Nerve fibres in the parathyroid gland of the golden hamster (Mesocricetus auratus): immunohistochemical and ultrastructural investigations

We investigated the morphology and the distribution of the nerve fibres in golden hamster (Mesocricetus auratus) parathyroid glands using antibodies to calcitonin gene-related peptide (CGRP) and substance P, and electron microscopy. CGRP-immunoreactive nerve fibres were densely distributed in the interstitial tissues and the capsules of the hamster parathyroid glands. Some nerve fibres were detected in close proximity of the parathyroid chief cells. The distribution pattern for substance P-immunoreactive nerve fibres was roughly the same as for CGRP-immunoreactive fibres. Ultrastructurally, we found numerous nerve fibres joining the blood vessels. Axon bundles were located adjacent to the smooth muscle cells of the arterioles. The axons formed structurally specialized neuromuscular junctions with the vascular smooth muscle cells. Some axons were in close vicinity to the parathyroid chief cells. These findings indicate that the hamster parathyroid gland contain CGRP and substance P, which may regulate the blood flow and the secretory activity of the gland.

A Case of Anaplastic Meningioma in a Dog

A tumor sized in 2.0x2.0x2.5 cm developed in the cerebellum of a female Beagle was pathologically investigated. Histopathologically, the tumor grew by compression and partially by infiltration into the adjacent cerebellar parenchyma. There were a large number of necrotic lesions and proliferation of collagen fibers. The tumor cells had oval nucleus showing cellular atypia and a high mitotic index. The tumor cells were reacted with vimentin antibody on immunostain. Electron microscopic examination revealed the tumor cells interdigitated with cytoplasmic processus where the desmosomes developed on cell junction. This tumor was diagnosed as anaplastic meningioma, which is rarely observed in dogs.

Methodology in diagnostic virology

Selection of proper assays and appropriate interpretation of results can be a challenge to the veterinary clinician. Assays vary in methodology, sensitivity, and specificity. These assays can be invaluable in attaining the correct diagnosis, but a clear understanding of the assay and the results is essential. To this end, communication with the laboratory personnel is crucial. Optimal sample selection, shipping recommendations, assay selection, and interpretation should be discussed with the laboratory staff.

RANAVIRUS-ASSOCIATED MORBIDITY AND MORTALITY IN A GROUP OF CAPTIVE EASTERN BOX TURTLES (TERRAPENE CAROLINA CAROLINA)

Seven captive eastern box turtles (Terrapene carolina carolina) from a large collection of North American chelonians in North Carolina became acutely ill in the fall of 2002. Five of the turtles died. Clinical signs included cutaneous abscessation, oral ulceration or abscessation (or both), respiratory distress, anorexia, and lethargy. The predominant postmortem lesion was fibrinoid vasculitis of various organs, including skin, mucous membranes, lungs, and liver. No inclusion bodies were detected by histopathology or electron microscopy of formalin-fixed tissue. An iridovirus was isolated from tissues obtained postmortem from two of the box turtles that died. The virus was characterized by electron microscopy, polymerase chain reaction, and sequence analysis of a portion of the major capsid protein as a member of the genus Ranavirus.

An ELISA optimized for porcine epidemic diarrhoea virus detection in faeces

Monoclonal antibodies to porcine epidemic diarrhoea virus (PEDV) membrane protein M were prepared and used for the comparative assessment of three blocking ELISA variants to detect PEDV. The competitive blocking ELISA (CB-ELISA) format showed the highest sensitivity, allowing detection of 10^2.5 plaque-forming units of PEDV/ml in culture medium. Its specificity was verified by inclusion of control samples containing transmissible gastroenteritis virus (TGEV) and rotavirus A in each analysis. Eighty porcine field samples of faeces obtained from 38 herds affected with diarrhoea were examined, and PEDV was found in 15 (19%) samples from 6 (16%) herds. The suitability of the CB-ELISA for the screening herds in epizootiologic situations is discussed.

An epidemic of caprine arthritis encephalitis in Japan: isolation of the virus

A disease characterized by arthritis of carpal joints and occasionally by pneumonia was seen among goats on a farm in Nagano prefecture of Japan in the summer of 2002. Serological investigation was done on 30 goats, that is one group on the farm by agar gel immunodiffusion tests using maedi-visna virus as the antigen, and 19 goats were positive. The caprine arthritis encephalitis virus genome was detected in peripheral blood leukocytes from several antibody-positive goats. Two goats among them were necropsied and used for pathological tests and virus isolation. The isolated virus was serially propagated in fetal lamb lung cell cultures. Goats inoculated with the culture fluid became antibody positive. These results suggested that a CAEV-infected goat had been introduced accidentally to the farm and that subclinical infection occurred among the flock.

Invasion of chicken embryo fibroblast cells by avian Pasteurella multocida

Invasion of chicken embryo fibroblast (CEF) cells by the virulent encapsulated Pasteurella multocida strains P-1059 (serovar A:3) and X-73 (serovar A:1) and an avirulent noncapsulated derivative P-1059B (serovar -:3) was investigated. The number of intracellular bacteria increased for all the strains after 2, 4 and 6 h post-inoculation to CEF cells. By 6 h post-inoculation, the number of invaded bacteria of encapsulated strains was significantly higher than noncapsulated strain and reached 150- and 112-fold for strains P-1059 and X-73, respectively, while it was 9-fold for strain P-1059B as compared to the number of invaded bacteria recovered after 2 h post-inoculation. Electron microscopy of invasion by encapsulated strains showed that the bacteria were adhering to CEF cells membrane after 1 h of inoculation. By 4-h, one or two bacteria were detected within membrane-bound vacuoles of the intracellular space. The number of intracellular bacteria markedly increased at 14 h post-inoculation. Invasion of all strains was inhibited significantly when the monolayers were treated with periodic acid (P<0.001) or trypsin (P<0.05). The treatment of bacteria with hyaluronidase did not affect invasion. The present results indicate that avian P. multocida capsular type A strains are invasive and that the receptor on CEF cell surface might be glycoprotein.

A microsporidian parasite of the genus Spraguea in the nervous tissues of the Japanese anglerfish Lophius litulon

In the present study, a high percentage of Japanese anglerfish, Lophius litulon (Jordan, 1902), contained a microsporidian infection of the nervous tissues. Xenomas were removed and prepared for standard wax histology and transmission electron microscopy (TEM). DNA extractions were performed on parasite spores and used in PCR and sequencing reactions. Fresh spores measured 3.4 x 1.8 microm and were uniform in size with no dimorphism observed. TEM confirmed that only a single developmental cycle and a single spore form were present. Small subunit (SSU) rDNA sequences were >99.5% similar to those of Spraguea lophii (Doflein, 1898) and Glugea americanus (Takvorian et Cali, 1986) from the European and American Lophius spp. respectively. The microsporidian from the nervous tissue of L. litulon undoubtedly belongs in the genus Spraguea Sprague et Vivra, 1976 and the authors suggest a revision to the generic description of Spraguea to include monomorphic forms and the transfer of Glugea americanus to Spraguea americana comb. n. Since no major differences in ultrastructure or SSU rDNA sequence data exist between Spraguea americana and the microsporidian from the Japanese anglerfish, they evidently belong to the same species. This report of Spraguea americana is the first report of a Spraguea species from L. litulon and indeed from the Pacific water mass.

Proliferative renal myxosporidiosis in spawning coho salmon (Oncorhynchus kisutch) in British Columbia and Washington

An unidentified myxosporean parasite (CKX) is described from the kidney of approximately 80% of spawning coho salmon Oncorhynchus kisutch (Walbaum) in British Columbia, Canada and Washington, United States of America. Morphological features were described using light and electron microscopy. Sequencing of polymerase chain reaction (PCR) amplified 18S ribosomal RNA gene and in situ hybridisation were used to further characterise CKX. The parasite occurred with a focal distribution within tubule epithelial cells, the tubule lumen and the interstitium as primary cells containing from one to at least 16 secondary cells. Luminal stages were degenerate and sporogony was not observed. In situ hybridisation using a digoxygenin-labelled DNA probe confirmed CKX to be the source of DNA used in PCR analyses. CKX 18S rDNA sequences were most similar (97%) to those of Sphaerospora oncorhynchi. Phylogenetic analysis revealed similarities among the 18S rDNA sequences of CKX, S. oncorhynchi and Myxidium lieberkuehni. CKX is hypothesised to be the abortive extrasporogonic development of a Sphaerospora sp. or Myxidium sp. occurring in immune-incompetent spawning and senescent salmon.

Characterisation of attaching-effacing Escherichia coli isolated from animals at slaughter in England and Wales

Escherichia coli isolates were recovered from faecal samples taken from cattle, sheep and pigs at slaughter in England and Wales. Isolates (n = 1227) selected at random from this collection were each hybridised in colony dot-blot experiments with an eae gene probe that presumptively identified attaching-effacing E. coli (AEEC). Of the 99 (8.1%) eae positive isolates 72 were of ovine origin, 24 were of bovine origin and three of porcine origin. None were typed as O157:H7 whereas 78 were assigned to 23 serogroups and 21 were untypable. The most frequently isolated eae positive serogroups were O156 (10), O26 (8), O103 (8), O108 (7) O56 (6) and O168 (6) of which serogroups O103 and O156 only were recovered from all three animal species. In tissue culture adherence assays, 36 representatives of eae positive isolates of all serogroups and host of origin tested induced intimate attachment with varying degrees of actin accumulation and pedestal formation in the HEp-2 cells. The identity of the eae type for these 36 was determined by specific PCR and the most prevalent intimin types were eaebeta (15), eaegamma (12) and eae (4). Isolates were examined by PCR for the presence of other virulence determinants and five possessed stx1 but none possessed stx2. One O115 eae isolate possessed cnf1 and 2, hlyA, etpD and katP genes which is a novel combination of virulence determinants.

Distribution of the pores of epithelial basement membrane in the rat small intestine

The distribution and diameter of the pores of epithelial basement membrane in the intestinal villi and the lymph nodules of ileal Peyer's patches were investigated in the rat small intestine by scanning electron microscopy after the removal of the overlying epithelial cells with OsO(4) maceration. In the duodenum, jejunum and ileum, the pores were mainly distributed at the upper three fourths of the villi, but were scarce around the top of the villi. The diameter of some of the pores in the upper three fourths of the villi was larger than that of those in the lower portion. The protrusion of lymphocytes and the cytoplasmic processes of macrophages were also seen at the orifices of the pores. In ileal Peyer's patches, in contrast, pores were densely distributed in the lower one third of the follicle-associated epithelium (FAE) where M cells were mainly seen. Furthermore, these pores were larger than those found in the upper two thirds. Lymphocytes or cytoplasmic processes of macrophages were frequently seen in the lower one third of FAE. These results suggest that the pores at the basement membrane correspond to the passage of the immunocompetent cells which are in contact with M cells or villous columnar epithelial cells and that the abundance of pores is a sign of aggressive interaction between the particular epithelial cells and the immunocompetent cells at the upper three fourths of intestinal villi and the lower one third of FAE in the rat small intestine.

Distributive and phagocytic characteristics of hepatic macrophages in five cetaceans belonging to Delphinidae and Ziphiidae

Details of morphology and distribution of hepatic macrophages in cetaceans were investigated using the immunohistochemistry with an antibody (SRA-E5) generated against human macrophage scavenger receptor antigen. Liver samples were obtained from five species of cetaceans (Baird's beaked whales, short-finned pilot whales, Risso's dolphins, bottlenose dolphins, and pantropical spotted dolphins). Except for two species of whales, the number of SRA-E5-positive Kupffer cells was greatest in the perivenous zone (zone 3), followed by the mid-zonal (zone 2) and periportal (zone 1) zones; this distribution pattern was different from that in cattle examined here and previously reported rodents with the highest number in zone 1. The frequency of Kupffer cell in each of zones was significantly different among species, and interestingly, the total mean of the Kupffer cell number in three zones increased as the body-length of species was small. In cetaceans, Kupffer cells in zone 1 appeared larger and more stellate in shape, whereas those in zone 3 were smaller and rounder. All cetaceans but Baird's beaked whales had the black pigment-containing Kupffer cells, with the greatest number in zone 3, and macrophages with the similar pigments were also seen in the hepatic intermediate septa, indicating an active phagocytosis. Most of the black pigments were considered to be lipofuscin and such pigments were not seen in the bovine livers. These results indicate that cetacean hepatic macrophages show differences in the distribution and phagocytosis among hepatic lobular zones, or between cetacean species and terrestrial animals.

Lipoic acid is 10 times more toxic in cats than reported in humans, dogs or rats

The antioxidant lipoic acid (LA) is administered to humans and pets. We described acute toxicity and maximum tolerated dose (MTD) of LA in cats. In progression, 10 healthy adult male cats received orally 60 (high), 30 (low), or 0 mg LA/kg (control). Serum enzyme activities and concentrations of bile acids, ammonia, amino acids (AA), LA and dihydrolipoic acid (DHLA) were measured, and tissues examined microscopically. Significant clinical toxicity with changes in ammonia and AA concentrations occurred in all high-dose cats. Oral LA produced hepatocellular toxicity and MTD was < 30 mg/kg in cats.

Primary cardiac fibrosarcoma in a dog

A primary cardiac fibrosarcoma in the right atrium of a 6-year-old Chihuahua dog is described. At necropsy, there was a firm, whitish and spherical mass in the right atrium. Histopathologically, the mass had moderate cellularity composed of spindle-shaped cells with scattered multinucleated giant cells. The tumor cells were arranged in interwoven bundles and sheets in the collagenous stroma. No metastases were observed. Ultrastructurally, the tumor cells mainly consisted of fibroblasts. Multinucleated giant cells did not have any certain organelles that would indicate a higher order of differentiation. Primary cardiac sarcomas in dogs are extremely rare.

Effects of furazolidone pretreatment of Salmonella enteritidis PT4 at sub- and suprainhibitory concentrations on phagocytosis and intracellular survival in chicken macrophages

The antimicrobial effect of the nitrofuran derivative furazolidone at sub- and suprainhibitory concentrations on Salmonella enteritidis PT4 and the influence with regard to interaction with avian macrophages was investigated in this study. Phagocytosis of furazolidone-sensitive (FzS) S. enteritidis with chicken macrophages in the presence of furazolidone at concentrations of 1/8, 1/4, 1/2 and 8x MIC resulted in an increase in the rate of phagocytic killing of approximately 3-, 6-, 6.5- and 9-fold, respectively, with 1/2 and 8x MIC concentrations producing statistically significant (P<0.05) increases in phagocytosis. Treatment of the FzS Salmonella with furazolidone at concentrations of 4x and 10x MIC, for 15 min prior to phagocytosis, also significantly (P<0.005) increased phagocytic uptake when compared with untreated bacteria. The rate of phagocytosis monitored over 90 min was highest between 30 and 60 min with the furazolidone pretreated salmonella, compared with the delayed rate of the control between 60 and 90 min. Exposure of FzS and FzR strains with suprainhibitory concentrations of furazolidone at 4x, 8x and 10x MIC for 30 min prior to phagocytosis demonstrated an increase in bacterial killing. Exposure of strains to sub-inhibitory concentrations of furazolidone led to an increase in chemiluminescence during phagocytosis with macrophages, suggesting an increase in oxidative metabolism in the macrophages as a result of an increase in activation and phagocytosis. Pretreatment of the strains with suprainhibitory concentrations of furazolidone for 30 min prior to phagocytosis demonstrated a similar increase in oxidative metabolism in the macrophages. Measurement of the amount of 14C-furazolidone associated with chicken macrophages was determined over 20 h incubation. The level of radioactivity of 14C-furazolidone alone was used to estimate the amount of cell-associated nitrofuran when incubated with the macrophages by means of regression analysis. Incubation with concentrations of 16, 32 and 64 microg/ml for 20 h resulted in the cell association of >or=1 microg/ml of furazolidone, which is the concentration required for the agent to exhibit bactericidal activity on furazolidone-sensitive Salmonella strains. Furazolidone was able to reduce intracellular salmonella viability at all concentrations, but total killing was achieved only with concentrations of >or=8 microg/ml, which supports the results for furazolidone association with the macrophages. This substantiates that the bioactivity of the nitrofuran was not inhibited or diminished in the intracellular environment of the macrophage and that exposure of salmonella to nitrofurans enhances phagocytosis.

RENAL MYXOSPORIDIASIS IN ASIAN HORNED FROGS (MEGOPHRYS NASUTA)

Renal myxosporidiasis and associated lesions were seen in Asian horned frogs, Megaphrys nasuta, at the Detroit Zoological Institute and the Toledo Zoo. The organism was identified as Chloromyxum sp. on the basis of histopathology, cytology, and electron microscopy. Histologic changes in the kidneys included varying degrees of renal tubular dilation and necrosis, and mild to severe nonsuppurative tubulointerstitial nephritis associated with vegetative stages of the myxosporidian. This is the second known identification of Chloromyxum sp. in amphibian kidneys, and the first report of death attributed primarily to the parasite.

Effect of supplemental vitamin D3 concentration on concentrations of calcium, phosphorus, and magnesium relative to protein in subcellular components of the longissimus and the distribution of calcium within longissimus muscle of beef steers12

The effect of supplementing diets with various levels of vitamin D3 to provide 0, 0.5, 1, and 5 million IU/(steer x d) for 8 d before slaughter on the mineral content and localization of Ca in LM and muscle fragments was studied during the postmortem aging process. Twelve feedlot steers of three biological types were given access to the four levels of vitamin D for 8 d before slaughter. Differential centrifugation techniques were used to determine the concentrations of minerals relative to protein in different muscle fragments on d 3 and 21 postmortem. Electron microscopy visualization of bound Ca indicated that vitamin D3 mobilized Ca from the sarcoplasmic reticulum and transverse tubule system into the myofibrils. Bound Ca was concentrated near the Z-line at the A-band/I-band juncture within the sarcomere. Supplementing steers with 1 and 5 million IU/(steer x d) of vitamin D3 increased (P < 0.05) Ca, P, and Mg concentrations per unit of protein in the cytosol. Soluble cytosolic Ca concentrations were greater (P < 0.05) on d 21 than on d 3 postmortem only when steers were supplemented with 5 million IU/d. Concentrations of Ca, P, and Mg in isolated tissues were increased (P < 0.05) in nuclei and myofibrilar proteins by supplementing steers with 1 and 5 million IU/ (steer x d) of vitamin D3. All supplemental vitamin D3 treatments also increased (P < 0.001) Mg concentrations in the cytosol, regardless of aging treatment, and increased Mg concentrations (P < 0.04) within the mitochondria at d 3 postmortem. Thus, supplementation of feedlot steers with vitamin D3 at levels of 0.5 to 5 million IU/(steer x d) increased Ca concentrations within respiring muscle, resulting in increased bound tissue Ca concentrations. When the respiring muscle was converted to meat, the increased bound tissue Ca resulting from vitamin D3 treatment released Ca concentrations into the cytosol during aging (P < 0.05). Results of this study indicate that vitamin D3 supplementation increased total cytosolic Ca, P, and Mg concentrations in meat.

Hexamita meleagridis (Spironucleus meleagridis) Infection in Chukar Partridges Associated with High Mortality and Intracellular Trophozoites

An outbreak of infectious catarrhal enteritis, associated with the flagellated protozoan Spironucleus meleagridis (syn. Hexamita meleagridis), is reported from a commercial flock of chukar partridges in California. The disease affected birds between the ages of 4 and 6 wk and resulted in diarrhea, listlessness, depression, and high mortality. Concurrent infection with other intestinal pathogens, including Cryptosporidia, group E Salmonella, long-segmented filamentous microorganisms (LSFMOs), and Rotavirus-like virus particles, was found in some but not all affected birds. Dermatitis of the face, shanks, and feet, suggestive of B-complex vitamin deficiency, was present in most affected birds as well. Flagellated protozoan parasites could be found in the lumen of the duodenum and jejunum and in the intestinal crypts. In some cases the flagellates were wedged between epithelial cells or were located intracellularly within cells of the mucosal epithelium and the intestinal lamina propria.

Light and Transmission Electron Microscopy of Immature Camelus Dromedarius Oocyte

In order to provide a consistent system for laboratory production of embryos, the characteristics of immature camel oocyte must first be described. The objective of this study was to define ultrastructural features of immature camel oocyte. Ovaries were obtained from camels at a local abattoir, and then transported to the laboratory within 2 h. Camelus cumulus oocyte complexes (COCs) were aspirated from 2-6 mm follicles using a 22-gauge needle. Excellent and good quality COCs were selected and prepared for transmission electron microscopy study using a cavity slide. The fine structure of camel oocyte is morphologically similar to that of other mammalian oocytes. However, some minor differences exist between COC of camel and other mammalian species. Different size and shape of membrane-bound vesicles, lipid droplet, mitochondria and cortical granules were distributed throughout the ooplasm. Discrete or in association with endoplasmic reticulum, Golgi complexes were observed in the periphery of the oocytes. The majority of the oocytes were in the germinal vesicle stage.

Disseminated Toxoplasmosis in a Captive Ring-Tailed Lemur (Lemur catta)

A 3-yr-old secundiparous female ring-tailed lemur presented to the Auburn University Small Animal Clinic with signs of dyspnea, lethargy, and anorexia. The animal died before she could be examined, and a full necropsy was immediately performed. Provisional necropsy findings included moderate pneumonia and hepatopathy. Acute interstitial pneumonia and focal hepatocellular necrosis were confirmed histologically. Lung impression smears, histopathology, electron microscopy, immunohistochemistry, and tissue culture isolation resulted in a diagnosis of acute disseminated Toxoplasma gondii infection, which was confirmed by polymerase chain reaction. The isolate of T. gondii was avirulent for mice and was named AU Tgl and genetically is type II. The source of the infection remains unclear, but speculation suggests contaminated fruit or blackbirds (Passeriformes: Icteridae) acting as transport hosts for oocysts from nondomestic felids and feral cats on the property.

Cryptobia iubilans infection in juvenile discus

Four commercial producers of discus (Symphysodon aequifasciatus) were found to have fish infested with the flagellate Cryptobia iubilans. Affected fish had granulomatous gastritis, and many also had granulomatous disease of other organs. The parasite had to be differentiated from the related flagellates Spironucleus spp, which induce different lesions. Transmission electron microscopy was found to be useful in detecting and identifying the parasite. Morbidity and mortality rates in the various fish populations appeared to be linked to a number of variables, including water quality, presence of other parasites and bacteria, diet, species, size, and age of the fish, and optimization of husbandry appeared to be important in alleviating the severity of disease. Metronidazole was not effective for treatment of C iubilans, but bath treatments with dimetridazole (80 mg/L for 24 hours, repeated daily for 3 days) or 2-amino-5-nitrothiazol (10 mg/L for 24 hours, repeated daily for 3 days) may be useful in decreasing the prevalence of infestation.

Erysipelothrix septicemia in a little blue penguin (Eudyptula minor)

On June 25, 2002, aquarium veterinarians treated a 5-year-old, male little blue penguin (Eudyptula minor) that was acutely recumbent and dull, with inappetence of 24-hour duration. The penguin died within 10 minutes of presentation despite emergency resuscitation efforts. Gross pathologic findings consisted of pulmonary congestion and intestinal hemorrhage. Histopathologic findings included necrosis of tips of intestinal villi, increased numbers of mononuclear cells in pulmonary interstitium and hepatic sinusoids, and gram-positive bacteria in systemic microvasculature. Transmission electron microscopic examination revealed short gram-positive bacilli located in lumina of glomerular capillaries and in cytoplasm of mononuclear phagocytic cells in the lung and liver. Erysipelothrix rhusiopathiae was recovered from the lung, liver, and intestine by bacteriologic culture. Amplicons from polymerase chain reaction (PCR) tests using Erysipelothrix genus-specific primers and total genomic DNA extracted from formalin-fixed, paraffin-embedded tissue sections of lung and intestine demonstrated 99% nucleotide sequence identity with 16S small-subunit ribosomal DNA of E. rhusiopathiae and E. tonsillarum. The source of infection was speculated to be fish in the diet; however, repeated attempts to detect Erysipelothrix spp. from the mucous layer of food fish using bacteriologic culture and PCR were unsuccessful. This is the first report of erysipelas in a captive aquatic bird. Details of the isolation of E. rhusiopathiae and the application of molecular testing to identify Erysipelothrix DNA in formalin-fixed, paraffin-embedded tissue sections are given.

In vivo and in vitro colonization patterns of AIDA-I-positive Escherichia coli isolates from piglets with diarrhea

Transmission electron microscopy (TEM) was used to characterize the colonization patterns of 3 pathogenic Escherichia coli strains: PD58 and PD149 of the AIDA-I/STb/EAST1 pathotype, serogroup O: ND (not determined), and PD31 of the LT/STb/EAST1 pathotype, serogroup O149. These strains were isolated from diseased piglets and caused diarrhea in experimentally inoculated, newborn, colostrum-deprived pigs. In this study, intestinal tissues from newborn pigs experimentally infected with a high inoculum (20 ml containing 10(10) cfu) were harvested and examined for bacterial colonization using light microscopy. A nonaqueous perfluorocarbon fixation method was used to preserve the glycocalyx of the microvillus border in tissues collected for TEM. Transmission electron micrographs revealed that E. coli strain PD149 displayed long flexible fimbria-like structures that intimately attached the bacteria both to the microvillus border of the upper colon and to adjacent bacteria. In vitro, this strain demonstrated the localized adherence pattern to HEp-2 cells characteristic of enteroaggregative E. coli (EAggEC). Both PD58 and PD31 strains colonized the upper colon through the formation of a biofilm, also characteristic of EAggEC. Strains PD58 and PD31 adhered poorly to HEp-2 cells in vitro, although these demonstrated a colonization pattern suggestive of diffuse and aggregative adherence, respectively. These findings suggest that strains PD58 and PD149, expressing the AIDA-I, factor and strain PD31 represents hybrid pathotypes of diarrheagenic E. coli and that they probably cause diarrhea in piglets through differing mechanisms.

Trichinella papuae and Trichinella zimbabwensis induce infection in experimentally infected varans, caimans, pythons and turtles

The discovery of Trichinella zimbabwensis in farm crocodiles of Zimbabwe has opened up a new frontier in the epidemiology of the Trichinella genus. The objective of the present study was to investigate the infectivity of encapsulated species (T. spiralis, T. nativa, T. britovi, T. murrelli and T. nelsoni) and non-encapsulated species (T. pseudospiralis, T. papuae and T. zimbabwensis) in caimans (Caiman crocodilus), varans (Varanus exanthematicus), pythons (Python molurus bivittatus) and turtles (Pelomedusa subrufa) raised at their natural temperature range (26-32 degrees C). Mice and chickens were used as controls. At 6 days post-infection (p.i.), adult worms were detected in the small intestine of reptiles infected with T. papuae and T. zimbabwensis, of chickens infected with T. pseudospiralis and of mice infected with all encapsulated and non-encapsulated species. At 60 days p.i., T. papuae and T. zimbabwensis adult worms were collected from the intestine of varans and caimans and larvae from muscles of the four reptile species, T. pseudospiralis larvae from muscles of chickens, and larvae of all Trichinella species from mouse muscles. The highest reproductive capacity index of both T. papuae and T. zimbabwensis was observed in varans. The results show that T. papuae and T. zimbabwensis are able to complete their entire life-cycle in both poikilothermic and homoiothermic animals.

PHASMID ULTRASTRUCTURE OF AN ASCARIDOID NEMATODE HYSTEROTHYLACIUM AUCTUM

Here, for the first time in an ascaridoid (Hysterothylacium auctum), we present structural features of the phasmids, paired sense organs, positioned in a bilateral manner close to the point of the tail; the features were obtained using scanning and transmission electron microscopy. We found that each phasmid consists of a single ciliated dendritic process situated in a phasmidial canal surrounded by 2 supporting cells, a socket and a sheath cell. The socket cell contains clusters of electron-dense fibrous material in its apical region and covers the phasmidial canal along its whole length. The sheath cell is characterized by a well-developed endoplasmic reticulum. The phasmidial canal is lined with a thin layer of cuticle that becomes incomplete at the base of the ciliated dendritic process. In this region, the dendritic process consists primarily of a high number of microtubule singlets and some peripheral microtubule doublets. The base of the dendritic process, containing numerous striated rootlets, gives off a large number of fingerlike offshoots, villi, invading the surrounding sheath cell. The systematic significance and functional implication of the phasmid in nematodes are also discussed.