BY
MUSTAPHA
IDRIS
AUGUST,
2009
ABSTRACT
A survey of mosquitoes was conducted within Gombe
State University for a period of three months from March to May on weekly
bases. Three areas were used as sampling sites to determine the presence of
mosquito species; they are students’ hostel, class rooms and bathrooms/toilets.
Out of the 312 mosquitoes collected Four species were recorded: Culex nigripalpis 157 (50.3%), Culex uniformis 74 (23.1%), Anopheles gambiae complex 44 (14.1%) and
Anopheles funestus 37 (11.8%). Males
were more recorded 166 (53.2%) than the females and 146 (46.7%).More mosquitoes
were collected from the Bathroom/toilets 157 (50.3%), than Bedrooms 110 (35.2%)
and classrooms 44 (14.1%), chi-square (X2) shows that there was no
significant difference between, Sexes and the sampling areas.
Introduction
Mosquitoes
are small flying, blood sucking insects. There are about 3100 species of
mosquitoes belonging to 34 genera arranged in 3-subfamilies; Toxorynchitinae,
Anphelinae and Culicinae. The most important man biting mosquitoes belongs to
the genera, Anopheles, Culex, Mansoni, Aedes, Psorphora, Haemagogus and
Sabethes. The last two genera are found in central and south America,
(Service, 1976).
Mosquitoes
are of interest to man as potential vectors of various pathogens. Such as
yellow fever, Filariasis, Encephalities and malaria (Annon 1.1992) Malaria is
known to be the most prevalent and devastating disease of mankind in the
tropics. It is endemic in 91 countries with 41% of the world population at risk
(WHO 1 984a), furthermore, malaria is one of the world most widespread and
severe disease, and it has plagued mankind since prehistoric time (WHO 1984b).
Malaria was reported to kill one human being in every 12 seconds (McGraw,
2000).
Mosquitoes
have the following characteristics, they are small fragile insects that have
six delicate legs and two wings covered which are scales, the head of mosquito
is equipped with a projecting proboscis which conceals and protects the long
piercing and sucking mouth parts. These biting insects have a complex life
cycle, the immature stage is totally aquatic and the adult is terrestrial. The
adult female returns to a water habitat for a brief period to lay eggs. Each
batch of mosquito species varies in their breading habit biting behaviour, host
preference and flight range (Wigglesworth, 1976).
On
average, a female mosquito will live 2-3 weeks but the males life span is
shorter, within their life time adult male and female will feed on nectar and
plant fluids, but it is the female that will seek a blood meal, majority of
species require this blood meal as a protein source for egg development, female
mosquitoes are attracted to a potential host through the combination of the
different stimuli that emanate from the host. The stimuli can include carbon
dioxide, body odours, air movement or heat for locating a suitable host.
Like
all Diptera, mosquito has a complete metamorphosis, having fours distinct
stages in their life cycle and hence is said to belong to the group of insects
that are referred to as Holometablolous i.e. (young one’s are very different
from their parents, in structure and habit).
Mosquitoes
are world wide in distribution occurring in different altitudes and
geographical regions, they are found in elevation of 5,500 meters in height and
depth of 1,200 meters below sea level (Goma, 1966a), they occur in tropical to
temperate regions and even in deserts.
The geographical distribution of
many types of mosquitoes closely conforms to the six zoo geographical regions
of the earth, these major zoogeographical region are Palaeactic, Ethiopian,
oriental, Nearctic, Neotropical and Australian regions, (Sevice 1963 a).
Evolutionary
wise, mosquitoes have a very ancient history. They are believed to have
appeared in the world long before man Winterboun, et al (2000).
Today
it leaves no place to doubt that mosquitoes have attained their place in the
world by evolving highly specialized anatomical structures with the
corresponding specialized habits, mosquitoes are good vectors of some human and
animal diseases. The species differ in the diseases they act as vectors.
Control
strategies can not be effective unless the species are known. The insects will
therefore multiply rapidly, owing to lack of attempts to control their
population, this implies that the diseases they act as vectors, such as
Malaria, filariasis, yellow fever and etc. will be so rampant in the school
compound, if they are not controlled. Their bites cause itching, swellings,
rashes and even sometimes nervous irritations in man.
Scope
of the Study
The
scope of this study is limited to the survey of mosquitoes within Gombe State
University Campus, and the survey areas are, student’s hostels.
Significance
of the Study
The
significance of this research is to make us have a greater and better knowledge
of the mosquitoes that are prevalent within the school campus, and to know more
about their biology.
This
knowledge will enable us have a better chance of controlling them and the
diseases they act as vector more effectively, since the world is committed
towards rolling back malaria and other parasitic diseases.
Aims
and Objectives
1.
To determine the species of mosquitoes within the school campus
2. To
evaluate the distribution of mosquitoes species in three sampling areas
3. To
determine the population of the sexes of mosquitoes in these areas.
Materials
and Methods
The
Study Area
The
survey was carried out in Gombe State University Campus which is located in
Tudun Wada Ward of Gombe, the area is located between latitude N 10° 18’ 19.8”
and longitude B 110 10’ 36.111 of the northern part of Gombe metropolis. There
are two main seasons in Gombe; the cold wet season lasting from May to October
with a heavy rainfall and dry season from November to April.
The humidity is low
more especially in the dry season, the temperature varies throughout the day.
High in the afternoon but drops completely in the night, the hottest months in
the area are February, March and April with a temperature of about 32°C-38 °C.
Preliminary
Investigation
A
preliminary survey was carried out within the survey area, aimed at identifying
the breeding/hiding areas of the mosquitoes.
The
preliminary investigation provides information on which time of the day the
mosquitoes were most abundant and thus the time for which the maximum catches
should be made.
Time
of Collection
Resting
mosquitoes were collected, collection was done once
in a week between the hours of
8:30-1 1:30am with an interval of
one hour to each station.
Method
of Collection
Adult
mosquitoes were collected for three months from March 2009-May 2009 from three
sites within the school campus, and the sampling was carried out in the morning
hour based on the preliminary survey earlier conducted in their hiding place as
they are inactive at that time for easy collection.
The
method employed was by hand catching using a specimen bottle which was soaked
in ethyl acetate, and by dipping and netting method as per (WHO, 1975b)
guidelines. Used of mosquito nets for the distance one’s.
Mosquitoes
were identified up to their genera level based on their resting position,
Anophelines rest at an angle to the surface while Culicines abdomen parallel to
their resting surface.
The
mosquito covered with specimen bottle which contained soaked ethyl acetate by
aspiration. It is was then collected dead and place in a labeled container for
identification. Keys used for identification are those of (Gillet 1971).
Methods
of Identification
After
a days collection was done, it was taken into the lab for final identification
to the species with the help of stereomicroscope and a taxonomic key by
Gillete.
The
Result
The
total number of mosquitoes caught during the period of sampling was three
hundred and twelve (312) table 1. The total number of males was greater than
that of females throughout the period of sampling. The total number of males
caught during this period of survey was one hundred and sixty six (166)
(53.2%), while that of the female was one hundred and forty six (146) (46.7%)
table 1.
The
average caught per month was one hundred and four (104). The highest catch was
in May with a population of one hundred and thirty eight (138) (44.2%), and the
least catch was in April with a population of eighty five (85) (27.2%).
Appendix 14, 15 and 16.
The
mosquitoes caught during the sampling period belongs to two genera namely
Culicinae and Anopheline, the species caught were those belongs to the
following. Culex nigripalpis, culex uniformis, Anopheles gambiae complex and
Anopheles funestus, table 1.
The number and their percentage are
as follows, Culex nigripalpis 157 (50.3%), Culex uniformis has a population of
74 (33.7%), Anopheles gambiae complex has 44 (14.1%) finally Anophelesfunestus
which is 37 representing (11.8%).
The
highest number of Culicinaes occur in May with a population of 66 (21.1%) and
the least occur in March with a population of 19 (6.0%) the highest number of
Anopheles occurs in May with a population of 20 (6.4%) and least population is
in April it has a population of 8 (2.5%) fig. 1-7.
The
highest collection in the sampling area was bathroom toilet with a population
of one hundred and fifty seven 157 (50.3%) followed by student hostel with a
population of 110 (35.2%), lastly the class rooms which has a population of 45
(14.4%) as shown in fig8.
The
species of Culex cough were only two namely culex nigripalpis, Culex uniform
is, and that of Anopheles area also two species which are anopheles gambiae
complex and Anopheles funestus which occur throughout the period of survey.
Table 1: Summary of
mosquitoes collection
|
S/NO.
|
SPECIES
NAMES
|
M
|
F
|
TOTAL
|
|
1.
|
Culex
nigripalpis
|
85
|
72
|
157
|
|
2.
|
Culex
uniformis
|
44
|
30
|
74
|
|
3.
|
Anopheles
gambiae complex
|
21
|
23
|
44
|
|
4.
|
Anopheles
funestus
|
16
|
21
|
37
|
|
|
TOTAL
|
166
|
146
|
312
|
Table
2: Percentage of mosquitoes species
collection
|
S/NO.
|
SPECIES
NAMES
|
M
|
%
|
F
|
%
|
TOTAL
|
%
|
|
1.
|
Culex
nigripalpis
|
85
|
51.2
|
72
|
49.3
|
157
|
50.3
|
|
2.
|
Culex
uniformis
|
44
|
26.5
|
30
|
20.5
|
74
|
23.7
|
|
3.
|
Anopheles
gambiae complex
|
21
|
12.6
|
23
|
15.7
|
44
|
14.1
|
|
4.
|
Anopheles
funestus
|
16
|
9.6
|
21
|
14.3
|
37
|
11.8
|
|
|
TOTAL
|
166
|
99.9
|
146
|
99.8
|
312
|
99.9%
|
Fig
1. Mosquito occurrence for the month of March
Discussion
Out of the four
species of mosquitoes caught, Culex
nigripalpis were the most abundance occurring through out the period of
survey with a percentage of (50.3%) and the least population is Anopheles funestus with a percentage of
11.8%. The breeding space for the Culex
mosquitoes are around pools in all the three areas of survey, this implies that
Anopheles species breed in a clear or less polluted water bodies, (Jarafu
1981), had reported a similar result with Anopheles forming 0.23% of the total catches
made. (Service 1963a) reported that the population of Culex sp. increased with high rainfall and decline subsequently in
dry season.
Christopher
(1960) reported that eggs of mosquitoes undergo some increase in size before
they become matured and the development of egg was directly under the influence
of temperature or it may development directly without influence of temperature
but it remain at diapauses until some stimuli receptivity the larvae to lead to
hatching.
The reason why
bathroom / toilet has the highest collection was that the place was dark and
cool and contained more moisture than the other two places which served as a
good resting place for mosquitoes.
Table 2 shows
the number of males to out numbered the population of the female because the
female supplement their diet by piecing the skin of vertebrates and taking
their blood meals and since the class rooms are shut in the night time when
mosquitoes are active, they cannot get their blood meal but rather they can
feed on the nectar of flower which is more abundant in the class room area.
Culex
nigripalpis recorded the highest in the month
of May because at that time we have started experiencing rainfall which
correlate positively with their breeding season, and the month of April
recorded the least species of Anopheles
funestus which may be related to lack of rainfall at that time, generally
mosquitoes population is known to decrease in the dry season due to unfavourable
condition such as law humidity, temperature lack of breeding place (Service,
1963)
The low
incidence in occurrence has been explained by Gadzama (1976) as a result of
eruption of springs after persistent rains Anopheles
funestus though is an important malaria vector it’s role in a particular
locality depends on the presence of Anopheles gambiae complex.
The species of
Anopheles caught were only two namely Anopheles
gambiae complex, Anopheles funestus
which occurred throughout the period of survey, these species of Anopheles are
said to be the commonest species of the genus in Nigeria (Service 1963b).
The distribution
of adult mosquitoes was said to be dependent on their behavior prevailing
climatic condition of the area and the availability of breeding habitats and
food.
Christopher
(1960) observed that high humidity favors the development of mosquitoes and it
could be up to saturation of 80% relative humidity at 28°C they are active at high
humidity provided temperature is about 25 °C.
The number of
the Anopheles was not high and they occurred only after the first rain, similar
observation was made by Gadzama (1976).
Mosquitoes are
also found to be present in areas not of their breeding sites especially in
winter days for instance (Service 1963), found that Anopheles funestus flies a distance of 4.5km in the direction of
wind with the wind velocity of 9.5km per hour generally mosquitoes population
was known to decrease in the dry season due to unfavorable condition such as
low humidity, temperature lack of breeding place.
Feeding habit of
Anopheles gambiae was said to be
variable, but principally indoors (Anon 3, 1999), and it is active after mid
night. It can fly to a distance of up to 3.2 km per day in the wind direction,
this species is widely spread in Africa and it is an efficient vector of the
killer disease, malaria. Its larvae occur in temporary habitats such as pools,
puddles, foot prints and breeds in sunlight pools.
Both Anopheles gambiae and Anopheles funestus is the most frequent
house hunting Anopheles sp. and described as anthrophilic.
In this survey
members of culicine group were representative of only one genera, Culex made up of Culex nigripalpis 50.3%, Culex
culiformis 23.7% respectively Gadzama (1976), found that the distribution
of Culex .in Samaru ,Zaria has a peak in November and December and is seasonal.
This genera is the only truly cosmopolitan one possibly because of it’s
occurrence in sewage effluent adults and larvae of Culex quinquefasciatus occur in high number in the polluted Samaru
stream. This species is a very good vector of bancroftian filariasis of which Wuchereria bancrofti is the causative
agent. The species being domestic in habit feeds on man inside and outside
houses in the night.
The
lowest occurrence was recorded in the lecture rooms and labs and this might be
as a result of constant disturbance by people during the day time, and the
place is not dark therefore not comfortable for stay
Conclusion
/ Recommendation
The
occurrences of four species of mosquitoes in these areas pose a danger to
infection with both malaria and filarial diseases. Hence control measures need
to be taken which should include
1. Elimination
of breeding site: - this can be done by increasing water flow and simple
ditching to provide proper drainage and disposal of empty containers.
2. By
using insecticides: - to eliminate ‘the adult mosquitoes population.
3. Use
of oil: - powering of oil on the surface of stagnant water help to kill the
larvae.
4. Clearing
the surrounding area to make it free of grasses which harbor the adult
mosquitoes.
References
Anonymous
(1992): The World Book
Encycolopedia, Vol 13 World Book, Inc
Anonymous
(1999) Mosquitoes have
discriminating tastes
Environmental
news Network . CNN. corn
Boris
R. (1974): The Historical
development of Diptera University of Alberto Press pp5 1-53.
Braks M.A.H, Anderson R.A and knols
B.G.J (1999). “Info chemicals in mosquitoes, host selection
human skin
microflora and plasmodium parasites” Parasitology Today Vol 15N.1O.
Christopher
S. R. (1960) Aedes aegvpti (L.)
The yellow fever mosquito:
Its life
history, bionomies and structures, the
syndics of
the Cambridge University press.
Gadzama, N. M. (1960. The distribution of populations of
adult mosquitoes at Ahmadu Bello University, Zaria.
Research publication, department of biological Sciences, Ahmadu
Bello University, Zaria.
Godzama
.N.M. (1976): The Distribution of
Population of Adult Mosquitoes at ABU
Zaria Research Publication,
Dept of
Biological Sciences, ABU Zaria
Gillett.
J. D. (1971). Mosquitoes.
Gillett
T.D (1972): Common
African Mosquitoes and their medical importance.
Heinemann Medical Book ltd, London
pp 106.
Goma,
L.K.H (1966a). The mosquito. Hutchinson
tropical monographs.
Hutchinson
& co (publishers) Ltd. 176-202 great
Portland street, London Wi.
Goma,
L.K.H (1966b): The Mosquitoes
Hutchurison Tropical Monographs
Hutchurison
Gordon,
B.M Lavoipierre, M.M. (1978): Entomology
for students of medicine B lockwell
Scienctific Publication London pp 83-119
Hopkins,
H.A. (1952): “Aquatic Fauna and
Limological Studies of Fresh
Water”
University of California. Press pp
Horsfall,
W. R. (1972). Mosquitoes. Their bionomic
in relation to disease. Hefner Publishing Company
(Ltd). New York. Pp 1-73.
Jarafu,
U.M. (1981): Dry Season Population of
adult mosquitoes on Ahmadu Bello University Main Campus
and Samaru
village. Unpublished B.Sc Thesis, Development
of Biological Sciences, ABU Zaria. Pp
1-49
KEAY, R. W. J. (1953). An outline of Nigerian vegetation,
Government printer,
Nigeria, pp 55.
Mattingly, P.F. (1969): The biology of mosquito borne diseases George
Allen and
Union ltd. l84.pp
MC Graw G.C. (2000) Insects Spiders and other terrestrial
arthropods
Darling
Kindersley ltd, London pp 256.
Service M. W. (1963). The ecology of mosquitoes of Guinea Savanna
of Nigeria. Bull. Fnt. Res.
56:601-632.
W.H.O (1984a): Venture for Waith UNDP/World Bank/WHO Special Programe for Research and Training in Tropical Diseases World Health
Organization 1211 Geneva 27 Switzerland.
W.H.O (1972 — 75) Offset Publication No 13 World Health Organisation
WHO (1985): Biological control of vectors in tropical Diseases Research (TDR) 7th programme Report
(January 1983— 31
December 1984)
Wigglesworth, V.B. (1976): The Principle of insect physiology London Chapmann and Hall pg. 652.
Winterboom, M.J and Gregson, K.L.D. and
Dolphin, C.H (2000), Guide to aquatic insects of New Zealand Bulletin
of the Entomologic
of Society of New Zealand 13:65—68.
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