Goals/Learning Objectives€¦ · Deer Tick Life Cycle Lyme Disease Lyme Disease II Tick-Vectored...

Slide IndexGoals/Learning ObjectivesLouse-borne diseasesEpidemic TyphusImportance of TyphusTrue Bug-borne Pests and DiseasesChagas' DiseaseChagas' Disease IIChagas' Disease IIIHuman Bot FlyHuman Bot Fly Life CycleTick-Vectored DiseasesTick-Vectored Diseases IIDeer Tick Life CycleLyme DiseaseLyme Disease IITick-Vectored Diseases IIITick-Vectored Diseases IVLeichmaniasisHistory of LeishmanaisisEpidemicsSearch for Causal Agent and VectorDr. LeishmanCultivation of "Leishman Bodies"Biology of the Sandfly VectorHuman ExperimentsHabits of SandfliesHistory of Treatment/ManagementWorldwide Malaria Eradication ProgramAbandonment of Malaria Eradication ProgramTypes of LeishmaniasisKala-AzarDermal LeichmaniasisEspundia - Hindi for "Black Fever"Oriental SoreTreatmentTreatmentsTable of Diseases and

Goals/Learning Objectives

: Goal Develop a biological understanding of the diseases vectored by lice, true bugs, ticks, other flies and how and why these diseases are a problem for humans throughout the world.

Learning Objectives

Name the major diseases vectored by lice, true bugs, ticks, Human bot flies, and sand flies, and identify where they are problems in the world.List the human symptoms associated with each of the lice, tick, true bug, Human Bot Fly and sandfly-vectored diseases.Identify an insect-vectored disease given a description or visual image of the human symptoms.Sketch or outline the disease cycle of typhus.Name several prevention and treatment options for each of the insect-vectored diseases discussed.

Louse-borne diseases

Sucking lice, such as the human body louse, can transmit diseases such as trench fever and epidemic typhus.Infection by Rickettsia organisms lead to high fever for two weeks, aches, bronchial disturbance, stupor, and red rash outbreaks. Fatality rate high under epidemic conditions.

Importance of Typhus

Typhus, as you have already learned, is one of the two most important historical (pre-19th century) diseases vectored by insects.

Major battlesNazi concentration camps in W.W.IITyphus is absolutely deadly to lice

True Bug-borne Pests and Diseases

True bugs (Hemiptera), have piercing-sucking mouthparts.Two families that are pests of man: Cimicidae (bedbugs), and Reduviidae (assassin bugs).Bedbugs bite people, poultry, rats, and rabbits. So alternate hosts.Cause a dermatosis, or rash, and are nocturnal feeders. Rarely disturb their host when they feed.

Chagas' Disease

Most assassin bugs are predators, but some, such as, are vertebrate feeders. They are vectors

of a microscopic flagellated protozoan, , which causes Chagas' Disease Important disease in South America

Triatoma infestansTrypanosoma lewesi

from Binford & Connor (1976)

Chagas' Disease

Transmission cycle similar to typhus, in that when bug eats it defecates. Your inoculate yourself by scratching infected feces into the wound.Trypanosome gets on your hand, and you may eventually touch your eye.

Chagas' Disease

Eye swells, and this is called the Sign of Romana.Two forms of disease:

Acute form affects young children, and kills in 2 to 4 weeks.Chronic form, where nervous system and heart muscle is weakened gradually and person may die of heart attack.

Problem of eradication is that disease also in local rat and opossum populations.

from Harwood & James (1979)

Human Bot Fly

Pests of man include the human bot fly which lives under the skin of humans.

The larvae cause welts in the skin, and eventually the adult will eat its way out. Found in the tropics of Central and South America.

Human Bot Fly Life Cycle

Female glues the egg on bloodsucking fly's leg. Egg drops off fly when feeding on human. Egg hatches and larva will enter skin. No feeling until larva gets completely under the skin. It is itchy and larvae can be felt moving under skin.

Tick-Vectored Diseases

Lyme DiseaseVectored by deer ticks, . Adult ticks feed on deer and humans. Immature larvae feed on the white-footed mouse, where they pick up the disease

Ixodes dammini

Alternate hosts:some micewild dogssome reptiles

Causal Agent: A spirochaete,Borrelia burgdorferi

Slide IndexGoals/Learning ObjectivesLouse-borne diseasesEpidemic TyphusImportance of TyphusTrue Bug-borne Pests and DiseasesChagas' DiseaseChagas' Disease IIChagas' Disease IIIHuman Bot FlyHuman Bot Fly Life CycleTick-Vectored DiseasesTick-Vectored Diseases IIDeer Tick Life CycleLyme DiseaseLyme Disease IITick-Vectored Diseases IIITick-Vectored Diseases IVLeichmaniasisHistory of LeishmanaisisEpidemicsSearch for Causal Agent and VectorDr. LeishmanCultivation of "Leishman Bodies"Biology of the Sandfly VectorHuman ExperimentsHabits of SandfliesHistory of Treatment/ManagementWorldwide Malaria Eradication ProgramAbandonment of Malaria Eradication ProgramTypes of LeishmaniasisKala-AzarDermal LeichmaniasisEspundia - Hindi for "Black Fever"Oriental SoreTreatmentTreatmentsTable of Diseases and Vectors: A Review

Lyme Disease

Symptoms: A few days after bite, circular rash may develop with a clear center (only 40% of time!)Flu-like symptoms such as fatigue, headache, chills, stiffness of jointsStiff neck, swollen glands, conjunctivitusCan ultimately cause chronic arthritis or heart and central nervous system complicationsCan invade brain, can cause neurologic problems (EEG affected)

DetectionElevated antibodies in blood

Lyme Disease

TreatmentAntibiotics (Tetracycline) effective.Usually several weeks of antibiotics.If detected late, Intravenous antibiotics.

Human Granulocytic Ehrlichiosis (HGE):A newly identified disease that is also vectored by the deer tickSymptoms are flu-like, yet more severe than Lyme diseaseAffects the immune system, allowing other diseases to take placeTreatment: Tetracycline

HMESimilar to HGE, transmitted by the Lone Star Tick

Rocky Mountain Spotted Fever:Vectored by the dog tick, Dermacentor variabilisMust be attached for 4 - 6 hr to transmit the diseaseSymptoms:

Flu-like symptoms; large spots around wrists and ankles, then rest of the body several days after the bite High (105-106 F) fever Can kill small children

Treatment:The antibiotic Tetracycline

Leishmaniasis

Vector- a sand fly, , transmits, which is a flagellated microscopic

protozoan

Phebotomus argentipesleichmania donovani

Mode of attack- the microorganism attacks the phagocytes, which are the 'hunter-killer' cells in the immune system. These cells not recognized as parasitized by other cells

History of Leishmanaisis

1875- first protozoan shown to be parasiticRoad building in India helped to disseminate the disease:More travel of infected individualsRoads themselves provided wet breeding sites for sandflies to breedRuts along sides of roads were beneficial for both sandflies and mosquitoes

Epidemics

1875 in Assam, India-25% of population killed over the next 25 years1992 in Somalia, so still an important disease

Search for Causal Agent and Vector

Originally was transmitted by bedbugs, due to abundance of bedbugs in many developing countriesThought illness was caused by hookworm injury-the extreme anemia and eventual death Problems with this hypothesis were that spleens were enlarged in leishmaniasis, not so with hookworm infestation

Dr. Leishman

Dr. Leishman found "leichman bodies", as they were later to be called, in the macrophage cells from the grossly enlarged spleen of a dead British soldierThey were ovoid, spore like bodies not much larger than a bacterium

Cultivation of "Leishman Bodies"

In 1904, Dr. Rogers cultured the Leishman-Donovan bodies into a flagellated protozoan stage These are much larger and correspond to the promastigote stage The organism is a hemoflagellate, similar to the trypanosome that causes sleeping sickness

Biology of the Sandfly Vector

Method of transmission:Sandfly ingests protozoanFemale sandfly feeds on fruit, protozoans would multiply enormously in throat of sandfly Sandfly's throat became clogged, and sandfly would try to dislodge them by ingesting liquidSandfly, which feeds on human blood, bites human, and injects protozoan

Human Experiments

Method of transmission:In the 1940s, Dr. Swaminath used six human volunteers, and allowed raisin (fruit) fed and inoculated sandflies to feed on the volunteers Three of the volunteers became ill with leishmaniasis So, vector proved!

Habits of Sandflies

Like hot & humid climates Feed on cows, people Larvae live on floor of homes and feed on organic matter Adult is a weak flier Dark, humid homes are good places for them-British homes in 1800s versus traditional open homes of local Indian peoples

History of Treatment/Management

No treatment initially, so high death rate, particularly among childrenDDT was a wonder drug-spray on walls of home, and up to six months later any insect landing on walls of home died First large scale trial with DDT was to eradicate Malaria along the Tennessee River in 1945 Nobel Peace Prize to discoverer of DDT, Paul Muller

Worldwide Malaria Eradication Program

Devastated sandflies, and virtually eliminated leichmania as a major disease in several areas of the world for 20 yearsIn some places a single spray would eliminate the sandflies for an entire year

Abandonment of Malaria Eradication Program

Malaria eradication program abandoned in 1960s-it was not working-spraying was expensive, not totally effective due to politics, incompetence, permanent carriers for reinvasion, etc. Also, chloroquinone was discovered-it was cheap and effectiveSandflies came back, and new epidemics occurred in Bangladesh, India, and Nepal

Types of Leishmaniasis

Visceral Leichmaniasis-is Kala Azar, and has reached epidemic proportions Attacks the liver, spleen, bone marrow

Tender spot over liverHigh fever

Severe and eventually deadly anemia

Kala-Azar

Symptoms anemia, enlarged liver & spleen, and susceptibility to other diseases Mortality is in untreated cases (1989 Medical Encyclopedia)

extremely high

Synonym is Dum dum fever Important is Asia, USSR, Africa, and Central America

Dermal Leichmaniasis

Post-Kala Azar Dermal Leichmaniasis-

Leichmania eliminated from deep organs by treatment, but for some reason organism changes form and

. attacks

macrophages in skinResult is a

, with large warts on skin.

leprosy-like condition

Extremely difficult treat. Does not respond well to antimony gluconate.

Espundia - Hindi for "Black Fever"

A , where the pathogen attacks the naso-oral area of the face and the

disfiguring disease

nasal cartilage is destroyedThe nasal area of the face rots away, leaving a .large, gaping holeCausal agent is Leichmania brasilensis

.Important in Central and South America, and Asia.

Oriental Sore

A skin disease caused by another leichmania. Causes skin ulcers

Treatment

Now, low level of resistance in leichmania populations in Asia.Pentamidine, which is much more toxic than antimony gluconate (itself toxic to people), will work. Cost $100.00. Pentamidine used to treat AIDS patients with pneumonia caused by parasite . Pneumocystus carynii

Treatments

20 days of . antimony gluconateCost in 1990 dollars $15.00. This is a great deal of money in several developing countries, which is why deaths occur.

Some people did not use all 20 days-they saved last few days worth because they felt better. Result-resistant leichmania

Table of Diseases and Vectors: A Review

Disease Vector

Malaria (protozoan) Mosquitoes (Anopheles)

Yellow fever (viral) Mosquitoes (Aedes)

Dengue, Hemorrhagic Dengue Mosquitoes

Encephalitides (viral) Mosquitoes

Filiariasis (nematodes) Mosquitoes

Sleeping Sickness (protozoan) Tsetse flies

Leishmaniasis (protozoan) Sandflies

Onchocerciasis (nematode) Blackflies

Plague (bacterial) Fleas

Murine Typhus (rickettsial) Fleas, Lice

Typhus (rickettsial) Lice

Relapsing Fever (bacterial) Lice, Ticks

Chagas' Disease (protozoan) Conenose bugs

Rocky Mountain Spotted Fever Ticks

Lyme Disease (bacterial) Ticks

Study Questions

Study QuestionsWhat kind of microorganism causes typhus and how is it transmitted?How were WWII concentration camp victims treated for typhus at the end of the war?What is one way bedbugs are controlled in Central and South America?How is Chagas' disease transmitted and what is the microorganism responsible for the disease? Briefly describe the disease cycle.What is the problem in eradicating ChagasÕ disease?Outline the Human Bot Fly life cycle.What tick transmits Lyme Disease and what other hosts does it feed on?When is the Deer Tick most active and likely to spread Lyme Disease?Why is Lyme Disease a concern?Distinguish between HGE and Lyme Disease.What tick transmits Rocky Mountain Spotted Fever?What insect transmits leishmaniasis and what microorganism causes the disease?Why were sandflies able to multiply in India during the late 1800s?What did soldiers in Operation Desert Storm do to prevent getting bitten by sandflies?What was one positive thing that happened as a result of the worldwide Malaria Eradication Program?What form of leishmaniasis affected U.S. troops in Somalia in 1992? What are the symptoms of this disease?Explain how Kala-Azar sometimes changes form, what this condition is called and the symptoms.What is Espundia? Describe its symptoms.What are two reasons why control and treatment of leishmaniasis have been a problem.

Goals/Learning Objectives€¦ · Deer Tick Life Cycle Lyme Disease Lyme Disease II Tick-Vectored...

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