Disease Vectors: Mosquitoes and Houseflies

W.malayi also called as brugia malayi are the important agents of bancroftian and brugian(it is sometimes referred to as Malayan)filariasis. In contrast to many other mosquito-borne infections of medical significance, lymphatic filariae are transmitted by not just one but by several genera of mosquitoes.

 Female mosquito have mouthparts that pierce food items to enable sucking of internal fluids. In female mosquitoes, all mouthparts are elongated. The labium encloses all other mouthparts like a sheath. The labrum forms the main feeding tube, through which blood is sucked. Paired mandibles and maxillae are present, together forming the stylet, which is used to pierce an animal's skin. During piercing, the labium remains outside the food item's skin, folding away from the stylet. Saliva containing anticoagulants, is injected into the food item and blood sucked out, each through different tubes.

The gametocytes are the sexual stages of Plasmodium that develop in human red blood cells. When a mosquito takes a blood meal, it ingests these gametocytes, making them the infective stage of the parasite for the mosquito vector.

Culex causes filariasis, bird malaria. Its body rests parallel to the surface or substratum. Whereas Anopheles causes malaria. The body is slender and rests at an angle to the surface or substratum.
Therefore, the correct answer is option B.

Plague is a bacterial disease caused by Yersinia pestis, which is primarily transmitted to humans and animals through the bites of infected rat fleas, scientifically known as Xenopsylla cheopis.

A malaria control method that targets mosquito larvae and pupae as they mature in standing water could be an important supplementary measure in the fight against the disease. Larval source management (LSM) is a method that targets immature mosquitoes, found in standing water before the females develop into flying adults that are capable of transmitting malaria. This is done by permanently removing standing water, for example by draining or filling land; making temporary changes to mosquito habitats to disrupt breeding, for example by clearing drains to make the water flow; or larviciding by adding chemicals or biological larvicides to standing water to kill larvae.

• Quinine and other cinchona alkaloids including quinidine and cinchonine are effective against malaria.
  
• So, the correct answer is 'Quinine'.

The western mosquitofish (Gambusia affinis) is a species of freshwater fish, also known commonly as simply mosquitofish. Mosquitofish were introduced directly into ecosystems in many parts of the world as a biocontrol to lower mosquito populations, which in turn negatively affected many other species in each distinct bioregion. Based on diet, mosquitofish are classified as larvivorous fish. Their diet consists of zooplankton, small insects and insect larvae, and detritus material. Mosquitofish feed on mosquito larvae at all stages of life. Adult females can consume hundreds of mosquito larvae in one day.

Gametocyte is infective stage for female anopheles mosquito because optimum temperature for growth of gametocyte is present in their body.

The motile zygote formed by fertilization of macro gameteby a micro gameteis called ooKinete. It  occurs in gut of mosquito. 

Mosquitoes cause more human suffering than any other organism. Mosquito acts as a vector for the bacteria and viruses, responsible for the diseases such as malaria, dengue, encephalitis and yellow fever etc. When mosquito bites a human it causes severe skin irritation through an allergic reaction to the mosquito's saliva, this is what causes the red bump and itching.

The causative agent of malaria is Plasmodium vivax and female anopheles act as a vector. 

Malaria is caused by the toxins produced in the human body by malarial parasite Plasmodium. Malarial parasite is carried from the infected to the healthy persons by the female Anopheles mosquito.

Culex is a genus of mosquitoes which carries worms of filariasis, Japanese encephalitis, St. Louis encephalitis, and avian malaria. 
Anopheles is a genus of mosquito first described and named by J. W. Meigen in 1818. About 460 species are recognized, while over 100 can transmit human malaria. Both Culex and Anopheles have three pairs of legs, the last pair is held up in the air while sitting. 

The female Anopheles mosquito, when it withdraws blood the infected malarial patient, the male and female gametes enter into the mosquito gut, when the two male and female gametes fuse together and form a zygote, which develops into ookinetes that burrow into the mosquito midgut wall to develop into oocysts.

Trypanosoma brucei rhodesiense and Trypanosoma brucei gambiense are the two parasites causes sleeping sickness. Tsetse flies which acts as a carrier of the infection. 

There are different ways to prevent mosquito larvae to grow in ponds and rice fields. These can be done by not allowing the water to get stagnant. Also, it can be prevented by inoculating it with Microcystis cyanobacteria. Microcystis aeruginosa causes death of the larvae by producing neurotoxins and hepatotoxins.

Houseflies live for up to 3 weeks and are active during the warmer part of the year. An adult female deposits 50 to 100 eggs at a time and about 500 eggs over her lifetime. The eggs are deposited in rotting organic matter. They hatch after about 12 hours and the larvae, or maggots, feed on the rotting organic material. A maggot passes through three larval stages and then forms a pupa, or cocoon. The adult fly emerges from the cocoon. Houseflies typically develop from egg to adult within 10 days. 

The diseases, which spread from one person to another person or from animal to person are called as communicable diseases. It is also termed as infectious or contagious diseases. Housefly is a major factor in contributing communicable diseases. Housefly comes in contact with waste products and eatables. When it flies from wastes to eatables, it transports bacterial agents from wastes to eatables. Due to consumption of such eatables, the persons infected with microbes of various diseases, person gets sick. 

House flies are the vectors of several infectious agents. The pathogen may attach with flies when they sit on the waste materials. They cause typhoid, cholera, salmonellosis, dysentery, tuberculosis, anthrax, and parasitic worms carried to human food on the fly’s body parts or in its regurgitations or defecations.

Sanitation is the primary method for controlling houseflies because it removes their breeding grounds, such as decaying organic matter and waste.

The housefly undergoes complete metamorphosis, which consists of four stages: egg, larva (maggot), pupa, and adult.

House Flies are generally, found feeding and breeding on trash and rotten food where they get attached to several pathogens which is further transmitted by these flies to a healthy host.  As houseflies and their larvae feed, on dead remains of plants and animals. So, they act as a scavenger.

Effective housefly control requires a combination of measures, including covering food, securing garbage, and screening buildings to prevent access and breeding.

Insecticides are a common chemical measure used to control housefly populations when sanitation alone is insufficient.

Housefly belongs to the largest phylum known as arthropoda which is characterized by joint appendages. The thorax of housefly contains three pairs of legs. The legs have sharp claws and spines which help the fly to cling to objects.

Houseflies belong to a group of flies called filth flies because they get food from breaking down decaying material. Such type of nutrition is called a saprophyte. If there were no saprophytes, then there would be no top soil for plants to grow in. 

Housefly undergoes several phases during metamorphosis. The mature egg turns into a larva which grows to pupa which finally forms an imago. Imago is generally colourless. Its wings are colourless and immobile.

Compound eyes mainly provide the mosaic pattern of vision as they don't have the well-developed brain to analyze the formed image. The image is formed as repeating units known as ommatidia. The head of the housefly bears two compound eyes.

Houseflies are considered mechanical vectors because they carry pathogens on their bodies and legs, transferring them directly to food or surfaces, rather than the pathogen undergoing a developmental cycle within the fly.

• Adult houseflies never have chewing mouthparts. They use saliva to change solids to liquids. Sponge-like mouthparts pick up semi-liquid foods, such as feces and decaying matter.
• Hence Housefly feeds on sugar by Dissolving in saliva and sucking because they do not have chewing mouthparts.
• So, the correct answer is '.Dissolving in saliva and sucking'.

• The female housefly usually mates only once and stores the sperm for later use. She lays batches of about 100 eggs on decaying organic matter such as food waste, carrion, or faeces. These soon hatch into legless white mature larvae, known as maggots.
• This larval stage is further followed by pupa and adult stages.
• Hence Mature larva of Housefly is Maggot.
• So, the correct answer is 'Maggot'.

• The pupal stage occurs only in holometabolic insects i.e those that undergo a complete metamorphosis, going through four life stages; egg, larva, pupa, and imago(adult). For example, Housefly, Beetle, Butterfly, moths, wasps, etc.
• During the time of pupation, that the adult structures of the insect are formed whilst the larval structures are broken down.
• Hence Pupa occurs in the life cycle of Housefly.
• So, the correct answer is 'Housefly',

• The female housefly usually mates only once and stores the sperm for later use. She lays batches of about 100 eggs on decaying organic matter such as food waste, carrion, or feces.
  
• House fly eggs are laid in almost any warm, moist material that will supply suitable food for the larvae. For example, Cow/Horse dung.
• Hence Common House Fly (Musca nebulo) lays eggs on Cow/Horse dung.
• So, the correct answer is 'Cow/Horse dung.

• Metamorphosis is defined as the series of changes that occur during the development of adult from the larva.
• The order of metamorphosis in Housefly is Egg, larva, pupa, and adult.
  
• So, the correct answer is 'Egg, larva, pupa, and adult'.

Houseflies are generally found feeding and breeding on trash and rotten food where they get attached to several pathogens which are further transmitted by these flies to a healthy host. Housefly pupae contain large amounts of protein and are thus especially beneficial to the various birds, reptiles, and insects that prey on them.