Acquisition of resistance after continuous infection with Ascaridia galli in chickens.

SUMMARY Acquired resistance against Ascaridia galli infection was studied in seventy-two 18-week-old white Leghorn chickens allocated to six groups (G1-G6). In order to understand the population dynamics following trickle-infection (100 eggs per chicken twice weekly), chickens of subgroups of G1 were necropsied 3 days after 1, 6 or 12 inoculations (G1A, G1B and G1C respectively), while G2-G4 were inoculated for 6 weeks. G2 was necropsied 4 weeks after the last inoculation. The number of established larvae increased initially (between G1A and G1B) but decreased after repeated inoculations (G1C, G2). G3, G4 and G5 were used to measure the efficacy of anthelminthic treatment and to monitor the acquisition of resistance following a challenge infection. At week 7 G3, G4 and G5 were treated with flubendazole for 7 days in the feed. Two weeks after treatment the chickens in G4 and G5 were challenged with 500 eggs. G6 was left as uninfected control. Necropsy at week 10 after first inoculation revealed a lower establishment rate, an impaired development and a more posterior localization of the larvae in G4 (trickle-infected-treated-challenged) compared with G5 (treated-challenged). IgY level in serum reached noticeable level at 14 dpi in G2 and G4 chickens, and in G4 chickens IgY level further increased after challenge infection. The study provides evidence that acquired resistance against A. galli in chickens leads to a significant yet incomplete protection against re-infection.

Antihistomonal effects of artemisinin and Artemisia annua extracts in vitro could not be confirmed by in vivo experiments in turkeys and chickens.

Five different Artemisia annua-derived materials (i.e. dry leaves, pure artemisinin, and hexane, dichloromethane or methanol extracts of leaves) were screened for their in vitro activities against six clonal cultures of Histomonas meleagridis. Except for the methanol extract, all tested materials displayed in vitro activity against all tested protozoal clones. Neither the dry plant material, extracts nor artemisinin showed any antibacterial activity against the xenic bacteria accompanying the six H. meleagridis clones at concentration levels identical to the antihistomonal setting. The dichloromethane extract of dry leaves (Ext-DCM) (minimal lethal concentration=1.0 mg/ml) and artemisinin (half-maximal inhibitory concentration=1.295 mg/ml) had the most promising antihistomonal properties and were therefore subsequently tested in a standardized experimental infection model in both turkeys and chickens infected with clonal H. meleagridis. There were no differences between treatment groups, where all infected turkeys showed severe clinical histomonosis and demonstrated severe typhlohepatitis typical for histomonosis. Consistent with the infection model used, the infected chickens did not show any adverse clinical signs but contracted severe lesions in their caeca 7 and 10 days post infection (d.p.i.), liver lesions were absent to mild after 7 d.p.i. and progressed to severe lesions at 10 d.p.i.; thus no differences between treatment groups were observed. In conclusion, neither artemisinin nor Ext-DCM was able to prevent experimental histomonosis in turkeys and chickens at the given concentrations, which is contrary to the antihistomonal effect noticed in vitro even though the same clonal culture was used. The results of this study therefore clearly demonstrate the importance of defined in vivo experimentation in order to assess and verify in vitro results.

Mannan-binding lectin (MBL) in two chicken breeds and the correlation with experimental Pasteurella multocida infection.

The present study is the first demonstration of an association of the genetic serum Mannan-binding lectin (MBL) concentration with bacterial infections in chickens. The genetic serum MBL concentration was determined in two chicken breeds, and the association with the specific Pasteurella multocida humoral immune response during an experimental infection was examined. Furthermore, we examined the association of the genetic serum MBL concentration with systemic infection. The chickens with systemic infection had a statistically significant lower mean serum MBL concentration than the rest of the chickens, suggesting that MBL plays an important role against P. multocida. A statistically significant negative correlation was found between the specific antibody response and the genetic serum MBL concentration for both breeds. This indicates that MBL in chickens is capable of acting as the first line of defence against P. multocida by diminishing the infection before the adaptive immune response takes over.

MHC haplotype and susceptibility to experimental infections (Salmonella Enteritidis, Pasteurella multocida or Ascaridia galli) in a commercial and an indigenous chicken breed.

In three independent experimental infection studies, the susceptibility and course of infection of three pathogens considered of importance in most poultry production systems, Ascaridia galli, Salmonella Enteritidis and Pasteurella multocida were compared in two chicken breeds, the indigenous Vietnamese Ri and the commercial Luong Phuong. Furthermore, the association of the Major Histocompatibility Complex (MHC) with disease-related parameters was evaluated, using alleles of the LEI0258 microsatellite as markers for MHC haplotypes. The Ri chickens were found to be more resistant to A. galli and S. Enteritidis than commercial Luong Phuong chickens. In contrast, the Ri chickens were more susceptible to P. multocida, although production parameters were more affected in the Luong Phuong chickens. Furthermore, it was shown that the individual variations observed in response to the infections were influenced by the MHC. Using marker alleles of the microsatellite LEI0258, which is located within the MHC region, several MHC haplotypes were identified as being associated with infection intensity of A. galli. An association of the MHC with the specific antibody response to S. Enteritidis was also found where four MHC haplotypes were shown to be associated with high specific antibody response. Finally, one MHC haplotype was identified as being associated with pathological lesions and mortality in the P. multocida experiment. Although not statistically significant, our analysis suggested that this haplotype might be associated with resistance. These results demonstrate the presence of local genetic resources in Vietnamese chickens, which could be utilized in breeding programmes aiming at improving disease resistance.

Gastrointestinal helminths in indigenous and exotic chickens in Vietnam: association of the intensity of infection with the Major Histocompatibility Complex.

This study compared the prevalence and intensity of infections of helminths in 2 chicken breeds in Vietnam, the indigenous Ri and the exotic Luong Phuong. Also, possible correlations with the Major Histocompatibility Complex (MHC) were tested. The most prevalent helminths were Ascaridia galli, Heterakis beramporia, Tetrameres mothedai, Capillaria obsignata, Raillietina echinobothrida and Raillietina tetragona. Differences in prevalence and intensity of infection were found between the 2 breeds. Comparing the 2 groups of adult birds, Ri chickens were observed to have higher prevalence and infection intensities of several species of helminths, as well as a higher mean number of helminth species. In contrast, A. galli and C. obsignata were shown to be more prevalent in Luong Phuong chickens. Furthermore, an age-dependent difference was indicated in the group of Ri chickens in which the prevalence and the intensity of infection was higher for the adult than the young chickens for most helminths. The most notable exception was the significantly lower prevalence and intensities of A. galli in the group of adult chickens. In contrast, the prevalence and intensity were very similar in both age groups of Luong Phuong chickens. Using a genetic marker located in the MHC, a statistically significant correlation between several MHC haplotypes and the infection intensity of different helminth species was inferred. This is the first report of an association of MHC haplotype with the intensity of parasite infections in chickens.

Infection and excretion of Salmonella Enteritidis in two different chicken lines with concurrent Ascaridia galli infection.

Studies on the impact of interaction of Salmonella enterica serovar Enteritidis and the parasitic nematode Ascaridia galli with the avian host were undertaken with particular emphasis on infection and excretion of these pathogens in two different layer lines. A total of 148 salmonella-free 1-day-old chickens (73 Hellevad and 75 Lohmann Brown) were randomly divided into five groups for each line. Group 1 served as an uninoculated control group. Groups 2 and 3 were infected with A. galli and S. Enteritidis, respectively. Group 4 was first infected with S. Enteritidis and subsequently with A. galli, and vice versa for group 5. The number of chickens excreting S. Enteritidis was significantly higher (P < 0.001) in the groups infected with both S. Enteritidis and A. galli compared with those only infected with S. Enteritidis over time. Furthermore, excretion of S. Enteritidis over time was significantly higher (P < 0.001) in the group first infected with S. Enteritidis and subsequently with A. galli compared with the group infected in the reverse order. No significant differences were observed between the two lines concerning excretion of S. Enteritidis over time in any group (P = 0.61 (group 3), P = 0.73 (group 4), P = 0.31 (group 5)). A. galli established itself significantly better (P = 0.02) in the group first infected with A. galli and subsequently with S. Enteritidis compared with the group infected in the reverse order. Furthermore, the A. galli infection rate was significantly higher (P = 0.02) in Hellevad chickens compared with Lohmann Brown chickens at the end of the experiment.

Schistosoma japonicum in the pig: the influence of age on the host/parasite relationship.

The current study sought to elucidate a possible association between age and susceptibility to a primary infection with Schistosoma japonicum in pigs. Sixteen Landrace/Yorkshire crossbred specific pathogen-free pigs in three different age groups (group A-C), aged approximately 7, 24 and 37 weeks at the beginning of the experiment, were infected by intramuscular injections of 1,000, 1,500 or 2,400 cercariae, respectively. Fecal egg counts were obtained twice weekly from six to eight weeks post infection (wpi), and the pigs were killed 11 wpi. The number of worms collected were counted and sexed subsequent to perfusion. Tissue egg counts were estimated on samples from the liver. The worm recoveries for group A, B and C were 3.2%, 8.1% and 3.8%, respectively. No differences were observed between the male/female ratios of the three groups. The fecundity parameters, ie, fecal egg counts per mature female and liver egg counts per mature female, showed no significant differences between the three age groups. The results did not indicate any difference in susceptibility between the different age-groups of pigs to a primary infection with S. japonicum.

In vitro maintenance of Schistosoma japonicum and surgical transfer from donor to naïve recipient pigs.

An objective of this study was to find a culture medium and a temperature range suitable for in vitro maintenance of adult Schistosoma japonicum during surgical transplantation experiments. Adult S. japonicum were cultivated in four different media (NCTC 135, NCTC 109, RPMI 1640 and 0.85% physiological saline) supplemented with 10% heat-inactivated normal pig serum (hiNPS) at either 4 degrees C, 22-25 degrees C (room temperature) or 37 degrees C. Based on survival and morphologic evaluation, NCTC 135 at room temperature was found to be the best medium/temperature combination for maintenance of worms. An additional objective was to develop a method for transplanting adult S. japonicum from experimentally infected donor pigs to naïve recipient pigs. Six Landrace/Yorkshire crossbred pigs were used as donors to supply worms for two recipient pigs. Worms for transplantation were obtained by perfusion of the mesenteric veins of the donor pigs and maintained for a maximum of 3 h in NCTC 135 + 10% hiNPS at room temperature. A total of 148 and 132 worms were surgically transferred by way of an infusion tube into caecal veins of the two recipients. Six weeks after transplantation, 14% and 36% of the transferred worms were recovered by perfusion and subsequent manual inspection of the mesenteric veins of the two recipient pigs, respectively. The successful results suggest that surgical transfer of S. japonicum worms from donor to naïve recipient pigs may be useful for future studies on population genetics, dynamics and regulation in the pig/S. japonicum model.