Greg F. Mathis

Survival of Coccidia in Poultry Litter and Reservoirs of Infection

The survival of coccidia was studied in poultry litter, dust, soil, and invertebrate animals. The populations of coccidia in litter were recorded during broiler growout in 16 broiler houses and in floor-pen trials involving anticoccidial drugs. The viability of oocysts declined rapidly in poultry litter regardless of the species; it was retained best in 40% moisture at 4 C. Sporocysts from broken oocytes did not survive even short exposure to poultry litter. Survival of oocysts was poorest at temperatures higher than 4 C, regardless of the carrier. In four floor-pen experiments designed to study the efficacy of anticoccidial drugs, the oocyst counts correlated in a general way with lesion scores and performance, indicating the oocyst counts might be useful along with other parameters to judge the effectiveness of drugs. Coccidia were transmitted to susceptible chicks by feeding them darkling beetles, flies, or house dust from poultry houses. More carrier samples were positive during the warmer months. Oocyst counts in litter of commercial poultry houses were very low during the first or last weeks of broiler growout but were high during the normal 3-to-6-week stress period. These results confirm the poor survival of oocysts in poultry litter and suggest that carryover from one flock to the next depends on the survival of a few oocysts in dust or arthropod vectors.

Anticoccidial efficacy of diclazuril against recent field isolates of Eimeria from commercial poultry farms.

The anticoccidial efficacy of diclazuril, a novel anticoccidial agent, was titrated in laboratory experiments using recent field isolates of Eimeria. Fifty tests were conducted with six individual species isolates, and seven tests were done with a mixture of the six species. Results were based on intestinal lesion scores at necropsy, droppings scores, and weight gain. Diclazuril at 0.5 ppm was almost completely effective against E. tenella, E. acervulina, and E. mitis. Prevention of E. brunetti was better at 1.0 ppm than at 0.5 ppm. In birds infected with E. mitis. Prevention of E. brunetti was better at 1.0 ppm than at 0.5 ppm. In birds infected with E. maxima, diclazuril at 0.5-1.5 ppm significantly reduced lesion scores and droppings scores and improved weight gain, although lesions were higher than with other species. Oocyst shedding by E. maxima was almost completely prevented by 0.5-1.5 ppm. Lesion scores and droppings scores caused by E. necatrix or mixed infections were greatly reduced by 0.5 ppm of diclazuril, but 1.0 ppm was necessary to obtain full protection of weight gain. Results suggest that 1.0 ppm of diclazuril best prevents coccidiosis caused by six species of coccidia in chickens.

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.

Comparative evaluation of probiotic and salinomycin effects on performance and coccidiosis control in broiler chickens

The annual financial loss to the poultry industry as a result of coccidiosis has been estimated at about US

Anticoccidial efficacy of diclazuril in broilers under simulated natural conditions in floor pens.

3 billion. The objective of this study was to evaluate and compare the effects of probiotics and salinomycin as feed additives on performance and coccidiosis control in male broilers raised to 42 d of age. The study consisted of 360 Cobb male broiler chickens randomly allocated to 4 groups each with 3 replicates. Group 1: untreated, unchallenged negative control group (NC); group 2: untreated, challenged positive control group (PC); group 3: negative control supplemented with salinomycin 66 mg/kg, challenged group (Sal); and group 4: negative control supplemented with probiotics, challenged (Prob mix). On d 15, all birds (except group 1) were challenged with approximately 75,000, 25,000, and 75,000 of Eimeria acervulina, Eimeria maxima, and Eimeria tenella oocytes, respectively, that were mixed into the feed. Feed conversion ratio and mortality were recorded throughout the experiment. On d 21 and 42, intestinal lesions and litter conditions were scored. On d 7, 14, 21, 28, 35, and 42, oocyst counts were determined from 10 freshly collected fecal samples per pen. The results showed that mortality, litter, and lesion scores at d 21 and 42, and oocyst shedding at d 21 did not differ significantly between the Prob mix and the Sal groups. However on d 28, oocyst shedding was significantly lower in the Sal group than in the PC group but insignificantly lower than the Prob mix group. Body weights of the Prob mix group at d 42 were significantly lower than the Sal group; however, the feed conversion ratio values were similar between the 2 groups. The results of this study showed that probiotics supplementation could be considered as a potential strategy to control coccidiosis in broiler chickens.

Comparative Efficacy of Enrofloxacin, Oxytetracycline, and Sulfadimethoxine for the Control of Morbidity and Mortality Caused by Escherichia coli in Broiler Chickens

Anticoccidial efficacy of diclazuril given for 42 to 49 days of age was evaluated in broiler chickens. Mortality from coccidiosis in unmedicated controls averaged 12.90% for six experiments. Treatment with diclazuril at 0.5, 1.0, and 1.5 ppm reduced coccidiosis mortality to 1.41%, 0.85%, or 0.63%, respectively, and reduced average total lesion scores by 78%, 81% or 82%, respectively. The final live weight and feed conversion at 49 days of age was significantly improved by treatment with diclazuril at all levels. Comparisons in some trials suggested that 1.0 ppm of diclazuril was equal or superior to the other anticoccidial drugs. There was no evidence that diclazuril harmed performance, even when given at 1.5 ppm.

Anticoccidial efficacy of diclazuril against recent field isolates of Eimeria from turkey farms in the United States.

Abstract The purpose of the present study was to compare the ability of enrofloxacin, oxytetracycline, and sulfadimethoxine to reduce morbidity and mortality caused by Escherichia coli (colibacillosis) in broiler chickens. The chickens were raised in 80 pens (20 birds per pen) with 20 pens representing each treatment group under simulated commercial conditions that produced a colibacillosis challenge scenario. Each group of 20 randomized pens (replicates) was given one of four water treatments. Chickens that received enrofloxacin had significantly less mortality (P < 0.01), lower average gross pathology (colibacillosis) scores (P < 0.01), and better feed-conversion ratios (P < 0.05) than did chickens that received either oxytetracycline or no medication. Chickens that received enrofloxacin had significantly less mortality and lower pathology scores than those that received sulfadimethoxine and numerically lower feed conversion than the sulfadimethoxine group. Results from the present study show that enrofloxacin is superior to oxytetracycline and sulfadimethoxine for the control of morbidity and mortality caused by E. coli in broiler chickens. Our findings will help veterinarians choose and prescribe the most efficacious antimicrobial when treating colibacillosis.

Evaluation of Interspecific Hybrids of the Chicken, Guinea Fowl, and Japanese Quail for Innate Resistance to Coccidia

In a series of laboratory tests, diclazuril was evaluated for efficacy against Eimeria adenoeides, E. meleagrimitis, E. gallopavonis, and a mixture of the three species. Four isolates of each of the species were tested. When given at 0.5, 1.0, and 1.5 ppm in the feed, diclazuril was highly efficacious against all three species and against mixtures of the three, as judged by protection against mortality from coccidiosis, reduction in droppings scores, and improvement of weight gains compared with unmedicated controls. When diclazuril was given at 1.0 ppm, the improvement in droppings scores and weight gains was better than when 0.5 ppm of diclazuril was given. Increasing the dosage to 1.5 ppm did not appear to offer any consistent or significant improvement over 1.0 ppm.

Elevated methemoglobin in the pathology of avian Coccidia (Protozoa, Apicomplexa) and Histomonas (Protozoa, Sarcomastigophora).

Experimental chicken/guinea fowl hybrids, guinea fowl, and chickens were orally inoculated with Eimeria acervulina or E. tenella, which are specific for chickens, or with E. grenieri, which is specific for guinea fowl. No intact oocysts were found in feces within 24 hr of inoculation, suggesting that excystation occurred in the normal and abnormal hosts. No oocysts were found in the feces of hybrids during a 9-day postinoculation period. The guinea fowl passed oocysts of guinea fowl coccidia (E. grenieri) but not those of chicken coccidia, and the chickens passed oocysts of chicken coccidia (E. acervulina and E. tenella) but not those of guinea fowl coccidia. Some asexual development (schizogony) occurred in hybrids inoculated with E. tenella, but sexual development (gametogony) did not. In contrast, quail/chicken hybrids became infected with oocysts of chicken coccidia (E. acervulina, E. tenella, and E. maxima) and quail coccidia (E. bateri) and passed a few oocysts during the normal patent period; control chickens and quails became heavily infected with oocysts of chicken and quail coccidia, respectively.

Calcium Montmorillonite-Based Dietary Supplement Attenuates Necrotic Enteritis Induced by Eimeria maxima and Clostridium perfringens in Broilers

Inflammation of tissues causes an increase in peroxide formation, which may directly cause the irreversible oxidation of hemoglobin to methemoglobin (Paul and Sbarra, 1968, Biochem. Biophys. Acta 156: 168-178; Cohen and Hochstein, 1961, Science 134: 1756). Such oxidation lowers the oxygen-carrying capacity of blood and may contribute to the pathogenicity of many types of infections. After a preliminary experiment indicated that methemoglobin is indeed elevated in chicken coccidiosis infections, we conducted a series of experiments to characterize the methemoglobinemia during coccidiosis infections and to compare this disease with histomoniasis in the turkey. Four species of coccidia were used, since there is considerable variation among species in virulence, type of lesions caused and location in the intestinal tract. Groups of 20 chicks (2-wk-old, parasite-free, Arbor Acres cockerels) were inoculated with sporulated oocysts of Eimeria tenella, E. maxima, E. brunetti, or E. necatrix which had been isolated from commercial poultry farms. The dose of oocysts was selected from prior titration in susceptible chicks. To provide birds for daily collection of blood samples, 100 chicks were inoculated with E. tenella and 10 were selected at random each day. Heparinized blood samples were taken at the peak of the infection (on days 4-7 postinoculation) (Experiment 1), or throughout the infection (Experiment 2). Other samples collected in heparinized capillary tubes were centrifuged for determination of packed cell volume (PCV). Intestinal lesions were graded at necropsy according to Johnson and Reid (1970, Expl Parasit. 28: 3036). Groups of 20 turkey poults (male, Nicholas) were infected with blackhead disease at 4 wk of age by cloacal inoculation of Histomonas meleagridis cultured in vitro (McDougald and Gal-