Medical Parasitology: Hookworm

• Medical parasitology studies animal parasites of humans, which are medically significant and have a public health impact.
• Parasitology is the scientific study of parasites.
• A parasitic infection occurs when a parasite lives in a host.

Infective Stages & Mode of Transmission

• Filariform larva that penetrates the skin.
• Ova: ingestion
• Necator Americanus is a human hookworm.
• The stages of hookworm are the rhabditiform and filariform larva.
• The rhabditiform larva is the feeding stage with an open mouth.
• The filariform larva is the infective stage which is thin and slim, and penetrates the skin.
• Hookworm in humans and animals works the same way from penetration to the habitat.

Signs and Symptoms of Hookworm

• Ground itch is a sign of animal to human transmission.
• Hookworm finds its way to the intestine, its habitat.
• CASH-P (small intestine) relates to Capillaria Philippinensis, Ascaris Lumbricoides, Strongyloides Stercolaris, and Human Hookworm.
• Pig relates to HAS (heart -> lungs)
• HAS (heart -> lungs) relates to human hookworm, ascaris lumbricoides, strongyloides stercoralis.
• Juvenile larva relating to Animal Hookworm, and remains in the skin in the form of creeping eruption
• Cutaneous Larva Mutation (CLM) = animal -> animal.
• Animal Hookworm stays young in the heart and lung.
• Pulmonary Wakana Disease results from animal hookworm.
• Anemia can be a sign of hookworm in the small intestine of oral cavity.
• Parasites suck blood.

Effects of Parasite on Host

• Wuchereria Bancrofti is a tissue nematode that requires a vector.

Types of Parasite

• Pathogenic parasites cause disease with a parasitic effect.
• Commensal parasites do not cause disease.
• E. Histolytica is the most pathogenic amoeba, leading to amoebiasis from contaminated food.
• Cysteine proteinase is a feature of E. Histolytica, that is erratic

Obligate Parasitism

• Obligate parasites can't survive without a host.
• Soil transmitted helminthes are an example of obligate parasites
• Ascaris lumbricoides's ova survives for up to 10 years.
• Human Hookworm, Ascaris Lumbricoides, Trichinella Spiralis, Strongyloides Stercolaris are all obligate parasites

Facultative Parasitism

• Facultative parasites can exist in a free-living state and may become parasitic.
• Strongyloides Stercolaris can be a facultative parasite.

Temporary Parasitism

• Temporary parasitism is obligatory in one or more stages, while free-living in other stages.
• Ectoparasites are temporary parasites
• Babesia Canis (Ticks) is a blood parasite that is a main killer of dogs

Intermittent Parasitism

• Intermittent parasites periodically seek larger forms, visiting the host only during feeding time.
• Vectors are examples of intermittent parasites.
• Anopheles mosquito that transmit protozoan are intermittent parasites. The disease of mosquitos is malaria.
• The scientific name for mosquito is Anopheles Minimum Flavirostris
• Female: Anopheles bites can spread Falciparum, Malariae, Vivax, Ovale, and Knowlesi
• Mosquitoes with type O blood are intermittent parasites.
• Triatoma spp bugs transmit Trypanosoma cruzi, causing Chaga's disease.
• Tsetse flies (Glossina spp) transmit Trypanosoma spp, causing sleeping sickness.
• Sandflies (Phlebotominae) transmit Leishmania, causing Kala-azar.

Types of Parasite: Habitat

• Endoparasites live within the host.
• Ectoparasites live on the surface of the host.

Habitat: Surface

• Nematodes, Cestodes, Trematodes and Protozoan are examples relating to surface habitats.
• Ticks are also examples of surface parasites
• Human and animals are target hosts.

How Parasites Obtain Food

• Predation involves attacking another living organism and consuming part or all of its body for nourishment.
• Scavenging derives nutrition from already dead animals, either by devouring them or taking their leavings.

Types of Parasites: Others

• Permanent parasites remain on the host throughout their life, maturing on the host's body
• Incidental parasites occasionally infect an unusual host.
• Hymenolepis nana (dwarf tapeworm) infecting a rice beetle, with humans as an incidental host.
• Periodic parasites require a vector that is intermittent
• Larval development will be intermittent.
• Transitory parasites go through larval development. During the first snail stage, they become free-living cercaria and then metacercaria.
• Entamoeba histolytica is erratic, because it keeps changing habitats.
• Arthropods are temporary
• Nematodes have 1 DH = 0 IH
• Trichinella spiralis has 1 IH; a pig.
• Trichinella spiralis will then cause encysted larvae on muscle
• Capillaria Philippinensis has 1 IH; fish (glass fish).
• Tissue Nematodes/Filarial Worm requires a vector
• Cestodes: DH = 1 IH except: Dibothriocephalus Latus
• Trematodes: 1 DH = 2 IH except Shistosoma
• MOT relates to Metacercaria and ingestion
• Schistosoma relates to 1 DH = 1 IH; and skin penetration.

Types of Host

• Definitive/Final hosts house the adult, sexually mature form of the parasite.
• Plasmodium falciponum, which causes malaria infection, has asexual reproduction in humans and sexual reproduction in mosquitoes. In mosquitoes, the falciparum becomes gametocyte.
• Intermediate hosts harbor the larval stages or asexual forms of the parasite.
• First intermediate hosts house the early larval or developing stages before becoming infectious (ex: trematode in the IH snail).
• Blood-feeding arthropods include IH: mosquitos, Tse Tse flies, Soundflies, and Triatomid Bugs
• Cestodes include 1 IH.
• Second intermediate hosts house the infective larval stage.
• Snail (other species), fish, vegetable, crabs, and ants are all second intermediate hosts.
• Reservoir hosts are alternative hosts that maintain the parasite's life cycle and provide an additional source of infection. This is a parasite control measure
• Pig relates to balantidum Coli
• Cat relates to Brugia Malayi
• Field bats relate to Paragonimus Westermani
• Paratenic hosts harbor underdeveloped parasites in an arrested state.
• Paratenic hosts transfer the parasites until they are consumed by a susceptible definitive host, where the life cycle will continue.
• Paragonimus Westermani has an infective metacercaria.
• Wild boar is its paratenic host
• Fresh water prawn/crab are the 2nd IH

Vectors

• Vectors transmit parasites from one host to another, sometimes also serving as a host themselves.
• Biological vectors are directly involved in the parasite's life cycle. The development of the parasitic organism occurs on the biological host.
• Development of the parasites must develop on the mosquito before transmitting infection
• Anopheles mosquito is a biological vector.
• They can transmit Elephantiasis, and huge inflammation
• Elephantiasis relates to Wuchereria Bacrofti, crotch area (waist down), and lymphatic inflammation
• It also relates to Brugia Malayi, breast area (waist up), and lymphatic inflammation
• Chyluria = crystal in urine
• Filariasis: Filarial Worm contains 3rd stage (L3)
• Mechanical/Poretic vectors transmit parasites passively, acting as instruments of transfer.
• Fly feeds on fecal matter containing cyst of E. Histolytica
• Transfers to food
• Cockroach can transmit Ascaris

Host-Parasite Relationship

• Host parasite relationship must consider the number of parasites
• *Taenia Solium, known also as pork, can be meters long
• Ascaris Lumbricoides produces 200k egg/female parasite
• Essential part of attachment:
• Cestode = head/scolex w/ body attached
• Trematode = mouth
• Hole breaks downs organs
• Enzyme Secret will also break down organs

Factors Affecting Parasite Transmission

• Source of infection is a factor affecting transmission.
• Trichinella can come from pork.
• Naegleria Fowleri can come from air.
• Draconculus Medinensis can come from water (Red Sea)
• Ingestion = mouth is an effect of mode of transmission / portal of entry.
• Skin penetration = skin is an effect of mode of transmission / portal of entry
• Presceptible host exists within exposure to source of infection / mode of transmission

Soil Transmitted Transmissions

• HAT (acronym)
• Hookworm
• Ascaris Lumbricoides
• Trichinella Spiralis
• All nematodes

Snail Transmitted Transmissions

• Fluke
• Trematodes

Arthropods and Food Animal Transmissions

• Tissue Nematode
• Protozoan
• These infections are vector borne.
• Cestode
• Nematode

Contact Transmitted and Autoinfection Transmissions

• Self
• From other host
• Sexual
• Trichomonas Vaginalis (protozoan) causes CES (both sexes are affected)
• In Trichomonas Vaginalis disease, Male = carrier, Female = infected
• IS: Trophozoite
• *Capillaria Philippinensis is spread via autoinfection.
• Enterobis Vermicularis is ingested or inhaled from touching infected fecal matter.
• Stronyloides Stercularis undergoes internal and external autoinfection
• Route of transmission includes fecal oral, ingestion, and raw meat

Route of Transmission

• Raw meat can be contaminated cyclops
• Types of skin penetration
• Dry
• Wet
• Arthropods:
• Biting: Microfiariae
• Inoculating into Blood: Protozoan
• Sexual/Direct contact
• Pregnant women can survive w/ parasite
• Mother can transmit the parasite via breastfeeding
• The type, number, size, and habitat of a parasite are the type of parasite the body can have. These parasite will also determine the level of maturation they will each present
• Treatment includes chemotherapic agent, surgical infection, and adequate nutrition
• Population at risk from contracting parasite are people in underdeveloped areas or close quarters.
• This also includes refugees, immigrants, foreigners, immunocompromised, and children in day care.