Fleas Flashcards
What are fleas?
small wingless ectoparasites of the order Siphonaptera
Where are fleas found?
Live on the host or in the host’s burrow 94% of species are parasites of mammals and 6% are parasites of birds
What do fleas vector ?
Plague Murine typhus Tape worms Both males and females are vectors
How are fleas classified?
Combed - cat and dog fleas Combless - Pulex (human flea) and Xenopsylla (tropical rat5 flea) Jigger/ Chigoes - Tunga penetrans (not a vector)
What are the key features of Ctenocephalides
genal comb pronotal comb meral rod
What is not present in Pulex
No combs No meral rods
Flea life cycle
Females lay eggs in the nest of host animal Larva feeds on near detritus and undergoes three moults to reach the pupal stage The pre-emergent adult can remain in the pupal state for over a year but in ideal conditions emerges after 6 days Females lay up to 25 eggs per day and can live for several months
Where can plague be found in wild reservoirs
Asia, Americas and Africa
What is Plague
zoonotic disease of wild rodents transmitted by numerous wild rodent fleas
what is sylvatic plague
woodland plague with background levels of transmission with little harm to rodents and occasional transmission to humans (hunters and forestry workers etc.) infrequent epizootics in wild rodents and when rodents die often leads to the disease entering an urban cycle
What is urban plague
First sign of urban plague in brown/sewer rat Rattus norvegicus - lives at interface between syllabic and domestic environment May be followed by an epizootic in the more domestic black rat Rattus rattus Fleas rapidly abandon dead hosts to seek out new ones Two weeks later there are human cases
What are the main flea vectors of urban plague
Xenopsylla cheopis Nosopsyllus fasciatus Pulex irritans
How is flea to mammal transmission achieved?
Regurgitation of fleas oesophageal contents Proventriculus - spines normally press together to prevent regurgitation Proventriculus blocked by large number of bacilli Hungry fleas then bite repeatedly
Murine typhus - Rickettsia typhi
rickettsial disease also called endemic or flea borne typhus rarely fatal (<2% of cases) caused by infection of commensal rodents - Rattus rattus and Rattus norvegicus distribution throughout the tropics especially in ports transmitted through flea faeces (rubbed into the wound) Main vector is Xenopsylla cheopis
What is the main vector of murine typhus
Xenopsylla cheopis
Where is murine typhus found
tropics in ports
how is murine typhus transmitted
flea faeces rubbed into the wound
What are the symptoms of rickettsial disease
fever transient rash falling blood pressure headache backache
Cestodes - Dipylidium caninum - dog/cat parasite life cycle
tapeworm eggs in animal excreta consumed by larval fleas become infective stage (cysticercoids) in adult flea infected flea eaten by dog or cat when grooming children occasionally infected when playing with pets through swallowing fleas or being licked by pets with crushed flea in mouth
Cestodes - Hymenoleptis - rat tapeworm
Can also infect humans
Xenopsylla control
residual insecticide spraying of domestic rat runs and burrows during outbreaks, treat all dwellings <200 m of affected one range of insecticides available but resistance common for wild rodent flea, insecticide in bate boxes made of bamboo dichlorvos resin strips on container ships
insecticial control of fleas must precede or at least be coincident with rodent control
What is the most essential feature of insecticide control of plague and murine typhus
MUST precede or at least be coincident with rodent control
Rodent control
domestic - rodenticides e.g. warfarin amongst many others rodent chemosterilization (long term)
wild - HCN Methyl bromide gas
Jigger flea - Chigoes - Sand flea - Tunga penetrans
Distribution restricted to Americas and Africa and India attacks rodents, pigs and man - female burrows into the skin common on toes and nail bed eggs extruded from 8th day - lays 100-200 eggs over 14 days (2 larval instars)
Treatment of jigger fleas
Careful removal and prevention through wearing footwear
Where can the jigger flea be found
Americas, Africa and India
What is a key feature of Tunga penetrans
Compressed thoracic segments Females can have a distended abdomen
Ctenocephalides female
combed dog and cat flea
features include meral rod, pronatal comb and genal comb
intermediate hosts for Diphylidium caninum
Xenopsylla female
combless flea and most important for plague transmission
tropical rat flea
Pulex female - human flea
no combs or meral rods
important for plague transmission
flea larva - maggot like and approximately 0.5 cm long
covered in many small hairs
Distribution of countries with known presence of plague in wild reservoir species
flea eggs - pearly white, oval with rounded ends and 0.5mm in length
Flea cocoons - at the end of the larval period, the larva spins a whitish cocoon from its salivary glands - covered in dust particles
tunga pentrans male
compressed thoracic segments
female tunga penetrans with hugely distended abdomen
worldwide distribution of murine typhus
