Pathogenesis of Eimeria praecox in chickens: virulence of field strains compared with laboratory strains of E. praecox and Eimeria acervulina

The pathogenesis in chickens of the apicomplexan Eimeria praecox was compared with that of Eimeria acervulina, using intestinal lesions, mucosal integrity, body weight gain (BWG) and the feed conversion ratio (FCR) as criteria. Characteristics of each species were described by combinations of polymerase chain reaction assays and classic parasitological signs. There were considerable overlaps in lengths, breadths, shape indices and volumes of the oocysts of each species. Both species caused statistically significant reductions in BWG at the lowest inocula tested (500,000 sporulated oocysts per bird of E. praecox and 250,000 of E. acervulina). E. praecox was observed for the first time to cause actual body weight loss and marked increases in FCR, as did E. acervulina. E. acervulina caused gross, white pathognomonic lesions, but E. praecox caused micro-lesions, visible in fresh tissue only with a dissecting microscope. Occasionally, lesions of the Houghton strain of E. acervulina were observed to be rounded, rather than typically "ladder-like". Both species caused villous erosion and atrophy. No mortality occurred in birds receiving up to 1 million sporulated oocysts of either species. Using BWG and FCR as criteria, the virulence of recent field strains of E. praecox from Wales (Tynygongl) and the USA (Raleigh) was compared with English laboratory strains of E. praecox (Houghton) and E. acervulina (Houghton). E. praecox (Tynygongl) was markedly more virulent than E. acervulina (Houghton), which was more virulent than E. praecox (Raleigh) and E. praecox (Houghton).

[Analysis of the duration of and reasons for changing the first combination of antiretroviral therapy]

OBJECTIVE

To determine the duration of and reasons behind changing the various combinations of drugs used for the initiation of antiretroviral treatment in naïve patients.

METHODS

A retrospective observational study that included all patients with HIV infection who started antiretroviral therapy in a high-tech university reference hospital during the period from 1 January 2003 and 31 December 2005. Patients were followed until 31 December 2008. To estimate the cumulative probability of discontinuation the Kaplan-Meier method was used.

RESULTS

A total of 441 patients were included. The average duration of the first treatment was 384 (interquartile interval 84-1290) days. The regimen based on non-nucleoside reverse transcriptase inhibitors and those that included as nucleosides abacavir or tenofovir in combination with lamivudine or emtricitabine showed a significantly longer duration than the rest. The main reasons for termination were the side effects, although in a lesser percentage than that obtained in previous studies. No associations were found between the rest of the characteristics of the patients or of the treatment and the risk of termination.

DISCUSSION

Although the duration of the first antiretroviral treatment remains short, currently fewer changes are made due to side effects and due to loss to follow-up. The reasons may be better tolerance and less complexity. However, more studies are needed to determine the benefits of one regimen or another, and to be able to generalise the results.

DIFFERENCES IN HSP70 EXPRESSION IN THE SPOROZOITES OF THE ORIGINAL STRAIN AND PRECOCIOUS LINES OF EIMERIA TENELLA

The levels of expression of Heat shock protein 70 (Hsp 70) in sporozoites of a wild-type parent strain and 2 precocious lines of Eimeria tenella, were compared to investigate the relationship between the heat shock proteins expressed by the parasite and virulence of the strain. Hsp70 expression was analyzed in sporozoites by immunohistochemical techniques, immunoblot, and flow cytometric analyses. One band of 70 kDa was identified and the variation of the Hsp70 expression levels was quantified by optical densitometric analyses. The results showed a significant gradual decrease in the Hsp70 expression in sporozoites of E. tenella as attenuation progressed, suggesting that the Hsp70 expressed in the excysted sporozoites of E. tenella might be involved in parasite pathogenicity. In addition, the cytoplasmic distribution of the Hsp70, which was observed in the entire sporozoites of the wild strain, was reduced to the anterior portion in the precocious lines.

Expression of anti-apoptotic factors in cells parasitized by second-generation schizonts of Eimeria tenella and Eimeria necatrix

Intracellular infections by parasites require a functional anti-apoptotic mechanism for parasite survival within the host cell. The intracellular cycle of Eimeria tenella and Eimeria necatrix in chicken intestinal cells involves the maturation of schizonts within the epithelial cells lining the crypt lumen of the ceca (E. tenella) and jejunum (E. necatrix). After invasion, these cells detach from the epithelial layer and migrate into the underlying connective tissue, where maturation of second-generation schizonts takes place. However, the detached epithelial cells that harbour the parasite and localize in the lamina propia do not undergo apoptosis despite the fact that they are parasitized cells and are located in an inappropriate microenvironment. In this study we consider the hypothesis that E. tenella and E. necatrix may inhibit the host cell apoptosis that accompanies parasite-mediated transformation during late schizogony. To that end, the expression of both NF-kappaB, a transcriptional factor that blocks parasite-induced apoptosis, and bcl-xL, an anti-apoptotic protein induced by NF-kappaB, were studied in the host cell during the maturation of second-generation schizonts. In addition, the expression of the phosphorylated inhibitor of NF-kappaB, p-IkBalpha, was also studied to further confirm NF-kappaB activation. Immunocytochemical techniques, flow cytometric and blott analysis were applied by using polyclonal antibodies that specifically react with bcl-xL, p-IkBalpha, and NF-kappaB to detect these anti-apoptotic proteins in the parasitized cell. Our results offer evidence that both these coccidial species first induce NF-kappaB activation to protect the transformed parasitized cells from apoptosis, allowing the second-generation schizonts to mature, and later, after complete schizonts maturation, cause NF-kappaB inhibition to trigger host cell apoptosis in order to facilitate the escape of merozoites. To determine whether inhibition of the NF-kappaB pathway would induce apoptosis of the host cell, a protease inhibitor (TPCK), which induces apoptosis by mediating inhibition of IkB phosphorylation, was administered to parasitized chickens.

Prevalence and analysis of potential risk factors for Cryptosporidium parvum infection in lambs in Zaragoza (northeastern Spain)

An epidemiologic study was carried out to investigate the prevalence of and to identify factors associated with the risk of Cryptosporidium infection in sheep in Zaragoza (northeastern Spain). Faecal samples from 583 lambs aged from 1 day to 3 months and 205 ewes older than 1 year were collected at 89 farms in the two regions of the province of Zaragoza with the highest sheep population (Zaragoza and Ejea de los Caballeros). In every sheep farm, data of the factors potentially associated with the likelihood of C. parvum infection were analysed: geographical location, season, size of herd, number of lambs in the herd at sampling time, lambing period, cleaning of lambing area and presence of diarrhoeic lambs in the farm. C. parvum oocysts were identified by using the Ziehl-Neelsen technique in 344 lambs (59%) from 75 farms (84.4%). Infected lambs ranged from less than 7 days to 90 days of age, although the percentage of animals shedding oocysts peaked at 8-14 days of age (76.2%). Statistical analysis showed that infection rates were significantly higher in lambs aged between 1 and 21 days (66.4%) than in those aged between 22 and 90 days (23%) (P<0.0001, chi(2)). Analysis of correlation between excretion of oocysts and diarrhoea revealed a relationship in all age groups and the probability of presenting diarrhoea was significantly higher for lambs shedding oocysts (86.3%) than for those which did not excrete the parasite (32.2%) (P<0.0001, chi(2)). Similarly, cryptosporidial infection rates were significantly higher in diarrhoeic (79.4%) than in non-diarrhoeic lambs (22.4%). Furthermore, infection intensity was correlated with the presence of clinical symptoms. Presence of diarrhoeic lambs in the farm was the only factor significantly associated with an increased risk of infection since the percentage of herds testing positive was significantly higher in farms with diarrhoeic lambs (91.3%) than in those without cases of neonatal diarrhoea (12.5%) (P<0.0001, chi(2)). Factors associated with a decreased risk of C. parvum infection in lambs included low numbers of lambs in the farm and cleaning of the lambing area. Additionally, lambs 8-14 days of age were less likely to be infected at the first lambing period and in spring/autumn. Cryptosporidial infection was also detected in 16 ewes (7.8%) which excreted few oocysts and without diarrhoea.

Serum antibody response and Cryptosporidium parvum oocyst antigens recognized by sera from naturally infected sheep

The response of specific serum immunoglobulins (IgG, IgM and IgA) and the major antigens of Cryptosporidium parvum recognized by these isotypes were investigated by using enzyme-linked immunosorbent assay and immunoblot techniques in lambs and ewes naturally infected throughout an outbreak of cryptosporidiosis. Serum samples were collected from 20 lambs the first day they showed diarrhoea (D1), and Days 11 and 22, in addition to single serum samples from 17 of their dams. Serum anti-C. parvum IgG, IgM and/or IgA antibodies were detected in lambs as early as Day 1. Levels of IgM antibodies remained steady from D1 to D11 and increased at D22, whereas the IgG response decreased from D1 to D11 and subsequently increased. In contrast, IgA antibodies rapidly fell from D1 and all lambs were seronegative at D11 and D22. The highest levels of specific antibodies were detected in sera from ewes. In fact, all ewes were seropositives for IgM and IgA isotypes and most (16/17) showed positive levels of IgG. Four protein fractions (37-39, 42-48, 51-57 and 60-69 kDa) were the most frequently recognized by IgG and IgM from lamb sera. A low molecular weight fraction (12-14 kDa) reacting with IgG and IgA in most lamb sera was scarcely recognized by IgM and three broad bands were frequently recognized by IgA antibodies (23-25, 51-57 and 90-95 kDa). The recognition pattern of 23-25 kDa peptides by IgA from lamb sera clearly increased with the age. Peptides of 42-48, 51-57, 60-69 and 71-78 kDa were most frequently recognized by IgG and IgM from ewe sera. In relation to IgA antibodies from ewe sera, a frequent immunoreactivity was found with proteins in the intervals between 12 and 22 kDa as well as between 32 and 34 kDa and practically all sera reacted with fractions from 42 to 95 kDa.

Eimeria tenella: hsp70 expression during sporogony

There is an increasing interest in identifying the parasite components involved in the maturation, development, and infectivity of intracellular protozoan parasites. In the present study, a heat shock protein (hsp) of the family of 70 kDa hsp (hsp70), which play important roles in the stage conversion and virulence of these parasites, was examined. Whereas hsp70 expression has been examined in Eimeria tenella within host tissues, in the present study, oocysts of E. tenella were used to investigate the expression of hsp70 during sporulation without interference from the host; hsp70 expression during excystation was induced by incubating sporulated oocysts under various experimental conditions to produce the stimuli necessary for sporozoites to become active and to excyst in vitro. Hsp70 was detected by immunohistochemical techniques; quantitative flow cytometric analysis was also been carried out using specific monoclonal antibodies against hsp70. Hsp70 was expressed during sporulation but was not found in sporulated oocysts after the completion of sporulation. Oocysts re-expressed hsp70 when excystation was induced. The presence of hsp70 prior to infection may preadapt the parasite for additional stress in the host and may be involved in the formation of sporozoites.

Eimeria necatrix virus: intracellular localisation of viral particles and proteins

The presence of the Eimeria necatrix virus was investigated in the following life cycle stages: sporocysts, sporozoites, merozoites, and macrogametes. Electron microscopy revealed virus-like particles (VLPs) in sporozoites, which were purified from sporozoite extracts and used to raise polyclonal antibodies. Viral proteins were identified as RNA polymerase (95 kDa) and the major capsid protein (80 kDa). Polyclonal antibody was used to detect the intracellular localisation of VLPs and proteins. Immunoelectron microscopy and immunohistochemistry identified a viral protein of 95 kDa in all the E. necatrix stages studied, whereas the 80 kDa protein was found only in sporocysts and sporozoites. In addition, no VLPs were found in sporocysts. These results indicate that the synthesis of viral capsid proteins takes place during the early events of sporulation, and is then packaged into novel viruses during the late events. No VLPs were seen and no capsid proteins were found in the merozoites and macrogametes, whereas the 95 kDa RNA polymerase was present in both these stages. In addition, no VLPs or proteins were detected in chicken tissues.

A method for the sequential study of eimerian chromosomes by light and electron microscopy

In the present study, the authors describe a simple method to isolate chromosomes from eimerian oocysts and to submit them to sequential study by light and electron microscopy. This method includes a reliable and reproducible technique for transferring eimerian chromosomes from slides to grid that fulfills the essential requirements for generalized use in cytogenetics. In addition, this method overcomes the difficulty of the resistance of protozoan oocysts to disruption and permits the release of intact meiotic chromosomes. The observation by the authors of synaptonemal complexes in meiotic chromosomes of different Eimeria species by applying the above-mentioned method to oocysts revealed its importance to future applications.

Field trial on the therapeutic efficacy of paromomycin on natural Cryptosporidium parvum infections in lambs

The objective of this study was to evaluate the therapeutic efficacy of paromomycin against cryptosporidiosis in naturally infected lambs under field conditions. The 36 cross-bred neonatal lambs, 3-10 days old, were used. On the first day that lambs showed diarrhea (Day 1) they were randomly divided into three groups. The infected control group (14 lambs) remained unmedicated whereas the two other groups were orally medicated with paromomycin solution (Humatin((R)), Parke Davis, France): 12 lambs (Group A) at 100mg/kg per day for three consecutive days (Days 1-3) and 10 lambs (Group B) at 200mg/kg per day for two days (Days 1 and 2). Drug efficacy was assessed by evaluating the presence of diarrhea, oocyst shedding and weight gains from Days 1 to 23. The results show the efficacy of paromomycin in reducing both cryptosporidial oocyst output and severity of clinical signs. On Day 4, all unmedicated lambs remained infected and excreted large numbers of cryptosporidial oocysts (mean score: 2.5) whereas oocyst output had stopped in most medicated lambs (>60%) and low numbers of oocysts were excreted in the remaining lambs (mean score: 0.45 in Group A and 1 in Group B). Mean oocyst excretion was significantly reduced in medicated lambs from Days 2 to 5 (P<0.05). Treatment also reduced, but not completely prevented, clinical symptoms although diarrhea stopped in most medicated lambs just after drug withdrawal. The mean weight gains of Group A lambs were higher than that of unmedicated lambs throughout the study and statistically significant differences were found from Days 1 to 11 (1.99+/-0.81 versus 1.47+/-0.53) (P<0.05). By contrast, the growth rate of Group B lambs from Days 11 to 23 was impaired when compared with the two other groups (P<0.05) although no significant differences were found at the end of the study (Days 1-23).

Immunohistochemical study of S100-like protein in Eimeria brunetti and Eimeria acervulina

We have investigated the expression of a calcium-binding protein, the S100 protein, in Eimeria brunetti and Eimeria acervulina stages. For this purpose, paraffin sections of distal ileum and bursa of Fabricius or duodenum from experimentally infected chickens were treated with anti-alpha-S100 (anti-alpha subunit of S100 protein) and anti-beta-S100 (anti-beta subunit of S100 protein) monoclonal antibodies and anti-S100 whole molecule polyclonal antibody. The avidin-biotin peroxidase method was used to demonstrate immunoreactivity. In the ileum, our results reveal a positive immunoreaction for the beta subunit and S100 whole molecule within the macrogametes of E. brunetti, whereas they were devoid of immunostaining after treatment of the paraffin sections with the anti-alpha-S100 antiserum. Schizonts and oocysts of E. brunetti and all the E. acervulina stages gave a negative reaction after treatment with any of the three antiserum used in the study. This result indicated that the S100 protein molecules within these stages were not recognized by the antibodies, suggesting that these molecules are different from those identified in macrogametes of E. brunetti. By contrast, in the epithelial cells, lining the lumen of the bursa of Fabricius, macrogametes of E. brunetti were stained by the three antibodies used. These results may indicate the existence of metabolic adaptations that enable the parasite to invade tissue sites different from those where the parasite usually develops.

Expression and localization of an S100 protein-like molecule in Eimeria tenella

We investigated the expression of a calcium-binding protein, the S100 protein, in Eimeria tenella. Cecal paraffin sections from experimentally infected chickens were treated with anti-alpha-S100 (anti-alpha subunit of S100 protein) and anti-beta-S100 (anti-beta subunit of S100 protein) monoclonal antibodies and anti-S100 whole molecule polyclonal antibody. The avidin-biotin peroxidase method was used for immunocytochemical staining. Our results demonstrated a positive immunoreaction within the schizonts, macrogametes, and oocysts. These stages were all beta subunit and S100 whole-molecule positive. Immunoblot studies of the total proteins of E. tenella merozoites and sporozoites of the original strain and 2 precocious lines have demonstrated that precocious attenuation produced different S100 protein isotypes.

Immunohistochemical identification of the cells parasitized by second-generation schizonts of Eimeria tenella

Conflicting reports exist in the literature concerning the type of cells within the lamina propria of the ceca that harbor second-generation schizonts of Eimeria tenella. Most of the previous studies concerning these cells have been performed using routine light or electron microscopy. Consequently, difficulties are evident in precise definition of the type of these cells using normal morphological criteria, since growth of the schizonts of E. tenella alters the morphology of the parasitized cell, making it difficult to recognize the cell type. This has led us to investigate the possibility of precisely identifying the subepithelial cells that are parasitized by mature schizonts. For this purpose we used cytoskeletal markers, namely, keratin and vimentin intermediate filaments, which allow the discrimination between epithelial and mesenchymal cells. Localization of keratin and vimentin on frozen cecal sections was studied immunohistochemically using specific monoclonal antibodies. Sites of antigenicity were detected by the avidin-biotin complex (ABC) immunoperoxidase technique and visualized by the deposition of diaminobenzidine. The identity of the cells was confirmed by the immunodetection of keratin intermediate filaments in the cytoplasm of the cells. Immunoreactivity for vimentin was absent in the parasitized cells. Therefore, we conclude that the development of second-generation schizonts of E. tenella takes place in epithelial cells within the lamina propria, which are presumably crypt epithelial cells that leave the crypts and enter the lamina propria after infection by first-generation merozoites.

[Comparative study of an expert system application in the prescription of medications]

BACKGROUND

The aim of this study was to evaluate the impact of a expert drug system implementation on the drug prescription habits and on drug cost in an university hospital.

MATERIAL AND METHODS

During a 3 months period, the drug prescriptions to patients admitted to the Internal medicine, lung, gastroenterology and hepatology units, have been evaluated through the expert drug system (Medisource). This expert drug system functions in according to patients characteristics such as age, weight, height, sex, renal function and liver function. It recommends the correct dose, detects interactions and adverse effects and makes suggestions in pregnancy and lactation. It also offers alternative drugs with their cost. During the study period physicians were unaware of the investigation being performed.

RESULTS

836 patients (63.9 +/- 16.5 years) with an average hospital stay length of 11.6 +/- 6.7 days were studied. The most common diagnoses were: lung obstructive chronic disease, cirrhosis, gastrointestinal hemorrhage and cancer. The total amount of drug prescribed was 6,308. The expert system detected 458 overdosages and 33 underdosages, mainly in antibiotics and antiulcer drugs, and 1,722 interactions. The drug costs reduction that could be obtained following the expert system recommendations was 4.5% in antibiotic drugs and 23% in antiulcer drugs.

CONCLUSION

The frequency of drug overdosage and underdosage in patients admitted in an university hospital is relatively high. The expert systems available for drug decisions could solve this problem.

Identification of avian dendritic cells in the spleen using a monoclonal antibody specific for chicken follicular dendritic cells

BACKGROUND

In the chicken, circulating antigens enter the splenic white pulp via the Schweigger-Seidel sheaths (ellipsoids), where they are bound by cells, the ellipsoid associated cells (EAC), which are located on the periphery of the ellipsoid. There is an increasing body of evidence that these antigen-binding cells move through the PALS, to be finally located within the germinal centers, where these antigen-transporting EAC function as follicular dendritic cells (FDC). The aim of the current study was to further study the relationship between the EAC, the FDC, and the antigen-bearing EAC which migrate through the splenic white pulp.

METHODS

In order to identify the splenic FDC and their presumed migrating EAC precursors in the chicken, we used a monoclonal antibody produced against chicken FDC and an antiserum anti-S-100 protein which identifies chicken dendritic cells in lymphoid organs.

RESULTS

Cells reacting with the 74.3 monoclonal antibody, which identifies FDC, were found within the germinal center, around the penicilliform capillary, in the periellipsoidal white pulp, and in the periarteriolar lymphatic sheaths (PALS). S-100+ cells were found in these same locations.

CONCLUSIONS

A comparison between the staining patterns obtained with both antibodies strongly suggested that the intrasplenic distribution of 74.3+ cells was identical with that of FDC, EAC, and antigen-binding EAC migrating in the PALS. Therefore, the 74.3 monoclonal antibody identified not only FDC but also the splenic precursor cells of FDC, in accordance with the hypothesis of the migration of the EAC through the white pulp. S-100+ cells were more numerous than 74.3+ cells, which is in accordance with the fact that S-100 protein antibody stains both FDC and interdigitating dendritic cells (ID). This has allowed us to suggest that 74.3- EAC may represent precursors of ID. The current findings reinforce previous investigations, which provided evidence supporting the migration of EAC through the PALS and further supported the hypothesis which considers EAC precursors of FDC.

Prevalence of intestinal parasites, including Cryptosporidium parvum, in dogs in Zaragoza city, Spain

Faecal samples from 81 dogs aged between 2 months and 13 years were collected in the small animal clinic (37 domestic dogs) and the animal shelter (44 stray dogs) located in the Faculty of Veterinary Sciences in Zaragoza city (northeast Spain) and screened for the presence of Cryptosporidium oocysts. Faeces were concentrated by the formalin-ethyl acetate method and smears of the sediment were stained by using the modified Ziehl-Neelsen technique. Cryptosporidium parvum oocysts were detected in six dogs (7.4%) aged from 2 months to 6 years. Infection was detected in both domestic (three) and stray (three) dogs and all of them excreted few oocysts (0-1 oocyst per 20 x field). No statistically significant differences in prevalence occurred between dogs younger than 6 months (11.8%) and the older dogs (6.2%). Prevalences were not significantly different between domestic (8.1%) and stray dogs (6.8%). Diarrhoea was recorded in three of the positive dogs (50%), although additional enteric parasites such as oocysts of Isospora spp. were also detected in their faeces. Nevertheless, prevalence was significantly higher in diarrhoeic (30%) versus non-diarrhoeic (4.2%) dogs (P < 0.05). Cryptosporidium was one of the parasites most frequently detected in the dogs surveyed.

Prevalence of Cryptosporidium infections in pigs in Aragón (northeastern Spain)

Faecal samples from 620 pigs randomly selected from 27 farms throughout Aragón were examined to determine the prevalence of Cryptosporidium infections. Detection of oocysts was performed using the ethyl-acetate stool concentration method and the modified Ziehl-Neelsen technique. Cryptosporidium parvum oocysts were identified in 136 (21.9%) pigs from 21 (77.8%) farms. Infected animals ranged from 1 to 6 months old and oocysts were not detected in suckling piglets or adults. Infection rates were significantly higher in weaned, 1-2 month old piglets (59.2%) than in fattening, 2-6 month old pigs (34.3%) (P < 0.001). Cryptosporidial infections were asymptomatic in most of the pigs (90.4%) and usually of low intensity, since 92.6% of the infected pigs excreted few oocysts (0-1 oocysts per field at x 200 magnifications). Although 24.1% of weaned and 5.6% of fattening pigs infected by C. parvum had diarrhoea, it was not found to be statistically associated with infection. In fact, infection rates were higher in non-diarrhoeic than in diarrhoeic pigs, in both weaned (64.7% and 46.7%, respectively) and fattening pigs (34.3% and 33.3%).

Comparison of an acid-fast stain and a monoclonal antibody-based immunofluorescence reagent for the detection of Cryptosporidium oocysts in faecal specimens from cattle and pigs

A commercially available direct immunofluorescence (IF) assay with monoclonal antibodies (Monofluo Kit Cryptosporidium, Diagnostics Pasteur, France) was compared with the modified Ziehl-Neelsen (MZN) acid-fast technique for the detection of Cryptosporidium oocysts in faecal samples from cattle and pigs. Stool specimens individually collected from 108 bovines and 90 pigs were examined in a blind test. The results of the two procedures corresponded (both positive or negative) in 102 (94.4%) cattle samples and 80 (88.9%) pig faecal samples. However, the remaining six (5.5%) cattle specimens and 10 (11.1%) pig stool samples, all of them harboring few oocysts (0-1 oocysts per 20 x field), were negative by MZN and positive by IF. False-negative results of the acid-fast stain occurred in suckling (17.2% of discrepant results) and weaned calves (2.9%) as well as weaned piglets (43.7%) and fattening pigs (10%). Stool specimens from the remaining age groups were negative by both techniques. The MacNemar's chi-square test showed that differences between both methods were statistically significant (P < 0.05). Compared with immunofluorescence procedure, the sensitivity of MZN technique in samples from cattle and pigs was 79.3% and 67.7% and the negative predictive value was 92.9% and 85.5% respectively. The specificity and positive predictive values of the acid-fast stain were 100% in both animal species. It is concluded that the monoclonal antibody-based immunofluorescence reagent evaluated is more efficient that the MZN technique, especially for detecting a low number of Cryptosporidium oocysts, in faecal specimens from both cattle and pigs.

Prevalence of Cryptosporidium and Giardia infections in cattle in Aragón (northeastern Spain)

Faecal samples from 554 bovines randomly selected at 30 farms in Aragón were examined to investigate the prevalence of Cryptosporidium and Giardia infections. C. parvum oocysts were identified by using the Ziehl-Neelsen modified technique in 109 (19.7%) bovines ranging from 3 days old to adults. Positive animals were found in 19 (63.3%) farms. As much as 44.4% of calves aged 3-4 days were infected, but infection rates peaked at 6-15 days of age (76.7%). Nevertheless, prevalence was also high in weanling calves aged 1.5-4 months (14%), fattening calves and heifers 4-24 months old (7.7%) and adults (17.8%). Diarrhoea was recorded in 78.6% of suckling and 29.4% of weanling calves infected by C. parvum, but it was only found to be statistically associated with infection in suckling calves (P < 0.01). All calves shedding moderate or many oocysts had diarrhoea, whereas asymptomatic infection was always correlated with few oocysts in faeces. Cryptosporidial infections were always asymptomatic in bovines older than 4 months. Giardia cysts were identified in 65 bovines (11.7%) from 16 (53.3%) of the farms surveyed. Infection rates were significantly higher in suckling (14.1%) and weanling calves (38%) than in bovines older than 4 months (2.2%) (P < 0.001). Diarrhoea was recorded in 45.5% of suckling and 10.9% of weanling calves infected by Giardia, but it was not found to be statistically associated with infection. In fact, infection rates were higher in non-diarrhoeic than in diarrhoeic calves.

Comparison of oocyst shedding and the serum immune response to Cryptosporidium parvum in cattle and pigs

A comparison was made between oocyst shedding and the presence of specific serum IgG antibodies to Cryptosporidium parvum in 108 bovines and 90 pigs. Oocysts were detected by a commercial immunofluorescence assay in feces from 26.8% of bovines and 34.4% of pigs, whereas positive titers as determined by an indirect fluorescent antibody method were found in sera from 12.9% and 48.9% of the respective animals. Infection was significantly most frequent in suckling calves (82.7%) and weaned piglets (87.5%). By contrast, the numbers of seropositives were highest in weaned calves (17.1%) and fattening pigs (76.6%). The results of coprological and serological analysis corresponded in 65.7% of bovines and 56.7% of pigs. When used to diagnose the shedding of cryptosporidial oocysts, the detection of specific IgG antibodies had a sensitivity ranging from 10.3% (cattle) to 58.1% (pigs) and a specificity of 86.1% (cattle) and 55.9% (pigs).

Cytochemical study of the germinal membrane of the Echinococcus granulosus cyst

The present cytochemical study was undertaken to provide more information on the localization of enzymatic and glycoconjugates in the germinal membrane of the Echinococcus granulosus cyst. The distinctive distribution of binding sites for two lectins (peanut agglutinin and Dilochos biflorus agglutinin) in the germinal membrane are described. An investigation is made of the distribution and specific activity of adenosine triphosphatase, alkaline phosphatase and acid phosphatase. The results suggest that cells located in the deeper layer of the germinal membrane are intrinsic in the cellular differentiation process. The dissimilarities detected in both the enzymatic activity and the lectin-binding receptors could be associated with metacestode development or degeneration.

Antigen-binding cells in the cecal tonsil and Peyer's patches of the chicken after bovine serum albumin administration

It has been previously reported in the chicken that the ellipsoid-associated cells (EAC), which are considered to be a type of splenic dendritic cell, migrate from the spleen into the blood after binding antigen on their surface. In the current study we traced the localization of these cells within two peripheral lymphoid organs, the cecal tonsil (CT) and the Peyer's patches (PP). The migration of the cells was followed by light microscopy using bovine serum albumin bound to biotin and conjugated to gold particles as a histochemically identifiable antigen detected as peroxidase reaction. The observations showed that the EAC after entering the circulating blood migrated into the lymphoid tissue of the CT and the PP. As a consequence, the antigen-binding cells were found in the diffuse lymphoid tissue and the germinal centers in both lymphoid organs. In the former location they were seen 24 h after the second antigen administration and in the germinal centers on Day 3. In addition, antigen-binding cells started to be observed in the lymphoid tissue at the same time as T and B cells were found to proliferate by using 5-bromo-2'-deoxyuridine. Based upon these findings, we suggested that the EAC have a role as antigen-transporting cells from the spleen to the CT and the PP via the blood stream. Furthermore, our results provided evidence that after the antigen-transporting EAC entered the above-mentioned organs, these cells behaved as antigen-presenting cells in both the T- and B-dependent areas.(ABSTRACT TRUNCATED AT 250 WORDS)

Localization of splenic cells with antigen-transporting capability in the chicken

BACKGROUND

The objective of the present study is to investigate the migration pattern of the splenic dendritic cell of the chicken named the ellipsoid-associated cell (EAC) from the site of initial location at the periphery of the ellipsoid to the splenic T- and B-dependent areas.

METHODS

Bovine serum albumin bound to biotin and conjugated to gold particles was used as a histochemically identifiable antigen detected as a peroxidase reaction. The antigen was intravenously injected, and subsequently its pattern of distribution in a time sequence and within the tissue was examined at the light and electron microscopy levels. In addition, an hour prior to sacrifice, the chickens received a single injection of the thymidine analogue 5-bromo-2'-deoxyuridine, in order to quantify the number of DNA synthesizing cells and to establish a relationship between the migrating EAC and the rate of mitosis in the white pulp.

RESULTS

The observations showed that between 12 hours and 3 days after the second antigen administration the labeled EAC, which was first located around the ellipsoid, progressively reached further areas with time towards the periarteriolar lymphoid sheaths, where newly formed germinal centers appeared. Furthermore, the rate of cell proliferation within the white pulp was associated with the arrival of the antigen-transporting EAC.

CONCLUSIONS

The results suggest that migrating EAC have a role as both antigen-transporting cell and antigen-presenting cell in the T- and B-dependent areas, as a result of which migrating EAC is transiently found in periellipsoidal white pulp, then periarteriolar lymphoid sheaths, and finally germinal centers, where it may function as an interdigitating cell or as a follicular dendritic cell, depending on its location. Thus, we conclude that the EACs are precursors of both interdigitating and follicular dendritic cells.

Characterization of distal lymphoid nodules in the chicken caecum

In this report, we describe lymphoid nodules consistently found in the distal region of each chicken caecum at approximately 3 cm from the ileo-cecal junction. These structures were studied by light microscopy both in normal and Eimeria tenella-infected chickens. They were observed with the naked eye in infected birds but not in normal chickens. In these latter the region of the caecal lamina propria corresponding to that in which the lymphoid aggregates were visible revealed a light infiltration by diffuse lymphoid tissue as well as a few germinal centers. The distal lymphoid nodules were studied using a panel of monoclonal antibodies which are specific for chicken Ig-containing cells, macrophages, Ia-like positive cells, and interdigitating cells, as well as a policlonal antiserum reactive with S-100 protein to stain both interdigitating cells and follicular dendritic cells. The immunohistochemical study demonstrated the resemblance of these aggregates to the caecal tonsils, suggesting that they represent specialized mucosa-associated lymphoid tissue that respond to antigens in the caecal lumen, their function being to enhance the mucosal defense provided by the caecal tonsils against antigens in the lumen of the caeca.

Immune complex-mediated glomerulopathy in Barbus graellsi infected with Myxobolus spp

Membranous glomerulonephritis caused in Barbus graellsi by myxosporidian infections have been studied by electron microscopy and immunoelectron microscopy techniques. This study indicates that Myxosporidian infection produces a chronic severe aggression. Spores reach the spleen, the kidney and the liver, where they are trapped and phagocyted by Melano Macrophage Centres. Consequently, the commencement of a immunological response to myxosporidian is evident. Our results show the presence of immunodeposits in the basement membrane of the glomeruli, suggesting that they might initiate glomerulonephritis. The lesion was markedly similar to immune complex-mediated glomerulonephritis disease in higher vertebrates.

Follicular dendritic cell activation in the harderian gland of the chicken

The avian follicular dendritic cell changes that occur in the germinal center of the Harderian gland during the course of the immune response were studied by electron microscopy and the immunoperoxidase method was employed for the detection of S-100 protein. The chickens were injected twice with Salmonella O Antigen into the nictitating membrane at 9-day intervals. The follicular dendritic cells exhibited filiform processes at between 24 and 96 h after the second antigen administration. Filiform dendrites tended to convolute near the cell body. Therefore, it can be assumed that these processes make it more difficult for macrophages and B cells to make contact with the immune complexes retained by the follicular dendritic cells and, as a consequence, the period of antigen handling by these cells increases. Evidence is provided that the dendritic processes are closely associated with both lymphoblasts and lymphocytes. Furthermore, S-100 protein was found in the abovementioned cells exclusively and only in those cells where filiform dendrites were observed. These findings suggest that, during a secondary immune response, the follicular dendritic cell undergoes a functional activation which involves morphological changes and the phenotypic expression of the S-100 protein. This activation is hypothesized to be similar to that described for follicular dendritic cells in mammals after fixing immune complex.

Local immune response in the chicken Harderian gland to antigen given by different ocular routes

The effectiveness of three ocular routes of antigen administration to produce a local immune response in the Harderian gland was studied. The routes were by eyedrop, injection into the ocular conjunctiva and injection into the nictitating membrane. The antigen was observed in the cytoplasm of macrophages located within the lymphoid tissue only after the injection into the nictitating membrane. The numbers of germinal centres and plaque forming cells found in the gland after injection into the nictitating membrane was higher than the numbers observed following the other two ocular applications. These findings indicate that the injection of the antigen into the nictitating membrane is the most effective ocular route for producing a local immune response in the Harderian gland.

Immunoglobulin classes synthesised by the chicken Harderian gland after local immunisation

The immunoglobulin (Ig) levels in tears and sera were compared after antigen administration (salmonella O antigen) by eyedrop and injection into the nictitating membrane, to determine the Ig classes synthesised by the plasma cells in the chicken Harderian gland. Samples of tears and sera were collected from immunised and control birds between 24 hours and 24 days after the antigen or sterile saline was administered. Samples were assayed for IgA, IgG and IgM concentrations using radial immunodiffusion. It is suggested that most of the IgG found in tears after local immunisation has an extraglandular origin.

Myofibroblasts and myoepithelial cells in the chicken harderian gland

An electron microscopic study of the myoepithelial cells in the chicken Harderian gland provides evidence that these cells can be transformed into myofibroblasts. After the application of a Brucella ovis suspension in sterile saline onto the eyeball, every 5 minutes for half an hour, myoepithelial cells gradually develop over a 90-minute period the characteristic features of myofibroblasts: bundles of intracytoplasmic microfilament; abundant rough endoplasmic reticulum; prominent Golgi complex; and surface membrane differentiations, that provide attachment to neighbouring epithelial cells. No typical desmosomes are observed. Besides, the intercellular space between epithelial cells and myofibroblasts increases and the basement membrane adjacent to myofibroblasts disappears. Hypoxia is hypothesized to be involved in the transformation of myoepithelial cells into myofibroblasts.

Granulopoiesis in the pineal gland of chickens

Foci of differentiating heterophilic granulocytes in the pineal gland were studied by light and electron microscopy in chickens, from hatching until 56 weeks of age. Foci of granulopoiesis could be seen in the first 24 hours after hatching. Thereafter, their number and cellular density increased, becoming highest at 2 weeks. From then on, numbers decreased progressively until foci disappeared at 18 weeks. Granulopoietic cells established local associations with fibroblast-like cells. Mature granulocytes reached the bloodstream by the 2 mechanisms described for hematopoietic cells in the bone marrow, either passing between lining cells or through the cytoplasm of lining cells.