[The genus Nippostrongylus Lane, 1923 (Nematoda-Heligmosomatidae)]

Two new genera and species of Nippostrongylinae (Nematoda: Heligmonellidae) parasites of two murine rodents (Muridae): from the Moluccas, Indonesia and Papua New Guinea with a comment on a pentastomatid

Bisastrongylus multiovorum gen. nov., sp. nov. (Nematoda: Heligmonellidae: Nippostrongylinae) is described from a murid, Melomys obiensis, from the Moluccas, Indonesia. The new genus differs from all other Nippostrongylinae genera in having a synlophe of 12 unequal ridges with a type A carene, the dorsal ridge 1 being larger than the ventral ridge 1'. Pentastomid larvae, an acanthocephalan, Plagiorhynchus sp., and the nematodes Rictularia sp., a spirurid and the nippostrongylin Soricstrongylus obreensis gen. nov., sp. nov. were collected from the murid Pseudohydromys murinus from Central Province, Papua New Guinea. The new genus is distinguished by a combination of characters including a synlophe of 11-13 ridges at mid body, left ventral ridges larger and a sub frontal axis of orientation. The assemblage of P. murinus is discussed and a re-evaluation of nippostrongylin Odilia sp., previously reported from P. murinus indicates that the specimens were likely a Parasabanema sp.

Population genetics, community of parasites, and resistance to rodenticides in an urban brown rat (Rattus norvegicus) population

Brown rats are one of the most widespread urban species worldwide. Despite the nuisances they induce and their potential role as a zoonotic reservoir, knowledge on urban rat populations remains scarce. The main purpose of this study was to characterize an urban brown rat population from Chanteraines park (Hauts-de-Seine, France), with regards to haematology, population genetics, immunogenic diversity, resistance to anticoagulant rodenticides, and community of parasites. Haematological parameters were measured. Population genetics was investigated using 13 unlinked microsatellite loci. Immunogenic diversity was assessed for Mhc-Drb. Frequency of the Y139F mutation (conferring resistance to rodenticides) and two linked microsatellites were studied, concurrently with the presence of anticoagulant residues in the liver. Combination of microscopy and molecular methods were used to investigate the occurrence of 25 parasites. Statistical approaches were used to explore multiple parasite relationships and model parasite occurrence. Eighty-six rats were caught. The first haematological data for a wild urban R. norvegicus population was reported. Genetic results suggested high genetic diversity and connectivity between Chanteraines rats and surrounding population(s). We found a high prevalence (55.8%) of the mutation Y139F and presence of rodenticide residues in 47.7% of the sampled individuals. The parasite species richness was high (16). Seven potential zoonotic pathogens were identified, together with a surprisingly high diversity of Leptospira species (4). Chanteraines rat population is not closed, allowing gene flow and making eradication programs challenging, particularly because rodenticide resistance is highly prevalent. Parasitological results showed that co-infection is more a rule than an exception. Furthermore, the presence of several potential zoonotic pathogens, of which four Leptospira species, in this urban rat population raised its role in the maintenance and spread of these pathogens. Our findings should stimulate future discussions about the development of a long-term rat-control management program in Chanteraines urban park.

Helminths from introduced small mammals on Kerguelen, Crozet, and Amsterdam Islands (southern Indian Ocean)

Four monoxenous nematodes and 1 heteroxenous cestode were found in 4 species of introduced small mammals on isolated sub-Antarctic islands of the Indian Ocean. In the Kerguelen Archipelago, Syphacia obvelata, Passalurus ambiguus (Nematoda: Oxyuridae), and Rodentolepis straminea (Cestoda: Cyclophyllidae) were respectively found in the house mouse Mus musculus, the rabbit Oryctolagus cuniculus, and the black rat Rattus rattus. One accidental nematode, Trichostrongylus sp. (Nematoda: Trichostrongylidae), was also found in a black rat on Kerguelen. On Possession Island (Crozet Archipelago), R. straminea was present in the black rat. On Amsterdam Island, the brown rat R. norvegicus harbored 2 species, R. straminea and Nippostrongylus brasiliensis (Nematoda: Heligmonellidae). The small number of founder hosts and the depauperate terrestrial communities on these remote islands explain the low diversity in the helminth communities of these introduced mammals compared with continental populations.

Phylogeny, host-parasite relationship and zoogeography

Phylogeny is the evolutionary history of a group or the lineage of organisms and is reconstructed based on morphological, molecular and other characteristics. The genealogical relationship of a group of taxa is often expressed as a phylogenetic tree. The difficulty in categorizing the phylogeny is mainly due to the existence of frequent homoplasies that deceive observers. At the present time, cladistic analysis is believed to be one of the most effective methods of reconstructing a phylogenetic tree. Excellent computer program software for phylogenetic analysis is available. As an example, cladistic analysis was applied for nematode genera of the family Acuariidae, and the phylogenetic tree formed was compared with the system used currently. Nematodes in the genera Nippostrongylus and Heligmonoides were also analyzed, and the validity of the reconstructed phylogenetic trees was observed from a zoogeographical point of view. Some of the theories of parasite evolution were briefly reviewed as well. Coevolution of parasites and humans was discussed with special reference to the evolutionary relationship between Enterobius and primates.

Microtopography of Nippostrongylus brasiliensis (Nematoda: Heligmosomatidae): parasitic larval stages and adults

Specimens of the rat hookworm, Nippostrongylus brasiliensis (Nematoda) were recovered from lungs (third- and fourth-stage larvae) and intestine (fourth-stage larvae and adults). The following features were studied in the different stages by scanning electron microscopy: cephalic structures, especially sense organs, synlophe, cervical region, and caudal part. The main differences between the third and fourth stages concerned the lip-like structures around the oral aperture, the appearance of the cephalic space with the presence of a cephalic cap in fourth-stage larvae, the pattern of longitudinal ridges, and sexual differentiation. Pore-like papillae, not seen in third-stage larvae, developed in later stages. Deirids were observed only in adults, and phasmids were poorly discerned. Some of these morphological features, such as the cephalic sense organ apertures and cuticle pores and micropores, can be observed only by scanning electron microscopy. The possible functions of these different structures and their relationship with the behavior of the worms during their life cycle are discussed.

Microtopography of Nippostrongylus brasiliensis (Nematoda: Heligmosomatidae): free-living larval stages

Microtopographic features of the various growth stages of the three free-living larval stages of the rat hookworm Nippostrongylus brasiliensis (Nematoda) were surveyed by scanning electron microscopy. These worms have a rounded anterior end and an elongated tail. Cuticular annulations were observed along the body, which also bore two ribbon-like lateral alae. Two rings of six lip-like lappets were observed around the triradiate oral opening in all larval stages. The cephalic space contained two lateral amphidial pits. The excretory pore in the third anterior part was observed in a ventral view of the larvae. No deirids were observed. The anus with a crescent-shape opening was located posteriorly. Phasmidial apertures, only observed in the third-stage larvae, opened on the lateral alae in the tail region.