'A child is also a teacher': exploring the potential for children as change agents in the context of a school-based WASH intervention in rural Eastern Zambia

As part of water, sanitation and hygiene interventions in low-income settings, it is frequently assumed that pupils can disseminate information and catalyze change at home, yet this assumption has not been rigorously assessed. We employed qualitative research methods in two phases to assess the potential for children to be change agents in five schools in rural Zambia. Phase 1 included role-play and focus group discussions among pupils on their percieved ability to serve as change agents. Children were then given 'homework' that included information on health messages and on how to build a handwashing station, and were encouraged to engage their family. In Phase 2, we conducted separate focus group discussions with pupils and mothers on their experiences with the 'homework'. We found that, in general, pupils were enthusiastic about engaging with parents-typically male heads of household-and were successful at constructing handwashing stations. Mothers reported high levels of trust in children to relay health information learned at school. Pupils were able to enact small changes to behavior, but not larger infrastructure changes, such as construction of latrines. Pupils are capable of communicating knowledge and behaviors to family members; however, discrete activities and guidance is required.

Influence of animal age on body concentrations of minerals in Japanese quail (Coturnix japonica)

Mathematical modelling of the relationships between mineral inputs and outputs would enable the prediction of mineral requirements of poultry under a wide range of conditions. To establish the feasibility of possible modelling of mineral requirements, the current study aimed to describe the individual mineral concentrations of whole bodies of quail over the life cycle from hatching to 70 days of age. Quail were reared indoors without any restrictions that could limit growth. Sampling of birds (n = 6-18) was carried out at 0, 3, 7, 14, 21, 35, 49 and 70 days after hatching. Freeze-dried samples of whole bodies (digestive contents removed) were analysed for ash, and macrominerals (calcium, magnesium, phosphorus, potassium, sodium) and microminerals (copper, iron, manganese, nickel, selenium, zinc). Ash concentration followed a curvilinear trend, with a maximum of 101.7 g/kg dry matter at 32.77 days. Individual mineral concentrations, expressed as a proportion of ash, were fluctuating over time, with the most prominent changes at 3 days and again at either 14 or 21 days. Dissimilar patterns in individual mineral concentrations resulted that ratios between minerals followed inconsistent patterns over time. Although mineral contents in absolute quantities can be described through modelling over the entire life cycle of the bird, it can be concluded that variable concentrations of individual minerals could complicate further model development.

Pathogenesis of scrapie in ARQ/ARQ sheep after subcutaneous infection: effect of lymphadenectomy and immune cell subset changes in relation to prion protein accumulation

It is well established that the infectious agent of scrapie can replicate in the lymphoreticular system (LRS). However, the effects of removal of LRS target tissues on the pathogenesis of the infection and the accumulation of disease-associated prion protein (PrP(d)) in LRS tissues on specific immune cell subsets are poorly understood aspects. To address these questions 16 ARQ/ARQ sheep were subcutaneously inoculated in the drainage area of the prefemoral lymph node with brain homogenate derived from Suffolk sheep naturally infected with scrapie. Fourteen sheep were then subjected to either early (14-17 days post-inoculation [dpi]) or late (175-201 dpi) lymphadenectomy and culled at preclinical or clinical stages of infection. Neither late nor even early lymphadenectomy prevented infection or had any effect on the accumulation of PrP(d) in the LRS or CNS suggesting a rapid organic dissemination of the infectious agent after inoculation. Lymph nodes from eight scrapie inoculated sheep selected on the basis of the amount of PrP(d) in their LRS tissues (negative, low or high) were examined for six different immune cell markers. The PrP(d) negative lymph nodes from two sheep with no evidence of scrapie infection showed lower numbers of cluster of determination (CD) 21 positive cells than PrP(d) positive nodes, irrespective of their location (hind leg or head). However, quantitative differences in the expression of this marker were not detected when comparing lymph nodes with low and high levels of PrP(d) accumulation, suggesting that proliferation of CD21 positive cells is related to scrapie infection, but not directly linked to the magnitude of PrP(d) accumulation. An additional observation of the study was that sheep that were methionin-threonine at codon 112 of the prion protein gene showed lower attack rates than methionine homozygotes (67% and 100%, respectively) and also generally lower levels of PrP(d) accumulation in the LRS and brain and increased survival times, suggesting an influence of such polymorphism in the susceptibility to scrapie.

Cholesterol content and fatty acid composition of ostrich meat as influenced by subspecies

Two muscles, the m. gastrocnemius and m. iliofibularis, were excised from the left legs of six Red Neck (Struthio camelus massaicus) and six Blue Neck (Struthio camelus australis) ostriches and analysed for lipid and cholesterol content and fatty acid composition. Total lipid (1.43 g 100g ) and cholesterol content (65.63 mg 100g ) did not differ (ps> 0.05) in any muscle between subspecies. Although the percentage of some individual fatty acids differed (p < 0.05), the total percentage of saturated fatty acids and total monounsaturated fatty acids was similar (p > 0.05) between subspecies in both muscles. Although the percentage total polyunsaturated fatty acids was higher (p < 0.05) in Blue Necks (23.78%) than in Red Necks (23.65%) in the m. gastrocnemius, but not (p > 0.05) in the m, iliofibularis, the difference of 0.13% is probably of no practical significance.

Immunophenotype of cells within cervine rectoanal mucosa-associated lymphoid tissue and mesenteric lymph nodes

Rectoanal mucosa-associated lymphoid tissue (RAMALT) is a part of the lymphoid system that can be sampled easily in live animals, especially ruminants. RAMALT biopsy is useful for the diagnosis of transmissible spongiform encephalopathies, including scrapie in sheep and goats and chronic wasting disease (CWD) in cervids. Diagnosis is reliant on detection of abnormal prion protein (PrP(d)), which is associated with lymphoid follicles. For enzyme linked immunosorbent assays (ELISAs) detecting PrP(d) it is necessary to ensure that lymphoid follicles are present in biopsy samples to avoid false-negative results. Monoclonal antibodies known to recognize specific immune cell subsets present in lymphoid tissues of sheep were tested for cross-reactivity with cervine RAMALT and mesenteric lymph nodes (MLNs) preserved in zinc salts fixative. The distribution of cells expressing CD3, CD4, CD79, CD21 and class II molecules of the major histocompatibility complex was determined in these tissues. Cells of each immunophenotype had similar distributions in RAMALT and MLNs and these distributions were similar to those reported previously for sheep and cattle. The identification and validation of cervine lymphoid follicle cell markers (CD79 and CD21) may allow reduction in false-negative results during diagnosis of CWD by ELISA.

Effects of dietary chromium supplementation on performance, carcass characteristics, and meat quality of growing-finishing swine: a meta-analysis

Dietary Cr supplementation has potential to decrease fat and increase lean in carcasses of growing-finishing swine. However, effects of Cr supplementation on performance and economically important carcass and meat quality characteristics varied considerably among studies. Therefore, a meta-analysis was designed to quantitatively describe effects obtained in several independent studies. To accommodate differences in methodology among studies, standardized effect sizes (Hedges's g) were calculated for results from 31 studies, in which Cr was supplemented as complexes of Cr Met chelate, Cr nanocomposite, Cr nicotinate, Cr propionate, Cr tripicolinate, or Cr yeast in diets for growing-finishing swine. Summary statistics were calculated by frequentist fixed and random effects, and hierarchical Bayesian models. With characteristics related to carcass quality, observed heterogeneity (P < 0.10) could not adequately be explained in a meta-regression by differences in initial BW and amount of Cr supplemented. Random effects and Bayesian models to summarize effect sizes for these characteristics showed similar results. According to random effects models, dietary Cr supplementation decreased (P < 0.05) 10th-rib fat thickness (mean effect size = -0.479; 95% confidence intervals = -0.680 to -0.279; 24 studies; 59 comparisons), whereas percentage carcass lean (mean effect size = 0.614; 95% confidence intervals = 0.366 to 0.863; 22 studies; 52 comparisons) and LM area (mean effect size = 0.571; 95% confidence intervals = 0.364 to 0.778; 29 studies; 72 comparisons) increased. Average daily gain and G:F, which did not present heterogeneity, were improved by Cr supplementation, whereas no effects were detected in characteristics (CIE color, drip loss, cook loss, shear force) related to meat quality. Some publication, or other small-study bias, was evident in results on growth and feed efficiency. However, directions of mean effect sizes were not changed by application of the trim-and-fill method to correct for bias.

Dietary vitamin E and lipid and color stability of beef and pork: modeling of relationships

Dietary vitamin E supplementation provides a feasible option to extend the shelf life of meat. However, the costs of extra supplementation necessitate an accurate level of feeding to achieve the maximum return in product quality improvement. The current study aimed to quantify the effects of total dietary vitamin E intake on muscle α-tocopherol concentration in cattle and pigs, and to relate muscle α-tocopherol concentration to lipid oxidation and color of meat. Through computerized and manual searches, 13 studies with cattle and 10 with pigs were identified that have presented data on dietary vitamin E intake and muscle α-tocopherol concentration. Treatment means from 12 studies with beef and 14 with pork were used to evaluate the effects of muscle α-tocopherol concentration on lipid oxidation, as represented by thiobarbituric acid reactive substances in meat stored or retail displayed at chilled temperatures. With CIELAB a* (redness) values as an indicator of color development, the association between muscle α-tocopherol concentration and color could be evaluated with treatment means from 8 studies with beef and 5 with pork. Different treatments applied within studies resulted in 20 to 66 values available for the respective regression analyses. Relationships could be described effectively by different forms of the Mitscherlich model, which presented an initial value for y when x = 0, an asymptotic plateau, and the rate of change of y with increasing values of x. With the inclusion of experiment as a random effect, the relationship between total dietary vitamin E intake (x, IU/d for cattle and mg/d for pigs) and muscle α-tocopherol concentration (y, µg/g of meat) reached asymptotic plateau values at 5.71 and 4.83 µg/g of meat for cattle and pigs, respectively. The fractional accumulation rate (per total dietary vitamin E intake) of muscle α-tocopherol concentration was considerably greater in pigs (0.0130) than in cattle (0.00174). The form of the relationship between muscle α-tocopherol concentration and thiobarbituric acid reactive substances in pork was influenced by a single value, whereas muscle α-tocopherol concentrations could not be related to a* values in beef. This study presented viable models that could be applied in practice to calculate the amounts of supplemental dietary vitamin E needed to obtain the maximum profit from beef and pork.

Relative quantitative kinetics of interferon-gamma and interleukin-10 mRNA and protein production by activated ovine peripheral blood mononuclear cells

Interferon-gamma (IFN-gamma) and interleukin (IL)-10 are cross-regulatory cytokines capable of driving and controlling the adaptive host immune response. The inter-relationship between IFN-gamma and IL-10 expression has not been defined in sheep despite biological evidence suggesting that they perform similar functions to their orthologues described in other species. To address this, we have developed a quantitative (q)PCR method to assess relative levels of IFN-gamma and IL-10 mRNA expression in activated ovine peripheral blood mononuclear cells (PBMC) and compared the kinetics of mRNA expression with amounts of cytokine secreted by the cells over a 96h period. PBMC were collected from sheep immunised with the nominal antigen ovalbumin (Ova) and re-stimulated in vitro with antigen and the T cell mitogen concanavalin A (ConA). The recall response to antigen was characterised by a single peak in IFN-gamma mRNA expression at 48h of culture (13-fold increase over unstimulated cells) and relatively lower expression of IL-10 mRNA (average 2-3-fold increase over the 96h culture period). Antigen-driven IFN-gamma protein concentration was greatest at the end of the culture period (96h) whereas IL-10 protein level was not elevated above that observed in unstimulated cells. The typical response to ConA was greater for both cytokines, with IFN-gamma mRNA expression peaking at 6h of culture (133-fold increase) then declining rapidly whereas IL-10 mRNA expression peaked at 24h (16-fold increase) and declined more gradually. Despite these differences in the relative kinetics of mRNA expression in mitogen-activated PBMC, the typical pattern of protein expression of the two cytokines was similar. Both showed a gradual rise in protein concentration starting from 12h of culture which was still rising at the end of the culture period (96h). These data demonstrate that the kinetics of mRNA expression for IFN-gamma and IL-10 in activated ovine PBMC do not necessarily correlate with detectable protein in culture.

Characterization and time course of pulmonary lesions in calves after intratracheal infection with Pasteurella multocida A:3

Pasteurella multocida A:3 is a common cause of suppurative bronchopneumonia in calves and results in significant production losses and mortality. Here we describe the lesions in three calves at each of four time points (1 day and 4, 7 and 10 days) after experimental intratracheal infection with approximately 1x10(9) colony-forming units of P. multocida A:3 Moredun Research Institute (MRI isolate 671/90). Equivalent age- and time-matched sham-dosed negative control animals were also studied. Infected calves developed significantly elevated mean rectal temperatures (P<0.001) and respiratory rates (P<0.001) compared with negative control animals. Extensive consolidation of multiple lung lobes was present on each of the day/s post-infection (dpi). Histologically, large numbers of alveoli contained either or both polymorphonuclear neutrophils (PMNs) and oedema fluid (1 dpi). At 4 dpi a severe fibrinosuppurative bronchopneumonia had developed. At this time, PMNs and macrophages formed focal lesions containing central necrotic and mineralized debris, while the interlobular septa were severely distended by oedema. Early abscess formation was present in the lung parenchyma at 7 dpi and many of the interlobular septa were thrombosed. At 10 dpi abscesses within the lung parenchyma were mature and comprised of central necrosis with surrounding layers of PMN, macrophages and fibrous tissue. This study describes, for the first time, the commencement, nature and progression of lesions in bovine pneumonic pasteurellosis caused by P. multocida A:3 and provides the foundations for further investigation of the pathogenesis of this disease in cattle.

Proteomic analysis of excretory/secretory products released by Teladorsagia circumcincta larvae early post-infection

Teladorsagia circumcincta is an important parasitic nematode of domestic small ruminants. Drug resistance in this species is common so alternative methods of control are required. As animals develop immunity to T. circumcincta, vaccination is a valid option. Little is known about the antigens that play a role in stimulating immunity at this host/parasite interface. As responses generated between 1 and 5 dpi are known to affect development of these nematodes in their gastric niche, we focused on proteins released during the early stages of infection. To identify molecules potentially involved in immunity, we undertook a proteomics analysis of proteins released from larvae harvested at 1-, 3- and 5-days post-infection (dpi). This analysis produced peptide sequence data that was used to search information available in T. circumcincta expressed sequence tag (EST) databases and enabled identification of a number of excretory/secretory (ES) proteins. Immunoblots were performed to assess the relative molecular weight of ES antigens that were targets of local IgA responses in mucus from sheep rendered immune to infection. ELISA was performed to assess antigen-specific mucus IgA levels in individual sheep. These experiments provided preliminary evidence that the proteins identified in the larval secretome were subject to these antibody responses.

Antigen-specific peripheral immune responses are unaltered during normal pregnancy in sheep

A shift in the balance of T(Helper) (T(H))1/T(H)2 cytokine production by maternal peripheral blood leukocytes is regarded as a common important feature of successful mammalian pregnancy. Although the phenomenon has been studied extensively in animals with invasive hemochorial placentae, the paradigm has not been studied in detail in species with less-invasive placentae, such as sheep that have a synepitheliochorial placenta. Sixteen sheep were immunised with the nominal antigen chicken egg albumin (Ova) and antigen-specific humoral and cellular responses were established in all sheep. The 16 sheep were synchronised, 11 were mated and successfully conceived, the remaining 5 served as non-pregnant controls. Peripheral blood mononuclear cells (PBMC) were isolated approximately every 2 weeks and restimulated in vitro with either Ova or the T cell mitogen concanavalin A (ConA), and cell proliferation and cytokine production measured. There were no detectable differences in antigen-driven PBMC proliferation, interferon-gamma (IFN-gamma), interleukin (IL)-4 or IL-10 production between pregnant and non-pregnant sheep. Also, there were no appreciable differences in ConA-induced IFN-gamma, IL-4 or IL-10 between the groups. These data suggest that a shift in T(H)1/T(H)2 cytokine production does not occur in pregnant sheep and indicate that further comparative reproductive immunology studies on species with non-invasive placentation will be informative of materno-fetal interactions and immune regulation during pregnancy.

The interaction between dam methylation sites and Xba1 restriction digest sites in Escherichia coli O157:H7 EDL933

AIMS

The aim of this study was to gain a better understanding of the reason for the predicted pulsed-field gel electrophoresis (PFGE) pattern for the sequenced Escherichia coli O157:H7 EDL933 (EDL933) being different from that observed in practice, using the restriction enzyme Xba1.

METHODS AND RESULTS

Primers were designed that flanked either side of each of the predicted Xba1 restriction sites, and the resultant PCR products were sequenced. No sequencing errors were found in the published genome. The distribution of dam methylation sites within the genome was investigated, and a new PFGE pattern was predicted by assuming that any Xba1 restriction site that coincided with a dam methylation site would not be cut. The estimated mean band sizes were obtained from six replicate gels. It was found that the observed and predicted PFGE patterns were in good agreement.

CONCLUSIONS

The difference between the observed and the predicted PFGE patterns for EDL933, using Xba1, could be accounted for by assuming that the methylated restriction sites were not cut.

SIGNIFICANCE AND IMPACT OF THE STUDY

PFGE is commonly used as a subtyping method. This study provides additional information about the basic technique that could enhance the interpretation of PFGE patterns in comparative studies of the E. coli isolates.

Immunological differences between susceptible and resistant sheep during the preclinical phase of scrapie infection

In order to investigate the relationship between the immune response to scrapie infection and genetic susceptibility to the disease in sheep, immune cell subsets and prion protein (PrP) expression were determined in susceptible and resistant Suffolk sheep in the preclinical phase of infection. At 6 months of age, 12 ARQ/ARQ (susceptible) and nine ARR/ARR (resistant) scrapie-free Suffolk lambs were challenged subcutaneously with scrapie inoculum. Prefemoral lymphadenectomies were carried out at 14 and 180 days post-inoculation (p.i.) and serial bleeds were collected at monthly intervals for up to 1 year p.i. An indirect double-labelling procedure was carried out on peripheral blood mononuclear cells (PBMCs) and lymph node cell preparations and analysed using flow cytometry. Prior to scrapie challenge, significantly more PrP+cells were detected in PBMCs from the susceptible sheep. Furthermore, following challenge, significantly more CD8+andγΔ+T cells were detected in the PBMCs of the resistant sheep. However, at both 14 and 180 days p.i, CD21+cell expression was significantly higher in the lymph node preparations of the susceptible sheep. In contrast, more CD4+cells were detected in the lymph nodes of the resistant sheep at both time points. It was concluded that significant differences in immune cell subsets and PrP expression occur between ARQ/ARQ and ARR/ARR Suffolk sheep in the preclinical phase of infection.

Role of endogenous transplacental transmission in toxoplasmosis in sheep

To investigate the potential role of endogenous transplacental transmission of Toxoplasma gondii, 31 seropositive ewes presumed to be persistently infected with the parasite and 15 seronegative ewes were mated and monitored throughout pregnancy and lambing. Antibody titres were determined in precolostral sera from the liveborn lambs and in thoracic fluid from the dead lambs. A PCR for the B1 gene of T gondii was applied to the placentas from all the ewes and to the brains of the stillborn lambs. Samples of brain, lung, liver, spleen and heart from the dead lambs were examined by histopathology. No evidence of toxoplasmosis was detected by histopathology or PCR in any of the samples, but low titres of antibody to T gondii were detected in two liveborn, healthy offspring of a seropositive ewe by the immunofluorescent antibody test (3.2 per cent of pregnancies and 4.1 per cent of lambs in the seropositive group). Antibody to specific antigens of T gondii was demonstrated in sera from these two lambs by Western blotting.

Antiviral activity of HPMPC (cidofovir) against orf virus infected lambs

(S)-1-[3-hydroxy-2-(phosphonomethoxy)propyl]cytosine [corrected] (HPMPC, cidofovir, CDV, Vistide) is an acyclic nucleoside analogue with a potent and selective activity against a broad spectrum of DNA viruses including the poxviruses. In this study we present the results of different treatment regimens in lambs experimentally infected with orf virus with different cidofovir formulations prepared in Beeler basis and Unguentum M. Our results show that choice of excipient, concentration of codofovir [corrected] and treatment regimen were all important to the clinical outcome of the therapy. Whilst one particular regimen appeared to exacerbate the lesion, treatment with 1% (w/v) cidofovir cream, prepared in Beeler basis, for 4 consecutive days did result in milder lesions that resolved in milder lesions that resolved [corrected] more quickly than untreated lesions. Furthermore the scabs of the treated animals contained significantly lower amounts of viable virus meaning there should be less contamination of the environment with virus than would normally occur.

Long-term passage of tachyzoites in tissue culture can attenuate virulence of Neospora caninum in vivo

To determine whether prolonged in vitro passage would result in attenuation of virulence in vivo, Neospora caninum tachyzoites were passaged for different lengths of time in vitro and compared for their ability to cause disease in mice. Groups of Balb/c mice were inoculated intraperitoneally with 5×106 or 1×107 of low-passage or high-passage N. caninum tachyzoites. The mice were monitored for changes in their demeanour and body weight, and were culled when severe clinical symptoms of murine neosporosis were observed. Mice inoculated with the high-passage parasites survived longer (P<0·05), and showed fewer clinical symptoms of murine neosporosis, compared to the mice receiving the low-passage parasites. The parasite was detected in the brains of inoculated mice using immunohistochemistry and ITS1 PCR. Tissue cysts containing parasites were seen in mice inoculated with both low-passage and high-passage parasites. When the in vitro growth rates of the parasites were compared, the high-passage parasites initially multiplied more rapidly (P<0·001) than the low-passage parasites, suggesting that the high-passage parasites had become more adapted to tissue culture. These results would suggest that it is possible to attenuate the virulence of N. caninum tachyzoites in mice through prolonged in vitro passage.

Local cytokine responses in Dictyocaulus viviparus infection

The high degree of immunity induced by the bovine lungworm, Dictyocaulus viviparus, makes it an ideal model in which to study nematode-induced protective immune responses. Here, cytokine responses were measured over the course of an experimental infection of D. viviparus. Local cytokine messenger RNA (mRNA) transcripts were measured in lung parenchyma, tracheal rings and draining lymph nodes using semi-quantitative reverse transcriptase-polymerase chain reaction. Responses were measured in animals necropsied at 15, 22 and 43 days post-infection (DPI). The responses elicited at these time points were compared with cytokine levels observed in uninfected animals. Interleukin (IL)-4, IL-5, IL-10, IL-12p35, IL-13 and interferon gamma (IFNgamma) mRNA levels were measured in duplicate at each site. By 42 DPI, very few parasites were recovered, either from faeces or lungs. Transcripts of all cytokines increased in the lung parenchyma, tracheal rings and caudal mesenteric lymph nodes by 15 DPI. The response was rapid and peaked during the time of larval migration through the lungs. By 42 DPI, expression levels of most cytokines were reduced to levels similar to, or below, base line values measured in uninfected animals. Highest levels of IL-10, IL-12p35, IL-13 and IFNgamma transcript were measured in the bronchial lymph nodes of uninfected animals. IgG1 levels were negatively correlated with expression levels of all cytokines. The results demonstrate that a mixed cytokine response occurs over the course of a primary infection during which the parasites were eliminated by day 43 DPI. These results agree with those obtained for other helminths in cattle and challenge the hypothesis that polarised Th2 responses are essential for protection against nematodes in this species. These observations are important in the development of recombinant vaccines, particularly when considering adjuvant choice.

Pathophysiological and immune cell responses in calves prior to and following lung challenge with formalin-killed Pasteurella multocida biotype A:3 and protection studies involving subsequent homologous live challenge

Pneumonic pasteurellosis is a common respiratory infection in cattle that has major economic and welfare implications world-wide and the incidence in the UK due to Pasteurella multocida, currently the same as that associated with Mannheimia haemolytica, is increasing. Whereas much is known regarding the pathogenesis of M. haemolytica infections little information is available on the pathogenic process of pasteurellosis initiated by P. multocida. In the present work calf systemic and innate immune responses to intratracheal challenge with formalin-killed P. multocida biotype A:3 and to subsequent experimental lung infection with live P. multocida were investigated. Eight-week-old calves were challenged intratracheally on day 0 with either 10(9) colony forming units (cfu) of formalin-killed P. multocida biotype A:3 in 300 ml saline (n = 10) or 300 ml saline alone (n = 10), followed, at day 21, by challenge with 10(9) cfu live P. multocida. Pathophysiological and lung phagocyte responses were assessed by clinical monitoring, sequential lung lavage and blood sampling. Results for samples obtained before, during and after challenge showed clinical and acute phase protein responses to both bacterial culture and saline control treatments, although higher responses were associated with bacterial challenge. Phagocytosis of P. multocida during 1h incubation periods with lavaged cells in vitro was unaffected by exposure in vivo to killed P. multocida and there was evidence that P. multocida was able to survive intracellularly during this assay. There was no indication that lung exposure to formalin-killed P. multocida conferred protection against subsequent homologous live challenge.

Methods to determine metabolizable energy and digestibility of feed ingredients in the domestic pigeon (Columba livia domestica)

The influence of length of excreta collection period (1, 3, 6, 10, 14 d) and prefeeding protocol (7 d either individual feeding in collection cages or group feeding in housing cages) on AMEn, nitrogen retention (NR), and apparent DM, organic matter and ether extract digestibility of corn and peas were evaluated in domestic pigeons (Columba livia domestica). In addition, the use of internal markers [acid-insoluble ash (AIA) and acid detergent lignin (ADL)] to determine AMEn, NR, and apparent digestibility was compared with the method of measuring total feed input and excreta output. A quadratic (y = a + bx + cx2) trend in the CV for AMEn, NR, and apparent digestibility coefficients found over collection periods with corn presented evidence that excreta collection for a period of 3 d will produce a CV of 5% less than the minimum CV. Although no trend could be detected in CV for peas, a 3-d excreta collection period resulted in relatively low variation. Both AIA and ADL, when used as internal markers, resulted in AMEn, NR, and digestibility values below (P < 0.05) those obtained with total collection with corn. However, values between markers were comparable (P > 0.05) for all components evaluated. The ADL was unsuccessful as marker with peas. Group prefeeding of pigeons in housing cages resulted in lower feed intake, excreta output, NR, and apparent digestibility than when birds were adapted individually to collection cages. This study presents evidence that the method of measuring total feed intake and excreta output for a period of 3 d, with individual adaptation of birds to collection cages, resulted in the most reliable values for AMEn, NR, and apparent digestibility of DM, organic matter and ether extract of feed ingredients in pigeons.

The pathogenesis of neosporosis in pregnant cattle: inoculation at mid-gestation

To investigate the pathogenesis of bovine neosporosis, 14 pregnant cattle were each inoculated subcutaneously with either 10(7) or 5 x 10(8) Neospora caninum (strain NC1) tachyzoites at 140 days' gestation. Serial necropsies were then carried out over an 8-week period. In the placenta, Neospora DNA and histopathological changes were observed in samples taken 14 days post-inoculation (dpi), with focal necrosis of maternal caruncular septa and fetal placental villi, serum leakage, and a maternal and fetal inflammatory response. At subsequent samplings, pathological changes in the placenta showed signs of resolution. No parasitaemia was detected in the dams in the two weeks following inoculation. In the fetus, Neospora DNA was detected at 14 dpi, and histopathological changes in the fetal central nervous system at 28 and 42 dpi consisted of small foci of necrosis and inflammation. Resolution of placental lesions during the experiment indicated that the disease was being controlled, and fetal infection, although established, did not appear to be progressing to a fatal outcome. The two doses of tachyzoites produced similar results, but the higher dose elicited earlier and more extensive lesions in the placenta and fetus. Control animals remained negative for all parameters recorded. It is concluded that in bovine neosporosis the placenta plays a central role in the pathogenesis and epidemiology of the infection, and that while primary tissue destruction by the parasite may endanger the fetus, the maternal and fetal inflammatory responses may also be damaging.