Ovine coccidiosis: effect of the antibiotic monensin against Eimeria ninakohlyakimovae and other naturally occurring coccidia of sheep

Sixteen female and 16 male lambs were used in 4 groups to determine the effect of monensin on naturally occurring and experimentally induced coccidiosis. Determinations of numbers of oocysts discharged, quantities of feces discharged, feed consumption, and weight gain were made for female and male lambs in each group. The effect of experimentally induced and naturally occurring coccidiosis on the performance of each group was compared. Nonmedicated lambs, experimentally inoculated with Eimeria ninakohlyakimovae, gained the least weight. Lambs naturally infected with coccidia gained next best and inoculated lambs, in 2 groups medicated with 10 or 20 ppm of monensin in the feed, gained best. The average net gain for the 4 groups was 7.8, 9.7, 13.7, and 13.7 kg. The medicated lambs required less feed/kilogram of weight gain than did the nonmedicated lambs. In general, female lambs were more severely affected by the coccidia, consumed more feed, produced more fecal material, and gained less weight than did male lambs.     

Pathogenic Effiects of the Coccidium Eimeria ninakohlyakimovae in Goats

Twenty-four coccidia-free goats were reared artificially in indoor cages and allocated to 6 groups of 4 animals each. At 20 days of age, goats in groups 1–3 received 10⁴,10⁵ and 10⁶ sporulated oocysts of Eimeria ninakohlyakimovae per goat, respectively, each as a single dose. Goats in group 4 received daily doses increasing over a 3-week period, starting with 100/day for the first week, followed by 1000, and 10 000/day in weeks 2, 3, respectively. Goats in group 5 received 10⁴ oocysts following a challenge dose of 10⁶ oocysts on day 32. Goats in group 6 were kept as uninoculated controls. Infected animals showed diarrhoea and weight loss. Goats in group 4 showed longer periods of diarrhoea and patency than other infected goats. Goats in group 5 showed the same severe clinical signs as those in group 3 but produced very low oocyst output after a challenge dose. The diarrhoea was associated with a reduction in alkaline phosphatase activity and increases in packed cell volume and haemoglobin. No significant differences were found in serum aspartate aminotransferase, alanine aminotransferase, total protein, albumin, globulin, Na⁺, K⁺,Cl⁻ between groups during 48 days after inoculation. There were no serum enzyme indications of damage to the liver. Histological examination performed 100 days after inoculation revealed that inoculated goats had mild subacute to chronic proliferative enteritis in the lower small intestine and the large intestine, and the mesenteric lymph nodes, gallbladders and livers also showed slight histological lesions. The results showed that E. ninakohlyakimovae was highly pathogenic.     

Natural and experimental infections of lambs with Mycoplasma ovipneumoniae

Mycoplasma (M.) ovipneumoniae was isolated pure or mixed with bacteria from 47 lungs of lambs of 14 in 22 tested flocks. M. ovipneumoniae was obtained as pure culture in cases of mild bronchopneumonia. Experimental intratracheal or intranasal infection caused several days of rising body temperature above 39.7 degrees C. Nasal discharge, coughing, and dyspnea did not occur. M. ovipneumoniae was successfully re-isolated from nasal swabs, beginning 2 d from infection. Lobular catarrhal bronchopneumonia was established by postmortem examinations, 10-14 d from infection, and M. ovipneumoniae was re-isolated from the lungs. Histological patterns of lungs were characterised by interstitial cell reactions.     

Efficacy of salinomycin in treatment of experimental Eimeria bovis infections in calves

The efficacy of salinomycin for treatment of experimental Eimeria bovis infections was evaluated. In experiment 1, 18 calves were placed into four groups. Group 1 calves were nonmedicated controls; groups 2, 3, and 4 calves were given salinomycin (0.33, 0.66, and 1.00 mg/kg of body weight, respectively) in daily oral divided doses starting 2 or 3 days prior to E bovis inoculations and continuing until postinoculation day (PID) 21. Calves treated with 0.66 and 1.00 mg/kg (groups 3 and 4) passed substantially fewer oocysts than did control calves (group 1) or calves treated with 0.33 mg/kg (group 2). Group 1 control calves had typical signs of severe E bovis infections, whereas signs of infection in medicated calves were almost nonexistant. Experiment 2 was conducted as before, with 15 calves. Group 5 calves were nonmedicated controls; groups 6, 7, and 8 calves were treated with 0.5, 1.0, and 2.0 mg/kg, respectively. All group 8 calves and three of four group 7 calves had nearly complete suppression of oocyst excretions. The severity of the disease in the group 5 control calves was not as extensive as it was in group 1 control calves. In experiment 3, 16 calves were used. Group 9 calves were nonmedicated controls, whereas other calves were given salinomycin (2.0 mg/kg) during PID 3 to 7 (group 10), PID 8 to 12 (group 11), and PID 13 to 17 (group 12). Salinomycin therapy in group 2 calves resulted in substantial reductions in oocyst excretions and clinical signs.     

Influence of coccidiosis on growth rate and feed conversion in broilers after experimental infections with Eimeria acervulina and Eimeria maxima

Under experimental conditions, the effects of subclinical Eimeria (E.) acervulina and E. maxima infections on growth and feed conversion in broilers of different ages were analysed. It was concluded that infection with E. acervulina and E. maxima led to a process which was independent of the age at which the birds were infected. The infection adversely affected growth and feed conversion for 2 to 3 weeks, followed by a recovery period of 2 to 3 weeks when compensatory growth took place. From this study it may be concluded that subclinical coccidiosis in the first weeks of life and in the last week of life of broilers does not lead to appreciable damage on growth and feed conversion. Since coccidiosis cannot be avoided in practice, systems in which broilers contact subclinical coccidiosis either in the first weeks of life or in the last week of life should be aimed for. It is suggested that in a coccidiostat programme an efficient anticoccidiosis agent is particularly desirable in the 3rd and 2nd week before slaughter. Examinations performed one week or less before slaughter can hardly be justified, on the grounds that there is a risk of a negative effect on growth an feed conversion due to subclinical coccidiosis.     

Effects of monensin on monovalent ion metabolism and tissue concentrations in lambs

A study consisting of two trials was conducted to determine the effects of monensin on the apparent absorption and retention of sodium (Na) and potassium (K) and to examine changes in tissue and ruminal fluid concentrations of these minerals in lambs. Eight lambs (39 kg) were used in trial 1 and 10 lambs (37 kg) were used in trial 2. Animals were used in randomized block designs, blocked by weight, and fed a high concentrate diet with or without 20 mg/kg monensin. Trials began with a dietary adjustment period lasting 18 d in trial 1 and 21 d in trial 2. Animals were then placed in metabolism stalls for a 10-d stall adjustment period followed by a 12-d collection period. Collections for mineral balance were made during the first 10 d of the collection period. Blood and ruminal fluid samples were obtained on d 11 of the collection period. Lambs were slaughtered on d 12 of the collection period and tissue samples were collected. Sodium retention decreased (P less than .05) 86.2% when monensin was fed. Apparent K absorption increased (P less than .05) 16.7%, while K retention increased (P less than .10) 52.6% when monensin was fed. In lambs fed monensin, ileal Na decreased (P less than .10) 13.8%. These results indicate that dietary monensin alters the metabolism of Na and K in lambs.     

Effects of leucocyte extract, levamisole and sulphadimidine on natural coccidial infections (Eimeria spp.) in young lambs

The efficacy of leucocyte extract (LE) and sulphadimidine in preventing coccidiosis in naturally infected lambs on pasture was evaluated in 3 separate experiments, whereas the prophylactic effect of levamisole was studied in 1 of the experiments. LE prepared from ewes immune to coccidia (Eimeria spp.) was administered either intravenously or intraperitoneally to young lambs 7, 5, or 2 days before they were turned out on pastures contaminated with coccidia. In all experiments, LE failed to transfer protective immunity to the lambs against the first coccidial infection on pasture. The LE preparations used apparently had an immunosuppressive effect, which resulted in more severe clinical signs of coccidiosis in the recipients. The lambs given LE showed a higher incidence of diarrhoea, a poorer weight gain, a higher mortality, and a higher oocyst output than the untreated control lambs. In lambs treated with sulphadimidine at 200 mg/kg on days 12, 13, and 14 after turnout there was a reduced severity of the coccidial infections in all experiments. The sulphadimidine-treated lambs had better weight gains and passed fewer oocysts than the controls during the third and fourth week after turnout, but some of them developed diarrhoea. Lambs treated with levamisole at 2 mg/kg 2 days before turnout, at turnout, and 2 days after turnout were more severely affected by the first coccidial infection on pasture than the controls.To study the lambs’ immunity against a heavy challenge infection with coccidia as compared with their immunity against the natural reinfection on pasture, some of the lambs from the original groups (untreated, sulphadimidine-treated, LE-treated) were each inoculated with 2 mill. Eimeria spp. oocysts about 6 weeks after turnout. The oocyst counts of the challenged lambs, except the LE-treated lambs, increased to a new peak 19–20 days after challenge. The challenge infection caused a softening of the faeces and a marked depression in weight gain in all challenged groups of lambs, mainly between days 10 and 17 after challenge. The lambs were thus only partially immune to coccidia after the first coccidial infection on pasture. The lambs treated with either LE or sulphadimidine in connection with the first coccidial infection on pasture were not appreciably more susceptible to the challenge infection than the untreated lambs.     

Interaction of aflatoxin with Eimeria tenella infection and monensin in young broiler chickens.

Young broiler chicks inoculated with Eimeria tenella and given a diet containing 2.5 mug aflatoxin/g had significantly higher mortality than birds with aflatoxicosis or coccidiosis alone or uninoculated controls. This effect was seen even when a light coccidial infection alone did not increase mortality or cause weight depression. In addition this higher mortality with the combination began earleir and occurred at a higher rate than did mortality from aflatoxin or cecal coccidiosis alone. Dietary monensin sodium (99 umg/g) did not completely prevent mortality and weight depression when aflatoxin and E. tenella were in combination. Aflatoxin and E. tenella singly significantly depressed three-week body weights; however, the depression was most severe when the two were in combination. Both dietary aflatoxin and E. tenella significantly reduced hemoglobin, packed cell volume, and plasma pigmentation, and in combination resulted in more severely reduced hemoglobin, packed cell volume, and plasma pigmentation. Coccidial lesion scores were significantly less for the combination of E. tenella and aflatoxicosis than for coccidiosis alone. This atypical response of the ceca to E. tenella in the presence of dietary aflatoxin was characterized by less distended ceca, very little coagulated blood in the ceca, and apparently more profuse cecal hemorrhage.     

Sensitivity of field isolates of Eimeria to monensin in the turkey

A method previously described by Jeffers and Bentley, involving calculation of a growth and survival ratio and optimal anticoccidial activity index, was used to investigate the sensitivity of 23 field isolates of Eimeria obtained from turkey flocks to the ionophorous antibiotic monensin. Isolates were obtained from litter and intestinal samples from several major turkey-growing regions of the United States, and in most cases contained at least two species of Eimeria. A mixture of strains that had been maintained in the laboratory for many years in the absence of exposure to anticoccidial drugs was found to be sensitive to monensin. Six of the field isolates were judged sensitive, seven partially resistant, and ten resistant to the drug, judged by the Jeffers and Bentley criteria. This is the first report of the acquisition of resistance to monensin in isolates of Eimeria from turkey flocks in the United States.     

Effects of the dose of Ehrlichia phagocytophila on the severity of experimental infections in lambs

Twenty-one lambs were used to investigate whether their response to an infection with Ehrlichia phagocytophila was dose-dependent Four groups of four lambs were infected intravenously with a dilution in physiological saline of E phagocytophila-infected sheep blood containing either 1.3 x 10(5) infected cells, or approximately 43 infected cells, 4.3 infected cells, or 1.3 infected cells (mean values) and four lambs were left uninfected. The incubation period was significantly shorter in the lambs infected with the highest dose of E phagocytophila. However, the clinical and haematological changes observed, and the weekly weight gains of the lambs were independent of the dose of E phagocytophila. As little as one Ephagocytophila infected cell may be enough to transmit the infection.     

Eimeria tenella: sensitivity of recent field isolants to monensin

Coccidia were propagated from litter samples obtained from broiler production flocks being medicated with monensin. Eimeria tenella was isolated from 48.9% of the litter samples from which coccidia were propagated. Tests of the monensin sensitivity of the 73 E. tenella isolants obtained revealed no monensin-resistant isolants.     

The immunoprophylaxis of of rotavirus infections in lambs.

The effect of colostrum or serum feeding on subsequent rotavirus infections was investigated in neonatal gnotobiotic lambs. Immunity after feeding colostrum did not depend on absorption of passively acquired antibody into the circulation. Protection against clinical disease depended on the volume of colostrum ingested. The protection afforded by feeding serum was specific, since serum free of rotavirus antibody failed to confer protection. Immune serum fed at a rate of 2.5 ml per kg twice daily protected against rotavirus infection. Also, it was shown by intraperitoneal inoculation of immune serum that protection could occur in the absence of ingested antibody, presumably by transfer of antibody into the gut. The implications of these findings for immunoprophylaxis of rotavirus diarrhoea in lambs and calves are discussed.     

Effect of sericea lespedeza (Lespedeza cuneata) fed as hay, on natural and experimental Haemonchus contortus infections in lambs

Parasitic infection is one of the leading economic constraints in small ruminant production. This problem is exacerbated as the resistance of nematode populations to chemical treatment (anthelmintics) becomes increasingly more common. Condensed tannin (CT) containing plants are being investigated as alternative solutions to address these problems. This investigation was conducted to evaluate the effect of the CT containing forage, Lespedeza cuneata (sericea lespedeza, SL) fed as hay, on Haemonchus contortus infection in sheep. Naturally and experimentally infected lambs were fed either SL or bermudagrass (BG, control) hay for 49 days. All lambs were fed BG hay for an additional 14 days. SL hay effectively reduced (67-98%) fecal egg count (FEC) during the time of feeding for both infection groups. FEC increased in both infection groups after SL feeding was stopped which indicated an effect on fecundity. SL hay feeding also reduced worm numbers, with more of an effect on reducing naturally infected worm burdens (67.2%) than on establishment of incoming larvae (26.1%). SL fed as hay may be more useful to remove existing worms than establishing worms. The decrease in FEC would have the benefit of reduced pasture contamination.     

Effects of monensin on the bioavailability and elimination of selenium from blood in lambs

A bioavailability study was conducted in lambs following intravenous and oral administration of sodium selenite (0.4 mg selenium/kg body weight) with and without concurrent oral monensin. Two- or three-compartment open models with first-order absorption after oral administration adequately described plasma selenium disposition irrespective of whether monensin was being administered. No significant differences were observed between groups of lambs receiving intravenous selenium with or without monensin with respect to distribution or elimination half-lives of selenium, areas under the concentration-time curve (AUC), volumes of distribution (Vd(ss)), or clearances (Cl). In lambs given selenium per os, no significant differences were observed with animals receiving monensin as well with respect to absorption and elimination half-lives, Vd(ss), or the time at which peak selenium concentrations occurred (tmax). However, peak selenium levels (Cmax) and AUC values were significantly higher in the group given monensin. The bioavailability of selenium with and without monensin was estimated to be 60% and 43%, respectively.     

Efficacy of toltrazuril and clazuril against experimental infections with Eimeria labbeana and E. columbarum in racing pigeons

The efficacy of toltrazuril in comparison with clazuril on heavy experimental Eimeria labbeana and E. columbarum infections in pigeons was investigated. The minimum required dose of toltrazuril to completely suppress oocyst excretion is 20 mg/kg body weight for 1 day. After treatment with toltrazuril, there was a dose-dependent period during which pigeons remained negative; at a dosage of 35 mg/kg or higher, this period was at least 4 weeks. Clazuril at the recommended dose of 2.5 mg/pigeon resulted in a rapid suppression of oocyst excretion, but oocysts were again observed in the feces 20 days after treatment. The fact that oocysts appeared again in the feces 3 to 5 weeks after treatment can probably be explained only by a persistence of endogenous stages, which are not affected during treatment, rather than by a reinfection. Reinfection of the previously medicated and infected pigeons 30 days after the first infection provided some data on possible induced immunity.