The document provides an overview of mosquitoes and their significance to public health, highlighting their role as vectors for diseases such as dengue, chikungunya, and zika. It details their anatomy, lifecycle, and the specific species associated with various illnesses, including the Aedes, Anopheles, and Culex mosquitoes. Additionally, it discusses factors affecting disease transmission and the importance of mosquito control for disease prevention.

1. Mosquitoes & their related
Diseases

2. Table of Contents
• Mosquitoes & Public Health Importance
• Mosquito Anatomy & Biology
• Mosquito Identification
• Mosquito Borne Disease

3. Mosquitoes & Public Health
Importance

4. Introduction: Public Health Importance
of Mosquitoes
• All mosquitoes, being hematophagous (blood
feeding) on human and other animal hosts are
potentially vectors (transmitters) of various
diseases.
• Mosquitoes are a nuisance since they bite trying
to get a blood meal from man and his animals.
• Mosquitoes known to cause vector borne
diseases.

5. Introduction: Public Health Importance
of Mosquitoes
• The Aedes mosquito was introduced in the
Caribbean through the African slave trade.
• The Aedes aegypti remains the principal
vector responsible for the transmission of
Dengue, Chikungunya and Zika virus.

6. Introduction: Public Health Importance
of Mosquitoes
• The presence of mosquitoes means
individuals are at risk of disease transmission
which can impact on the:
– Mental and social well being of individuals
– Economic cost (vector control, sick, loss
productivity)
– Negatively on the tourism sector

7. Mosquito Anatomy & Biology

8. What is a Mosquito?
• Mosquito is an insects,
part of a group of
arthropods – crabs,
spiders and shrimps etc.
• They are invertebrate
animals with hard
exoskeletons with joints.

9. Life Cycle of a Mosquito
• There are four distinct stages in
the life history of the mosquito:
Egg
Larva
Pupa
Adult
•The first three stages occur in
water
• the adult is an active flying
insect that feeds upon the blood
of man and animals or upon plant
juices depending on the species
of mosquitoes.

10. Life Cycle of a Mosquito
Egg
• The ADULT female mosquito
takes a blood-meal and after
digestion of the blood and
absorbing the protein, flies to
an appropriate location and
lays EGGS in close proximity
to water
• Eggs are laid:
– directly on the water surface,
– on the sides of a container, or
– on plants growing in the water.

11. Life Cycle of a Mosquito
Egg
• Some mosquito species lay
their eggs on a moist
surface.
• When water is introduced
then the larval stage will
emerge.
• The eggs of some species
can survive up for 3-5 years
without water.
• Depending on the species,
the eggs may hatch in 1-3
days, producing LARVA.

12. Life Cycle of a Mosquito
Larva
• The larva of all mosquitoes live in
water
• Most mosquitoes are adapted to
almost all kinds of aquatic
environment except:
– Flowing streams
– Open waters of large streams
& seas
• These larvae may grow in 4 instars
(stages)
• They cast off their old skins and
increase in size.
• The larval stage may take up to 7
days or more, depending on the
nutrition, temperature and
species.

13. Life Cycle of a Mosquito
Larva
• Larval mosquitoes feed on
debris of organic matter.
• Most people can recognize
as the wriggling immature
stage of the mosquito.
• Although, mosquitoes get
their food from the water,
they must come to the
surface for air.
• It is a phase of feeding and
growth for the mosquito.

14. Life Cycle of a Mosquito
Pupa
• A comma-shaped phase of the
insect.
• The adult features of the adult
mosquito are developed, and only
lasts 1-2 days.
• Mortality in this stage is relatively
low
• The amount of pupa present in any
container, is a good indication of
the productivity of a container.
• The ADULT then emerges from the
pupa, takes to the wing and flies off
to mate and feed - take a blood
meal (females), or plant juices
(males).

15. Life Cycle of a Mosquito
Adult
• About equal numbers of
male and females
produced.
• Males usually emerge first
and remain near the larval
habitats and mates with
the female soon after their
emergence.
• Female tends to travel
greater distances and
appears to live long.

16. Life Cycle of a Mosquito
Adult
Habitat: Depend on the species of
mosquito
• The Aedes prefers highly domesticated
areas and breeds in clean, clear water
and bites during the day (dusk to
dawn).
• The Culex mosquito is less particular
about the water quality in which they
breed (drains and dirty bodies of water)
and prefers to feeds at dawn or after
dusk.
• The Anopheles sp. occurs in a wide
range of habitats but most species
prefer clean, unpolluted water. They can
also be found in fresh or salt water
marshes, mangrove swamps, the edge
of streams and rivers and temporary
rain pools. A few species breed in tree
holes or the leaf axils of some plants.
Most Anopheles species are active at
dusk or dawn and at nights.

17. Mosquito’s Anatomy
Three parts of an adult
mosquito:
• Head (eyes, antennae,
the mouth parts
(proboscis)
• Thorax (wings and
venation)
•Abdomen

18. Mosquito’s Anatomy
The Head
• Sensory organs which assist in
finding and feeding on people and
animals.
• Two large compound
eyes capable of detecting even
slight movement.
• Antennae, long feathery organs,
which contain sensitive receptors to
detect carbon dioxide in human
breath from distances of more than
100 feet.
• Maxillary palp which pick up the
odor of ocentol and other chemicals
released in human sweat.
• Proboscis is a long serrated
mouthpart used to pierce the skin
and suck out blood. The proboscis
holds two tubes, one that injects
saliva containing an anti-coagulant
and mild painkiller, and a second

19. Mosquito’s Anatomy
The thorax
• Legs – there are three pairs of legs
resulting in 6 legs. The legs are
used to identify the species of
mosquito. For example the Aedes
species have white banded legs.

20. Mosquito’s Anatomy
The abdomen
• There are small opening on the
abdomen called spiracles which
draws in air.
• The abdomen is also where the
mosquito stores its eggs.

21. Mosquito Identification

22. Mosquito Identification
• In the discipline of medical (public health)
entomology, a system of “keys” has been
developed to identify mosquitoes at the
species and at the generic levels.
• These keys are based on anatomical
features such as the features of:
- the head (the eyes, the
antennae, the mouth parts);
- the thorax (the wings and
venation, the scales on the wings and thorax,
the legs and details;
- the abdomen –( the shape , the
terminal segment, the hairs and scales etc.).
•However, for identification of general
common mosquito types, in the egg, larval,
pupal and adult stages of an Anopheles,
Aedes or Culex types more detail is needed.

23. Clue: White banded
legs

24. Clue: Proboscis
longer than Maxillary
Palps

27. Mosquitoes in St. Vincent

28. Mosquito Borne Diseases

29. Mosquito- Borne Diseases
• Aedes – associated with the transmission of Dengue Fever (DF),
Chikungunya and Zika Virus. Yellow Fever although not endemic in SVG
is endemic in Trinidad.
• Anopheles – associated with the transmission of Malaria. Malaria is not
endemic to St. Vincent and the Grenadines. It is transmitted by
Anopheles mosquitoes in Countries such as Guyana, Suriname, Belize,
Jamaica, Haiti and the Dominican Republic (DR).
• Culex associated with the transmission of Lymphatic filarias, but only
confirmed in Guyana and Suriname. The West West Nile virus
infection, transmitted by Culex mosquitoes, may be present in
migratory birds. In 2002, there were confirmed infections in birds in
Jamaica, DR and Puerto Rico. There were human cases in 2002 in
Cayman and the Bahamas, and caged bird and horse infection in
Trinidad in 2004.

31. Dengue Fever and Chikungunya Virus
• Viral diseases transmitted from an infected to a non-
infected person, by the bite of an Aedes aegypti
mosquito.
Characterised by the sudden onset of:
Dengue Fever Chikungunya Virus
Fever High fever
Headache Headache
Retro-orbital pains Severe joint pain mainly in arms
and legs
Backache Back pain
Loss of appetite Rash (about 50% of persons
affected)
Muscle and joint pain Muscle pain

32. Dengue Fever Chikungunya Virus
Typically 3 to 5 days with a
range of 3 to 15 days
Typically 3 to 7days with a
range of 1 to 12 days.
The infection is self-limiting,
and the patient infected with
one of the 4 Dengue serotypes
recovers after being unwell for
10- 15 days.
Most people start to feel
better after 7 to 10 days
although some people will
develop longer term joint
pain.
Dengue Fever and Chikungunya Virus
Incubation Period

33. Yellow Fever
• The "yellow" in the name refers to the jaundice that affects some patients.
• Symptoms of yellow fever include:
– Fever
– Headache
– Jaundice
– Muscle Pain
– Nausea
– Vomiting and Fatigue
• A small proportion of patients who contract the virus develop severe
symptoms and approximately half of those die within 7 to 10 days.
• The virus is endemic in tropical areas of Africa and Central and South
America but is currently not endemic to St. Vincent & the Grenadines.
• Since the launch of the Yellow Fever Initiative in 2006, significant progress
in combatting the disease has been made in West Africa and more than
105 million people have been vaccinated in mass campaigns.

34. Yellow Fever
• Large epidemics of yellow fever occur when infected people
introduce the virus into heavily populated areas with high
mosquito density and where most people have little or no
immunity, due to lack of vaccination. In these conditions,
infected mosquitoes transmit the virus from person to person.
• Yellow fever is prevented by an extremely effective vaccine,
which is safe and affordable. The vaccine provides effective
immunity within 30 days for 99% of persons vaccinated.
• Good supportive treatment in hospitals improves survival
rates. There is currently no specific anti-viral drug for yellow
fever.

35. Zika Virus
• Zika is also spread to people through the bite of an
infected Aedes aegypti mosquito.
• The virus can also be transmitted from an infected
mother to an unborn child – resulting in
microcephaly.
• This disease can also caused a paralytic disease
called Guillain-Barre Syndrome.
• Studies also shown that the virus can also be
transmitted via sexual intercourse.

36. Zika Virus
• People with Zika virus disease can have symptoms including:
– mild fever,
– skin rash,
– conjunctivitis,
– muscle and joint pain, malaise or
– headache.
• These symptoms normally last for 2-7 days.
• The symptoms are similar to other arbovirus
infections such as Dengue Fever, Yellow Fever and
Chikungunya
• Confirmation of diseases is done through laboratory
testing

37. Factors affecting Disease Transmission:
Climate/Weather conditions
• In some years there are more episodes of DF transmission
than other years, and this may be affected by climatic
conditions.
• Dry hot periods such as occur in an El Nino period – as
happened in late 2009 and early 2010 in the Caribbean – are
not very conducive for mosquito production.
• However, research has shown that the year after (El Nino +1),
when it is wet and warm could be good for mosquito
production and virus multiplication in the mosquito and
transmission to new susceptible hosts.
• Thus late 2010 may well be a dangerous year for DF
transmission in EC countries (Fig.12).

38. Climate/Weather conditions

39. • The role of the Vector Control Inspectors thus
very important in disease prevention, since:-
• There are no effective treatment or vaccines
for most diseases transmitted by the
mosquitoes.
• It is therefore, important to control/eliminate
the immature and mature stages of the
mosquito!

40. Questions?

41. 41
• Members of class insecta,
order diptera
• 127 families, >85,000 species.
• Diptera - most important
vectors human disease.
 > 1 million deaths p.a.
1-1.5mm
1-3mm
18-22mm

42. 42
Flies - blackfly
Family Simuliidae.
• Simulium damnosum, S. neavei - important vectors in Africa.
• Simulium ochraceum - important vector in New World
(Australia – New Zealand)
• Breeds close to fast moving water or water falls
– Eggs are laid on running water, larvae attach on submerged
structures e.g. rocks, trees & vegetation
– S. neavei in Africa occur on arthropods
1-3mm
1-3mm

43. 43
Black fly
Effects on hosts.
Allergic reactions. "Blackfly fever"
Vector - Onchocerca volvulus – filarial nematode.
Vectors - Leucocytozoon spp. - "malaria" in birds.
1-3mm

44. 44
Midges.
Effects on vertebrate hosts:
• Annoyance.
• Vectors of Acanthocheilonema perstans -
filarial parasite humans and other filarial
nematodes.
1-1.5mm

45. 45
Tabanids
Order Diptera.
Suborder Brachycera
Family Tabanidae.
• ~ 4000 species
• Females intermittent parasites
• Males not parasitic
• Adults - large body (6-25mm long)
• Large eyes - facilitates host location
• Mouthparts - cut large wound, where they feed
from a formed pool of blood
18-22mm

46. 46
(c). Flies - tabanids
& bacteria.
Suborder Brachycera, Family Tabanidae.
• Mechanical vectors:
– Bacillus anthracis – anthrax.
– Francisella tularensis - tularemia – deerflies Chrysops spp.
• Blood loss
Important genera:
• Tabanus
18-22mm
18-22mm

47. 47
Flies - tabanids
• Vectors Loa loa, - filarial nematode.
• “Eye worm“.
• Vectors for Chrysops spp. (deerflies).
• C. dimidiata - most important.
18-22mm
18-22mm

48. 48
Flies - tsetse fly
Family Glossinidae, genus Glossina.
• Hosts & vectors of trypanosome protozoans.
• Trypanosoma brucei species complex.
• Sub-saharan Africa.

49. 49
Flies - sandflies
Family Psychodidae
Phlebotomus & Lutzomyia species
• Vectors of Leishmania - protozoa
• Cutaneous leishmaniasis (L. tropica - Old World
• L. mexicana- New World)
• Mucocutaneous leishmaniasis (espundia) - L.
braziliensis
• Visceral leishmanisis (kala azar) - L. donovani

50. 50
Sand fly
• Sand flies
• Phlebotomus & Lutzomyia
• Short mouth parts, pool feeders
• Only ♀♀ take blood
• Vector of Leishmania, bartonellosis
(bacterial) & sand fly fever (viral)
• Less than 5mm length, hairy body &
wings
• Old world species live in arid/semi-
arid conditions, new world species are
forest dwellers
• Epidemiological implication
• Have limited flight range close to
breeding sites
• Most active at twilight, night & shade

51. 51
House fly
• Musca domestica
• Domestic flies act as mechanical vectors of
many diseases

52. 52
Public Health importance
1. Nuisance
• Large numbers flies can be bring significant
nuisance by disturbing people during work
and at leisure.
• Flies soil the inside and outside of houses
with their feaces.
• They can also have a negative psychological
impact because their presence is considered a
sign of unhygienic conditions.

53. 53
2. Diseases
• Flies can spread diseases because they feed freely on
human food and filthy matter
• Flies pick up disease-causing organisms while
crawling and feeding
• Those that stick to the outside surfaces of the fly
may survive for only a few hours, but those that are
ingested with the food may survive in the fly’s crop
or gut for several days

54. 54
Diseases that flies can transmit include enteric
infections (such as dysentery, diarrhoea,
typhoid, cholera and certain helminth
infections), eye Infections (such as trachoma)

55. • Triatomine Bugs
(Order Hemiptera,
Genus Triatoma)
• Fleas (Order Siphonaptera)
Human Flea (Pulex)
Rat Flea (Xenopsylla)
Cat Flea (Ctenocephalides)
Jigger Flea(Tunga)
Bedbugs (Cimex)

56. Bugs
• Class: Insecta
• Order: Hemiptera
• Family: Cimicidae ( bed bugs )
• Family: Reduviidae
• Sub-family: Triatominae
• 15 genera with > 100 spp
• Panstrongylus, Triatoma, Rhodnius

57. Bed bugs
• Family: Cimicidae
• Blood sucking
• Temporary ectoparasites of birds and
mammals
• Human parasites:
–Cimex lectularis - main
–Cimex hemipterus
57

58. Morphology
• Oval, dorso-ventrally flattened, red-brown
bodies
• They are covered with short, stout hairs
• They are 5-7mm long, with females slightly
larger than males
• Head have prominent compound eyes.
• The proboscis is flexed backwards under the
head when not in use
• Legs terminate in a pair of simple claws
• Forewings reduced (hemielytra pads), hind wings
absent
58

59. 59

60. Habits
• They feed at night on humans or other
mammals
• A blood meal is essential to production
of eggs
• Conceal themselves during the day in
crevices of wooden beds, mattresses,
or under loose wallpaper.
• In search for hosts, they respond to
warmth & CO2, odours
60

61. Habits...
• Are easily transported in clothing and
baggage
• In cold weather they remain inactive in
hiding places
• They can survive starvation for over a
year
• Emit a characteristic odour from scent
glands
• Often found in dwellings with high rate of
occupant turnover – hotels, motels,
hostels, shelters & apartment complexes
61

62. Life Cycle
• Females deposit about 200 eggs in cracks
and crevices
• Eggs
– White, ovoid, about 1mm in length
– Have an operculum at the anterior end
– They are coated with transparent cement
– They hatch in 4-10days
– No hatching at 37⁰ or below 13⁰ C
• Incomplete metamorphosis
62

63. Life cycle...
• Nymph
–Yellowish-white to brown
–Passes through 5 or 6 moults before
becoming a sexually mature adult
• At 30⁰C, development from eggs to adult
takes 3 weeks
• The life span of the adult is 6-12 months
63

64. Medical Importance
• Sleep disturbance
• Biting nuisance
– The bite produces red, itching wheals
– Allergic symptoms – local or generalised urticaria and
asthma
• Transmission of diseases?
– Not believed to be a vector of disease
– As a mechanical carrier - Hepatitis B virus from human
to human. Virus from faeces could infect a person by
contamination of skin lesions or mucosal surfaces or
by ingestion of dust
64

65. Triatomine bugs
Family: reduviidae
Sub-family: triatominae
• Cone nose/assassin/kissing bugs
• Medically important, only found in americas
• Size: 1-4 cm long
• Elongated head
• Lateral 4- segmented antennae
• Eyes lateral

66. Tritomine bugs...
• Proboscis ventrad
• Two pairs of wings
• Basal fore wing thick/hardened, posterior wing
membrenous = heteroptera
• Lateral margins of abdomen visible dorsally

67. Triatomine bugs…
• Most are dull brown but some may have markings
• The shape of the head, position of the antennae
relative to the eyes: genera specific
• Hemimetabolous
• Eggs laid in/near host habitations: cracks on walls
etc

68. Life cycle…
• Eggs are laid in batches 100-800
• Hatch into wingless nymphs
• There are 5 nymphal instars, each requiring
blood
• N4 and N5 have rudimentary wings
• May take in blood up to 10x body weight
• Assassin?

69. Life cycle…
• Both nymphs and adults feed nocturnally
• Feed on exposed parts of the body: face, eyes,
nose, mouth - kissing
• Defecates during feeding
• Feed on humans, wild and domestic animals.

70. Life cycle…
• Development from egg to egg takes 3 months in lab
but may take 1-2 yrs in nature
• Vectors of T. cruzi:
• R. prolixus, P. megistus, T. dimidiata and T.
infestans
• Prevention and control
• Insecticide residual spraying, Insecticide treated
bednets, improved housing

71. Order Siphonaptera
• SIPHONAPTERA: Greek "siphon" (hollow tube) + "a"
(without) + "pteron" (wing); fleas are wingless and have
tube-like mouthparts for sucking blood
• Body hard, laterally compressed, and bristly
• Legs long with large coxae and 5-segmented tarsi
• Generally live as ectoparasites of mammals and birds.
• Fleas transmit various pathogens, including tapeworm and
bubonic plague.
• About 1,100 species of Siphonaptera in the world, 238 in
North America.
• 7 families of fleas based on characters of the head,
abdomen, and various bristles. Many characters are visible
only on specimens mounted on microscope slides.

72. Order Siphonaptera...
Pulicidae -- common fleas
Ischnopsyllidae -- bat fleas
Tungidae -- sticktight and chigoe fleas
Dolichopsyllidae --rodent fleas
Hystrichopsyllidae -- rat and mouse fleas
Malacopsyllidae -- malacopsyllid fleas
Vermipsyllidae -- carnivore fleas

73. Distribution
• Species and genera are distributed in East-Asian,
Central-Asian, West-American, Patagonian, Papuan
(New Guinean), and East-African zoogeographical
subregions.
• Forest foothills with temperate and subtropical climate
most favourable conditions for the fleas.

74. Morphology
• Shape of the head, flat body & prehensile claws
of legs help it to move easily through host’s
wool
• Length of jump some flea species attain ~32
cm, average body length being from 1 to 5 mm

76. Biology
• Fleas are obligatory blood feeders parasitizing warm-
blooded vertebrates. More than 94% of known species
are parasites of mammals and only about 5% of them
occur on birds
• Fleas have 4 phases of development - the egg, the free-
living larva, pupa and the imago
• The larvae is wormlike, legless & eyeless with biting
mouth parts. The larvae undergoes 3 instars. Prior to
pupation it empties the alimentary canal, and spin a
silken cocoon
• The majority of fleas are closely associated with the
host's home (nest, burrow etc), attacking the host for
feeding

77. Life cycle
• Adult flea jumps onto a host, gets a meal. A flea
bite becomes inflamed, itchy and swollen
• Once fed, the flea will mate and lay eggs. This
occurs in yards, houses, & on pets
• In the next two to three weeks, hundreds of eggs
will be laid in yard, house and on the host
• Eggs hatch into small larvae, which feed on
anything organic. Including dried blood, flea
faeces, animal hair.

78. Life cycle...
• The larva will feed for days, spin a cocoon and undergo
metamorphosis
• This stage is called the flea pupa. Its a worst stage
because of its resistance to control
• The cycle is completed when the flea pupa hatches
out. Hatching occurs when a host is close, will bite and
the cycle will start all over again

79. Medical significance
• Fleas transmit pathogens that cause disease in
humans and other animals.
• The Cat and Dog flea are intermediate hosts for a tapeworm
(Dipylidium caninum) that infects dogs, cats, and humans
• The Rabbit flea spreads a myxomatosis virus within rabbit
populations
• Oriental Rat Flea is the primary vector of Yersinia pestis,
the bacterial pathogen for bubonic plague.
• The cat flea commonly infests dogs, dog flea may
infest cats; both species may bite humans

80. Medical significance...
• Sand flea/jigger, Tunga penetrans
• Infect humans, pigs, birds
• Adapted to intracutaneous attachment, larvae free living, adults
free living but after mating penetrate the hosts.
• Soft areas are preferred for penetration
• In the body attaches with mouth, swells and envelops itself
leaving a spiracle for breathing
• Irritations start when a flea is mature, scratching helps to release
eggs

81. Control
• Best stage to control is an egg
• Treating animal pets
• If the pet is an inside animal, treat the home and the pet
• If the pet is an outside animal, treat the pet & the area the pet has
access to
• Treat home areas when fleas suspected
• Application of repellents
• Keeping environments clean out of organic matter
• Sweeping, mopping floors
• Treating floors with insecticides; DDT, OPs, PY, Cb
• Burning off infested soils
• Flea trap to induce hatching of pupae

82. Control...
• Wearing good, intact shoes
• Daily inspection of areas of the feet (interdigital
clefts)

83. 83
Other ectoparasites
Arachnid Vectors
1. TICKS
Soft Ticks (Ornithodorus)
Hard Ticks (Ixodes, Amblyomma,
Rhipicephalus, Dermacentor)
2. MITES
(Dematophagoides, Demodex,
Sarcoptes)
• Lice (Order Phthiraptera)
– Head/Body Lice (Pediculus)
Crab Lice (Phthirus)
TICKS
• Soft Ticks
Class: Arachnida
Order: Acarina
Family: Argasidae
Genus: Ornithodorous
General Characteristics
-tough leathery integument
-flattened oval shape when examined
dorsally
-they lack the dorsal shield
-they need to be examined ventrally to
observe their capitulum or
mouthparts.

84. 84
Ticks
• Ornithodoros spp. is the
most important soft tick
disease vector found
throughout the world
Ornithodoros populating in
Europe, Africa, Asia and
Americas.
Life cycles
• Soft ticks have a
hemimetabolous life cycle,
eggs hatching six legged
larvae, which moult to eight
legged nymphs

85. 85
• There are 5 - 7 larval instars
depending on the species
• Each stage requiring a blood
meal to proceed except of
Ornithodoros moubata
• Adult females lay small egg
batches following each blood
meal
• The duration of the life cycle
depends on temperature, host
availability and species
Disease
• Soft Ticks are vectors for
serious disease including :
– Tick borne relapsing fever
(Borrelia duttoni)
– Rickettsial disease (Coxiella
burneti), and some arboviruses

86. 86
Hard Ticks
• Class: Arachnida
• Order: Acarina
• Family: Ixodidae
• Genus: Ixodes, Amblyomma, Rhipicephalus,
Dermacentor

87. 87
• They are flattened when examined dorsally
• Characterized by the presence of a dorsal plate or
scutum, and a capitulum that projects beyond the body
outline
• The scutum regularly covers the entire dorsal area
• Ixodes spp. inhabit in Canada, Europe, Russia,
China, Japan and Australia
General Characteristics

88. 88
• Ixodes Adult male
showing the scutum
covering the whole length
of the body
• The capitulum is seen
protruding forward
beyond the body outline

89. 89
Life Cycle
• Similar to that of Soft Ticks
• There is only one nymph stage in Ixodes, and
following several weeks of stasis the nymph
will metamorphose into an adult

91. 91
Diseases
• Hard ticks transmit lyme disease, tick paralysis and
Rickettsiae
• Arboviruses that are responsible for encephalitis and
haemorrhagic fevers, tularaemia and Babesia microti
infection

92. 92
Other medically important Hard Ticks
Wood ticks
(Dermacentor andersoni)
• Found in the
mountainous west of
North America;
• Dog ticks
(Rhipicephalus) found in
coastal areas.
• Lone Star ticks
(Amblyomma
mericanum) found in
forests in SE USA
• The females of these
species causes tick
paralysis.

93. 93
• Dermacentor variabilis • Amblyomma, male hard
tick.

94. 94
• Both Dermacentor and Amblyomma transmit Rocky
Mountain Spotted Fever (Rickettsia rickettsia).
• Dermacentor transmit arboviruses responsible for
encephalitis and heamorrhagic fevers.
• D. variabilis is also responsible for spreading
tularaemia, Mediterranean Spotted Fever and
African Tick Typhus.

95. 95
Control
• Improve sanitation
• Cementing floors to eliminate cracks and crevices
and facilitate cleanliness
• Where floors are not cemented should be kept out
of dust
• The floors and walls up to a height of about half a
meter should be spread or dusted with lindane

96. 96
• With dust floor monthly application would be
necessary
• Other chlorinated hydrocabons, organophosphorus
compounds, carbomates or pyrethroids may be
used

97. 97
Mites
• Class: Arachnida
• Order: Acarina
• Genus: Dematophagoides,
Demodex, Sarcoptes
• General Characteristics
• Dematophagoides, is a
common dust mite,
inhabit beds,
mattresses, carpets and
house dust

98. 98
• They are motile
• They feed on residual
organic debris 0.3 mm
in length
• They have four long
legs, suckers and pincer
chelicerae

99. 99
• Dermatophagoides are antigenic, even when dead
(fecal pellets are also allergenic)
• Associated with complex allergies & symptoms such
as asthma, conjunctivitis and dermatitis.
• A treatment involves removal of accumulated
antigens from mattresses and pillows

100. 100
• Demodex have been implicated in dermatitis and
should be considered in chronic, therapy-resistant
cases of blepharitis (inflammation of eyelids)
• The role of this mite in ocular disease is uncertain
washing with soap and water is the most effective
method of prevention.

101. 101
• The mite, Sarcoptes scabiei, lives
on human skin causes scabies
• It is small (larger female is 0.3-
0.4 mm), colorless and oval with
8 short legs

102. 102
• Symptoms of Sarcoptes infection arise after 4-6
weeks post invasion
• Comprise a papular pruritic eruption at a site
often unrelated to the site of infestation;
symptoms of secondary infestations arise almost
immediately

103. 103
• Persistent nodular scabies involve itchy
erythematous or scabbed nodules
• When the immune system is impaired, Norwegian
(crusted) scabies may develop
– This presents with erythema and hyperkeratosis but little
itching

104. 104
Diagnosis
• Discovery of mites or eggs by epidermal shave
biopsy or superficial scraping
• Burrows are best seen on wrists and inter-digital
spaces
• They fluoresce under a Wood's lamp after
application of liquid tetracycline and alcohol;
alternatively ink may be used

105. 105
Treatment and control
• Lindane lotion is the treatment of choice,
permethrin is another alternative
• Ivermectin has been recommended for
Norwegian scabies
• Malathion liquid can also be used, benzyl
benzoate is also active

106. 106
• Malathion should be avoided in infants
• Lindane should be avoided in pregnancy, breast-
feeding and in young children
• Treatment is applied over the whole body except
the head and neck and washed off after 24 hours

107. 107
• Normal laundering of bed linen and clothes is
recommended
• Household and sexual contacts should also be
treated
• Symptoms may continue after treatment
because of persisting antigens, Calamine lotion
may be used
– other problems include re-infestation and secondary
bacterial infection

108. Myiasis
• Infestation of the organs and tissues
of humans or animals by fly larvae that
for some period of time, feed upon the
living or dead tissues or the ingested
food of the host
• It is the condition in which larvae of
flies exist as parasites in bodies of
vertebrates

109. Myasis
• Myasis is caused when fly maggots
(larvae of dipterans) invade living tissue or
when they are harboured in the intestines
or bladder
• Clinically, maggots causing myasis attack
three parts of the bogy: Cutaneous tissue,
body cavities and gut lumen

110. Myasis
• Some spp of maggots cause subcutaneous myasis, invade sores
&wounds (wound myasis), burrow under the skin (dermal
myasis)
• Body cavity myasis: Nasal myasis, ocular myasis ear myasis,
myasis of the anus and vagina
• Intestinal myasis-Eggs/larvae of many spp are deposited on
food stuffs may survive the journey to intestinal tract. They may
persist for months producing severe anxiety, and intestinal
irritation

111. Myasis
• Accidental = Facultative Myiasis
• Obligatory Myiasis

112. Myasis
• A number of families of flies e.g. Calliphoridae, Sarcophagidae
and Oestridae are composed of flies that are have either
facultative or obligate parasitic larval forms
• Family: Calliphoridae
• Non- metallic flies e.g. Cordylobia anthropophaga(Tumbu fly),
Auchmeromya senegalensis (Congo floor maggot)
• Metallic flies screw worms e.g. Cochliomya hominivorax(New
World), Chrysomia spp (Old World)
• Blow flies e.g. Lucilia spp (green bottles), Calliphora spp

113. Myasis
Family Sarcophagidae(Flesh flies)
The two genera Sarcophaga and Wohlfahrtia are of medical
importance
Family Oestridae
Subfamilies: Oestrinae, Gasterophilinae, Hypodermatinae and
Cuterebrinae.
Oestrinae, Gasterophilinae, Hypodermatinae are obligatory parasites of
domestic animals
Cuterebrinae has six genera that cause myasis in rodents, monkeys and
livestock
-Dermatobia hominis causes obligatory myasis in people and animals
living in central and south America

114. Facultative Myiasis
• Cutaneous myiasis - usually around wounds
• Larvae normally found in meat or carrion occasionally adapt
to a parasitic existence
• Usually do not invade healthy tissues
• Typically blow flies: species of Calliphora (bluebottles),
Lucilia (greenbottles), Phormia, Sarcophaga and
Wohlfahrtia (flesh flies), Cochliomyia macellaria (secondary
screw-worm), and others

115. Forensic Entomology, 2001. Byrd and Castner, Eds.

116. Forensic Entomology, 2001. Byrd and Castner, Eds.

117. Forensic Entomology, 2001. Byrd and Castner, Eds.

118. Facultative Myiasis
• Enteric Myiasis - accidental ingestion
• 50 species reported - most Muscidae and
Sarcophagidae
• Passive transport of larvae - no development in host
digestive tract
• Severity depends on fly species, number, location
• Genera commonly involved: Musca, Fannia,
Muscina

120. Facultative Myiasis
• Rectal/Urogenital Myiasis – access to intestine via
anus; larvae feed on excrement
• Immature stages may be completed in rectum or
terminal part of intestine
• Can occur in humans under unsanitary conditions
• Primary genera - Fannia, Musca, Sarcophaga

122. Sarcophaga Species

123. Obligatory Myiasis
• Calliphorids (non-metallic):
 Cordylobia anthropophaga - tumbu or mango fly (Africa);
larvae attach and burrow into skin leaving spiracles
exposed - boil-like swelling [cover with paraffin or oil to
extract]
 Auchmeromyia senegalensis - Congo floor-maggot
(Africa); adult looks like tumbu fly, but larvae do not
remain attached; feed nightly from people sleeping on
the floor

124. Obligatory Myiasis
• Calliphorids (metallic):
 Cochliomyia hominivorax - New World screw-worm;
eradicated from US and Mexico, but outbreaks possible
 Chrysomya bezziana - Old World screw-worm
• Sarcophagids (flesh flies):
 Wohlfahrtia magnifica - ear, eye, nose
• Oestrids (bot flies):
 Gasterophilus, Hypoderma, Oestrus, Cuterebra sp., and
Dermatobia hominis (human bot fly)

127. Dermatobia hominis larva
(human bot fly)

128. Control of Myiasis Species
• Control or eradication of the fly population - through
environmental sanitation or chemical control
• Avoidance of infestation (mechanical control) - do not sleep
outdoors or on the ground during fly activity, dress or cover
wounds to avoid fly strikes, use screening
• Treatment of infestation (remove larvae - antibiotic follow-up)