01 - Introduction and Neglected Tropical Diseases (NTDs)1. What is a symbiosis? What is each participant in a symbiotic relationship called? What is a trophic interaction? Give some examples. A symbiosis is the association of organisms of different species. Participants are called symbionts. A tropic interaction is a nutritional relationship in which there is a transfer of energy. Examples include remora fish and bigger fish (indirect), termites and intestinal protists (direct). 2. What type of dependency exists between the participants of a phoretic relationship? Does the phoront benefit from the relationship? There is no physiological or biochemical dependence. The phoront benefits in that it gets carried by the host. An example includes pollen being carried by a butterfly. 3. Explain commensalism. How does the commensal benefit? Can these organisms survive independently? Commensalism is an indirect tropic relationship. The commensal benefits while the host is neither harmed nor benefited. Both organisms can survive independently. 4. What is mutualism? Can these partners survive independently? What type of dependence exists between the partners? Give some examples. Mutualism is a direct tropic relationship in which both partners benefit. The partners cannot survive independently. There is a physiological dependence. Examples include termites, which eat wood that is ingested by intestinal protists, and intestinal bacteria which digest blood consumed by leeches. 5. How is each symbiont affected in an exploitation interaction? How do a predator and a parasitoid differ? What is the usually effect of a micropredator on its host? How do micropredators and parasites differ? In an exploitation relationship, one partner benefits while the other is harmed. A predator attacks and kills many hosts, while a parasitoid attacks and kills only one host. Micropredators seldom kill their hosts. A micropredator has many hosts, while a parasite only has one host. 6. What is parasitism? Which partner is harmed? Give the definition of parasitism. What does the parasite get out of the relationship? What does it mean that the parasite has greater reproductive potential than the host? What are some characteristics of a parasitic disease? Parasitism is a relationship between two organisms of different species. The parasite has potential to kill the host. The parasite receives nutrients and a place to live from the host. If the parasite has greater reproductive potential than the host, it means that the parasite will be able to reproduce more often than the host (?). Parasitic diseases are chronic and difficult to control. 7. What is a parasite? For each of the following, identify whether it could be a parasite according to the traditional definition Cestode - yes Trematode - yes Bacteria - no Nematode - yes Virus - no Fungus - no Protozoan - yes Arthropod - yes 8. Define the following: Ectoparasite ? parasite which lives on the host surface Endoparasite ? parasite which lives inside the host Obligate parasite ? has to be parasitic for at least some of its life cycle Facultative parasite ? not normally parasitic Temporary parasite ? spends most of life away from host Permanent parasite ? only away from host for a short period Definitive host ?parasite reaches sexual maturity Intermediate host ? required for development, but parasite does not reach sexual maturity Direct life cycle ? parasite passed from host to host through air, contaminated food/water Indirect life cycle ? parasite develops with IH before being passed to DH 9. How are parasites usually distributed within their host population? What does an overdispersed distribution look like (draw a graph of parasites per host within a host population). What are some explanations for this type of distribution? Parasites are over dispersed within the host population. Few hosts have many parasites. They are heavily infected and often killed. Many hosts have few parasites and are not killed. 10. According to the CDC, what are the leading causes of death in the US? Do bacteria, viruses, or parasites cause many of these diseases? Why should we care about parasites? Heart disease, cancer, stroke, lower respiratory disease, diabetes, accidents. Not caused by bacteria, viruses, or parasites. We should care about parasites because they cause many deaths in underdeveloped countries. 11. According to the WHO, what are the leading causes of death in underdeveloped countries? Heart disease, lower respiratory disease, HIV/AIDS, diarrheal diseases, tuberculosis, malaria, measles. 12. What is the goal of the UN Millennium Declaration which was adopted in 2000? What are the 8 Millennium Development Goals (MDGs) What is the target for completion of these goals? Goal is to achieve sustainable development and eradicate poverty. The 8 MDGs are to eradicate extreme poverty, achieve universal primary education, promote gender equality, reduce child mortality, improve maternal health, combat HIV/AIDS, malaria and other diseases, ensure environmental sustainability, and develop global partnership for development. The target for completion is 2015. 13. Most of the funds for MDG 6 are going toward which diseases? HIV/AIDS and malaria 14. What are NTDs? What STHs, other helminth infections, protozoan infections, and bacterial infections are classified as NTDs? NTDs = Neglected Tropical Diseases STHs =ascoriasis, hookworm infections, trichinriasis Other helminth = schistosomiasis, lymphatic filariasis, onchocerasis, dracunculiasis protozoan = leishmaniasis, chogas, human African trypanosomiasis bacterial = trachoma, Buruli ulcer, leprosy 15. What are 5 common features of NTDs? Why have these features contribute to making these diseases ?neglected?? Do many people die from NTDs compared to other major diseases? High prevalence, rural poverty, ancient diseases, chronic, causes disability and disfigurement. They are ?neglected? because they have a low mortality compared to other major diseases. 16. What do DALYs measure? How can this measure be used to compare diseases? What is the equation? What standard is used for measuring premature death and why? DALYs(Disability Adjusted Life Year) measure the health impact of NTDs. It can be used to compare diseases b/c it measures the number of healthy years lost from premature death or disability. DALY = YLL (Years of Life Lost) + YLD (Years of Live lived with Disability). Japanese life expectancy is used to measure premature death b/c Japanese have highest life expectancy. 17. Why are diseases in underdeveloped parts of the world a threat to us in the United States? What is the best strategy for fighting parasitic infections? 18. Reading assignment questions a. In what parts of the world does contamination by raw sewage increase the transmission of parasites? In countries of the tropical and subtropical belts, where construction of modern sewage systems is still being planned or is just starting. b. How do national public health budgets affect the control of parasitic infections? What economic class is most often affected by parasite infections? Why are pharmaceutical companies reluctant to invest in the development of drugs to treat parasitic infections? Funds go towards research and other programs that improve conditions. Parasite infections most often affect the poor. Pharmaceutical companies are reluctant to invest in the development of drugs to treat infections because victims most likely won?t be able to afford them. c. What role does malnutrition play in susceptibility to disease? Undernourished people, especially children, who have protein deficiency, are more likely to get a parasitic infection. d. Educational programs about parasites usually target what age group? Are these programs very successful? Educational programs target schoolchildren. They are not successful b/c people are resistant to efforts. e. How are climatic conditions related to the transmission of parasites? Climate in tropical areas favor the transmission of parasites. Sweat attracts insects, which are vectors of parasites. 02 ? Trematodes Introduction1. Name the four characteristics which are common to all members of the phylum Platyhelminthes. Phylum Platyhelminthes is divided into which four classes? Dorsoventrally flattened; acoelomates; bilaterally symmetrical; lack circulatory, respiratory, and skeletal systems. Platyhelminthes is divided into class Turbellaria, Monogenia, Cestodia, and Trematoda. 2. Are organisms in the class Turbellaria parasites? What animals are parasitized by Monogeneans? What is the common name of organisms in the class Cestoidea? What are the two subclasses in the class Trematoda? Turbellaria are not parasitic, they are free living. Monogenea are ectoparasites of fish. Cestoidea are commonly known as tapeworms. The subclasses of Trematoda are Aspidogastrea and Digenea. 3. How many hosts are involved in the life cycle of a digenetic trematode? What IH is always involved in the life cycle? What is the common name of digenetic trematodes? Draw a generalized life cycle of digenetic trematodes. Digenetic trematodes have at least 2 hosts in the life cycle. A mollusk (snail) IH is always involved in the life cycle. Digenetic trematodes are commonly known as flukes. Adult worms in DH eggs shed into external environment (hatch in H2O) miracidium (swims and penetrates snail, the IH) sporocyst redia cercaria* exit snail as metacercaria infect DH *AFTER REDIA DEVELOPS INTO CERCARIA, THE CERCARIA CAN ALSO DIRECTLY INFECT THE DH INSTEAD OF BECOMING A METACERCARIA* 4. The embryo inside a trematode egg will develop into a(n) ______. What is the function of the vitelline membrane? What is the operculum? The viscous cushion is composed of _______. Embryo develops into a miracidium. The vitelline membrane protects the miracidium. The operculum is the opening of the egg through which the miracidium can exit the egg. The viscous cushion is composed of mucopolysaccharides. 5. What types of conditions will stimulate hatching of trematode eggs? What does a miracidium do once its eyespot is triggered by light? What effect does this have on the viscous cushion? What is the function of leucine aminopeptidase? Stimuli that trigger hatching include light and temperature. Once the eyespot is triggered, enzymes are released which alter the permeability of the membrane around the viscous cushion. The viscous cushion becomes hydrated and expands, pushing the operculum open. Leucine aminopeptidase digests the shell. 03 ? Trematodes ?H ost-Parasite Interactions and Larval Stages 1. Why are we not constantly sick from the many potential pathogens to which we are constantly exposed? How is the host able to respond to the presence of a parasite? What are the two main sets of mechanisms in animals for resistance to infectious agents and in what animal groups are they found? We are not constantly sick because we have defense mechanisms to fight against pathogens. The host is able to respond to the presence of a parasite through innate resistance and internal defense mechanisms. Two main sets of mechanisms in animals for resistance to infectious agents include innate resistance and specific immunity. Innate resistance is found in all animals, and specific immunity is found in higher animal phyla, such as vertebrae. 2. Give some examples of external surfaces which play a role in innate resistance. Which are physical and which are chemical barriers? Are neutrophils and macrophages examples of specific responses? What do these cells do? External surfaces that play a role in innate resistance include feathers, hair, scales, and skin. Feathers, hair and scales are physical barriers, while skin is a chemical barrier. Neutrophils and macrophages are specific responses which act as phagocytic cells. 3. What are the two types of specific immunity? What is an antibody? What is an epitope? What can happen when an antibody and an epitope combine? What cells are involved in cellular immunity? Two types of specific immunity include antibody responses and cellular immunity. An antibody is a specific protein that is produced in response to an infection. An epitope is a small part of a parasitic macromolecule. When the epitope combines with an antibody, it neutralizes the parasite?s ability to enter the cell. T-cells are involved in cellular immunity. They either combine with specific epitopes or directly kill the parasite. 4. What is the size of a miracidium? What host does it need to infect? Draw a miracidium and label the ciliated epidermal plates, cephalic ganglion, apical papilla, sensory nerve endings, glands, and germinal cells. A miracidium is about 100 um in length. It needs to infect a snail host. 5. To what cues does a miracidium respond during host-finding? How do these responses compare to the response of the snail host to the same cues? What is a miraxone? What two behaviors are measured to determine attraction of a miracidium to a snail? What are the rates of swimming and rate of change of direction when a miracidium is far away from a snail? During host-finding, the miracidium responds to cues such as light, temperature and gravity. These responses are similar to the responses of the snail host to the same cues. A miraxone is a substance secreted by the snail host which attracts the miracidium. Two behaviors that are measured to determine the attraction of a miracidium to snail are swimming speed and rate of change of direction. When the miracidium is far from the snail, the swimming speed is fast and the rate of change of direction is low. 6. What happens during the transformation of a miracidium into a sporocyst? Does a sporocyst have a digestive tract? What is the tegument? What occurs in the germinal sac? The sporocyst does not have cilia, and forms a tegument. The sporocyst does not have a digestive tract. The tegument is an outer surface. Embryos develop in the germinal sac. 7. What happens to a snail when it is infected with Leuchocloridium paradoxum? Why is this advantageous to the parasite? Parasite embryos develop into cercaria and migrate to the snail?s tentacles. The tentacle?s become brightly colored, enlarged, and pulsate. This attracts the snails to birds, which are the next host in the cycle. This is advantageous to the parasite because it increases the chances of being passed on to the next host in its life cycle. 8. How do rediae leave the sporocyst? Does a redia have a digestive tract? What does the redia do with its ambulatory bud? Into what larval stages can the germ balls of a redia develop? Rediae leave the sporocyst by exiting through the birth pore or just bursting out. A redia has a digestive tract. The ambulatory bud aids in movement. The germ balls of a redia can develop into daughter rediae or cercariae. 9. What is parasitic castration? Why is this advantageous to the parasite? Parasitic castration is when the rediae move into the snail reproductive tissue; they feed on and destroy the tissue. The snail can no longer reproduce, so it allocates all of its resources towards growth. This is advantageous to the parasite b/c as the snail grows, there is more space and tissue for the parasite. 10. What is the mechanism by which snails distinguish self from non-self? How does a haemocyte function? Snails distinguish self from non-self through internal defense mechanisms. A haemocyte encapsulates the parasite and releases a cytotoxic superoxide, which phagocytizes the parasite. 11. Draw a typical cercaria and label the head, tail, mouth, pharynx, and intestine. What is the function of the escape glands? Escape glands secrete enzymes which secrete enzymes that aid in the cytolysis of snail tissue. 12. Depending on the species, cercariae take one of what three routes of development? How do some cercariae attach to vegetation? How do some cercariae find spatial and temporal locations which increase the chances of contact with the next host? Cercariae can either encyst on vegetation and develop into metacercaria, pentetrate a second IH and develop into metacercariae, or they can directly penetrate a DH and develop into an adult worm. Cercariae attach to vegetation through post-acetabular glands that secrete mucus. Some cercariae find spatial and temporal locations by using light, gravity, temperature and host cues. They also use circadian release; the cercariae are released from the snail only at certain times of the day; it corresponds to a time when the next host may be present. 13. What is swimmer?s itch? Cercariae might penetrate a human (wrong host) and dies. Humans develop an allergic reaction. 14. What forms the cyst of a metacercaria? How do metacercariae on vegetation differ from those found inside an intermediate host? (?) forms the cyst of metacercaria. Metacercariae on vegetation have a thick and complex cyst wall, while those found inside the IH have a thin and simple cyst wall. 15. What is PITT? Describe this phenomenon using Microphallus papillorobustus as an example. PITT = Parasite-Increased Tropic Transmission. Microphallus papillorobustus infects arthropods and migrate into the brain. This causes the arthropods to swim closer to the surface of the water. As a result, they are more visible to birds, which increase their predation to birds. 16. What stimulates excystation of the metacercariae? Excystation of the metacercariae is stimulatedby stimuli inside the host, such as body temperature and digestive enzymes. Reading assignment questions 1. Is the miracidium a feeding stage? Where are the cytoplasmic ridges found? Does the miracidium have muscles? How is the apical papilla involved in penetration of the snail host? What is the function of flame cells? The miracidium is a non-feeding stage. Cytoplasmic ridges are found at junctures of adjacent epidermal plates. The miracidium has circular and longitudinal muscles. The apical papilla contains glands that secrete enzymes during penetration, allowing it to act like suction. Flame cells collect body fluids that contain waste. 2. What is the function of the tail of the cercaria? What is the function of the escapes glands? The tail allows the cercaria to swim. Escape glands secrete a substance during the cercaria?s emergence from the sporocyst, and during the exit from the snail host. 04 ? Trematodes ? Adult Morphology1. Where is the tegument found? What is a syncytium? How many regions does a trematode tegument have? The glycocalyx is comprised of what type of molecules? Describe some functions of the glycocalyx. Does the distal cytoplasm contain nuclei? What is the function of the distal cytoplasm? The distal cytoplasm and proximal cytoplasm are separated by what type of tissue? How are the distal cytoplasm and proximal cytoplasm connected? What is the function of the proximal cytoplasm? The tegument is found is the outer surface of the adult trematode. A syncytium is multinucleated tissue with no cell boundaries. A trematode tegument has 3 regions. The glycocalyx is comprised of glycoproteins. The glycocalyx has invaginations that increase surface area, and enzymes which increase uptake of molecules. The distal cytoplasm does not contain nuclei. It has vesicles that maintain the glycocalyx, and spines that help the parasite attach. The spines may also function in storage. The distal cytoplasm is separated from the proximal cytoplasm by a muscle layer. They are connected by internuncial processes. The proximal cytoplasm has nuclei and organelles that produce materials to maintain the distal cytoplasm. 2. What are the functions of the two muscle zones in the adult trematode? The subtegumnetal muscle zone contains longitudinal, circular, and diagonal muscles which aid in movement (?). Gastrodermal muscles help food move in the intestine. 3. Where is the cerebral ganglion in an adult trematode? Where are the longitudinal nerve cords found? What is the function of the transverse ring commissures? The nervous system of trematodes is described as being _________. What types of sensory endings are found in trematodes? What are two neurotransmitters found in trematodes? Which is excitatory and which is inhibitory? The cerebral ganglion is on the anterior end. Longitudinal nerve cords branch from the cerebral ganglion and supply the posterior end. Transverse ring commissures connect longitudinal nerve cords and branches to the muscles and tegument. The nervous system of trematodes is described as being ladder like (orthagon). Sensory endings in trematodes are chemoreceptors and tangoreceptors. 5-hydroxytryptomine (serotonin) is an excitatory neurotransmitter. Acetylcholine is an inhibitory neurotransmitter. 4. Draw the digestive tract of an adult trematode and label the following : mouth, pharynx, esophagus, and cecum. Is the digestive tract complete? What do trematode adults eat? The digestive tract is incomplete. Adult trematodes eat (?). 5. What does monoecious mean? Draw the male reproductive tract and label the following: cirrus, male genital pore, cirrus pouch, vas deferens, vas efferens, and testes. Monoecious means both male and female reproductive organs are present. 6. Draw the female reproductive tract and label the following: female genital pore, metraterm, uterus, seminal receptacle, ovary, ovicapt, oviduct, vitelline cells, vitelline duct, Mehlis? gland, and ootype. What is the function for each of these structures? 7. The ovary produces oocytes. The ovicapt is the sphincter which controls the passage of oocytes out of the oviduct. The seminal receptacle stores sperm. The vitelline cells produce yolk and shell material. The Mehlis? gland surrounds the ootype. The muscular, distal portion of the uterus which propels eggs out is the metraterm. 8. What is polyembryony? Why is this strategy significant in the life cycle of trematodes? Polyembryony = asexual reproduction that results in multiple offspring from one embryo. This is significant b/c the parasite doesn?t have to produce as many eggs (?). 9. Draw a diagram of human including the following: lungs, esophagus, diaphragm, stomach, pancreas, gall bladder, liver, bile duct, small intestine (duodenum, jejunum, ileum), cecum, large intestine, and anus. 10. Name three trematodes which live in the human intestine. Fasciolopsis buski, Metagominus yokagawai, Heterophyes heterophyes Name two trematodes which live in the liver or bile duct of humans. Fasciola hepatica, Clonorchis sinensis Name three trematodes which live in the blood of humans. Schistosoma mansoni, Schistosoma japonium, Schistosoma haematobium Reading assignment questions 1. What is the function of the glycocalyx in the uptake of sugars and amino acids from the environment? The glycocalyx has hydrolytic enzymes that aid in the uptake of sugars and amino acids. 2. What is the function of acidic glycosaminoglycans in the glycocalyx? Glycosaminoglycans can inhibit certain digestive enzymes. They enable intestinal trematodes to resist the host?s digestive enzymes. 3. Where in the tegument are Golgi complexes, glycogen deposits, and mitochondria found? In the proximal cytoplasm. 4. How do vesicles move from the proximal cytoplasm to the distal cytoplasm? They move through microtubules in the cyton region and through cytoplasmic bridges. 05 ? Trematodes ? Intestinal1. Answer the following questions about Fasciolopsis buski. Size? 75 mm x 20 mm Common name? large intestinal fluke Transmission stage? Metacercariae(?) Morphology of cecum? unbranched Size of ventral sucker relative to oral sucker? Larger than oral sucker Cephalic cone present? no Draw the life cycle: adult worm in SI eggs in feces miracidium in H2O penetrates snail (IH) sporocyst redia 1 redia 2 cercaria (exits snail) metacercaria (in H2O vegetation) ingested by DH 2. Does a person generally experience symptoms during a light infection of F. buski? Where do the adult worms live in a light infection? What might the person experience in a heavy infection? What causes these symptoms? There are few symptoms during a light infection. During a light infection, adult worms live in the duodenum and jejunum of the small intestine. Symptoms of a heavy infection include inflammation, ulceration, abscesses, abdominal pain, malabsorption, and diarrhea and bowel obstruction. These symtoms are caused by the presence of worms throughout the entire SI. 3. How is an F. buski infection diagnosed? Why is a direct wet smear not the preferred method? Describe the formalin-ethyl acetate sedimentation concentration method. An F. buski infection is diagnosed by checking for eggs in the feces. A direct wet smear is not preferred b/c if the infection is low, eggs may not be found on the slide. In the formalin-ethyl acetate sedimentation concentration method, feces and formalin are strained through guaze; saline is added, and the sample is centrifuged and the supernatant is discarded; next, formalin and ethyl acetate are added, and the sample is centrifuged again; the remaining sediment is examined under the microscope for eggs. 4. What drug is usually used to treat an F. buski infection? How might this drug work? Praziquantel (PZQ). It causes muscular contraction and paralysis of the worm. The tegument is disrupted and the parasite is exposed to attack by the host. PZQ results in a rapid influx of calcium ions, which disrupts the parasite?s functions. 5. What methods can be used to control F. buski infections in the human population? Kill adult worms using PZQ, no use of night soil, snail control through physical removal and molluscicides, and cooking vegetables properly. 6. What is the size of Metagonimus yokagawai and Heterophyes heterophyes? What are the intermediate and definitive hosts in each of the life cycles? What morphological features can be used to identify each of the adults? Do the adults cause pathology? How does clinical disease occur in each of these species? How is infection diagnosed? How is an infection treated? How can infections be controlled? Size = 1.4 mm x 0.5 mm; IH = snail; 2nd IH = fish; DH = human. Adult H. heterophyes have a gonotyl. Adult M. yokagawai have a gonotyl and ventral sucker that are fused and off-center (genitor-acetabulum). Adults do not cause pathology. Clinical disease occurs when eggs are burrowed into the mucosa and erode the tissue. Eggs may even enter the host?s blood. The infection is diagnosed by checking for eggs in the feces using the formalin-ethyl acetate sedimentation concentration method. It is treated using PZQ and can be treated by cooking fish properly.06 ? Trematodes ? Liver/Bile Duct and Lungs1. What is the common name of Fasciola hepatica? In what domestic animals is it commonly found? How many people are infected with this parasite worldwide? Common name = sheep liver fluke. It is commonly found in sheep and catlle. About 2 to 17 million people are infected worldwide. 2. Draw the life cycle of Fasciola hepatica. What stages develop in the intermediate host? Is there a second intermediate host in the life cycle? What is the transmission stage to humans? What plant is the main source of infection to humans? Trace the path of the juveniles through the definitive host. Where does the adult worm live? IH = snail (sporocysts and 2 generations of rediae develop) metacercaria encyst on plants metacercaria excysts in SI penetrates intestinal wall migrates through abdominal cavity penetrates Glisson?s capsule juveniles develop in liver, migrate, feed, grow migrate to bile duct adult; there is not second IH. Metacerceria is transmission stage to humans. Watercress is the main source of infection to humans. Adult worms live in bile duct. 3. List the 5 prominent characteristics of Fasciola hepatica which are helpful in identifying the adult worm. 30 mm x 13 mm, cephalic cone on anterior end, oral and ventral suckers are the samesize, branched testes, branched cecum 4. What pathology is caused by the Fasciola hepatica juveniles and adult in the definitive host? Which stage causes acute fascioliasis? What is the effect of proline secreted by the adult worms? What is cirrhosis? Juveniles and adults cause ulcers in ectopic sites and necrosis of liver tissue. Acute fascioliasis is caused after about 8 weeks of infection. Proline stimulates host collagen deposition and fibrous tissue, which block walls of the bile duct and cause pipestem fibrosis. This causes back pressure, which can lead to liver atrophy and jaundice. Cirrhosis is when normal tissue is replaced with fibrous tissue. 5. How is a Fasciola hepatica infection diagnosed? How is the infection treated? Does Praziquantel work? What effect does Triclabendazole have on the worms? What is blebbing? Infection is diagnosed by checking for eggs in the feces with formalin-ethyl acetate sedimentation concentration. Praziquantel does not work. Triclabendazole causes the tegument to swell due to damage of ion pumps. It causes disruption of the spine, blebbing, swelling of mitochondria, and disrupts movement and vesicles to the distal cytoplasm. Blebbing is a mechanism for shedding the damaged tegument. 6. How can Fasciola hepatica infection be controlled? What is a reservoir host? It can be controlled by proper sewage disposal and control of reservoir hosts. A reservoir host is a non-human animal that can be a DH. 7. What is the common name of Clonorchis sinensis? Does the egg hatch in water? How does the parasite get into the snail host? What is the second intermediate host? Common name = oriental liver fluke.The egg does not hatch in water. The egg gets eaten by the snail. The second IH is fish. 8. Where do the adult C. sinensis worms live and what pathology do they cause? How is pathology related to the intensity of infection? It lives in the bile duct. It erodes the lining of the bile duct, thickens the bile duct, and blocks it (hepatomegaly). Less than 100 worms ? no symptoms; 100 to 1000 worms ? nausea, diarrhea, pain; more than 1000 worms ? jaundice, pain, fever. 9. How is a C. sinensis infection diagnosed? How is the infection treated? Does Praziquantel work? How can infection be controlled? Diagnosis ? eggs in feces. Treated with Praziquantel. The infection can be treated by avoiding the use of night soil, controlling reservoir hosts, and properly cooking fish. 10. What is the common name of Paragonimus westermani? What is a notable characteristic of the cercariae? What is the second intermediate host? Trace the path of the juveniles through the definitive host. Where does the adult worm live? Common name = oriental lung fluke. The cerceriae have a knob like tail and crawl over rocks instead of swimming. The second IH are crabs and crayfish. The metacercaria excysts in the SI and burrows through the intestinal wall; it embeds in the abdominal wall and remains there for about a week, and then migrates into the abdominal cavity; it penetrates the diaphragm and enters the lungs. Adult worms live in the lungs. 11. What pathology and symptoms are associated with P. westermani infections? How is an infection diagnosed? What is the treatment? How is infection controlled? Pathology = necrosis of lung tissue. Symptoms = cough, chest pain, sputum. Diagnosed by checking for eggs in sputum and feces with formalin-ethyl acetate. It is treated with Praziquantel and can be controlled by properly cooking crabs and crayfish. Reading assignment questions 1. What is significant about the life cycle of Fasciola hepatica in the history of the field of parasitology? It was the first life cycle to be completely elucidated among digenetic trematodes. 2. What is the function of miracidial eyespots? They help locate a suitable snail host. 3. Germ balls in the daughter rediae will develop into what stage? Cerceraie 4. How long can adult F. hepatica worms live in the definitive host? 11 years 07 ? Trematodes ? Blood Flukes 1. What is the common name of the Schistosoma? Which three species are of major human health importance? Is schistosomiasis a major problem throughout the world? Common name = blood fluke. Three species of human importance are S. mansoni, S. haematobium, and S. japonicum. They are a major problem throughout the world; 250 million people are infected worldwide. 2. Name 5 major differences between schistosomes and other trematodes. Separate male and female (dioecious), live in blood vessels, egg has no operculum, no rediae, no metacercariae, not food-borne. 3. For each of the human schistosomes, describe the morphology of the egg. How does hatching of the miracidium from the egg occur? What is the function of the suture in the egg? S. mansoni ? lateral spine, S. japonicum ? lateral knob, S. haematobium ? terminal spine. Fresh H2O stimulates the miracidium. It beats its cilia rapidly and begins to spin inside the egg. The line along the eggshell (suture) ruptures and the miracidium escapes. 4. What larval stages occur in a schistosome life cycle? What is schistosomin and how does it affect reproduction in the snail? Miracidium, sporocysts, daughter sporocysts. Schistosomin is a peptide produced by the snail. An infected snail overproduces it, which interferes with its neuroendocrine system. This affects the snails reproductive organs, leading to decreased egg production by the snail. 5. What are the functions of the following cercarial glands? Escape ? exit snail Post-acetabular ? secretes mucous for attachment Pre-acetabular ? penetration of host Head ? adjustment after penetration of DH 6. What changes occur to the cercaria once it penetrates the definitive host? What is it known as now? The cercaria loses its tail and glycocalyx. It is now known as a schistosomulum. 7. Trace the migration path of a schistosomulum in the definitive host. Where do the adults go? It gets into the blood stream and travels to the lungs. It lives in the pulmonary capillaries and feeds on red blood cells. 8. Why don?t adult worms have a pharynx? What is unusual about the cecum? What does sexually dimorphic mean? Where is the gynecophoral canal found and what is its function? What happens to a female that is not paired to a male? They don?t have a pharynx b/c they feed on blood which is liquid. The cecum bifurcates, then joins back together in the posterior end. Sexually dimorphic means the male and female are distinguishable. The gynecophoral canal is found on the male; it is a canal in which the female sits. A female that is not paired with a male does not reach sexual maturity. 9. Fill in the table. 10. How do adult worms avoid immune attack? How is this related to resistance to reinfection? Adult worms avoid immune attack by molecular mimicry. They absorb lipoproteins from the host serum into the tegument. It is related to resistance to reinfection because the host produces an antibody against the schistosomula, but not all get killed. The ones that don?t get killed can mimic the antibody. 11. Describe how the eggs of schistosomes exit the body of the definitive host. Include in your description the following: migration of the mated pair, migration of the female, endothelial cells, miracidial SEA, eosinophils, macrophages, granuloma, wall, and lumen. Pair works upstream into smaller vessels; female travels alone to the smaller vessels and lays eggs; male blocks blood flow during this time; female migrates back to male; endothelial cells lining the vessel actively move over the egg and exclude it from the vein lumen; miracidium releases soluble egg antigen (SEA) which leaves through pores in the eggshell; gramuloma forms around egg along with motile cells (eosinophils and macrophages); granuloma moves across wall to gut or bladder lumen and carries eggs 12. What pathology results from penetration of the cercariae into the definitive host? Which species cause Katayama Fever and what are the symptoms. Cercarial dermatitis ? causes allergic reaction due to penetration into the skin of DH. S. mansoni and S. japonicum cause Katayam fever. Sysmtoms include fever, muscle pain and heptasplenomegaly (enlarged liver and spleen). 13. Where can the eggs become trapped? What is the granulomatous response? What is SEA? What are the benefits and costs of the granuloma to the host? What is Symmer?s pipestem fibrosis? How can kidney failure result from a S. haematobium infection? What is the relationship of schistosome infections to cancer? Eggs can be trapped in the gut/bladder wall or in the blood stream. The granulomatous response is (?). SEA is soluble egg antigen. Benefits of granuloma include protection from toxic substances. A cost of granuloma is pathology. Symmer?s pipestem fibrosis is when the liver function is impaired, causing the heart to take on an extra load. S. haematobium infection can lead to kidney failure b/c the uterus and bladder can become fibrotic, causing back pressure of urine to the kidney. S. haemtobium causes an increase in bladder cancer; S. mansoni causes increase in colon cancer. 14. How are schistosome infections diagnosed? Diagnosed by checking for eggs in urine and feces 15. What is the treatment for schistosomiasis and how does the drug work? Is resistance to this drug developing? What does artemether do to the worms? Treatment = Praziquantel. It damages the tegument and makes the worm vulnerable to immune response. However, resistance is developing. Artemether damanges the tegument, cecum and vitelline glands. 16. What is the function of glutathione-S-transferase in schistosomes? What is the effect of the GST vaccine on infections? Does the vaccine appear to be safe for humans? GST is an enzyme that is an antioxidant. It is a defense mechanism against reactive oxygen species. GST vaccine has an inhibitory effect on egg production. There is no cross reactivity with human GST, so it is safe. 17. Describe some methods of controlling schistosome infections. Drugs, sewage treatment, snail control, boots and gloves when in water, vaccine, education. Reading assignment questions According to the World Health Organization, the strategy to control schistosomiasis should be comprised of what four components? Population-based chemotherapy, with repeated drug administration to infected people; molluscicides; biological controls (carnivorous snails and fish); education size of male size of female tubercles on male tegument? epd habitat in DH S. mansoni 10 mm 14 mm Bumps 200-300 Veins of LI S. haematobium 15 mm 20 mm Bumps 30 Veins of urinary bladder S. japonicum 20 mm 26 mm Smooth 3500 Veins of SI
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