Enteric disease in specific-pathogen-free turkey poults inoculated with a small round turkey-origin enteric virus

Four- and 5-day-old specific-pathogen-free turkey poults were inoculated orally or by contact exposure to a small round turkey-origin enteric virus. At days 4 and 8 postinoculation (PI), the orally inoculated poults had significantly lower body weight gains than control poults. Poults at day 4 (orally inoculated) and 5 (contact-exposed) PI had watery droppings, dilated thin-walled ceca filled with yellow foamy fluid, catarrhal small intestinal secretions, pale intestinal serosa, and mild lymphocytic enteritis. In addition, at day 4 PI, poults were lymphopenic, had intracytoplasmic crystalline arrays of 17.1 +/- 1.1 nm viral particles in the jejunal villar enterocytes, and had an 18-to-24-nm virus in intestinal contents. Analysis of morphometric data revealed mild shortening of villi in the duodenum and elongation of crypts in the duodenum and ileum during the late stage of the syndrome (day 8 PI). These findings suggest that the 18-to-24-nm virus can produce an enteric disease syndrome and that the acute clinical manifestation of this syndrome is not the result of morphologic change such as intestinal villus atrophy. The definitive identity of this 18-to-24-nm virus is not known; however, based on size and intracytoplasmic arrays of virus, it is most probably an enterovirus.     

雏鹅实验性副粘病毒病的临诊症状及病理变化研究

用鹅副粘病毒BY株人工感染5日龄雏鹅，观察试验鹅的临诊症状和病理学变化。试验鹅最早于2d出现症状，3d开始死亡，死亡高峰期在3－5d,7d后停止死亡，总计试验鹅发病率为89.19%，死亡率为64.86%。主要临诊症状为精神不振，食欲降低或废绝，拉稀，流泪，流鼻液。主要大体病变为消化道粘膜的水肿、出血、坏死以及胰腺、脾脏组织的严重坏死。主要组织学变化为腺胃、肠道粘膜上皮细胞和胰腺腺泡上皮细胞严重变性、坏死、胸腺、脾脏、法氏囊等器官内淋巴细胞坏死、崩解，数量显著减少。     

Adenovirus enteritis in pigs

Experimental transmissions were done with adenovirus strain 6618 in hysterectomy-produced colostrum-deprived pigs. After an incubation period of 3 to 4 days, all inoculated animals had diarrhea. Histopathologically, many intranuclear inclusion bodies were present on short villi of the terminal parts of jejunum and ileum. With electron microscopy, the inclusion bodies were observed to contain numerous adenovirus particles. Immunoperoxidase-positive cells were seen on short villi of the terminal parts of jejunum and ileum. Adenovirus particles also were detected by negative staining of intestinal contents. In 1 pig (naturally occurring infection), adenovirus enteritis was studied by the aforementioned techniques. Similar intestinal lesions as described in the experimental pigs were observed.     

Comparative virulence of two porcine group-A rotavirus isolates in gnotobiotic pigs

The virulence of 2 porcine group-A rotavirus isolates was compared. Forty hysterotomy-derived 3-day-old gnotobiotic pigs were inoculated orally with 2 ml of intestinal homogenate containing either the Ohio State University (OSU) or the South Dakota State University (SDSU) strain of porcine rotavirus or were inoculated with medium only. Clinical signs of disease, body weight, distribution of viral antigen, fecal excretion of virus, and histologic lesions (observed by light and scanning electron microscopy) were determined. Morphometric measurements of villi and crypts were made. In pigs inoculated with OSU or SDSU strains, diarrhea began at postinoculation hours (PIH) 19 to 48 and PIH 24 to 54, respectively. None of the virus-infected pigs died as a consequence of infection and all had similar clinical signs of disease, body weight changes, and virus-shedding patterns, regardless of the strain of rotavirus with which they were infected. Microscopic findings in the small intestine of virus-infected pigs were similar, except that the SDSU strain caused more severe villus atrophy and villus fusion in the duodenum at PIH 72 and 168 than was associated with the OSU strain. Viral antigen in the small intestine of pigs infected with either virus was observed by use of immunofluorescence at PIH 24 and 72, but was seldom seen at PIH 168.     

Enteropathogenicity of Dutch and German avian reoviruses in SPF white leghorn chickens and broilers

The enteropathogenicity of avian reoviruses (ARVs), isolated from chickens affected with malabsorption syndrome (MAS) from The Netherlands and Germany was studied. In the first trial seven different ARVs isolated from MAS cases were inoculated in 1-day-old specific pathogenic free (SPF) white leghorns. The pathogenicity was compared with 2 ARVs isolated from cases of tenosynovitis, namely reference strain S1133 and a Dutch strain. Although a difference in the severity of the clinical disease was observed, all reoviruses could induce vacuolar degeneration and sloughing of the epithelium of the small intestine at day 2 post inoculation (PI) till day 7 PI. Two Dutch and one German ARV derived from MAS causing the most severe intestinal lesions at day 2 PI, were further studied in the second trial using SPF broilers. These reoviruses did not cause weight gain depression in the broilers although lesions in the small intestine were present from day 1 up to day 4 PI and were more severe than in the white leghorn chickens. In one of the inoculated groups apical denuded villi were already present at day 1 PI. At day 7 PI the small intestine of the infected broilers appeared to be normal. Reovirus antigen was detected in the cytoplasm of the enterocytes at the tip and middle section of the affected villi both in layers and in broilers. To study the role of intestinal CD4+ and CD8+ T-cells and macrophages/monocytes in the pathogenesis of ARV, the numbers of these cells of the jejunal villi of one infected and the control broiler groups were compared. CD4+ T-cells were detected in low numbers and only in the infected broiler group at day 14 PI. The numbers of CD8+ T-cells and macrophages/monocytes were significantly higher in the infected broiler group than in the control broiler group at day 7 and 14 PI and at day 7 PI respectively. Our study indicates that the reovirus alone cannot induce intestinal lesions as found in MAS chickens. Moreover, CD8+ T-cells may play a major role in the pathogenesis and or reovirus clearance in the small intestine.     

Intestinal lesions in specific-pathogen-free lambs associated with a cryptosporidium from calves with diarrhea

Small and large intestines of seven specific pathogen-free lambs infected with cryptosporidia from calves with diarrhea were examined by scanning and transmission electron microscopy and by light microscopy. The small intestine was infected in all the lambs, and the cecum and colon in three. Small intestinal alterations were severe villous atrophy and dilatation of the crypts of Lieberkühn. Epithelial cross-bridging between contiguous villi caused much villous fusion. Epithelial cells constituting the bridges were connected by desmosomal junctions, and were continuous with the epithelial coverings of the associated villi. The lamina propria was heavily infiltrated with neutrophil leukocytes. Infected crypts in cecum and colon were dilated and devoid of mucus-secreting cells, while the ridges between crypts were hypertrophied, and the lamina propria was infiltrated by neutrophils. Cell vegetations with adherent bacteria were present in the surface intestinal epithelium of two lambs infected for 11 and 14 days, respectively. No adherent bacteria were seen in any site in lambs killed up to six days post-inoculation.     

Experimental enteric infection of gnotobiotic piglets with Chlamydia suis strain S45

Enteric chlamydial infections of pigs with Chlamydia (C.) suis are frequent and often subclinical. The enteric pathogenicity of C. suis strain S45 was investigated in gnotobiotic piglets. Piglets from three litters (n=31) were inoculated with egg-grown chlamydiae at 2-3 days of age (n=17) or used as controls (n=14). They were observed for clinical signs, killed and necropsied sequentially at 2-13 days postinoculation (DPI). Feces were collected daily and investigated with an ELISA for chlamydial antigen. At necropsy, specimens were collected for histopathology and for immunohistochemical, PCR-based, and serological (complement fixation test, ELISA) detection of chlamydiae. Chlamydial replication and associated symptoms and lesions were observed from 2 to 13 DPI and were particularly pronounced within the first week PI. Clinical symptoms consisted of moderate-to-severe diarrhea, slight and transient anorexia, weakness and body weight loss. Immunohistochemistry and ELISA revealed that chlamydial replication was particularly marked at 2-4 DPI and primarily located in the small intestinal villus enterocytes. Further sites of replication included large intestinal enterocytes, the lamina propria and Tunica submucosa, and the mesenteric lymphnodes. Histopathological changes included moderate-to-severe villus atrophy with flattened enterocytes and focal villus tip erosions, and moderate mucosal inflammatory cell infiltrates and lymphangitis in the small intestine. PCR of spleen tissue and blood was mostly negative for chlamydiae, indicating that they did not substantially disseminate into the host up to 13 DPI. All sera were negative for anti-chlamydial antibodies. In conclusion, C. suis strain S45 elicited significant enteric disease and lesions in gnotobiotic piglets indicating its pathogenic potential for swine.     

Intestinal migrations of Trichostrongylus retortaeformis (Trichostrongylina,Trichostrongylidae) in the rabbit

Observations were made on histological sections of the stomach and small intestine of seven rabbits infected with Trichostrongylus retortaeformis and from one uninfected control rabbit. At 12h post-infection, larvae were found in the small intestine. At first, only a few larvae were observed entering the mucosa through capillaries of the stroma of villi; the majority of larvae remained in the intestinal lumen, within mucus of the crypts. We consider that the presence of the worms in the stroma is the result of a larval migration. From a phyletic point of view, this migration is interpreted as an ancestral memory of the pulmonary migration seen in the primitive Strongylida.     

Follicle associated epithelium of the gut associated lymphoid tissue of cattle

The morphology of the gut-associated lymphoid tissue of the small and large intestine in three gnotobiotic calves was examined by scanning and transmission electron microscopy, and the distribution of specialized membranous cells present in the follicle associated epithelium was defined. Isolated follicles remaining in the ileum of a cow after involution of the continuous Peyer's patch were examined by scanning electron microscopy. The presence of membrane-bound particles, reported to be exclusively associated with the continuous Peyer's patch, was investigated in other gut-associated tissue of the small and large intestine of the calf. The presence of two types of follicle associated epithelium in the small intestine of the calf was confirmed, and the follicle associated epithelium of the large intestine proved to be a homogeneous population of specialized membranous cells, similar to that of the continuous Peyer's patch of the small intestine. In the discrete Peyer's patches, some specialized membranous cells were completely hidden by adjacent enterocytes and could only be identified by cytoplasmic extensions into the intestinal lumen. In the proximal part of the continuous Peyer's patch, a transitional zone was detected where the follicle associated epithelium of some doomed villi was composed of a homogeneous population of specialized membranous cells, while the epithelium covering other doomed villi consisted of a mixture of absorptive and specialized membranous cells, usually only found in the discrete Peyer's patches. Membrane-bound particles were observed associated with gut-associated lymphoid tissue in the small and large intestine.     

Pathology of natural rotavirus infection in clinically normal calves

During a longitudinal study of the epidemiology of rotavirus infection in a calf rearing unit, excretion of virus in faeces was detected by enzyme-linked immunosorbent assay in 40 of 48 (83 per cent) unweaned calves aged between three days and five weeks. Fifty per cent of the infected calves had no clinical signs of disease. Enterocytes containing rotavirus antigen and intestinal lesions were found in all of 12 clinically normal calves selected for necropsy between days 1 and 4 of virus excretion. Stunting and fusion of villi, exfoliation, disarrangement and vacuolation of enterocytes and the presence of cuboidal enterocytes were observed in infected calves but not in rotavirus-free control calves. Lesions predominated in the upper small intestine, where rotavirus was most abundant, especially on the first two days of virus excretion. The numbers of enterocytes infected with rotavirus diminished before the lesions resolved.     

The pathology of experimental respiratory infection with Pasteurella multocida and Bordetella bronchiseptica in rabbits

Groups of female New Zealand White rabbits, 8-10 weeks old, were inoculated intranasally with three different Pasteurella multocida serotypes (A:3, A:4 and A:12) or one of three Bordetella bronchiseptica strains of rabbit origin. Seven out of 18 rabbits died of experimental infection with P. multocida. B. bronchiseptica killed 3 out of the 8 animals inoculated with it. Deaths occurred between 3 and 6 days postinoculation (PI). In the rabbits that died of P. multocida inoculation, necropsy and histology revealed severe pleuritis with the accumulation of a remarkable amount of fibrinopurulent exudate in the thoracic cavity, serous rhinitis and tracheitis, acute hepatitis with necrotic foci in the parenchyma, and atrophy of the lymphoid organs and tissues. Rabbits killed 10 days PI developed only subacute serous rhinitis and hyperplasia of the lymphoid tissues. Rabbits that died of B. bronchiseptica inoculation showed acute serous rhinitis, acute catarrhal-fibrinopurulent pneumonia and mild pleuritis. As opposed to P. multocida inoculated animals, hepatitis and atrophy of the lymphoid tissues were not characteristic of these rabbits. Rabbits killed 10 days PI developed subacute purulent and necrotic pneumonia with remarkable macrophage proliferation, involving all lobes, and hyperplasia of the lymphoid tissues.     

Studies on the evolution, pathology, and immunity of commercial fattening rabbits affected with epizootic outbreaks of diarrhoeas in Mexico: a case report

Epizootic outbreaks of diarrhoeas have emerged and disseminated in different rabbit farms in Mexico causing great economical losses, during the past years. Seven, 5-weeks-old New Zealand White (NZW) rabbits chosen at random from 35 ill animals that were remitted for postmortem, histopathology, and ultrastructural examinations were studied. Bacteriological and parasitological studies were carried out in three additional ill rabbits of same age. In a field trail 45, 5-weeks-old apparently healthy NZW rabbits were observed daily for sanitary status for a 5-week period. Some of the rabbits did not response to the preventive drug treatment and were therefore, used to study the development of the disease. Clinical signs, gross lesions, and mortality throughout the fattening period were recorded. Eight, 8-weeks-old NZW rabbits who survived an outbreak were assessed for gamma-globulins in serum of the total protein fraction during a 3-week period. Gamma-globulins were also measured in eight free-disease healthy rabbits of same breed and age. Lesions of the small intestine consisted of mucoid enteropathy, lymphocytic plasmocytic enteritis with atrophy and fusion of villi, and hyperplasia of globet cells. Serosal edema was present. Ultrastructural examinations of jejunum and ileum from 3/7 diseased rabbits, revealed enterocytes in apoptosis, mixed with degenerative and/or necrotic changes together with infiltration of lymphocytes, macrophages, neutrophils, and loss of microvillus. There were electron dense structures suggestive of virus particles inside the nuclei and cytoplasm of some enterocytes. There was lymphoid spleen atrophy and proliferation of reticuloendothelial cells in 7/7 rabbits. Interstitial pneumonia in 4/7 rabbits was found. Encephalitozoon cuniculi was detected in the brain of 1/7 rabbits. Escherichia coli were detected in 3/3 cases and Eimeria spp. in 2/3 cases. Mortality rate in the field study was 51.1% and the spread of the disease occur in 9/9 cages. The proportion of gamma-globulins in rabbits who survive an outbreak was much lower (P=0.0001) than free-disease healthy rabbits (8.1+/-1.0 and 14.0+/-1.0, respectively). The disease was multifactorial and consisted of sub-acute mucoid enteropathy probably induced by viral infection and aggravated by the proliferation of opportunistic pathogens common to rabbits. This may explain the severe degenerative and necrotic changes observed in the small intestine of diarrhoeic rabbits.     

The role of K antigens of enteropathogenic Escherichia coli in colonization of the small intestine of calves.

The colonizing and proliferating abilities of enterotoxigenic acapsular or K99- mutants of bovine enteropathogenic Escherichia coli strains were compared with those of their capsulated and K99+ parent strains in the small intestine of infected colostrum-fed calves. Calves infected with the enteropathogenic E. coli parent strains developed profuse diarrhea and severe dehydration. None of the calves which received the acapsular mutant developed diarrhea and one of three calves inoculated with the K99- enterotoxigenic mutant developed moderate diarrhea. The parent enteropathogenic E. coli strains colonized the middle and lower small intestine; in these areas a layer of specific immunofluorescence against the enteropathogenic E. coli covered most villi and 80% of the organisms were associated with the intestinal wall. The acapsular mutant strain failed to colonize the small intestine and fluorescent bacteria were not observed in any area of the small intestine. The K99- mutant proliferated to a lesser extent than did the K99+ parent strain in all areas of the small intestine but moderately colonized the lower small intestine where fluorescent bacteria were observed to cover parts of the intestinal villi.     

Lesions of gnotobiotic calves experimentally infected with a calicivirus-like (Newbury) agent

Fourteen gnotobiotic calves were killed 0.5 to ten days after infection with Newbury agent SRV-1 and the changes in small intestinal structure and function were assessed, qualitatively and quantitatively, by light microscopy, scanning and transmission electron microscopy, enzymology and xylose absorption. The first enterocytes detected as infected by immunoperoxidase were those on the sides of villi at the base. Subsequently exfoliation of degenerate enterocytes resulted in stunted villi; mucosal beta-galactosidase activity fell and there was xylose malabsorption. Small intestinal damage, first detected at 12 hours after infection but almost repaired by ten days, was restricted to the anterior half of the small intestine. In the distal small intestine, where no virus-induced damage occurred, villi lengthened--possibly due to increased mitosis of crypt cells stimulated by enteroglucagon release.     

Fatal cryptosporidiosis in quail

Young quails kept in wire-floored cages experienced high mortality, beginning at age 5 days, from diarrhea that was unresponsive to antibiotic therapy. At necropsy, the small intestine had clear fluid content and the cecum was distended by brown foamy fluid. Histopathologic findings in the small intestine were shortened villi with detached enterocytes at the tip. Cryptosporidium sp. (confirmed by electron microscopy) were numerous in the microvillous border. Neither bacterial nor viral pathogens were detected. No infection was established in day-old chickens gavaged with feces and intestinal contents from infected quails. Thorough cleansing of the cages followed by application of commercial bleach prevented recurrence.     

Experimental Chlamydia psittaci serotype 1 enteric infection in gnotobiotic piglets: Histopathological,immunohistochemical and microbiological findings

The enteric pathogenicity of the ovine C. psittaci serotype 1 isolate S26/3 was assessed using a litter of gnotobiotic piglets. In one group, eight piglets were inoculated at 3 days of age; at 10 days, two of these were re-inoculated. In a second group, six animals were mock-inoculated at 3 days of age as negative controls; subsequently, at 10 days, three of these piglets were inoculated with C. psittaci. The animals were observed for clinical signs, killed and necropsied sequentially between 4 and 17 days of age. At necropsy, specimens were collected for histopathology, immunohistochemistry and serology. Clinical manifestations consisted of sporadic slight softening of faeces observed between 8 and 12 days post inoculation (d.p.i.) in pigs inoculated at 3 days of age and between 4 and 6 d.p.i. in those inoculated at day 10. Histopathological changes were minimal and inconsistent and occurred almost exclusively in the small intestine in pigs of 15 days of age and older; they consisted of a slight shortening of villi, of a small number of tongue-shaped villi and of villous fusions. Immunohistochemistry revealed small numbers of chlamydial inclusions in the small intestinal enterocytes of only five pigs, all killed within 5 d.p.i. An ELISA run on faecal samples collected daily after inoculation from six of the pigs showed that chlamydial antigen was excreted in the faeces. In pigs inoculated at 3 days, chlamydial antigen was detected inconsistently before, and consistently after 9 d.p.i. Pigs inoculated at 10 days excreted antigen consistently after inoculation until the end of their observation period (8 d.p.i.). Infective chlamydiae were detected from the faeces of inoculated piglets using Vero cell cultures. Sera of all pigs were negative for anti-chlamydial antibodies using a complement fixation test. In conclusion, enteric pathogenicity of C. psittaci serotype 1 in a litter of gnotobiotic piglets proved minimal. The results, therefore, indicate that serotype 1 C. psittaci is not likely to cause enteric disease in conventionally reared pigs. Nevertheless, a potential role of swine in the epidemiology of this agent should be considered with regard to spread of Chlamydia to other species.     

Experimental transmission of sheep scrapie by intracerebral and oral routes to genetically susceptible Suffolk sheep in the United States.

Scrapie is a naturally occurring fatal neurodegenerative disease of sheep and goats. Susceptibility to the disease is partly dependent on the genetic makeup of the host. This study documents clinicopathological findings and the distribution of abnormal prion proteins (PrPres) by immunohistochemical and Western blot techniques, in tissues of genetically susceptible sheep inoculated with US sheep scrapie agents. Four-month-old Suffolk lambs (QQ or HQ at codon 171) were inoculated (5 intracerebrally and 19 orally) with an inoculum (#13-7) consisting of a pool of scrapie-affected sheep brains. Intracerebrally inoculated animals were euthanized when advanced clinical signs of scrapie were observed. Orally inoculated animals were euthanized at predetermined time points (4, 9, 12, 15, and 21 months postinoculation [PI]) and thereafter when the animals had terminal signs of disease. All intracerebrally inoculated animals exhibited clinical signs of scrapie and were euthanized between 13 and 24 months PI. Spongiform lesions in the brains and PrPres deposits in central nervous system and lymphoid tissues were present in these sheep. In orally inoculated sheep, clinical signs of scrapie were seen between 27 and 43 months PI in 5/9 animals. The earliest detectable PrPres was observed in brainstem and lymphoid tissues of a clinically normal, orally inoculated sheep at 15 months PI. Three of the 4 clinically normal sheep were positive at 15, 20, and 49 months PI by PrPres immunohistochemistry.     

Comparison of intestinal mucosa homogenate and pure culture of the homologous Lawsonia intracellularis isolate in reproducing proliferative enteropathy in swine

Little information is available on reproduction of proliferative enteropathy (PE) using a virulent pure culture of Lawsonia intracellularis. Reproduction of the disease using PE-diseased mucosa homogenates, however, is well-characterized. The aims of this study were to evaluate and compare clinical signs, growth performance and the severity of lesions in pigs inoculated with intestinal mucosa homogenate or pure culture of the homologous L. intracellularis isolate. Five-week-old pigs were inoculated with pure culture of L. intracellularis (isolate PHE/MN1-00; n=10), PE-diseased mucosa (n=10), or control media (n=4). The L. intracellularis isolate PHE/MN1-00 used in the pure culture inoculum was extracted from a fragment of the same intestine used to prepare the mucosa homogenate. Clinical signs and growth performance were evaluated throughout the study. Fecal shedding was evaluated in all animals weekly during the experiment. All animals were euthanized 22 days post-inoculation, the intestines were examined grossly and histologically. Results showed that both the infection procedures reproduced clinical disease, macroscopic and histologic lesions typical of PE. Fecal shedding was detected in animals in both challenge groups. In conclusion, the L. intracellularis isolate PHE/MN1-00 reproduces typical clinical signs and lesions of PE similar to the homologous infection with an intestinal mucosa homogenate.     

Bacterial colonization and morphology of the intestine in porcine Escherichia coli enterotoxemia (edema disease)

Twenty-one pigs were divided into three groups. Pigs in one group were inoculated with the intestinal contents which included bacteria from a pig with edema disease. Pigs in another group were inoculated with a culture of Escherichia coli serogroup O 139:K12(B):H1 isolated from the aforementioned contents, and pigs in a third group served as uninoculated controls. The infection was similar following both inocula. Enterotoxemia developed in 11 of the 14 pigs allowed to survive for more than two days. The onset varied from two to seven days after inoculation. There were maximal viable counts of E. coli in the intestine from the second day post-inoculation and thereafter. In frozen and paraffin sections, as well as by scanning electron microscopy, the organisms were seen on the surface of the small intestinal epithelium where they formed either isolated colonies or continuous layers. They colonized the lower small intestine more intensely than the upper section. The intestinal epithelium and the villi of infected pigs were indistinguishable morphologically from the tissues of three uninoculated control pigs. The diarrhea which was observed in controls and inoculated pigs before inoculation and the villus atrophy in controls and inoculated pigs indicated a preexisting infection with at least one other agent.     

Pathogenesis of canine parvovirus-2 in dogs: histopathology and antigen identification in tissues

The pathogenesis of canine parvovirus-2 was studied in orally inoculated conventional dogs using histopathological and peroxidase anti-peroxidase staining techniques. Lymphoid necrosis and depletion of lymphocytes from lymphoid tissues were most notable on days 5 and 6 after exposure. Lymphocyte hyperplasia occurred following day 7. Epithelial cell changes in segments of the small intestine were more severe on days 6 to 9 after exposure in areas associated with Peyer's patches and in the upper segments of the small intestine. The lymphocyte was the primary infected cell. Virus infected cryptal epithelial cells were not detected until 24 hours after the identification of infected cells in lymphoid tissues on day 4 after exposure. The majority of virus infected epithelial cells were found in crypts intimately associated with or adjacent to Peyer's patches in the upper segments of the small intestine.