Parasites and Protozoa Classification

Parasites

• Parasites live in or on a host organism, benefiting by deriving nutrients at the host's expense
• Parasites are categorized into parasitic protozoa and parasitic helminths
• Protozoa are unicellular, microscopic eukaryotes that can be free-living or parasitic
• Protozoan parasites are classified into four groups based on means of locomotion and reproduction
• Protozoa multiply in humans, enabling serious infections from a single organism
• Intestinal protozoa transmit via the fecal-oral route through contaminated food, water, or person-to-person contact
• Blood or tissue protozoa transmit via arthropod vectors like mosquitoes or sandflies

Protozoa Classification

• Parasitic protozoa are classified into Sarcodina (ameba), Mastigophora (flagellates), Ciliophora (ciliates), and Sporozoa

Amebae

• Amebae have an ameboid shape and move using pseudopodia or protoplasmic flow
• Common species include Entamoeba, Naegleria, and Acanthamoeba

Flagellates

• Flagellates have one or more whip-like flagella
• They sometimes have an undulating membrane (e.g., trypanosomes)
• Giardia and Trichomonas are intestional
• Trypanosoma and Leishmania are blood and tissue flagellates

Ciliates

• Ciliates are complex protozoa bearing cilia in rows or patches
• Ciliates have two kinds of nuclei (micro and macro)
• Balantidium coli is the only representative human parasite

Sporozoa

• Sporozoa undergo a complex life cycle with alternating sexual and asexual reproductive phases
• Human parasites include Cryptosporidium, Cyclospora, and Toxoplasma, and malarial parasites (Plasmodium)

Key Concepts, Parasitic Protozoa

• Parasitic protozoa are grouped into flagellates, amebae, sporozoa, and ciliates
• Flagellates and amebae multiply by binary fission; sporozoans reproduce by merogony/schizogony
• Sporozoans undergo sexual recombination, leading to genomic and antigenic variation
• Protozoa multiply quickly, causing rapid symptom onset
• Intestinal infections are acquired by ingesting environmentally resistant cysts/oocysts; blood infections are vectorborne
• Intracellular protozoa infections are difficult to treat as drugs must cross membranes; vaccines are unavailable
• Latent infections occur with Toxoplasma (bradyzoites in tissue cysts) and Plasmodium vivax and P. ovale (hypnozoites in liver)
• Disseminated protozoal infections cause nonspecific fever and flu-like symptoms
• Protozoa evade host immune responses through intracellularity or antigenic variation

Intestinal Protozoan Infections

• Giardia lamblia causes giardiasis: it is a common pathogenic protozoan in the human duodenum and jejunum
• Giardia lamblia exists in trophozoite and cyst forms.
• A heart-shaped organism with four pairs of flagella, and a ventral concave sucking disk which adheres the organism to intestinal villi
• The organism encysts in the colon and is passed in the stool and can survive 3 months in water
• Giardia lamblia is usually only weakly pathogenic, where the cysts may be found in large numbers in the stools of entirely asymptomatic persons.
• Giardia is found worldwide
• Entamoeba histolytica cysts are present only in the lumen of the colon, and range in size from 10 to 20 μm
• Disease results when the the amoeba trophozoites invade the intestinal epithelium forming discrete ulcers which may coalesce and create lesions
• Diagnosis rests on the characteristics of the cysts
• Symptoms vary greatly based on the site and intensity of lesions.
• There are estimated to be of invasive disease 50 million cases with up to 100,000 deaths each year worldwide

Comparison of Intestinal Protozoa (Site, Mode, Diagnosis, Treatments and Geographic Area)

• Giardia lamblia (flagellate): infects the small intestine, mode is ingesting cysts in water (not killed by normal chlorination), diagnosis is by stool exam or EIA for antigens, Ubiquitous
• Entamoeba histolytica (amoeba): infects the colon, mode is ingesting cysts; stool exam or EIA for antibodies and antigen, treats with lodoquinol, Globally
• Cryptosporidium (sporozoa): infects small intestine, mode is ingesting oocysts; stool exam/acid-fast staining, treats with Nitazoxanide , ubiquitously
• Cyclospora (sporozoa): infects small intestine, ingests oocysts from food, stool exam-acid-fast staining, treats with Trimethoprim/sulfamethoxazole, globally

Sexually Transmitted Protozoan Infection

• Trichomonas vaginalis is a genitourinary flagellate
• It exists only as a Trophozoite
• Trichomonas vaginalis is approximately 20 µm in length and 10 µm wide.
• Most infections are asymptomatic or mild for both women and men, though in women the infection is typically limited to the vulva, vagina, and cervix
• In men, the prostate, seminal vesicles, and urethra may be infected, and approximately 10% of infected males experience a thin, white urethral discharge.
• The incubation period is 5 to 28 days
• The infection is sexually transmitted but can also spread through towels and exam equipment
• Treatment is Metronidazole for both partners and use of physical barriers

Blood and Tissue Protozoan Infections - Hemoflagellates (Disease, Vector and Stages)

• Trypanosoma brucei rhodesiense: African sleeping sickness , transmitted by tsetse fly, characterized by trypomastigotes in blood
• Trypanosoma brucei gambiense: African sleeping sickness , transmitted by tsetse fly, characterized by trypomastigotes in blood
• Trypanosoma cruzi: Chagas disease, transmitted by kissing bug, characterized by trypomastigotes in blood
• Leishmania spp. Cutaneous leishmaniasis, transmitted by Sandfly, characterized by Amastigotes within macrophages

Trypanosoma brucei rhodesiense and T B gambiense

• Trypanosoma brucei rhodesiense and T B gambiense are introduced through the bite of the tsetse fly , multiplying at the site of inoculation to cause variable induration and chancre
• The African forms multiply extracellularly as trypomastigotes in the blood
• This pathogen spread to the limbs and the CNS , producing sleeping sickness
• African trypanosomiasis is restricted to recognized tsetse fly belts with focus in west to central Africa

Leishmania donovani

• The Sandfly promotes Rapid change to Amastigotes after phagocytosis by macrophages
• This process is repeated until a Lesion or Visceral Infection with a range of clinical groupings including cutaneous, mucocutaneous , and visceral leishmaniasis'
• The disease is particularly present tropical and subtropical regions and territories, and an estimated 12 million people are currently infected with the parasite
• Leishmania donovani is common found in tropical and subtropical countries, with its dissemination being related to the prevalence of flies

Comparison of Blood Flagellates regarding (Parasite mode of infection diagnosis treatment)

• Trypanosoma brucei: The tsetse fly transmits causes lacerations on on the human skin allowing for for the Trypomastigotes to be released (diagnosed through observation of blood and lymph) can be given treatment with suramin
• Trypanosoma brucei gambiense: The tsetse fly lacerats skin and releases trypomastigotes (diagnosed through examination of blood and lymph) can be treated with Pentamidine and Eflornithine
• Trypanosoma cruzi: Transmitted through kissing bugs feces being rubbed to the bite or blood transmission (Diagnosed though detection of trypomastigotes in fluids or a PCR test gives the option through Benznidazole treatment
• **Leishmania (Blood flagellates) ** injects promastigotes by sandflies then colonizes in monocytes (diagnosis is histopathology and PCR of the organisms) can be treated with Stibogluconate sodium

PLASMODIUM SPECIES

• Plasmodium causes malaria from the species Plasmodium vivax, P falciparum, P malariae, and P ovale
• P vivax and P falciparum are common, with falciparum being the most pathogenic.
• Transmission to humans involves female Anopheles mosquitoes inject sporozoites into the bloodstream

The Plasmodium Species

• Plasmodium vivax, P malariae, and
• P ovale parasitemias are relatively low grade, primarily because the parasites favor either young or old red cells, or not both
• Plasmodium falciparum: invades all red cells, so parasitemia is very high and produces knobs adhering to blood vessels, causing obstruction, thrombosis, and local ischemia, severe complications leading to cerebral malaria, malarial hyperpyrexia, gastrointestinal disorders and blackwater fever.

Stages and Malaria Symptoms

• Periodic paroxysms of malaria are closely related to events in the bloodstream
• Characterized as; An initial chill 15-60 minutes begins as a synchronously dividing parasites rupture and escape into the blood Nausea, vomiting, and headache are common at this time.
• The succeeding febrile stage (2), last several hours, is characterized by a spiking fever reaching 40°C During this parasites invade new red blood cells. The third, or sweating (3), stage concludes the episode.
• The fever subsides, and the patient falls asleep and later awakes feeling relatively well.
• In the early stages of infection fever fluctuates
• As the disease progresses, splenomegaly more common to a lesser extent, hepatomegaly appear.

Sickle Cell Anemia and Malaria

• People with the sickle cell trait are healthier with one normal hemoglobin gene and one sickle cell gene, they show low chance with malaria
• People with the Double dose of the sickle cell gene show a high chance of blockages and is worsened by infection

Helminths (Metazoa)

• Parasitic helminths are animals included into microbiology because these worms are identified by microscopic eggs and larvae.
• As animals, they are multicellular with the exception of certain organ systems
• Their ability to cause limited digestive tracts, nervous systems,
• Helminths are categorized into nematodes and platyhelminthes
• Large, multicellular organisms visible to the naked eye in their adult stages
• Like protozoa, helminths can be either free-living or parasitic
• Adults cannot multiply in humans and instead use other transmission mechanisms
• Parasites are intestinal , where their disruptions allow them obtain nourishment from the loss of normal gut absorptioon.

Helminth Infection Reproduction

• Organisms usually live inside the hosts intestine, where they produce , eggs that release with the feces
• Then eggs become infective, in area of contaminated that lack proper sanitization systems
• The mature to egg while still in the additional stages within the life style
• After this they will enter the mucous mebrane and continue with the rest of the life style.

Nematodes

• Among the most diverse , among the animal kingdoms
• They have longitudinal muscles that are elongated and tapered which allows them to move in whiplike movement.
• They can ingest gut contents , cells or blood with there adapted digestive systems
• The species are separate-sexed
• The species have thick layers molting, and larvae well suites in the external enviroment . Most human nematodes ingest eggs and through insect transmission.

Platyhelminthes

• Platyhelminthes are dorsoventrally flattened animals and are hermaphroditic
• Two clases include Trematoda and Cestoda

Trematoda (Flukes)

• Trematodes are also flattened and leafs shapted with two muscular suckers
• They possess a both circular and longitudinal muscles having both sexes , (schistosomes are the exception)
• The life cycle is initated by contamination to water, that release a ciliated miracidium that then infects a snail
• This leads to sporocyst that develop into germinal that are swim out from the snail and are the cercariae. and encysted as metacercariae

Cestoada (TApeworms)

• Flat chain like segments including the reprodutive structures
• Tape worms can reach 10+ M's can lead to 100S" of 1000's Of eggs
• Anterior end of adult tapewormis the the scolex or hooks that help attach and directy absorb nutrients through the integument.
• The cycles are indirect with eggs eaten and eaten into the second host who are eaten

Intestinal Helminthic Infections

• 1.5 billion people are infected with roundworms, 800. Million with whip and 1.3 hooked worms
• Most intestinal heminthac infections can are fairly benign high worm presence
• Nematode infection , human and sanitation contributes greatly

Enterobius vermicularis (Pinworm)

• Female pinworms have a pointed end and 10 mm in length.
• Common to find this in the US and its high contagious in Children
• Main reaction from the infection is perianal Pruritus especially at at night when they move down
• Anal itching promotes the transmission

Scotch Tape Test

• The scotch tape test helps diagnose the tape worms
• It is a stickly test performed in the Anal region under a microscope, and is non-invasive making it easy and effective .

Ascaris lumbricoides (Human roundworm)

• Adult Ascaris is very long (20+cm). they acquire the infection after the eggs are infested and lodge in the lung after swallowed again
• Females are found to released 200K"s A DAY

Anclystomas

• Females are about 10mm in length
• Release 10K's of eggs perday of faces where larvae hatches.
• Can infect an unsuspecting host

Trichuris trichiura (Whipworm)

• Females are nearly 50+ millmeter
• They release by eating contaminates

Taenia saginata/solium (Beef/pork Tapeworm)

• Cyctceri and leads to adult worms
• Eggs consumed by cows
• Humnas ingest food with cysts It can cause nereve damage

Taenia pathosgenes and cycle

• difference between T saginata and T solium is that humans can be the intermediate host for T solium
• This can result in Cystycosrsis and can be dettermental
• T sagniata and Tape worms adults can devolve in cattle

Wulcheria

• Slnder worms (129 million in other regions)
• Mosuquito vector

Oncocherceriasis (River Blidnness)

• The who calculates that more than 170 million people and has 20700K Blinded by the pathigen