BY
JACOB PHELIMON
AUGUST, 2010.
ABSTRACT
A study on susceptibility status of culicine to DDT
and Propoxur in three (3) Local Government Areas in Gombe State,Nigeria was
conducted over a period of three months (March —May 2010). A total of 750
culicine mosquitoes were collected and tested from the three (3) sites which
were Gombe, Yamaltu-Deba and Akko L.G.As Mosquitoes show 100% susceptibility
when exposed to Propoxur from all the three L.G.A. over a period of 1 hour and
after 24hours interval. No signs of resistance due to Propoxur were observed.
Exposure to DDT showed a strong indication of resistance of 57%, 34% and 22% in
Gombe, Yamaltu —Deba and Akko L.G.A. respectively.
Introduction
Background
of the Study
Little
is known on the susceptibility of mosquitoes in Gombe tate (sudan savanna) to
the spectrum of many and widely used insecticides in this area. The work of the
World Health Organization (WHO, 1975) in Kaduna, Kano and Sokoto states of
Nigeria has paved a way to this problem. It is known that a large number of
mosquitoes species which are less susceptible to DDT (Dichloro-diphenyltrichioroethane)
are being controlled by the use of chemicals and other new brand chemicals
(Molta et al., 1990).
With increase in the chemical pest
control activities in the savannas, there may be the tendency for insecticides
to develop resistance to the conventional product (Molta et al,1990). It is a
priority to determine and monitor the efficacy of these chemicals as well as
their effects on the ecosystem be monitored as part of the operation (Koeman, 1971).
Culicines are of interest to man as potential vectors of various pathogens such
as yellow fever, filariasis, encephalitis (Annon, 1992). These disease vectors
controlled by, using either insecticides treated nets (ITNs) or indoor residual
spraying(IRS), relies on the continued susceptibility of culicines mosquitoes
to a limited number of insecticides( WHO,2002).
Effective implementation of indoor
residual spraying with DDT or other recommended insecticides should be a
central part of the national malaria and other mosquito — borne disease control
strategies.
(
WHO, 2006 ). DDT is the only insecticide which is used exclusively for public
health, and unlike with other insecticides, development of resistance to it is
no longer influenced by other uses such as in agriculture (WHO, 2006).
DDT
has for long been the cheapest insecticides and the one with longest residual
efficacy against anopheles that transmit malaria ad other mosquito-borne
disease vector (6-12 month depending on dosage and substrate). Thus, the use of
alternatives to DDT might require 2 or 4 spraying cycle per year instead of one
depending on the length of transmission season (WHO, 2006). Other insecticides
have relatively shorter residual effect e.g. pyrethroid which requires 4-6
month; Organophosphate and carbamates: 2-6 month (WHO, 2006).
The insecticides such as Benzene
Hexachloride (HCH) was banned from the public health use in 1997 and DDT and
Malathon were introduced and recommended for public use(Gunasekaran, et al, 2005)
in India. The use of other insecticides for use is the propoxur, which was not
considered to be a mutagemc or embryogenic (WHO, 2003).
Culicine
mosquitoes are distributed world wide occurring in different altitudes and
geographical regions, they are found in elevations of 1,200metres below sea
level (Goma, 1961). They occur from tropical to temperate regions and even in
deserts.
Evolutionary wise, culicine have a
very ancient history, they are
believed to have appeared in the
world long before man, (Winterboun et al, 2000).
Culicine
mosquitoes have the following characteristics: they are small fragile insect
that have six delicate legs and two wings covered with scales, the head of
which is equipped with a projecting proboscis which conceals and protects the
long piercing and sucking mouth parts. The biting culicines mosquito have a
complex life cycle, the immature stages are totally aquatic and the adults
terrestrial. The adult female returns to water habitat for a brief period to
lay eggs (Wigglesworth, 1979).
Breeding
ground for culicine mosquitoes include extensive mining and mineral prospecting
activities which enhance the activities of culicines mosquitoes, and natural
pots often employed in fermentation concotions called “ruwan magani” (Molta et
al,1990) serves as major habitats for culicine mosquitoes breeding activity
most especially Culex quinquefasciatus, (Greg and Moses, 1999).
Motor
tyres abandoned at some obscure location in the premises or sometimes used by
natives as wind checks on roof tops or to rim off. Poorly constructed compound
wells rather become ideal and quiet breeding grounds for mosquito species like
Aedes aegyti and Cx. quinqufasciatus (Greg and Moses, 1999). “Rijiya” or
compound wells to habour tremendous numbers of immature mosquitoes especially
during the dry season months when most other units lack water.
Justification
for Study
The
reason for the study of the susceptibility status of culicine mosquitoes is
because of the high modification of structure by mosquitoes and insecticides
nowadays have litter or no effect on mosquitoes, only few have effect on them.
Scope
of the Study
The
scope of this study is limited to the collection of culicine mosquito larva in
three L.G.As, reared to adult stage and determines their susceptibility status
with exposure to DDT and Propoxur. 1.4Aim of the Study
The
aim of the study is to determine the susceptibility status of culicine
mosquitoes to DDT and Propoxur. It is hoped that knowledge obtained will be of
importance in indoor residual spraying (IRS).
Materials
and Method
The
Study Area
The
study was carried out in Akko, Yamaltu-Deba and Gombe Local Government Areas.
Gombe state lies between latitude 11 °8 ‘N and 11°24”, longitude 11°2’ and
11°18’E. It has a population of about 2.1 million people and an area of about
18,000km2. The temperature average 30°C with an annual rainfall of 52cm. The
predominat occupation of its people is Agriculture and livestock rearing.
Materials/Equipments
Materials that were used in this
study include:
Susceptibility
kits (including exposure tube or holding tubes, silver rings, insecticides
impregnated papers, control papers), ladle, hatchery, mosquito cage, markers,
watch clock, aspirator, glucose, yeast.
Preliminary
Investigation
A
preliminary survey was carried out within the study areas, aimed at identifying
the breeding areas of mosquitoes. This provides information on areas in which
the larvae of culicine mosquitoes are found.
Method
of Collection
Culicine
larvae were collected from two sites in each of the three(3) L.GA in Gombe
state within the months of March20 10- May2010.
A
laddle was used to collect different larval instar. About 7-10 scoops were
collected depending on the concentration of the larvae in the water. In order
to get enough quantity for rearing. All collected larvae were brought to the
insect laboratory which was then reared to adult stage.
About
100 female culicine were used for the susceptibility test from each of the
L.G.A.
Insecticide
Susceptibility Test
Insecticide
susceptibility test was carried out using the standard WHO protocol (WHO,
2008), insecticides susceptibility test kits and impregnated papers were used.
The mosquitoes were transferred from the hatchery to the cage with the use of
an aspirator. The males were selected from the females and only the females
were used for the susceptibility test.
1-2
day old non-blood fed adult female culicine were tested in batches of 25
mosquitoes per tube. These were exposed to the holding tubes for 1hour and
later transferred to the testing tubes with DDT-5 % and propoxur-l% the
required dosage. With control in each case were exposed to untreated papers.
Knock-down mortality was recorded at 5, 10, 20, 30, 40, 50, 60minutes and
24hours interval.
Results
A
total number of 750 female culicine mosquitoes were exposed to impregnated
insecticides treated papers with propoxur and DDT while the control were
exposed to non treated papers.
Table
1: Culicine mosquitoes from Gombe L.G.A.
exposed to propoxur and percentage knock down.
|
Time (min)
|
Control (%)
|
Knock down (%)
|
|
5
|
0.0
|
0
|
|
10
|
0.0
|
3
|
|
20
|
0.0
|
22
|
|
30
|
0.0
|
45
|
|
40
|
0.0
|
58
|
|
50
|
1.0
|
82
|
|
60
|
1.0
|
100
|
|
24 hours
|
1.0
|
100
|
From table 1, knock down percentage
of mosquitoes with 100% susceptibility at 60mins and 24hours interval.
Table 2: Culicine mosquitoes from
Yamaltu-Deva exposed to propoxur and percentage knock down.
|
Time (min)
|
Control (%)
|
Knock down (%)
|
|
5
|
0.0
|
0
|
|
10
|
0.0
|
0
|
|
20
|
0.0
|
10
|
|
30
|
0.0
|
45
|
|
40
|
0.0
|
64
|
|
50
|
0.0
|
87
|
|
60
|
0.0
|
100
|
|
24 hours
|
0.0
|
100
|
Table 2 shows culicine mosquitoes
with knock down of 100% susceptibility at 60mins and 24hours interval.
Table
3: Culicine mosquitoes from Akko L.G.A. exposed to propoxur and percentage
knock down.
|
Time (min)
|
Control (%)
|
Knock down (%)
|
|
5
|
0.0
|
0
|
|
10
|
0.0
|
4
|
|
20
|
0.0
|
8
|
|
30
|
0.0
|
21
|
|
40
|
0.0
|
37
|
|
50
|
0.0
|
61
|
|
60
|
0.0
|
100
|
|
24 hours
|
0.0
|
100
|
Table 3 also shows a high knock
down mortality of 100% at 60mins and 24 hours intervals.
Table
4: Culicine mosquitoes from Gombe L.G.A. exposed to DDT and percentage knock
down.
|
Time (min)
|
Control (%)
|
Knock down (%)
|
|
5
|
0.0
|
0
|
|
10
|
0.0
|
0
|
|
20
|
0.0
|
2
|
|
30
|
0.0
|
11
|
|
40
|
0.0
|
19
|
|
50
|
0.0
|
25
|
|
60
|
1.0
|
54
|
|
24 hours
|
1.0
|
57
|
The
table shows a difference in the knock down rate of mosquitoes compared to other
L.G.A. exposed to propoxur. There is a knock down of 57% at 60 mins and 24hours
interval. And not all mosquitoes died at the end of 24 hours, they show
resistance to the insecticides.
Table
5: Culicine mosquitoes from Yamatu-Deba exposed to DDT and percentage knock
down.
|
Time (min)
|
Control (%)
|
Knock down (%)
|
|
5
|
0.0
|
0
|
|
10
|
0.0
|
0
|
|
20
|
0.0
|
2
|
|
30
|
0.0
|
4
|
|
40
|
0.0
|
9
|
|
50
|
0.0
|
14
|
|
60
|
0.0
|
34
|
|
24 hours
|
0.0
|
34
|
From
table 5, resistance in mosquitoes tend to be increasing with a knock down of
34% at 60mins and 24 hours intervals. This shows at high resistance status in
the mosquitoes.
Table
6: Culicine mosquitoes form Akko L.G.A exposed to DDT and percentage knock
down.
|
Time (min)
|
Control (%)
|
Knock down (%)
|
|
5
|
0.0
|
0
|
|
10
|
0.0
|
0
|
|
20
|
0.0
|
2
|
|
30
|
0.0
|
2
|
|
40
|
0.0
|
5
|
|
50
|
0.0
|
11
|
|
60
|
0.0
|
22
|
|
24 hours
|
0.0
|
22
|
Table 6 shows a
knock down rate of 22% at 60mins and 24 hours intervals also shows that there
is a resistance status in these mosquitoes due to slow percentage knocks down.
Discussion
This
study has shown high knock down mortality rate of culicine mosquitoes exposed
to propoxur was found in all the L.GAs with 100% at 60 mins and at 24hours
intervals knock down, and this agree with the work of the World Health
Organization (WHO, 2003) which reported a susceptibility to propoxur
insecticides in Gambia. According to (WHO, 2001) recommendations. 98-100%
mosquito mortality indicate susceptibility, 80-97% suggest potential resistance
that needs to be confirmed, and <80% mortality suggest resistance.
A
very slow knock down mortality of culicine mosquitoes exposed to DDT
impregnated papers from all the L.G.As were recorded. This ranges from 5 7-22%
(Gombe with 57%, Yamaltu-deba 34% and Akko 22%). This agrees with the reported
resistance of culicine mosquitoes to DDT in Gambia (Betson et al, 2009).
Generally,
the results of this study provide evidence of susceptibility to propoxur in
culicine mosquitoes from Gombe, Yamalyu-Deba and Akko L.GA. resistance
indicated in the three(3) L.G.As due to DDT. Resistance shown here may be as a
result of continued use of chemicals in farmlands such as herbicides,
fungicides, germicides and insecticides. These chemicals tend to remain in the
soil/environment for months to several years and these mosquitoes become
resistance to other resistance like in the case of DDT. There is a need for
continued surveillance to find out the resistance factors present in these
mosquito species.
Conclusion
This
study reveals a resistance status or culicine to DDT based on the
susceptibility test on culicine mosquitoes, and completes susceptibility to
propoxur. The data provides a base line information on resistance level in
culicines before the Gombe State Health Authority embarks on an indoor residual
spraying campaign using DDT.
Recommendation
1. Continued
research should be carried out to find out the resistance factors present in
these species of mosquitoes.
2. Indoor
Residual Spraying should be effectively improved in the state with the use of
Propoxur and other effective insecticides.
3. Breeding
sites of mosquitoes should be destroyed as this will reduce the rate of
infection of diseases caused by culicine mosquitoes.
REFERENCES
Annon
C.W (1992): Diseases of mosquito vector species of the tropics. Bulleting of
Entomology society of New Zealand. 10:20-30.
Betson.
M, Musa. J. Taiwo .S (2009): Status of insecticides susceptibility in Anopheles
gambiae S.I from malaria surveillance sites in Gambia. Malaria Journal.
96:849-860
Colless
and Mc Alphine (1970): Aquatic insect orders. New Zealand bulletin Of
Entomology society. 13.65-68.
Curtis
C.F and Muzava A.E.P (2000): Comparison of house spraying and Insecticides
treated nets for malaria control. Bulleting for World Health Organization. 78:
455-460
Greg
LA. and Moses O.E. (1991): Mosquito breeding sites: distribution and Relative
abundance of species in Jos Plateau,
Nigeria Medical entomology Zoology. 50: 2 14-219
Goma
L.K.H (1966a): The mosquito. Published by Hutchinson tropical Monographs,
Hutchinson and Co. ltd. 38: 176-202
Gordon,
(1978): Entomology for students of medicine. Published by block Well scientific
publication London.
Gunasekaran
, M. Ludo, k. Felicia, C. (2005): Use of insecticides for public Health.
Journal of entomology. 43: 2-4
Hargreaves,
K. Koekmoer, L.L. Brook, B.D. Hunt, R.H. Mthembu, J. Cotzee M. (2000): Anopheles
funestus resistance to pyrethroid in South Africa Medical veterinary
entomology. 14: 18 1-189.
Kelly-
Hope, L. Ransom, H. Hemingway, J. (2008): Managing insecticides Resistance
malaria control and eradication programme. Malaria Journal. 8: 3 87-389
Longnecker,
V. (1999): Effective and proper management in the use of Insecticides. Medical entomology. 16: 3-8.
Molta,
N.B. Gadzama, N.M. Standsfield, F. (1990): The susceptibility of a Mosquito
species (Culex pipiens quinquefasciatus)
to the insecticides, Malathion, DDT, and DBMT in the sudan savanna zone of
Nigeria. Nigerian Journal of Entomology.11: 43-52
Nagera,
J.A. and Zaim, M. (2002): Decision making criteria and procedures For the
judicious use of insecticides. Medical parasitology. 21: 21-24
Romi,
R Razaiarimanya, M.C. Rahari, M.R. Rokotontraibe, E.M. Ranaivo, L.H. Pietra, V.
Raveloson, A. Majori, G (2001): impact of malaria Control campaign in the
highlands of madagascar. Parasitology and
Entomology data, Journal of tropical medical hygiene. 66: 2-6.
Suarez, M.F. Quinones, Mi. Palacious,
J.D. Carrilo, A.(1990): first record To DDT resistance in Anopheles darling) .j. Am. mosq. Association. 6: 72-74.
Service,
M.W. (1963): The ecology of mosquitoes of Guinea savanna of Nigeria. Bulletin of entomology resource. 56:
601-632. U.S EPA. (199Th): Effective use propoxur. Medical entomology society.
50:8-11.
Winterbourn,
M.J. Gregson, K.L.D. Dolphin, C.H.(2000): Guide to aquatic Insect of new
Zealand. Bulleting of entomology society of New Zealand. 76: 67-89.
World
Health Organization,(1973): Use of propoxur in pest control. WHO Technical report series. Geneva.
World
Health Organization, (2003): save use of pesticides. WHO technical Report series. Geneva.
World
Health Organization, (2006): Use of indoor residual spraying for Scaling up
global malaria control and Elimination. Geneva.
World
Health Organization (2002): Test procedures for insecticides Resistance
monitoring in malaria vectors .Bio-efficacy and persistence of insecticides on
treated surfaces. WHO. 98: 20-31.
World
Health Organization (1998: Test procedures for insecticides Resistance
monitoring in malaria vectors 98:12-16.
Related Articles:
