 1.2 g kg(-1) betaine to diet diminished intestinal lesions (p < 0.05). Dietary supplementation with 0.6 or 1.2 g kg(-1) betaine significantly (p < 0.01) increased intraepithelial lymphocytes as well. Level of additive betaine had no effect on the ratio of villus height/crypt depth or villus surface area. Lamina propria of duodenum became thicker in the intestine of chickens which received more supplemental betaine via their diet. In conclusion, since the number of intraepithelial lymphocytes and thickness of lamina propria represent the condition of gut immune response, it seems that dietary betaine may immunomodulate the gastrointestinal tract of broilers. In addition, betaine effect on villus morphology measured later in life differed from what had been measured already earlier in life of the chicks.

The methylerythritol phosphate pathway for isoprenoid biosynthesis in coccidia: presence and sensitivity to fosmidomycin

The apicoplast is a recently discovered, plastid-like organelle present in most apicomplexa. The methylerythritol phosphate (MEP) pathway involved in isoprenoid biosynthesis is one of the metabolic pathways associated with the apicoplast, and is a new promising therapeutic target in Plasmodium falciparum. Here, we check the presence of isoprenoid genes in four coccidian parasites according to genome database searches. Cryptosporidium parvum and C. hominis, which have no plastid genome, lack the MEP pathway. In contrast, gene expression studies suggest that this metabolic pathway is present in several development stages of Eimeria tenella and in tachyzoites of Toxoplasma gondii. We studied the potential of fosmidomycin, an antimalarial drug blocking the MEP pathway, to inhibit E. tenella and T. gondii growth in vitro. The drug was poorly effective even at high concentrations. Thus, both fosmidomycin sensitivity and isoprenoid metabolism differs substantially between apicomplexan species.

Evaluation of herbal coccidiostat 'Coxynil' in broiler

Anticoccidial efficacy of "Coxynil" a polyherbal preparation was tested against Eimeria tenella in broilers. Body weight of birds challenged with E. tenella in Coxynil treated groups was higher as compared to Coxynil untreated. Oocyst out put, lesion score, HI titres against New Castle disease virus were significantly higher in Coxynil supplemented groups in comparison to Coxynil un-supplemented groups. Examination of ceaca of the birds, revealed that the Coxynil interfered with life cycle of coccidia. The typical second generation schizonts were absent in ceacal section of Coxynil treated groups. The results indicate that Coxynil is effective herbal coccidiostat.

Recent advances in the search for new anti-coccidial drugs

Coccidia provide a rich hunting ground for drug-designers, as there are significant biochemical differences between the parasites and their hosts. Recent years have brought the discovery of the plastid and its possible metabolic machinery, characterisation of acidocalcisomes, reports on the apparent absence from some coccidia of a typical mitochondrion, and the discovery of the mannitol cycle and shikimate pathway in the parasites. Moreover, modern technologies such as genomics and proteomics are bringing new insights into the biochemistry of coccidia and highlighting possible drug targets in abundance. A major issue for would-be drug discoverers is to decide upon the targets to prioritise. This review provides an update on recent findings on how coccidia differ biochemically from vertebrates. It includes discoveries within coccidian parasites themselves but also uses findings in Plasmodium to provide an overview of biochemical features that may be characteristics of many apicomplexan parasites and so potential targets for broad-spectrum drugs.

Chemotherapeutic approaches to protozoa: Coccidiae--current level of knowledge and outlook

Progress in the treatment and prophylaxis of cyst-forming coccidial infections (Neospora, Sarcocystis Toxoplasma) and Cryptosporidium infections has been limited (Table 1: Haberkorn 1996: Croft 1997: Wang 1997). However, new possibilities have been opened up in the treatment of Eimeria-induced coccidiosis in poultry and mammals. due to improvements in treatment and, or metaphylaxis. A new polyether antibiotic. semduramycin, has recently been added to the range of effective prophylactic preparations. The development of resistance to anticoccidial agents is now posing similar problems to those encountered with malaria, coccidiosis in poultry being particularly affected. Because no new active ingredient from a new family of chemical substances has been developed for more than 10 years, the following approaches are being adopted to get round this problem: the use of older preparations which have not been used for a long time, the introduction of combinations such as narasin nicarbazin or methyl benzoquate clopidol and the alternating use of anticoccidial agents in rotation and shuttle programmes. The goal of a real alternative, i.e. vaccination, has been achieved to a certain extent in the form of live vaccines for laying hens and broiler breeders and is being practiced in some countries.

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.

Effects of ozone, chlorine dioxide, chlorine, and monochloramine on Cryptosporidium parvum oocyst viability

Purified Cryptosporidium parvum oocysts were exposed to ozone, chlorine dioxide, chlorine, and monochloramine. Excystation and mouse infectivity were comparatively evaluated to assess oocyst viability. Ozone and chlorine dioxide more effectively inactivated oocysts than chlorine and monochloramine did. Greater than 90% inactivation as measured by infectivity was achieved by treating oocysts with 1 ppm of ozone (1 mg/liter) for 5 min. Exposure to 1.3 ppm of chlorine dioxide yielded 90% inactivation after 1 h, while 80 ppm of chlorine and 80 ppm of monochloramine required approximately 90 min for 90% inactivation. The data indicate that C. parvum oocysts are 30 times more resistant to ozone and 14 times more resistant to chlorine dioxide than Giardia cysts exposed to these disinfectants under the same conditions. With the possible exception of ozone, the use of disinfectants alone should not be expected to inactivate C. parvum oocysts in drinking water.

Effect of disinfection of drinking water with ozone or chlorine dioxide on survival of Cryptosporidium parvum oocysts

Demineralized water was seeded with controlled numbers of oocysts of Cryptosporidium parvum purified from fresh calf feces and subjected to different treatments with ozone or chlorine dioxide. The disinfectants were neutralized by sodium thiosulfate, and neonatal mice were inoculated intragastrically and sacrificed 7 days later for enumeration of oocyst production. Preliminary trials indicated that a minimum infection level of 1,000 oocysts (0.1-ml inoculum) per mouse was necessary to induce 100% infection. Treatment of water containing 10(4) oocysts per ml with 1.11 mg of ozone per liter (concentration at time zero [C0]) for 6 min totally eliminated the infectivity of the oocysts for neonatal mice. A level of 2.27 mg of ozone per liter (C0) was necessary to inactivate water containing 5 x 10(5) oocysts per ml within 8 min. Also, 0.4 mg of chlorine dioxide per liter (C0) significantly reduced infectivity within 15 min of contact, although some oocysts remained viable.

Response of 21 Canadian field isolates of chicken coccidia to commercial anticoccidial drugs

Coccidia were isolated from 30 broiler farms in major poultry-producing provinces of Canada; 21 mixed-species isolates were tested for sensitivity to anticoccidial drugs. Eimeria acervulina was identified in 20 samples, E. maxima in 15, and E. tenella in 10 of the mixed-species isolates. On the basis of weight gain after infection, 3 isolates were judged sensitive to amprolium, 5 to monensin, 9 to salinomycin, 14 to lasalocid, 19 to halofuginone, and 20 to nicarbazin. Similar trends in sensitivity/tolerance were identified from the percent reduction of intestinal lesion scores of medicated birds compared with scores of unmedicated, infected controls. These results were consistent with the previous pattern of use of anticoccidial drugs in commercial poultry in Canada.

16-Deethylindanomycin (A83094A), a novel pyrrole-ether antibiotic produced by a strain of Streptomyces setonii. Taxonomy, fermentation, isolation and characterization

16-Deethylindanomycin (A83094A) is a novel pyrrole-ether antibiotic produced by a strain of Streptomyces setonii. The antibiotic, which is structurally similar to indanomycin (X-14547A), is active in vitro against Gram-positive bacteria as well as coccidia.

Efficacy of a pentaiodide resin disinfectant on Cryptosporidium parvum (Apicomplexa: Cryptosporidiidae) oocysts in vitro

The resin-I5 column developed at Kansas State University was tested for efficacy against oocysts of Cryptosporidium parvum (Apicomplexa: Cryptosporidiidae). Cesium chloride gradient-purified oocysts were passed through 1.0-cm-diameter columns with lengths of 2.5, 5.0, and 10.0 cm at 23 C. Following column passage, oocyst viability was determined both in vitro by excystation and in vivo by the ability to establish infections in suckling mice. Oocysts were found to be retained by the pentaiodide resin in a linear fashion, probably by electrostatic interactions. Linear regression analysis revealed 100% of the oocysts should be removed in such a manner using a column length of greater than or equal to 25.7 cm. When compared to untreated control oocysts, less than 12% of the oocysts that passed through the columns appeared to be affected by the resin, as assessed by excystation. Inoculation of suckling mice with these column-treated oocysts supported the excystation data and revealed the coccidian to be viable. These results indicate that oocysts of C. parvum are retained on the pentaiodide column in a 1-hit manner and that, although killing of parasites may occur within the column, the greatest effect that the column may have on the parasite is as an electrostatic retention device.

Prevention and control of coccidiosis in goats with decoquinate

Decoquinate was evaluated as a coccidiostat in domestic goats. Fifty goats less than 4 months of age were assigned to 5 groups (pens) of 10 goats each and were treated for 87 days with 0 (control), 0.3, 0.5, 1.0, or 4.0 mg of decoquinate in feed/kg of body weight. Goats were inoculated orally weight. Goats were inoculated orally with 30,000 oocysts, mainly Eimeria christenseni (74%) and E ninakohlyakimovae (20%) on day 19. Nontreated goats developed profuse watery diarrhea and tenesmus and gained weight poorly; 2 died. Treated goats did not develop clinical coccidiosis and gained significantly more weight (P less than 0.05), regardless of the dose used. Treated goats also had significantly fewer (P less than 0.05) oocysts in feces than did nontreated controls. Oocyst numbers were inversely related to dose; a more rapid decrease in oocyst numbers occurred as the dose was increased. At the doses used, decoquinate was safe in goats and was an effective drug for the prevention of clinical coccidiosis.

Drug sensitivity of coccidia from broiler breeder pullets and from broilers in the same integrated company

Coccidia isolated from 12 breeder pullet farms and 18 broiler farms were tested for sensitivity to anticoccidial drugs. The species Eimeria acervulina, E. maxima, and E. tenella were common in the isolates and were fully pathogenic. Broiler coccidia were generally resistant to Zoalene but sensitive to nicarbazin. About half of the isolates had reduced sensitivity to amprolium and monensin. Most of the breeder pullet coccidia were resistant to Zoalene and amprolium, but almost all were highly sensitive to nicarbazin and monensin. There was some difference in responses of broiler isolates to various ionophores. Isolates responded best to salinomycin and lasalocid, which had not been previously used on the farms. Monensin controlled coccidia slightly better when given at 120 ppm than when given at 100 ppm. These results suggest that broiler coccidia have lost some responsiveness to ionophores as a result of long-term exposure, but that breeder pullet coccidia, which have never been exposed to those drugs, have retained their sensitivity. Resistance or sensitivity to other drugs was consistent with history of use: more isolates were sensitive to older drugs that had not been used for several years than was reported in previous surveys.

[The effect of a single disinfection of a farm on cryptosporidiosis infection in calves]

The disinfection of a farm with Dikonit (active substance: sodium dichlorocyanuran) exerted no significant influence on the course of the spreading of cryptosporidiosis infections in newborn calves. The oocysts of Cryptosporidium sp., isolated from the faeces of a spontaneously infected calf and left in a 2.5% disinfecting solution of Dikonit under laboratory conditions for four hours, did not lose their viability. Laboratory mice experimentally infected with these "disinfected" oocysts, began to produce oocysts of Cryptosporidium sp. the sixth day from infection. The findings of different developmental stages of this protozoan obtained during the histological examination of the intestinal tissue of test mice are also considered as evidence of successful experimental infection. The cryptosporidium-free period which lasted only 14 days from disinfection was mainly due to thorough mechanical cleaning of the area where the calves were kept after birth. This is also proved by the results of the examination of old residues of calf faeces scraped from the floors: only individual individual oocysts of Cryptosporidium sp. were found in these samples.

[Effects of Mebendazole and Cambendazole on enterohelminths in pigs]

Mebendazole, administered at a dose of 30 mg active substance per 1 kg of feed, was found to have 100% effectiveness on Ascaris suum and Cambendazole, administered at a dose of 1.5 g per 1 kg of liver weight, showed the same effectiveness in the control of Ascaris suum and Oesophagostomum dentatum. The effectiveness of both drugs on Trichocephalus suis and Strongyloides ransomi was low. Mebendazole and Cambendazole can be recommended for mass dehelminthization of pigs in affected stocks. Helminthoovoscopical examination of sows and fattened pigs showed an 88.6% extensity of invasion in sows, and a 28.3% and 33.9% extensity in three- and five-month-old pigs, respectively. Coccidiosis was found in 51.4% of the sows and Balantidium coli had an occurrence rate of 80.7 to 98.2%.