Parasitology

What is parasitology

The study of interactions between parasites and their hosts

What is a parasite

An animal that lives in or on the body of another organism and gains an advantage from the host

What are the two main types of parasites

Ectoparasites (live on the surface of the host) and endoparasites (live inside the host)

What are examples of ectoparasites

Lice and mites

What are examples of endoparasites

Malarial parasites and threadworms

What are the two zoological classes of ectoparasites

Insects (three-segmented bodies) and arachnids (four pairs of legs)

What are the two types of endoparasites

Protozoa and helminths

What are the characteristics of protozoa

Microscopic, single-celled organisms that can multiply within the host and are transmitted via the fecal-oral route or vectors

Where do protozoa live in the human body

Some live in the bloodstream and are transmitted by vectors like mosquitoes or sandflies

What are helminths

Parasitic worms that infect the gastrointestinal tract and can be transmitted through soil

Who is at the greatest risk of helminth infections

Immigrants and refugees from endemic countries

What are examples of helminths

Roundworms, hookworms, and whipworms

What are the five main causes of parasitic infections

Animals (zoonotic diseases), blood, food, insects, and water

How can animals transmit parasites

Through contaminated food or water, or direct contact with pets that may be carriers

How can parasites be transmitted through blood

Via blood transfusions, shared needles, or insect vectors like mosquitoes

What are examples of vector-borne diseases

Leishmaniasis, malaria, and toxoplasmosis

What are common foodborne parasites

Cryptosporidium and Giardia intestinalis

How can foodborne parasites be transmitted

By consuming undercooked meats, raw vegetables, or food handled with poor hygiene

What are mechanical vectors in insect-borne transmission

Insects that carry parasites but are not necessary for the parasite’s life cycle

What are examples of insect-borne parasitic infections

Leishmaniasis and malaria

What are common waterborne parasitic diseases

Guinea worm disease, schistosomiasis, amebiasis, cryptosporidiosis, and giardiasis

How can waterborne parasites be transmitted

By drinking contaminated water, swimming in infected lakes, or coming into contact with infected water sources

What are recreational water illnesses (RWI)

Diseases spread by swallowing, breathing, or contact with contaminated swimming pools, lakes, or hot tubs

What is the most common symptom of RWIs caused by parasites

Diarrhea

What are common diagnostic methods for parasitic infections

Fecal stool exams, blood tests, imaging (X-ray, MRI, or CT scans)

What do fecal stool exams detect

Parasite eggs (ova) or the parasite itself

How can blood tests help diagnose parasitic infections

Through serology (antibody detection) or blood smears for parasites in the bloodstream

What are lice

Ectoparasites that suck blood from their host

How do lice feed

Their mouths are specialized for piercing skin and sucking blood

What are the three species of lice

Pediculosis capitis (head lice), Pediculosis corporis (body lice), Pediculosis pubis (pubic lice)

Who is most at risk for lice infestations

People in crowded conditions such as homeless populations, refugees, and survivors of disasters

How are body lice transmitted

Through clothing-to-clothing contact or direct skin contact

Where do body lice lay their eggs

In the seams of clothing

Why do body lice cause intense itching

Their saliva is injected into the skin, triggering an allergic reaction

What are potential complications of body lice infestations

Secondary bacterial infections, thickening and discoloration of skin, and transmission of diseases like trench fever and typhus

How are body lice treated

With insecticides, hygiene measures (bathing, washing clothes at 50°C, vacuuming mattresses), and isolating contaminated clothing for two weeks

What are pubic lice commonly known as

Crabs

How are pubic lice transmitted

Through close contact, including sexual contact, and sometimes via clothing or bedding

What are symptoms of pubic lice

Itching, inflammation, tiny blood spots, nits attached to hair, and blue-colored spots where lice have fed

What is the treatment for pubic lice

Insecticides like permethrin 5% dermal cream or malathion 0.5% liquid, plus hygiene measures like washing clothing and bedding at 50°C

Who should be referred for pubic lice treatment

People with lice on eyelashes

How are head lice transmitted

By head-to-head contact

How long do head lice live

Around one month

How many eggs do female head lice lay per day

5-6 eggs per day

How long does it take for a louse to mature from egg to adult

About 10 days

What is a nit

An empty white eggshell stuck to the hair, not removed by treatment

Why do some people experience itchy scalps with head lice

Itching is often an allergic reaction to louse saliva, not the bite itself

What are the main detection methods for head lice

Wet hair combing and dry hair combing

What are physical insecticides used for head lice

Dimeticone-based products (Hedrin, NYDA, Linicin Lotion) and isopropyl myristate solutions (Full Marks, Vamousse)

What is the mechanism of action of dimeticone for head lice

It blocks the lice’s breathing tubes, leading to suffocation

What is the mechanism of action of isopropyl myristate for head lice

It dissolves the lice’s waxy exoskeleton, causing dehydration and death

What are chemical insecticides used for head lice

Malathion 0.5% aqueous liquid (Derbac-M)

What is the alternative to insecticides for head lice

Wet combing with the Bug Buster Kit

Who should use wet combing as the first-line treatment for head lice

Pregnant/breastfeeding women, children under 2 years old, and those with asthma or eczema

What is scabies

A pruritic skin condition caused by mites that burrow into the skin

How is scabies transmitted

Through direct skin-to-skin contact

What is the difference between classical and crusted scabies transmission

Classical scabies requires direct contact, while crusted scabies can spread through contaminated bedding and clothing

What are symptoms of scabies

Intense itching, rash, burrows in the skin, and worsening symptoms at night

What are first-line treatments for scabies

Permethrin 5% cream (Lyclear) and malathion 0.5% (Derbac-M)

What medication is used for treatment-resistant or crusted scabies

Ivermectin (oral tablet)

What is threadworm

A parasitic worm (Enterobius vermicularis) that commonly infects the intestines

How is threadworm transmitted

Primarily via the fecal-oral route, but also through retroinfection or inhalation of eggs

What are symptoms of threadworm

Night-time perianal itching and visible white thread-like worms in stool

What is the first-line treatment for threadworm

Mebendazole (Ovex or Vermox), a 100 mg tablet or suspension

Who should be treated for threadworm in a household

The entire household, even if only one person is symptomatic

Who should avoid mebendazole treatment

Pregnant and breastfeeding women