Lecture 18 Flashcards
What are the key features of arthropods?
- jointed limbs: adaptable limbs for movement and handling objects
- segmented bodies: divided into distinct regions
- exoskeleton made of chitin (molts for growth)L for protection and support
What are some types of arthropods?
- insects
- myriapods
- arachnids
- crustaceans
What are examples of insect vectors?
- mosquitoes
- fleas
- flies
- kissing bugs
- lice
What is the effect of warmer temperatures on arthropod diseases?
- expanded habitats (mosquitoes love warm)
- increased reproduction rates (warm speeds up insect life cycles)
What is the effect of a shift in seasonal pattern on arthropod diseases?
- longer active seasons (extends breeding and biting season)
- migration patterns (introduce new diseases to previously unaffected areas)
What is the effect of increased prevalence on arthropod disease?
- increase in mosquito-borne diseases
- increase in tick-borne diseases
- increase in crop-damaging pests
What is the effect of humidity and precipitation changes on arthropod diseases?
- higher humidity support insect reproduction
- flooding = stagnant water = ideal breeding grounds for mosquitoes
What type of arthropod disease is plague?
bacterial
What causes plague?
yersinia pestis
What transmits plague?
fleas (typically found on rodents)
What are examples of protozoan diseases?
- malaria
- african trypanosomiasis
- chagas disease
What causes malaria?
plasmodium
What transmits malaria?
Anopheles mosquitoes
What is another name for African Trypanosomiasis?
sleeping sickness
What is African Trypanosomiasis caused by?
trypanosoma brucei
What is African Trypanosomiasis transmitted by?
tsetse flies
What is Chagas Disease caused by?
Trypanosoma cruzi
What transmits Chagas Disease?
triatomine bugs (kissing bugs)
What are the 4 species of parasites that cause malaria?
1) plasmodium vivax: mildest and most prevalent
2) plasmodium ovale: benign
3) plasmodium malariae: benign
4) plasmodium falciparum: most deadly
What does plasmodium falciparum affect?
- severe anemia
- blocks capillaries
- affects kidneys, liver, brain
How does malaria spread in the body?
- mosquito bite transmits sporozoite into the bloodstream
- enters liver cells (schizogony) = release of merozoites into the blood
- infects RBCs and undergo schizogony
- ruptures infected RBCs, releasing toxic compounds
- causes paroxysms of chills and fever
- some merozoites develop into gametocytes and taken up by a mosquito
- cycle repeats
Why is it hard to have a vaccine for malaria?
- plasmodium rapidly mutates and evades an immune response
How can you prevent malaria?
- chloroquine (malarone for resistant areas)
- artemisinin
- bed nets
- vaccines
Is malaria hard to diagnose?
yes, without sophisticated equipment
What is the reservoir of Trypanosoma brucei gambiense?
humans
What is the reservoir for trypanosome brucei rhodesiense?
livestock and wild animals
How is African trypanosomiasis transmitted?
animals to humans by tsetse fly
What are the symptoms of African trypanosomiasis?
- few early symptoms
- fever
- headache
- deterioration of CNS
How does African trypanosomiasis spread through the body?
parasites evades antibodies through antigenic variation
How is african trypanosomiasis treated?
eflornithine
- crosses blood-brain barrier
- blocks enzyme needed for parasite
How is african trypanosomiasis prevented?
elimination of tsetse fly vectors
What is another name for Chagas disease?
American Trypanosomiasis
What causes Chagas disease?
Trypanosoma cruzi
- flagellated protozoan
What is the reservoir for Chagas disease?
rodents, opossums, armadillos
What is the vector for Chagas disease?
reduviid bug (kissing bug)
- defecates trypanosomes into the bite wound of humans
What does the chronic form of Chagas disease cause?
- megaesophagus
- megacolon
- death due to heart damage
How can chagas disease be treated?
- it can’t
- trypanosome multiplies intracellularly
What are examples of insect viral diseases?
- yellow fever
- dengue
- west nile virus
- chikungunya fever
- zika virus
- st. louis encephalitis
What is yellow fever caused by? What is the vector?
yellow fever virus
- injected from Aedes aegypti
What are symptoms of yellow fever?
- fever
- chills
- headache
- nausea
- vomiting
- jaundice (liver damage)
What is the treatment for yellow fever?
none
- attenuated vaccine
What is dengue?
milder than yellow fever
- also transmitted by Aedes aegypti
Where are most cases of yellow fever and dengue found?
tropical areas
- Caribbean
What are symptoms of dengue?
asymptomatic
- mild fever
- mild pain
- everything mild
What are symptoms of severe denngue?
- severe bleeding
- organ impairment
What is the reservoir for dengue?
humans
- no animals
How can dengue be prevented and treated?
- no vaccine
- no drug treatment
What is chikunngunya fever caused by?
chikungunya virus
What is the chikungunya fever related to?
western and eastern equine encephalitis
What is chikungunya fever transmitted by?
Aedes albopictus
- AKA asian tiger mosquito
What are symptoms of chikungunya fever?
- high fever
- severe joint pain
- rash
- blisters
- low death rate
Where are most cases of chikungunya fever found?
- 1.7m cases in Caribbean
- first case in western hemisphere in 2013
- locally acquired in Florida and Texas
What are some challenges with fighting vectors for chikungunya fever?
- insecticides don’t work well
- bed nets don’t work because they eat all day
What are some ways to prevent Chikungunya fever?
- water storage covers
- ovitraps
- biological control (mosquito dunks)
How do ticks work as vectors?
attaches to host to feed on blood and transfers pathogens at the same time
What diseases are ticks transmit?
- lyme disease
- rocky mountain spotted fever
- tick-borne encephalitis
What disease can mites transmit?
rickettsial diseases
- scrub typhus
What are examples of bacterial disease arachnids can carry?
- typhus
- rocky mountain spotted fever
- lyme disease
What is typhus caused by? What are their main characteristics?
Rickettsia spp
- obligate intracellular parasites
How do Rickettsia spp work?
- infect endothelial cells of the vascular system
- block and rupture the small blood vessels
What spreads typhus?
arthropod vectors
What is typhus fever? What is it caused by?
- epidemic louseborne typhus
- Rickettsia prowazekii
What is Typhus fever transmitted by?
- body louse: Pediculus humanus corporis
- louse feces are rubbed into the bite wound from the louse
What are symptoms of Typhus fever?
- prolonged fever
- rash of red spots
- subcutaneous hemorrhaging
How is typhus fever treated?
- tetracycline
- chloramphenicol
What is endemic murine typhus caused by?
Rickettsia typhi
What is endemic murine typhus transmitted by?
rat flea: X. cheopiis
What is the common host for endemic murine typhus?
rodents
- murine = mouse
How is endemic murine typhus treated?
same as typhus fever
- tetracycline
- chloramphenicol
What is another name for Rocky Mountain spotted fever?
tickborne typhus
What is rocky mountain spotted fever caused by?
rickettsia rickettsii
What is rocky mountain spotted fever spread by?
- wood ticks (Dermacentor andersoni)
- dog ticks (Dermacentor variabilis)
What are the symptoms of rocky mountain spotted fever?
measles-like rash
- also on palms and soles
How can rocky mountain spotted fever be treated?
same as typhus
- tetracycline
- chloramphenicol
What disease do biting midges transmit?
bluetongue virus
- affects livestock
What is the mechanism for biting midges?
bites transfer virus to animals
- impacts agriculture and ecosystems
What disease do sandflies transmit?
- leishmaniasis
- sandfly fever
What is the mechanism for sandflies?
transfers protozoan parasites or viruses through blood feeding
What is born from biting midges?
arboviral encephalitis
What is EEE and WEE? What is mortality rate?
Eastern/western equine encephalitis
- 30% mortality in humans
What does WEE and EEE cause?
- brain damage
- deafness
- neurological damage
How can EEE and WEE be treated?
it can’t
- no FDA-approved antiviral drugs
What is transmission of St Louis encephalitis?
Culex mosquitoes
What are symptoms of St Louis encephalitis?
mild or asymptomatic
- severe cases = serious neurological disease
Where is St Louis encephalitis prevalent?
central and eastern US
What is California encephalitis transmitted by?
Aedes and Culex mosquitoes
What are symptoms of California encephalitis?
mild and rarely fetal
What is west nile virrus transmitted by?
Culex mosquitoes
How is west nile virus maintained?
bird-mosquito-bird cycle
What are symptoms of west nile virus?
mild (fever, headache) to polio like paralysis and fetal encephalitiis
What crustaceans can be intermediate hosts?
freshwater crustaceans (copepods)
What is schistosomiasis transmitted by?
small flukes called Schistosoma
What is guinea worm disease transmitted by?
larvae of Dracunculus medinensis develop in copepods
- ingested by humans in contaminated water
How does schistosomiasis work through the body?
- feces carrying eggs get into the water supply
- cercariae released from the snail penetrate the skin of humans
- eggs shed by adult schistosomes in the host lodge in tissues (forms granulomas)
What is the intermediate host for Schistosomiasis?
aquatic snails
What is Schistosoma haematobium?
urinary schistosomiasis
What is schistosoma japonicum?
schistosomiasis that causes intestinal inflammation found in Asia
What is schistosoma mansoni?
schistosomiasis that causes intestinal inflammation found in South America
What is the primary treatment of Schistosomiasis? What is the dosage like? How effective?
Praziquantel: kills adult worms by disrupting their structure
- single or split dose based on infection severity
- highly effective: 60-90% cure rate
What are alternative drugs for Schistosomiasis?
- Oxamniquine for praziquantel resistance
- Artemisinin derivatives (currently researching)
How can we provide supportive care for Schistosomiasis?
- symptom management (anti-inflammatory drugs, hydration)
- surgery for severe organ damage
How can we prevent Schistosomiasis?
- mass drug administration (MDA)
- health education: avoid contact with contaminated water, improve sanitation
