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Questions and Answers
What is the scientific name for the class that includes beetles, flies, and moths?
What is the scientific name for the class that includes beetles, flies, and moths?
Insecta
What is the main characteristic of the exoskeleton of arthropods?
What is the main characteristic of the exoskeleton of arthropods?
Chitinous
Which class of arthropods has two pairs of legs per segment?
Which class of arthropods has two pairs of legs per segment?
Arthropods with venomous fangs belong to the class Chilopoda.
Arthropods with venomous fangs belong to the class Chilopoda.
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Insects have __ distinct body regions: Head, Thorax, Abdomen.
Insects have __ distinct body regions: Head, Thorax, Abdomen.
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Match the arthropod vector with the corresponding disease vector:
Match the arthropod vector with the corresponding disease vector:
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What is the primary mode of transmission for scabies?
What is the primary mode of transmission for scabies?
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Which group is at risk for a more severe form of scabies known as Norwegian or crusted scabies?
Which group is at risk for a more severe form of scabies known as Norwegian or crusted scabies?
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Crusted scabies is characterized by minimal itching.
Crusted scabies is characterized by minimal itching.
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Nodular scabies is characterized by reddish-brown, pruritic nodules on covered parts, most frequently the male genitalia, groin, and __ regions.
Nodular scabies is characterized by reddish-brown, pruritic nodules on covered parts, most frequently the male genitalia, groin, and __ regions.
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Match the complications of scabies with their descriptions:
Match the complications of scabies with their descriptions:
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What is another name for infestation with lice?
What is another name for infestation with lice?
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Which family of lice is known for infesting humans?
Which family of lice is known for infesting humans?
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Human Body lice prefer hair over cloth for oviposition substrate.
Human Body lice prefer hair over cloth for oviposition substrate.
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The Pediculus capitis louse feeds on blood from the ___.
The Pediculus capitis louse feeds on blood from the ___.
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Match the louse-borne pathogen with the correct disease:
Match the louse-borne pathogen with the correct disease:
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What is the skin infestation caused by the microscopic mite Sarcoptes scabei called?
What is the skin infestation caused by the microscopic mite Sarcoptes scabei called?
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How many pairs of legs do adult Sarcoptes scabei mites have?
How many pairs of legs do adult Sarcoptes scabei mites have?
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Scabies can spread rapidly under crowded conditions.
Scabies can spread rapidly under crowded conditions.
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The burrow caused by Sarcoptes scabei mites is known as a ________.
The burrow caused by Sarcoptes scabei mites is known as a ________.
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Study Notes
Arthropods: An Overview
- Arthropods belong to the kingdom Animalia, phylum Arthropoda, and are classified into different classes such as Insecta, Arachnida, Diplopoda, Chilopoda, Crustacea, and Pentastomida.
- Phylum Arthropoda characteristics:
- Metameric body (true segmentation with replication of muscles and nerves)
- Chitinous exoskeleton (nitrogenous polysaccharide)
- Bilaterally symmetrical
- Jointed legs
- Dorsal heart (open circulatory system)
- Ventral nervous system
- Striated muscle
Class Arachnida
- Characteristics:
- 2 body regions or unsegmented
- Without antenna and wings
- 4 pairs of legs
- Stigmata
Class Diplopoda
- Characteristics:
- Two pairs of legs per segment
- Two pairs of spiracles per segment
- Body cylindrical
- Detritivorous
- Can secrete toxic substances (e.g., HCl) as a defense
Class Chilopoda
- Characteristics:
- One pair of legs per segment
- One pair of spiracles per segment
- Body flattened dorso-ventrally
- Carnivorous
- First pair of legs modified as venomous fangs
Class Crustacea
- Characteristics:
- One or two segmented body
- 2 pairs of antenna
- 5 pairs of legs
- Without tracheal system
Class Pentastomida
- Characteristics:
- Segmented slender body
- Without appendixes
Class Insecta
- Characteristics:
- 3 distinct body regions: head (feeding, sensory, CNS), thorax (locomotion, respiration), abdomen (feeding, reproduction)
- 3 pairs of legs
- 1 pair of antenna
- Spiracle
- Exoskeleton
- Segmented; bilateral
- Open circulatory system
- Ventral nervous system
Types of Insect Development
- "A" – (lacking)
- "Hemi" - (incomplete)
- "Holo" - (complete)
Medical Entomology
- Subfields:
- Public health entomology
- Veterinary entomology
- Importance:
- Provide useful medical services/drugs
- Useful model systems in genetic studies
- Natural enemies of other medically harmful insects
- Vectors or hosts of pathogenic organisms
- Direct causes of disease or distress
Arthropods as Direct Causes of Diseases and/or Distress
- Delusory parasitosis (DP) and entomophobia
- Envenomization - wasps, bees, spiders
- Ectoparasites - ticks, fleas, mites
- Endoparasites - chigoe flea, myiasis
- Allergic reactions - dust mites
- Blister and urtic (itch) inducing insects - blister beetles, some caterpillars
- Annoyance - mosquitoes, black flies
Arthropods as Vectors of Diseases
- Mechanical transfer:
- Occurs passively and externally from host to host
- Pathogen does not increase inside vector
- Examples: House flies and cockroaches transfer bacteria from faeces to human food
- Biological transfer:
- Specific association between vector, pathogen, and host
- All three components are essential
- Pathogen increases inside vector
- Example: Malaria cycle
Agents Transmitted by Vectors
- Viruses (arboviruses)
- Bacteria (Rickettsia, Francisella)
- Protozoa (Plasmodium)
- Helminths (filarial nematode worms)
Method of Arthropod Vector Transmission
- Bite of vector
- Contaminated food and water
- Direct contact with infected vector
Examples of Arthropod-Borne Diseases
- Scrub typhus (Rickettsia tsutsugamushi)
- Rickettsial pox (Rickettsia akari)
- Tularemia (Francisella tularensis)
- Lyme disease (Borrelia burgdorferi)
- Ehrlichiosis (Ehrlichia canis, etc.)
- Babesiosis (Babesia microti)
- Colorado tick fever (CTF virus, etc.)
- Russian spring-summer encephalitis, Louping ill, etc. (Flaviviridae)
- Nairobi sheep fever, Crimean hemorrhagic fever, etc. (Bunyaviridae)
- Epidemic typhus (Rickettsia prowazekii)
- Trench fever (Bartonella quintana)
- Louse-borne relapsing fever (Borrelia recurrentis)
- Plague (Yersina pestis)
- Murine typhus (Rickettsia typhi)
- Rat tapeworm infection (Hymenolepsis diminuta)
- Dog tapeworm infection (Diphylidium caninum)
- Chaga's disease (Trypanosoma cruzi)
- Hymenolepsis nana
- African trypanosomiasis (Trypanosoma brucei)
- Onchocerciasis (Onchocerca volvulus)
- Leishmaniasis (Leishmania donovani)
- Loaiasis (Loa loa)
- Sandfly fever (Sandfly fever Naples virus, etc.)
- Malaria (Plasmodium falciparum, etc.)
Mites and Ticks: General
- Characteristics:
- Sac-like, unsegmented body
- Highly specialized mouthparts, capitulum/hypostome
- Phytophagous, predatory, parasitic
- 4-stage life cycle, egg-larva-nymph-adult
- Larvae 6 legs, nymph and adult 8 legs### MITES
- Usually less than 1 mm long, with 1-3 nymphal stages
- Oviposition can be via egg or ovoviviparity
- Development from egg to adult takes 8 days to several weeks, with an average of 4 weeks
- Abdomen is joined to cephalothorax, with no segmentation
- Larvae have 3 legs, while adults have 4 legs, but with some species having leg reduction
- Chelicerae are used for tearing or piercing in parasitic species
Effects on Humans and Animals
- Causes dermatitis or other tissue damage
- Leads to loss of blood or other tissue fluids
- Transfers pathogenic agents
- Can cause strong allergic reactions
Scabies
- Caused by Sarcoptes scabei mite
- Common, found worldwide, and affects people of all races and social classes
- Spreads rapidly under crowded conditions, especially through skin-to-skin contact
- Circular body, 0.3-0.45 mm in length, with striped dorsal and ventral surfaces
- Adults have 4 pairs of short legs, with females being larger than males
- Males have long strings on the last two pairs of legs
- Larvae create a moulting pocket
Clinical Presentation
- Burrow or tunnel in the skin, which is pathognomonic
- Mite is visible to the naked eye as a small white dot
- Lesions are initially erythematous, then become papular, and eventually crusty
- Alopecia, skin thickening, and pruritus occur
- Intense itching, especially at night, and over most of the body
Complications
- Secondary bacterial infection
- Nephritogenic streptococcal strains may colonize scabietic lesions, leading to acute glomerulonephritis
- Eczema may be prominent in active scabies and continue after treatment
- Acarophobia
Demodex (Follicle Mites)
- Small, worm-like mites
- Striped abdomen
- 4 pairs of legs, segmented to 5 circles
- Found in hair follicles, feeding on sebum
- Common in the nose, eyebrows, cheeks, and ears
Rosacea
- Chronic inflammatory eruption of the face, especially the central regions
- Affects up to 3% of the world's population
- Microorganisms cover the skin surface and reside deep in hair and glands
- Erythema, papules, pustules, telangectasia, and hypertrophy of the sebaceous glands
House Dust Mites
- Live on skin and sleep furniture
- Feed on dead skin layers
- Proteins, excrements, and allergens can cause allergic reactions
- Approximately 19,000 mites in each gram of house dust
- Control measures include washing bed furniture in hot water, using dehumidifiers, and cleaning the house regularly
Ticks
- Classified into two families: Ixodidae (hard ticks) and Argasidae (soft ticks)
- Segmentation is reduced externally
- Body consists of two parts: gnathostoma (capitulum) and idiosoma
- Capitulum consists of feeding appendages
- Important to humans due to exsanguination, dermatosis, paralysis, and otoacariasis
Medical Importance in Iran
- Tick paralysis: affects talking, walking, breathing, and dysphagia
- Crimean-Congo hemorrhagic fever: transmitted by Hyalomma and Argas spp.
- Tick-borne relapsing fever: caused by Borrelia persica, transmitted by ticks and rodents
Ticks Control
- Repellents
- Removing ticks
- Insecticides: Permethrin, Deltamethrin, Diazinon, and Malathion
- Impregnated ear tags and collars
- Powder spraying and dipping animals
Lice
- Classified into two suborders: Anoplura (sucking lice) and Mallophaga (chewing lice)
- Sucking lice: Pediculidae (human lice) and Pthiridae (crab lice)
- Chewing lice: feed on sloughed epidermal tissues, parts of feathers, and sebaceous secretions
- Lice morphology: all are wingless, body flattened in a dorsoventral axis, short stout legs with strong claws
- Life cycle: egg, nymph, and adult
Sucking Lice
- Pediculidae (human lice): Pediculus humanus (body louse) and Pediculus capitis (head louse)
- Pthiridae (crab lice): Pthirus pubis (pubic lice)
- Body lice: prefer cloth fibers to hair, usually stay on clothing, and can be vectors of pathogens
- Head lice: suck blood from scalp, lay eggs on hair, and are easily spread by close contact
- Pubic lice: typically found in pubic region, armpits, and rarely beards or eyelashes, and are spread by close body contact
Lice Control
- Body lice: change and wash clothing in hot water, and use insecticides like DDT, malathion, and permethrin
- Head lice: soap and water washing, combing to remove nits, and using insecticides
- Pubic lice: insecticidal emulsions and lotions
Fleas
-
No details provided in the text### Siphonaptera (Fleas)
-
Parasitic on birds and mammals
-
All adults have piercing and sucking mouth parts, feeding on blood
-
Females require blood to lay eggs
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Most species are not host-specific, feeding on several hosts
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Considered annoying pests due to blood sucking, skin burrowing, and transmission of diseases and parasites
Characteristics of Fleas
- Adults are tan to dark brown in color
- Contain numerous bristles and spines
- Small, laterally flattened, and wingless
- Large hind legs enable spectacular jumps
Importance of Fleas
- Most fleas are occasional biters, causing minor itching and little damage to skin
- Two exceptions:
- Sticktight flea (Echidnophaga gallinacea) attaches permanently to chicken skin, causing ulcerations
- Female chigoe flea (Tunga penetrans) penetrates human skin
- Disease transmission is a significant concern
Tungidae (Jigger or Chigger Fleas)
- Only one species: Tunga penetrans
- Introduced from South America in the 17th century
- Very small size
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Description
This quiz covers the taxonomy and systematics of arthropods, including insects, arachnids, and diplopods. It is designed for students of parasitology and mycology.
