Human intestinal parasites in the past: new findings and a review

Almost all known human specific parasites have been found in ancient feces. A review of the paleoparasitological helminth and intestinal protozoa findings available in the literature is presented. We also report the new paleoparasitologic findings from the examination performed in samples collected in New and Old World archaeological sites. New finds of ancylostomid, Ascaris lumbricoides, Trichuris trichiura, Enterobius vermicularis, Trichostrongylus spp., Diphyllobothrium latum, Hymenolepis nana and Acantocephalan eggs are reported. According to the findings, it is probable that A. lumbricoides was originally a human parasite. Human ancylostomids, A. lumbricoides and T. trichiura, found in the New World in pre-Columbian times, have not been introduced into the Americas by land via Beringia. These parasites could not supported the cold climate of the region. Nomadic prehistoric humans that have crossed the Bering Land Bridge from Asia to the Americas in the last glaciation, probably during generations, would have lost these parasites, which life cycles need warm temperatures in the soil to be transmitted from host to host. Alternative routes are discussed for human parasite introduction into the Americas.

Prevalence of blood parasites in Tyrannidae (flycatchers) in the Eastern plains of Colombia

Blood samples from 159 birds of the New-world family Tyrannidae (the flycatchers) from the eastern plains of Colombia, were examined for haematozoa parasites, in 1999-2000. Haematozoa were detected in six of 20 species. The overall prevalence was 10.1%. The most common parasites detected were microfilariae, followed by Trypanosoma and Plasmodium. The highest prevalence (9.6%) was found in the Ochre-bellied Flycatcher (Mionectes oleaginea). Mixed infections with more than one genus of blood parasite were rare and most infections encountered were of low intensity. The results of this study suggest an important role of ecologically diverse conditions determining composition, transmission, and prevalence of a blood parasite fauna, presumably through host interaction population density. Some new host parasite relationship records are presented.

Blood and intestinal parasites of squirrels (Rodentia: Sciuridae) in Amazonian Brazil

We report the result of an examination for blood and intestinal protozoa in 12 specimens of the red squirrel Sciurus spadiceus (Rodentia: Sciuridae) from Birroque, municipality of Plácido de Castro, state of Acre, Brazil. No parasites were detected in thin, Giemsa-stained blood films of the animals, but culture of the blood of three in Difco B45 medium blood-agar slants gave rise to isolates of epimastigotes. Inoculation of one isolate into laboratory mice resulted in the appearance of Trypanosoma cruzi-like trypomastigotes in their peripheral blood, and the other two isolates gave rise to transient infections with a T. lewisi-like parasite in inoculated mice and hamsters. The failure of the latter parasite to develop in the triatomine bug Rhodnius robustus suggests that it is probably not T. rangeli. This appears to be the first record of a T. lewisi-like trypanosome in neotropical squirrels. Oocysts of an Eimeria sp., were detected in the faeces of 10 animals (83.3%). The parasite develops in the epithelial cells of the intestine, where it may cause severe damage and sometimes results in death of the animal. No oocysts were detected in bile.

Antimalarial drugs disrupt ion homeostasis in malarial parasites

Plasmodium chabaudi malaria parasite organelles are major elements for ion homeostasis and cellular signaling and also target for antimalarial drugs. By using confocal imaging of intraerythrocytic parasites we demonstrated that the dye acridine orange (AO) is accumulated into P. chabaudi subcellular compartments. The AO could be released from the parasite organelles by collapsing the pH gradient with the K+/H+ ionophore nigericin (20 µM), or by inhibiting the H+-pump with bafilomycin (4 µM). Similarly, in isolated parasites loaded with calcium indicator Fluo 3-AM, bafilomycin caused calcium mobilization of the acidic calcium pool that could also be release with nigericin. Interestingly after complete release of the acidic compartments, addition of thapsigargin at 10 µM was still effective in releasing parasite intracellular calcium stores in parasites at trophozoite stage. The addition of antimalarial drugs chloroquine and artemisinin resulted in AO release from acidic compartments and also affected maintenance of calcium in ER store by using different drug concentrations.

Prevalence and level of antibodies to the circumsporozoite protein of human malaria parasites in five states of the Amazon region of Brazil

The aim of this study was to determine the prevalence of malaria infection and antibodies against the repetitive epitopes of the circumsporozoite (CS) proteins of Plasmodium falciparum, P. malariae, P. vivax VK210, P. vivax VK247, and P. vivax-like in individuals living in the states of Rondônia, Pará, Mato Grosso, Amazonas, and Acre. Active malaria transmission was occurring in all studied sites, except in Acre. P. falciparum was the predominant species in Pará and Rondônia and P. vivax in Mato Grosso. Infection by P. malariae was low but this Plasmodium species was detected in Rondônia (3.5%), Mato Grosso (2.5%), and Pará (0.8%). High prevalence and levels of serological reactivity against the CS repeat peptides of P. falciparum were detected in Rondônia (93%) and Pará (85%). Sera containing antibodies against the CS repeat of P. malariae occurred more frequently in Rondônia (79%), Pará (76%), and Amazonas (68%). Antibodies against the repeat epitope of the standard CS protein of P. vivax VK210, P. vivax VK247, and P. vivax-like were more frequent in Rondônia, Pará, and Mato Grosso. The high frequency of reactions to P. malariae in most of the areas suggests that the infection by this Plasmodium species has been underestimated in Brazil.

Parasites in rodent coprolites from the historical archaeological site Alero Mazquiarán, Chubut Province, Argentina

The aim of this study was to examine the parasitic remains that were found in rodent coprolites collected from the archaeological site Alero Mazquiarán (Chubut Province, 45º44'15"S, 70°25'9"W), which is assigned to the interface of the Araucanian and Tehuelche cultures, dated at 212 ± 35 years B.P. The faecal material from two unidentified rodent species (X-10 and X-11) was collected from one human pelvic cavity found in a multiple burial. The faecal samples were processed and examined using paleoparasitological procedures. The X-10 coprolites were positive for eggs of Monoecocestus sp. (Cestoda: Anoplocephalidae) and the X-11 faeces were positive for Pterygodermatites sp. (Nematoda: Rictulariidae), Trichosomoides sp. (Nematoda: Trichosomoididae) and Monoecocestus sp. In this study, we discuss parasitic life cycles, the zoonotic importance of parasites and the behaviour of the aboriginal people.

Spontaneous stage differentiation of mouse-virulent Toxoplasma gondii RH parasites in skeletal muscle cells: an ultrastructural evaluation

Although the predilection for Toxoplasma gondii to form cysts in the nervous system and skeletal and heart muscles has been described for more than fifty years, skeletal muscle cells (SkMCs) have not been explored as a host cell type to study the Toxoplasma-host cell interaction and investigate the intracellular development of the parasite. Morphological aspects of the initial events in the Toxoplasma-SkMC interaction were analysed and suggest that there are different processes of protozoan adhesion and invasion and of the subsequent fate of the parasite inside the parasitophorous vacuole (PV). Using scanning electron microscopy,Toxoplasma tachyzoites from the mouse-virulent RH strain were found to be attached to SkMCs by the anterior or posterior region of the body, with or without expansion of the SkMC membrane. This suggests that different types of parasite internalization occurred. Asynchronous multiplication and differentiation of T. gondii were observed. Importantly, intracellular parasites were seen to display high amounts of amylopectin granules in their cytoplasm, indicating that tachyzoites of the RH strain were able to differentiate spontaneously into bradyzoites in SkMCs. This stage conversion occurred in approximately 3% of the PVs. This is particularly intriguing as tachyzoites of virulent Toxoplasma strains are not thought to be prone to cyst formation. We discuss whether biological differences in host cells are crucial to Toxoplasma stage conversion and suggest that important questions concerning the host cell type and its relevance in Toxoplasma differentiation are still unanswered.

Oocyst wall formation and composition in coccidian parasites

The oocyst wall of coccidian parasites is a robust structure that is resistant to a variety of environmental and chemical insults. This resilience allows oocysts to survive for long periods, facilitating transmission from host to host. The wall is bilayered and is formed by the sequential release of the contents of two specialized organelles - wall forming body 1 and wall forming body 2 - found in the macrogametocyte stage of Coccidia. The oocyst wall is over 90% protein but few of these proteins have been studied. One group is cysteine-rich and may be presumed to crosslink via disulphide bridges, though this is yet to be investigated. Another group of wall proteins is rich in tyrosine. These proteins, which range in size from 8-31 kDa, are derived from larger precursors of 56 and 82 kDa found in the wall forming bodies. Proteases may catalyze processing of the precursors into tyrosine-rich peptides, which are then oxidatively crosslinked in a reaction catalyzed by peroxidases. In support of this hypothesis, the oocyst wall has high levels of dityrosine bonds. These dityrosine crosslinked proteins may provide a structural matrix for assembly of the oocyst wall and contribute to its resilience.

Zoonotic parasites associated with felines from the Patagonian Holocene

Feline coprolites were examined for parasites with the aim of studying ancient infections that occurred in the Patagonian region during the Holocene period. Eggs compatible to Trichuris sp., Calodium sp., Eucoleus sp., Nematodirus sp., Oesophagostomum sp. (Nematoda), Monoecocestus sp. (Cestoda) and Eimeria macusaniensis (Coccidia) were recovered from faecal samples. The results obtained from the analysis provide evidence of consumption by felids of the viscera of both rodents and camelids. This knowledge allows for improved explanations as to the distribution of parasitism and its significance to the health of humans and animals inhabiting the area under study during the Middle Holocene.

Chemoresistance of Plasmodium falciparum and Plasmodium vivax parasites in Brazil: consequences on disease morbidity and control

In Brazil, malaria still remains a clinically important febrile syndrome for local populations and travelers, occurring mostly in the Amazon Basin. This review aims to report the main efforts employed to control this disease since the 1940s and the emergence of Plasmodium falciparum and Plasmodium vivax chemoresistance to chloroquine and sulphadoxine-pyrimethamine among other drugs. Additionally, in vivo, in vitro and molecular studies as well as malaria chemoresistance consequences on disease morbidity and policy treatment guidelines were commented.

Red blood cells derived from peripheral blood and bone marrow CD34+ human haematopoietic stem cells are permissive to Plasmodium parasites infection

The production of fully functional human red cells in vitro from haematopoietic stem cells (hHSCs) has been successfully achieved. Recently, the use of hHSCs from cord blood represented a major improvement to develop the continuous culture system for Plasmodium vivax. Here, we demonstrated that CD34+hHSCs from peripheral blood and bone marrow can be expanded and differentiated to reticulocytes using a novel stromal cell. Moreover, these reticulocytes and mature red blood cells express surface markers for entrance of malaria parasites contain adult haemoglobin and are also permissive to invasion by P. vivax and Plasmodium falciparum parasites.

Aspidosperma (Apocynaceae) plant cytotoxicity and activity towards malaria parasites. Part I: Aspidosperma nitidum (Benth) used as a remedy to treat fever and malaria in the Amazon

Infusions of Aspidosperma nitidum (Apocynaceae) wood bark are used to treat fever and malaria in the Amazon Region. Several species of this family are known to possess indole alkaloids and other classes of secondary metabolites, whereas terpenoids, an inositol and the indole alkaloids harmane-3 acid and braznitidumine have been described in A. nitidum . In the present study, extracts from the wood bark, leaves and branches of this species were prepared for assays against malaria parasites and cytotoxicity testing using human hepatoma and normal monkey kidney cells. The wood bark extracts were active against Plasmodium falciparum and showed a low cytotoxicity in vitro, whereas the leaf and branch extracts and the pure alkaloid braznitidumine were inactive. A crude methanol extract was subjected to acid-base fractionation aimed at obtaining alkaloid-rich fractions, which were active at low concentrations against P. falciparum and in mice infected with and sensitive Plasmodium berghei parasites. Our data validate the antimalarial usefulness of A. nitidum wood bark, a remedy that can most likely help to control malaria. However, the molecules responsible for this antimalarial activity have not yet been identified. Considering their high selectivity index, the alkaloid-rich fractions from the plant bark might be useful in the development of new antimalarials.

Ecology of cutaneous leishmaniasis in Sinai: linking parasites, vectors and hosts

Cutaneous leishmaniasis (CL) is a neglected clinical form of public health importance that is quite prevalent in the northern and eastern parts of Egypt. A comprehensive study over seven years (January 2005-December 2011) was conducted to track CL transmission with respect to both sandfly vectors and animal reservoirs. The study identified six sandfly species collected from different districts in North Sinai: Phlebotomus papatasi, Phlebotomus kazeruni, Phlebotomus sergenti, Phlebotomus alexandri, Sergentomyia antennata and Sergentomyia clydei. Leishmania (-)-like flagellates were identified in 15 P. papatasi individuals (0.5% of 3,008 dissected females). Rodent populations were sampled in the same districts where sandflies were collected and eight species were identified: Rattus norvegicus (n = 39), Rattus rattus frugivorous (n = 13), Rattus rattus alexandrinus (n = 4), Gerbillus pyramidum floweri (n = 38), Gerbillus andersoni (n = 28), Mus musculus (n = 5), Meriones sacramenti (n = 22) and Meriones crassus (n = 10). Thirty-two rodents were found to be positive for Leishmania infection (20.12% of 159 examined rodents). Only Leishmania major was isolated and identified in 100% of the parasite samples. The diversity of both the vector and rodent populations was examined using diversity indices and clustering approaches.

Intestinal parasites and genotyping of Giardia duodenalis in children: first report of genotype B in isolates from human clinical samples in Mexico

Giardia duodenalis is one of the most prevalent enteroparasites in children. This parasite produces several clinical manifestations. The aim of this study was to determine the prevalence of genotypes of G. duodenalis causing infection in a region of southeastern Mexico. G. duodenalis cysts were isolated (33/429) from stool samples of children and molecular genotyping was performed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis, targeting the triosephosphate isomerase ( tpi ) and glutamate dehydrogenase ( gdh ) genes. The tpi gene was amplified in all of the cyst samples, either for assemblage A (27 samples) or assemblage B (6 samples). RFLP analysis classified the 27 tpi -A amplicons in assemblage A, subgenotype I. Samples classified as assemblage B were further analysed using PCR-RFLP of the gdh gene and identified as assemblage B, subgenotype III. To our knowledge, this is the first report of assemblage B of G. duodenalis in human clinical samples from Mexico.

Genetic diversity of chloroquine-resistant Plasmodium vivax parasites from the western Brazilian Amazon

The molecular basis of Plasmodium vivax chloroquine (CQ) resistance is still unknown. Elucidating the molecular background of parasites that are sensitive or resistant to CQ will help to identify and monitor the spread of resistance. By genotyping a panel of molecular markers, we demonstrate a similar genetic variability between in vitro CQ-resistant and sensitive phenotypes of P. vivax parasites. However, our studies identified two loci (MS8 and MSP1-B10) that could be used to discriminate between both CQ-susceptible phenotypes among P. vivax isolates in vitro. These preliminary data suggest that microsatellites may be used to identify and to monitor the spread of P. vivax-resistance around the world.