Differences In Lesion Scores Research Articles

Differential Impact of Massachusetts, Canadian 4/91, and California (Cal) 1737 Genotypes of Infectious Bronchitis Virus Infection on Lymphoid Organs of Chickens.

Infectious bronchitis virus (IBV) induces severe economic losses in chicken farms due to the emergence of new variants leading to vaccine breaks. The studied IBV strains belong to Massachusetts (Mass), Canadian 4/91, and California (Cal) 1737 genotypes that are prevalent globally. This study was designed to compare the impact of these three IBV genotypes on primary and secondary lymphoid organs. For this purpose, one-week-old specific pathogen-free chickens were inoculated with Mass, Canadian 4/91, or Cal 1737 IBV variants, keeping a mock-infected control. We examined the IBV replication in primary and secondary lymphoid organs. The molecular, histopathological, and immunohistochemical examinations revealed significant differences in lesion scores and viral distribution in these immune organs. In addition, we observed B-cell depletion in the bursa of Fabricius and the spleen with a significant elevation of T cells in these organs. Further studies are required to determine the functional consequences of IBV replication in lymphoid organs.

Effects of Enrichment Type, Presentation and Social Status on Enrichment Use and Behavior of Sows-Part 2: Free Access Stall Feeding.

Simple SummaryThe Canadian pork industry is transitioning to group housing gestation. The Code of Practice for pigs recommends the provision of enrichment. Although straw is considered prime enrichment, it is perceived as a biosecurity risk and manure management issue; therefore, identifying other enrichment materials is needed to promote adequate welfare. Previously, our group examined the effects of four types of point-source enrichments in an Electronic Sow Feeding (ESF) system. This study is a continuation of our previous research applied in Free Access Stalls (FAS). Four treatments were studied: (1) Constant: constant provision of wood on chain; (2) Rotate: rotation of three enrichments (rope, straw, and wood on chain); (3) Stimulus: rotation of three enrichments with an associative stimulus (bell or whistle); and (4) Control: no enrichment. Contact with enrichment and time spent in different postures were measured using scan sampling. Skin lesions were scored, and salivary cortisol was measured in a subset of dominant and subordinate sows. Sows spent more time contacting straw compared to other types of enrichment. There was no difference in enrichment use between dominant and subordinate sows, no increase in cortisol concentrations in subordinates nor significant differences in aggression. In conclusion, sows preferred straw enrichment and FAS provided some protection against aggression and stress.Continuing with previous research by our group in an ESF system, four types of enrichment treatments were assessed in gestating sows housed in Free Access Stalls: (1) Constant: constant provision of wood on chain; (2) Rotate: rotation of rope, straw and wood; (3) Stimulus: rotation of enrichments with an acoustic cue; and (4) Control: no enrichment. Treatments had a 12 day-duration. Four groups (28 ± 2 sows) were studied from weeks 6 to 14 of gestation. Groups received all treatments in random order. Three dominant and 3 subordinates per pen were selected using a feed competition test. Digital photos were collected at 10 min intervals for 8 h on days 1, 8, 10 and 12 to record interactions with enrichment. Skin lesions were assessed on days 1 and 12, and salivary cortisol was assessed in weeks 6, 10 and 14 of gestation. More enrichment use was observed in Rotate and Stimulus treatments compared to Constant, and more sows contacted enrichment when straw was provided in the Rotate and Stimulus treatments. There was no difference in the amount of enrichment use by dominants and subordinates, no cortisol concentration elevation in subordinate sows nor any difference in lesion scores. In conclusion, social status had little impact and feeding system is important to reduce stress and aggression.

Pathogenesis of domestic pigs submitted to mycobacterial sensitizations previous to experimental infection with Mycobacterium bovis

Aim of study: To demonstrate the virulence of a Mycobacterium bovis local pig isolate in order to contribute to a better understanding of the pathological and immunological consequences of M. bovis infection in previous sensitized animals. Area of study: Buenos Aires, Argentina Material and methods: One group of ten pigs received two oral doses of killed M. bovis suspension and a comparative intradermal tuberculin test (CIT) (multiple sensitized) and then was infected with the M. bovis strain. Another group only received the CIT (single sensitized) and the infective dose. Humoral immune response was followed monthly, and gross pathology, histopathological and bacteriological analysis were performed at necropsy 100 days after infection. Main results: M. bovis oral infection induced lesions and allowed bacterial growth in most of the animals. Previous sensitization with killed M. bovis suspension slightly raised the intensity of the response, as the multiple sensitized group showed higher lesion scores and humoral response. Research highlights: Although the differences in lesion scores were not statistically significant, oral route infection after sensitization can modify the course of infections towards a fast development of lesions with a higher fibrotic component suggestive of increased resistance to infection in the right conditions.

Concurrent use of saponins and live coccidiosis vaccines: the influence of a quillaja and yucca combination on anticoccidial effects and performance results of coccidia-vaccinated broilers

A series of studies was conducted to determine the effects of a quillaja and yucca (saponin) combination (QY) product on postvaccination oocyst production, development of coccidial immunity, and final bird performance of broilers administered live coccidiosis vaccines. In all, 3 groups of tests were carried out. Study 1 evaluated the effects of QY (0 and 250 ppm) on oocyst per gram of feces (OPG) following vaccination at day-of-age; OPG were measured from 5 to 12 d postvaccination. Study 2 determined the effects of QY (250 ppm) in the presence of 3 commercial coccidiosis vaccines in floor pens. OPG were measured weekly for birds receiving each vaccine and for each corresponding vaccine group fed QY. To determine whether QY influenced the development of coccidial immunity induced by the 3 vaccines, 5 birds were removed from each pen at 28 d and challenged with pathogenic levels of Eimeria spp. At 6 d post challenge, lesion scores were used to evaluate the effects of QY on immune protection provided by each vaccine. In addition, comparisons of final bird performance were made between birds given each vaccine and their corresponding vaccinates fed QY. Study 3 comprised a meta-analysis of 15 floor pen trials in which 21- and 42-d body weight, feed conversions, and total mortality were compared between coccidiosis-vaccinated broilers and similarly vaccinated broilers fed QY (250 ppm). Results of these experiments indicated that feeding QY to vaccinated broilers did not significantly affect OPG from days 5 through 12 postvaccination (P > 0.05). For each vaccine tested in study 2, OPG values were the highest at 14 and 21 d postvaccination. QY significantly reduced OPG at 14 d postvaccination for 2 of the vaccines tested, and produced a similar effect in 1 vaccine at 21 d postvaccination. The remaining vaccine was not affected by QY in the postvaccination OPG results. Despite these changes in OPG, significant differences in lesion scores following the Eimeria challenge were not observed for any vaccinated groups receiving QY. Irrespective of the vaccine, both interim and final feed conversion values were significantly improved when QY was fed (P < 0.01). Similarly, results of a 15-trial meta-analysis indicated that QY-fed vaccinated broilers had higher body weights, improved feed conversions, and lower mortality than their vaccinated controls. Results show that while QY may induce changes in OPG following vaccination, coccidia-vaccinated broilers fed QY develop immunity equivalent to that of controls and show significant improvements in performance and mortality.

A High Enrichment Replenishment Rate Reduces Damaging Behaviors and Increases Growth Rate in Undocked Pigs Kept in Fully Slatted Pens.

One of the difficulties in complying with the prohibition of routine tail docking is a lack of effective alternative solutions to prevent tail biting, especially in fully slatted systems. This study compared three slat-compatible enrichment replenishment strategies for pigs. Forty-eight mixed-sex pens (six males and six females/pen) of undocked pigs were followed from birth to slaughter. Pre-weaning, half the pigs were provided with enrichment materials (a cardboard cup, rubber toy, hessian cloth and bamboo), in addition to a rope for the sows, in all farrowing crates. Post-weaning, all pens were enriched with eight identical items, including an elevated rack supplied with fresh-cut grass, and objects of wooden, bamboo, rubber, and fabric materials presented in various ways. However, three different replenishment frequencies were applied: “Low” (replenished on Monday/Wednesday/Friday), “Medium” (replenished once daily), and “High” (replenished ad libitum). Individual pigs were weighed on days 0, 49, 91, and 113 post-weaning. Direct behavior observations were conducted twice weekly at pen level (10 min/day/pen), and tail and ear lesion scores of individual pigs were also recorded every other week. These measurements were taken during the post-weaning period. The cost of all enrichment materials used was calculated. Pre-weaning enrichment only contributed to a lower ear lesion score (P = 0.04). No difference in lesion scores was found between post-weaning treatments. “Low” replenishment rate pigs performed more damaging behaviors (tail/ear biting, belly-nosing, mounting, other biting, and aggressive behaviors combined) than “High” and “Medium” pigs (P < 0.01). The average daily gain in the finishing stage was higher in “High” than “Low” pigs (P < 0.05). Although sporadic tail biting occurred, only 0.69% of the pigs had their tails bitten severely enough that they became shorter than half of a normal undocked tail. The average enrichment cost for the post-weaning period was <€2 per pig. In conclusion, the high enrichment replenishment rate increased growth and reduced damaging behaviors compared to the low replenishment rate pigs. Overall, these findings show that the provision and regular replenishment of multiple, slat-compatible, enrichment sources can reduce tail damage to manageable levels without the need for tail docking.

Evaluation of encapsulated sodium butyrate with varying releasing times on growth performance and necrotic enteritis mitigation in broilers

This study was conducted to evaluate the effect of an encapsulated sodium butyrate (Na-B) with targeted releasing times on growth performance and mitigating the impact of necrotic enteritis in broilers. Two Na-B (30% of Na-B content) products, CMA (2 h releasing time) and CMP (3 to 4 h releasing time), were evaluated in a necrotic enteritis challenge model. The experiment consisted of 4 Na-B treatments (500 and 1,000 ppm of each product) plus 2 control (non-challenged and challenged). A total of 336 Cobb-Cobb male broilers were placed 8 birds per pen into 7 replicate battery cages. On day 14, birds from challenged treatments were orally gavaged with ∼5,000 oocysts of Eimeria maxima. On day 19, 20, and 21, the challenged birds received 1 mL of 108 cfu/mL Clostridium perfringens. Total pen body weight (BW) and feed weight were assessed on day 14, 21, and 28 for BW gain and mortality-adjusted feed conversion ratio (FCR). On day 21, 3 birds were randomly selected per pen and scored for intestinal lesions. The duodenum and jejunum tissue were collected on day 21 and 28 for quantifying intestinal histology. Results revealed that adding CMA at 500 ppm showed significantly higher cumulative BW gain (P < 0.05) compared to the challenged control from day 1 to 21. Adding CMA at 500 ppm also showed the equivalent cumulative FCR that was comparable to the non-challenged control on day 21. The CMA treatments and CMP at 1,000 ppm treatment showed equivalent BW gain compared to the non-challenge control after an additional 7 d post-challenge on day 28. Both products at 500 or 1,000 ppm had the significantly (P < 0.05) lower intestinal lesion scores compared to the challenged control. However, there was no difference in lesion scores among the Na-B treatments. The Na-B product targeted to release in the anterior intestinal tract shows the beneficial effects on BW gain and feed utilization efficiency in current challenge model. Adding encapsulated Na-B product has the potential to mitigate the impact of necrotic enteritis in broilers.

The impact of β-glucans on performance and response of broiler chickens during a coccidiosis challenge.

Coccidiosis is a costly parasitic disease to the poultry industry with multiple prevention methods being explored to control its impact. This study evaluated the feeding effects of β-glucans on performance and responses of chickens during a coccidiosis challenge. Cobb 500 male broilers (n = 1280) were assigned to 1 of 8 treatment groups (8 replicate pens; 20 birds/pen) in a 2 × 4 factorial arrangement, including non-infected and Eimeria-infected birds fed for 28 d a control diet, control + BG (150g/MT Algamune 50), control + BGZn (100g/MT Algamune 50Zn), and control + 0.01% Salinomycin (Sal). On d15, birds in the challenge groups received a mixed Eimeria inoculum. Birds and feed were weighed weekly on a per pen basis to evaluate body weight gain (BWG), feed intake (FI), and feed conversion ratios (FCR). Lesion scores were assessed 6 d post infection (d21) on 3 birds per pen. Performance data were subjected to ANOVA and differences were established using the LS-MEANS statement with significance reported at P ≤ 0.05. There were minor differences in lesion scores among the dietary treatments in the infected groups with reduced duodenal and cecal scores in the Sal group compared to the BGZn and BG groups, respectively. The coccidiosis challenge main effect resulted in a significant reduction in 0-28 d BW and FI. Dietary treatment resulted in non-significant effect on BWG, but Sal addition resulted in increased FI. A significant diet X challenge interaction resulted in higher FCR in the Eimeria-challenged birds supplemented with Sal and BGZn in comparison to the other challenged groups, likely due to reduced mortality in the challenged Sal and BGZn groups. Body composition analysis at d28 revealed that the Eimeria challenge reduced both fat and lean tissue contents, where the β-glucans and Sal birds had lower fat percent than control birds.

Minimal short-term effect of dietary 2'-fucosyllactose on bacterial colonisation, intestinal function and necrotising enterocolitis in preterm pigs

Human milk decreases the risk of necrotising enterocolitis (NEC), a severe gastrointestinal disease that occurs in 5-10 % of preterm infants. The prebiotic and immune-modulatory effects of milk oligosaccharides may contribute to this protection. Preterm pigs were used to test whether infant formula enriched with α1,2-fucosyllactose (2'-FL, the most abundant oligosaccharide in human milk) would benefit gut microbial colonisation and NEC resistance after preterm birth. Caesarean-delivered preterm pigs were fed formula (Controls, n 17) or formula with 5 g/l 2'-FL (2'-FL, n 16) for 5 d; eight 2'-FL pigs (50 %) and twelve Controls (71 %) developed NEC, with no difference in lesion scores (P=0·35); 2'-FL pigs tended to have less anaerobic bacteria in caecal contents (P=0·22), but no difference in gut microbiota between groups were observed by fluorescence in situ hybridisation and 454 pyrosequencing. Abundant α1,2-fucose was detected in the intestine with no difference between groups, and intestinal structure (villus height, permeability) and digestive function (hexose absorption, brush border enzyme activities) were not affected by 2'-FL. Formula enrichment with 2'-FL does not affect gut microbiology, digestive function or NEC sensitivity in pigs within the first few days after preterm birth. Milk 2'-FL may not be critical in the immediate postnatal period of preterm neonates when gut colonisation and intestinal immunity are still immature.

The effect of a straw dispenser on behavior and lesions in weanling pigs

Abstract Slatted floors and liquid manure–handling systems in intensive housing systems preclude the use of large straw quantities as enrichment material for pigs. Consequently, there is a need for alternative enrichment strategies, for example, by using suitable applications providing pigs with small straw quantities, which are associated with low straw waste. The aim of this study was to evaluate the effects of a straw dispenser filled with fully chopped straw on the behavior and lesions in weanling pigs. A total of 365 weanling pigs, housed in single-sex groups (gilts and intact boars), were randomly divided in 2 groups. Half of the pigs had access to a straw dispenser (straw; n = 187), and the other half had no access to straw (control; n = 178). They were housed in the weanling unit for a period of 7 weeks (7-20 kg) and received liquid feed. One straw dispenser was provided per pen, accessible to 3 pigs at a time of 10 to 15 pigs in the pen, and positioned above the feed trough. To receive straw, pigs had to manipulate the dispensing unit on the bottom of the dispenser. Behavioral observations were carried out twice a week, and present lesions were also scored on these days by the same observer. Data were analyzed using a logistic mixed model and a Fisher exact test. No differences were found for biting behavior toward different body parts between control and straw pigs. There was also no effect of gender. In boars, aggressive behavior occurred more in straw groups compared to control groups, which might be related to competition. This finding is also reflected in more lesions on the middle part of the body in straw groups. A lack of difference in lesion scores for tail and ears between the 2 groups suggests that the dispenser provided insufficient distraction for weanling pigs compared to a barren environment. However, the position of the straw dispenser must be kept in mind, as this caused pigs to perform straw-directed behavior mainly in the feed trough. In this study, based on behavioral observations and lesion scores, it seems that the straw dispenser did not provide pigs with more advantages compared to pigs in a barren environment. Moreover, competition was observed in pens with boars, which might be related to the fact that only one dispenser was provided per pen. It should, however, be taken into account that the position of the dispenser might not have been the most suitable as it possibly caused mixing of feed and straw.

An in vitro attenuated strain of Histomonas meleagridis provides cross-protective immunity in turkeys against heterologous virulent isolates

ABSTRACTIn the current study, cross-protective immunity induced by a well-defined clonal strain of Histomonas meleagridis, attenuated by prolonged in vitro cultivation against different clonal heterologous isolates of the same parasite was investigated. For this purpose, 86 turkey poults were assigned to groups consisting of 9–10 birds. Birds of four groups were vaccinated on their 1st day of life followed by re-vaccination on their 14th day of life when the remaining turkeys were left untreated. The challenge was performed using four strains of H. meleagridis that were isolated from chickens or turkeys from different outbreaks of histomonosis in Europe and three of them showed diversities in their genome. Hence, every strain used for the challenge was applied to a group of vaccinated and a group of non-vaccinated birds while birds of the negative control group were sham inoculated. Non-vaccinated birds suffered from severe histomonosis due to the challenge with fatalities reaching from 5 to 10 turkeys per group. Vaccinated birds did not contract clinical signs of the disease following challenge and the increase in weight was unaffected compared to birds of the negative control group. A significant difference in lesion scores was recorded between vaccinated and non-vaccinated groups, with very few instances of liver involvement in the former groups. Livers of vaccinated birds that were without recordable macroscopic lesions were also found negative by immunohistochemical investigation. According to the data obtained, the present study demonstrates, for the first time, the cross-protective capability of a tentative vaccine strain of H. meleagridis attenuated in vitro against heterologous virulent isolates of different origin.

The effect of selection for residual feed intake on general behavioral activity and the occurrence of lesions in Yorkshire gilts1

The objectives of this study were to determine the effect of selection for improved residual feed intake on behavior, activity, and lesion scores in gilts in their home pen. A total of 192 gilts were used, 96 from a line that had been selected for decreased residual feed intake over 5 generations (LRFI) and 96 from a randomly bred control line. Gilts were housed in 12 pens (16 gilts/pen; 0.82 m(2)/gilt) containing 8 gilts from each line in a conventional grow-finish unit. Twelve hours of video footage were collected on the day of placement and then every 4 wk for 3 more observational periods. Video was scored using a 10-min instantaneous scan sampling technique for 4 postures (standing, lying, sitting, and locomotion) and 1 behavior (at drinker). Categories of active (standing, locomotion, and at drinker) and inactive (sitting and lying) were also created. Lesion scores were collected 24 h after behavior collection had begun. The body of a gilt was divided into 4 regions, with each region receiving a score of 0 (0 lesions) to 3 (5+ lesions). All statistical analyses used Proc Mixed of SAS. Data were analyzed separately for the day of placement and the subsequent 3 rounds. General activity was summarized on a percentage basis by each posture and behavior and subjected to an arcsine square root transformation to normalize data and stabilize variance. Analysis was performed on each behavior and posture. Lesion scores for each region of the body were analyzed as repeated measures. There were no differences (P > 0.05) between genetic lines for all postures and the behavior at drinker on the day of placement. However, over subsequent rounds it was observed that LRFI gilts spent less (P = 0.03) time standing, more time sitting (P = 0.05), and were less active (P = 0.03) overall. Gilts from the LRFI line had decreased (P < 0.045) lesion scores on the day after placement. However, over subsequent rounds there were no (P > 0.05) differences between the genetic lines. In conclusion, on the day of placement there were no postural, behavior, or general activity differences between genetic lines, but LRFI gilts had decreased lesion scores. Behavioral differences were observed between genetic lines over subsequent rounds, with LRFI gilts becoming less active, but there were no differences in lesion scores.

Effect of Vaccination Against Coccidiosis in Combination with an Antibacterial Oregano (Origanum vulgare) Compound in Organic Broiler Production

Effects on production and health in broilers vaccinated against coccidiosis (Paracox®, Schering-Plough Animal Health) in combination with an antibacterial organic compound (Orego-Stim®, Meriden Animal Health Ltd.) were investigated. To obtain an environment and infection level similar to practical conditions, experimental floor pens were set up in a commercial broiler chicken house. Orego-Stim® supplement increased live weight and feed intake up to 48 days of age, whilst feed conversion ratio was not significantly affected. Vaccinated birds had a significantly higher live weight between 34 and 48 days, compared to non-vaccinated, but vaccination did not significantly affect feed intake or feed conversion ratio. Coccidial numbers in the litter were low, and only minor intestinal lesions were found. There were no significant differences in lesion scores between the different treatments. Orego-Stim® supplement decreased caecal numbers of Clostridium perfringens at 31 days, but not at 52 days, and numbers were not affected at all by anticoccidial vaccination. Bird health was overall good. The results indicate that vaccination against coccidiosis in combination with an in-feed antibacterial compound may be an alternative control method for intestinal health in organically produced chickens.

Immune competence, resistance to Escherichia coli and growth in male broiler parent chicks fed different levels of crude protein.

Immune competence, resistance to Escherichia coli and growth were measured in female chicks of broiler male parent lines from four different commercial sources. These chicks were fed with three levels of dietary crude protein (CP) from day-old. The protein contents in the diets were 18%, 20.5% and 23%; these diets are referred to as the low-, medium- and high-protein diets, respectively. There was a significant genotype by dietary protein interaction for body weight at 35 days of age but not at 14 or 28 days of age. At 14 days of age, the chicks fed on the high-protein diet weighed significantly more than those fed on the low-protein diet, but there were no differences between the chicks fed on the medium-and low-protein diets. The influence of CP content on body weight had disappeared by 28 days of age. There were significant differences between the genotypes-in antibody production in response to sheep red blood cell (SRBC) inoculation, but no such differences were observed between the chicks fed the different levels of dietary protein. Chicks fed on the high-protein diet had lower lesion scores following E. coli inoculation than those fed on the low-protein diet. There were also significant differences in lesion scores among the genotypes. Genotypes with heavier body weights had significantly higher lesion scores and lower antibody titres than those with less body weight. Also, genotypes of lower body weight had a greater cutaneous basophilic hypersensitivity response to phytohaemaglutinin-P inoculation, and a better humoral response against SRBC and a lower heterophil to lymphocyte ratio.

Protective role of maternal antibodies against Haemophilus parasuis infection

Abstract Objective To evaluate the impact of maternal antibodies after challenge exposure of baby pigs with a homologous serovar of Haemophilus parasuis. Animals 7 gilts and their litters from a high health status farm. Procedure Gilts were vaccinated twice with a commercial bacterin that contained H parasuis serovar 4 and 5 or, as a control, adjuvant only. A group of pigs was also vaccinated similarly before challenge exposure. After early and late challenge exposure at 3 and 4 weeks, respectively, all pigs from vaccinated gilts were evaluated for clinical signs of infection, lesions, and antibody titer. Results All pigs coming from control gilts had severe signs of H parasuis infection. Macroscopic lesions included polyserositis and pneumonia, and bacteriologic examination confirmed H parasuis as the etiologic agent. Vaccinated pigs born to vaccinated gilts did not have clinical signs of disease. However, some vaccinated pigs born to control gilts had signs of nervous system dysfunction and lameness. There was no difference in lesion scores between early or late challenge exposure, but lesions scores for pigs from vaccinated and control gilts were different (P &lt; 0.01). Conclusions Under these experimental conditions, immune-naive and vaccinated pigs from vaccinated gilts were protected against systemic lesions when challenge exposed with a virulent strain of H parasuis. Clinical Relevance Vaccination of the gilt and pigs protects the latter from polyserositis, but results are not different from those for nonvaccinated pigs from vaccinated gilts. Maternal antibodies did not seem to interfere with vaccination of pigs at 1 and 3 weeks of age. (Am J Vet Res 1999;60:81–87)

Response of Unimmunized and Sporozoite-Immunized Chickens to Challenge with Avian Eimeria Species: Effects of Intraperitoneal Injection of Sephadex

Unimmunized chickens, given intraperitoneal injections of Sephadex at the same time that they were inoculated with oocysts of either Eimeria tenella or E. acervulina, had significantly lower lesion scores at 6 days postinoculation (PI) than unimmunized chickens that were injected with saline instead of Sephadex. Despite the difference in lesion scores, there was little effect on weight gain, except in one experiment, in which Sephadex-injected chickens gained significantly more weight than saline-injected chickens. In contrast, in chickens that were immunized by prolonged exposure to sporozoites of E. adenoeides, injection of Sephadex at the time of challenge with E. tenella did not reduce lesion scores or parasite development as compared with the uninjected chickens, and the weight gain of the Sephadex-injected challenged chickens fell to a level significantly lower than that of their saline-injected challenged counterparts. The data indicate that Sephadex injected at the time of oocyst inoculation 1) produces markedly different effects on lesion scores and weight gain in unimmunized and immunized chickens and 2) abrogates sporozoite-elicited immunity against E. tenella challenge.

Characterization of Resistance and Immunity to Eimeria tenella Among Major Histocompatibility Complex B-F/B-G Recombinant Hosts

The relative influence of the B-F vs. B-G chromosomal regions on innate resistance and immunity to Eimeria tenella was studied among six B-F/B-G recombinants, designated BR1, BR3, BR4, BR5, BR6, and BR8. In one experiment, resistance was studied among 340 F1 chicks each carrying the B17 allele derived from Line UCD.003 and therefore also heterozygous for one of the B recombinant haplotypes. In a second experiment, acquired immunity was studied among 161F2 chicks each carrying one B17 allele and segregating for one of the recombinant alleles.In Experiment 1, F1 Chicks of similar haplotypes, BR3 and BR4 (BR3-G23) BR3, gained significantly more weight than those with BR1 (BF24-G23) and BR5 (BF21-G19) following exposure to a single high dose of 25,000 oocysts, although no differences in lesion scores were detected among the six recombinants. Following exposure to a single low dose of 2,500 oocysts, F1 chicks BR3 and BR4 also gained significantly more weight and had significantly lower lesion scores than BR1 or BR5 F1 chicks.To study acquired immunity in the F2 homozygous chicks, five consecutive daily exposures of 500 oocysts were followed 21 days later by challenge with 10,000 oocysts. The BR5 (BF21-G19) and BR6 (BF21-G23) homozygous chicks, both carrying the B-F21 allele, showed significant protection in terms of reduced lesion scores. These results demonstrate that E. tenella parasitism manifests itself to varying degrees in chicken hosts possessing different recombinant major histocompatibility complex haplotypes.

Coccidiosis: Effects of High Environmental Temperatures on Anticoccidial Protection

In a series of nine experiments birds subjected to heat-stress showed decreases of 9 to 61 percent in feed intake. In only one of these experiments, involving E. acervulina and monensin, was there sufficient reduction of anticoccidial intake to partially nullify effects of drug protection. In this case, a 40 percent decrease in monensin intake resulted in significantly higher lesion scores (1.9 vs. 1.0) (P ≤ 0.05) in birds maintained at 32° C. for days 1 to 7 postinfection (P.I.) compared to controls maintained at 20° C. No other failures due to heat stress occurred with this anticoccidial in three other trials with E. acervulina or five trials involving E. tenella infection. In one experiment E. tenella coccidiosis (lesion scores 0.7 vs. 1.1) was more severe in the cool environment than in birds under heat-stress from 2 to 7 days P.I. Similarly, less severe lesions of E. tenella (0.4 vs. 0.8) occurred during heat-stress (32° C.) than in controls maintained at 11° C. in zoalene-fed and unmedicated control birds. No differences in lesion scores occurred in birds in hot versus cool room environments in two experiments involving sulfaquinoxaline or one with robenidene and E. tenella infection. E. tenella lesions in unmedicated controls were significantly more severe in the cool than the hot environment in one experiment. Results from these experiments suggest that decreases in feed and anticoccidial intake during heat-stress could seldom be the cause of coccidiosis breaks under field conditions.

A larvicidal evaluation programme using Ascaris suum in mice.

An evaluation programme is presented for determining activity of unknown compounds on Ascaris suum larvae migrating into pulmonary tissues of animals. Data on gross lung lesions due to migrating ascarid larvae were obtained in a series of 44 screening tests consisting of 223 group observations from 1115 mice orally infected with A. suum. Lesion scores were graded in ascending order from 0 to 5 depending upon number and extent of pulmonary haemorrhages. In general, there was no significant difference in lesion scores between untreated mice and mice treated with unknown compounds in their ration. The programme is based on an initial 95% rejection of compounds with a 5% ability to retest compounds in groups of mice.The grand mean score for 44 tests was 2·88. Ninety per cent confidence limits for means among tests established scores at 2·21 and 3·55, and among groups of mice at 1·76 and 4·00, When the test mean was less than 2·2, the ascarid ova used for infection were considered non-virulent. Compounds selected as active were in groups of mice having a mean lesion score of 1·76 or less. Banminth, Styquin and Tetramisole showed larvicidal activity. A reasonable compromise exists in this system wherein false leads are tolerated to avoid screening out effective materials. The host-parasite relationship is proposed as a valuable tool for anthelmintic evaluation.The authors wish to thank Mr W. Henry and Mr M. Jackley of this laboratory.