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parasitic_infections.pptx
- 2. Definitions Parasitology is a branch of microbiology; it is the scientific study of parasites. Parasitism is a symbiotic relationship that is of benefit to one party or symbiont (the parasite) and usually detrimental to the other party (the host). Parasites are organisms that live on or in other living organisms (hosts), at whose expense they gain some advantage. Parasites that live on the outside of the host’s body are called ectoparasites. Parasites that live inside the host are called endoparasites.
- 3. Definitions The life cycle of a parasite may involve one or more hosts. If more than one host is involved, the definitive host is the host that harbors the adult or sexual stage of the parasite. The host that harbors the larval or asexual stage is the intermediate host. An accidental host is one that serves as a host, but is not the usual host in the parasite’s life cycle. A dead-end host is one in which the parasite cannot continue its life cycle.
- 4. Definitions A facultative parasite is an organism that can be parasitic, but does not have to live as a parasite; it is capable of an independent life. Example: The free-living amoeba, Naegleria fowleri, that causes primary amebic meningoencephalitis An obligate parasite has no choice; it must inhabit a host or hosts. Most parasites that infect humans are obligate parasites
- 5. How Parasites Cause Disease The manner in which parasites cause damage to their host varies from one species of parasite to another, and often depends on the number of parasites that are present. Some parasites produce toxins; some produce harmful enzymes; some invasive and migratory parasites cause physical damage to tissues and organs; some cause the destruction of individual cells; and some cause occlusion of blood vessels and other tubular structures. Sometimes, the host immune response to the parasites causes more injury than do the parasites themselves.
- 6. Parasitic Protozoa • Most protozoa are unicellular. • They are classified taxonomically by their mode of locomotion; amebae move by means of pseudopodia (“false feet”); flagellates move by means of flagella; ciliates move by means of cilia; sporozoans do not move. • Not all protozoa are parasitic (e.g., Paramecium spp.). • Protozoal infections are most often diagnosed by microscopic examination of body fluids, tissue specimens, or feces – specimens are examined for motile trophozoites and dormant cyst stages.
- 7. Parasitic infections caused by protozoa
- 8. Toxoplasmosis A systemic sporozoan infection that, in immunocompetent persons, may be asymptomatic or resemble infectious mononucleosis. Serious disease, even death, may occur in immunodeficient persons. Typically involves the CNS, eyes, lungs, muscles, or heart
- 9. Toxoplasmosis Parasite Toxoplasma gondii Reservoir Definitive host: cats and other felines Intermediate host: rodents, birds, sheep, goats, swine, cattle Mode of transmission Eating infected raw or undercooked meat containing the cyst form of the parasite Ingesting oocysts that have been shed in the feces of infected cats Transplacental, blood transfusion, organ donation Laboratory diagnosis Immunodiagnostic procedures Demonstration of the parasite in stained body tissues or fluids Patient care Use standard precautions for hospitalized patients.
- 10. Amebiasis Protozoal gastrointestinal infection that may be asymptomatic, mild, or severe and is often accompanied by dysentery, fever, chills, bloody or mucoid diarrhea or constipation, and colitis.
- 11. Amebiasis Parasite Entamoeba histolytica Reservoir Symptomatic and asymptomatic humans Fecally contaminated food or water Mode of transmission Ingestion of fecally contaminated food or water containing cysts Flies transporting cysts from feces to food Fecally soiled hands of infected food handlers Oral-anal sexual contact Anal intercourse involving multiple sex partners Laboratory diagnosis Microscopic observation of E. histolytica trophozoites / cysts in stained smears of fecal specimens Patient care Use standard precautions for hospitalized patients
- 12. Giardiasis Protozoal infection of the duodenum and may be asymptomatic, mild, or severe Patients experience diarrhea, steatorrhea, abdominal cramps, bloating, abdominal gas, fatigue, and weight loss
- 13. Giardiasis Parasite Giardia lamblia Reservoir Infected humans Fecally contaminated drinking water and recreational water Mode of transmission Ingestion of cysts in fecally contaminated food or water Person to person by soiled hands to mouth Laboratory diagnosis Microscopic observation of trophozoites / cysts in stained smears of fecal specimens or duodenal aspirates Patient care Use standard precautions for hospitalized patients. Add contact precautions for diapered or incontinent patients
- 14. Balantidiasis Protozoal gastrointestinal infection of the colon causing diarrhea or dysentery, colic, nausea, and vomiting
- 15. Balantidiasis Parasite Balantidium coli Reservoir Pigs and anything that might be contaminated with pig feces Mode of transmission Ingestion of cysts in fecally contaminated food or water Laboratory diagnosis Observing and identifying B. coli trophozoites or cysts in fecal specimens Patient care Use standard precautions for hospitalized patients
- 16. Trichomoniasis Sexually transmitted protozoal disease affecting both men and women Usually symptomatic in women (vaginitis with profuse, thin, foamy, malodorous, greenish- yellowish discharge) Rarely symptomatic in men
- 17. Trichomoniasis Parasite Trichomonas vaginalis Reservoir Infected humans Mode of transmission Direct contact with vaginal and urethral discharges of infected people during sexual intercourse Laboratory diagnosis Saline wet mount examination Patient care Use standard precautions
- 18. Malaria Systemic sporozoan infection with malaise, fever, chills, sweating, headache, and nausea Exhibits periodicity (cycle of chills, fever, and sweating) depending on the particular species of malarial parasite that is causing the infection
- 19. Malaria Parasite Plasmodium spp - P. vivax (most common) - P. falciparum (most deadly) - P. malariae - P. ovale Reservoir Infected humans Infected mosquitoes (Anopheles) Mode of transmission Injection of sporozoites into the bloodstream by an infected female Anopheles mosquito while taking a blood meal Blood transfusion, use of blood-contaminated needles and syringes Laboratory diagnosis Observation and identification of Plasmodium parasites in Giemsa-stained blood smears Patient care Use standard precautions
- 20. Parasitic infections caused by helminths
- 21. Ascariasis (Roundworm) Ascaris infection is one of the most common intestinal worm infections It is found in association with poor personal hygiene, poor sanitation, and in places where human feces is used as fertilizer People infected often show no symptoms
- 22. Ascariasis (Roundworm) Parasite Ascaris lumbricoides Reservoir Infected humans Soil with roundworm eggs Mode of transmission Ingestion of eggs (hands that have contaminated dirt, contaminated foods) Laboratory diagnosis Microscopic examination of stool samples for presence of eggs Treatment Antihelminthic drugs (albendazole, mebendazole, ivermectin)
- 24. Trichuriasis (Whipworm) Often occurs in areas where human feces is used as a fertilizer or where defecation onto soil happens Infected people could suffer from light (asymptomatic) or heavy (frequent, painful passage of stool that contains a mixture of mucus, water, and blood) infestations
- 25. Trichuriasis (Whipworm) Parasite Trichuris trichiura Reservoir Infected humans Soil with whipworm eggs Mode of transmission Ingestion of eggs (hands that have contaminated dirt, contaminated foods) Laboratory diagnosis Microscopic examination of stool samples for presence of eggs Treatment Antihelminthic drugs (albendazole, mebendazole, ivermectin)
- 27. Ancylostomiasis / Necatoriasis (Hookworm) Often occurs in areas where human feces is used as a fertilizer or where defecation onto soil happens The most serious side effects of hookworm infection are the development of anemia and protein deficiency caused by blood loss at the site of intestinal attachment
- 28. Ancylostomiasis / Necatoriasis (Hookworm) Parasite Ancylostoma duodenale Necator americanus Reservoir Infected humans Soil with hookworm eggs Mode of transmission Walking barefoot on contaminated soil Ingestion of eggs (hands that have contaminated dirt, contaminated foods) Laboratory diagnosis Microscopic examination of stool samples for presence of eggs Treatment Antihelminthic drugs (albendazole, mebendazole, pyrantel pamoate)
- 30. Enterobiasis (Pinworm) The most common clinical manifestation of a pinworm infection is an itchy anal region When the infection is heavy, there can be a secondary bacterial infection due to the irritation and scratching of the anal area
- 31. Enterobiasis (Pinworm) Parasite Enterobius vermicularis Reservoir Infected humans Mode of transmission Fecal-oral route (directly by hand or indirectly through contaminated clothing, bedding, food , or other articles) Laboratory diagnosis Tape test Treatment Antihelminthic drugs (albendazole, mebendazole, pyrantel pamoate)
- 33. Parasitic infections caused by arthropods
- 34. Scabies An infestation of the skin by the human itch mite Microscopic itch mite burrows into the upper layer of the skin where it lives and lays its eggs Most common symptoms are intense itching and a pimple-like skin rash
- 35. Scabies Parasite Sarcoptes scabiei Reservoir Infected humans Mode of transmission Direct, prolonged, skin-to-skin contact Laboratory diagnosis Microscopic examination of skin scrapings for the presence of the mite, eggs, or fecal matter Treatment Scabicides (permethrin cream, crotamiton cream, lindane lotion, ivermectin)
- 36. Pediculosis (Lice infestation) A skin infestation by tiny wingless insects that live by sucking blood Lice infestation usually causes severe itching on the infested area
- 37. Pediculosis (Lice infestation) Parasite Pediculus humanus capitis (head louse) Pediculus humanus corporis (body louse) Pthirus pubis (pubic “crab” louse) Reservoir Infected humans Mode of transmission Direct contact or indirectly through personal articles and belongings Laboratory diagnosis Finding live lice or nits on scalp, clothing, beds, linens, towels, and the pubic area Treatment Pediculicides (permethrin cream, malathion lotion, lindane shampoo, oral ivermectin
- 38. Other arthropods Anopheles mosquito – vector for malaria Aedes aegypti mosquito- vector for dengue Ornithodoros spp. (ticks) – vector for Lyme disease
Editor's Notes
- Although parasitology is considered a branch of microbiology, not all organisms studied in a parasitology course are microbes. Of the 3 categories of organisms studied in parasitology – protozoa, helminths, arthropods – only protozoa contains microorganisms ========== Not all parasites cause disease.. But even if a parasite is not causing disease, it is depriving the host of nutrients; therefore parasitic relationships are always harmful to the host ========== Ectoparasites: arthropods (mites, ticks, lice) Endoparasites: protozoa and helminths
- Knowing the life cycle of a particular parasite enables HCPs to control the parasitic infection through intervention at some point in the life cycle
- Trophozoite is the motile, feeding, dividing stage in a protozoan’s life cycle Cysts, oocysts, and spores are dormant stages Protozoal infections are primarily acquired through ingestion or inhalation of cysts, oocysts, or spores, or injection via the bite of an infected arthropod Because of their fragile nature, trophozoites rarely serve as the infective stage
- Cerebral toxoplasmosis is common in AIDS patients Infection during early pregnancy may cause death of the fetus or serious birth defects (brain damage)
- The amoebas may invade mucous membranes of the colon, forming abscesses and amebomas that are sometimes mistaken for carcinoma Amoebas may also be disseminated via the bloodstream to extraintestinal sites, leading to abscess of the liver, lung, brain, and other organs
- Persons with trichomoniasis often also have other STDs, especially gonorrhea
- Plasmodium are intraerythrocytic sporozoan parasites P. vivax and P. ovale results in chills and fever every 48 hours (tertian malaria) P. malariae infection causes chills and fever every 72 hours (quartan malaria) P. falciparum varies from 36 to 48 hours
- Occurs worldwide in areas with warm, moist climates (tropical and subtropical areas) If symptoms occur, they can be light and include abdominal discomfort. Heavy infections can cause intestinal blockage and impair growth in children
- A. lumbrocoides is the largest nematode parasitizing the human intestine
- (1)Adult worms live in the lumen of the small intestine. A female may produce approximately 200,000 eggs per day, which are passed with the feces . (2)Unfertilized eggs may be ingested but are not infective. Fertile eggs embryonate and become infective after 18 days to several weeks , (3)depending on the environmental conditions (optimum: moist, warm, shaded soil). After infective eggs are swallowed , (4)the larvae hatch , (5)invade the intestinal mucosa, and are carried via the portal, then systemic circulation to the lungs . (6)The larvae mature further in the lungs (10 to 14 days), penetrate the alveolar walls, ascend the bronchial tree to the throat, and are swallowed . (7)Upon reaching the small intestine, they develop into adult worms . (1)Between 2 and 3 months are required from ingestion of the infective eggs to oviposition by the adult female. Adult worms can live 1 to 2 years.
- Rectal prolapse could occur Heavy infection in children can lead to severe anemia, growth retardation, and impaired cognitive development.
- (1)The unembryonated eggs are passed with the stool . (2)In the soil, the eggs develop into a 2-cell stage , (3)an advanced cleavage stage , (4)and then they embryonate ; (5)eggs become infective in 15 to 30 days. After ingestion (soil-contaminated hands or food), the eggs hatch in the small intestine, and release larvae (6)that mature and establish themselves as adults in the colon . The adult worms (approximately 4 cm in length) live in the cecum and ascending colon. The adult worms are fixed in that location, with the anterior portions threaded into the mucosa. The females begin to oviposit 60 to 70 days after infection. Female worms in the cecum shed between 3,000 and 20,000 eggs per day. The life span of the adults is about 1 year.
- The loss of iron and protein in children could result in growth retardation and delayed mental development
- (1)Eggs are passed in the stool , (2)and under favorable conditions (moisture, warmth, shade), larvae hatch in 1 to 2 days. The released rhabditiform larvae grow in the feces and/or the soil , (3)and after 5 to 10 days (and two molts) they become filariform (third-stage) larvae that are infective . (4)These infective larvae can survive 3 to 4 weeks in favorable environmental conditions. On contact with the human host, the larvae penetrate the skin and are carried through the blood vessels to the heart and then to the lungs. They penetrate into the pulmonary alveoli, ascend the bronchial tree to the pharynx, and are swallowed . (5)The larvae reach the small intestine, where they reside and mature into adults. Adult worms live in the lumen of the small intestine, where they attach to the intestinal wall with resultant blood loss by the host . Most adult worms are eliminated in 1 to 2 years, but the longevity may reach several years.
- Often the patient will complain of teeth grinding, and insomnia due to disturbed sleep, or even abdominal pain or appendicitis.
- Pinworm eggs become infective within a few hours after being deposited on the skin around the anus and can survive for 2 to 3 weeks on clothing, bedding, or other objects. Because of their small size, pinworm eggs sometimes can become airborne and ingested while breathing. Pinworm eggs can be collected and examined using the “tape test” as soon as the person wakes up. This “test” is done by firmly pressing the adhesive side of clear, transparent cellophane tape to the skin around the anus. The eggs stick to the tape and the tape can be placed on a slide and looked at under a microscope. Because washing/bathing or having a bowel movement can remove eggs from the skin, this test should be done as soon as the person wakes up in the morning before they wash, bathe, go to the toilet, or get dressed. Because itching and scratching of the anal area is common in pinworm infection, samples taken from under the fingernails may also contain eggs. Pinworm eggs rarely are found in routine stool or urine samples.
- (1)Eggs are deposited on perianal folds . (2)Self-infection occurs by transferring infective eggs to the mouth with hands that have scratched the perianal area . Person-to-person transmission can also occur through handling of contaminated clothes or bed linens. Enterobiasis may also be acquired through surfaces in the environment that are contaminated with pinworm eggs (e.g. , curtains, carpeting). Some small number of eggs may become airborne and inhaled. (3)These would be swallowed and follow the same development as ingested eggs. Following ingestion of infective eggs, the larvae hatch in the small intestine (4)and the adults establish themselves in the colon. The time interval from ingestion of infective eggs to oviposition by the adult females is about one month. The life span of the adults is about two months. (5)Gravid females migrate nocturnally outside the anus and oviposit while crawling on the skin of the perianal area . The larvae contained inside the eggs develop (the eggs become infective) in 4 to 6 hours under optimal conditions . Retroinfection, or the migration of newly hatched larvae from the anal skin back into the rectum, may occur but the frequency with which this happens is unknown.
- The intense itching of scabies leads to scratching that can lead to skin sores. The sores sometimes become infected with bacteria on the skin, such as Staphylococcus aureus
- Contact generally must be prolonged; a quick handshake or hug usually will not spread scabies. Animals cannot spread scabies to humans
- Only the body louse is known to spread disease (epidemic typhus, louse-borne relapsing fever, trench fever)
- Aedes has black and white stripes all over the body except wings, but the anopheles only has blocks of black and white scales mainly on the wings.