The document outlines entomological field techniques for collecting mosquitoes and sand flies, emphasizing their role in vector-borne disease transmission. Various equipment, including mouth aspirators and traps, was tested during a field study in Kathmandu, Nepal, to assess mosquito populations and their disease relationships. The findings aim to enhance vector control planning and monitoring efforts against diseases such as malaria and dengue.

1. Field Report
Entomological field techniques
for mosquito and sand fly
collection
By
Prakash Dhakal
Public Health Microbiology
Central Department of Microbiology
Tribhuvan University
Kirtipur
Nepal

2. Abstract:
Entomological field visit was done. Relationship between vector and causative
agents of some diseases was studied. Different entomological methods for
collecting mosquitoes and sand flies were observed and handled. Mouth aspirator,
BG Sentinel trap, CDC light trap, adult emergence trap and ovitrap were observed
and handled.
Keywords: Mosquito, Sand fly, equipments, Mouth aspirator, BG sentinel trap,
CDC light trap, Adult emergence trap
Introduction:
Mosquitoes and sand flies are
important insect pests and control
efforts can be justified when they
represent a significant “nuisance” or
threat to public health. Mosquitoes are
considered a nuisance because they
can 1) decrease the quality of life of
local residents by annoying and
bother people (including adverse
reactions to their bites) in and around
their homes or in recreational areas or
2) by reducing property values,
slowing economic development of an
area, reducing tourism, or adversely
affecting livestock production in
localities that produce large adult
populations1
.
Different mosquito and sandflies are
found to transmit different diseases.
Mosquitoes Culex tritaeniorhynchus
and Culex gelidae transmit Japanese
Encephalitis. Aedes spp. transmits
Dengue, Yellow fever and
Chikengunya. Anopheles spp.
transmits malaria. Sandflies
(Phlebotomus spp.) transmit
leishmaniasis and sandfly fever. A
control of these diseases can only be
done by a control in the vector
population.
Mosquitoes and sand flies both are
holometabola insects. Mosquitoes
pass through the egg, larval, pupal
and adult stages during their life
cycle. There are four larval instars.
All stages except the egg stage are
mobile. Female mosquitoes may lay
their eggs either on moist soil or on
the surface of water. The 1st-instar
larva is very small. As the larvae pass
through their four instars, they

3. become larger after each moult.
During the larval and pupal stage,
mosquitoes remain in the water. Both
these stages are adapted for
swimming. The larvae swim as they
go to and from feeding to other
activities, like swimming to the
surface to obtain air. Many people call
them 'wrigglers' because of the way in
which they swim. The larvae of most
species can be seen resting at the
surface, hanging from the surface film
by their respiratory siphon. The pupal
stage looks like an inverted comma.
Some people think the pupae look like
miniature tadpoles. They use their
flattened, paddle-like 'tails' to propel
themselves through the water. They
do not feed during this transitional
stage of development, as they
transform from larvae to adults. When
mature, the skin of the pupa splits
open along its back and the fresh,
adult mosquito slowly emerges into
the air. After resting on the surface of
the water for a few minutes, the adult
mosquito usually moves to a sheltered
spot close by to allow its outer
skeleton and wings to harden. Soon
after emergence, mating takes place.
Mating usually occurs in mating
swarms, typically within 3 to 5 days
after the adults emerge. Females are
attracted to the mating swarm and
soon fertilized. Females mate once,
remain fertilized for life and are the
only sex to seek blood from hosts.
The life cycle of sandflies also
includes four stages: egg, larva (4
instars), pupa and adult. The eggs are
elongated oval-shaped, pale at first
and darkening on exposure to air with
a single black “eye spot”. The larvae
emerge through a J-shaped fissure and
are legless and whitish with a dark
head capsule. Those of the first instar
can be distinguished by the presence
of two caudal bristles, all subsequent
instars bearing four. Fourth instar
larvae also have a prominent sclerite
on the dorsum of the penultimate
segment. The pupae are golden brown
and are affixed to the surface of the
substrate in which they developed by
the final larval exuvium. Shortly
before emergence the wings and eyes
turn black. Male sand flies emerge
about 24 h before females, allowing
their external genitalia time to rotate
180° to the correct position for mating
before females have emerged.
Although there have been no studies
of sand fly development time in
nature, the time from oviposition to
adult emergence at ambient
temperature is around 4-6 weeks.
The population of mosquitoes and
sandflies is affected by humidity and

4. temperature. Their number increase
during warm and humid climates.
Life cycle of mosquito is completed
in water and soil while that of
sandflies is completed in moist soil.
Control at larval and pupal stage of
mosquitoes is feasible while it is not
so for sandflies. Larvicides are not
very effective for sandflies because of
their unlocalised presence in soil.
Efforts for vector control are made
worldwide. Epidemiology and
Disease Control Division of the
Ministry of Health and Population of
Government of Nepal plans and
monitors control of vector of malaria,
Japanese encephalitis, kala-azar, etc.
Accuracy in mosquito population
levels has long been major component
of control efforts. Early attempts
measuring mosquito populations
consisted of counting, capturing and
identifying the species attracted
humans. Although new techniques
provided useful overview of the
mosquitoes causing nuisance the
residents of given area. Different
entomological field techniques used
for vector sampling so that a study
about vector can be done and
planning and monitoring of plan can
be done.
Objective:
To operate different equipments in the
field for collecting mosquito and sand
fly Swayambhu—Sitapaila area of
Kathmandu, Nepal.
Methodology:
The current study was carried on 17th
May 2013 at Swayambhu -Sitapaila
area of Kathmandu metropolitan city.
Different equipments for sampling of
mosquitoes and sandflies were
handled. The methodology employed
was direct handling and usage of
different equipments. These
investigations provide information on
vector species, their distribution,
density, bionomics and
susceptibility/resistance to
insecticides for vector control.
Results and Discussions:
Different tools and equipments used
in vectors collection were observed
and used.
The equipments used were aspirator,
BG sentinel trap, CDC light trap,
ovitrap and adult emergence trap.
1. Indoor hand collection:
Indoor hand collections were carried
out inside different shelters in human,

5. mixed and animal dwellings spending
15 minutes in each house by one
collector using aspirators and flash-
lights.
2. Outdoor hand collection
Outdoor collections was similarly
attempted outside the house from
outside walls, under leaves,
vegetation and bushes around cattle
sheds and piggeries, and in and
around outdoor stored materials
spending 30 minutes using aspirators
and flash-lights.
Mouth aspirator was used for
collecting indoor and mosquitoes. It
can also be used for collecting
sandflies. It consists of mouth piece
and rubber tubing. Rubber tubing was
placed near a resting mosquito and air
was sucked up from mouth piece.
This created a negative pressure
inside the rubber tube and the
mosquito was pulled in. Man hour
density of mosquitoes was calculated
using the formula for indoor hand
collected mosquitoes and sand flies:
Man-hour density=
(No. of mosquitoes collected/duration
in minutes)X 60 minutes
Calculation for outdoor hand
collected mosquitoes and sand flies:
Number of mosquitoes collected per
artificial shelter (No. of mosquitoes
collected/No. of artificial shelters
searched)
BG sentinel trap is designed
especially for Aedes spp1
. The
equipment was set up and connected
to electric source. The luring
substance in the equipment, octenol,
and carbondioxide attract mosquitoes.
Negative pressure created by rotating
fan inside the trap doesn't allow the
mosquitoes to escape. Basically,
Aedes mosquitoes are collected in the
trap. However, Culex spp are also
collected due to their abundant
number.
CDC (Centre for Disease Control)
Light trap is used for sampling
Anopheles as well as Culex
mosquitoes along with
sandfly(Phlebotomus argentipus),
causative agent of Leishmaniasis2, 3.
CDC light trap consists of light and
carbondioxide to attract mosquitoes. It
has a fan rotating inside the trap
which maintains a negative pressure
not letting trapped mosquitoes to
escape. It is run for 12 hours from 6
a.m. to 6 p.m.

6. Adult emergence trap was observed
and its usage was learned. It consists
of two compartments. The lower
compartment accomodates water
containing larval stages of
mosquitoes. The upper compartment
also known as collection cup holds
the mosquitoes that emerge from
larvae. It has been used to study Culex
mosquitoes in urban catch basins5
An ovitrap is a device which consists
of a black cylinder with a piece of
cardboard. This device is used to
control the Aedes mosquito
population and as well all other
mosquito populations. It can monitor,
control and detect Aedes mosquito
populations thus acting as an early
warning signal to preempt any
impending dengue outbreaks.6
The
black ovitrap attracts female
mosquitoes to lay their eggs. When
the eggs hatch and develop into
adults, they cannot fly out of the
device and die inside the trap. The
extensive use of the ovitrap in a
community can be used in Aedes
population control and effectively
reduce the Aedes population in that
area. It has been used in countries like
Singapore, United States and Hong
Kong since the 1970s.
Ovitrap index
= Number of positive ovitrap × 100
Total ovitraps placed
Conclusions:
Different equipments ranging from
simple to sophisticated equipments
for mosquito and sandfly sampling are
used. They help in studying
relationship between vector and
disease, planning and monitoring
control measures for vector.
References:
1. Ellis R, 2004, Municipal
Mosquito control
Guidelines, Health Canada, Centre for
Infectious Disease Prevention and
Control, pg.1-3
2. Maciel-de-Freitas R, Eiras AE,
Lourenço-de-Oliveira R, 2006 , ,
"Field evaluation of effectiveness of
the BG-Sentinel, a new trap for
capturing adult Aedes aegypti
(Diptera: Culicidae)", Journal of the
American Mosquito Control,
May;101(3):321-5, PMID: 16862330

7. 3. Zaim M, Ershadi MR,
Manouchehri AV, Hamdi MR, 1986, ,
" The use of CDC light traps and
other procedures for sampling malaria
vectors in southern Iran", Journal of
the American Mosquito Control,
Dec;2(4):511-5 PMID: 3507528
4. Dinesh DS, DAS P, Picado A,
Davies C, Speybroeck N, Boelaert M,
Coosemans M, 2008, "The efficacy of
indoor CDC light traps for collecting
the sandfly Phlebotomus argentipes,
vector of Leishmania donovani",
Medical and Veterinary Entomology,
Jun;22(2):120-3. doi: 10.1111/j.1365-
2915.2008.00724.x.,PMID: 18498610
5. Hamer GL, Kelly PH, Focks DA,
Goldberg TL, Walkers ED, 2011, , "
Evaluation of a novel emergence trap
to study Culex mosquitoes in urban
catch basins", Journal of the
American Mosquito Control,
Jun;27(2):142-7 PMID:21805846
6. Jakob WL, Bevier GA (1969).
"Application of ovitraps in the US
Aedes aegypti eradication program".
Mosq News 29: 55–62. ISSN 0027-
142X.
Advisor
------------------------------------
Dr. Ishan Gautam
Lecturer, Tribhuvan Universisty