CHN

1. Vector borne diseases
Presented by
Deepa Manandhar
Lecturer
Community Health Nursing

2. Vector
• A vector is a living organism that transmits an infectious agent
from an infected animal to a human or another animal. Vectors are
frequently arthropods, such as mosquitoes, ticks, flies, fleas and lice.

3. introduction
• Vector-borne diseases are infections transmitted by the bite of infected
arthropod species, such as mosquitoes, ticks, bugs, sandflies, and
blackflies.

4. introduction
• Vector-borne diseases account for more than 17% of all infectious
diseases, causing more than 700 000 deaths annually. They can be
caused by either parasites, bacteria or viruses.
• Many of vector-borne diseases are preventable, through protective
measures, and community mobilization.
-WHO 2nd march 2020

5. Vector borne diseases
• Dengue
• Malaria
• Japanese Encephalitis
• Lymphatic Filariasis
• Kalazar

6. malaria

7. introduction
Malaria is transmitted by:
a. Female anopheles mosquito
b. Male anopheles mosquito
c. Culex mosquito
d. Aedes mosquito
ANS: a

8. introduction
• Malaria is a protozoal disease caused by infection with parasites of the
genus Plasmodium and transmitted to man by certain species of
infected female Anopheline mosquito.
• In the human body, the parasites multiply in the liver, and then infect
red blood cells.

9. Problem statement
• In 2021, there were an estimated 247 million cases of malaria
worldwide.
• The estimated number of malaria deaths stood at 619 000 in 2021.

10. Problem statement
• In 2076/2077, there were total 619 of malaria positive cases reported.
– P. falciparum: 56
– P. vivax: 563

11. Agent
Species of Plasmodium infective to humans:
Plasmodium falciparum
Plasmodium vivax
Plasmodium ovale
Plasmodium malariae
Plasmodium knowlesi

12. Reservoir of infection
Man is the only important reservoir of human malaria.

13. Host factors
AGE : Malaria affects all ages.
SOCIO-ECONOMIC DEVELOPMENT Malaria has demonstrated the
relationship between health and socio-economic development. It is
generally accepted that malaria has disappeared from most developed
countries as a result of socio-economic development.

14. Host factors
HOUSING:
• The ill-ventilated and ill-lighted houses provide ideal indoor resting
places for mosquitoes.

15. Host factors
OCCUPATION: Malaria is predominantly a rural disease and is closely
related to agriculture practices.
HUMAN HABITS : Habits such as sleeping out of doors, nomadism,
refusal to accept spraying of houses, not using measures of personal
protection (e.g. bed nets) influence man-vector contact.

16. Environmental factors
(a) SEASON : Malaria is a seasonal disease. It is more common during
the rainy season.
(b) TEMPERATURE: Temperature affects the life cycle of the malaria
parasite. The optimum temperature for the development of the malaria
parasite in the insect vector is between 20 deg. to 30 deg.C

17. Mode of transmission
Vector transmission
Direct transmission
Congenital Malaria

18. Mode of transmission
a) VECTOR TRANSMISSION: Malaria is transmitted by the bite of
certain species of infected, female, anopheline mosquitoes. A single
infected vector, during her life time, may infect several persons. The
mosquito is not infective unless the sporozoites are present in its
salivary glands.

19. Mode of transmission
(b) DIRECT TRANSMISSION: Malaria may be induced accidentally
by hypodermic intramuscular and intravenous injections of blood or
plasma, e.g., blood transfusion, malaria in drug addicts
(c) CONGENITAL MALARIA:
Congenital infection of the newborn from an infected mother may also
occur, but it is comparatively rare.

20. Incubation period
12 days for P. falciparum
14 days for P. vivax and ovale
30 days for P. malariae
9-12 days for P. knowlesi
 Most common worldwide is P. vivex
 The deadliest is P. falciparum. It causes cerebral malaria, the most
severe pathology caused by the malaria parasite.

21. Clinical features
• The typical attack comprises three distinct stages, i.e., the cold stage,
the hot stage and the sweating stage. These are followed by an afebrile
period in which the patient feels greatly relieved.

22. Clinical features
• lassitude, headache, nausea and chilly sensation followed in
an hour or so by rigors. The temperature rises rapidly to 39-
41°C.
• In early part of this stage, skin feels cold; later it becomes
hot.
Cold stage
• The skin is hot and dry to touch.
• Headache is intense
• The pulse is full and respiration rapid. This stage lasts
for 2 to 6 hours.
Hot stage
• Fever comes down with profuse sweating.
• The temperature drops rapidly to normal and skin is
cool and moist.
• This stage lasts for 2-4 hours.
Sweating stage

23. Treatment
• Chloroquine is given as anti-malarial drug.
• Chloroquine resistant P. falciparum requires treatment with oral
quinine given concurrently with pyrimethamine with sulphadoxine and
a sulfonamide (e.g. sulfadiazine)
• Relapse require same treatment, or quinine alone, followed by
tetracycline

24. Treatment
• Artemisinin-based combination therapies (ACTs) are the most
effective antimalarial medicines available today and the mainstay of
recommended treatment for Plasmodium falciparum malaria, the
deadliest malaria parasite globally.

25. Preventive measures
• Prevention of malaria is currently based on two complementary
methods: chemoprophylaxis and protection against mosquito bites.
• Malaria prophylaxis is not necessary for in-country travel within
Nepal. ƒ
Prophylactic medication for malaria is recommended for
Nepalese traveling to countries with areas of malaria transmission. ƒ
The medicine of choice depends on the parasite species and resistance
profile in the destination country.

26. Malaria control programme
• Nepal`s malaria control programme began in 1954, mainly in the terai
belt of central Nepal with support from United States.
• Nepal`s National Malaria Strategic Plan (2014-2025)
Vision: Malaria Elimination in Nepal by 2025
Goal: Reduce the indigenous malaria cases to zero by 2022 and sustain
thereafter.

27. Current Achievement
• In 2077/78, National Malaria program has achieved 90% reduction in
indigenous malaria cases compared to 2071/72.

28. dengue

29. dengue
• Dengue is an infectious tropical disease caused by the dengue virus
(DEN-1-4) & transmitted by the Aedes species mosquito.

30. Problem statement
• The global incidence of dengue has grown dramatically with about
half of the world's population now at risk. Although an estimated 100-
400 million infections occur each year, over 80% are generally mild
and asymptomatic.

31. Problem statement- Nepal
• Between January to 28 September 2022, a total of 28109 confirmed
and suspected dengue cases and 38 confirmed deaths due to dengue
have been recorded, affecting all seven provinces of Nepal.
• According to the Epidemiology and Disease Control Division (EDCD)
of the Ministry of Health and Population, the highest number of new
cases in 2022 have been reported in the districts of Kathmandu
(n=9528; 33.8%), Lalitpur (n=6548; 23.2%), and Makwanpur
(n=2776, 9.8%).

32. Problem statement- Nepal
• In sunsari from 076-1-30 to 076-4-22
2,803 cases without any mortality

33. agent
• Dengue is caused by a virus of the Flaviviridae family and there are
four distinct, but closely related, serotypes of the virus that cause
dengue (DENV-1, DENV-2, DENV-3 and DENV-4).

34. vector
• Aedes aegypti and Aedes Albopictus

35. Aedes aegypti
• Considered the primary vector of DENV.
• It could breed in natural containers such as tree holes but nowadays it
has well adapted to urban habitats and breeds mostly in man-made
containers including buckets, mud pots, discarded containers and used
tyres, thus making dengue an insidious disease in densely populated
urban centers.

36. Aedes aegypti
• Ae. aegypti is a day-time feeder; its peak biting periods are early in the
morning and in the evening before sunset.
• Once a female has laid her eggs, these eggs can remain viable for
several months in dry condition, and will hatch when they are in
contact with water.

37. Aedes ALBOpictus
• A secondary dengue vector.
• It favors breeding sites close to dense vegetation including plantations
which is linked to increased risk of exposure for rural workers.
• Similar to Ae. aegypti, Ae. albopictus is also a day biter

38. reserviour
man together with the vector acts as reservoir also because the virus is
transmitted transovarially.

39. transmission
Transmission through mosquito bite
Maternal transmission
Other transmission modes

40. Transmission through mosquito bite
• The virus is transmitted to humans through the bites of infected female
mosquitoes

41. Maternal transmission
The primary mode of transmission of DENV between humans involves
mosquito vectors. There is evidence however, of the possibility of
maternal transmission (from a pregnant mother to her baby).

42. Other transmission modes
Rare cases of transmission via blood products, organ donation and
transfusions have been recorded. Similarly, transovarial transmission of
the virus within mosquitoes have also been recorded.

43. Incubation period
3-14 days, commonly 5-7 days

44. Clinical features
• may be asymptomatic or may cause febrile illness as dengue fever,
dengue haemorrhagic fever including dengue shock syndrome.

45. Clinical features

46. Un differentiated fever
Develop a simple fever indistinguishable from other viral infection
• Maculo papular rash may accompany fever
• Gastrointestinal symptoms are common.

47. Classical dengue Fever
The onset is sudden, with chills and high fever
• Intense headache
• Muscle and joint pains.( also known as breakbone fever)
• Within 24 hour retro orbital pain, particularly on eye movements or
eye pressure
• Photophobia
• extreme weakness, anorexia, abdominal tenderness, sore throat
• The skin eruptions appear in 80% of cases

48. Dengue haemorrhagic fever
• Headache, high fever (lasting 2-7 days)
• Rash, and evidence of hemorrhage in the body (Petechiae)
• Bleeding in the nose or gums
• Black stools, or easy bruising are all possible signs of hemorrhage.
• Rising hematocrit value (>20% of baseline)
• Hepatomegaly
• Moderate to marked thrombocytopenia

49. Dengue Shock syndrome (DHF+SHOCK)
As dengue vascular permeability progresses, hypervolemia worsens and
results in shock.
Criteria:
– Tachycardia, cool extremities, delayed capillary refill, weak pulse,
lethargy
– Hypotension
– Pulse pressure ≤ 20 mm Hg

50. management
• No specific antiviral treatment for the DENV infection.
• Most patients recover without complication.
• Symptomatic treatment
• Management of dengue fever:
– Encourage intake of oral rehydration (ORS), fruit juice and other
fluids.
– Tab. Paracetamol for fever

51. management
Management of DHF
• Febrile phase is treated same as dengue fever
• IV fluid therapy- crystalloid and colloid
• Blood transfusion
• Management of Dengue Shock Syndrome
• Oxygen therapy
• IV fluid- dextran, haemacele
• Whole blood transfusion/platelet transfusion

52. Control Measures
Mosquito control
• In late 2015 and early 2016, the first dengue vaccine,
Dengvaxia (CYD-TDV) by Sanofi Pasteur, was
registered in several countries for use in individuals
9-45 years of age living in endemic areas.
Vaccination

53. management
Dengue fever is transmitted by:
a. Aedes mosquito
b. Anopheles mosquito
c. Mansonoides mosquito
d. Culex mosquito
ANS: a

54. management
Which is not true about dengue hemorrhagic fever:
a. Thrombocytopenia
b. Hepatomegaly
c. Shock
d. Plasma leaking
ANS: c

55. Japanese Encephalitis

56. introduction
• Japanese encephalitis (JE) is a mosquito-borne encephalitis caused by
a group B arbovirus (Flavivirus) and transmitted by culicine
mosquitoes.
• It is a zoonotic disease, i.e., infecting mainly animals and incidentally
man.

57. Problem statement
• JE is the main cause of viral encephalitis in many countries of Asia
with an estimated 68 000 clinical cases every year.
• 24 countries in the WHO South-East Asia and Western Pacific regions
have endemic JEV transmission, exposing more than 3 billion people
to risks of infection

58. Problem statement
• Although symptomatic Japanese encephalitis (JE) is rare, the case-
fatality rate among those with encephalitis can be as high as 30%.
• Permanent neurologicol psychiatric sequelae can occur in 30%–50%
of those with encephalitis.

59. Epidemiological features
HOST FACTOR:
• Reservoir – Pigs, bats, ardeid birds
• Incidental hosts –humans
INCUBATION PERIOD: -5 to 15 days

60. transmission
Transmitted by culex mosquitoes
• The basic cycles of transmission are :
– Pig —> Mosquito —> Man
– The Ardeid bird —» Mosquito —> Ardeid bird

61. Transmission cycle

63. Clinical features
Prodromal stage
Acute encephalitic
stage
Late stage and
sequelae

64. Prodromal stage
• Fever
• Headache
• GI disturbances
• Lethargy and malaise
• The duration of this stage is usually 1-6 days.

65. Acute encephalitic stage
• Fever 38-40.7 degree C
• Nuchal rigidity
• Focal CNS signs
• Raised ICP
• Difficulty of speech
• Dystonia
• Ocular paralysis
• Altered sensorium progressing to coma

66. Late stage and sequelae
Characterized by the persistence signs of CNS injury such as:
• Mental impairment
• Epilepsy, abnormal movements
• Speech impairment

67. Prevention

68. vaccination
JE is endemic in the Terai, with maximum number of cases occurring in
the western districts of Banke, Kanchanpur and Kailali. JE
immunization with CD-JEVAX at 1 year of age is included in the
national immunization program of Nepal with excellent results.

69. Vector control
• Elimination of mosquito breeding areas
• Adult and larvae control
• Cover tightly all water containers, wells and water storage tanks
• Use of mosquito nets, insecticides or coil incenses to repel mosquitoes

70. Lymphatic filariases

71. introduction
• The term "lymphatic filariasis" covers infection with three closely
related nematode worms -Wuchereria bancrofti, B. malayi and B.
timori.
• Lymphatic filariasis impairs the lymphatic system and can lead to the
abnormal enlargement of body parts, causing pain, severe disability
and social stigma.
• All three infections are transmitted to man by the bites of infective
mosquitoes.

72. Problem statement
• 51 million people were infected as of 2018, a 74% decline since the
start of WHO’s Global Programme to Eliminate Lymphatic Filariasis
in 2000.

73. Problem statement
• Nepal is one of the 73 countries listed by WHO as being endemic for
LF.
• Nepal conducted LF mapping in 2001 and 2005 and remapping in
2012 by using ICT (Immuno chromatography Test), which revealed
13% average prevalence of LF infection in the country, ranging from
<1% to 39%.

74. Problem statement
• The LF mapping completed in 2005 by using ICT
(Immunochromatograhy) card revealed that 60 out of 75 districts as
endemic for lymphatic filariasis in the country.
• Wuchereria bancrofti is the only recorded parasite in Nepal.

75. The EDCD formulated a National Plan of Action for the Elimination of
Lymphatic Filariasis in Nepal (2003–2020) by establishing a National
Task Force.
The division initiated mass drug administration (MDA) in Parsa district
in 2003, which was scaled up to all endemic districts by 2069/70 (2013).

76. agent
• Wuchereria bancrofti, Brugia malayi, B.timori are the worms causing
lymphatic filariasis.

77. reservoir
• The main reservoir is man, who harbours microfilariae in the blood.

78. Host factors
(a) AGE: All ages are susceptible to infection
(b) SEX : In most endemic areas the rate is higher in men.
(c) MIGRATION : The movement of people from one place to another
has led to the extension of filariasis into areas previously non-endemic.

79. Host factors
d) IMMUNITY : Man may develop resistance to infection only after
many years of exposure.
(e) SOCIAL FACTORS : Lymphatic filariasis is often associated with
urbanization, industrialization, migration of people, illiteracy, poverty
and poor sanitation.

80. Mode of transmisson
• Filariasis is transmitted by the bite of infected vector mosquitoes.
• The parasite is deposited near the site of puncture.
• It passes through the punctured skin or may penetrate the skin on its
own and finally reach the lymphatic system.

81. Incubation period
• The incubation period is about 8 to 16 months. This period may
however be longer.

82. Clinical features
•
• Eosinophilic lung indicated by eosinophilia,
chronic bronchitis and asthma.
Allergic
• Acute (such as lymphangitis of the legs and
genitals) and chronic (such as lymphadenitis in
inguinal and femoral regions)
Inflammatory
• Soft edematous swelling due to blockage of
lymphatics followed by fibrotic changes give
rise to the picture of elephantiasis.
• Soft or hard swelling of testes, legs and feet are
common. Sometimes arms, breasts, vulva and
penis are also involved.
Obstructional

83. Preventive and control measures
1. Mass Chemotherapy
2. Mosquito Control

84. Mass chemotherapy
• Annual Mass Drug Administration(MDA) of single doses of
Albendazole plus Diethylcarbamazine (DEC) is being implemented,
treating the entire at-risk population.
• MDA is being continued for 6 years or more to reduce the density of
microfilariae circulating in the blood of infected individuals to levels
that will prevent mosquito vector from transmitting infection.

85. Mass chemotherapy
• Objective of MDA is to reduce the prevalence of the infection in the
entire community
• The MDA should have greater than 65% epidemiological coverage
(proportion of individuals treated in a district) at each round.

86. Mass chemotherapy
• From this year, triple drug regimen (including Ivermectin) has been
introduced in Nepal.
• This regimen is more effective in clearing microfilaria faster than DA
MDA.

87. kalazar

88. Kalazar
Visceral leishmaniasis or Kala-azar is a vector-borne disease by the
protozoan parasite Leishmania donovani and transmitted by the sandfly,
Phlebotomus argentipes.

89. introduction
There are 3 main forms of leishmaniases:
• Visceral (the most serious form because it is almost always fatal
without treatment),
• Cutaneous (the most common, usually causing skin ulcers)
• Mucocutaneous (affecting mouth, nose and throat).

90. epidemiology
 An estimated 700 000 to 1 million new cases occur annually.
 Only a small fraction of those infected by parasites causing
leishmaniasis will eventually develop the disease.

91. Epidemiology in nepal
• National program initially identified 12 districts as kala azar endemic
districts.
• 6 other districts were included in the list in 2016 because sporadic
cases were consistently being reported by these 6 districts.
• Currently 18 districts are considered endemic.

92. Epidemiology in nepal

93. Agent factor
• The leishmania are intracellular parasites.
• Leishmania donovani →Kala-azar (VL)
• L. tropica → cutaneous leishmaniasis
• L. braziliensis → muco-cutaneous leishmaniasis.
But visceral forms may produce cutaneous lesions, and cutaneous forms
may visceralize.

94. Reservoir of infection
• There is a variety of animal reservoirs, e.g., dogs, jackals, foxes,
rodents and other mammals

95. Host factors
• Kala-azar can occur in all age groups.
• Males are affected twice as often as females.
• Migration from endemic to non-endemic area.
• Socio-economic status
• Occupation: People who work in various farming practices, forestry,
and fishing have a great risk of being bitten by sand flies.

96. transmission
• Kala-azar is transmitted from person to person by the bite of the
female phlebotomine sandfly.
• Transmission of kala-azar has also been recorded by blood transfusion,
and is also possible by contaminated syringes and needles.

97. Incubation period
• The incubation period in man is quite variable, generally 1 to 4
months; range is 10 days to 2 years.

98. Clinical features
Kala-azar (VL) :
Classical features: – fever, splenomegaly and hepatomegaly
accompanied by anaemia and weight-loss
Darkening of the skin (face, hands, feet and abdomen)
Lymphadenopathy (uncommon)

100. Clinical features
Muco-cutaneous leishmaniasis
• Ulcers similar to the oriental sore (CL) appear around the margins of
mouth and nose.
• It can mutilate the face so badly that victims may become social
outcasts.

102. diagnosis
Clinical Examination
Laboratory Examination
• Haematological findings: leucopenia, anaemia, raised ESR,
• Serological tests: DAT, rk39 dipstick test,
• Leishmanin (Montenegro) test

103. treatment
Liposomal Amphotericin B has been introduced in Nepal since 2015
with support from WHO.
The national program recommends the use of the following drugs for
Kalazar treatment:

104. treatment
• Liposomal amphotericin B infusion (15 mg/Kg in 3 doses or single
dose of 10 mg/Kg). OR
• Combination therapy regimens:
• (i) Miltefosine + Paromomycin and
• (ii) L-AmB (5mg/Kg on D1) + Paromomycin.
• In children (< 5 years), pregnant and breast feeding women and
women of child bearing age group, the preferred regimens will be L-
AmB or combination of L-AmB + Paromomycin

105. Vector control strategies
1. Anti-adult Measures
Residual spraying
Space application
Individual protection

106. Vector control strategies
2. Anti-larval measures:
Larvicides
Source Reduction
Integrated control

107. Anti-adult measures
(i) Residual spraying : The spraying of the indoor surfaces of houses with residual
insecticides (e.g., DDT, malathion, fenitrothion) is still the most effective measure to
kill the adult mosquito. It has been observed that discontinuation of spraying has
very often led to the resurgence of malaria. This implies that spraying once applied
may need to be continued for an indefinite period.
(ii) Space application : This is a major anti-epidemic measure in mosquito-borne
diseases. It involves the application of pesticides in the form of fog or mist using
special equipment. Outdoor space sprays reduce vector population quickly.

109. Anti-adult measures
iii) Individual protection : Man-vector contact can be reduced by other preventive
measures such as the use of repellents, protective clothing, bed-nets· The methods of
personal protection are of great value when properly employed.

110. Anti-larval measures
i) Larvicides : With the increase in insecticide resistance, the older methods of
mosquito control have now become promising. Some modern larvicides such as
temephos ( organophosphate larvicide) which confer long effect with low toxicity
are more widely used.
ii) Source reduction : Techniques to reduce mosquito breeding sites (often called
source reduction) which include draining and flushing of water collections;
filling of water logged areas; proper maintenance of water levels and intermittent
irrigation in dams and canals . Whenever practicable, measures for the
improvement of the environment by the permanent reduction of sources should
be instituted.

111. Anti-larval measures
(iii) Integrated control : In order to reduce too much dependance on residual
insecticides, increasing emphasis is being put on "integrated" vector control
methodology which includes bio environmental and personal protection measure.
One of the safest and interesting methods in mosquito control is the use of
biological agents that eat or destroy the larvae. Eco-friendly larvivorous fish such as
the top water minnow or mosquito fish (Gambusia affinis) can be effectively used
to control the mosquito population.

112. MCQs
1.The Animal that is considered as “amplifier host” of the virus, in
Japanese encephalitis is
a.Man
b.Cattle
c.Horse
d.Pig
ANS: d

113. 2. Kala-azar is transmitted by
(a) mosquito
(b) Housefly
(c) ticks
(d) Sand fly
ANS: d

114. 3. How many district are endemic for lymphatic filariasis in Nepal?
a. 75
b. 77
c. 60
d. 50
ANS:c

115. 4. Which mosquito species are primarily responsible for Dengue fever?
a.Aedes albopictus
b.Anopheles
c.Aedes aegypti
d.Culex
ANS: c

116. 5. Dengue fever incubation period ranges from
a.4-12 days
b.3-14 days
c.14-28 days
d. 28-32 days
ANS: b

117. 6. Which mosquito species is responsible for JE?
a. Culex
b. Anopheles
c. Aedes
d. Mansonia
ANS: a