40 Questions
How long can adult fleas remain active inside their cocoon?
4-12 months
How many times their own weight in blood can nymphs ingest?
6-12 times
What is the shape of the proboscis of the insect?
Thin and straight
What is the primary reason for the bugs' defecation during or soon after feeding?
For disease transmission
What is the maximum duration a flea can survive without a blood meal?
Up to 6 months
Approximately how many species of fleas exist?
2200
What is the average number of eggs laid by a female insect in its lifetime?
200-300
What is the main function of the proventriculus in fleas?
To prevent regurgitation of blood
Why is it medically important to know that fleas will abandon their host if it dies?
Because it allows fleas to transmit diseases to other hosts
How long does it typically take for the complete life cycle of these insects to occur?
3-10 months
Where do female insects typically lay their eggs?
In mud walls or cracks in walls and floors
How do fleas move on their host?
By crawling
Why do hungry adults and nymphs sometimes pierce the swollen abdomen of an engorged nymph?
To feed on the nymph's blood
What is unique about the flea species Tunga penetrans?
It burrows into people's feet
What is the purpose of the genal combs in some flea species?
To defend against predators
How many nymph instars are there in the life cycle of the insect?
5
What is the maximum vertical distance a flea can jump?
20cm
What is the typical duration of feeding for these insects?
10-25 minutes
Where do female fleas typically lay their eggs?
In debris or detritus
What is the maximum lifespan of an adult insect in the absence of hosts?
4-6 months
How do fleas jump?
Using a molecular spring link trigger
What is the typical size of the eggs laid by the female insect?
1.5-2.5mm
What triggers the emergence of adult fleas from their pupae?
Vibrations from an animal moving nearby
How long does it take for the eggs to hatch?
10-15 days
What is the most common nuisance flea species in the US?
Ctenocephalides felis
What is the function of the silk produced by larval fleas?
To create a protective cocoon
What is one of the main reasons for the medical importance of fleas?
They can cause discomfort and irritation to their hosts
What is the color of the eggs laid by the female insect?
White, pearly, pink, or yellowish
How many blood meals do the nymphs require?
One per instar
What is the purpose of the flea's powerful hind legs?
To jump long distances
How many eggs can a female flea lay during her lifetime?
300-1000
How long does the larval period of fleas typically last?
2-3 weeks
How do people typically get infected with Chagas disease?
By scratching the feces of the insect into their skin
What is the number of triatomine species that have been found to be infected naturally?
70
What determines the vector efficiency of triatomine insects?
Speed of feeding and defecation rate
Which of the following is a non-pathogenic species of trypanosome?
Trypanosoma rangeli
What is the primary host of the trypanosome parasite?
Wild animals
What percentage of triatomines in an area may be infected?
25 to 50%
What is another way people can get infected with Chagas disease?
By eating infected bugs or animals
Where is Chagas disease most common?
Central and South America
Study Notes
Fleas
- Order Siphonaptera: 2200 species, 220 genera, with only a few important to humans
- 94% of fleas bite mammals, while the remainder feed on birds
- Worldwide distribution, with many species and genera having limited ranges
General Taxonomy
- Medically important genus: Xenopsylla
- Other genera with medically important roles: Ctenocephalides (hosts for cestodes)
- One flea species (Tunga penetrans) "burrows" into people's feet
Morphology
- Adults: 1-6mm, oval shaped, compressed laterally, light to dark brown, with small bristles and spines
- Lack wings, but have powerful legs, with hind legs specialized for jumping
- Females: tip of the abdomen is more rounded
- Head: triangular, with conspicuous eyes, club-shaped antennae, and mouthparts pointing downward
- Some species have tooth-like spines called genal combs
Role of Blood Feeding
- Both sexes take blood meals, with saliva injected during feeding containing anticoagulants
- Blood sucked through pharynx into proventriculus, with backwards pointing spines to prevent regurgitation
- Proventriculus is important for disease transmission
- Blood enters mid-gut for digestion
Life Cycle
- Female deposits eggs in debris or detritus, often in habitat or dwelling where host lives (nest, burrow, etc.)
- Eggs: small (0.1-0.5mm), oval, yellow or white, with female laying 300-1000 eggs during her lifetime
- Eggs hatch after 2-5 days, with legless larva emerging
- Larval period: 2-3 weeks, may be up to 200 days
- Pupae: white cocoon made of silk, with silk being sticky and picking up bits of dust, dirt, and debris
- Adults emerge after 2-3 weeks, with stimulus required for emergence usually being a vibration of an animal moving nearby or carbon dioxide
Adults
- Can live anywhere from 10 days to 12 months
- Avoid light, usually hiding among the hair or feathers of the host (or clothing, in beds)
- During feeding, feces are evacuated to make room for blood meal
- Presence of flea feces (sometimes partially digested blood) can be seen in bed linens of infested houses
Host Specificity
- Most fleas have a slight preference for a specific host, but will bite other hosts when their preferred host is absent
- If a host dies, fleas will abandon host for a new one
- Some fleas can tolerate desiccation, starvation (up to 6 months), and can jump up to 20cm vertically or 30cm horizontally
Medical Importance
- Four main reasons for medical importance: Nuisance, Plague, Murine Typhus, and Cestodes
- Nuisance aspect: flea bites result in discomfort, swelling, and irritation, with cat fleas being the most common nuisance species in the US
Learn about the biology, taxonomy, and medically important aspects of fleas, including their species, genera, and distribution. This quiz covers the morphology, feeding habits, and characteristics of fleas.
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