Protozoan parasites of British small rodents

Thirty-five species of protozoan parasites belonging to thirteen genera have now been recorded for British small rodents. These include species of Entamoeba, Giardia, Spironucleus, Trichomonas, Chilomastix, Eimeria and Cryptosporidium in the gut; Trypanosoma, Hepatozoon and Babesia in the blood; and Toxoplasma, Frenkelia and Sarcocystis in the tissues. Recent advances have progressed along two lines, the elucidation of the life-cycles of the species of Frenkelia and Sarcocystis , which are now known to involve a carnivore as the final host, and laboratory studies on those parasites that can be maintained in laboratory animals. It is now possible to draw up a definitive list of hosts and parasites and this should serve as a basis for studies on the epidemiology of these parasites and their possible effects on their hosts.     

Protozoan and helminth parasites of humans in mainland China

To date, 30 species of protozoa, 12 species of cestodes, 26 species of trematodes, 23 species of nematodes, two species of gordius and one acanthocephalan species hae been reported as parasites of man in mainland China.     

Protozoan parasites in group-living primates: testing the biological island hypothesis

A series of articles by W.J. Freeland published in the 1970s proposed that social organization and behavioral processes were heavily influenced by parasitic infections, which led to a number of intriguing hypotheses concerning how natural selection might act on social factors because of the benefits of avoiding parasite infections. For example, Freeland [1979] showed that all individuals within a given group harbored identical gastrointestinal protozoan faunas, which led him to postulate that social groups were akin to "biological islands" and suggest how this isolation could select specific types of ranging and dispersal patterns. Here, we reexamine the biological island hypothesis by quantifying the protozoan faunas of the same primate species examined by Freeland in the same location; our results do not support this hypothesis. In contrast, we quantified two general changes in protozoan parasite community of primates in the study area of Kibale National Park, Uganda, over the nearly 35 years between sample collections: (1) the colobines found free of parasites in the early 1970s are now infected with numerous intestinal protozoan parasites and (2) groups are no longer biological islands in terms of their protozoan parasites. Whatever the ultimate explanation for these changes, our findings have implications for studies proposing selective forces shaping primate behavior and social organization.     

Protozoan parasites: programmed cell death as a mechanism of parasitism

Programmed cell death (PCD) is a potent mechanism to remove parasitized cells, but it has also been shown that protozoan parasites can induce or inhibit apoptosis in host cells. In recent years, it has become clear that unicellular parasites can also undergo PCD, meaning that they commit suicide in response to various stimuli. This review focuses on the role of protozoan PCD and on the interaction between protozoan parasites and the host cell death machinery from the perspective of parasite survival strategies.     

Protozoan species accrual on artificial islands in differing lentic and wetland systems

In the recently broadened context of insular biogeographic theory, artificial substrates might well be considered as initially barren islands with the surrounding natural community acting as a source pool of potential colonists. In an attempt to relate protozoan communities forming on polyurethane foam (PF) substrates to their environments, a series of field experiments were performed in several aquatic and semi-aquatic (wetlands) systems in Michigan, Virginia, and Colorado. Results were considered in the context of island colonization theory.Given relatively stable environmental conditions and sufficient time to colonize, protozoa formed highly replicable communities on PF substrates; MacArthur & Wilson's equation for noninteractive island colonization, S = Seq ·(l-e^–Gt ), accuratelt described the process of species accrual in most cases. Sites were compared using non-linear regression estimates of the parameter, G, which reflects the rate at which substrates attained equilibrium species numbers. In general, the rate of equilibrium acquisition reflected differences in productivity and structure between the protozoan communities from the various habitats and systems studied.     

Protozoan parasites in cultured mussels Mytilus galloprovincialis in the Thermaikos Gulf (north Aegean Sea, Greece)

The protozoans Ancistrum mytili (Oligohymenophorea: Ancistridae) and Marteilia refringens/maurini (Marteiliidea: Marteiliidae) were found parasitizing cultured mussels Mytilus galloprovincialis L. in the Thermaikos Gulf (north Aegean Sea, Greece). The former did not affect the condition index of infected mussels, in contrast to the latter, which did so and which also induced hemocyte infiltration in the affected digestive epithelium. The prevalence of both parasites was relatively high in a polluted area.     

Coccidian parasites of four Panamanian lizard species

Eight species of coccidia (Apicomplexa: Eimeriidae) are reported from Panamanian lizards. –Eimeria randolphi n. sp. is a biliary parasite of –Gymnopthalmus speciosus (Gymnopthalmidae) with cylindrical oöcysts, 29.1 × 16.8 m (25.0–31.5 × 15.0–18.5), an oöcyst length/width index (shape-index, SI) of 1.73 (1.46–2.07) and no polar granule or oöcyst residuum. Ovoidal sporocysts are 9.5 × 7.8 m (9.0–10.5 × 7.0–8.5), with an SI 1.21 (1.06–1.43), a sporocyst residuum and no Stieda body. –E. gymnopthalmi n. sp., an intestinal parasite of –G. speciosus, has round to oval oöcysts of 22.4 × 20.5 m (21–24 × 18–23), an SI of 1.09 (1.00–1.28) and no polar granule or oöcyst residuum. Sporocysts are ovoidal, 8.9 × 7.7 m (8–10 × 7–9), with an SI of 1.16 (1.06–1.29), a prominent sporocyst residuum and no Stieda body. –E. lepidophymae n. sp. parasitises the gall-bladder of –Lepidophyma flavimaculatum (Xantusiidae) and has cylindrical oöcysts of 36.7 × 18.5 m (34.0–40.0 × 16.0–20.5), an SI of 1.99 (1.79–2.31) and no polar granule or oöcyst residuum. Sporocysts are ovoidal, 10.3 × 8.8 m (9.0–11.0 × 8.0–9.5 m), with an SI of 1.17 (1.06–1.29), a sporocyst residuum and no Stieda body. –E. limifronsi n. sp. parasitises the intestine of –Anolis limifrons (Polychrotidae). Oöcysts are oval, 22.5 × 16.0 m (20.0–26.0 × 14.5–17.5), an SI of 1.41 (1.18–1.73) and no polar granule or oöcyst residuum. Sporocysts are ovoidal, 8.4 × 7.5 m (7.5–9.0 × 7.0–8.5), an SI of 1.13 (1.00–1.29), a small sporocyst residuum and no Stieda body. –Isospora limifronsi n. sp. parasitises –A. limifrons and has oval to round oöcysts with a rough, pitted wall, 24.5 × 22.4 m (20–27 × 19–25), an SI of 1.09 (1.00–1.23) and no oöcyst residuum or polar granule. Ovoidal sporocysts are 14.7 × 10.2 m (13–17 × 9–13), with an SI of 1.44 (1.27–1.58), a central sporocyst residuum, Stieda body and a prominent, homogeneous sub-Stieda body. –Anolis limifrons is also parasitised by –I. achiotensis n. sp. The oval to round oöcysts are 22.0 × 19.8 m (20–24 × 18–22.5), with a smooth wall, an SI of 1.11 (1.05–1.25) and no oöcyst residuum or polar granule. Sporocysts are ovoidal, 12.6 × 9.5 m (11–14.5 × 7.5–11), have an SI of 1.32 (1.10–1.60), a small central residuum often hidden by sporozoites, and no Stieda or sub-Stieda body. –I. gonatodi n. sp., from –Gonatodes albogularis fuscus, has oval to round oöcysts 23.0 × 21.8 m (20–25 × 19–24), an SI of 1.06 (1.00–1.16) and a variably present oöcyst residuum. Sporocysts, 12.0 × 9.6 m (10–14 × 9–11), with an SI of 1.25 (1.10–1.44), have no Stieda or sub-Stieda body. A sporocyst residuum comprised of loosely adherent or scattered, irregular granules is present. Panamanian –Gonatodes albogularis fuscus are also parasitised by –I. albogularis.     

Host plant species affects virulence in monarch butterfly parasites

1. Studies have considered how intrinsic host and parasite properties determine parasite virulence, but have largely ignored the role of extrinsic ecological factors in its expression. 2. We studied how parasite genotype and host plant species interact to determine virulence of the protozoan parasite Ophryocystis elektroscirrha (McLaughlin & Myers 1970) in the monarch butterfly Danaus plexippus L. We infected monarch larvae with one of four parasite genotypes and reared them on two milkweed species that differed in their levels of cardenolides: toxic chemicals involved in predator defence. 3. Parasite infection, replication and virulence were affected strongly by host plant species. While uninfected monarchs lived equally long on both plant species, infected monarchs suffered a greater reduction in their life spans (55% vs. 30%) on the low-cardenolide vs. the high-cardenolide host plant. These life span differences resulted from different levels of parasite replication in monarchs reared on the two plant species. 4. The virulence rank order of parasite genotypes was unaffected by host plant species, suggesting that host plant species affected parasite genotypes similarly, rather than through complex plant species-parasite genotype interactions. 5. Our results demonstrate that host ecology importantly affects parasite virulence, with implications for host-parasite dynamics in natural populations.     

Avian hemosporidian parasites from northern California oak woodland and chaparral habitats

During spring-summer 2003-2004, the avian community was surveyed for hemosporidian parasites in an oak (Quercus spp.) and madrone (Arbutus spp.) woodland bordering grassland and chaparral habitats at a site in northern California, a geographic location and in habitat types not previously sampled for these parasites. Of 324 birds from 46 species (21 families) sampled (including four species not previously examined for hemosporidians), 126 (39%) were infected with parasites identified as species of one or more of the genera Plasmodium (3% of birds sampled), Haemoproteus (30%), and Leucocytozoon (11%). Species of parasite were identified by morphology in stained blood smears and were consistent with one species of Plasmodium, 11 species of Haemoproteus, and four species of Leucocytozoon. We document the presence of one of the parasite genera in seven new host species and discovered 12 new parasite species-host species associations. Hatching-year birds were found infected with parasites of all three genera. Prevalence of parasites for each genus differed significantly for the entire sample, and prevalence of parasites for the most common genus, Haemoproteus, differed significantly among bird families. Among families with substantial sample sizes, the Vireonidae (63%) and Emberizidae (70%) were most often infected with Haemoproteus spp. No evidence for parasite between-genus interaction, either positive or negative, was found. Overall prevalence of hemosporidians at the northern California sites and predominance of Haemoproteus spp. was similar to that reported in most other surveys for the USA, Canada, and the Caribbean islands.     

Listeria species in a California coast estuarine environment

Listeria species and L. monocytogenes were found in 81 and 62%, respectively, of fresh or low-salinity waters (37 samples) in tributaries draining into Humboldt-Arcata Bay, Calif., during a winter (January-February) sampling period. The incidence of Listeria species and L. monocytogenes in sediment (46 samples) from the same sites where water was sampled was 30.4 and 17.4%, respectively. One of three bay water samples contained Listeria species (including L. monocytogenes), while of 35 samples of oysters examined, only 1 was found positive for Listeria species (L. innocua). A given species or L. monocytogenes serogroup appeared to predominate in fresh water when domesticated animals (cows, horses) were nearby, whereas greater variety with no species predominance was observed in areas with no direct animal influence.