vectors of medical importance

1. Dr. Ambreen Ansar
1

2. BY THE END OF THE LECTURE
STUDENTS SHOULD BE ABLE TO:
• Identify & differentiate the arthropods of medical
importance
• explain briefly taxonomy of arthropods
• identify the arthropod habitat
• explain importance of arthropods
• Advice a control plan for human arthropod borne
infections
2

3. Phylum
Arthropoda
Class
Insecta
Class
Arachnida
3

4. 1. Class
Insecta
(Hexapoda)
A. Diptera
i.
Mosquitoe
s
ii. Flies
iii. Sand
flies
B.
Dictyopter
a
Cockroaches
C.
Hemiptera
Bugs
D.
Anoplura
Lice
E.
Siphonaptera
Fleas
4

5. Class
Arachnida
Ticks
Hard
ticks
Soft ticks
Mites
Trombiculid
mite
Itch mite
5

6. Causative agents transmitted through arthropods
1. Arbovirus infections 1. Yellow fever
2. Dengue fever
3. Japanese B encephalitis
2. Rickettsial infections 1.Epidemic typhus
2. Murine typhus
3. Scrub typhus
4. African tick typhus
5. Q fever
3. Bacterial infections 1. Plague
2. Tick-borne relapsing fever
3. Louse-borne relapsing fever
4. Protozoal infection 1. Malaria
2. African trypanosomiasis
3. South American trypanosomiasis
4. Leishmaniasis
5. Helmenthic infections 1. Filariasis
2. Loasis
3. Onchocerciasis
6

7. Diseases Causing agents transmitted through
arthropods
Disease Agents Vectors
1.Epidemic typhus
2. Murine typhus
3. Scrub typhus
4. Indian tick typhus
5. Q fever
1. R. prowazekii
2. R. Typhi
3. R. orientia
tsutsugamushi
4. R. coronii
5. Coxiella burnetti
1. Louse
2. Flea
3. Larval
Trombiculid mite
4. Tick
5. Ticks
1. Plague
2. Tick-borne
relapsing fever
3. Louse-borne
relapsing fever
3. Bacterial
infections
1. Flea
2. Tick
3. Louse
1. Scabies 1. Direct vector
being the
1. Itch mite
7

8.  FLEA
• Plague
• Flea borne
/Murine/Endemic
typhus
• Chiggerosis
• Hymenolepis diminuta
 LOUSE
• Epidemic typhus
• Relapsing fever
• Trench fever
• Dermatitis
8

9. Hard ticks
• Tick typhus
• Viral encephalitis
• Viral fevers
• Viral
hemorrhagic
fevers
• Tularemia
• Tick paralysis
• Human
babesiosis
 Soft ticks
• Q fever
• Relapsing
fever
9

10. 10

11. TROMBICULID MITE
ITCH MITE/SARCOPTES
SCABEII/ ACARUS SCABEII
 Scrub typhus  Scabies
11

12. LOUSE FLEA
 Human lice are known to
live throughout the hair,
skin, and body parts of
humans. Since they
survive from the blood of
their host, they tend to live
on the hair, or even clothing
of the person.
 Fleas are always found
among the feathers or
hair or within the nests of
animals. The main
introduced species are
the cat flea, the dog flea
and the rat flea
(Xenopsylla cheopis). The
most heavily parasitized
group of mammals are the
rodents (e.g., rats, mice,
squirrels). 12

13. TICKS MITES
 Wooded areas
 Tall brush/grass
 Under plants/leaves to
prevent dehydration
 cut/raked lawns or sports
fields
 Under ground cover (plants)
in yard
 Around stone walls and
woodpiles where mice &
other small mammals live
 Many live freely in the soil
or water, but there are also
a large number of species
that live as parasites on
plants, animals, and some
that feed on mold.
13

14.  A 45-year-old, previously healthy man presented with a
2-day history of increasing fever, myalgia, rigors,
headache, and weakness. The patient had a history of
camping and sleeping on the ground. The patient had
history of rodent exposure.
 Physical examination revealed an acutely ill man with a
blood pressure of 85/57 mm Hg, a respiratory rate of 26
breaths/min, a heart rate of 117 beats/min, and a
temperature of 38.5°C. He had acrocyanosis, severe
muscle pain, and a purpuric rash with evolving gangrene
of the extremities . Skin lesions, lymphadenopathy, and
pneumonia were not present. His abdomen was diffusely
tender, without peritoneal signs. In the ensuing days, he
had progressive gangrene of the fingers, toes, ears, and
nose.
14

15.  A 45-year-old, previously healthy man presented with a
2-day history of increasing fever, myalgia, rigors,
headache, and weakness. The patient had a history of
camping and sleeping on the ground. The patient had
history of rodent exposure.
 Physical examination revealed an acutely ill man with a
blood pressure of 85/57 mm Hg, a respiratory rate of 26
breaths/min, a heart rate of 117 beats/min, and a
temperature of 38.5°C. He had acrocyanosis, severe
muscle pain, and a purpuric rash with evolving
gangrene of the extremities . Skin lesions,
lymphadenopathy, and pneumonia were not present. His
abdomen was diffusely tender, without peritoneal signs.
In the ensuing days, he had progressive gangrene of the
fingers, toes, ears, and nose.
15

16. Early gangrenous changes in the feet of a patient with septicemic plague.
T. Kuberski et al. Clin Infect Dis. 2003;36:521-523
© 2003 by the Infectious Diseases Society of America
16

17.  A 25-year-old Indian rancher was admitted
because of a two-day history of headache, chills,
and fever (40°C). The day before admission, he
began vomiting. The day of admission, an orange-
sized swelling in the left axilla was noted. A
lymph-node aspirate and a smear of peripheral
blood were reported to contain gram-positive
cocci, often in pairs.
 In the 2 weeks prior to becoming ill, the patient
had trapped, killed, and skinned 3 foxes, 4
coyotes, and 1 bobcat. The patient had cut his left
hand shortly before skinning the bobcat.
17

18. 18

19. CHARACTERISTICS OF PLAGUE
Agent
Host
Or occupations involved
Environment
Mode of Transmission
Or vector
Incubation period
19

20.  Causative agent: Yersinia pestis
 Distribution :
Although the number of cases of plague have gradually
declined, foci of the disease still exist in the
 Indian sub continental,
 China,
 South Asia,
 Africa,
 South America and
 Middle East.
 Currently it is not existing in Pakistan.
20

21. • Agent: It is a gram negative, non motile
cocco-bacillus.
• Reservoir: Wild rodents (e.g. field mice,
skunks, gerbils and other small animals.
• Sources of infection:
Infected rodents and fleas
Cases of Pneumonic Plague
21

22. • Age and sex: All ages and both sexes are
susceptible.
• Human activities : Man may come into
contact with natural foci in the course of
hunting, grazing, cultivation, harvesting and
construction activities.
• Movement of People: Plague is associated
with movement of people and cargo by sea
or land.
• Immunity: Man has no natural immunity.
Immunity after recovery is relative.
22

23.  Environmental factors:
• Season: Plague season starts from September till
May.
• Temperature and Humidity: A mean temperature
of 20 - 25°C and relative humidity of 60% and above
are considered favorable for the spread of Plague.
• Human dwellings: Rats infested dwelling.
• Vectors: Rat flea (Xenopsilla cheopsis), X. astia, X.
brasiliensis & Pulex irritans
23
Fleas are wingless insects, 1/16 to 1/8-inch
(1.5 to 3.3 mm) long, that are agile, usually
dark colored.

24. 24

25. 25

26. • Pneumonic plague is very communicable from person to
person
• Bubonic plague is directly communicable only if there is
terminal plague pneumonia.
• Fleas often remain infective for life.
• There is no trans-ovarian transmission.
26

27.  Mode of transmission:
• Most frequently contracted from the bite of an infected
flea.
• Occasionally by direct contact with the tissues of an
infected animal.
• By droplet infection from cases of pneumonic plague.
27

28. • Bubonic plague 2 - 7 days
• Septicemic plague 2 – 7 days
• Pneumonic plague 1 – 3 days
28

29.  There are 4
recognized clinical
forms:
• Bubonic plague:
• In this patient has
sudden onset of
 fever,
 restlessness,
 prostration and
 Later the appearance of a
painful bubo, which is an
inflamed lymph node
commonly of the inguinal
region.
 Vesicular and pustular skin
lesions many develop.
29

30. 30

31. • Pneumonic plague:
• It is the most deadly form.
• Patients develops fever, cough,
hemoptysis.
• Sputum contain Y.Pestis in large
numbers.
• Death occurs in 2-4days after
onset.
• Sylvatic plague:
• It is the name given to plague
that remains endemic in
rodents in jungle. Man is
affected accidentally while
hunting.
31

32. Laboratory diagnosis:
• Staining: It is important to prepare smears of the clinical
material (e.g. bubo fluid, sputum) which should be fixed
with alcohol and then stained with Giemsa’s or waysons
stain to demonstrate bipolar bacilli in the specimen.
• Culture: Of organism from blood taken from patients.
• Serology: Acute and convalescent specimens of blood
sera should be collected for antibody studies.
32

33. Vector
Agent
HostEnvironment
33

34. PREVENTION AND CONTROL OF PLAGUE
Strategies Actions
1. Targeting the
agent
Cases END IT!!
Carriers CT
2. Targeting the
vector
The Flea DDT, BHC or
Carbaryl,
Malathion
3. Targeting the
host
Vaccination Haffkine ; killed
Plague vaccine
4. Targeting the
environment
The rodents Housing,
sanitation, quality
of life
Surveillance of Human & rodent ‘s
34

35. A. Control of cases: (targeting the
agent)
• Early diagnosis:
 Diagnosis of plague can be made readily on clinical
grounds e.g. acute fever and painful lymph node.
 Rat falls (dead rats) provide a useful warning of a
possible outbreak.
• Notification: If a human or rodents case is diagnosed
health authorities must be notified promptly.
35

36. • Isolation : It is recommended whenever
possible.
• Treatment : It should be started without
waiting for confirmation of the disease.
The drug of choice is streptomycin.
Tetracycline is an alternative drug.
• Disinfection: Of sputum discharges and
articles soiled by the patient. Dead
bodies should be handled with aseptic
precautions.
36

37. B. Control of cases: (Carriers)
(targeting the agent)
Chemoprophylaxis : It is a valuable
preventive measure. It should be offered to
all plague contacts & suspected carriers.
The drug of choice is tetracycline.
37

38. 38

39.  The most effective method to break the chain of
transmission (rodent-flea-man) is the destruction
of rat fleas by the proper application of an
effective insecticide.
 In general DDT and BHC should be used.
 In areas where resistance to one or both of
these insecticides dust of carbaryl (2%) or
malathion (5%) should prove effective.
39

40. Useful measurement of the density of fleas
helpful in evaluating the effectiveness of a
spraying programme.
• Total flea index
• Cheopsis index
• Specific percentage of fleas
• Burrow index
40

41. 41

42.  Continuous mass destruction of rodents is
an important plague preventive measure.
Control of rodents should be based on
improvement of general sanitation,
housing and quality of life.
42

43. Surveillance should cover all aspects of
rodents and human plague for example:
• Microbiology,
• Serology,
• Entomology,
• Epidemiology and
• Ecology.
• On the basis of information provided by
surveillance, effective control measures must be
established.
43

44. Detailed study of all cases of plague.
Keep complete record of each case.
Isolate strains of Y. pestis for detailed
biochemical analysis.
Serological survey of target population to
identify untreated infections and
asymptomatic pharyngeal carriers.
Keep an eye on changes in human social
and economic activities and rodent
population.
44

45. Keep a watch on containerized cargoes of
grains and other food crops.
Cooperate and coordinate with adjacent
countries.
Special attention to areas near sea ports
and airports.
45

46.  Immunization with plague vaccine is a
valuable preventive measure.
 Vaccination should be carried out at least a
week before an anticipated outbreak.
 Haffkine ; killed plague vaccine
 It should be given subcutaneously in 2 doses
of 0.5 and 1 ml at interval of 7-14 days.
 Immunity starts 5-7 days after inoculation and
remains for 6 months. At risk population
should be vaccinated biannually.
46

47. 47
Age and gender Primary inoculation Booster doses
1st dose 2nd dose
Adult males 1.0ml 1.5ml 1.0ml
Adult females 0.75ml 1.0ml 0.75ml
Children
1-4 years 0.2ml Double the first
dose
Same as the first
dose
5-10 years 0.3ml
11-16 years 0.4ml
Infants under 6
months of age
Not immunized

48.  It is an essential part of any plague control
programme.
• Education should aim at providing the public with
the facts about plague and at enlisting their
cooperation.
• Emphasis must be placed on the need for the
prompt reporting of dead rats and suspected
human cases.
• Medical practitioners should keep plague in mind
differential diagnosis of any case of fever with
lymphadenopathy.
48

49. 49

50.  They are caused by Rickettsia type of
organism, which are coccobacilli.
They are transmitted to man by an insect or
other arthropods like tick or mite.
They are classified according to their
arthropod vectors into 4 principal diseases.
• Louse borne or epidemic typhus
• Flea born or Murine typhus
• Tick born or Rocky Mountain spotted fever
• Mite born or Scrub typhus (tsutsugamushi disease)
50

51. Diseases Ricckettsial
agents
Insect vectors Mammallion
vectors
nemonics
Typhus group
1. Epidemic
typhus
R. Prowazeki Louse Humans EPL
2. Murine
typhus
R. Typhi Flea Rodents MTF
3. Scrub typhus R.
Tsutsugamushi
Mite Rodents STsM
Spotted fever group
1. Indian tick
typhus
R. Conorii Tick Rodents, dogs TCT
2. Rocky
mountain
spotted fever
R. Ricketsii Tick Rodents, dogs
3. Rickettsial
pox
R. Akari Mite Mice
others
1. Q fever C. Burnetti Nil Cattle, sheep, goats
2. Trench fever Rochalimaea Louse humans 51

52. Sign & symptoms of various Typhus fevers
Epidemic typhus/Louse Murine
typhus/
Endemic/
Flea-borne
Scrub typhus/Mite-
borne
Tick Typhus
Common to all: Headache, fever, chills, rash
•high fever (above 104 degrees
Fahrenheit)
Symptoms
similar to
louse-borne
but milder and
rarely fatal.
Generalized swollen
lymph nodes
Fever which persist for
2-3 weeks
•Macular rash that begins on
the back or chest and spreads red lesion or sore on the
skin at the site of the bite
Maculopapular rash
appears first on
extremeties
•confusion Tiredness
•stupor and seeming out of
touch with reality
cough
•low blood pressure
(hypotension)
Punched out ulcer
covered with blackened
scab (eschar)
Lesion or eschar at the
site of bite•eye sensitivity to bright lights
52

53. It is the only fever in typhus group which
appears in epidemic form.
Causative organism : Rickettsia
prowazeki
Vector: Pediculus humanus capitis
53
The head louse (Pediculus humanus
capitis) is an obligate ectoparasite , a
wingless insects spending its entire life on
the human scalp and feeding exclusively
on human blood.

54.  Host factors: Following factors favors its spread
• Overcrowding
• Personal unhygienic condition
• Malnutrition
• Louse infestation
 Incubation period : 10 -14 days
 Clinical features: The onset of the disease is sudden in
which patient develops fever with chills, headache which
usually last for two weeks. The patient also develops rash
which initially is papular later on it becomes macular and
petechial rash which extends to arms and legs.
 Diagnosis: It is made by serological test called Weil Felix
reaction.
54

55. 55
Along with Rickettsia
prowazekii and Bartonella
quintana, Borrelia recurrentis is
one of three pathogens of
which the body
louse (Pediculus humanus
humanus) is a vector

56. Head lice and petechial rash caused by Louse bite 56

57. Preventive measures:
• Apply 10% DDT powder to clothes and bodies of person
who are infected with lice.
• Living conditions should be improved.
• Frequent baths and washing of clothes should be
encouraged.
57

58.  Control of infected persons, contacts and
environment:
• Notify to local health authority
• Isolation is not required after the patient has been
deloused
• Concurrent disinfection: Apply insecticide powder to
clothes and bedding of patient and contacts.
• Terminal disinfection: If death occurs before delousing,
thorough application of insecticide to body and clothing.
• Quarantine : susceptible contacts may be released
after applying DDT
• Immunization of all contacts
• Treatment of cases with tetracycline or
chloremphenicol for 3 – 4 days.
END IT
58

59.  Epidemic measures:
• Delousing : Insecticides should be applied to all
contacts.
• Immunization
 International measures:
• Government should notify WHO
• Ships aircrafts and land transport arriving from
typhus areas are given thorough application of
residual insecticides.
• International travelers from Typhus endemic areas
are allowed to enter after application of DDT
• Those persons entering typhus areas should get
themselves vaccinated.
59

60. Causative organism: Rickettsia conorii
Reservoir: Wild animals, chiefly rodents and
dogs. Tick itself.
Mode of transmission:
The infection is transmitted by the bite of hard
tick known as Dermacentor Andersoni.
Contamination of skin with crushed tissues or
faeces of an infected ticks.
60

61. Incubation period: 3 - 7 days
Clinical features: It is the mild form of
typhus characterized by a black spot at the
site of tick bite. The regional lymph nodes
enlarge and the body is entirely covered
with a maculopapular rash. Fever occur
after 3 -7 days of bite. Rash appears first
on extremities
Diagnosis: The weil-felix reaction is usually
positive with proteus 0X2.
61

62. 62

63.  Avoid infected localities and animals.
 To avoid ticks, walk in the center of trails
and avoid walking through tall bushes or other
vegetation.
 Use a repellent with DEET (on skin or clothing)
or permethrin (on clothing and gear). Repellents
containing 20% or more DEET (N, N-diethyl-m-
toluamide) can be applied to the skin and can
protect up to several hours.
 Wear tick proof clothes impregnated with
dimethylphthalate in infected areas.
63

64. Frequent examination of whole body, if
found they should be removed with
forceps.
Vaccination for contacts:2 injections with
10 days apart.
Treatment with antibiotics.
Health education of people regarding
mode of transmission and its prevention.
64

65. How to
Prevent
tick bite
65

66. Causative organism: Rickettsia Typhi
Distribution : World wide appears to be more prevalent in
South East Asia.
Vector: Rat flea( X. cheopsis)
Reservoir : Rattus rattus and Rattus norvegicus
Mode of transmission:
• Inoculation into skin of faeces of infected fleas.
• Inhalation of derived infective faeces.
Incubation period : 6 – 14 days
66

67. 67

68. Period of communicability: not communicable from
man to man.
Susceptibility: is general
Immunity: One attack of murine typhus gives immunity
which is not always permanent
Clinical features : Resembles epidemic typhus but
milder in intensity.
Diagnosis : Weil felix reaction is usually positive with proteus
OX-19 in 2nd week.
Methods of control:
• Preventive measures: Apply DDT powder to rat runs and
burrows to kill rat fleas.
68

69. Control of Infected persons, contacts and
environment:
• Notification to local health authority
• No need of isolation
• Treatment of the cases
Epidemic measures: Wide spread use of DDT
markedly reduces the flea index of rats.
69

70. a patient presents with persistent fever of 5
days' duration without explanation, there is
a history of exposure to cats infested with
wingless dark coloured insects approx
2-3mm long. Maculopapaular rash,
hypotension and stupor is positive on
examination. No bite marks are visible on
the body.
70

71. Causative organism: Rickettsia orientalist or
R.tsutsugamushi.
 Vector : The disease is transmitted to man by larval
mites.
 Mode of transmission: by the bite of infected larval
mites. It is not directly transmitted from persons to
persons.
 Incubation period : 6 -14 days
71

72.  Clinical features: Sudden onset of fever with chills,
conjunctional infection and lymphadenopathy. Cutaneous rash
appears on the 5th day.
 Diagnosis : The causative organism can be recovered from
the blood during the febrile period. A positive weil felix reaction
is usually obtained with proteus OXK.
72

73. • Preventive measures:
 Avoid infected localities
 Insecticides should be applied on individual clothes and
body if he has to work in infected areas.
 No need of isolation and quarantine
 No effective vaccine is available but prophylacticaly
chloramphenicol can be taken.
• .
73

74. • Treatment :
 Wash bite site with soap and water
 Apply ice pack to bite area to reduce swelling, itching
and pain.
 In children trim fingernails to prevent further injury from
scratching.
 Topical Benzocaine or lidocaine can be use for 7 days
max to relieve itching and irritation.
 Calamine, oral antihistamine and topical hydrocortisone
may be beneficial.
 Broad spectrum antibiotics are very effective in treating
scrub typhus
74

75. 75

76. 76

77. 77
Trombiculid
Mite
Flea Louse Hard tick

78. 78
Clinical presentations of Typhus fevers vary with
the causative agent and patient; however, common
symptoms that typically develop within 1–2 weeks of
infection include fever, headache, malaise, rash,
nausea, and vomiting. Many rickettsioses are
accompanied by a maculopapular, vesicular, or
petechial rash or sometimes an eschar at the site of
the tick bite.
Scrub typhus should be suspected in patients with a
fever, headache, and myalgia after recent travel to
Asia; eschar, lymphadenopathy, cough, and
encephalitis may be present.
Patients with murine or epidemic typhus usually
present with a severe but nonspecific febrile illness,
and approximately half will also present with a rash.

79. Relapsing fever is a recurring febrile
disease transmitted to humans by ticks
(endemic form) and by body lice (epidemic
form). It is caused by several
different Borrelia species.
79

80. Rash of Scabies
Scabies is a contagious skin
disease marked by itching
and small raised red spots,
caused by the itch mite.
80

81. Life cycle from egg
to adult form
takes10 to 15
days.
Adult mite live for 1
to 2 months.
Mode of spread:
1. Close contact
(house hold
infection)
2. Contaminated
Clothes.
81

82.  Site of Lesions:
The disease
classically affects
• Hands and wrist 63%
• Extension aspect of
elbow 10.9%
• Axilla, buttocks, lower
abdomen
• Palm in infants are all
common sites of
infestation.
82

83.  Essential to treat all the members of
family whether or not they appears to be
infested.
 Before start of treatment patient is given a
god scrub with soap and hot water.
 Benzyl benzoate 25% is an effective
sarcopticide. It should be applied with a
paint brush or shaving brush to every inch
of the body below the chin including the
sole of feet and allowed to dry.
83

84.  Application should be repeated after 12 hours.
 Other chemicals which are effective:
• HCH: 0.5 to 1.0% strength of gamma HCH
(lindane) in coconut oil or any vegetable oil.
Lindane is rarely used because of its side effects.
• Tetmoslol 5% of its solution is effective, there
daily application are recommended.
• Sulphur ointment: 2.5 to 10% daily for 4 days is a
cheap remedy.
84

85. Before treatment, wash underwear, towels,
and sleepwear in hot water. Items that
cannot be washed or dry-cleaned can be
decontaminated by removing from any
body contact for at least 72 hours.
Vacuum the carpets and upholstered
furniture.
Use calamine lotion and soak in a cool
bath to ease itching.
Take an oral antihistamine
85

86. 86

87. 87