Branched Mycobacterium-like organisms from swine lymph nodes.

Branched, weakly acid fast organisms were isolated from 5 of 112 caseous lymph nodes derived from slaughter-house pigs. In two cases they were associated with typical Mycobacterium avium strains. The bacteria differed from all other mycobacteria known at present. Limited experiments in pigs with one strain failed to disclose a possible pathogenic role in the host species although this strain was pathogenic for mice. Tests with this and three other strains showed that all four were apathogenic for chickens.

Evaluation of the bovine corneal opacity-permeability assay as an in vitro alternative to the Draize eye irritation test.

The bovine corneal opacity-permeability assay (BCO-P) was evaluated as an in vitro alternative test model for the Draize eye irritancy test. Fifty pharmaceutical and commercially available compounds were tested in the BCO-P assay. The compounds were selected on the basis of their in vivo irritancy potential as determined in previous Draize tests. Liquids as well as solids were tested. Corneal opacity and permeability were measured to determine ocular irritation potential. When two irritancy classifications (non-irritant and irritant) were considered, 96% of the tested chemicals were classified correctly. A 72% concordance was obtained when four irritancy classifications (non-irritant, mild, moderate and severe irritant) were considered. Furthermore, all compounds that were severe eye irritants in vivo were equally scored in vitro. The results of this study show that the BCO-P assay is a competent in vitro test system for the prediction of ocular irritation of chemicals. This test model can be used as a first screen to avoid in vivo testing of severe ocular irritants.

In vivo action of the anticoccidial diclazuril (Clinacox) on the developmental stages of Eimeria tenella: a histological study.

Diclazuril, a new benzeneacetonitrile anticoccidial, has potent activity against various stages of Eimeria tenella. A single treatment of experimentally infected chickens during the prepatent phase (up to day 5) results in a complete interruption of the life cycle and oocyst shedding. The first- and second-generation schizonts show extensive degenerative changes that finally result in a complete loss of the parasitic stage. The degeneration is characterized by loss of internal structure, the appearance of many intracytoplasmic vacuoles, and incomplete merogony. The merozoites themselves show similar degenerative changes, including the presence of numerous small vacuoles in the cytoplasm. Diclazuril is also effective against both the micro- and macrogametocytes that have a ballooned appearance and loose their internal structure completely. In the macrogametocytes, wall-forming bodies either do not develop or disappear rapidly. Development of typical caecal lesions is prevented when treatment with diclazuril is initiated before large numbers of second-generation schizonts appear, i.e., day 3. It is concluded that diclazuril is lethal against both the asexual and the sexual stages of E. tenella. At the proposed use level of 1 ppm in the feed, the life cycle is interrupted at a very early stage and lesion development and oocyst shedding are completely prevented.

In vivo action of the anticoccidial diclazuril (Clinacox) on the developmental stages of Eimeria tenella: an ultrastructural evaluation.

A single 5-mg/kg oral dose of diclazuril affected both the asexual and sexual development of Eimeria tenella in experimentally inoculated chickens. In second-generation schizonts, early growth and nuclear divisions progressed normally, but a marked inhibition of merozoite formation was observed. Exogenesis of merozoites was largely prevented, whereas production of micronemes, amylopectin granules, and dense bodies and the formation of rhoptries, conoid, and pellicle continued. All these subcellular organelles accumulated, together with differentiated nuclei, within the main cytoplasmic mass. In the end, complete necrosis of the schizonts occurred. In macrogamonts, dilation of the rough endoplasmic reticulum around type II wall-forming bodies, fusion of type II wall-forming body contents, disturbance of the normal parallel arrangement of rough endoplasmic reticulum, and disruption of row formation of amylopectin granules became evident. In the microgamonts, normal evagination of microgametes was prevented; the flagellar complex formed within the main cytoplasmic mass and the differentiated nuclei remained present within the parasite body. The macro- and microgamonts also ended up in a stage of complete necrosis. These data indicate that diclazuril treatment primarily affects the normal differentiation of the respective endogenous stages during parasite development. This leads to complete degeneration of schizonts and gamonts indicating the lethal effect of this new anticoccidial compound.

Spontaneous and experimental myofibrillar hypoplasia and its relation to splayleg in newborn pigs.

The relation of myofibrillar hypoplasia to clinical splayleg was studied. A strain of Belgian Landrace sows was selected for this study because they produced pigs which had no myofibrillar hypoplasia. Myofibrillar hypoplasia could nevertheless by induced experimentally in these animals by dexamethasone treatment of the sows during late pregnancy. The lesion was observed without clinical signs and was compared to the myofibrillar hypoplasia in clinical cases of splayleg. The differences between these 2 groups may account for the appearance of clinical signs. These differences included the maturity of the myofibrils and the degree of autophagolysosomal glycogen breakdown.

Immunoperoxidase study of Aujeszky's disease in pigs.

Viral antigen was detected by an immunoperoxidase technique in histological sections from pigs with Aujeszky's disease. The antigen was found mainly in association with focal necrosis in the cerebellum, tonsils, oral and nasal mucosa, salivary glands, lungs, liver, kidneys, pancreas, spleen and adrenal glands. Cells at the margin of the necrotic foci especially were strongly positive. Viral antigen was also demonstrated in the cerebral cortex and in the brain stem. Two types of intranuclear inclusion bodies were found to contain viral antigen and one type also contained viral nucleic acids. Inflammatory cells usually contained no viral antigen. The possible significance of some of these infected tissues in the excretion of the virus is discussed.

Action of the anticoccidial clazuril on the endogenous stages of Eimeria labbeana and E columbarum in experimentally infected pigeons.

Racing pigeons were artificially infected with a mixed inoculum of Eimeria labbeana (85 per cent) and E columbarum (15 per cent) and treated orally with 2.5 mg clazuril either on day 1, 2, 3, 4, 5, 6 or 7 after infection. The impact of the treatment on the different developmental stages was evaluated by oocyst output and by histological examination of the duodenum and jejunum. The life cycle always became completely interrupted, but maximal effects were noted when treatment was given on day 4, 5 or 6 after infection. Treatment during patency completely interrupted oocyst excretion within three days after dosing. Degenerative changes in schizonts and gametocytes were always observed. The histology revealed a reduced number and abnormal structure of developing merozoites; a ballooned aspect and presence of numerous small vacuoles in the microgametocytes; the absence of typical wall-forming bodies in macrogametocytes and a complete absence of oocysts. It is concluded that clazuril has a coccidiocidal effect on the asexual and sexual developmental stages of both Eimeria species, resulting in a complete interruption of the life cycle.

Demonstration of canine distemper viral antigen in paraffin sections, using an unlabeled antibody-enzyme method.

A peroxidase technique was used for the immunohistochemic demonstration of canine distemper viral antigen in formalin-fixed and paraffin-embedded tissues. The antigen was detected in epithelial cells and nerve cells of young dogs. The application of a combined peroxidase and hematoxylin and eosin stain as a diagnostic technique is discussed.

Demonstration of pseudorabies viral antigen in thick and ultrathin tissue sections of young pigs using an immunogold method.

Pseudorabies (Aujeszky's) virus antigens were labeled in thick and ultrathin tissue sections of young pig brain and liver tissue, using an indirect immunogold method. Antigens were tagged with 20 nm gold particles. Controls proved the specificity of the reaction in paraffin sections and ultrathin epoxy sections. Immunogold staining was compared with immunoperoxidase staining in paraffin sections. In ultrathin sections stained with the immunogold method, the gold particles were present on viral nucleocapsids and viral envelopes, as well as on a number of other intracellular structures. These included the inner nuclear membrane, the nucleoplasm, intranuclear filaments, the endoplasmic reticulum, and free cytoplasmic polyribosomes. Gold particles were absent on mitochondria and microtubules. In paraffin sections, immunogold labeling for pseudorabies virus antigen was less sensitive than immunoperoxidase staining. Immunogold staining of ultrathin tissue sections can yield additional information on virus-host cell interactions.

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.

Baby pig diarrhea caused by coccidiosis.

An outbreak of coccidiosis on two Belgian farms is described. Diarrhea started in piglets at 9 or 10 days of life. Zero to three pigs died per litter. The morbidity rate varied from 70 to 90 per cent. Histological examination of the intestines revealed shortening of villi and different stages of the life cycle of coccidia were seen in the enterocytes. Virological examination was negative for corona-, corona-like, and rotavirus. A haemolytic E. coli strain was isolated in one case. As for treatment, good results were obtained by the adding of 1 kg amproleum pre-mix per ton sow feed. Scouring pigs were treated orally with 2 cc of an amprol solution once a day. The diarrhea stopped one day after treatment.

Dual adenovirus and distemper virus pneumonia in a dog.

A case of simultaneous infection of the lungs of a dog with canine distemper virus (CDV) and canine adenovirus (CAV) is described. The techniques employed are histological stains, immunoperoxidase technique, and transmission electron microscopy. Two viruses are shown to infect the same cells. The significance of dual infection of the same cells is discussed in comparison with literature data on in vitro experiments.

Space occupying lesions of cranial nerves in calves with facial paralysis.

Clinical and pathological data of a recently discovered neurological disorder in young calves were studied. The symptoms were those of a paralysis of the nervus facialis and a dysfunction of the nervus vestibulocochlearis. Macroscopically, space occupying lesions were found at the roots of these two cranial nerves and in some cases further on their course into the os petrosum. On histological examination, these legions contained multiple nodules with mainly histiocytic cells, some plasma cells and multinucleated giant cells. Around these nodules, dense bands of connective tissue with fusocellular fibroblasts, some plasma cells and small blood capillaries were present. The nodular lesions were usually in close contact with the nerve. Ultrastructurally, a variety of cells, predominantly histiocytes and some plasma cells, were seen next to Schwann cells which contained degenerating axons.

[Safety of a new anticoccidial agent, clazuril, during reproduction in carrier pigeons]. / Veiligheid van een nieuw anti-coccidiosemiddel clazuril tijdens de kweekperiode bij postduiven.

In a six-month study, the safety of repeated treatments with clazuril, a new anticoccidial agent for the treatment of pigeons, was evaluated during 4 to 5 consecutive reproduction cycles. Clazuril was administered weekly at the recommended therapeutic dose level of 2.5 mg/pigeon and at twice this dose. The results were compared to placebo treatment. Evaluation was based on the following parameters: reproductive behaviour, egg laying, fertilisation, embryonic mortality, hatching, percentage of weaning and time interval between consecutive reproductive cycles. Maternal-paternal toxicity (body weight evolution, feather coat) and tolerance in newborn pigeons (general behaviour, daily gain in body weight, feathering, skeletal anomalies) were also evaluated. In all the treatment groups, reproductive performance was comparable and no drug- or dose-related side-effects were observed. Fertilisation, embryonic mortality and the time-interval between the consecutive reproductive cycles remained within the normal physiological range. Hatched pigeons showed a satisfactory daily weight gain and deaths among these birds were exceptional. Tolerance of clazuril in adult as well as in day-old pigeons was exceptionally good and body weight evolution, feathering and mortality were not adversely affected. No drug-related pathological findings or skeletal anomalies were detected in the animals at autopsy. It can be concluded that repeated treatments with clazuril are entirely harmless for pigeons during reproduction, even at double the therapeutic dose level. Clazuril is well tolerated by newborn and growing pigeons, which means that pigeon house group treatments during reproduction may be performed without any risk.

Replication of porcine enteric adenoviruses in vivo.

The replication of an enteropathogenic porcine adenovirus in the intestinal epithelial cells of naturally and experimentally piglets has been studied by transmission electron microscopy (TEM) and by immunoperoxidase (Ip) staining of paraffin sections. Three types of intranuclear inclusion bodies were observed. Viral particles appeared to be assembled from electron dense crescents which seemed to originate from type II intranuclear inclusion bodies. Virus accumulated in the nucleus of infected cells. It formed paracrystalline arrays in the electron dense centre of the nucleus but was dispersed in the peripheral electron translucent zone. Virus was released from the cells after rupture of the nuclear and plasma membranes. The results are compared with published data on the replication of adenoviruses in cell cultures.