Overview of study A vector is an organism that does not cause disease itself but spreads infection by conveying pathogens from one host to another. Some Species of mosquito, for example, serve as vectors for the deadly disease such as Malaria (Wilson et al, 2017). Disease is any harmful deviation from the normal structural or functional state of an organism, generally associated with certain signs and symptoms and differing in nature from physical injury. A diseased organism commonly exhibits signs or symptoms indicative of its abnormal state. Mosquitoes are common, flying insects that live in most parts of the world. Over 3,500 types of mosquitoes can be found worldwide (Hardstone et al, 2012).Not all mosquitoes bite people or animals. When mosquitoes bite people, the most common reactions to the bite are itching and swelling. Some mosquitoes can be vectors. The germs (viruses and parasites) that mosquitoes spread can make people sick. Some mosquitoes bite, but do not spread germs. These types of mosquitoes are called nuisance mosquitoes (Becker et al, 2010).

1. MOSQUITO VECTOR BEHAVIOUR; IMPLICATIONS FOR
TRANAMISSION
BEING A SEMINAR PAPER SUBMITTED TO THE DEPARTMENT OF
ZOOLOGY
PRESENTED BY:
TACHIN FAITH
MATRIC NO: 17/44174/UE
DEPARTMENT OF ZOOLGY
JOSEPH SARWUAN TARKA UNIVERSITY MAKURDI,
IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE
AWARD OF BACHELOR OF SCIENCE (B.SC) DEGREE IN ZOOLOGY

2. SUMMARY
Overview of study
 A vector is an organism that does not cause disease itself but spreads infection by conveying pathogens from one host to
another. Some Species of mosquito, for example, serve as vectors for the deadly disease such as Malaria (Wilson et al, 2017).
 Disease is any harmful deviation from the normal structural or functional state of an organism, generally associated with certain
signs and symptoms and differing in nature from physical injury.
 A diseased organism commonly exhibits signs or symptoms indicative of its abnormal state. Mosquitoes are common, flying
insects that live in most parts of the world. Over 3,500 types of mosquitoes can be found worldwide (Hardstone et al, 2012).Not
all mosquitoes bite people or animals.
 When mosquitoes bite people, the most common reactions to the bite are itching and swelling. Some mosquitoes can be vectors.
The germs (viruses and parasites) that mosquitoes spread can make people sick. Some mosquitoes bite, but do not spread germs.
These types of mosquitoes are called nuisance mosquitoes (Becker et al, 2010).

3. Facts about Mosquitoes
Adult mosquitoes live indoors and outdoors.
Mosquitoes can bite day and night.
Mosquitoes live for about 2 to 4 weeks depending on the species, humidity, temperature, and other
factors. Female mosquitoes often live longer than male mosquitoes.
Only female mosquitoes bite people and animals to get a blood meal. Female mosquitoes need a blood
meal to produce eggs.
Mosquitoes get infected with germs, such as viruses and parasites, when they bite infected people and
animals.
It takes just a few infected mosquitoes to start an outbreak in a community and put you and your family
at risk of becoming sick.

4. Morphology
As true flies, mosquitoes have one pair of wings, with distinct scales on the surface. Their
wings are long and narrow, as are their long, thin legs. They have slender and dainty bodies
of length typically 3–6 mm, with dark grey to black coloring. Some species harbor specific
morphological patterns. When at rest they tend to hold their first pair of legs outward. They
are similar in appearance to midges (Chironomidae)
Habitats
Some mosquitoes like living near people, while others prefer forests, marshes, or tall
grasses. All mosquitoes like water because mosquito larvae and pupae live in the water
with little or no flow. Different types of water attract different types of mosquitoes.
Permanent water mosquitoes: These mosquitoes tend to lay their eggs in permanent-to-
semi-permanent bodies of water (Knight et al, 2003).
Some mosquitoes prefer clean water, while others like nutrient-rich waters. Some
mosquitoes lay eggs near the edges of lakes and ponds, or among plants in swamps and
marshes, or in containers that hold water (Knight et al, 2003).

5. Habitats COUNT’D
Floodwater mosquitoes: These mosquitoes lay their eggs in moist soil or in containers above the water line. The eggs
dry out, then hatch when rain floods the soil or container. Floodwater habitats include:
Temporary pools and ponds created by melting snow or rain
Floodplains along stream and river banks
irrigated fields and meadows
Containers that hold water and fill up after a rain shower and tree holes that collect rainwater
Breeding
In most species, adult females lay their eggs in stagnant water: some lay near the water's edge while others attach their
eggs to aquatic plants. Each species selects the situation of the water into which it lays its eggs and does so according
to its own ecological adaptations. Some breed in lakes, some in temporary puddles. Some breed in marshes, some in
salt-marshes. Among those that breed in salt water, some are equally at home in fresh and salt water up to about one-
third the concentration of seawater, whereas others must acclimatize themselves to the salinity (Day 2015). Such
differences are important because certain ecological preferences keep mosquitoes away from most humans, whereas
other preferences bring them right into houses at night. Some species of mosquitoes prefer to breed in phytotelmata
(natural reservoirs on plants), such as rainwater accumulated in holes in tree trunks, or in the leaf-axils of bromeliads
(Ahmed, 2013).

6. Anatomy of an adult mosquito
The period of development from egg to adult varies among species and is strongly
influenced by ambient temperature. Some species of mosquitoes can develop from
egg to adult in as few as five days, but a more typical period of development in
tropical conditions would be some 40 days or more for most species. The variation
of the body size in adult mosquitoes depends on the density of the larval population
and food supply within the breeding water (Brittain, 1990).
Adult mosquitoes usually mate within a few days after emerging from the pupal
stage. In most species, the males form large swarms, usually around dusk, and the
females fly into the swarms to mate. Males typically live for about 5–7 days, feeding
on nectar and other sources of sugar. After obtaining a full blood meal, the female
will rest for a few days while the blood is digested and eggs are developed. This
process depends on the temperature, but usually takes two to three days in tropical
conditions. Once the eggs are fully developed, the female lays them and resumes
host-seeking (Brittain, 1990).

7. INTRODUCTION CONT’D
Feeding by adults
Typically, both male and female mosquitoes feed on nectar, aphid honeydew, and
plant juices, but in many species the mouthparts of the females are adapted for
piercing the skin of animal hosts and sucking their blood as ectoparasites. In
many species, the female needs to obtain nutrients from a blood meal before it
can produce eggs, whereas in many other species, obtaining nutrients from a
blood meal enables the mosquito to lay more eggs. A mosquito has a variety of
ways of finding nectar or its prey, including chemical, visual, and heat sensors
(Krenn, 2019). Both plant materials and blood are useful sources of energy in the
form of sugars, and blood also supplies more concentrated nutrients, such as
lipids, but the most important function of blood meals is to obtain proteins as
materials for egg production.

8. Mouthparts
Mosquito mouthparts are very specialized, particularly those of the females,
which in most species are adapted to piercing skin and then sucking blood. Apart
from bloodsucking, the females generally also drink assorted fluids rich in
dissolved sugar, such as nectar and honeydew, to obtain the energy they need. For
this, their blood-sucking mouthparts are perfectly adequate. In contrast, male
mosquitoes are not bloodsuckers; they only drink sugary fluids. Accordingly,
their mouthparts do not require the same degree of specialization as those of
females. (Davies et al; 2008)

9. Egg development and blood digestion
Most species of mosquito require a blood meal to begin the process of egg
development. Females with poor larval nutrition may need to ingest sugar or a
preliminary blood meal bring ovarian follicles to their resting stage. Once the
follicles have reached the resting stage, digestion of a sufficiently large blood
meal triggers a hormonal cascade that leads to egg development (Telang et al.,
2006). Upon completion of feeding, the mosquito withdraws her proboscis, and as
the gut fills up, the stomach lining secretes a peritrophic membrane that surrounds
the blood.

10. Distribution
Mosquitoes are cosmopolitan (world-wide): they are in every land region except
Antarctica and a few islands with polar or subpolar climates. Iceland is such an
island, being essentially free of mosquitoes. The absence of mosquitoes from Iceland
and similar regions is probably because of quirks of their climate, which differs in
some respects from mainland regions. At the start of the uninterrupted continental
winter of Greenland and the northern regions of Eurasia and America, the pupa enters
diapause under the ice that covers sufficiently deep water. Ujváry, (2010).
The imago emerges only after the ice breaks in late spring. In Iceland however, the
weather is less predictable. In mid-winter it frequently warms up suddenly, causing
the ice to break, but then to freeze again after a few days.

11. Climate and global distribution
Seasonality
In order for a mosquito to transmit a disease to the host there must be favorable conditions, referred to as
transmission seasonality. Seasonal factors that impact the prevalence of mosquitos and mosquito-borne
diseases are primarily humidity, temperature, and precipitation. A positive correlation between malaria
outbreaks and these climatic variables has been demonstrated in China; and El Niño has been shown to
impact the location and number of outbreaks of mosquito-borne diseases observed in East Africa, Latin
America, Southeast Asia and India.
Climate change impacts each of these seasonal factors and in turn impacts the dispersal of mosquitos
Karungu et al., (2019)
Mosquito-borne diseases
Mosquitoes can act as vectors for many disease-causing viruses and parasites. Infected mosquitoes carry
these organisms from person to person without exhibiting symptoms themselves. Mosquito-borne diseases
include: Viral diseases, such as yellow fever, dengue fever, and chikungunya, transmitted mostly by Aedes
aegypti. Dengue fever is the most common cause of fever in travelers returning from the Caribbean, Central
America, South America, and South Central Asia.
This disease is spread through the bites of infected mosquitoes and cannot be spread person to person.

12. Mosquito Feeding
Blood feeding in mosquitoes follows a species-specific circadian rhythm, which
is mainly nocturnal.
Generally three main categories can be distinguished:
Nocturnal, if feeding occurs at night – many, probably most species belong to
this group, e.g. some Aedes species and Mansonia africana;
Diurnal, if feeding occurs largely during daylight hours, e.g. Aedes
apicoargenteus and Aedes longipalpis; and
Crepuscular, if feeding occurs largely during twilight hours, at dusk or at dawn,
e.g. Aedes africanus and Anopheles gambiae (Goma, 1966 Lazzari, et al., (2019).

13. Feeding habits
The feeding habits include:
Anthropophagic/anthropophilic: mosquitoes biting (preferably) humans
Zoophagic/zoophilic: mosquitoes biting lifestock and other animals
Endophagic: mosquitoes biting mainly inside houses
Endophilic: mosquitoes resting indoors after blood-feeding while the meal is digested
and the eggs mature
Exophagic: mosquitoes biting mainly out of doors
Exophilic: mosquitoes resting outdoors after blood-feeding while the meal is digested
and the eggs mature
Female mosquitoes bite because they need protein found in blood to develop their eggs.
They choose their targets through a combination of smell, heat and visual cues, and
continue seeking blood meals until their abdomens are full. The females can live up to
about a month and feed every two or three nights during that time. The most common
mosquito species feed at dawn and dusk, and for a few hours into dark. However, there
are some species that are particularly aggressive and will feed both day and night
(Baptista et al., 2007)

14. Host spectrum
Mosquitoes obtain their blood meals from a very wide variety of hosts. These
include warm-blooded animals as birds, cattle, pigs, numerous wild animals, and
humans; and cold-blooded animals such as frogs, lizards, snakes, insect nymphs
and pupae. The choice of host varies greatly with species of mosquito and the
availability.
Many species have a marked predilection for one type of host which they select
if reasonable available, taking other hosts only in the absence of their preferred
food (Macdonald, 1957). Other mosquitoes have no particular preferences and
will feed readily on a wide range of hosts.

15. Mosquito control
Mosquito fish Gambusia affinis, a natural mosquito predator
Many measures have been tried for mosquito control , including the elimination
of breeding places, exclusion via window screens and mosquito nets , biological
control with parasites such as fungi and nematodes, or predators such as fish,
Copepods, dragonfly nymphs and adults, and some species of lizard and gecko.
Another approach is to introduce large numbers of sterile males.

16. CONCLUSION
 In summary, the study shows mosquito lifecycle, its habits, breeding sites, the
disease they transmit and its resting behaviour after blood meal.
Attribute such as host spectrum. The study also involves the control of the vector
using the natural means (mosquitofish Gambusia affinis), elimination of breeding
sites and chemical control methods such as use of insect repellent (DEET) and the
use of treated nets.

17. REFERENCES
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18. REFERENCE
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