Human Health and Disease – Immunity, Pathogens and Prevention

Fifteen question-and-answer flashcards reviewing key pathogens, symptoms, hygiene measures, immunity types, vaccination principles and modern vaccine production techniques.

What parasite causes ascariasis, and how does a person typically become infected?

The roundworm Ascaris lumbricoides; infection occurs by ingesting food or drinking water contaminated with its eggs from faeces-polluted soil.

Name the two filarial worms that cause elephantiasis and state the vector involved.

Wuchereria bancrofti and Wuchereria malayi; they are transmitted through the bites of female mosquitoes.

Which three fungal genera are chiefly responsible for human ringworm infections?

Microsporum, Trichophyton and Epidermophyton.

What are the characteristic symptoms of a ringworm infection?

Dry, scaly, intensely itchy lesions on the skin, nails or scalp, especially in warm, moist skin folds.

State two personal hygiene measures that help prevent water- and food-borne diseases such as typhoid and ascariasis.

1) Keeping the body clean, 2) Consuming clean drinking water, food, vegetables and fruits.

Give three practical mosquito-control methods to curb diseases like malaria, dengue and filariasis.

Avoid stagnation of water near homes, use mosquito nets or window screens, and introduce larvivorous fish such as Gambusia or spray insecticides in breeding sites.

Define innate immunity and list its four categories of barriers.

Innate immunity is the non-specific defence present from birth; its barriers are physical, physiological, cellular and cytokine barriers.

Which leukocytes perform phagocytosis as part of the cellular barrier of innate immunity?

Polymorphonuclear leukocytes (neutrophils), monocytes, tissue macrophages and natural killer (NK) cells.

Describe the basic structure of an antibody molecule.

An antibody consists of four peptide chains—two identical heavy (H) chains and two identical light (L) chains—forming an H₂L₂ structure.

Differentiate humoral immunity from cell-mediated immunity (CMI).

Humoral immunity involves B-lymphocytes producing circulating antibodies, whereas CMI is mediated by T-lymphocytes that act directly on infected or foreign cells and cause graft rejection.

Why must tissues be matched before organ transplantation?

Because the cell-mediated immune response recognises non-self tissues; without adequate matching, T-cells will attack and reject the graft.

Contrast active immunity with passive immunity and give one example of each.

Active immunity develops after antigen exposure (e.g., polio vaccination); passive immunity is conferred by transfer of ready-made antibodies (e.g., tetanus antitoxin injection or IgA in colostrum).

What immunological principle underlies vaccination?

Vaccination introduces antigenic proteins or weakened/inactivated pathogens to create memory B- and T-cells so the body mounts a rapid, strong response on subsequent exposure.

Identify one disease eradicated through vaccination and two others that have been significantly controlled.

Smallpox has been eradicated worldwide; polio and diphtheria have been largely controlled.

How has recombinant DNA technology enhanced vaccine production? Provide one example.

It enables large-scale, safe production of antigenic polypeptides in microbes; for instance, the yeast-derived hepatitis B vaccine.