Helminths parasitizing larval fish from Pantanal, Brazil

Fish larvae of 'corvinas' (Pachyurus bonariensis and Plagioscion ternetzi) from Sinhá Mariana Lagoon, Mato Grosso State, were collected from March 2000 to March 2004, in order to determine the parasitic fauna of fishes. Larvae from the two species were parasitized by the same endoparasites: Contracaecum sp. Type 2 (larvae) (Nematoda: Anisakidae) in the mesentery and Neoechinorhynchus (Neoechinorhynchus) paraguayensis (Acanthocephala: Neoechinorhynchidae) in the stomach and the terminal portion of the intestine. Statistical analysis showed that there was a significant positive correlation between the standard length of hosts and the abundance of acanthocephalans and nematodes, and that the prevalence of nematodes presented a significant positive correlation with the standard length of the two species of hosts, indicating the presence of a cumulative process of infection. The present study constitutes the first record of nematodes and acanthocephalans parasitizing larval fish, as well as the first record of endoparasites in fish larvae in Brazil. In addition, it lists a new locality and two species of hosts for Contracaecum sp. Type 2 (larva) and N. (N.) paraguayensis.     

Helminths of the horned leaf frog, Proceratophrys appendiculata, from southeastern Brazil

The helminth fauna of the horned leaf frog, Proceratophrys appendiculata (Anura: Leptodactylidae), was studied from 17 adult individuals from an island in Rio de Janeiro state, southeastern Brazil. A total of five nematode species (Aplectana delirae, Cosmocerca brasiliense, Schulzia travassosi, Rhabdias androgyna and Physaloptera sp.) and an unidentified cestode were recovered from the digestive tract, lungs and gall bladder of P. appendiculata and all the nematode species are new host records. Aplectana delirae had the highest values for the prevalence and intensity of infection and can thus be considered a core species in the helminth community of P. appendiculata. Aplectana crossodactyli Baker, 1980 is synonymized with Aplectana delirae (Fabio, 1971). The helminth fauna of P. appendiculata presents characteristics typical of those in amphibians.     

Helminths of the Virginia opossum Didelphis virginiana (Mammalia: Didelphidae) in Mexico

The goal of this study was to provide further information about helminth parasites of Virginia opossum Didelphis virginiana Kerr, 1792 from Mexico. During routine faunal investigations between 1958 and 2001, 101 opossum were necropsied. Nineteen taxa of helminths were collected, representing 13 genera from hosts in 27 localities from Mexico. There are 58 new locality records, with 6 species recorded in Mexico for the first time: Brachylaima virginiana Dickerson, 1930; Cruzia americana Mapleston, 1930; Didelphonema longispiculata (Hill, 1939); Didelphostrongylus hayesi Prestwood, 1976; Viannaia didelphis Travassos, 1914; and Viannaia viannai Travassos, 1914. This increases the number of helminth taxa previously known for this host in Mexico to 28.     

Helminths of the exotic lizard Hemidactylus mabouia from a rock outcrop area in southeastern Brazil

The helminth fauna of 291 Hemidactylus mabouia (Lacertilia: Gekkonidae) from a rock outcrop area in the state of S?o Paulo, Southeastern Brazil, was studied. Five species were recovered, namely one unidentified species of centrorhynchid acanthocephalan (present only as cystacanths) and the nematodes Parapharyngodon sceleratus, P. largitor (Oxyuroidea: Pharingodonidae), Physaloptera sp. (Spiruroidea: Physalopteridae) and one indeterminate species of Acuariidae (Acuaroidea), with the latter two forms present only as larvae. Infection rates tended to increase with host size, but appeared to be unaffected by season. Hemidactylus mabouia shared most of its helminth fauna with two other sympatric lizard hosts, Mabuya frenata and Tropidurus itambere. The helminth assemblage of the H. mabouia population appears to have been entirely acquired by this exotic gecko from the local helminth species pool, rather than possessing any species from the parasite faunas of the original African populations.     

Characterization of an unidentified Sarcocystis falcatula-like parasite from the South American opossum, Didelphis albiventris from Brazil

An unidentified isolate of a Sarcocystis falcatula-like parasite was obtained from the lungs of budgerigars (Melopsittacus undulatus) fed sporocysts from a naturally-infected South American opossum, Didelphis albiventris from Brazil. Four captive budgerigars fed sporocysts from the opossum intestine died of acute sarcocystosis 8, 10, and 12 days after oral inoculation (DAI); one budgerigar was killed 12 DAI when it was lethargic. Schizonts and merozoites found in the lungs of the budgerigars reacted mildly with polyclonal S. falcatula antibody. The parasite was isolated in equine kidney cell cultures inoculated with lung tissue from a budgerigar that was killed 12 DAI. Two budgerigars inoculated subcutaneously with 100,000 culture-derived S. falcatula merozoites developed acute sarcocystosis and S. falcatula-like schizonts were found in their lungs 15 and 16 DAI. Four budgerigars kept as unfed controls in the same environment remained free of Sarcocystis infection. The parasite underwent schizogony in African green monkey kidney cells and bovine turbinate cells. Merozoites divided by endopolygeny, often leaving a residual body. Polymerase chain reaction studies using primers JNB33/JNB54 and Hinf I and Dra I digestion indicated that the isolate was not S. falcatula. Results of this study indicated that the South American opossum, D. albiventris, is a definitive host for yet another S. falcatula-like parasite.     

Helminths of pond-reared walleye from Wisconsin

One hundred extended growth walleye fingerlings, Sander vitreus (Percidae), collected on 6 October 2004, from 1 rearing pond at the Lake Mills State Fish Hatchery in Lake Mills, Wisconsin, were examined for parasites. Diplostomum sp. (Trematoda: Diplostomatidae), Contracaecum sp. (Nematoda: Anisakidae), Bothriocephalus cuspidatus (Cestoda: Bothriocephalidae), and Proteocephalus sp. (Cestoda: Proteocephalidae) were the only parasites found. The first 3 species occurred as larval stages. Diplostomum sp. and Contracaecum sp. had similar prevalences, mean intensities, and mean abundances (72%, 2.2, and 1.6 and 71%, 2.1, 1.5, respectively) in walleye fingerlings. A headlamp technique used by the Wisconsin Department of Natural Resources personnel generated a prevalence of Diplostomum sp. in the lens that overestimated the prevalence of Diplostomum sp. found in a random subsample of 100 fingerlings examined with a microscope. Proteocephalus sp. and B. cuspidatus infected 14 and 12 fingerlings, respectively.     

Helminths of the ocelot from southern Texas

In the USA, the ocelot (Leopardus pardalis) is a highly endangered felid found only in a few remaining vestiges of native thornshrub brushland in the Lower Rio Grande Valley (LRGV) of extreme southern Texas. From 1987-1998, carcasses of 15 adult ocelots that died of vehicular accidents or natural causes were examined for helminths. All cats had 1-8 (mean = 3) helminth species. All were infected with 1-101 (mean +/- SE = 32 +/- 7) Toxascaris leonina. Other helminths from these ocelots were Alaria marcianae, Brachylaima sp., Mesocestoides lineatus, Taenia rileyi, Oncicola canis, Dirofilaria immitis, Physaloptera rara, Ancylostoma tubaeformae, Cylicospirura chevreuxi, Vogeloides felis, and Metathelazia californica. Additionally, two cats had scarring of the aorta with lesions typical of those caused by Spriocerca lupi, although larval nematodes were not seen. A clinal variation in size of nearly three orders of magnitude was noted in the diplostomatid trematodes in the small intestine of one adult male ocelot. Despite the differences in size, all specimens appeared morphologically identical and were regarded as A. marcianae. Helminth prevalences and abundances, including those of potentially pathogenic species like D. immitis, were low. Although a single heartworm infection may have contributed to the death of one ocelot, helminth infections in general seemed to be of no great consequence to this endangered ocelot population. The helminth fauna of ocelots in the LRGV is reflective of that from wild felids in general; all have been reported previously from the bobcat (Lynx rufus) and mountain lion (Puma concolor) elsewhere in Texas.     

Sarcocystis lindsayi n. sp. (Protozoa: Sarcocystidae) from the South American opossum, Didelphis albiventris from Brazil

A new species, Sarcocystis lindsayi n. sp., is proposed for a parasite resembling Sarcocystis falcatula. It was obtained from the lungs and muscles of budgerigars (Melopsittacus undulatus) fed sporocysts from a naturally-infected South American opossum, Didelphis albiventris, from Jaboticabal, Brazil. Sarcocysts of S. lindsayi n. sp. in budgerigars are microscopic, up to 600 microm long and up to 50 microm wide. The cyst wall is up to 2 microm thick. Ultrastructurally, the sarcocyst wall consists of numerous slender villar protrusions (up to 2.0 microm long and up to 0.3 microm wide), each with a stylet at its tip. Schizonts in cell culture divide by endopolygeny leaving a residual body. Sporocysts are approximately 12 x 7 microm. The parasite is genetically distinct from other organisms that also cycle between opossums and avian species and resemble S. falcatula. Diagnostic genetic variation has been observed in the nuclear large subunit ribosomal RNA gene, the internal transcribed spacer (ITS-1), and each of two other genetic loci. Although the structure of the sarcocyst wall may not provide sufficient grounds for differential diagnosis, several other attributes including schizont morphology and genetic variation at each of these genetic loci permit identification of S. lindsayi n. sp.. Natural intermediate hosts for S. lindsayi n. sp. are not known, and fuller characterization of these and other Sarcocystis species would benefit from experimental avian hosts that are more permissive to the maturation of sarcocysts.     

Helminths infecting the parthenogenetic whiptail lizard Cnemidophorus nativo in a restinga habitat of Bahia State, Brazil

A sample of 101 specimens of the unisexual whiptail lizard Cnemidophorus nativo (Squamata; Teiidae) from a coastal site in Bahia State, Brazil were examined for the presence of endoparasites. Of these, 35 (34.7%) harboured helminths. Six helminth species were recovered from C. nativo, including five nematodes (Physaloptera retusa, Physalopteroides venancioi, Subulura lacertilia, Skrjabinelazia intermedia and Parapharyngodon sp., and one cestode (Oochoristica ameivae), all representing new host records. Most lizards were infected by a single species of helminth and none by more than three. Infection rates were neither significantly influenced by host body size nor by environmental factors. The results are compared with data from studies on other whiptail species in both South and North America.     

Staining and Mounting Helminths

The following procedure is recommended: Fix ces-todes and trematodes (while held flat between glass slides) 0.5-2.0 hr. in the following mixture: formalin, 15; acetic acid (gl.), 5; glycerol, 10; 95% ethyl alcohol, 24; distilled H₂O, 46; all proportions by volume. After freeing them from the slides, wash thoroughly in running water and stain immediately thereafter. Stock staining solution: ferric ammonium alum (violet cryst.), 2 g.; distilled H₂O (cold) 100 ml.; after solution, add 2 ml. concentrated H₂SO₄, bring to a boil; add 1 g. coelestin blue B (Nat. Aniline), boil 3-5 min.; cool and add 10 ml. absolute methyl alcohol and 10 ml. glycerol. Dilute 1 vol. with 3 vol. distilled H20 for use. Stain 5-30 min., depending on size of specimens. Wash with 2 changes 0.5 hr. each of distilled H₂O, then 50% isopropyl alcohol 12-16 hr., 50% isopropyl alcohol 2 hr., followed by graded isopropyl alcohol for dehydration. Ether: ethyl alcohol (equal parts), 1 hr., is followed by embedding in celloidin in a sheet just thick enough to cover the specimens. Trim embedded specimens and dehydrate with isopropyl alcohol, 80%, 90% and absolute. Clear in beechwood creosote. Mount in balsam with cover glasses that overlap the edges of the celloidin 1-2 mm. While drying at 37°C, refill edges of mount with fresh balsam as needed. When dry, remove excess balsam and ring the edges with ordinary gloss enamel paint.     

Serine Proteases of Parasitic Helminths

Serine proteases form one of the most important families of enzymes and perform significant functions in a broad range of biological processes, such as intra- and extracellular protein metabolism, digestion, blood coagulation, regulation of development, and fertilization. A number of serine proteases have been identified in parasitic helminths that have putative roles in parasite development and nutrition, host tissues and cell invasion, anticoagulation, and immune evasion. In this review, we described the serine proteases that have been identified in parasitic helminths, including nematodes (Trichinella spiralis, T. pseudospiralis, Trichuris muris, Anisakis simplex, Ascaris suum, Onchocerca volvulus, O. lienalis, Brugia malayi, Ancylostoma caninum, and Steinernema carpocapsae), cestodes (Spirometra mansoni, Echinococcus granulosus, and Schistocephalus solidus), and trematodes (Fasciola hepatica, F. gigantica, and Schistosoma mansoni). Moreover, the possible biological functions of these serine proteases in the endogenous biological phenomena of these parasites and in the host-parasite interaction were also discussed.     

Parthenogenesis in Parasitic Helminths

SYNOPSIS. In neinatodes, parthenogenesis, meiotic or more oftenmitotic with polyploidy, occurs in the orders Tylenchida andRhabditida. It has evolved independently within the variousfamilies and even certain genera, replacing the usual amphimixisin some species and supplementing it in others with one or moreparthenogenetic generations. Polyploidy, haploidy, abnormalspennatogenesis and absence of sperms have been cited as evidenceof parthenogenesis in some adult cestodes and digenetic trematodes,especially dioecious species in those predominantly hermaphroditicgroups. Evidence now favors interpretation of reproduction bygerminal sacs in trematodes as diploid parthenogenesis whichcan be continued through an indefinite number of generationsin some species by transplanting germinal sacs from infectedto uninfected snails.