Eukaryotic Pathogens: Helminths

What are Helminths?

Worms (Flat- like tapeworms & Round- Egg infective & Larvae infective)

Host susceptibility

Pathogenesis Direct & Indirect damage

Direct Damage

• Blockages (worm size, migration, granulomas (mass of inflamed tissues)

• Pressure

• Tissue necrosis, migration, turnover

Indirect damage

• Inflammation

• Hypersensitivity

• Mucosal Changes

They have…

Little to no digestive system

Very simple nervous system

Little or no means of locomotion

A complex reproductive system, sometimes with multiple hosts (definitive and intermediate)

Flatworm characteristics

Roundworm Characteristics

Arthropods as Vectors (Kingdom, Phylum Class)

Arachnids: Ticks & Mites. 4x legs

Insects: Fleas, Lice, Flies, Mosquitoes, Kissing bugs. 3x legs

Ticks, Mites, Fleas & Lice (What do they feed on & symptoms)

Ticks

• Epidermal parasites

• Feed mainly on blood

• May cause anaemia, dermatosis, paralysis, otoacariasis and

  other infections (transmit viral, bacterial, protozoan and helminth pathogens)

Second only to mosquitoes in the number of diseases they transmit

Mites

• Feed on skin debris or suck lymph

• Some burrow into the skin, some live in hair follicles, and some in the ear canals

• E.g. Scabies (burrows into skin and lays eggs- direct contact)

Fleas

• Larvae are not parasitic but feed on debris associated mainly

  with bedding

• Adult stages are parasitic and feed on blood

• Most fleas are not associated with humans but a few do feed

  on humans

Plague is the most significant disease transmitted by fleas

Lice

• Sucking and chewing varieties

• Parasites that can also transmit disease

• Most common among poor or overcrowded communities

Flies, Mosquitoes, Kissing bugs (What do they feed on & symptoms)

Flies

• Among the most common insects

• Those that transmit disease are generally bloodsuckers

• Both adults and larvae may be parasitic

• Cholera

• E.g. Bot fly (Parasitic to mammals), intense pain.

Mosquitoes

• Most important arthropod vector of disease

• Carry some of the world’s most devastating diseases

Kissing bugs (Triatominae)

• Feed on blood nocturnally near the mouth of their human hosts

• while the host sleeps

Scabies