Fine structure of Plasmodium gallinaceum in embryonic and neonate chicks

The erythrocytic stages of Plasmdoium gallinaceum in chicken embryos injected with parasited blood either from a syringe-passaged infection in chickens or from a chicken infected with sporozoites were characterized by abnormal structure. Particularly evident were large, unstained vacuoles within the cytoplasm; these occurred with greatest frequency in schizonts. The presence of myelin bodies within these vacuoles was revealed by transmission electron microscopy; abnormal cytokinesis and aberrant merozoites provided additional evidence of the parasite's inability to develop naturally within the milieu of the embryonic erythrocytes. Fifty-five passages were necessary to restore normal structure of the parasites in embryos, while only 5 passages were required for such restoration in neonate chicks. The probable adaptation of the parasite to the proportions of hemoglobin of the adult chicken may be responsible for the abnormal growth in the immature host.

Studies on the feeding of larval Argas persicus Oken

The development of the lesions caused by Argas persicus larvae while feeding on chickens, their natural hosts, was followed using histological techniques. Penetration of the skin by the mouthparts was accompanied by rapid lysis of the cells of the epidermis and dermis within 100 mum of the mouthparts. A foreign-body reaction developed within 2 mm of the attachment and was characterized by rapid dilation of blood vessels, emigration of leucocytes, particularly heterophil leucocytes (heterophils) into the tissues and oedema. Haemorrhage developed near to the mouthparts and within 2 h of the start of feeding, erythrocytes were seen in the gut caeca of the larvae. Whole blood provides the diet of the larva throughout the entire period of feeding and unlike the situation described with nymphal and adult. A. persicus the blood is lysed immediately after ingestion. By 30 h the extra-vascular heterophils had migrated to the mouthparts around which they formed a loose, superficial, collar. Further emigration of heterophils into the tissues then ceased, although some were present in the blood being ingested. It appears that the heterophils mask the mouthparts so that they are no longer recognised as foreign by the host and thus provide an example of the concept of adaptation tolerance. But the development of lymphocyte and monocyte infiltrations in the dermis close to the mouthparts indicates that the immunological response of the host to salivary secretions is not suppressed. Oedema which develops around the site of attachment further protects the larvae from the host's predations.

Enzyme variation in Eimeria species of the chicken

A method for the biochemical identification of protozoa belonging to the genus Eimeria is described for the first time. Starch gel electrophoresis of the enzymes lactate dehydrogenase, glucose phosphate isomerase, 6-phosphogluconate dehydrogenase and glucose-6-phosphate dehydrogenase from parasite extracts revealed both intra- and inter-species differences when 11 strains representative of 6 species of Eimeria were examined. Oocysts were the most accessible parasite stage for investigation but sporozoites and merozoites of an embryo-adapted strain of E. tenella were also examined for enzyme activity.

Scanning electron microscopy of the duodenal mucosa of chickens infected with Eimeria acervulina

The morphology of the duodenal mucosal surface of chickens infected with Eimeria acervulina has been studied on days 5, 6, 8 and 11 post-infection and compared with that of the normal duodenal mucosa using the scanning electron microscope. The normal duodenum possessed tall, spatulate villi with horizontally-arranged surface clefts upon which a regular pattern of hexagonal absorptive cells and goblet cell mouths was superimposed. A maximum degree of villous atrophy was shown on day 5 post-infection, the villi being thickened and flattened with frequent adhesions and fusions between them. The general effects of the disease together with the physical presence of intracellular parasites caused considerable changes in size and shape of the cell apices. By day 8 the mucosa was clearly recovering, with a normal pattern of somewhat thickened and truncated villi beginning to re-appear and by day 11 post-infection the mucosa had regained an outwardly normal morphological pattern. The mucosal changes are discussed in relation to similar changes which occur in diseases of the alimentary tract of other animals, including man.

Eimeria tenella in chickens: development of resistance to quinolone anticoccidial drugs

The development of drug resistance by the present Houghton strain of Eimeria tenella to the quinolones, methyl benzoquate and buquinolate, was found to take place after a single experimental passage. The development of resistance was independent of drug selection pressure and showed cross resistance to other quinolones, but not to amprolium and robenidine. When the Weybridge, Beltsville and Elberfeld strains of E. tenella were compared under similar laboratory conditions, the Weybridge and Elberfeld strains developed resistance to methyl benzoquate after 6 passages and the Beltsville after 5. Studies on the response of the Houghton strain to methyl benzoquate and buquinolate revealed that the drugs did not completely control the infection as measured by weight gain and that oocyst production was not suppressed. These observations indicate that the strain had already acquired some resistance to these drugs. This was confirmed by examining the resistance to methyl benzoquate of a culture of the Houghton strain of E. tenella which had been stored frozen in liquid nitrogen since 1969. This showed full sensitivity to the drug and developed resistance after 8 passages. This suggests that drug tolerance has been acquired by the Houghton strain since 1969. Oocyst lines were established from the Houghton strain by infecting single birds with approximately 10 oocysts. Eleven of these lines were found to be sensitive to methyl benzoquate, and nine to give rise to resistant parasites. It is concluded that the Houghton strain is contaminated by a small number of resistant oocysts which can be eliminated from a culture by dilution of the challenge inoculum. One of these Houghton oocyst lines, sensitive to methyl benzoquate, developed resistance after 8 serial passages.

[Genesis of merozoites in the coccidia, Eimeria necatrix. Ultrastructural study]

Second generation schizonts of Eimeria necatrix were studied with the aid of the electron microscope. Differentiation of daughter merozoites is associated with the last mitosis, which is not significantly different from the earlier ones. The merozoites develop at the periphery of the schizont. The conoid and 22 subpellicular microtubules, probably induced by centrioles, and the inner membranes complex and the rhoptry anlagen which seem to be produced by the Golgi apparatus, appear close to each nuclear pole, just near the schizont membrane. These organelles are the first to appear in the merozoite anlagen. Then, nucleus, dictyosome and multimembranous vescles enter the budding merozoites. Micronemes, probably originating from Golgi apparatus, and amylopectin granules are produced later, when daughter merozoites separate from the residuum. The genesis of these various organelles and the relation between the last mitosis and differentiation are discussed.

The life cycle of Echinoparyphium ralphaudyi sp. n. (Trematoda: Echinostomatidae)

The life cycel and morphology of Echinoparyphium ralphaudyi sp. n. is described. Natural infections were found in Bulinus truncatus from Egypt, Ethiopia, and the Yemen Arab Republic, and later in B. forskalii and B. sericinus from Ethiopia. Sporocysts develop near the places of miracidial entry into the snail (the head-foot region, mantle edge, pseudobranch, and antennae). Rediae occur mainly in the ovotestis and in tissues anterior to the liver. The first cercariae are released 24 days postexposure. Metacercariae encyst in various freshwater snails and are localized in the pericardial sac and the posterior part of the kidney. Adult worms live in the small intestine of a variety of experimental animals: hamsters, rats, mice, chicks, ducklings, pigeons, and finches.

Structure and mode of function of the organelles associated with nutrition of the macrogametes of Eimeria acervulina

The macrogamete of Eimeria acervulina, lay and developed within the host cell in a parasitophorous vacuole. The cytoplasmic membrane of the host cell bordering the vacuole was not smooth, but it had numerous folds extending into the vacuole. These "intravacuolar folds" varied in depth and number in different sections. In some, the majority of the folds were disconnected from the host cell. Once disconnected, they evidently disintegrated forming the amorphous, particulate material present in the parasitophorous vacuole. The pellicle of the young macrogamete consisted of a single unit membrane with an osmiophilic material representing the second membrane. Two unit membranes were apparent at a later stage of development when the wall-forming bodies had been formed and amylopectin granules deposited. Two kinds of organelles were present on the surface of the macrogamete, typical micropores and invaginations of the pellicle. The micropores arose from an invagination of the outer membrane, which continued through the invagination without interruption. Irrespective of whether an inner membrane was present in the pellicle or not, a thickened cylindrical wall around the inner portion of the invagination was always present. Micropores appeared in large numbers in both micro- and macrogametocytes. As many as three micropores were seen in a surface area of 2 mu2. Invaginations arose in a similar manner by infolding of the pellicle. They differed from micropores in that the thickened cylindrical wall present around the inner portion of the micropore was absent, and also in that invaginations had no uniform appearance. They were of varying shapes, and lengths, varying from very short V-shaped to long and narrow. Micropores and invaginations take in nutrients in the form of particulate matter present in the parasitophorous vacuole, this material having been derived from the host-cell membranous "intravacuolar folds". The micropores function as cytostomes and the invaginations take in material by means of pinocytosis. Large numbers of intravacuolar tubules were seen at the surface of the macrogamete. They were present only at certain areas of the macrogamete and in groups and were connecting the parasite with the host cell. They were about 80-110 nm in diameter, and were seen to attain a length of up to 6 mu. Evidence was obtained indicating that the tubules transport free ribosomes from the host cell to the parasite. The ribosomes were seen to accumulate in "pockets" within the cytoplasm of the host cell, at the area where the tubules were connected.

Acquired resistance to experimental Heterakis gallinarum infections in pheasants: relative immunity conferred by exposure to heterakids of different ages

Ring-necked pheasants were exposed to artificially limited 10-day infections with heterakids either from 0-10 or 10–20 days old. The number and length of worms developing from a subsequent challenge dose were compared with those in nonimmunized control birds and with those in birds that had been exposed to a continuous immunizing infection for a total of 49 days: 28 days before challenge and 21 days during the challenge infection.

[Refractoriness of hens towards Trypanosoma (Schizotrypanum) cruzi. III. Dissociation of phenomena of the refractory state and lysis of the epimastigotes by fowl serum]

Há muito tempo é sabido serem as aves refratárias ao "T. (S.) cruzi". Em trabalhos anteriores verificou-se que nas galinhas pode-se obter infecções "in ovo" diagnosticáveis até o 21º de incubação, porém, logo após o nascimento os pintos mostram-se refratários ao parasito, que é destruído no ponto de inoculação. Neste trabalho verificou-se que tripomastigotas injetados diretamente no sangue, podem ser esporadicamente encontrados até 1h depois. Verificou-se também que galinhas bursectomizadas, com associação de testosterona "in ovo" e ciclofosfamida nos 4 primeiros dias de vida permanecem refratárias. Entretanto, o soro dessas aves perde a capacidade lítica que o soro das aves normais possui para os epimastigotas do "T. (S.) cruzi", pela qual são responsáveis as gama-globulinas séricas, conforme foi verificado após o fracionamento do soro em coluna de DEAE-Sefádex A50. A dissociação dos 2 fenômenos, mostra que a capacidade lítica pode ser atribuída a um "anticorpo natural" - uma vez que é eliminada ou grandemente diminuída com a supressão do sistema imunitário bursa- dependente - porém, o mesmo não se pode concluir quanto à refratariedade. Esta, provavelmente, deve estar relacionada ao próprio metabolismo celular após o nascimento.

Pathogenic mechanisms not operating in Eimeria necatrix infections

Having investigated certain aspects of Eimeria necatrix coccidiosis in chickens, workers of the Hannover Veterinary School postulated "that death following a single inoculation of a large number of oocysts is due to an alarm reaction and not a specific pathogenic action of the parasites". Because this hypothesis is somewhat revolutionary in its consept, several pieces of evidence on which it is based and several logical deductions which can be made from it have been examined. It has been confirmed that injection of chichens with cysteamine or 5-hydroxytryptamine 30 min before inoculation of the birds with a lethal dose of E. necatrix oocysts reduces subsequent mortality; the reason for this, however, appears not to be the neutralisation of the proposed shock reaction, but rather an inhibition of the excystation process, brought about indirectly through the host. Inoculation of chickens with a non-lethal dose of E. necatrix oocysts 30 min before inoculation with a lethal dose of oocysts was followed by increased mortality rather than the decreased mortality which the hypothesis would predict. Treatment of chickens with sulphadimidine starting 48 h after inoculation resulted in survival of the birds rather than death which would ensue if in fact mortality was due to a shock reaction irreversibly initiated at the time of inoculation. A direct effect of sulphadimidine on the parasite has been shown both in vivo and in vitro.