Review Article- Parasites: Introduction, Classification, Lifecycle and Relationship with their Hosts

Parasites are microorganism that need host to continue its lifecycle, some of them need direct life cycle while others needs indirect lifecycle. In this review article the researcher focus on things that related to types of parasites, as well as their lifecycles, and the type of the hosts, and how parasites affect the host and their relationship. The review comes over a wide range of years up to 2020, and the last published researches that are related to the topic of this review. The review discusses briefly the classification of the parasites and classified them into three main classes (groups), which are, Helminthes, Protozoa, and Arthropods. Eventually, the researchers came to a certain conclusions such as parasites are living species that needs host to continue its life cycle, there are many types of hosts depend upon the needs of parasites, there are more than eight million of parasites and their weight ranged from 25 microgram up to 70 grams.

Proteomic Analysis Of Trichuris Trichiura Egg Extract Reveals Potential Immunomodulators And Diagnostic Targets

Background: Trichuris trichiura embryonated eggs are the infectious developmental stage and the first signal to the immune system of the definitive host. Each infective T. trichiura egg carries the antigens needed to challenge the immune system with a wide variety of proteins present in the shell, larvae’s surface, and the accompanying fluid that contains their excretions/secretions. The parasite eggs constitute the first antigenic stimuli to evoke the host response to this intestinal parasite with direct life cycle and enteric development.Methods: The soluble egg extract of T. trichiura obtained from naturally infected African green monkeys (Chlorocebus sabaeus) was investigated using a proteomic approach by mass spectrometry. The antigenic profile of the egg soluble proteins against sera IgG from C. sabaeus with trichuriasis was also investigated by Western blot and LC-MS/MS from the corresponding SDS-PAGE gel.Results: A total of 231 proteins were accurately identified, 168 with known molecular functions. The proteome of the egg lysate revealed common protein families including energy and metabolism; cytoskeleton, motility and muscle; proteolysis; signaling; stress and detoxification; transcription and translation and; lipid binding and transport. Vitellogenin N and VWD and DUF1943 domain containing protein, Poly-cysteine and histidine tailed protein isoform 2, Heat shock protein 70, Glyceraldehyde-3-phosphate dehydrogenase, Actin and Enolase, were among the potential immunoactive proteins. Conclusions: To our knowledge, this study represents the first attempt to identify the proteome of the T. trichiura egg extract as a novel source of immunomodulators and targets for immunodiagnosis able to contribute to the treatment of human autoimmune diseases and to the control of this neglected disease.

Morphological, Molecular, and Pathological Appraisal of Hymenolepis nana (Hymenolepididae) Infecting Laboratory Mice (Mus musculus)

Hymenolepis nana, typically a parasite found in conventionally established mouse colonies, has zoonotic potential characterized by autoinfection and direct life cycle. The objective of this study was to determine the rate of parasite infection in laboratory mice. The hymenolepidide cestode infected 40% of the 50 mice sampled. The rate of infection in males (52%) was higher than in females (28%). Morphological studies on the cestode parasite showed that worms had a globular scolex with four suckers, a retractable rostellum with 20–30 hooks, and a short unsegmented neck. In addition, the remaining strobila consisted of immature, mature, and gravid proglottids, irregularly alternating genital pores, lobulated ovaries, postovarian vitelline glands, and uteri with up to 200 eggs in their gravid proglottids. The parasite taxonomy was confirmed by using molecular characterization based on the sequence analysis of the mitochondrial cytochrome c oxidase subunit 1 (mtCOX1) gene. The parasite recovered was up to 80% identical to other species in GenBank. High blast scores and low divergence were noted between the isolated parasite and previously described H. nana (gb| AP017666.1). The phylogenetic analysis using the COX1 sequence places this hymenolepidid species of the order Cyclophyllidea.

Morphological, molecular and pathological appraisal of Hymenolepis nana (Hymenolepididae) infecting laboratory mice Mus musculus

Background: Hymenolepis nana , commonly found parasite in mice colonies maintained under conventional conditions, has zoonotic potential and is characterised by autoinfection and direct life cycle. Results: This study intended to determine parasitic infection rate in laboratory mice. Of the 50 mice, 40.0% were found to be infected with hymenolepidid cestode. Infection rate was higher in males (52.0%) than in females (28.0%). Light and scanning electron microscopic studies of cestode parasite revealed that the worms were medium-sized; had globular scolex with four suckers, a retractable rostellum equipped with 20-30 hooks, and a short unsegmented neck; remaining strobila consisted of immature, mature, and gravid proglottids; irregularly alternating genital pores; lobulated ovary; post-ovarian vitelline gland; and uterus containing ˃200 small eggs in gravid proglottids. Molecular characterisation based on mitochondrial COX1 gene sequence analysis used to confirm taxonomy of the parasite. The parasite showed identity ˃80.0% with other species available in GenBank. High blast scores and low divergence were noted between isolated parasite and previously described H. nana (gb| AP017666.1). Phylogenetic analysis using COX1 sequence place this hymenolepidid species within Cyclophyllidea. Conclusions: The present species was found to be deeply embedded in the genus Hymenolepis with close relationships to other H. nana as a putative sister taxon.

Heterogeneity in helminth infections: factors influencing aggregation in a simple host–parasite system

The almost universally-occurring aggregated distributions of helminth burdens in host populations have major significance for parasite population ecology and evolutionary biology, but the mechanisms generating heterogeneity remain poorly understood. For the direct life cycle monogenean Discocotyle sagittata infecting rainbow trout, Oncorhynchus mykiss, variables potentially influencing aggregation can be analysed individually. This study was based at a fish farm where every host individual becomes infected by D. sagittata during each annual transmission period. Worm burdens were examined in one trout population maintained in isolation for 9 years, exposed to self-contained transmission. After this year-on-year recruitment, prevalence was 100% with intensities 10–2628, mean 576, worms per host. Parasite distribution, amongst hosts with the same age and environmental experience, was highly aggregated with variance to mean ratio 834 and negative binomial parameter, k, 0.64. The most heavily infected 20% of fish carried around 80% of the total adult parasite population. Aggregation develops within the first weeks post-infection; hosts typically carried intensities of successive age-specific cohorts that were consistent for that individual, such that heavily-infected individuals carried high numbers of all parasite age classes. Results suggest that host factors alone, operating post-infection, are sufficient to generate strongly overdispersed parasite distributions, rather than heterogeneity in exposure and initial invasion.

The helminth community of the Iberian hare, Lepus granatensis (Lagomorpha: Leporidae), in the province of Granada, Spain

The helminth community of the Iberian hare, Lepus granatensis, in the southern Spanish province of Granada was analysed, thorough the study of 487 individuals shot by hunters between November 1998 and October 1999. Six helminth species were found: Mosgovoyia pectinata (Cestoda); Trichostrongylus retortaeformis, Nematodiroides zembrae, Nematodirus sp., Passalurus ambiguus and Micipsella numidica (Nematoda). N. zembrae and M. pectinata (62.4 % and 17.2 %, respectively) were the only component species found. The predominance of helminth species with a direct life cycle is noteworthy. These two component species were significantly influenced by season of capture. Other factors, such as host age and municipality of capture, influenced the prevalences and/or abundances of the component species, while host sex did not exert any important role. These variations, determined by extrinsic and/or intrinsic factors, in the helminth community could be related to the ecology of the Iberian hare, mainly diet, habitat and behaviour.

On the development of a parasitic copepod, Lamproglena clariae Fryer, 1956 (Copepoda, Lernaeidae) infecting the sharp tooth catfish, Clarias gariepinus

The postembryonic development of the gill parasite, Lamproglena clariae, infecting the sharp tooth catfish, Clarias gariepinus was established from egg culture and artificial infection of fish under laboratory conditions. Like most fish parasitic copepods, L. clariae has a direct life cycle utilizing only a single fish host species. Adult post metamorphosis females produce two egg strings. The mean number of eggs in each egg string was 52. Three naupliar and first copepodid stages were obtained in culture while two copepodid stages, cyclopoid and adult specimens were obtained after artificial infection of catfish in aquaria. First stage nauplii were globular in shape and densely filled with yolk. Nauplii lacked a perforation for the mouth and masticatory parts of the appendages, all of which indicate that they do not feed. Body architecture of the first copepodid stage of L. clariae is similar to that of all other copepods in the number and kind of somites: a cephalothorax with five appendages, three thoracic somites, one abdominal somite and furca rami. This seems to be a conserved morphology among the copepods. The three naupliar and three copepodid stages are described and compared to related copepods.

Other adult and larval cestodes

Adult Diphyllobothrium latum is acquired by consumption of raw fish by persons living around lakes/reservoirs/rivers. Hymenolepis nana can have a direct life cycle so eggs produced by adults in man are important in transfer between humans. The contribution of rodents and the indirect life cycle through arthropods need re-evaluation. Other minor adult cestode infections are described.Man can be an intermediate host for tissue metacestodes. Taenia multiceps and related species are that acquired from canids and produce a coenurus. Spirometra spp. pleurocercoids are acquired from copepod or reptile/amphibian/mammalian intermediate hosts. Other metacestode infections are very rare.

Helminth parasites of Leptodactylus podicipinus (Anura: Leptodactylidae) from south-eastern Pantanal, State of Mato Grosso do Sul, Brazil

Forty-three specimens of Leptodactylus podicipinus (Anura: Leptodactylidae) were collected in the south-eastern Pantanal, municipality of Corumbá, State of Mato Grosso do Sul, Brazil in February and July 2007, and examined for endoparasites. Forty (93%) specimens were infected with at least one helminth species. The predominant parasites were nematodes (Aplectana sp., Cosmocerca podicipinus, Oswaldocruzia lopesi, Physalopteroides venancioi, Rhabdias sp.), but the trematode Catadiscus propinquus also showed high prevalence. The trematodes Infidum infidum and Travtrema stenocotyle were also found, but in only one specimen. Adult frogs showed higher parasite diversity than subadults. Leptodactylus podicipinus was preferentially infected by direct life-cycle parasites and was reported as a new host record for seven helminth species.