Worm Life Research Articles

Imaging of Ascaris lumbricoides in the common bile duct and small intestine

Dear Editor, In the western world, Ascaris lumbricoides A. lumbricoides) or roundworm infestation is uncommon. It usually involves the small bowel and is diagnosed by stool examination. It is unusual to make the initial diagnosis by imaging. The detection of mobile worms within the common bile duct (CBD) on ultrasound is extremely rare. A 32-year-old male presented with a three-month history of abdominal pain and weight loss. Clinical examination was unremarkable. Abnormal laboratory findings included a mild hypochromic microcytic anaemia and mildly elevated liver function tests. A small bowel follow-through showed multiple linear filling defects in the jejunal loops in keeping with Ascaris (roundworm) infestation (see Figure 1) and barium was seen in the alimentary canal of the worm. J An upper abdominal ultrasound showed a linear echogenic luminal abnormality in the CBD suggestive of a worm (see Figure 2) . Dynamic imaging revealed antegrade movement of the worm within the bile duct. A computer tomography (CT) scan of the abdomen revealed no other cause for the biliary obstruction. It also revealed worms within the small bowel giving a `target'-like appearance (see Figure 3). An endoscopic retrograde cholangiopancreatography (ERCP) confirmed the presence of Ascaris in the CBD (see Figure 4). The offending worm was removed and the patient was treated with oral antihelminthic medication and made an uneventful recovery. A. lumbricoides typically measures about 25-35cm in length. The average worm's life span is approximately one year. The disease is more common in children under 10 years of age. The incidence varies significantly with some groups having an incidence of up to 12%;. It is found world-wide but is particularly common in poor and rural communities due to heavy faecal contamination of the immediate environment. Infection may be asymptomatic or be associated with nausea, vomiting, abdominal discomfort and anorexia. Worms may obstruct the small intestine with the most common site being the ileo-caecal valve. Occasionally they may extend into the appendix causing acute appendicitis. When Ascaris migrates from the duodenum through the ampulla of Vater to the CBD, patients may present with abdominal pain and jaundice.' Obstruction may occasionally lead to suppurative cholangitis with rigors and fever.' Mebendazole 100mg twice daily for three days is the treatment of choice but surgical or endoscopic intervention may be required for intestinal or biliary obstruction.

CLK-1 protein has DNA binding activity specific to O L region of mitochondrial DNA

Mutations in the clk-1 gene of Caenorhabditis elegans extend worm life span and slow down a variety of physiological processes. Here we report that C. elegans CLK-1 as well as its mouse homologue have DNA binding activity that is specific to the O L region of mitochondrial DNA. DNA binding activity of CLK-1 is inhibited by ADP, and is altered by mutations that extend nematode life span. Our results suggest that, in addition to its enzymatic function in ubiquinone biosynthesis, CLK-1 is involved in the regulation of mtDNA replication or transcription.

Selection of different genotype larvae and adult worms for anthelmintic resistance by persistent and short-acting avermectin/milbemycins

To understand the factors that influence selection for anthelmintic resistance, it is necessary to examine the impact of drug treatment, particularly persistent drugs, on all phases of the worm life cycle. The efficacy of various avermectin/milbemycin anthelmintics was determined against resident worms, incoming larvae (L3) and development of eggs in faecal culture. Homozygote-resistant and maternal and paternal F1-heterozygote genotypes of Haemonchus contortus were used to infect sheep before or after treatment with ivermectin (IVM) oral, IVM capsule, moxidectin (MOX) oral or MOX injectable. Total worm count and quantitative larval culture were used to determine efficacy against parasitic and free-living stages, respectively. Selection for resistance by IVM capsules occurred at the adult and L3 stages because of poor efficacy against these stages for all resistant genotypes. However, the selective advantage of these surviving worms was reduced due to the low development of their eggs to L3 in faecal culture. For MOX, selection for resistance predominantly occurred after treatment because of high efficacy against resident adult worms of all resistant genotypes but poor efficacy against resistant L3 ingested after drug administration. The results indicated no evidence of sex-linked inheritance for IVM resistance. Mean IVM efficacies against homozygous and heterozygous resistant adult worms were not different, and IVM capsule efficacy against incoming L3 was approximately 70% for all resistant genotypes, consistent with a dominant trait. MOX was highly effective against adults of all resistant genotypes and approximately 76% effective against incoming L3 regardless of resistance genotype, also consistent with a dominant trait. These results will enable the impact of persistent drugs on worm control and anthelmintic resistance to be estimated. The results indicate that IVM capsules should not be used in populations where avermectin/milbemycin resistance is present.

Multiple Genes for Vacuolar-type ATPase Proteolipids inCaenorhabditis elegans: A NEW GENE, vha-3, HAS A DISTINCT CELL-SPECIFIC DISTRIBUTION

In the vacuolar-type H+-ATPase (V-ATPase), highly hydrophobic subunits known as the proteolipids are components of the integral membrane V0 sector. Previously, we described the identification of three different proteolipid genes in Caenorhabditis elegans (Oka, T., Yamamoto, R., and Futai, M. (1997) J. Biol. Chem. 272, 24387-24392): vha-1 and vha-2 encoded 16-kDa subunits, and vha-4, a 23-kDa isoform. We report here that a third 16-kDa gene, vha-3, has been identified on chromosome IV. This is the first example in which four proteolipid genes have been found in a single organism. vha-2 and vha-3 exhibited 85% nucleotide identity within the open reading frames which encoded the identical amino acid sequence. Northern blot analysis indicated that all four genes were expressed in a similar pattern during the worm life cycle; however, studies with transgenic worms indicated that the vha-3 gene was expressed differently from other proteolipid genes in a cell-specific manner. These results implied that the isoforms of the proteolipids may be related to functional differences of V-ATPases in various cell types. Another new gene, vha-11, contained seven exons and was found to be located immediately downstream of vha-3. The two genes constitute a single transcriptional unit. The VHA-11 protein had 384 amino acids and shared strong sequence similarities with the C subunit, a component of the peripheral V1 sector of the V-ATPase, from yeast, bovine, and human. Expression of the vha-11 cDNA complemented a null mutation of VMA5, the yeast C subunit gene, thus demonstrating that vha-11 was the functional C subunit of C. elegans.

The importance of worm identity and life history in determining the vertical distribution of tubificids (Oligochaeta) in a riverine mud

The vertical distribution of Tubifex tubifex, Limnodrilus hoffmeisteri and L. udekemianus, in a riverine mud was studied over a year. Distribution was dependent upon species identity, season and locality. The size structure of the population, and hence species life history, was of fundamental importance in determining temporal patterns of vertical distribution. A positive correlation between worm length and depth of penetration was clearly demonstrated for all three species. However, the mid-stream populations of the three species were closer to the mud surface during the summer and autumn than were the near-bank populations, although the size structures of the populations were not significantly different. Thus, another factor, possibly the distribution of food, also influenced the vertical distribution of the worms. Cocoon distribution was similar to that of the adult worms. Cocoons of the larger species, L. udekemianus, occurred deeper in the mud than those of T. tubifex. A comparison between the vertical distributions of tubificids in cores sectioned in situ, on the stream bank, and 30 mins later, showed there to be no significant change in distribution with time.

Intra‐specific variability of the morphology in a single population of the seal parasite Contracaecum osculatum (Rudolphi) (Nematoda, Ascaridoidea), with a redescription of the species

Contracaecum spp. are common parasites of seals and piscivorous birds. The world‐wide distribution which has been attributed to the species C. osculatum needs verification. In the present study thc intra‐specific variability of some taxonomically significant characters was studied in this species. Features analysed include the length and morphology of the distal end of the spicules, the number of proximal caudal papillae and the number of papillae in the region of the first 25 cuticular transverse striae anterior to the cloaca, delined as the Pts zone (precloacal transverse striae zone). The spicules reach their maximum length only in fully grown worms. while the morphology of the distal end of the spicule is determined early in the life of adult male worms. Included is a detailed analysis of the observed morphometric variability in the distal end of the spicule. The number of cuticular transverse striae in relation to papillae in the Pts zone remains constant in different length classes of the parasite. A redescription of the parasite is provided, bascd on material obtained from grey seals in the Baltic Sea, to serve as a basis for discussions on the taxonomy of the genus.

Formation and diagenesis of Visean trace fossils from Ireland

Tube-like trace fossils occur within dolomitised Visean pelmicrites in County Fermanagh, Northern Ireland. The pelmicrites are associated with algal laminated carbonates and evaporites which imply deposition in a coastal sabkha. The tubes exhibit a preferred orientation caused by minor current systems. Thin sections and scanning electron micrographs show that in life the tubes were characteristically bilaminar, with an internal sheath of organic material and an organically cemented tube wall. This structure resembles that of modern polychaete worms. Comparison with a Bahaman polychaete suggests that the Visean worms inhabited a subtidal algal mat. The diagenetic history of the tubes is one of progressive dolomitisation and is closely linked to the presence of organic substances in the walls of the tubes and the mucus sheath which lined the tubes during the worm's life. The presence of the organic matter may have been a prerequisite for the formation of the dolomite observed in the tubes. Ichnofossils, diagenesis, dolomitisation, sabkha environment, Polychaeta, algal mats. Carboniferous, Visean, Northern Ireland, Fermanagh.

Effects of host endocrine gland removal on the permissive status of laboratory rodents to infection by Schistosoma mansoni

Knopf P. M. and Soliman M. 1980. Effects of host endocrine gland removal on the permissive status of laboratory rodents to infection by Schistosoma mansoni. International Journal for Parasitology, 10: 197–204. The capacity of Schistosoma mansoni to complete its life cycle was compared in CD-1 mice (permissive hosts) and Sprague-Dawley rats (nonpermissive hosts) from which the pituitary gland had been removed prior to infection with cercariae. Except for a modest decrease in egg burden, none of the parameters of worm life cycle assessed were affected in hypophysectomized mice. In contrast, all these parameters were affected in hypophysectomized rats, e.g. onset of adult worm elimination was delayed, worm development improved, oviposition increased and miracidia developed. Effects of removal from rats of the thyroid/parathyroid glands on the parasite life cycle were similar to hypophysectomy; adrenalectomy or gonadectomy were without affect. Differences between thyroidectomized and thymectomized rats are discussed. It is concluded that host hormones contribute to the nonpermissive status of rats to Schistosoma mansoni infections.

Syphacia muris, the Rat Pinworm

A migration of gravid Syphacia muris pinworms down the large intestine of the rat host is shown to occur from the seventh day on in the worm's life cycle. Eggs obtained from migrating worms have proved to be infective to helminth-free rats after incubation in saline for 30 minutes at room temperature and 4 hours at 37 degrees C.

Syphacia muris , the Rat Pinworm

A migration of gravid Syphacia muris pinworms down the large intestine of the rat host is shown to occur from the seventh day on in the worm's life cycle. Eggs obtained from migrating worms have proved to be infective to helminth-free rats after incubation in saline for 30 minutes at room temperature and 4 hours at 37°C.