BVT 211 – BIOLOGY OF VECTORSAND PARASITESDr. Nik Ahmad Irwan Izzauddin B. Nik HimRoom: G09/403Email: firstname.lastname@example.org
60% - Final exam 40% - Coursework - 12% - Prof Wahab - 14% - Dr. Nik - 14% - Dr. Hamady
Nutrition and excretion/secretion in parasites Ecology of parasites Treatment and control methods in parasitology Introduction to vectors Arthropod vector Mosquitoes Mosquito-borne diseases:1. Malaria2. Dengue3. Filariasis
NUTRITION ANDEXCRETION/SECRETION IN PARASITESPart 1: Protozoa
HOW A PARASITE GETS NUTRIENT FROMHOST? 2 system are employed by parasites:a) Direct nutrients transfer through membranesb) Through the involvement of various specialized organs/ structures – permanent/temporary.
Based on the kinds of food/ nutrients taken in – 2 class of protozoa1) Phagothropic – if protozoa takes in large particles of food2 ) Saprozoic – Obtaining nourishment by absorption of dissolved organic and inorganic materials The manner of nutrition in Protozoa varies, depending on species and where it lives.
PHAGOTHROPIC Feeding by engulfing a food cell or particle and ingesting it in a phagocytic vacuole In Entamoebidae family, there is a structure called pseudopodia (plural)/ pseudopodium (singular) involved in feeding. In ciliates there is a specialized groove or chamber in the cell where phagocytosis takes place, called the cytostome or mouth.
SPOROZOA The Sporozoa are parasitic protozoans that lack locomotor organs. They have no cilia, no flagella, no pseudopods. At some state in their life histories, they are usually intracellular parasites. The sporozoan can’t move or obtain food by itself and it needs to depend on it’s host for transportation and to obtain food. Feeding on the cells and body fluids of a main organism during their life cycle.
PART 1: PROTOZOA Need to reiterate the following points: - Protozoa consist of a single cell, although many species contain more than one nucleus during all or portions of their life cycles - Cytoplasm contained with a membrane - can be divided into ecto and endoplasm - many organelles/ structures - mitochondria, Golgi apparatus, lysosomes, endoplasmic reticulum, ribosome, contractile vacuoles, flagellum, cilium etc
a) Pentatrichomonas hominis, a harmless commensal of the human digestive tract.b) A species of Trypanosoma, 15–30 μm, from the bloodstream of vertebrates (both a and b have undulating membranes).c) Free-living Amoeba sp., 100–150 μm, showing lobopodia.d) Actinosphaerium sp., 200 μm (many species are much smaller), with actinopodia.e) Arcella vulgaris, a freshwater shelled ameba, about 100 μm with lobopodia.f) Globigerina sp., a marine foraminiferan up to 800 μm, with filopodia.g) Oocyst of Levineia canis, (35–42) (27–33) μm, a coccidian parasite of dogs.h) Zoothamnium sp. colony, individuals 50–60 μm, colony up to 2 mm tall, an obligate ectocommensal ciliate of aquatic invertebrates.i) Euplotes sp., 100–170 μm, a free- living ciliate with ventral cirri and prominent oral membranes.j) Tetrahymena sp., ∼60 μm, a free- living ciliate showing ciliary rows (kineties)
ORGANELLES – WITH DIFFERENT FUNCTIONS Mitochondria – respiration, exception – anaerobic - Mitochondria, the organelles that bear enzymes of oxidative phosphorylation and the tricarboxylic acid cycle, often have tubular rather than lamellar cristae. - In addition, some amebas have branched tubular cristae, but in other protozoan groups the cristae may be absent altogether. - Mitochondria may be present as a single, large body, as in some flagellates, or arranged as elongated, sausage- shaped structures, as occur in pellicular ridges of some ciliates. Ribosomes, endoplasmic reticulum – Secretory functions
Contractile vacuoles – excretion of excess water Flagellum and cilium – locomotion and food gathering Pseudopodia - are temporary extensions of the cell membrane and - are found in amebas as well as in a variety of cell types in other organisms. - Pseudopodia function in locomotion and feeding. All this organelles directly involved with nutrition process
Take up dissolved organics directly across the cell membranes, The most common mechanisms of ingestion are pinocytosis and phagocytosis. The size of the food vacuoles varies greatly, depending on the primarily on the size of the food materials ingested. Ingestion can occur anywhere on the surface of the body, there being no distinct cytostome. Most rhizopodans are carnivores and frequently predaceous.
A food vacuole forms from invagination in the cell surface – sometimes called a food cup – that pinches off and drops inward. This process called endocytosis, occurs in response to stimulus at the environment. Vacuole formation in rhizopodans may be induced either mechanical or chemical stimuli Even nonfood items may be incorporated into food vacuoles, but they are soon ingested. Not only the size of food item, but also the amount of water taken in during feeding determine the size of the food vacuole.
is the case when a molecule causes the cell membrane to bulgeinward, forming a vesiclesurrounding of food particles - pushing of food particles into its cytoplasm
If live prey been ingested, they generally die within a few minutes from the paralytic and proteolytic enzymes present. Undigested material that remains within the vacuole wall reincorporated into cell membrane. In most rhizopodans this process of cell defecation may occur anywhere on the body, but in some active forms it tend to take place at or near the trailing end of the moving cell.
The streaming of protoplasm inside the pseudopods moves the amoeba forward.Amoeba make contacts with a food particle.The pseudopods surround the particle.After the food is corralled by the amoeba, an opening in the membrane allows the food particle to pass into the cell.Inside the cell, the food is enclosed within food vacuoles, digested by enzymes, and assimilated by the amoeba.The amoeba expels particles that are not acceptable as food.
B) Uptake of dissolvednutrients through apinocytotic channel inAmoebaC) Two ameba ingestedciliates by phagocytosis.
PHYLUM KINETOPLASTIDA Trypanosoma brucei, a blood stream parasite
All kinetoplastids are heterotropic. Free-living bodonids capture particulate food, primarilly bacteria, with the aid of anterior flagellum and ingest through a permanent cytostome. The cytostome leads to a cytopharynx which is supported by microtubules At the base of the cytopharynx, food is enclosed in food vacuoles by endocytosis
Unfortunately, little is known about feeding mechanisms in trypanosomes, all of which are parasitic. Some trypanosomes have cytostome-cytopharyngeal complex through which proteins are ingested. The proteins are taken into food vacuoles by pinocyctosis at the base of cytopharynx. It has also reported that some trypanosomes can take in proteins by pinocyctosis from the membrane lining the flagellar pocket or by some sort of cell membrane mediated mechanism.
PHYLUM APICOMPLEXA An apicomplexan sporozoite or merozoite illustrating the apical complex and other structures typical of this life-cycle stage.
The alveoli are interrupted at both the anterior and posterior ends, and at tiny invaginations of the cell membranes called microspores, which have been implicated in feeding. Nutrient ingestion is thought to occur primarily by pinocytosis or phagocytosis at the microspores. In the haemosporidians, ingestion of the host’s cytoplasm through the microspores has been observed. Absorption of the nutrients in some gregarines at the point where the parasite attaches to the host’s cell.
B and C: The body of agregarine is commonly into3 three recognizableregions
PLASMODIUM Malaria parasites transport carbohydrates, amino acids, purine nucleosides, fatty acids, complex lipids, anions and cations and the presence of the parasite confers upon the infected red cell pathological alterations in nutrient transport that may favour the development of the parasite. The asexual stages of the parasite within the red cell lack stored carbohydrate but require considerable quantities of glucose to fuel their active metabolism and division. Infected erythrocytes use between 10 and 50 times more glucose than uninfected cells and the parasite appears to induce permeability changes in the red cell membrane which facilitate the passage of host glucose and amino acids into the erythrocyte.
The nutritional source of amino acids for intracellular stages of malaria is not fully understood; haemoglobin digestion undoubtedly provides significant amounts, but the infected red cell also shows increased transport of free amino acids in culture. In P. falciparum, these changes in amino acid transport rates are first seen 15 hours after invasion and the infected erythrocyte loses energycoupled transport systems in favour of diffusion; whether these amino acids enter the parasite itself by carrier mediated transport or by diffusion remains to be determined and awaits the development of methods permitting culture of the asexual stages of the parasite outside the red cell.
Malaria parasites transport exogenous purine nucleosides but not pyrimidines. This may be related to their inability to synthesize the purine ring de novo. Parasites liberated from red cells may accumulate certain purines (e.g. adenosine, guanosine and hypoxanthine) and can incorporate radioactivity from labelled adenosine, AMP and ATP. Several studies have demonstrated that lipids (i.e. free fatty acids, cholesterol and phospholipid) are readily incorporated into malaria parasites resident within the red cell but the transport processes involved are unknown.
Most diplomonads are phagotrophic and feed on bacteria. These forms have a cytostome through which endocytosis of the bacteria occur. Other genera susch as Giardia lack of cytostomes and are saprozoic, feeding by pinocytosis on mucous secretions of the host’s intestinal tissue.
All parabasilids are heterotrophic and lack of cystome. Fluid is taken up by pinocytosis in depression of cell surface. Some take in by phagoctosis. In heypermastigotes, pseudopodia formed in a sensitive region at the posterior end of the cell engulf wood particles. Trichomonads also form pseudopodia that engulf bacteria, cellular debris and leukocytes
The ciliates include may different feeding types. Some are filter feeders, other capture and ingest other protista or small invertebrates, many eat algal filaments or diatoms, some graze on attached bacteria, and a few are saprophytic parasites. In most ciliates, feeding is restricted to a specialized oral area containing the cytostome or ‘the cell mouth’. Food vacuoles are formed at the cytostome and then are circulated through the cytoplasm a digestion occurs.
There are a variety of structures associated with, and modifications of the cytostome. Holozoic ciliates that ingest relatively large food items usually possess a nonciliated tube – called the cytopharnx, which extend from cytosome deep into the cytoplasm. The wall of the cytopharynx often reinforced with rods of microtubules (nematodesmata). In Didinium, the cytopharynx is normally everted to form a projection that sticks to prey and then inverts back into the cell, thus pulling the prey into food vacuole.
In this way Didinium can engulf its relatively gigantic prey. Other ciliates, such as hypostomes, have complex nematodesmal baskets in which microtubules work together to withdrawn filament of algae into cytostome, reminiscent on the way sucks up a piece of spaghetti. In most of these ciliates, the cilia around the mouth are relatively simple
Other ciliates, including many of more familiar form (e.g Stentor) are suspension feeders. These often lack or have reduced cytopharynxes. They have elaborate speciall oral cilia for creating water currents, and filtering structures or scrapping devices. Their cytostomes often sit in a depression on the cell surface.
The size of food eaten by such ciliates depends on the nature of feeding current and when present, the size of depression. The oral ciliates often consists of compound ciliary organeles, call the adoral zone of membranelles or simply the AZM, on the other side of cytostome and a row of closely situated paired cilia which is frequently called the paroral membrane on the other side. E.G Euplotes, Stentor, and Vorticella. Many hypotrichs e.g Euplotes that move about the substratum with their oral region oriented ventrally use their specialized oral ciliature to swirl settle materials into suspension and then into buccal cavity for ingestion.
Among the most specialized cialite feeding methods are those use by suctorians, which lack cilia as adults and instead have knobbed feeding tentacles. A few suctorians, have two types of tentacles, one form for food capture, and another one for digestion. The swelling at the tips of the tentacles contains extrusomes called haptocysts, which are discharged upon contact with potential prey.
Portions of the haptocyst penetrate the victim and hold it to the tentacle. Sometime prey are actually paralysed after contact with haptocycts, presumably by enzymes released during discharge. Following attachment to the prey, a temporary tube forms within the tentacle and the contents of the prey are sucked into tentacle and incorporated into food vacuoles
Phylum Ciliophora: Feeding insuctorian ciliate Acinate.A) Acinate has capitate feeding tentacles; note the absence of ciliaB) Contact with prey and firing of haptocysts into preyC) Shortening the tentacle and formation of a temporary feeding duct within the ring of microtubulesD) Drawing of contents of prey into duct and formation of food vacuole
Several other types are extrusomes are present in the ciliates. Some predatory ciliates have tubular extrusomes, called toxicysts, in the oral region of the cell. During feeding, the toxicysts are extruded and release their contents, which apparently include both paralytic and digestive enzymes. Active prey are first immobilised and then partially digested food is later taken into food vacuoles.
Some ciliates have organelles called mucocysts located on the beneath the pellicle. Mucocysts discharge mucus onto the surface of the cell as a protective coating; they may also play a role in cyst formation. Other have trichocysts, which contain nail-shaped structures that can be discharged through the pellicle. This structure serve a defensive function.
Extrusomes in ciliates:A) ToxicystsB) MucocystsC) The pellicle showing of mucocysts of (rised dots) just below the surface
EXCRETION AND OSMOREGULATION Most protozoa appear to be ammonotelic; that is, they excrete most of their nitrogen as ammonia, most of which readily diffuses directly through the cell membrane into the surrounding medium. Other sometimes unidentified waste products are also produced, at least by intracellular parasites. After these substances are secreted they are accumulated within their host cell and, on the death of the infected cell, have toxic effects on the host. Carbon dioxide, lactate, pyruvate, and short-chain fatty acids are also common waste products.
Contractile vacuoles are probably more involved with osmoregulation than excretion. Because free living, freshwater protozoa are hypertonic to their environment, they imbibe water continuously by osmosis. Contractile vacuoles effectively pump out the water. Marine species and most parasites do not form these vacuoles, probably because they are more isotonic to their environment. However, Balantidium species have contractile vacuoles.
CONTRACTILE VACUOLE Water is collected into the central ring of the vacuole and actively transported from the cell
RFERENCES; Foundations of Parasitology Parasitology – An Integrated Approach