Paper XV, XVI and Practical IV�

Dr. Sajjan M.B.,�,�Dept. of Zoology,�Raje Ramrao Mahavidyalaya, Jath

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Syllabus – Paper XVI

Unit I: Dipterans as Disease Vectors 18

1 Dipterans as important insect vectors

• Mosquitoes
• Sand fly
• Houseflies

2 Study of mosquito born diseases –

• Malaria
• Dengue
• Chikungunya
• Viral encephalitis
• Filariasis

3 Control measures of Mosquitoes

4 Study of house fly as important mechanical vector

• Myiasis, Control of house fly

Unit II: Siphonoptera as Disease Vectors 6

1 Fleas a important insect vectors

2 Host-specificity

3 Study of Flea-borne diseases

• Plague
• Typhus fever

4 Control of fleas

Unit III: Histology of mammalian organs 6

Tooth, tongue, Salivary glands, Stomach, Duodenum,

Ileum, Liver, Pancreas, Kidney

Unit I: Dipterans as Disease Vectors�1 Dipterans as important insect vectors

• Mosquitoes
• Sand fly
• Houseflies
• Scope: - Which stage of their life works as a disease vector and how?
• Limitations: - Classification, Morphology, Life cycle is of least concern

Unit I: Dipterans as Disease Vectors�1 Dipterans as important insect vectors

• Introduction
• Diptera is an order of winged insects commonly known as flies.
• Biologically very diverse.
• They occupy every terrestrial niche.
• Many have co-evolved in association with plants and animals.
• There larvae are supplement diet of higher agrarian (agricultural) organisms.
• They are also an important component in food chains.
• The applied significance of the Diptera is as disease vectors, as agricultural pests, as pollinators and as biological control agents.

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Diptera classification

• Diptera fall into three suborders: 
• Nematocera (some are sap feeding insects and/or Sanguivorous)
• Brachycera (most are predators or scavengers)
• Cyclorrhapha (flies that breed in vegetable or animal material – living or dead)

Unit I: Dipterans as Disease Vectors�1 Dipterans as important insect vectors

Morphology & Life cycle of Mosquito

Comparison between Anopheles, Culex and Aedes

Feeding behaviour of Mosquitoes

Biting behaviour of Mosquitoes

• Female mosquitoes feed on animals and humans.
• They are attracted by the body odours, carbon dioxide and heat emitted from the animal or person.
• Some species prefer biting at certain hours.
• Feeding mostly takes place during the night.
• Some species prefer to feed in forests, some outside of houses, and others indoors.
• A blood-fed mosquito looks for a safe resting place that is shaded. E.g. houses, cattle sheds, outdoors - on vegetation, at other natural sites.
• Mosquitoes do not usually bite while eggs are developing.
• Those that bite in the early evening may be more difficult to avoid than species that feed at night.
• Mosquitoes that rest indoors are the easiest to control.

Female anopheles mosquito - vector of Malaria

• When Anopheles females feed on blood meal, they carry malarial pathogen from infected person to normal person during successive feeding.
• Female mosquitoes take blood meals to carry out egg production, and such blood meals are the link between the human and the mosquito hosts in the parasite life cycle.
• The successful development of the malaria parasite in the mosquito (from the "gametocyte" stage to the "sporozoite" stage) depends on several factors.
• The most important is ambient temperature and humidity (higher temperatures accelerate the parasite growth in the mosquito) and whether the Anopheles survives long enough to allow the parasite to complete its cycle in the mosquito host ("sporogony" or "extrinsic" cycle, duration 10 to 18 days).
• Differently from the human host, the mosquito host does not suffer noticeably from the presence of the parasites.

Factors Involved in Malaria Transmission

• Preferred Sources for Blood Meals - One important behavioral factor is the degree to which an Anopheles species prefers to feed on humans (anthropophily) or animals such as cattle (zoophily). Anthropophilic Anopheles is more likely to transmit the malaria parasites from one person to another. Most Anopheles mosquitoes are not exclusively anthropophilic or zoophilic. However, the primary malaria vectors in Africa, A. gambiae and A. funestus, are strongly anthropophilic and, consequently, are two of the most efficient malaria vectors in the world.
• Life Span - Once ingested by a mosquito, malaria parasites must undergo development within the mosquito before they are infectious to humans. The time required by Plasmodium for development in the mosquito (the extrinsic incubation period) ranges from 10 to 18 days, depending on the parasite species and the temperature. If a mosquito does not survive longer than the extrinsic incubation period, then she will not be able to transmit any malaria parasites.
• Patterns of Feeding and Resting - Most Anopheles mosquitoes are crepuscular (active at dusk or dawn) or nocturnal (active at night). Some Anopheles mosquitoes feed indoors (endophagic) while others feed outdoors (exophagic). After blood feeding, some Anopheles mosquitoes prefer to rest indoors (endophilic) while others prefer to rest outdoors (exophilic).

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Mosquito Control

• Elimination of breeding places (Source reduction)
• Standing water
• Containers around Home
• Gutters
• Swampy areas
• Destruction of larvae and pupae
• Oil drip - The thin layer (surface film) of oil on top of the water
• Chemical larvicides - contact poisons, growth regulators, stomach poisons (including bacterial agents). DDT, BHC (According to some workers DDT deeply damages biodiversity; hence its use is banned in many countries.) Methoprene is another larvicide which mimics and interferes with natural growth hormones in mosquito larvae, preventing development.
• Biological control – Direct introduction of parasites, pathogens and predators to target mosquitoes. Eg. Nematodes, copepods, and fishes (Mosquito fish - Gambusia affinis, cyprinids, Tilapia, Dragonfly naids, Some species of lizard and gecko)
• Destruction of Adult Mosquitoes
• Prevention of mosquito bite – bed net, window screens,
• Adulticides - In 1958, the National Malaria Eradication Programme – use of DDT
• Fumigation – The burning of sulpher, pyrethrum, cresol, tar camphor, etc. To control adult mosquitoes in India, van mounted fogging machines and hand fogging machines are used.
• A light trap that attracts and captures mosquitoes – Lethal ovitraps, automatic lethal ovitraps, burning Propane – generates CO₂, warmth & water vapour (this attracts the mosquitoes where they are trapped or killed).

Sandfly (Phlebotomus & Lutzomyia)

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Phlebotomus Lutzomyia

Sandfly (Phlebotomus & Lutzomyia)

• Sand Fly is responsible for spread of disease Leishmaniasis, caused by protozoan parasites belonging to the genus Leishmania
• There are some 500 known phlebotomine species, but only about 30 have been found to transmit Leishmaniasis.
• Only the female sand fly transmits the parasites.
• Over a period of between 4 and 25 days, the parasites develop in the sand fly. When the infectious female sand fly then feeds on a fresh source of blood, it inoculates the person or animal with the parasite, and the transmission cycle is completed.
• Phlebotomine sand flies are found throughout the inter-tropical and temperate regions of the world.
• The main symptoms of Leishmaniasis are Fever, malaise, eye pain, and headache occurring mainly during the warm weather. Acute symptoms last for 2-4 days, but if the fever is severe it takes a week

Morphology & Life cycle of Sandfly (Phlebotomus)

Lutzomyia: Life Cycle

Leishmania (Protozoan): Life cycle

Sand fly Control

• As the breeding-sites of sand flies are generally unknown, control measures that act specifically against immature are not feasible.
• Measures used to control adult sand flies include the use of insecticides (mostly pyrethroids) for residual spraying of dwellings and animal shelters, space-spraying, insecticide-treated nets, and personal protection through application of repellents/insecticides to skin or fabrics.
• No vaccines or drugs to prevent infection are available. The best way to prevent infection is to protect from sand fly bites.
• To decrease the risk of being bitten, avoid outdoor activities, especially from dusk to dawn, when sand flies generally are the most active.
• When outdoors:
• Minimize the amount of exposed (uncovered) skin. Wear long-sleeved shirts, long pants, etc.
• Apply insect repellent to exposed skin. The most effective repellents generally are those that contain the chemical DEET (N,N-diethylmetatoluamide).
• When indoors:
• Stay in well-screened or air-conditioned areas.
• Spray living/sleeping areas with an insecticide to kill insects.
• Use a bed net and tuck it under your mattress. If possible, use a bed net that has been soaked in or sprayed with a pyrethroid-containing insecticide. The same treatment can be applied to screens, curtains, sheets, and clothing (clothing should be retreated after five washings).

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House fly – Musca domestica

• The common housefly is one of the most widely distributed insects and has the ability to transmit disease to people.
• This fly is found throughout the world and is commonly found in homes and restaurants.
• Because of its close association with people and its ability to transmit disease, it is considered a greater threat to human welfare than any other species of non-biting fly.
• They can carry more than 1 million bacteria on their bodies and can transfer these to contaminate surfaces and food.
• The common housefly can transmit the pathogens that cause shigellosis, typhoid fever, E. coli, and cholera.
• The disease-causing agents can either be transmitted by the body hairs or by the tarsi which are transmitted to food or surfaces when the fly lands.
• Additionally, pathogens can be transmitted when a fly regurgitates onto food in order to liquefy material for digestion. 

House fly: - Life Cycle

• Egg – on Animal & vegetable waste (In favourable conditions - hatching 24 hrs.)
• Larva (maggots) - creamy-white color and 1/2 inch long. (4-7 days)
• Pupa - Shell hardens and darkens.
• Adult - mating occurring soon after emergence.

House fly: Mechanical Vector

• Flies can spread diseases because they feed freely on human food and filthy matter alike.
• The fly picks up disease-causing organisms while crawling and feeding.
• Those that stick to the outside surfaces of the fly may survive for only a few hours, but those that are ingested with the food may survive in the fly’s crop or gut for several days.
• Transmission takes place when the fly makes contact with people or their food.
• Most of the diseases can also be contracted more directly through contaminated food, water, air, hands and person-to-person contact.
• This reduces the relative importance of flies as carriers of disease.
• The diseases that flies can transmit include enteric infections (such as dysentery, diarrhoea, typhoid, cholera and certain helminth infections), eye infections (such as trachoma and epidemic conjunctivitis), poliomyelitis and certain skin infections (such as yaws, cutaneous diphtheria, some mycoses and leprosy).

House fly Control

• Exclusion and Sanitation
• Sanitation is the first measure of defense. Even though some various traps and sprays are used to kill flies, it is necessary to eliminate the source to remove them
• Whenever possible, food and materials on which the flies can lay eggs must be removed or destroyed, which will isolate the egg-laying adult. Killing adult flies will reduce infestation, but the elimination of breeding areas is necessary for good House Fly control management.
• Garbage cans and dumpsters should have tight-fitting lids and be cleaned regularly.
• Drainage will often aid control, getting rid of extra moisture.
• Openings of buildings should be tightly screened with screen.

Control Products for House Flies

• Insecticide Residual Concentrates
• Insecticide Dusts
• Pyrethrin Insecticide Aerosols
• Fogging Insecticides and Professional Foggers
• Fly Baits - Outside Use
• Fly Light Traps - Inside Use

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Fly baits & Traps

4 House fly - Myiasis

Myiasis is an infestation of the skin by developing larvae (maggots) of a variety of fly species (myia is Greek for fly) of order Diptera. Worldwide, the most common flies that cause the human infestation are Dermatobia hominis (human botfly) and Cordylobia anthropophaga 

(tumbu fly).

Myiasis - Life Cycle of flies

• The female flies lay their eggs on animal’s damp, protected areas of the body (soaked with urine and feces) mainly buttocks.
• Eggs – hatch in eight hours to a day depending on the conditions.
• The larvae then lacerate the skin with their mouthparts, causing open sores.
• Then larvae tunnel through the sores into the host's subcutaneous tissue, causing deep and irritating lesions highly subject to infection.
• The larvae travel through bloodstream and migrate to skin via spinal canal.
• They moult on the skin and pupae fall on the ground where adult emerges out.
• After about the second day, bacterial infection is likely and, if left untreated, causes bacterial bloodstream infections or sepsis. This leads to anorexia and weakness and is generally fatal if untreated.

Types of Myiasis

• Specific Myiasis - Caused by flies that need a host for larval development
• Examples - Dermatobia hominis (human botfly), Cordylobia anthropophaga (tumbu fly), Oestrus ovis (sheep botfly), Hypoderma spp. (cattle botflies or ox warbles), Gasterophilus spp. (horse botfly), Cochliomyia hominivorax (new world screwworm fly), Chrysomya bezziana (old world screwworm fly), Auchmeromyia senegalensis (Congo floor maggot), Cuterebra spp. (rodent and rabbit botfly)
• Semi specific Myiasis - Caused by flies that usually lay their eggs in decaying animal or vegetable matter, but that can develop in a host if open wounds or sores are present.
• Examples - Lucilia spp. (green-bottle fly), Cochliomyia spp. (screw-worm fly), Phormia spp. (black-bottle fly), Calliphora spp. (blue-bottle fly), Sarcophaga spp. (flesh fly or sarcophagids)
• Accidental Myiasis - It is also called as pseudomyiasis. Caused by flies that has no preference or need to develop in a host but that will do so on rare occasions. Transmission occurs through accidental deposit of eggs on oral or genitourinary openings, or by swallowing eggs or larvae that are on food.
• Examples - Piophila casei (cheese fly), Musca domestica (housefly), Fannia spp. (latrine flies), Eristalis tenax (rat-tailed maggots), Muscina spp.

Myiasis Symptoms

Myiasis – Control Measures

• Prevention: -
• Cattle Hygiene – Washing, crutching of sheep (removal of wool)
• Human Hygiene – Sanitation, personal hygiene, clothes washing by hot water.
• Vector control – insecticide application (Organo-phosphorous, Organo-chlorine), Sterile insect technique (sterilized male),
• Treatment: -
• First the larva must be eliminated through pressure around the lesion and the use of forceps. Secondly the wound must be cleaned and disinfected. Further control is necessary to avoid further reinfestation.
• Livestock may be treated prophylactically with slow release boluses containing Ivermectin which can provide long-term protection against the development of the larvae. Sheep also may be dipped - a process which involves drenching the animals in persistent insecticide to poison the larvae before they develop into a problem.

Unit I - 2 Study of mosquito born diseases

• Malaria
• Dengue
• Chikungunya
• Viral encephalitis
• Filariasis

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2 Study of mosquito born diseases - Malaria

2 Study of mosquito born diseases - Dengue

• Intro
• Dengue fever, commonly known as break bone fever is a flu-like illness caused by the Dengue virus.
• Vector - Aedes mosquito
• This disease is mainly found in the tropical and sub-tropical regions of the world.
• Causes of Dengue
• Dengue is caused due to four viruses, namely - DENV-1, DENV-2, DENV-3, and DENV-4.
• The virus enters a mosquito when it bites an already infected person.
• And the illness is spread when it bites a healthy person, and the virus spreads through the person’s bloodstream.
• Once a person recovers, he is immune to the specific virus and not the other three types.
• The probability of developing severe Dengue fever, also known as Dengue Haemorrhagic Fever, increases if you're infected a second, third or fourth time.

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Dengue virus

• Sphericle
• Single positive-stranded RNA virus of the family Flaviviridae, genus Flavivirus
• 47 strains of dengue virus
• Life Cycle - transmission between humans and Aedes mosquitoes – Vertical transmission from mosquito to mosquito has also been observed in some vector species
• The DENV genome is about 11000 bases of positive-sense, single stranded RNA (ssRNA) that codes for three structural proteins -capsid (C), membrane (M), envelope (E) and seven non-structural protein (NS1, NS2a, NS2b, NS3, NS4a, NS4b, NS5). It also includes short non-coding regions on both the 5' and 3' ends.

Dengue - symptoms

• Symptoms of Dengue - Usually, symptoms of Dengue feel like an uncomplicated fever and not easily identifiable in teens and children. Dengue causes a fever of 104⁰ F along with at least two of these symptoms:
• Headache, Muscle, bone and joint pain
• Nausea, Vomiting
• Pain behind the eyes
• Swollen glands, Rash
• There are three types of fever a person is prone to, namely – Mild Dengue Fever, Dengue Haemorrhagic Fever and Dengue Shock Syndrome.
• Mild Dengue Fever – Symptoms are seen after a week from the bite and include severe or fatal complications.
• Dengue Haemorrhagic Fever – Symptoms are mild but can gradually worsen within a few days.
• Dengue Shock Syndrome – This is a severe form of dengue and can even cause death.

Dengue - Treatment

• There is no specific treatment of Dengue fever or cure as Dengue is a virus. Timely intervention can help, depending on how severe the disease is. Here are a few basic treatments of Dengue fever:
• Medication: Painkillers like Tylenol or Paracetamol are generally prescribed to the patients. IV drips are sometimes supplemented in case of severe dehydration.
• Stay hydrated: This is crucial as most of our bodily fluids are lost during vomiting and high fever. Continuous intake of fluids will make sure that the body does not easily dehydrate.
• Hygiene: Hygiene is of the utmost importance, even more so when you are not well. The patient can opt for a sponge bath if not a regular bath.
• Add a few drops of disinfectant liquid to the water being used for bathing. It is also advisable to sanitize your hand with a hand sanitizer before and after visiting the patient in the hospital. Disinfect the water used to wash the patient’s clothes to rid the clothes of germs.

Dengue - Prevention

• Researchers are still working on finding a specific cure for Dengue fever. Dengue fever treatment involves the use of pain relievers with acetaminophen. Additionally, doctor will recommend to drink plenty of fluids and take rest. The best way is prevention. Following are some actions that can keep safe from the virus:
• Lesser skin exposure: Try wearing long pants and shirts to cover your skin surfaces and reducing the chances of bites. Mosquitoes are highly active early in the morning or evening, so try avoiding venturing out in those times.
• Mosquito Repellent: A repellent with at least 10 per cent concentration of diethyltoluamide (DEET). A higher concentration is needed for longer exposures. You can apply the ointment daily to keep mosquitoes away.
• Personal hygiene: When you are infected with any virus, you are extra sensitive to other illnesses. Use a hand sanitizer which acts to keep germs at bay. The liquid soap will protect you against many illness-causing germs.
• Disinfect stagnant water: The Aedes mosquito breeds in clean and stagnant water. Keep water covered at all times and use a proper disinfectant if necessary. Turn over any vessels which can accumulate water and scrub the surfaces thoroughly so as to reduce the chances of developing a breeding ground for the mosquitoes.

2 Study of mosquito born diseases - Chikungunya

• Caused by chikungunya virus (CHIKV).
• Arthropod-borne virus - genus – Alpha
• Vector – Aedes mosquito
• Symptoms similar to dengue fever, followed by a prolonged arthralgic disease that affects the joints of the extremities. The pain associated with CHIKV infection of the joints persists for weeks or months, or in some cases years.

2 Study of mosquito born diseases - Chikungunya

• Spherical in shape
• Genome is 12000 bases long positive-sensed single-stranded RNA molecule
• Encoding four nonstructural proteins (nsP1–4), & five structural proteins (capsid C & glycoproteins E1, E2, E3, 6K).

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Chikungunya - Symptoms

• Most people infected with Chikungunya virus will develop some symptoms.
• Symptoms usually begin 3–7 days after being bitten by an infected mosquito.
• The most common symptoms are fever and joint pain.
• Other symptoms may include headache, muscle pain, joint swelling, or rash.
• Chikungunya disease does not often result in death, but the symptoms can be severe and disabling.
• Most patients feel better within a week. In some people, the joint pain may persist for months.
• People at risk for more severe disease include newborns infected around the time of birth, older adults (≥65 years), and people with medical conditions such as high blood pressure, diabetes, or heart disease.
• Once a person has been infected, he or she is likely to be protected from future infections.

Chikungunya – Control Measures

• There is no vaccine to prevent or medicine to treat Chikungunya virus.
• Prevention
• Avoid mosquito bite
• Use preventive measures for mosquito bite such as bed net, insecticide, etc.
• Treat the symptoms:
• Get plenty of rest.
• Drink fluids to prevent dehydration.
• Take medicine such as acetaminophen or paracetamol to reduce fever and pain.
• Do not take aspirin and other non-steroidal anti-inflammatory drugs (To reduce the risk of bleeding).
• If you are taking medicine for another medical condition, talk to your healthcare provider before taking additional medication.
• If you have Chikungunya, prevent mosquito bites for the first week of your illness.
• During the first week of infection, Chikungunya virus can be found in the blood and passed from an infected person to a mosquito through mosquito bites.
• An infected mosquito can then spread the virus to other people.

2 Study of mosquito born diseases – Viral Encephalitis

• Encephalitis is inflammation of the brain. There are several causes, but the most common is a viral infection.
• Encephalitis often causes only mild flu-like signs and symptoms - such as a fever or headache - or no symptoms at all.
• Sometimes the flu-like symptoms are more severe.
• Encephalitis can also cause confused thinking, seizures, or problems with movement or with senses such as sight or hearing.
• In some cases, encephalitis can be life-threatening. Timely diagnosis and treatment are important because it's difficult to predict how encephalitis will affect each individual.

Viral Encephalitis - causes

• Common viral causes
• Herpes simplex virus (HSV). Both HSV 1 &  HSV 2 can cause encephalitis. Encephalitis caused by HSV 1 is rare but can result in significant brain damage or death.
• Other herpes viruses. These include the Epstein-Barr virus, which commonly causes infectious mononucleosis, and the varicella-zoster virus, which commonly causes chickenpox and shingles.
• Enteroviruses. These viruses include the poliovirus and the coxsackie virus, which usually cause an illness with flu-like symptoms, eye inflammation and abdominal pain.
• Mosquito-borne viruses. These viruses can cause infections such as West Nile, La Crosse, St. Louis, western equine and eastern equine encephalitis. Symptoms of an infection might appear within a few days to a couple of weeks after exposure to a mosquito-borne virus.
• Tick-borne viruses. The Powassan virus is carried by ticks and causes encephalitis. Symptoms usually appear about a week after a bite from an infected tick.
• Rabies virus. Infection with the rabies virus, which is usually transmitted by a bite from an infected animal, causes a rapid progression to encephalitis once symptoms begin.
• Childhood infections. Common childhood infections - such as measles (rubella), mumps and German measles (rubella) - used to be fairly common causes of secondary encephalitis.

Viral Encephalitis - Types

• There are two main types of encephalitis:
• Primary encephalitis. This condition occurs when a virus or other agent directly infects the brain. The infection may be concentrated in one area or widespread. A primary infection may be a reactivation of a virus that had been inactive after a previous illness.
• Secondary encephalitis. This condition results from a faulty immune system reaction to an infection elsewhere in the body. Instead of attacking only the cells causing the infection, the immune system also mistakenly attacks healthy cells in the brain. Also known as post-infection encephalitis, secondary encephalitis often occurs two to three weeks after the initial infection.

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Viral Encephalitis - Symptoms

• Most people with viral encephalitis have mild flu-like symptoms, such as:
• Headache
• Fever
• Aches in muscles or joints
• Fatigue or weakness
• Sometimes the signs and symptoms are more severe, and might include:
• Confusion, agitation or hallucinations
• Seizures
• Loss of sensation or paralysis in certain areas of the face or body
• Muscle weakness
• Problems with speech or hearing
• Loss of consciousness (including coma)
• In infants and young children, signs and symptoms might also include:
• Bulging in the soft spots (fontanels) of an infant's skull
• Nausea and vomiting
• Body stiffness
• Poor feeding or not waking for a feeding
• Irritability

Viral Encephalitis - Prevention

• The best way to prevent viral encephalitis is to take precautions to avoid exposure to viruses that can cause the disease.
• Practice good hygiene. Wash hands frequently and thoroughly with soap and water, particularly after using the toilet and before and after meals.
• Don't share utensils. Don't share tableware and beverages.
• Teach children good habits. Make sure they practice good hygiene and avoid sharing utensils at home and school.
• Get vaccinations. Keep your own and your children's vaccinations current. Before traveling, talk to your doctor about recommended vaccinations for different destinations.
• Protection against mosquitoes and ticks
• Dress to protect yourself. 
• Apply mosquito repellent. 
• Use insecticide. 
• Avoid mosquitoes.
• Get rid of water sources outside your home. 
• Look for outdoor signs of viral disease. 

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Viral Encephalitis - Treatment

• Consult the Doctor
• Diagnose the cause
• Take medicine accordingly

2 Study of mosquito born diseases - Filariasis

• Filariasis is a parasitic disease caused by an infection with round worms of the Filarioidea type. These are spread by blood-feeding insects such as black flies and mosquitoes. They belong to the group of diseases called helminthiases.
• Types of Filariasis in Human
• Lymphatic filariasis is caused by the worms Wuchereria bancrofti (Elephantiasis), Brugia malayi, and Brugia timori.
• Subcutaneous filariasis is caused by Loa loa (the eye worm), Mansonella streptocerca, and Onchocerca volvulus.
• Serous cavity filariasis is caused by the worms Mansonella perstans and Mansonella ozzardi.

Filariasis Wuchereria bancrofti – Life Cycle

Filariasis Wuchereria bancrofti – Symptoms

• The most spectacular symptom of lymphatic filariasis is Elephantiasis - edema with thickening of the skin and underlying tissues. Elephantiasis results when the parasites lodge in the lymphatic system.
• Elephantiasis affects mainly the lower extremities. However, different species of filarial worms tend to affect different parts of the body;.
• The subcutaneous worms present with rashes, urticarial papules, and arthritis, as well as hyper- and hypo pigmentation macules. 
• Onchocerca volvulus manifests itself in the eyes, causing "river blindness".
• Serous cavity filariasis presents with symptoms similar to subcutaneous filariasis, in addition to abdominal pain, because these worms are also deep-tissue dwellers.

Filariasis Wuchereria bancrofti – Treatment

• The recommended treatment is Albendazole combined with Ivermectin.
• A combination of diethylcarbamazine and Albendazole is also effective.
• Side effects of the drugs include nausea, vomiting, and headaches.
• All of these treatments are microfilaricides; they have no effect on the adult worms. While the drugs are critical for treatment of the individual, proper hygiene is also required.
• There is good evidence that Albendazole alone; or addition of Albendazole to diethylcarbamazine or Ivermectin, makes minimal difference in clearing microfilaria or adult worms from blood circulation.
• Diethylcarbamazine-medicated salt is effective in controlling lymphatic filariasis while maintaining its coverage at 90% in the community for six months.
• Different trials were made to use the known drug at its maximum capacity in absence of new drugs. In a study from India, it was shown that a formulation of Albendazole had better anti-filarial efficacy than Albendazole itself.
• In 2003, the common antibiotic doxycvline was suggested for treating elephantiasis. Filarial parasites have symbiotic bacteria in the genus Wolbachia, which live inside the worm and seem to play a major role in both its reproduction and the development of the disease. This drug has shown signs of inhibiting the reproduction of the bacteria, further inducing sterility.
• Clinical trials in June 2005 reported an eight-week course almost completely eliminated microfilaraemia.

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Unit II: Siphonoptera as Disease Vectors

1 Fleas a important insect vectors

2 Host-specificity

3 Study of Flea-borne diseases

• Plague
• Typhus fever

4 Control of fleas

Siphonoptera

• Siphonoptera includes 2,500 species of small flightless insects that survive as external parasites of mammals and birds.
• They are commonly called as 'fleas' which live by consuming blood from their hosts.

1 Fleas a important insect vectors

• Flea Morphology
• Adult fleas grow to about 3 millimeters long, are usually brown, and have bodies that are "flattened" sideways or narrow, enabling them to move through their host's fur or feathers.
• They lack wings, but have strong claws preventing them from being dislodged, mouthparts adapted for piercing skin and sucking blood, and hind legs extremely well adapted for jumping.
• They are able to leap a distance of some 50 times their body length.
• Flea larvae are worm-like with no limbs; they have chewing mouthparts and feed on organic debris left on their host's skin.
• Fleas as vector
• Fleas are vectors for viral, bacterial and rickettsial diseases of humans and other animals, as well as of protozoan and helminth parasites.
• Bacterial diseases carried by fleas include murine or endemic typhus and bubonic plague.
• Fleas can transmit Rickettsia typhi, Rickettsia felis, Bartonella henselae and the myxomatosis virus.
• They can carry Hymenolepiasis tapeworms and Trypanosome protozoans.
• The chigoe flea or jigger (Tunga penetrans) causes the disease tungiasis, a major public health problem around the world.
• Fleas that specialize as parasites on specific mammals may use other mammals as hosts; thus, humans may be bitten by cat and dog fleas.

Flea – Life Cycle

• Egg The number of eggs laid depends on species, with batch sizes ranging from two to several dozen. The fecundity of fleas varies from around one hundred to several thousand. The eggs take around two days to two weeks to hatch.
• Larva Flea larvae emerge from the eggs to feed on any available organic material such as dead insects, faeces, and vegetable matter. They are blind and avoid sunlight, keeping to dark, humid places such as sand or soil, cracks and crevices, under carpets and in bedding. The entire larval stage lasts between four and 18 days.
• Pupa Larvae pupate and weave silken cocoons after three larval stages. Within the cocoon, the larva molts for a final time and undergoes metamorphosis into the adult form. This can take just four days, but may take much longer under adverse conditions, and there follows a variable-length stage during which the pre-emergent adult awaits a suitable opportunity to emerge.
• Adult Once the flea reaches adulthood, its primary goal is to find blood and then to reproduce. Female fleas can lay 5000 or more eggs over their life, permitting rapid increase in numbers. An adult flea only lives for 2 or 3 months. Without a host to provide a blood meal, a flea's life can be as short as a few days. Optimum temperatures for the flea's life cycle are 21 °C to 30 °C and optimum humidity is 70%.

Fleas: host specificity

• Fleas feed on a wide variety of warm blooded vertebrates including humans, dogs, cats, rabbits, squirrels, ferrets, rats, mice and birds.
• Fleas normally specialize in one host species or group of species, but can often feed but not reproduce on other species. (Ceratophyllus gallinae affects poultry as well as wild birds)
• Avian fleas that exploit a range of hosts only parasitize species with low immune responses.
• In general, host specificity decreases as the size of the host species decreases.
• Another factor is the opportunities available to the flea to change host species; this is smaller in colonially nesting birds, where the flea may never encounter another species, than it is in solitary nesting birds.
• A large, long-lived host provides a stable environment that favours host-specific parasites.
• Although there are species named dog fleas (Ctenocephalides canis Curtis, 1826) and cat fleas (Ctenocephalides felis), they are not strictly species-specific. {Eg. A study in Virginia examined fleas collected from 29 dogs. In total, 244 fleas were identified and all turned out to be cat fleas. In fact, dog fleas haven't been found in Virginia in more than 70 years, so it is very likely that a flea found on a dog is actually a cat flea (Ctenocephalides felis)}.
• One theory of human hairlessness is that the loss of hair helped humans to reduce their burden of fleas and other ectoparasites.

3 Study of Flea-borne diseases - Plague

• Plague is an infectious disease caused by Yersinia pestis bacteria, usually found in small mammals and their fleas. The disease is transmitted between animals via their fleas and, as it is a zoonotic bacterium, it can also transmit from animals to humans.
• Humans can be contaminated by the bite of infected fleas, through direct contact with infected materials, or by inhalation. Plague can be a very severe disease in people, particularly in its septicaemic and pneumonic forms, with a case-fatality ratio of 30% - 100% if left untreated.
• Although plague has been responsible for widespread pandemics throughout history, including the so-called Black Death that caused over 50 million deaths in Europe during the fourteenth century, today it can be easily treated with antibiotics and the use of standard preventative measures.
• Plague is found on all continents except Oceania but most human cases since the 1990s have occurred in Africa. Democratic Republic of Congo, Madagascar and Peru are the three most endemic countries.

Plague Yersinia pestis

• Yersinia pestis (formerly Pasteurella pestis) is a gram negative, non motile, rod shaped, coccobacillus bacterium, without spores.
• It is a facultative anaerobic organism that can infect humans via the Oriental rat flea (Xenopsylla cheopis).
• It causes the disease plague, which takes three main forms: bubonic, septisemic, and pneumatic.
• A complete genomic sequence of strain KIM of Y. pestis is 4,600,755 base pairs long; the chromosome of strain CO92 is 4,653,728 base pairs long.

Plague - Symptoms

• Incubation period of 3–7 days.
• Symptoms include fever, chills, aches, weakness, vomiting and nausea.
• There are 3 main forms of plague.
• Bubonic plague The plague bacillus, Y. pestis, enters at the bite and travels to the nearest lymph node to replicate. The lymph node becomes inflamed, tense and painful, and is called a bubo. With advanced infections, the inflamed lymph nodes can turn into suppurating open sores. Bubonic plague cannot be transmitted from human to human.
• Septicaemic plague – wounds formation on the body
• Pneumonic plague – or lung-based plague – is the most virulent and least common form of plague. Typically, it is caused by spread to the lungs from advanced bubonic plague. However, a person with secondary pneumonic plague may form aerosolized infective droplets and transmit plague to other humans.

Plague – Prevention and Treatment

• Prevention
• Preventive measures include informing people when zoonotic plague is present in their environment and giving advice on how they can protect themselves.
• They should be advised to take precautions against flea bites and not to handle animal carcasses.
• People, especially health workers, should also avoid direct contact with infected tissues such as buboes, or close exposure to patients with pneumonic plague.
• Preventive measures for flea bite.
• Vaccination - Jewish bacteriologist Waldemer Haffkine developed the first plague vaccine in 1897. 
• Treatment
• If diagnosed in time, the various forms of plague are usually highly responsive to antibiotic therapy.
• The antibiotics often used are streptomycine, chloramphenicol and tetracycline.
• Amongst the newer generation of antibiotics, gentamyvin and doxycycline have proven effective.

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3 Study of Flea-borne diseases - Typhus fever

• Typhus, also known as typhus fever, is a group of infectious disease that includes epidemic typhus, scrub typhus, and murine typhus.
• Common symptoms include fever, headache, and a rash. Typically these begin one to two weeks after exposure.
• Epidemic typhus is due to bacteria – Rickettsia prowazekii spread by body lice
• Scrub typhus is due to bacteria – Orientia tsutsugamushi spread by chiggers (Red bugs or berry bugs)
• Murine typhus is due to bacteria – Rickettsia typhi spread by fleas 

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Typhus fever - Rickettsia prowazekii

• Rickettsia prowazekii is a species of gram negative, alpha-proteo bacteria, obligate intracellular parasitic, aerobic bacillus bacteria that is the etiologic agent of epidemic typhus, transmitted in the feces of lice.
• The natural life cycle of the bacterium generally involves a vertebrate and an invertebrate host, usually an arthropod, typically the human body louse.
• A form of R. prowazekii that exists in the feces of arthropods remains stably infective for months.
• R. prowazekii also appears to be the closest free-living relative of mitochondria, based on genome sequencing.

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Typhus fever - Symptoms

• Signs and symptoms begin with sudden onset of fever and other flu-like symptoms about one to two weeks after being infected.
• Five to nine days after the symptoms have started, a rash typically begins on the trunk and spreads to the extremities.
• This rash eventually spreads over most of the body, sparing the face, palms, and soles.
• Signs of meningo-encephalitis begin with the rash and continue into the second or third weeks.
• Other signs of meningo-encephalitis include sensitivity to light (Photophobia), altered mental status (delirium), or coma.
• Untreated cases are often fatal.

Typhus fever – Prevention and Treatment

• No vaccine available.
• Doxycycline & Chloromphenicol

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4 Control of fleas

• The following flea control measures are effective when implemented in combination to kill adult fleas, eggs, larvae, and pupae.
• Indoors
• Vacuuming - use Vacuum cleaner
• Laundering - use hot soapy water to clean surfaces
• On your pet
• Grooming with a flea comb
• Bathing
• Outdoors�Flea habitat reduction
• Biological control - Nematodes feeds on flea larvae
• Flea Control Pesticides
• Methoprene, pyriproxifen, Lufenuron, Nitenpyram, Selemectin, etc.

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Syllabus – Practical IV

A] Aquatic biology

B] Insect Vectors & diseases

Study of different kinds of mouth parts of insects

• Chewing & biting
• Chewing & lapping
• Piercing & sucking
• Sponging
• Siphoning

Study of following insect vectors through permanent slides or photograph

• Insect vector – Mosquito, sandfly & housefly
• Study of mosquito born diseases – Malaria, dengue, Chikungunya, encephalitis, filariasis
• Study of sandfly born diseases – Visceral leishmanians, Cutaneous leishmanians,

Phlebotomus fever

• Study of housefly born diseases – Myiasis
• Study of flea born diseases – Plague, typhus

Histology of Following mammalian organs-

a) Tooth (V.S.) b) Tongue c) Salivary gland d) Stomach e)Duodenum

f) Ileum g) Liver h) Pancreas i) Kidneys

Mouth Parts of Insects

Study of different kinds of mouth parts of insects

Chewing & biting - Cockroach

Chewing & lapping – Honey bee

Piercing & sucking - Mosquito

Sponging – House fly

Siphoning – Butterfly

Chewing & biting - Cockroach

Chewing & lapping – Honey bee

Piercing & sucking - Mosquito

Sponging – House fly

Siphoning – Butterfly

Study of following insect vectors through permanent slides or photograph

Insect vector – Mosquito, sandfly & housefly

Study of mosquito born diseases – Malaria, dengue, Chikungunya, encephalitis, filariasis

Study of sandfly born diseases – Visceral leishmanians, Cutaneous leishmanians,

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Phlebotomus fever

• Study of housefly born diseases – Myiasis
• Study of flea born diseases – Plague, typhus

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Histology of Following mammalian organs

• Tooth (V.S.)
• Tongue
• Salivary gland
• Stomach
• Duodenum
• Ileum
• Liver
• Pancreas
• Kidneys

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