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.

In vitro inhibition of Clostridium difficile and Clostridium perfringens by commercial probiotic strains.

Probiotics have gained importance in human and veterinary medicine to prevent and control clostridial enteric disease. Limited information is available on the ability of different probiotic bacteria used in food products to inhibit Clostridium difficile and Clostridium perfringens. The objective of this study was to examine the in vitro inhibitory effects of selected commercial bacterial strains on pathogenic clostridia and their growth characteristics under simulated gastrointestinal conditions. The inhibitory effects of 17 commercial strains of Lactobacillus (n = 16) and Bifidobacterium (n = 1) on the reference strains of C. difficile and C. perfringens were assessed by an agar well diffusion assay and by a broth culture inhibition assay using cell-free supernatant harvested at different growth phases, with and without pH neutralization. To study growth characteristics, probiotic strains were cultivated in different acid and bile environments, and growth in the modified media was compared to growth in standard medium. In the agar well diffusion assay, supernatant obtained from two probiotic strains inhibited the growth of both reference and clinical strains of C. perfringens. This effect as seen when supernatant was assessed with and without pH neutralization. Supernatants obtained from 10 probiotic strains inhibited C. difficile only when supernatant was added without pH neutralization. In the broth culture inhibition assay, growth of C. perfringens and C. difficile was inhibited by supernatant without pH neutralization from 5 and 10 probiotic strains, respectively. All potential probiotic strains were able to grow at pH 4.0 and in the presence of 0.15% and 0.3% bile but none were able to grow or survive at pH 2.0. Altogether five probiotic strains [Lactobacillus plantarum (n = 2), Lactobacillus rhamnosus (n = 2), Bifidobacterium animalis lactis (n = 1)] were shown to inhibit all strains of C. difficile and C. perfringens. The inhibitory effect was probiotic strain-specific. Two strains showed a pH-independent inhibitory effect likely due to production of either antibiotics or bacteriocins inhibiting C. perfringens only. These strains have favourable growth characteristics for use as probiotics and their efficacy as prophylactic or therapeutic measures against clostridial enteric disease should be further evaluated by clinical trials in animals.

World association for the advancement of veterinary parasitology (WAAVP): Second edition of guidelines for evaluating the efficacy of anthelmintics in poultry.

This revision of the original poultry guidelines has been prepared to assist in the planning, conduct and interpretation of studies designed to assess the anthelmintic efficacy of drugs (newly discovered or currently used) against helminth parasites of chickens and turkeys. The original set of poultry guidelines was published in 2003. The current version provides an update on procedures to study and quantify the most important helminth parasites of chickens and turkeys, and to integrate these poultry guidelines with a new series of general, reflective and host-specific guidelines relative to assessing anthelmintic efficacy in production and companion animals. General considerations required for the conduct of studies designed to evaluate anthelmintics regardless of animal host such as the selection of study animals, animal housing, feeding, study design, record keeping and statistical analysis are for the most part provided in the newly published general guidelines. Taken together, the general and poultry guidelines should help investigators and others design and conduct studies and evaluate data concerned with determining the efficacy and safety of anthelmintics in chickens and turkeys. Additionally, this revision draws attention to several timely considerations inherent to anthelmintic evaluations such as the need to properly collect helminth specimens for subsequent determinations (e.g. species and stage verification, helminth genotyping). The investigations addressed herein, will most likely provide the very first public record of a new product's abilities to effectively reduce targeted, helminth infections in animals, and particular attention should be focused on study excellence and accuracy. Due to changes in consumer preferences, and new regulatory requirements, poultry husbandry, especially regarding laying hens, has changed immensely in many countries since the publication of the first poultry guidelines. These changes have generally allowed for a much greater exposure of birds to the source of helminth challenge (litter and fields as opposed to cages). Parasitic helminthiosis of poultry has therefore greatly increased in incidence and magnitude; changes that accentuate the need for more effective anthelmintic intervention and an update on the means of determining anthelmintic efficacy.

Multi-locus sequence typing and plasmid profile characterization of avian pathogenic Escherichia coli associated with increased mortality in free-range layer flocks.

Avian pathogenic Escherichia coli strains originating from 10 free-range layer flocks were characterized by multi-locus sequence typing and plasmid profile analysis to investigate their phylogenetic relationship and diversity, respectively. In addition to colibacillosis, all flocks tested positive for antibodies against avian metapneumovirus (aMPV) during production, and six of the flocks were concurrently affected by histomonosis. Accumulated average mortality for flocks concurrently affected by colibacillosis and histomonosis made up 17.4%, while the average mortality for E. coli-infected flocks was 16.5%. A total of eight different sequence types (STs) and 47 different plasmid profiles were demonstrated among the E. coli isolates. Within each flock between one and four different STs and between three and 13 different plasmid profiles were demonstrated. A statistical significant difference in STs and plasmid profile diversity of the population of E. coli was not demonstrated between flocks affected by histomonosis compared with histomonosis-free flocks. Only minor clonal diversity was demonstrated for each flock, and in all but one flock colibacillosis started before antibodies against aMPV were detected. All isolates, except two, carried plasmids greater than 100 kb, but only a single plasmid replicon type, IncFIB, was demonstrated, suggesting plasmids representing this type might represent a common pathogenicity factor for the different STs of E. coli. Within each flock a clonal tendency was observed, indicating that only certain clones of E. coli possess a significant pathogenic potential. These clones act as primary rather than secondary pathogens, resulting in colibacillosis without predisposing factors, including histomonosis and aMPV.

Causes of mortality in commercial organic layers in Denmark.

A longitudinal study investigated the courses of mortality in commercial free-range organic layer flocks in Denmark. In total, 15 organic egg-producing flocks from 11 farms were randomly selected among 80 farms registered in Denmark. Four farms with confined egg production on deep litter were included for comparison. Flock sizes ranged from 2260 to 5940 layers. The flocks were monitored from introduction to the layer farm until slaughter. Flock mortalities ranged from approximately 2% to 91%, with a mean of 20.8% for organic flocks compared with 7% for confined flocks on deep litter. In total, 4608 layers were submitted for postmortem examination, representing > 40% of all the dead layers in the investigated flocks. Outbreaks of erysipelas (Erysipelothrix rhusiopathiae) and fowl cholera (Pasteurella multocida) were observed in two and three organic flocks, respectively. The mortality rate reached 91% in one organic flock dually affected by erysipelas and fowl cholera. In six organic flocks, outbreaks of blackhead were diagnosed. Concurrent infections of erysipelas and blackhead were diagnosed in one organic flock. Escherichia coli infections in the form of septicemia were identified in all organic flocks. In addition, cannibalism and constipation contributed significantly to the mortality in some organic flocks. In the confined deep litter flocks, E. coli infection, constipation, and cannibalism represented the most common causes of mortality.

Consequences of concurrent Ascaridia galli and Escherichia coli infections in chickens.

Three experiments were carried out to examine the consequences of concurrent infections with Ascaridia galli and Escherichia coli in chickens raised for table egg production. Characteristic pathological lesions including airsacculitis, peritonitis and/or polyserositis were seen in all groups infected with E. coli. Furthermore, a trend for increased mortality rates was observed in groups infected with both organisms which, however, could not be confirmed statistically. The mean worm burden was significantly lower in combined infection groups compared to groups infected only with A. galli. It was also shown that combined infections of E. coli and A. galli had an added significant negative impact on weight gain.

Test and validation of methods to sample and detect human virus from environmental surfaces using norovirus as a model virus.

BACKGROUND: Viruses cause a major proportion of human infections, especially gastroenteritis and respiratory infections in children and adults. Indirect transmission between humans via environmental surfaces may play a role in infections, but methods to investigate this have been sparse. AIM: To validate and test efficient and reliable procedures to detect multiple human pathogenic viruses on surfaces. METHODS: The study was divided into two parts. In Part A, six combinations of three different swabs (consisting of cotton, foamed cotton, or polyester head) and two different elution methods (direct lysis or immersion in alkaline glycine buffer before lysis) were tested for efficient recovery of human norovirus GII.7 and mengovirus from artificially contaminated surfaces. In Part B we determined the detection limit for norovirus GI.1 and GII.3 using the best procedure found in Part A linked with a commercial multiplex real-time quantitative polymerase chain reaction detection assay. FINDINGS: Combining the polyester swab with direct lysis allowed recovery down to 100 and 10 genome copies/cm(2) of norovirus GI.1 and GII.3, respectively. This procedure resulted in the significant highest recovery of both norovirus and mengovirus, whereas no differences in amplification efficiencies were observed between the different procedures. CONCLUSION: The results indicate that it is possible to detect low concentrations of virus on environmental surfaces. We therefore suggest that a polyester swab, followed by direct lysis, combined with a multiplex qPCR detection assay is an efficient screening tool that merits study of different respiratory and gastrointestinal viruses on environment surfaces.

Pigs become infected after ingestion of livers and lungs from chickens infected with Ascaris of pig origin.

An experimental infection with Ascaris of pig origin showed that Ascaris suum larvae can migrate extra-intestinally in chickens. Furthermore, after feeding piglets with Ascaris infected chicken liver and lungs, it was possible to recover larvae from their lungs. These observations suggest that the chicken could serve as a paratenic host for Ascaris. There is also the possibility for zoonotic transmission if raw chicken livers are consumed by humans.

Persistent and acute diarrhoea as the leading causes of child mortality in urban Guinea Bissau.

An investigation of child mortality in a semi-urban community, Bandim II, in the capital of Guinea Bissau was carried out from April 1987 to March 1990. 153 deaths were recorded among 1426 live-born children who were followed for 2753 child-years. The under-five mortality risk was 215 per 1000 children (95% confidence interval [CI] 176-264), infant mortality 94 per 1000 (95% CI 73-115), and perinatal mortality 52 per 1000 (95% CI 41-63). By prospective registration of morbidity, post-mortem interviews, and examination of available hospital records, a presumptive cause of death was established in 86% of the deaths. Persistent and acute diarrhoea were the most frequent causes of death, accounting for 43 and 31 deaths per 1000 children, respectively. Fever deaths (possibly malaria), neonatal deaths, acute respiratory infections, and measles were other frequent causes. The access to health services was relatively easy: 75% of the children who died had attended for treatment at a hospital or a health centre. It is important to find ways of preventing and managing persistent diarrhoea, the major cause of death, and to improve the control of acute diarrhoea by a targeted approach.

Virulence of Pasteurella multocida subsp. multocida isolated from outbreaks of fowl cholera in wild birds for domestic poultry and game birds.

Chickens, turkeys, partridges and pheasants were experimentally infected with Pasteurella multocida subsp. multocida to investigate whether outbreaks of fowl cholera in avifauna might represent a risk for organic, backyard and industrial poultry production. Birds were infected intra-tracheally with a strain of P. multocida subsp. multocida (40605-1) isolated from outbreaks of fowl cholera in wild birds in Denmark. P. multocida subsp. multocida strain P-1059 was included as a reference strain. The outbreak strain was highly virulent for turkeys, partridges and pheasants, while chickens were more resistant. The present findings underline the importance of wild birds as a reservoir for P. multocida. Intratracheal challenge proved useful for studying the virulence of P. multocida.

A case-control questionnaire survey of risk factors for porcine reproductive and respiratory syndrome (PRRS) seropositivity in Danish swine herds.

Sixty-eight case herds seropositive to porcine reproductive and respiratory syndrome (PRRS) were compared to 128 seronegative controls in a double-blinded questionnaire survey. The study indicated no increased risk of PRRS seropositivity for herds using artificial insemination with semen from PRRS seropositive AI-stations. Also the herd-size was non-related to the risk of PRRS seropositivity, indicating that air-borne spread of PRRS may not have been a predominant feature in Denmark. Introduction of replacement breeding animals from seropostive breeding- and multiplying herds significantly increased the risk of a herd being PRRS seropositive, as did introduction of 25 kg pigs for feeding. PRRS seropositivity was in the farmers' opinions associated with abortions in sows, early farrowing, high postweaning mortality and low weight gain in fattening pigs. However, the reported frequencies of probelms were relatively low.

The effect of concurrent infections with Pasteurella multocida and Ascaridia galli on free range chickens.

Pasteurella multocida and Ascaridia galli are observed with high prevalences in free range chickens in Denmark, but the impact is unknown. A study was carried out to examine the interaction between A. galli and P. multocida in chickens and the impact on production. Five groups, each with 20 18-week-old Lohmann Brown chickens were infected. Group 1 was orally infected with 1000+/-50 embryonated A. galli eggs. Group 2 received 10(4) cfu P. multocida intratracheally. Group 3 was infected with A. galli and subsequently with P. multocida. Group 4 was infected with P. multocida followed by A. galli. Group 5 was the control. The study ran for 11 weeks where clinical manifestations, weight gain and egg production were recorded. Excretion of P. multocida was determined on individual basis and blood smears were made for differential counts. At the end of the study pathological lesions and the number of adult worms, larvae and eggs in the faeces were recorded. The birds were more severely affected when infected with both pathogens compared to single infections with A. galli or P. multocida, respectively. A lower weight gain and egg production was observed with dual infections. A. galli infection followed by a secondary P. multocida infection resulted in more birds with pathological lesions and continued P. multocida excretion. In conclusion a negative interaction between A. galli and P. multocida was observed and it is postulated that free range chickens are at higher risk of being subjected to outbreaks of fowl cholera when they are infected with A. galli.

The development of Plasmodium gallinaceum infections in chickens following single infections with three different dose levels.

In the present study, groups of 5-day-old chickens were inoculated intravenously with approximately 10(6), 10(4) or 10(2) P. gallinaceum-infected erythrocytes. The outcome of disease in relation to dose level was evaluated in terms of number of parasitized erythrocytes, change in number of erythrocytes, pathological changes of organs and the course of exo-erythrocytic stages of the parasite in various organs over a period of 8 weeks. Mean weight gain and mortality were also recorded. With regard to differences between the size of the inoculation dose and the severity of disease, relationships could be observed in relation to clinical signs, mortality, prepatent period, exo-erythrocytic parasites and severity of pathological changes in organs, but in relation to weight gain, erythrocyte loss and number of parasitized erythrocytes no relationships were observed.

The effect of Plasmodium gallinaceum on a challenge infection with Ascaridia galli in chickens.

The effect of a primary infection with the haemoparasite Plasmodium gallinaceum on the establishment of a challenge infection with the nematode Ascaridia galli in chickens was studied. Four groups were infected as follows. Group 1: inoculated intravenously with 10(6) P. gallinaceum-infected erythrocytes on day 0; group 2: orally infected with 500 embryonated A. galli eggs on day 10; group 3: infected with P. gallinaceum on day 0 and A. galli on day 10; and group 3: non-infected control birds. The results of this investigation demonstrates that a primary infection with P. gallinaceum in chickens alters the course of a subsequent infection with A. galli. Thus, an antagonistic effect was seen in which the malaria infection caused a significant reduction on the establishment of the nematode in concurrently infected animals.

Genetic resistance to Ascaridia galli infections in chickens.

Ascaridiosis is still a cause of economic losses in modern poultry production systems. Improving genetic resistance to this disease provides an attractive alternative for free-range organic poultry producers and will eventually reduce the extensive use of anthelmintic drugs. An experiment was conducted to compare resistance to Ascaridia galli infections in Lohman Brown (LB) and Danish Landrace (DL) chickens. A self-cure mechanism to A. galli infections was observed in both breeds. However, significantly higher worm burdens and egg excretion were seen in the DL compared to LB chickens during primary infection. This indicates that breeding for resistance to A. galli is possible in chickens.

Host age only partially affects resistance to primary and secondary infections with Ascaridia galli (Schrank, 1788) in chickens.

Two experiments were conducted to compare the effect of chickens' age on resistance to primary and secondary infections with Ascaridia galli. In Experiment I, three groups, each of 80 female Lohman Brown chickens, aged one day, one month, or four months were compared. Within each group, 54 chickens were infected orally with 500 embryonated eggs and 26 were kept as non-infected controls. Weights were recorded weekly and five chickens in each group were slaughtered every 2 weeks for worm counts. At week 10 post-infection, 17 of the infected chickens and 18 of the controls were challenged with 500 eggs. In a replicate experiment (Experiment II), 35 one-day-old and 53 one-month-old female Lohman Brown chickens were infected orally with 500 A. galli eggs. Weights and fecal egg counts were recorded every week and infected chickens were necropsied every two weeks for determination of the worm burden. Chickens infected at one month of age excreted significantly fewer A. galli eggs when measured at 14 weeks of inoculation. The worms recovered from the one-month-old age group were significantly shorter than those from the chickens infected at one day of age in the first experiment. Worm burden and female fecundity values, however, were not significantly different between age groups in both Experiments I and II. Weight gains of infected chickens were not significantly different from the controls' and only a few chickens exhibited occasional slight diarrhea in both experiments. The results from these experiments demonstrate that the chickens' age only partially influences resistance to A. galli infection.

Zoonotic risk of Toxocara canis infection through consumption of pig or poultry viscera.

The potential zoonotic risk of Toxocara canis infections from consumption of swine or poultry viscera containing larvae was assessed using a pig model. Two groups of six pigs were fed either fresh swine viscera (group FS) or poultry viscera (FP) containing around 3500 Toxocara larvae. Another two groups of six pigs were fed swine viscera (PS) or poultry viscera (PP) preserved at 4 degrees C for 1 week. All pigs were necropsied 14 days after the exposure. Liver white spots were counted and T. canis specific IgG antibodies were measured by ELISA. Larval burdens were assessed in the mesenteric lymph nodes, liver, lungs, brain, tongue, and eyes. All recipient pigs exhibited several white spots on the liver surface and detectable antibody levels. Larvae were recovered predominantly from the lungs, but also from the mesenteric lymph nodes and the liver, a few larvae were found in the brain and tongue of the pigs. Two larvae were found in the eyes of two pigs in group FS. Mean percentages of total larval recoveries in groups FS, FP, PS, and PP were 75.3, 63.6, 42.6, and 18.8%, respectively. Significantly higher numbers of larvae were recovered from pigs given swine viscera than pigs given poultry viscera. The preservation at 4 degrees C for 1 week caused a significant reduction in the larval infectivity overall, nevertheless, the recoveries remained substantial. The fact that larvae migrating in swine or poultry organs and tissues have high infectivity in pigs even after preservation at 4 degrees C for 1 week, suggests that human infection with T. canis might easily occur following consumption of raw or undercooked dishes, either fresh or refrigerated, prepared from swine or poultry organs and tissues harbouring T. canis larvae.

Tetrameres americana Cram (1927) populations in chickens infected with different dose levels.

Three groups of 20-45 Lohman brown chickens aged 3 weeks were orally infected with doses of 25, 100 and 400 Tetrameres americana, respectively. Fifteen chickens were kept as uninfected controls. Every third week in a period of 12 weeks, 5-15 chickens were slaughtered and the proventriculi were examined for the presence of adult stages of T. americana. From day 21 post-infection, pooled feacal samples were examined for parasite eggs, whereas the weight gain of the chickens was monitored weekly. The parasite established the infection in similar rates in all the three groups, 9.5-15.2%, except on day 84 post-infection, when the establishment rate of the high-dose group was significantly lower (P < 0.005). The average worm burden increased with increasing dosages, though displaying the worm burden of the high-dose group as being roughly halved on day 84 post-infection, thus suggesting an expulsion of worms. Females were more abundant than males. The mean lengths of male and female specimens showed no significant differences between the groups. The egg output was also increased with increasing dosages with the earliest prepatent period of 38 days post-infection found in the high-dose group. Infected chickens exhibited no difference in weight gain in comparison with the controls. This study demonstrated that single infections with varying doses influenced the establishment rate and the worm burden but not the parasites egg excretion, worm size nor the weight gain and mortality of the final host.

Parasites in cross-bred pigs in the Upper East region of Ghana.

A cross-sectional study was carried out in the Upper East Region (UER) of Ghana in order to estimate the prevalence of parasitic infections in local cross-bred pigs. Out of 60 villages with a human population of 200-1000 inhabitants, 10 villages were randomly selected for the study. The number of pigs varied from 50 to 200 pigs per village. In total 259 faecal samples from growers were collected and examined. Ninety-one percent of the animals excreted parasite eggs. Among these the prevalence of Eimeria spp. was 77.2%, Isospora suis (27%) and Balantidium coli (19.3%).The following helminth eggs were identified: Metastrongylus salmi (19.3%); Physocephalus sexalatus (17.4%); Oesophagostomum spp./Hyostrongylus rubidus (60.6%); Trichuris suis (4.6%); Ascaris suum (12.7%); Ascarops strongylina (8.1%); Brachylaemus suis (1.9%); Paragonimus suis (0.8%); Globocephalus urosubulatus (2.7%); and Schistosoma suis (0.4%). Furthermore, six growers were selected from each village for clinical and postmortem examinations, i.e. 60 in total. The clinical examinations revealed ectoparasites on 98.3% of the animals. The ectoparasites were: Haematopinus suis (66.7%); Boophilus spp. (58.3%); Amblyomma spp (45.0%); Sarcoptes suis (38.3%); and Rhipicephalus spp. (8.3%). All pigs were examined for the presence of haemoparasites. It was found that 23.3% of the animals had haemoparasites. These were: Babesia perroncitoi (23.3%); Babesia trautmanni (13.3%); and Eperytrozoon suis (1.7%). Based on postmortem examinations the following adult worms were identified: Metastrongylus salmi (83.3%); Oesophagostomum dentatum (63.3%); Oesophagostomum quadrispinulatum (38.3%); Hyostrongylus rubidus (23.3%); Ascarops strongylina (76.7%); Globocephalus urosubulatus (20.0%); Strongyloides spp. (1.7%); and Physocephalus sexalatus (65.0%). Cysts of the human tapeworm Taenia solium, Cysticercus cellulosae, were present in 11.7% of the animals. Small pieces of the diaphragm were examined for the presence of Sarcocystis spp.. The prevalence was 28.3%, but no larvae of Trichinella spp. were found. Furthermore, four of the animals (6.7%) had Taenia hydatigena cysts.

Prevalence and distribution of gastro-intestinal helminths and haemoparasites in young scavenging chickens in upper eastern region of Ghana, West Africa.

We conducted a cross-sectional study to determine the prevalence and species of gastro-intestinal helminths and haemoparasites in 100 chickens kept under extensive management systems in Ghana, West Africa. All the examined chickens (100%) were infected with gastro-intestinal helminths; a total of 18 species were detected. The species and their prevalences were: Acuaria hamulosa (25%), Allodapa suctoria (20%), Ascaridia galli (24%), Capillaria spp. (60%), Choanotaenia infundibulum (13%), Gongylonema ingluvicola (62%), Heterakis gallinarum (31%), H. isolonche (16%), Hymenolepis spp. (66%), Raillietina cesticillus (12%), R. echinobothrida (81%), R. tetragona (59%), Strongyloides avium (2%), Subulura strongylina (10%), Tetrameres fissispina (58%), Trichostronygylus tenuis (2%), and finally one unidentified acanthocephalan (1%) and one unidentified trematode (1%). Thirty-five per cent of the chickens were infected with the haemoparasites Aegyptinella pullorum and Plasmodium juxtanucleare (prevalences 9% and 27%, respectively). Association between chicken sex and prevalences was not significant. An over-dispersed distribution was seen for most of the helminth species.