Methylprednisolone acetate induces, and Δ7-dafachronic acid suppresses, Strongyloides stercoralis hyperinfection in NSG mice

Strongyloides stercoralis hyperinfection causes high mortality rates in humans, and, while hyperinfection can be induced by immunosuppressive glucocorticoids, the pathogenesis remains unknown. Since immunocompetent mice are resistant to infection with S. stercoralis, we hypothesized that NSG mice, which have a reduced innate immune response and lack adaptive immunity, would be susceptible to the infection and develop hyperinfection. Interestingly, despite the presence of large numbers of adult and first-stage larvae in S. stercoralis-infected NSG mice, no hyperinfection was observed even when the mice were treated with a monoclonal antibody to eliminate residual granulocyte activity. NSG mice were then infected with third-stage larvae and treated for 6 wk with methylprednisolone acetate (MPA), a synthetic glucocorticoid. MPA treatment of infected mice resulted in 50% mortality and caused a significant >10-fold increase in the number of parasitic female worms compared with infected untreated mice. In addition, autoinfective third-stage larvae, which initiate hyperinfection, were found in high numbers in MPA-treated, but not untreated, mice. Remarkably, treatment with Δ7-dafachronic acid, an agonist of the parasite nuclear receptor Ss-DAF-12, significantly reduced the worm burden in MPA-treated mice undergoing hyperinfection with S. stercoralis. Overall, this study provides a useful mouse model for S. stercoralis autoinfection and suggests a therapeutic strategy for treating lethal hyperinfection.

A brood parasite selects for its own egg traits

Many brood parasitic birds lay eggs that mimic their hosts' eggs in appearance. This typically arises from selection from discriminating hosts that reject eggs which differ from their own. However, selection on parasitic eggs may also arise from parasites themselves, because it should pay a laying parasitic female to detect and destroy another parasitic egg previously laid in the same host nest by a different female. In this study, I experimentally test the source of selection on greater honeyguide ( Indicator indicator ) egg size and shape, which is correlated with that of its several host species, all of which breed in dark holes. Its commonest host species did not discriminate against experimental eggs that differed from their own in size and shape, but laying female honeyguides preferentially punctured experimental eggs more than host or control eggs. This should improve offspring survival given that multiple parasitism by this species is common, and that honeyguide chicks kill all other nest occupants. Hence, selection on egg size in greater honeyguides parasitizing bee-eaters appears to be imposed not by host defences but by interference competition among parasites themselves.

Sperm storage in the uterium of the insect-parasitic nematode Sphaerularia vespae (Nematoda: Sphaerulariidae)

The spermatheca found in the ‘uterium’ (highly transformed part of parasitic female) of the sphaerularioidid nematode Sphaerularia vespae, an endoparasite of a common Japanese hornet, Vespa simillima, was studied with TEM. The uterium consists of a thick trophic epithelium exposed to the insect haemocoel and a protective cavity which contains the female genital tube and storage cells (fat body). The uterium cavity contains the female reproductive system composed of the usual parts: uterus, oviduct and ovary. The genital pore of the young uterium is an opening of the short narrow uterine tube which joins to the voluminous spermatheca. The spermatheca is a dilated distal part of the uterus, storing numerous tiny spermatozoa. The spermatheca is blocked distally by the oviduct. The spermatozoa are uniform amoeboid cells only 1.4-1.6 μm in size with a highly condensed nucleus about 0.8 μm in size. The transparent sperm cytoplasm contains several mitochondria, small membranous organelles (specific organelles characteristic of nematode spermatozoa), occasional bundles of fibres and centriole-like bodies. The S. vespae spermatozoa are very similar to the spermatozoa stored in the uterus of infective females of another sphaerularioidid nematode, Deladenus sp., and have the main features of sperm found in many other rhabditid nematodes.

Use of larval, parasitic female and egg antigens fromStrongyloides venezuelensisto detect parasite-specific IgG and immune complexes in immunodiagnosis of human strongyloidiasis

SUMMARYThe aim of this study was to use larval, parasitic female and egg antigens fromStrongyloides venezuelensisto detect parasite-specific IgG and immune complexes in human serum samples by enzyme-linked immunosorbent assay (ELISA). In total, 95 serum samples were analysed, consisting of 30 patients harbouringS. stercoralislarvae, 30 healthy subjects and 35 patients with other parasites. Sensitivity, specificity and diagnostic efficiency were calculated. A significant statistical difference was found in the detection of immune complexes and antibodies in patients harbouringS. stercoralislarvae from larval and eggs antigens, with higher positivity using larval antigen. The larval antigen showed the highest values for sensitivity, specificity and diagnostic efficiency in ELISA from detection of immune complexes. For the first time we used IgG anti-larvae, IgG anti-parasitic females or IgG anti-eggs for immune complex detection. We concluded that the association of antibody and immune complex detection could be used in the diagnosis of human strongyloidiasis.

Morphological and molecular characterization of Strongyloides ophidiae (Nematoda, Strongyloididae)

The aim of the present study is to report morphological data from parasitic female, rhabditoid and filarioid larvae, free-living female worms and eggs of Strongyloides ophidiae (Nematoda, Strongyloididae). In addition, a molecular DNA analysis was carried out using a pool of eight S. ophidiae parasitic females. Samples were obtained from the small intestine of Oxyrhopus guibei (Serpentes, Colubridae) collected in the municipality of Lençóis Paulista, State of São Paulo, Brazil. DNA amplification by polymerase chain reaction (PCR) resulted in a 350 bp band for samples containing S. ophidiae and Strongyloides venezuelensis DNA. Strongyloides ophidiae nucleotide sequence analysis showed 98% similarity with Strongyloides procyonis and 97% with Strongyloides cebus, Strongyloides stercoralis, Strongyloides fuelleborni and Strongyloides sp. from snakes.

Description of two new species of Iotonchium Cobb, 1920 (Tylenchida: Iotonchiidae) from Japan

Two new Iotonchium species are described from Japan. These species possesses four adult forms; mycetophagous female, infective female, male and insect-parasitic female. Iotonchium laccariae n. sp. is characterised by short body length of all adult forms, right-angled L-shaped spicule with beak-like distal arm, a pair of large papillae anterior to the cloacal opening, the dorso-ventrally flattened head of male and the reproductive features of the parasitic female. The mycetophagous females of I. laccariae n. sp. inhabit the fruiting bodies of four Laccaria spp. Males and infective females were also obtained from the fruiting bodies. The insect-parasitic females of I. laccariae n. sp. inhabit the haemocoel of a fungus gnat, Allodia laccariae. Iotonchium russulae n. sp. is characterised by the long body length of the infective female, parasitic female and mycetophagous female, obtuse-angled L-shaped spicule with dorsally curved slender distal arm, a pair of bifid postcloacal papillae, presence of a mid-ventral postcloacal papilla in the male and reproductive features of the parasitic female. The mycetophagous females, males and infective females of I. russulae n. sp. were obtained from the fruiting bodies of three Russula spp. and two Lactarius spp. The insect-parasitic females of I. russulae n. sp. inhabit the haemocoel of A. bipexa, a species of fungus gnat.

Secreted adhesion molecules of Strongyloides venezuelensis are produced by oesophageal glands and are components of the wall of tunnels constructed by adult worms in the host intestinal mucosa

The parasitic female of Strongyloides venezuelensis keeps invading the epithelial layer of the host intestinal mucosa. Upon invasion, it adheres to the surface of the intestinal epithelial cells with adhesion molecules secreted from the mouth. It has been demonstrated that S. venezuelensis are expelled from the intestine because mucosal mast cells inhibit the attachment of adult worms to the mucosal surface. In the present study, we generated specific antibodies against secreted adhesion molecules to investigate their function in vivo, because these molecules have been demonstrated only in vitro in spite of the importance in the infection processes. A mouse monoclonal antibody specific to S. venezuelensis adhesion molecules inhibited the attachment of adult worms to plastic dishes and the binding of adhesion molecules to rat intestinal epithelial cells. Immunohistochemical study revealed that adhesion molecules were produced by oesophageal glands and were continuously secreted in vivo to line the wall of the tunnels formed by adult worms in the intestinal mucosa. Our findings indicate that adhesion molecules play essential roles in the infection processes of S. venezuelensis in the host intestine.

A genetic analysis of reproduction in Strongyloides ratti

SUMMARYStrongyloides ratti has a complex life-cycle with two adult generations, one free-living and dioecious and one parasitic and female only. The parasitic females reproduce by parthenogenesis, but it is unclear whether this is mitotic or meiotic in nature. This question has been addressed genetically by analysing the progeny of parasitic females that were heterozygous at an actin locus for evidence of allelic segregation. Such progeny were similarly heterozygous showing that segregation had not occurred. It was therefore concluded that reproduction in the parasitic female of S. ratti is functionally mitotic.

Comment: Why is conspecific nest parasitism more frequent in waterfowl than in other birds?

Rohwer and Freeman (F. C. Rohwer and S. Freeman. 1989. Can. J. Zool. 67: 239–253) have suggested that conspecific nest parasitism is rare in species with parentally fed young because high costs to hosts result in strong selection for defenses against parasitism. In contrast, conspecific nest parasitism is frequent in waterfowl and other species with self-feeding young because the costs of parasitism to hosts are minimal and produce little selection for host defenses. I offer several criticisms of this hypothesis and suggest that variation in the rate of conspecific nest parasitism among birds is better understood by focusing on the costs and benefits of parasitism for the parasitic female. I suggest that conspecific nest parasitism is more successful and therefore more frequent in waterfowl species because parasitic eggs and young require no more parental care from the host than it is already providing to its own offspring. In contrast, parasitism is less successful and less frequent in species with parentally fed young because parasitic young require additional care that hosts may not be capable of providing.

The ultrastructure of the peri-vulval region of Strongyloides cebus

ABSTRACTUltrastructural studies were undertaken on a discrete peri-vulval area of cuticular modification in the parasitic female of Strongyloides cebus. Cilium-like arrangements of microtubules were observed which suggested that this region was sensory in nature. The possible function of this is discussed.