SEM studies on Trichurus muris from Psammomys obessus from Sinai Peninsula, Egypt

The whipworm Trichuris muris was recovered from the caecum of the wild rodent Psammomys obessus trapped from Sinai Peninsula, Egypt. The cuticular surface ultrastructure is described using SEM. T. muris is closely related to other Trichuris species but can be distinguished from them mainly by differences in the posterior end of males. Details of the surface such as the bacillary gland, cuticular inflations and several morphological details obtained by scanning electron microscopy confirmed the characteristics that differentiate the species. P. obessus (Cretzschmar, 1828) is considered a new host record and Sinai is considered a new locality for the genus. This may through light on the spread of T. muris between Asia and Africa.

What are the infectious larvae in Ascaris suum and Trichuris muris?

In the present study, larvae of Ascaris suum and Trichuris muris were investigated by light and electron microscopy after incubation in a hatching medium containing 89% phosphate-buffered saline (pH 7.4), 10% RPMI-1640 and 1% sodiumhypochlorite at 40 and 37 degrees C, respectively. The larvae were obtained from fertilised eggs of the worms during defined phases of development (A. suum, 36th-50th day of development; T. muris, once a week from week 16 to 20). Light and electron micrographs of the larvae gave evidence that the third larval stage of A. suum is probably the infectious stage. The first moult of the larvae had already taken place before the 36th day of incubation starting at day 1. After 36 days of incubation, only the second larval stage was found within eggs. Some of these larvae were coated by a separated sheath so that a second moult of the larvae is reasonable. On the other hand, no sheathed larvae of T. muris were found in the eggs incubated for 20 weeks in distilled water. No signs of moult were seen for 20 weeks neither on light nor on the electron micrographs. Therefore, in T. muris, the first larval stage is the infectious stage, which was proven by means of re-infections of mice 16, 18 or 20 weeks after incubation of the eggs.

Light and electron microscopic studies on two nematodes, Angiostrongylus cantonensis and Trichuris muris, differing in their mode of nutrition

The morphological characteristics of the adult heteroxenous blood nematode Angiostrongylus cantonensis and the adult monoxenous intestinal nematode Trichuris muris were compared with special regard to the ultrastructure of their digestive systems. The small circular mouth of A. cantonensis appears sucker like. The very narrow mouth of T. muris is surrounded by three lips covered by the cuticle that extends into the buccal space. In the buccal cavity of A. cantonensis, a single tooth occurs opposite to a cutting plate, while no teeth are present in T. muris. The lumen of the well-developed muscular pharynx of A. cantonensis shows a trifurcated star-like cross-section. The anterior segment of the bipartite pharynx presumably functions as a pump. The lumen of the bipartite pharynx and esophagus of T. muris exhibits a very narrow oval cross-section and possesses no musculature. It is composed of a long column of stichosome cells. The esophagus region is lined inside by bands of bacillary cells as well as outside by two longitudinal rows of funnel-like papillae. These structures may be involved in the uptake of nutrients by T. muris. The gland cells might excrete digestive exoenzymes, while the bacillary cells take up the predigested nutrients. The presence of many vesicles suggests a vesicular transport of the material into the pharynx. The intestinal epithelium of A. cantonensis is densely covered with short microvilli. The lumen itself is filled with red blood cells originating from host blood. The intestine of T. muris has a thick epithelium being placed on a basal lamina and shows long thin microvilli. The intestinal lumen is very narrow and free from particles or granules. This again suggests that T. muris lives on low molecular nutrients resorbed from the environment. The epithelium cells of the intestine of T. muris contain glycogen and electron light granules but are lacking mitochondria. This finding may indicate that the epithelium cells have an anaerobic energy metabolism. This statement fits with the fact that the habitat of the worm, the cecum, is largely anaerobic.

New weapons in the war on worms: identification of putative mechanisms of immune-mediated expulsion of gastrointestinal nematodes

Parasitic nematode infections of humans and livestock continue to impose a significant public health and economic burden worldwide. Murine models of intestinal nematode infection have proved to be relevant and tractable systems to define the cellular and molecular basis of how the host immune system regulates resistance and susceptibility to infection. While susceptibility to chronic infection is propagated by T helper cell type 1 cytokine responses (characterised by production of IL-12, IL-18 and interferon-gamma), immunity to intestinal-dwelling adult nematode worms is critically dependent on a type 2 cytokine response (controlled by CD4+T helper type 2 cells that secrete the cytokines IL-4, IL-5, IL-9 and IL-13). However, the immune effector mechanisms elicited by type 2 cytokines in the gut microenvironment that precipitate worm expulsion have remained elusive. This review focuses on new studies that implicate host intestinal epithelial cells as one of the dominant immune effector cells against this group of pathogens. Specifically, three recently identified type 2 cytokine-dependent pathways that could offer insights into the mechanisms of expulsion of parasitic nematodes will be discussed: (i) the intelectins, a new family of galactose-binding lectins implicated in innate immunity, (ii) the resistin-like molecules, a family of small cysteine-rich proteins expressed by multiple cell types, and (iii) cytokine regulation of intestinal epithelial cell turnover. Identifying how the mammalian immune response fights gastrointestinal nematode infections is providing new insights into host protective immunity. Harnessing these discoveries, coupled with identifying what the targets of these responses are within parasitic nematodes, offers promise in the design of a new generation of anti-parasitic drugs and vaccines.

In vitro and in vivo anthelmintic efficacy of plant cysteine proteinases against the rodent gastrointestinal nematode, Trichuris muris

Extracts of plants, such as papaya, pineapple and fig, are known to be effective at killing intestinal nematodes that inhabit anterior sites in the small intestine, such as Heligmosomoides polygyrus. In this paper, we demonstrate that similar in vitro efficacy also occurs against a rodent nematode of the large intestine, Trichuris muris, and confirm that the cysteine proteinases present in the plant extracts are the active principles. The mechanism of action of these enzymes involved an attack on the structural proteins of the nematode cuticle, which was similar to that observed with H. polygyrus. However, not all plant cysteine proteinases were equally efficacious because actinidain, from the juice of kiwi fruit, had no detrimental effect on either the motility of the worms or the nematode cuticle. Papaya latex was also shown to significantly reduce both worm burden and egg output of mice infected with adult T. muris, demonstrating that enzyme activity survived passage to the caecum and was not completely inactivated by the acidity of the host's stomach or destroyed by the gastric or pancreatic proteinases. Thus, the cysteine proteinases from plants may be a much-needed alternative to currently available anthelmintic drugs due to their efficacy and novel mode of action against different gastrointestinal nematode species.

A NEW SPECIES OF TRICHURIS (NEMATODA: TRICHURIDAE) FROM PHYLLOTINI RODENTS IN ARGENTINA

A new species of Trichuris is described. Trichuris pardinasi n. sp. was recovered from Phyllotis xanthopygus Waterhouse (Rodentia: Muridae: Phyllotini) in Sierra de la Ventana, Buenos Aires Province, and Pampa de Achala, Córdoba Province (Argentina). This is the first record of Trichuris parasitizing Phyllotini rodents. The new species can be differentiated from the other 10 species parasitizing rodents from South America by the absence of the spicular tube, spicular sheath with spines uniformly distributed, the length of spicule, the J-shaped proximal cloacal tube, and the nonprotrusive vulva. Also, a description of the bacillary band is provided. The present and the future findings of shared parasite fauna from both populations of P. xanthopygus in these disjunct areas will support the hypothesis of a continuous distribution of this host species at a past time.

Adaptation of a nematode parasite to living within the mammalian epithelium

Trichuris muris is a large metazoan pathogen that has been proposed to live intracellularly within living host intestinal epithelial cells. We sought to determine how Trichuris bores its way through the mucosal epithelium and to elucidate the parasite strategies for taking advantage of this intracellular niche. Since the apical surface of the mucosal epithelium is stabilized by the actin cytoskeleton and cell junctions, it remains intact over the worm following its entry into cells. In contrast, non-stabilized lateral membranes of the host epithelial cells are ruptured and cells are killed to form an inert syncytial tunnel. The ventral surface of the nematode worm is studded by pores that overlie bacillary cells; these pores penetrate through the cuticle and are in direct contact with host cytoplasm. From scanning electron micrographs of isolated worms, we calculate that each adult contains approximately 50,000 bacillary cells. The apical surface of the bacillary cells is extensively folded into plicae 40 nm in diameter, thereby increasing the surface area many-fold. Bacillary cells lack organelles for enzyme synthesis and secretion and fail to export protons. However, by confocal light microscopy it was observed that fluorescent macromolecules in excess of 100,000 Da can penetrate into the pores. Taken together, we conclude that the bacillary cells are essential for living inside host epithelium and function predominantly in absorption of soluble molecules from the host mucosal cytoplasm, in essence behaving as an external gut epithelium that is protected from abrasion by the cuticle that surrounds the openings of the bacillary cells.

Scanning electron microscopy of Trichuris trichura

Scanning electron microscopy (SEM) studies have been carried out on adult and ova of T. trichura to provide the additional topographical details which are not obtainable by the light microscopy. The egg of T. trichura has a chitinous shell which consists of layers of dense lamellae and bordered by a limiting membrane. An operculum and a collar made of chitin form the opercular area. The lamallae of the egg shell are diffuse with numerous micropores. Cuticular pores are found scattering on the surface of the adult T. trichuira. The spicule sheath in male is cylindrical and covered with spines of different shape, size and distribution along its length. Spines are compact proximally, reduced in number on the middle part and lacking distally. SEM of the cloacal part showed paracloacal papillae.

[Scanning electron microscopy of adult Trichuris trichiura]

The paper reports the result of the observation on the ultrastructure of the body surface of adult T. trichiura by scanning electron microscopy. Unique features of T. trichiura are described including the presence of labial-shape structures at the periphery of mouth, eight cephalic pores and a pair of amphids around the mouth pore and vesicle-shaped cuticular protuberances on the abdomen of T. trichiura. Cuticular pores were found scattering on the surface of T. trichiura. Detailed descriptions of male copulatory sheath and spicule were presented.

Comparative study of Trichuris trichiura from non-human primates and from man, and their difference with T. suis

Whipworms from the macaque and baboon were studied by light and scanning electron microscopy. They were identified as Trichuris trichiura, though a slight variation was observed in the length of spicule as compared with the whipworms collected from man. Moreover, a row of small knob-like structures was observed at the base of the pericloacal papillae of T. trichiura from the monkey by scanning electron microscopy. T. trichiura from non-human primates and man has been reported to be morphologically indistinguishable from T. suis. However, this study showed that males of T. trichiura from both the monkey and man can be differentiated from T. suis from the pig on the basis of the presence of a pair of pericloacal papillae and a cluster of small papillae near the caudal end in the former, which is totally absent in the latter.

Description of Trichuris travassosi n. sp. (Nematoda:Trichurinae) from a brasilian rodent, by light and scanning electron microscopy

A new species of a trichurid nematode Trichuris travassosi n. sp., recovered from a wild rodent in the State of Rio Grande do Sul, Brazil, is described and compared to T. myocastoris (Enigk, 1933) and their differentiation was on the basis of a detailed morphometrical study. Oryzomys nigripes (Olfers, 1818) is a new host record for the genus. The denomination spicular prepuce is proposed to designate the structure previously named spicular sheath and, conversely, spicular sheath to indicate the cuticle that covers the spicule.

The structure of the shell and polar plugs of the egg of the whipworm, Trichuris trichiura (Nematoda: Trichuridae) from the Samango monkey (Cercopithecus albogularis)

The structure of the shell of the egg of Trichuris trichiura was examined using light microscopy as well as scanning and transmission electron microscopy. The results confirmed its three-layered structure and provided evidence that the cores of the polar plugs, which could be seen to be extensions of the shell's middle layer, could be lost en bloc, either mechanically or chemically, and in this way probably provided an exit for the first stage larva at hatching.

Scanning electron microscopy of Trichuris trichiura (Nematoda)

Trichuris trichiura was examined in the scanning electron microscope and revealed a double row of sucker-like structures at the anterior part. It is postulated that they may support the attachment of the worm in host tissues. The sheath of the spicule is covered with spikes and the vulval opening is surrounded by an elevated rim-like structure with indentations.

The morphology of the attachment and probable feeding site of the nematode Trichuris muris (Schrank, 1788) Hall, 1916

The 'tunnel' within which the nematode Trichuris muris is contained was examined by light, scanning, and transmission electron microscopy. The amount of worm covered by the tunnel varied with age. Young larval worms were completely embedded in the host's intestinal mucosa whereas older larvae and adults had part, if not all, of the posterior region protruding into the lumen. All worms were found to have heads embedded in the tissue and in no cases were whole worms found free in the lumen.The 'tunnel' was shown to be a syncytial protoplasmic mass with recognizable cellular elements such as nuclei, lipid droplets, mitrochondria, and mucous droplets anteriorly whereas more distal to the head these elements became increasingly scarce and degenerated. The syncytium is bordered apically, laterally, and basally by cell membrane. The basal lamina can be identified beneath the basal membrane of the syncytium indicating that syncytium formation occurs in the epithelial sheet only and does not extend into the lamina propria. Evidence suggests that the nematode initially induces a syncytium about its head, feeds on the syncytial cytoplasm, and then moves on to initiate extension of the syncytium. The result of this movement is a 'tunnel' snaking across the caecum and colon.

Structure and function of the male copulatory apparatus of the nematodes Capillaria hepatica and Trichuris muris

The anatomy of the terminal male reproductive system was studied by light microscopy and by scanning and transmission electron microscopy. In C. hepatica a common muscle sphincter surrounds the vas deferens and intestine at their point of juncture. The cloaca is divisible into proximal and distal portions. The spicule is formed in a short ventral spicule pouch but lies mainly in the distal cloaca. The spicule is retracted in C. hepatica by a paired retractor muscle and in T. muris by a single retractor muscle. Protraction of the spicule occurs by contraction of longitudinal muscles surrounding the distal cloaca. This results in the surface layers of the cloacal cuticle being everted as the spicule sheath. The spicule is tubular with a cellular core including multiple sensory receptors at its tip. The spicule is probably solely a chemosensory organ. Mechanical stimulation in the region of the distal cloaca resulted in activation of the spicule and spicule sheath. Response to mechanical stimulus is age dependent.

Pathophysiology of swine trichuriasis

Infection of pigs by the whipworm (Trichuris suis) resulted in profuse diarrhea on postinfection days 17 to 21. Anorexia, retardation of growth, dehydration, and emaciation were observed in infected pigs. Scanning electron micrography showed nematodes embedded in the mucosa of the cecum and colon, with resultant disruption of the mucosa. Infected pigs had decreased values of albumin, amylase, calcium and creatine phosphokinase, but increased values of alpha-, beta-, and gamma- globulins, total iron-binding capacity, copper, potassium, uric acid, and aspartate aminotransferase.