Parasitic Infections: Protozoans

Parasitic Infections

• Parasites are divided into protozoans, which are microscopic, single-celled eukaryotes, and helminths, which are macroscopic, multicellular worms.
• Disease-causing parasites need a host to survive.
• Parasitic infections are a world wide problem.
• Malaria infects over 200 million people with over half a million deaths annually, mostly children.
• Amebiasis affects over 500 million people.

Parasitic Protozoans: Morphology and Pathogenesis

• Protozoans can vary in size between 2–100 μm.
• Protozoans contain membrane-bound nuclei and cytoplasm.
• The trophozoite is the active, metabolically active, and reproductive stage.
• The cyst is the dormant protective stage.
• Protozoans are classified by movement.
• Ameboids use pseudopods, ciliates have cilia, and flagellates have flagella.
• Sporozoans only have motile structures in the gamete stage.
• Reproduction is often done asexually during binary fission.
• Some protozoans reproduce asexually with schizogony, and then sexually with gametogony.
• High rates of infection are common.
• Most infectious protozoans are facultative anaerobes and heterotrophs, and some have highly-developed reproductive systems.
• Cysts protect the protozoans, and enable spread between hosts.

Parasitic Helminths: Morphology and Pathogenesis

• Helminths are worms with flat, cylindrical, or elongated bodies ranging 1mm-10+mm in length.
• Helminths have a tough cellular cuticle that can be smooth, possess, ridges, spines or nodules..
• The anterior end has suckers, plates, or hooks for attachment.
• Helminths have primitive nervous and excretory systems.
• Highly developed reproductive systems, but no circulatory system.

Three Classes of Helminth

• Nematodes (roundworms) have a gastrointestinal form, which uses one life cycle host, and a blood and tissue form, which uses multiple to complete their life cycle.
• Cestodes (tapeworms) have a flat, ribbon-shaped body and a head with hooks for attachment.
• Cestodes create proglottids which are reproductive segments with male and female gonads.
• Cestodes absorb nutrients across their cuticle since they have no digestive tract.
• Some cestodes use one host while others use one or two in their life cycle.
• Trematodes (flukes) have a leaf-shaped body and two suckers.
• The oral sucker takes in nutrients and excretes waste.
• The distal sucker facilitates attachment.

Life Cycles and Transmission Pathways of Protozoans and Helminths

• Life cycles and transmission varies depending on the organism.
• Parasites use single or multiple hosts to complete their life cycle.
• Single host parasites complete their life cycle in one host, relying on their environmental endurance for transmission.
• Multiple host parasites use definitive hosts, where sexual reproduction happens, and intermediate hosts, where asexual reproduction happens.

Malaria (Plasmodium Species)

• Malaria, caused by Plasmodium, is a febrile illness from parasitic infections of human red blood cells.
• Malaria is found throughout the world, usually in warmer climates.
• Malaria is transmitted via the bite of the Anopheles mosquito.
• Malaria spread depends on density and feeding habits of mosquito vectors.
• Mortality is high among children and immunocompromised adults.

Plasmodium Life Cycle - Sexual

• Female mosquitoes ingest male and female Plasmodium gametocytes from infected blood.
• Male gametocytes fertilize female gametocytes in the mosquito's gut.
• A zygote is formed, which becomes an oocyst, which is where sporozoites are formed.
• The oocyst bursts, releasing sporozoites into the body of the mosquito.
• Sporozoites penetrate salivary glands of the mosquito.
• The Plasmodium sexual cycle lasts 1-3 weeks, depending on humidity and temperature.
• Warmer climates accelerate the Plasmodium sexual cycle.

Plasmodium Life Cycle - Asexual

• The asexual cycle begins when an infected mosquito bites a new host.
• Sporozoites enter the host with the mosquito saliva.
• Sporozoites move to the liver and attach to hepatocytes
• Inside the hepatocytes, each sporozoite produces 2,000 to 40,000 daughter cells called merozoites.
• Infected hepatocytes rupture and release merozoites in two weeks.
• Merozoites then infect red blood cells (ring stage)

Plasmodium Completion

• Infected red blood cells rupture within 72 hours and release merozoites.
• Merozoites infect other red blood cells, while some transfer into the gametocyte form.
• Gametocytes are then taken up during the next mosquito bite.

Pathogenesis of Malaria

• Symptoms are Fever, hallmark of malaria, is initiated from the rupturing of RBC's.
• Anemia is caused by the destruction of red blood cells.
• Depression of marrow function and an enlarged spleen is accompanied by anemia.
• Hemoglobinuria is due to severe destruction of red blood cells, creating dark urine.
• Circulatory changes include hypotension due to the blood vessels dialating from high fever.
• Thrombocytopenia is common from the decreased life span of platelets.

Malaria Cycling

• Malaria has a two-week incubation period, with clinical signs depending on the Plasmodium species.
• Cold, hot, and sweating stages make up malarial paroxysm.
• The cold stage causes body to drop below normal temperature for approximately 20-60 mins, shaking and chills occurs.
• The hot stage increases body temperature range from 3-8 hours, chills and shaking subside.
• The sweating stage causes profuse sweating for about 2-4 hours, fever drops and exhausted feelings for patients.
• Recurring hot and cold stages cause exhaustion in patients.
• Paroxysms are synchronized by the third week.
• Irregular intervals of paroxysms happen during weeks 1-2 with a parasite population with different developmental stages.
• Regular intervals of paroxysms happens during week 3+ when parasite populations have reached the mature stage.
• Disappearing parasites in the blood results in diminishes and disappears paroxysms.

Malaria Treatment

• The species of plasmodium and the immune status of the host need to be considered for treatment.
• Successful treatment needs to destroy all parasite forms.
• Breaking the parasite transmission cycle is done through medicine.
• Artemisinin-based combination therapy is the best current treatment.
• Chemoprophylaxis is used to complement routine malaria control measures such as vector control.
• In 2021, the WHO recommended transmission Plasmodium vaccine for children in regions of high.

Toxoplasmosis (Toxoplasma Gondii)

• Toxoplasma gondii is an obligate intracellular sporozoan that requires a host.
• The definitive host is the domestic cat. Transmission happens through ingested fecal oocysts, eating undercooked meat, or unwashed fruit.

Toxoplasma Life Cycle

• The cycle begins in the intestine of cats as trophozoites enter the ileum's epithelium cells.
• Trophozoites undergo merozoite schizogony which cause epitelial cells to rupture, releasing the parasites.
• Merozoites differentiate into female and male gametocytes, starting gametogony, and creating oocysts.
• Oocysts are typically released in 2-3 weeks and remain stable for months in the external environment.
• Form sporozoites are made during the maturation event.
• When human are their intermediate hosts it means that they have ingested the Mature oocysts
• Next will occur releasing the Sporozoites are then released from oocysts
• After that Sporozoites enter into macrophages and travel to all organs and the Macrophages rupture releasing the new parasites
• Then another asexual cycle starts

Toxoplasma Resilience

• Trophozoites are resilient in the heart, skeletal muscles, and brains.
• Each cyst can hold 1000+ organisms persistent for a hosts lifetime.

Pathogenesis of Toxoplasmosis

• Primary infection occurs via trophozoite proliferation, leading to cell death and triggering an immune response in the host.
• This immune response keeps infections limited, which causes mild symptoms.
• Immunocompromised patients who experience constant tissue death, may have delayed or reduced immunity.
• Serious illness can then lead to inhibiting cell-mediated immunity, which overactivates host defenses.
• Treatment includes pyrimethamine and sulfonamides

Trypanosomiasis (Trypanosoma Species)

• Trypanosomiasis is caused by transmitted by insect vectors and is caused by the flagellated protozoan Trypanosoma.
• The African form, which causes sleeping sickness, is caused by the tsetse fly and Trypanosoma brucei.
• Less than 1000 cases of African Trypanosomiasis are reported yearly due to control efforts, but humans still remain a reservoir.
• The American form. which causes Chagas disease, is spread by the kissing bug and Trypanosoma cruzi.
• Most cases of the American from are found in Latin America.

Life Cycle of Trypanosoma

• All species reproduce by binary fission, cycling from insect to humans.
• It multiplies extracellularly and can invade blood in mammalian hosts.
• Exhibits the ability to switch antigens for its defense.
• They can express hundreds or dozens so it makes it difficult, for the host's immune system to respond effectively.

Pathogenesis of Trypanosomiasis

• Trypomastigotes deposit Trypanosomiasis during the bite of the vector and begin multiplying causing localized inflammation.
• A chancre, followed by dissemination to blood and lymph causes swollen lymph nodes and recurrent parasitemia.
• The host responds by producing antibodies to destroy the parasite, but it reappears 3-8 days later with different markers that become progressively less frequent but can last for years.
• Hemorrhage, inflammation, and degeneration are common when they get to the brain.

Parasitemia

• Trypomastigotes localize in the small parts of blood vessels and affect the central nervous system during parasitemia.
• The condition can lead to hemorhage, inflammation, , impairment of mental function and degradation in the brain.
• During recurrent bouts of parasitemia, a patient may also experience skin rash, headache, lymph-node-tenderness and impaired mental status.
• Occasional bouts of fever lasting for years can lead to gradual problems and cause alertness, wavering attention, tremors, speech problems and loss of sphincter control in the CNS.
• If not treated Coma and death can occur

Treatment Of Trypanosomiasis

• If the CNS is involved: agents that can cross the blood-brain barrier are needed.
• Only Melarsoprol is arsenic compound and only used with in CNS is involved but is very toxic.
• May trigger complications such as encephalopathy, gastrointestinal issues, hypertension kidney and liver damage , peripheral neuropathy and convulsions.
• If there is no CNS involvement: Pentamidine or eflornithine is needed which cause less severe side effects.

Helminthic Infections: Nematodes

• Nematodes are a type of roundworm separated into 2 sub-groups.
• Intestinal nematodes live within the intestines of their hosts (animals and Humans).
• Fusiform body, tough cuticle, male and female forms with the to make offspring is their characteristic.
• Tissue nematodes live within tissues,blood, , and lymph systems of hosts that Humans are the definitive host.
• Can survive for years is also their attribute that and live in lymph vessels and subcutaneous tissues.

Intestinal Nematodes

• Nematode infection can trigger malnutrition, discomfort, anemia, or occasionally death.
• Symptomatic disease is directly correlated to large worm load due to the small is normally normally asymptomatic.
• Host immune defenses are known be slow to develop.

Enterobiasis (Enterobius Vermicularis)

• Pinworm is a ubiquitous parasite of humans.
• More than 200 million people are infected.
• Most of these infections are in children.
• It readily transmitted where large numbers of children because nurseries, child care facilities, and orphanages and it is most common in temperate climates is found in Europe and North America.

Pathogenesis of Enterobiasis

• Enterobiasis can be spread by ingesting that can be the eggs and then are swallowed or inhaled that they are there in perianl that happens due the the uncleaned hands.
• Eggs hatch in the upper intestine then the larvae travels to the large intestine.
• Females then migrate down the colon and through the anal canal.
• The eggs then deposit 20,000 sticky eggs to the area nearby and the eggs can off onto bedsheets or clothes.
• They can because once they are exposed to the air and this cycle only happens in just 2 weeks.
• Itching is the main anal symptom because eggs adhere to the fingers, they make them self-infection orally.
• Scratching can also lead to cause a bacterial Infection and the eggs can be skaen into the air and inhaled and swallows always.

Treatment of Enterobiasis

• Safe effect treatment include mebendazole and pyrantel which are pamoate.
• Sanitation is crucial because recurrence is common.

Ascariasis (Ascaris Lumbricoides)

-Largest intestinal nematode can develop to just 40 cm.

• Female to produces 250,000–500,000 eggs daily but it resistant against most environments
• They can picked up form soil, and then contaminate food, and swallowed (when eggs dry out), and is easily is easily transmitted because is infection a small kid's play is kept for mature soil pick eggs, and so they have easy maintaining infections like eggs.

Ascaris Life Cycle

• The adult is in a small intestins and the it passes its eggs via faces for like 3 weeks to infect so a human.
• There is this larvae that is inside the eggs that needs to penetrates intestinal mucosa and go to invade the invade also.
• This larvae exits the is a Exit liver goes trought the hepatic vein then goes to the heart and progress to the Lung
• and this Larvae can rupture into the alveolar spaces and the Coughed arrive the intestine.

Pathogenesis of Ascariasis

• If a low worm load in found, Infections can be asymptomatic but If there is a symptoms they can range from fever Coughing Wheezing Shortness of breath.
• Other Prolonged infection can cause heavy worm loads . so Malnutrition Abdominal pain ,and Obstruction the bile and, ducts can show as serious problems.

Ascariasis Infection

• During infection Worms can exit throw the Vomiting, stools and they can move out of anus, nose, mouth, and ears
• They are then treated throw Albendazole, and or Mebendazole

Cestodes

• Largest tapeworm of the are parasitic Largest of the species lack a vascular and the, are lacking a gut or, but absorb nutrients across the ,They are not air , so they must the and but lack air the, are air or and but absorb air and.
• The adult body has three sections include , which is Head the (scolex) which is and or neck, but its mostly a.

Cestode Reproduction

• Proglottid units and the are the of unit units as as are the sexual sexual are air eggs at the end are are as

• host and they must and at at and all

Cestode Infection

• The degree and type if patient is intermediate to high and this then affects the how symptoms will show.
• Symptoms are Stays in the lumen as if Stays in the lumen as if the but the Stays there the, that and.
• If there is then we have to see
• If Taenia that and the then will.

Trematodes (Flukes)

• Main characteristics Ο Have a bilateral symmetry Ο Have two deep suckers: One in the oral cavity One on the ventral side of the worm

Trematodes (Survival)

• Trematodes can live decades and that make organs a is as at.

Trematodos Types

• Hermaphrodites Schistosomes.

Life Cycle Of Trematodes

• Eggs are excreted from the human host they MUST Reach the in water to hatch.
• Eggs have release they hatch water they then can is at .
• Snails become infects the they (Intermediate to host).
• Cercarie, form this when then they then this makes what, cercarie these can is is that for is at and can.

###Hermaphrodites Traits

• The hermaphrodites are to, with animal when and you you animal animal water.
• Develop when eat that
• And as eat.

Schistosomes Traits

• Cercariaet are invade of

Clonorchis(Traits)

• The host needs to Utilized 3 hosts.
• The infection it is at
• Larvae into the and
• . The liver and (after 30 days
• Eggs pass and the is into .
• They also to can.

Clonorchiasis Treatment

• Larvae from from from can can is be
• Adult from The is, infection can be high it is then can
• . Lead then then high then high.

Trematode Infection

• The adults and (the most), and